WO2015036585A1 - Corps d'enlèvement de roche - Google Patents

Corps d'enlèvement de roche Download PDF

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Publication number
WO2015036585A1
WO2015036585A1 PCT/EP2014/069587 EP2014069587W WO2015036585A1 WO 2015036585 A1 WO2015036585 A1 WO 2015036585A1 EP 2014069587 W EP2014069587 W EP 2014069587W WO 2015036585 A1 WO2015036585 A1 WO 2015036585A1
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WO
WIPO (PCT)
Prior art keywords
volume
pcd material
pcd
substrate
rock
Prior art date
Application number
PCT/EP2014/069587
Other languages
English (en)
Inventor
Geoffrey Davies
Moosa ADIA
Rufus NEETHLING
Original Assignee
Element Six Abrasives S.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Element Six Abrasives S.A. filed Critical Element Six Abrasives S.A.
Priority to US15/021,828 priority Critical patent/US20160230473A1/en
Priority to CN201480061793.6A priority patent/CN105723047A/zh
Publication of WO2015036585A1 publication Critical patent/WO2015036585A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C26/00—Alloys containing diamond or cubic or wurtzitic boron nitride, fullerenes or carbon nanotubes
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B10/00—Drill bits
    • E21B10/46—Drill bits characterised by wear resisting parts, e.g. diamond inserts
    • E21B10/58—Chisel-type inserts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
    • B22F7/06—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite workpieces or articles from parts, e.g. to form tipped tools
    • B22F7/062—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite workpieces or articles from parts, e.g. to form tipped tools involving the connection or repairing of preformed parts
    • B22F7/064—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite workpieces or articles from parts, e.g. to form tipped tools involving the connection or repairing of preformed parts using an intermediate powder layer
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
    • C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
    • C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
    • C22C29/08—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds based on tungsten carbide
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B10/00—Drill bits
    • E21B10/46—Drill bits characterised by wear resisting parts, e.g. diamond inserts
    • E21B10/50—Drill bits characterised by wear resisting parts, e.g. diamond inserts the bit being of roller type
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B10/00—Drill bits
    • E21B10/46—Drill bits characterised by wear resisting parts, e.g. diamond inserts
    • E21B10/54—Drill bits characterised by wear resisting parts, e.g. diamond inserts the bit being of the rotary drag type, e.g. fork-type bits
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B10/00—Drill bits
    • E21B10/46—Drill bits characterised by wear resisting parts, e.g. diamond inserts
    • E21B10/56—Button-type inserts
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B10/00—Drill bits
    • E21B10/46—Drill bits characterised by wear resisting parts, e.g. diamond inserts
    • E21B10/56—Button-type inserts
    • E21B10/567—Button-type inserts with preformed cutting elements mounted on a distinct support, e.g. polycrystalline inserts
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B10/00—Drill bits
    • E21B10/46—Drill bits characterised by wear resisting parts, e.g. diamond inserts
    • E21B10/56—Button-type inserts
    • E21B10/567—Button-type inserts with preformed cutting elements mounted on a distinct support, e.g. polycrystalline inserts
    • E21B10/573—Button-type inserts with preformed cutting elements mounted on a distinct support, e.g. polycrystalline inserts characterised by support details, e.g. the substrate construction or the interface between the substrate and the cutting element
    • E21B10/5735—Interface between the substrate and the cutting element
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B10/00—Drill bits
    • E21B10/60—Drill bits characterised by conduits or nozzles for drilling fluids
    • E21B10/602—Drill bits characterised by conduits or nozzles for drilling fluids the bit being a rotary drag type bit with blades
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
    • B22F2005/001—Cutting tools, earth boring or grinding tool other than table ware

Definitions

  • This disclosure relates to a rock removal body for a drag bit rock drilling application and a rock removal body for a roller cone bit rock drilling application
  • Polycrystalline diamond materials typically comprise an intergrown network of diamond grains with an interpenetrating metallic network.
  • the network of diamond grains is formed by sintering of diamond powders facilitated by molten metal catalyst/solvent for carbon at elevated pressures and temperatures.
  • the diamond powders may have a monomodal size distribution whereby there is a single maximum in the particle number or mass size distribution, which leads to a monomodal grain size distribution in the diamond network.
  • the diamond powders may have a multimodal size distribution where there are two or more maxima in the particle number or mass size distribution, which leads to a multimodal grain size distribution in the diamond network.
  • Typical pressures used in this process are in the range of around 4 to 7 GPa but higher pressures up to 10 GPa or more are also practically accessible and may be used.
  • the temperatures employed are above the melting point at such pressures of the metals.
  • the metallic network is the result of the molten metal freezing on return to normal room conditions and will inevitably be a high carbon content alloy.
  • any molten metal solvent for carbon which can enable diamond crystallization at such conditions may be employed.
  • the transition metals of the periodic table and their alloys may be included in such metals.
  • the predominant custom and practice is to use the binder metal of hard metal substrates caused to infiltrate into a mass of diamond powder, after melting of such binders at the elevated temperature and pressure.
  • This is infiltration of molten metal at the macroscopic scale of the conventional PCD construction, i.e., infiltrating at the scale of millimetres.
  • the commonest conventional situation is the use of tungsten carbide, with cobalt metal binders, as the sintered hard metal substrate. This inevitably results in the sintered hard metal substrate being bonded in-situ to the resultant PCD.
  • Successful commercial exploitation of PCD materials to date has been very heavily dominated by such custom and practice.
  • PCD constructs which use sintered hard metal substrates as a source of the molten metal sintering agent via directional infiltration and the bonding in-situ to that substrate, are referred to as "conventional PCD" constructions or bodies.
  • PCD structures comprising PCD material bonded and attached to carbide hard metal substrates are used for material removal elements attached and arranged in housing bodies.
  • General applications where the material to be removed is rock include drill bits for oil well and mining purposes and the like.
  • PCD structures may also find application in, for example, as road planing and building construction where the material to be removed may be considered as synthetic or re-constituted rock-like materials such as asphalt, rock chipping containing asphalt, concrete, brick and the like, including combinations of such.
  • rock will be considered to refer to both natural geological rocks and synthetic or re-constituted rock-like materials.
  • FIG 1 is a schematic diagram of a typical conventional drag bit, 101 , and housing body, 102.
  • the diagram shows conventional PCD rock removal elements 103, 104, and 105 in different radial positions in the housing body, consisting of right circular cylinders comprising relatively thin layers of PCD material bonded and attached to much larger carbide hard metal cylindrical substrates.
  • On rotation of the drill bit such elements are caused to continuously bear on the rock and operate by a predominantly shearing action, where the rock is progressively fractured and fragmented.
  • Figure 2 schematically shows one edge of a conventional PCD rock cutting element, 201 , continuously shearing rock, 202.
  • FIG 3 is a schematic diagram of a typical roller cone drill bit, 301 , consisting of a housing body, 302, and three roller cone structures, 303, which are able to freely rotate on bearings.
  • Each roller cone, 303 rotates around the surface of the rock as the overall drill bit housing body, 302, is rotated.
  • the rock removal elements or bodies, 304 are inserted and attached to the surface of each of the three cone structures. As the cone structures turn, they bring the rock removing elements sequentially to bear on the rock surface.
  • the roller cone structures are attached to the housing body via shaft and bearing structures which are in turn protected by gage pad surfaces, 305, with abrasion resistant gage elements, 306. Water cooling and crushed rock removal is facilitated by nozzles, 307.
  • rock removing elements, 304 have typically rounded ends such as general chisel shapes, or domed and/or conical surfaces which bear upon the rock surface.
  • rock removal elements typically have a relatively thin PCD material layer bonded with the shaped hard metal substrate, and remove rock by a predominantly crushing action.
  • Figure 4 schematically shows a cross-section of a dome shaped conventional PCD rock crushing element, 401 , consisting of a thin layer of PCD material, 402, forming a shell bonded to a dome shaped hard metal body, 403, bearing and crushing rock, 404.
  • roller cone designs are highly optimized and established. These too, therefore, are not lightly and conveniently altered.
  • PCD rock removal elements be they intended for drag bit or roller cone bits, have been restricted to relatively thin layers of PCD material (typically from 1 to about 2.5mm and rarely up to about 4mm) formed attached to typically one side of large, substantially cylindrical hard metal substrates in the same high pressure high temperature processes.
  • the required metal for the partial re-crystallisation and sintering of the diamond particles leading to the inter-grown polycrystalline diamond grains is predominantly derived from and infiltrated from the hard metal substrates.
  • the long range infiltration of the required metal necessary for PCD layers between 2.5 and 4mm progressively contributes to difficulties of producing well sintered diamond grains.
  • the dominant life limiting mechanism for conventional PCD rock removal elements or bodies involves crack propagation in the PCD body which extends to the free surfaces of the PCD material resulting in extremely damaging chipping and spalling behaviour. It is believed that a governing aspect for such crack propagation is the residual stress distribution in the PCD rock removal element or body which results from the differential thermal contraction of the PCD layer compared to the hard metal substrate material during the return-to-room pressure and temperature of the manufacturing process. Due to the conventional rock removal element or body designs involving the PCD layers being attached to one side of the hard metal substrates, the return-to-room pressure and temperature in the manufacturing process causes bending distortion to occur in the PCD layers, necessarily resulting in the residual stress distribution spanning the PCD layers involving substantial and significant tensile stress components. These tensile stress components govern the direction of crack propagation. Their particular magnitude, gradients and directional residual stress distributions for specific designs and arrangements for PCD layers and substrates distinguishes the poorest and the best designs.
  • PCD bodies comprising a thin layer of PCD material attached during manufacturing processes to substantial hard metal substrates also are restricted in both PCD layer thickness and composition of the PCD material itself.
  • PCD layer thicknesses made conventionally are typically less than 2.5mm, though exceptionally up to 4mm. These thicker PCD layers are very difficult to make and progressively suffer from inferior structure and properties arising from poor diamond-to-diamond bonding as a consequence of impurity segregation and general difficulties of long range infiltration of the catalyst/solvent metals for sintering of the diamond particles.
  • the compositional restrictions of the conventional PCD layers concern a dependence of the overall metal content of the PCD material to the diamond grain size distribution.
  • the metallurgy of conventional PCD materials is restricted to the metallurgies which are suitable for diamond particle recrystallization and sintering, and of viable hard metal materials, if such materials are exploited as substrate materials.
  • the dominant metal in this regard is cobalt with, to a far lesser extent, certain nickel and/or iron alloy variations of cobalt.
  • a rock removal body for a drag bit rock drilling application comprising a polycrystalline diamond (PCD) material volume bonded to a cemented hard metal substrate along an interface; wherein:
  • the body has an overall body volume, and is of a right circular cylindrical shape having a circumferential edge, and a barrel portion, the PCD material volume being axially asymmetrically disposed at one end of the body;
  • the PCD material volume has a thickness from the circumferential edge axially along the surface of the barrel portion of around 3mm or greater and a functional working volume, the functional working volume being the volume of PCD material progressively worn away in use during useful life of the rock removal body to a form a final wear surface, the functional working volume having a maximum extent such that the final wear surface does not intersect the interface of the PCD material volume and the substrate;
  • the interface bonding the polycrystalline diamond material volume to the cemented hard metal substrate comprising a layer of a third material derived from a refractory material, the third material being a metal diffusion blocking barrier material to molten bonding material of the substrate and molten catalyst solvent sintering aid of the PCD material volume during formation of the rock removal body;
  • the PCD material volume comprising a plurality of inter-bonded diamond grains having an average diamond grain size forming a diamond network and a metallic component forming a metallic network
  • the substrate comprising a cementing metal, the metallic component and the cementing metal being independent of one another, independently derived, have not interacted during the high pressure high temperature manufacturing process, are measurably distinguishable and are pre-selected to be different with respect to their alloy composition
  • the PCD material at least encompasses the functional working volume and is homogeneous in that the PCD material is spatially constant and invariant with respect to diamond network to metallic network volume ratio, wherein the homogeneity is measured at a scale greater than ten times the average diamond grain size, the maximum diamond grain size in the diamond network being less than three times the average diamond grain size.
  • a rock removal body for a roller cone bit rock drilling application comprising a polycrystalline diamond (PCD) material volume bonded to a cemented hard metal substrate along an interface; wherein:
  • the body comprises a right circular cylinder portion having an associated radius, one end of the cylinder portion forming a generally convex curved surface or surfaces with an apex, or one end forming a general chisel shape where two or more flat surfaces meet to form an apex, the PCD material volume being axially asymmetrically disposed extending from and abutting the apex, the cemented hard metal substrate being disposed at the opposite end of the cylinder;
  • the PCD material volume has a thickness from the apex in the axial direction of the cylinder portion of the body to the interface with the substrate equal to or greater than the radius of the cylinder portion of the body, the PCD material volume further comprising a functional working volume, the functional working volume being the volume of PCD material progressively worn away in use during useful life of the rock removal body to a form a final wear surface, the functional working volume having a maximum extent such that the maximum extent of the functional working volume is less than the thickness of the PCD material volume thickness; the functional working volume extending from the apex in the axial direction;
  • the interface bonding the PCD material volume to the substrate comprising a thin layer of a third material derived from a refractory material, the third material being a metal diffusion blocking barrier material to molten bonding material of the substrate and molten catalyst solvent sintering aid of the PCD material volume during formation of the rock removal body;
  • the PCD material volume comprising a plurality of inter-bonded diamond grains having an average diamond grain size forming a diamond network and a metallic component forming a metallic network
  • the substrate comprising a cementing metal, the metallic component and the cementing metal being independent of one another, independently derived, have not interacted during the high pressure high temperature manufacturing process, are measurably distinguishable and are pre-selected to be different with respect to their alloy composition
  • the PCD material at least encompasses the functional working volume and is homogeneous in that the PCD material is spatially constant and invariant with respect to diamond network to metallic network volume ratio, wherein the homogeneity is measured at a scale greater than ten times the average diamond grain size, the maximum diamond grain size in the diamond network being less than three times the average diamond grain size.
  • Figure 1 is a schematic diagram of a conventional drag bit and housing body
  • Figure 2 is a schematic side view of one edge of a conventional PCD rock cutting element continuously shearing rock;
  • Figure 3 is a schematic diagram of a typical roller cone drill bit consisting of a housing body and three roller cone structures;
  • Figure 4 is a cross-section of a dome shaped conventional PCD rock crushing element consisting of a thin layer of PCD material bearing on and crushing rock;
  • Figure 5 is a graph of the cobalt content of conventional PCD material plotted against the average grain size of well-established conventional PCD materials
  • Figure 6 is a schematic cross-section of a right cylindrical rock removal body intended for use in drag bit rock drilling wherein the dotted line indicates the final position of a wear scar formed during rock drilling application at end of life of the rock removal element or body;
  • Figures 7a, 7b and 7c are half cross-sectional schematic diagrams of examples giving the main characteristics of the residual stress distribution in a PCD material volume thickness of 2, 5 and 8mm, respectively;
  • Figures 8a, 8b and 8c are schematic cross-sectional diagrams which illustrate a generally convex curved surface or surfaces which can take a hemispheroidal form, either a prolate hemispheroidal, oblate hemispheroidal or a hemispherical form, respectively;
  • Figure 9a is a schematic cross-sectional diagram of an example curved surface which takes the form of a cone with a rounded apex, and Figure 9b shows an example of a general chisel shape which forms an apex;
  • Figures 10a, 10b, 10c and 10d are axial cross-sections of an example rock removal body for use in a conventional roller cone bit design, showing the zones of principal residual stress distinguished by grey shading where the thickness of the PCD material layer are 2, 8, 10 and 16mm, respectively;
  • Figures 1 1 a and 1 1 b indicate the positions of the dominant principal tensile residual stress maxima in the PCD material volume and the cemented hard metal substrate where Figure 1 1a represents examples for drag bit applications and Figure 1 1 b represents the examples for roller cone bit applications;
  • Figure 12 shows an example of a PCD rock removal body intended for drag bit applications, where the PCD material volume comprises two or more layers of differing PCD material and a half cross- section of the body is shown where the principal residual stress distribution is presented by a series of grey shaded volumes which are delineated by contour lines of equal stress;
  • Figure 13 is a set of examples comprising one homogeneous PCD material and the cemented hard metal substrate comprising two layers of differing material and illustrates the residual stress benefits of employing discrete layers of differing cemented hard metal carbide materials; and Figure 14 shows the residual stress benefits when the two layered arrangement of differing PCD materials of Figure 12 are combined with the two layer arrangement of differing tungsten carbide cobalt hard metal of Figure 13.
  • the rock removal bodies of examples described herein may comprise a right circular cylindrical overall shape with a PCD material volume 601 axially asymmetrically disposed at one end of the cylindrical body, with a right cylindrical cemented hard metal carbide substrate 602 disposed at the opposite end.
  • the cemented hard metal substrate 602 ensures that the standard custom and practice of braze technologies developed for drag bit manufacture may be applied in substantively unaltered form.
  • there should be sufficient cemented hard metal substrate free surface area to provide adequate bond strength to the braze layer or engagement this consideration implies a chosen minimum size of substrate for each design of the examples described herein.
  • FIG. 6 is a schematic cross section of a right cylindrical rock removal body intended for use in drag bit rock drilling.
  • a layer of PCD material 601 is separated from a cemented hard metal substrate, 602, by a thin layer of material, 603, which is extant from the use of a barrier layer material used to separate the PCD material volume and the cemented hard metal substrate during manufacture.
  • the dotted line 604 indicates the final position of a wear scar formed during rock drilling application at end of life of the rock removal element or body.
  • a part of the circumferential edge, 605, indicates the part of the composite rock removal body which first is made to bear on the rock strata.
  • the volume of material 606 between the circumferential edge 605 and the dotted line 604 is the volume of PCD material which is progressively worn away during use and will subsequently be referred to as the functional working volume.
  • the remainder of the volume of the composite body outside 606 will subsequently be referred to as the functional support volume.
  • the functional support volume is extant at end of life of the body and comprises the part of PCD material volume 601 left after end of life together with the barrier layer 603 and hard metal substrate 602.
  • the thicknesses of the PCD material layer, 601 , and the barrier layer material, 603, and the length of hard metal substrate, 602, are designated by 607, 608 and 609, respectively.
  • the interfacial thin layer of material 603 separating and bonding the PCD material volume 601 and the substrate 602 may form a planar interface or a non- planar curved surface.
  • Planar in this context means that the interface between the PCD bonding boundary layer and the cemented hard metal substrate is substantially flat and substantially parallel to the base of the cylindrical rock removal body, that being the cemented hard metal substrate.
  • the interfacial layer 603 alternatively may not be flat but may be made up of a curved surface or surfaces usually arcuate in regard to the flat end of the cylindrical body. This will be referred to as non-planar interfaces.
  • the outer free surface of the cemented hard metal substrate 602 is in the form of a right circular cylinder.
  • the layer of PCD material 601 will be a cylindrical layer when the interfacial thin layer of material 601 is planar.
  • the presence of a cemented hard metal substrate 602 bonded in an axially asymmetric manner to the PCD material volume 601 during the high pressure high temperature manufacture of the PCD material volume causes residual stress distributions in both the PCD and cemented hard metal material volumes.
  • the residual stress distributions are due to bending effects caused by differential expansion and contraction of the PCD and cemented hard metal material volumes during the return- to-room temperature and pressure at the end of the high pressure high temperature manufacturing process. These differential dilations are a result of the elastic modulus and thermal expansion properties of the PCD and cemented hard metal carbides being significantly different.
  • the residual stress distribution in PCD, hard metal composite rock removal elements, in particular the tensile residual components in the PCD material volume, are the dominant aspects which may determine the useful life of such rock removal bodies. This is understood to be due to the fact that, typically, crack related failures such as chipping and spalling are the dominant life limiting considerations.
  • the required metal for the liquid phase sintering of the PCD particulate network of the PCD material volumes is derived from long range infiltration of molten cementing metals of the carbide substrate
  • the residual stress distribution in the PCD material volume is of particular highly significance in this regard.
  • the long range infiltration of the required metal into the PCD volume results in the restriction of the general thickness of the PCD material volume to typically less than 3mm.
  • the metal required for the PCD material may be independently derived and isolated from the cementing metal of the hard metal substrate.
  • PCD material volumes of any general simple shape, up to dimensions limited by the high pressure high temperature apparatus available, may be made by providing the necessary metal for the PCD material from a starting mass of particulate diamond intimately and homogeneously combined with metallic particles.
  • the metallic component of the PCD material volume and the cementing metal of the hard metal substrate are independent of one another, independently derived and have not interacted during the high pressure high temperature process.
  • the metal components of the PCD material volume and the hard metal substrate are measurably different and pre-selected to be different in their elemental composition.
  • the molten binder metal of the hard metal substrate may be precluded from infiltrating into the polycrystalline diamond volume of the composite and an example of a means of achieving this separation and isolation of the metallurgy of the PCD volume and the hard metal substrate volume is to provide a barrier layer 603 between the said volumes which is capable of preventing significant cross contamination of the molten metals of the substrate and PCD material volumes.
  • Barrier layers which may operate in this way may comprise materials which have significantly higher melting points than the catalyst/solvent metals for the PCD material and also the binder metal of the hard metal substrate.
  • such metals may alloy and react slowly with the molten catalyst/solvent metals for the PCD materials and the molten binder metal for the hard metal substrate.
  • metals which may satisfy these behaviours may comprise the refractory metals including tantalum, vanadium, niobium, molybdenum, zirconium and their alloys.
  • Ceramic materials such as nitrides, borides and carbides may also fulfil the required criteria.
  • Some examples of such ceramics are tantalum nitride, titanium nitride, aluminium nitride, silicon nitride and mixed nitrides.
  • a 50 to 500 micro meter thick continuous zirconium metal barrier layer or bonding layer may be used.
  • the barrier layer may comprise a 50 micro meter thick tantalum metal or zirconium metal layer.
  • a thin layer of nitrides/borides and/or carbides of the elements of groups IVa ,Va and/or Via of the periodic table and B, Si and Al including, for example, TaN, TiB 2 , ZrB 2 , AIN, Si 3 N 4 , AIB 2 and ZrN, refractory metals, solids solutions, e.g., (Ti, AI)N and mixtures of these, may be used and may be applied using physical vapour deposition (PVD) or chemical vapour deposition (CVD) techniques.
  • the barrier layer between the PCD volume and hard metal substrate may comprise a continuous titanium nitride (TiN) layer, greater than around 3 micro meters in thickness. These thin barrier layers may have particular utility when the interface geometry between the PCD layer and substrate has a non-planar geometry.
  • examples may comprise an interface bonding the polycrystalline material volume to the cemented hard metal substrate, which is comprised of a thin layer of a third material derived from a refractory material which acts as a metal diffusion blocking barrier material to the molten cementing material of the hard metal substrate and the molten catalyst sintering aid of the polycrystalline diamond material during the high pressure high temperature process.
  • the metallic component of the PCD material volume and the cementing metal of the hard metal substrate are independent of one another as a result of being prevented from interacting with one another during the high pressure high temperature process due to the presence of the barrier material layer.
  • This independence of the metallurgy of the PCD material volume and the cementing metal of the hard metal substrate may assist in allowing each of these metallic components to be independently preselected in regard to particular desired composition and properties for each of the PCD material volume and hard metal substrate.
  • This is in contrast to much of the conventional prior art PCD where the metal of the PCD material volume is wholly or in part derived from the cementing metal of the hard metal substrate.
  • it may be desired to exploit a corrosion resistant grade of tungsten carbide hard metal based upon the cementing metal. This corrosion resistance is often and typically achieved by alloying the cobalt cementing metal with elements such as nickel and chromium, or completely replacing it with a more corrosion resistant alloy.
  • alloying agents may well not be ideal or desired components of the metal of the PCD material volume.
  • elements such as chromium and other stable carbide forming metals will always and necessarily form precipitated carbides in metal network of the PCD material volume.
  • precipitated carbides may well undesirably alter the properties of the PCD material volume.
  • some examples described herein may allow for the exploitation of a greatly expanded range of substrate materials without suffering from such potentially undesired metallurgies of the PCD material volume.
  • a further example may well be the use of titanium carbide cemented with nickel hard metal material for the substrates while exploiting well established simple cobalt PCD material volume metallurgy.
  • greatly expanded material design capabilities may be achievable in comparison with the conventional prior art where the metallurgies of the PCD material volume and the cemented hard metal substrate are co-dependent.
  • the metallic component of the PCD material volume and the cementing metal of the hard metal substrate are independent of one another, are independently derived, have not interacted during the high pressure high temperature process, are measurably distinguishable and are pre-selected to be different with respect to the alloy composition.
  • the metallic component of the PCD material volume may be a high carbon content alloy of transition metals which may be able to act as catalyst/solvent for diamond recrystallization from solution. These include, for example, transition metals such as cobalt, nickel, iron, manganese and their alloys.
  • High carbon content cobalt may be a catalyst/solvent for the formation of the PCD network.
  • the cementing metal of the hard metal substrate will have acted as a liquid phase for the sintering of the carbide hard material.
  • Such cementing metals will therefore tend to be alloys containing the hard metal carbide and the metallic element or elements of the carbide in solid solution.
  • Typical of such cementing metals is, for example, cobalt with tungsten in solid solution for tungsten carbide cobalt based hard metal or nickel with titanium in solid solution for titanium carbide nickel based hard metal.
  • the metal component of the PCD material volume and the cementing metal of the hard metal substrate are dominated and substantially the same metallic element, such as cobalt, they will be measurably distinguishable in such examples.
  • the former will be a high carbon cobalt alloy as compared to a cobalt tungsten alloy for the latter.
  • the metallic component of the PCD material volume and the cementing metal of the hard metal substrate of some examples may be preselected to be different with respect to their alloy composition.
  • the metal component of the PCD material volume may be shown to be different in alloy composition using standard analytical techniques known in the art. These techniques include Energy Dispersive Analysis (EDS) on a Scanning Electron Microscope, X-Ray Diffraction and Wet Chemical Analysis.
  • EDS Energy Dispersive Analysis
  • the conventional prior art rock removal element designs have their lives primarily determined by chipping and spalling macroscopic crack related phenomena. Examples described herein may assist in providing a means by which the desirable normal wear dominated behaviour may be approached.
  • the residual stress distribution of any given example will be of primary consideration. More specifically, some examples are created which are characterised by lowering tensile stress maxima, displacing these maxima from the environs of the functional working volume and the reduction of tensile stress gradients in and close to the functional working volume. In this way the probability of macroscopic crack propagation in use may be reduced.
  • the commonest conventional rock removal elements are all generally right circular cylinders with the PCD material volume dimension at the barrel being typically around 2.5mm and rarely and exceptionally around 3 to 4mm.
  • the diameter and length are usually selected according to the specifications given in the Table 1 below.
  • the examples described may be directed at any of the standard configurations.
  • the 1616 configuration will be used to exemplify various features, which may be applied to all of the configurations in Table 1.
  • the PCD material volume may be made to any predetermined dimensions. In the context of the 1616 example, where also a flat planar interfacial boundary is specified, the PCD material volume therefore may be chosen to be of any thickness within the constraints of the overall length.
  • Figures 7a, 7b and 7c are half cross-sectional schematic diagrams giving the main characteristics of the residual stress distribution for a 1616 configuration and comparing a PCD material volume thickness of 2, 5 and 8mm, respectively.
  • the stress distribution provided gives information of the principle residual stress and thus no information is provided at any given position of the direction of the stress.
  • the residual stress distribution information was generated using an ABACUS Finite Element Analysis (FEA) computer package well known in the art and general engineering practice.
  • FEA ABACUS Finite Element Analysis
  • the properties of the PCD material and the cemented hard metal material used for the analysis were as follows.
  • the elastic modulus of the PCD material and the cemented hard metal material used in the analysis were 1020 GPa and 550 GPa, respectively.
  • the linear coefficients of thermal expansion of the PCD material and the cemented carbide material used in the analysis were 4.01 ppm°K ⁇ 1 and 5.5 ppm°K ⁇ 1 , respectively.
  • the line 701 represents the planar interfacial boundary thin layer of third material derived from the refractory barrier material.
  • the dotted line 702 represents the position of the final wear scar surface, i.e., the final extent of the functional working volume at end of life.
  • the material progressively worn away during use extends from the line 702 to a position on the circumferential edge of the PCD material volume, 703, which indicates the point of first contact of the rock removal element or cutter at commencement of use.
  • the dimension of the functional working volume at end of life is chosen to be around 3mm vertically down the barrel of the cylindrical surface.
  • the angle 704 the final wear scar 702 makes with respect to the vertical of the cylindrical barrel is dependent upon the chosen rake angle in relation to the rock surface. This angle is chosen to be 20° for the purpose of this analysis and is typical of what is used in practice. This means that the extent of the functional working volume at end of life radially from 703, along the top flat surface, will be about 1.1 mm.
  • the lines labelled 705 represent principle tensile iso-stress contour lines in the cemented carbide substrate. Between this line and the base and barrel free surfaces of the substrate, the volume is occupied by a principle tensile stress field of very low magnitude. Between 705 and the line representing the barrier layer 701 , in the direction of the barrier 701 , there is a principal tensile stress field increasing in magnitude with an increase in stress gradient becoming more and more intense as the barrier layer is approached.
  • the line 706 represents an intermediate principal iso-stress contour line.
  • the dotted line 707 indicates the position of the maximum principal tensile stress in the substrate material immediately below the barrier layer 701 .
  • the line 708 in the PCD material volume represents the zero stress contour line which separates the hatched volume of PCD material which is in compression from a general tensile field occupying the remainder of the PCD material volume.
  • Two positions of principal tensile stress maxima are indicated by 709 and 710, respectively.
  • the principal stress tensile maximum 709 occupies a position at the circumferential barrel surface of the PCD material volume slightly above the barrier layer 701. This principal stress tensile maximum 709 is dominated by an axial tensile stress.
  • the principal stress tensile maximum 710 occupies a position on the flat top free surface of the PCD material volume. This principal stress tensile maximum, 710, is dominated by a radial tensile stress.
  • Figure 7b illustrates an example where the PCD material volume thickness is 5mm.
  • the functional working volume is invariant with respect to position and scale.
  • the final wear scar position 702 does not cross the boundary 701 and thus does not extend into the cemented hard metal substrate.
  • the functional working volume in example of Figure 7b does not encompass the tensile stress maximum 710 and occupies a volume therefore of greatly reduced residual stresses and gradients.
  • Such examples may be more favourable in that the probability of macroscopic crack propagation to free surfaces leading to chipping and spalling may now be significantly reduced.
  • a distinguishing factor between the example of Figure 7b and the PCD construction of Figure 7a is the crossing and interaction of the final wear scar 702 with the barrier boundary layer 701 .
  • examples where the final wear scar position 702 does not cross and interact with the boundary layer 701 may be favoured.
  • the functional working volume is considered to be invariant in the use of these drag bit examples, such that the extension of the final wear scar 702 down the circumferential barrel surface of the cylindrical cutter is about 3mm, so examples where the thickness of the PCD material volume from its circumferential edge axially along the curved barrel of the cylinder is 3mm or greater are a feature of some of the examples described herein.
  • Table 2 gives the estimated values of the average principal tensile stress gradients, 71 1 and 712. It may be seen that these estimates indicate that, as the PCD material volume thickness increases from 2 to 8mm, the tensile stress gradient 71 1 is progressively reduced by an order of magnitude and that the tensile stress gradient 712 is progressively reduced by about a factor of 4. This analysis, therefore, indicates that a less damaging tensile residual stress distribution in the functional working volume may progressively develop as the PCD material volume thickness increases from around 3mm.
  • This maximum principal tensile stress, 707, is dominated by primarily tensile stress in the hoop direction, i.e., along the circumferential direction. Cracks that form and extend into this region will then tend to split the hard metal substrate diametrically. This was indeed observed for situations where the PCD material layer was large in comparison with the cemented hard metal substrate.
  • the inventors have found that the occurrence of diametrical splitting of the hard metal substrate may be greatly reduced when the volume of the PCD material is less than 50 per cent of the overall rock removal body volume, i.e., when the ratio of the PCD material volume thickness to the cemented hard metal substrate length or thickness measured from the circumferential edge of the body along the curved barrel surface of the cylinder is less than 1.0.
  • the PCD material volume is a cylindrical layer with thickness 3mm or greater and the combined thickness of the boundary layer and the cemented hard metal substrate is 8mm or greater, the interfaces between the PCD material volume boundary and cemented hard metal substrate being flat, planar and parallel to the base of the PCD rock removal body.
  • the thickness of the PCD material volume layer is between 3mm and 8mm for these constructions.
  • the PCD material volume is a cylindrical layer with thickness 3mm or greater and the combined thickness of the bonding boundary layer and the cemented hard metal substrate is 8mm or greater, the bonding interface between the PCD material volume and the cemented hard metal substrate being flat, planar and parallel to the base of the cylindrical rock removal body.
  • the resulting PCD material exhibits a very high degree of homogeneity in that the diamond network to metallic network volume ratio is spatially constant and invariant at and above a scale directly related to the diamond grain size.
  • This may be achieved by generating a starting particulate mass of diamond particles homogeneously mixed with an accurately determined amount of metal particles such that the metal is always smaller than the diamond particle sizes.
  • the methods may involve suspending the diamond particles in a liquid and nucleating and growing precursor compound(s) for the required metals on the surfaces of the diamond particles. The precursor compound(s) are then conveniently converted to pure metals attached to the diamond surfaces by heat treatment in reducing furnace environment.
  • the homogeneity obtainable in the resulting PCD material by such methods may be demonstrated and measured at a scale greater than ten times the average diamond grain size.
  • a further constraint on the diamond grain size distribution in the context of such homogeneous materials is that the maximum grain size be less than three times the average diamond grain size.
  • Such homogeneous PCD materials may have best utility if they at least encompass the functional working volume. Homogeneity in this regard may allow the avoidance of local stress inducing inhomogeneity- based defect structures to occur. In turn this may allow the full exploitation of the residual stress minimizing aspects.
  • the PCD material in some of the examples that at least encompasses the functional working volume is homogeneous in that it is spatially constant and invariant with respect to diamond network and metallic network volume ratio, wherein the homogeneity is measured at a scale greater than ten times the average grain size, the maximum diamond grain size being less than three times the average diamond grain size.
  • the residual stress related criteria applied to the examples may allow the probability of macroscopic crack related behaviour, such as chipping and spalling, to be so reduced that they become of secondary consideration.
  • the primary consideration for the performance of such examples intended for drag bit applications may now be considered to be normal wear behaviour during the rock removal application. PCD material compositions and structures which exhibit improved wear resistance may then be favourably exploited.
  • the diamond grain size distribution and the metal content are independently pre-selected. Fine grained PCD material less than ten micro meters average grain size with a metal content between five and nine volume per cent may be utilized to assist in exploiting high wear resistant behaviour of the PCD material in the functional working volume.
  • the rock removal bodies of the examples intended for roller cone bit applications may comprise a body comprising a right circular cylinder body with one end extending to an apex, with the PCD material volume being axially asymmetrically disposed extending from or abutting the apex, the cemented hard metal substrate being disposed at the opposite cylindrical end.
  • the apex may be formed by a generally convex curved surface or surfaces.
  • the apex may be formed by a general chisel shape where two or more flat surfaces meet to form the apex.
  • the generally convex curved surface or surfaces may take a hemispheroidal form, for example, either a prolate hemispheroidal, oblate hemispheroidal or a hemispherical form, respectively.
  • Figures 8a, 8b, 8c are schematic cross-sectional diagrams which illustrate such examples, respectively.
  • the PCD material volumes, cemented hard metal substrates with a thin layer of bonding material are labelled 801 , 802 and 803, respectively.
  • the PCD material volume 801 extends from and abuts the apex 804.
  • the interfacial bonding material layer 803 separating the PCD material 801 and the cemented hard metal substrate intersects the free surface of the body in the cylindrical barrel surface below the shoulder 805, this being defined as the line of departure of the barrel cylindrical surface extending into the generally convex curved surface.
  • the generally curved surface or surfaces may take the form of a cone with a rounded apex where the radius of the rounded apex is about a quarter to a half of the radius of the cylindrical part of the body.
  • FIG. 9a where the PCD material volume, cemented hard metal substrate with a thin layer of bonding material are labelled 901 , 902 and 903, respectively.
  • the PCD material volume, 901 extends from the rounded apex 904.
  • Figure 9b shows an example having a general chisel shape which forms an apex.
  • the PCD material volume and cemented hard metal substrate with a thin layer of bonding material are labelled 901 , 902 and 903, respectively.
  • the illustrated chisel shape comprises a conical surface, 905, with a rounded apex, 904, modified by two symmetrical flat inclined surfaces, 906, which meet at an apex, 904.
  • the interfacial bonding material layer, 803 and 903 is a thin layer of material which is extant from the use of a barrier layer material used to separate the PCD material volume, 801 and 901 , and the cemented hard metal substrate, 802 and 902, during manufacture.
  • the barrier layer material assists in isolating the molten cementing metal of the hard metal substrate from the molten catalyst/solvent metal of the PCD material volume during the high pressure high temperature manufacturing process.
  • the cemented hard metal substrate assists in enabling the standard custom and practice of braze technologies developed for roller cone bit manufacture to be applied in substantively unaltered form. Moreover, a chosen minimum size of substrate for each design of the examples may assist in enabling there to be sufficient cemented hard metal substrate free surface area to provide adequate bond strength to the braze layer for engagement.
  • Prior art rock removal elements utilizing PCD for roller cone bit applications conventionally exploit a thin layer of PCD material, typically 1.0 to 2.0 mm thick, forming a shell at a convexly curved surface or surfaces. This is illustrated in Figure 4.
  • the examples described herein are not restricted to thin layers of PCD material and may exploit PCD material volumes which may occupy large volumes adjacent to and abutting the apices of convexly curved surface or surfaces, conical surfaces or general chisel surfaces.
  • the dotted lines 806 and 908 indicate the final position of a wear scar formed during rock drilling application at end of life of the rock removal element or body.
  • the apices, 804 and 904, of the PCD material volumes, 801 and 901 indicate the part of the rock removal body which is first made to bear on the rock strata.
  • the volumes of PCD material 807 and 909 between 804 and 904 and the dotted lines 806 and 908, respectively, are the volumes of PCD material which are progressively worn away during use in the rock removal application. These volumes, 807 and 909, will subsequently be referred to as the functional working volumes.
  • the remainder of the volume of the composite bodies outside the volumes 807 and 909, respectively, will subsequently be referred to as the functional support volumes.
  • the functional support volumes are extant at end of life of the body and comprise the part of PCD material volumes, 801 and 901 , left after end of life together with the interfacial layers, 803 and 903, and the cemented hard metal substrates, 802 and 902.
  • the thicknesses of the PCD material volumes, 801 and 901 is defined as the distance from the apices 804 and 904 in the axial direction along the axis of the body to the interfacial bonding barrier layer, 803 and 903, respectively.
  • the thin interfacial bonding layers, 803 and 903 may be flat and parallel to the circular cylindrical end of the substrates as illustrated.
  • the thin interfacial layers 803 and 903 may be generally arcuately curved in regard to the flat end free surface of the substrate. The arcuate nature may be convex in regard to this free surface of the substrate.
  • some examples may comprise an interface bonding the PCD material volume to the cemented hard metal substrate comprising a layer of third material, for example a thin layer, derived from a refractory material which acts as a metal diffusion blocking barrier material to the molten bonding material of the hard metal substrate and the molten catalyst solvent sintering aid of the PCD material during the high pressure high temperature manufacturing process.
  • a layer of third material for example a thin layer, derived from a refractory material which acts as a metal diffusion blocking barrier material to the molten bonding material of the hard metal substrate and the molten catalyst solvent sintering aid of the PCD material during the high pressure high temperature manufacturing process.
  • Rock removal elements in roller cone bit applications operate by predominantly a crushing action by indentation on the rock surface. In such applications, therefore, it is necessary that the rock removal elements bearing on the rock have high compressive strength.
  • Typical roller cone bit designs employ conical rollers with protruding rock removal elements inserted into the surface of the rollers. During drilling, the conical rollers roll around the surface of the rock so that the apices of the rock removing elements are cyclically brought to the bear on the rock surface. This cyclical rotary action, therefore, always involves a degree of impact loading to which the rock removal elements are exposed close to and at the apices of these bodies. Cemented hard metal rock removal elements have been traditionally used in this application in that they have adequate strength and impact resistance properties for such crushing actions particularly for soft rock formations.
  • Cemented hard metal rock removal elements however are somewhat inadequate in respect to their wear resistance properties in such applications and suffer from often unfortunate excessive wear which can limit their usefulness.
  • the systems of the prior art conventionally comprise a relatively thin PCD layer at the apices of cemented hard metal rock removal elements in an attempt to mitigate such wear resistance inadequacies by providing greatly improved wear resistance at the apices.
  • these limited thicknesses of PCD material up to about 1 mm
  • the present applicants have appreciated that such stresses are a consequence of bending effects resulting from the differential shrinkage of PCD layers or volumes bonded to cemented hard metal substrates during manufacture.
  • the thin PCD layers of the conventional structures usually involve functional grading to deal with local high interfacial stresses.
  • This conventional prior art may thus be viewed as using PCD to provide an enhanced wear resistance to the roller cone bullet which would still be dominated by the compressive properties of the carbide.
  • some examples described herein exploit the superior compressive strength of PCD over carbide by using large PCD material volumes and therefore may assist in enhancing the wear resistance of the PCD.
  • the substantial volumes of PCD material may occupy at least the functional working volume.
  • the PCD material volume may provide the required strength and impact resistance for the crushing action of the rock removal element.
  • the general bulk mechanical properties of homogeneous, well-sintered PCD materials may be far superior to general cemented hard metal materials for these purposes.
  • the hardness of PCD materials may be, in some examples, be two to five times greater than typical cobalt cemented tungsten carbide hard metals typically used in roller cone bit drilling applications.
  • the mechanical wear resistance of the PCD of some of the examples may be greatly superior to such cemented hard metals, and the measured compressive strength of PCD material grades (greater than 6700 MPa) may be greater than those obtained for most cobalt cemented tungsten carbide hard metals (eg in the range 3500 to 5500 MPa).
  • the fracture toughness of the PCD materials of some of the examples may be in the range 9 to 10.5 MPa.m "0 5 , which is high for such a hard material.
  • the PCD material volume in some examples must be sufficiently large, and avoid thin layers such as those exploited in the typical prior art PCD.
  • large pieces of PCD material which have an increase of cross- sectional area at right angles to the direction of the applied forces during the crushing action may benefit from the concept of massive support as taught by P W Bridgman 2 .
  • Some of the examples described herein for roller cone drilling applications have this geometry as the PCD material volumes extend from an apex and have a general convex nature. These examples, may therefore enjoy the benefits of the high rigidity of PCD materials providing massive support to their apices when they are bearing upon and crushing the rock. The very high rigidity of such PCD materials may be superior to those exhibited by general cemented hard metals in these applications.
  • the thickness of the PCD material volume from the apex in the axial direction of the cylindrical part of the body to the interface with the cemented hard metal substrate is equal to or greater than the radius of the right circular cylindrical body.
  • the maximum extent of the functional working volume extending from the apex in the axial direction may be less than the PCD material volume thickness. This assists in achieving a minimum thickness of PCD material volume, and for a minimum volume of PCD material relative to the overall rock removal body volume.
  • the examples described may comprise a cemented hard metal substrate.
  • a cemented hard metal substrate To assist in enabling relatively large bulk pieces of PCD material to be made bonded to cemented hard metal substrates during manufacture, it may be advantageous for the molten cementing metal of the hard metal substrate to be prevented from interacting with the molten catalyst/solvent metal/s necessary for the sintering of the PCD material volume.
  • refractory metal layers or certain ceramic layers may be used as metal diffusion blocking barriers during the manufacture of PCD material bonded to cemented hard metal substrates.
  • the interface bonding the PCD volume to the cemented hard metal substrate may comprise, for example, a thin layer of a third material derived from the refractory material which acted as a metal diffusion blocking barrier material to the molten bonding material of the hard metal substrate and the molten catalyst sintering aid of the PCD material during the high pressure high temperature manufacturing process.
  • the metallic component of the PCD material volume and the cementing metal of the hard metal substrate may be independent of one another, may be independently derived, have not interacted during the high pressure high temperature process, may be measurably distinguishable and may be pre-selected to be different with respect to the alloy composition.
  • the resulting PCD material exhibits a very high degree of homogeneity in that the diamond network to metallic network volume ratio is spatially constant and invariant at and above a scale directly related to the diamond grain size.
  • a starting particulate mass of diamond particles is generated which is homogeneously mixed with an accurately determined amount of metal particles such that the metal is always smaller than the diamond particle sizes.
  • the methods may involve suspending the diamond particles in a liquid and nucleating and growing precursor compound(s) for the required metals on the surfaces of the diamond particles. The precursor compound(s) is/are then conveniently converted to pure metals attached to the diamond surfaces by heat treatment in reducing furnace environment.
  • the homogeneity obtainable in the resulting PCD material by such methods may be demonstrated and measured at a scale greater than ten times the average diamond grain size.
  • a further constraint on the diamond grain size distribution in the context of such homogeneous materials is that the maximum grain size is preferably less than around three times the average diamond grain size.
  • Such homogeneous PCD materials may have improved utility if they at least encompass the functional working volume. Homogeneity in this regard may allow the avoidance of local stress inducing inhomogeneity-based defect structures to occur. In turn this may allow for the full exploitation of the residual stress minimizing aspects as described above.
  • the PCD material of some examples material at least encompass the functional working volume, and is homogeneous in that it is spatially constant and invariant with respect to diamond network and metallic network volume ratio, wherein the homogeneity is measured at a scale greater than ten times the average grain size, the maximum diamond grain size being less than around three times the average diamond grain size.
  • FIG 4 shows a generally example of a rock removal element utilizing a conventional prior art thin layer (about 1 mm) of PCD material extending from an apex.
  • a benefit can accrue from the very high wear resistance of PCD materials over cemented hard metals, serious potentially life limiting delamination, and chipping and spalling, of the PCD layer often occurs.
  • the source of such macroscopic crack phenomena may be primarily associated with high magnitude tensile residual stress distributions in the PCD material thin layers and in the cemented hard metal substrate closely associated with the bonding interface between the PCD material and the cemented hard metal.
  • the residual stress distribution in the functional working volume extending from the apex of the rock removal element is of primary consideration and must be managed to mitigate macroscopic crack behaviour such as chipping and spalling.
  • the methods of forming one or more examples which allow large volumes of PCD material to be made bonded to hard metal substrates may be of great benefit in this regard.
  • Figure 8c is an illustration of this, whereby the generally convex curved surface of the PCD material volume is hemispherical.
  • Figures 10a to d are a series of examples based upon Figure 8c where the residual stress distribution in the PCD material volumes, and the cemented hard metal substrates are presented, resulting from of a Finite Element Analysis (FEA).
  • FEA Finite Element Analysis
  • Such FEA techniques are well established in the art and provide semi-quantitative and qualitative information indicating compressive and tensile stress fields, the positions of stress maxima and meaningful comparisons of stress gradients in the stress fields.
  • the examples of Figures 10a to d are for bodies with cylindrical diameter of 16mm and overall length from the apices along the axis to the base of 27mm. These dimensions were chosen as examples for use in conventional roller cone bit designs and custom and practice.
  • the conclusions drawn from the FEA analysis for the examples of Figures 10a-d are believed to be applicable, for example, to the variations of dimensions and shape of the examples indicated in Figures 8a-c and 9a&b.
  • Figures 10a, 10b, 10c and 10d are axial cross-sections of rock removal body examples showing the zones of principal residual stress magnitude, distinguished by grey shading. The boundaries between the different shaded zones may be interpreted as equi-stress contour lines.
  • the thickness of the PCD material layer expressed as the distance from the apices 1001 along the axes to the interface of the PCD material to the boundary layer on the axes 1002, are 2, 8, 10 and 16mm for Figures 10a, 10b, 10c and 10d, respectively.
  • the line 1003 represents the thin interfacial bonding barrier material separating the PCD material volume above the line from the cemented hard metal substrate below the line.
  • This interfacial bonding barrier material is represented by a single line, 1003, in these diagrams due to being very thin; the boundary layer material does not significantly alter the residual stress information presented.
  • the zones or volumes of overall compression are indicated by cross-hatching. Outside these indicated compressive zones various levels of principal tensile stress are indicated by different shades of grey.
  • the tensile stress magnitude increases with the tensile stress maximum being just below the interfacial line 1003 and indicated by the position 1004.
  • the functional working volumes in these embodiments are considered to be invariant, of constant thickness, extending from the apices 1001 to the dotted line 1005.
  • the interfacial bonding barrier line 1003 and the boundary of the functional working volume, 1005, coincide.
  • the functional working volume and the PCD material volume are one and the same.
  • the thickness of the functional working volume, from 1001 along the axis to the dotted line 1005, has been chosen to be 2mm.
  • the most critical tensile residual stress aspects are the high tensile maxima at or close to the free surface of rock removal bodies. In the examples represented by Figures 10a-d, these are indicated by 1004 and 1006, respectively.
  • 1006 represents a tensile maximum in the PCD material volume above the boundary line 1003 at or close to the free surface of the PCD material volume.
  • the tensile stress maximum 1006 in the PCD material volume is dominated by an axial tensile stress.
  • the maximum stress 1006 has an axial and a radial component.
  • the tensile stress maximum 1004 immediately below the interfacial boundary 1003 in the cemented hard metal substrate is dominated by a combination of hoop radial tensile stresses.
  • the shoulder position 1007 coincides with the intersection of the interfacial boundary line 1003 with the free surface of the body.
  • both the critical tensile stress positions 1004 and 1006 rapidly move away from the position of the invariant functional working volume. As these critical points move away from the functional working volume the probability of delamination, chipping and spalling progressively becomes reduced.
  • both critical stress positions 1004 and 1006 may be considered to be sufficiently remote from the invariant functional working volume that the probability of delamination, chipping and spalling of the functional volume becomes insignificant.
  • these examples have the interfacial bonding material separating the PCD material volume and the cemented hard metal substrate intersecting the free surface of the body in the cylindrical barrel surface below the shoulder, this being defined as the line of departure of the barrel cylindrical surface extending into the generally curve surface of the PCD material volume.
  • the hemispheroidal form of the generally convex curved surface of the PCD material volume may be prolate hemispheroidal, oblate hemispheroidal or hemispherical, as depicted in Figures 8a, 8b and 8c, respectively.
  • Figures 10c and 10d show the principal residual stress distribution where the interfacial bonding material layer, 1003, intersects the free surface of the body at the cylindrical barrel surface below the shoulder, 1007.
  • the PCD material thickness, from the apex, 1001 , along the axis 1002, i.e., to the interfacial bonding line, 1003, increases from 10mm to 16mm for Figure 10c to Figure 10d, respectively.
  • the positions of the critical high tensile stress maxima 1004 and 1006 now progressively move to positions even further remote from the functional working volume, i.e., the volume of PCD between the dotted line 1005 and the apex 1001. This is considered to be progressively more and more advantageous.
  • the tensile residual stress in the functional working volume becomes progressively lower from Figure 10c to Figure 10d. Also note that at Figure 10d the tensile residual stress in the functional working volume approaches zero.
  • the gradient of tensile stress across the functional working volume for this range of examples may be very low, for example less than around 10 MPa/mm, which may be considered to be negligible.
  • the volume of PCD material changes from being less than the volume of the hard metal substrate to being greater than the volume of the hard metal substrate.
  • the examples represented by Figure 10d may have a more favourable general residual stress distribution for some applications, such as for rock removal bodies intended for roller cone bit applications, as the volume of the PCD material volume is greater than the cemented hard metal substrate.
  • all the examples described preferably have sufficient surface area of hard metal substrate to enable sufficient engagement and bonding to the roller bit housing bodies or conical rollers. Creating the length of the cylindrical hard metal substrate to be greater than the radius of the cylindrical cemented hard metal substrate may assist in achieving this.
  • the PCD material volume is greater in volume than the cemented hard metal substrate, the increased volume of PCD material adds strength to the overall body by virtue of increased massive support to the apex bearing on the rock strata.
  • Such examples may be expected to have lowered probabilities of chipping, spalling and delamination. Moreover, since residual stress related premature failure phenomena in and close to the functional working volume are relegated to secondary considerations, such examples may allow the exploitation of the exceptional properties of PCD materials (with average diamond grain sizes in the range 1 to 30 micro meters) in regard to the loading situation typical of the roller cone bit applications, where the rock is predominantly removed by a crushing action. These properties are predominantly a combination of the high stiffness of PCD materials exhibited by property measurements such as modulus of elasticity at about a 1000 GPa, transverse rupture strength greater than 1200 MPa and adequate impact resistance exhibited by fracture toughness measurements (K
  • C fracture toughness measurements
  • the PCD material in the examples intended for roller cone bit applications thus may have an average grain size in the range 1 to 30 micro meters, be homogeneous with well intergrown diamond structure such the transverse rupture strength is greater than 1200 MPa as measured in three point bend tests.
  • PCD materials with the highest compressive strength may be favoured.
  • PCD material types with higher diamond content, with good intergrowth may be favoured.
  • one or more of the examples may have a refractory metal diffusion blocking barrier of material may assist in preventing the molten cementing metal of the hard metal substrate and the molten catalyst/solvent metal of the PCD material volume from interacting with one another during the manufacturing process at high pressure high temperature.
  • such materials may also provide bonding between the PCD material volume and the cemented hard metal substrate.
  • Typical materials which can serve such purposes may be, for example, thin (eg around 20 to around 100 micro meters thickness) refractory metal layers chosen, for example, from any combination of one or more of tantalum, vanadium, molybdenum, zirconium, tungsten and alloys thereof.
  • these layers of refractory metals may be chosen such that they do not melt but will be subject to exposure to high carbon content molten transition metals such as molten cobalt- carbon alloy. Thus, these transition metals become partially carburised during the process.
  • the refractory bonding interfacial layer separating the PCD material volume and the cemented hard metal substrate may be, for example, a CVD or PVD deposited continuous ceramic layer of greater than, for example, around 3 micro meters thickness, chosen for example, from any combination of nitrides of the elements of Group IVa, Va or Via of the periodic table, such as titanium nitride, TiN.
  • Some of the examples may enjoy the benefits of the tensile residual stress distribution in and around the functional working volume being radically reduced in magnitude and intensity of gradient.
  • the principal tensile residual stress maxima may be significantly removed from and remote from the functional working volume and its environs. This may provide for a beneficial, significantly lowered possibility or probability of chipping and spalling in and close to the functional working volume.
  • the common feature which may assist in providing this is if the PCD material volumes are large and are comparable in volume to the cemented hard metal substrate or indeed are greater in volume than the cemented hard metal substrate. The latter being the case for rock removal bodies intended for roller cone bit applications.
  • tensile stress maxima are illustrated in Figures 7b and 7c for examples intended for drag bit applications. They are the axial tensile maximum in the PCD material volume positioned between the dotted line 709 and the cylindrical free surface, forming a ring of highly tensed material and the combined radial and hoop tensile maximum in the cemented hard metal substrate positioned between the dotted line 707 and the line representing the interfacial barrier, 701 , which separate the PCD material volume and the cemented hard metal substrate.
  • the tensile stress maxima are illustrated in Figures 10c and 10d for examples intended for roller cone bit applications. They are the axial tensile stress maxima in the PCD material volume 1006 and the combined hoop and radial tensile maxima, 1004, in the cemented hard metal substrate. It may be advantageous if the magnitude of these tensile stress maxima were to be reduced. A general way of doing this may be to minimize the difference between the average coefficient of thermal expansion of the PCD material volume and that of the cemented hard metal substrate.
  • the high linear coefficient of thermal expansion at the top of the range may restrict the PCD material to having a high metal cobalt content of at least above 9 volume per cent.
  • the cemented hard metal grades typically used in subterranean rock drilling applications are cobalt cemented tungsten carbide grades chosen within the range of 6 to 14 weight per cent cobalt. Cemented hard metal carbide with low coefficient of thermal expansion may be restricted to grades with low cementing metal contents at most 10 weight per cent (16.3 volume per cent) cobalt.
  • Examples which exhibit lowered tensile stress maxima may be used where the metallic network of the PCD material is, for example, a cobalt-carbon alloy and the cementing metal of the hard metal substrate is, for example, a cobalt-tungsten-carbon alloy and the average metal content of the PCD material volume is, for example, greater than around 9 volume per cent (20 weight per cent) together with the average cobalt content of the hard metal substrate being less than around 16.3 volume per cent (10 weight per cent).
  • compositions and structure of the PCD material are macroscopically invariant and homogeneous across the dimensional extent of the PCD material volume.
  • the composition and structure of the cemented hard metal substrates may also be invariant across the dimensional extent of the substrate, i.e., made of one grade of cemented hard metal for these examples.
  • Residual stress distributions extending across the macroscopic dimensions of high pressure high temperature PCD material bodies may be altered, manipulated and chosen by grading the composition of PCD material across the dimensions of the bodies. This may be done by graduating and changing the metal composition as a function of position in the PCD material volume such that the linear coefficient of thermal expansion is different as a function of position in the PCD material volume.
  • the differential shrinkage of the PCD material from position to position during the cooling and pressure reduction phase of high pressure high temperature manufacturing process then induces residual stress from position to position.
  • This method may be used by such positional choice of PCD material composition and structure to assist in reducing the intensity of tensile stress maxima and thus render them less likely to cause undesirable crack related fracture events such as chipping, spalling and delamination. This may be done by altering the composition and structure in a graduated way across the dimensions of the PCD material volume and/or by using discrete adjacent volumes of PCD materials differing appropriately in composition and linear coefficient of thermal expansion.
  • FIGS. 1 1 a and 1 1 b are cross-sectional diagrams representing the arrived at examples for drag bit and roller cone bit applications, respectively.
  • the PCD material volumes and cemented hard metal substrate are labelled 1 101 and 1 102, respectively.
  • the interfacial barrier layer material is represented by the line 1 103.
  • the functional working volume is the volume between a point on the circumferential edge, 1 104, and the dotted line 1 105.
  • the point 1 104 represents the initial part of the functional working volume to be made to bear on the rock during rock drilling applications.
  • the functional working volume is represented by the volume of PCD material between the apex 1 106 and the dotted line 1 105.
  • the apex 1 106 represents the initial part of the functional working volume to bear on the rock during drilling applications.
  • Examples where the linear coefficient of thermal expansion of the PCD material increases in the general direction away from a point which is part of the functional working volume which initially bears upon the rock in use, towards the interfacial barrier layer separating the PCD material volume and the cemented hard metal substrate may be advantageous due to the reduction of the residual stress maxima.
  • the value of the linear coefficient of thermal expansion of the PCD material at any given position in the PCD material volume is determined by the elemental composition and quantity of the metal component of the PCD material at and close to that given position.
  • the metal type or alloy is invariant across the dimension of the PCD material volume, the linear coefficient of thermal expansion is varied by the metal content alone. The higher metal contents correspond to PCD materials of the highest coefficient of thermal expansion. The converse is also true.
  • Examples where the metal of the PCD material is invariant as regards the metal type or alloy across the dimensions of the PCD material volume and where the metallic content of the PCD material increases in the general direction away from a point which is part of the functional working volume which initially bears upon the rock in use, towards the interfacial barrier layer separating the PCD material volume and the cemented hard metal substrate may be advantageous due to the reduction of the magnitude of the residual stress maxima.
  • a convenient way of generally increasing the linear coefficient of thermal expansion across a macroscopic dimension in a particular direction may be to employ discrete adjacent volumes of PCD materials differing in linear coefficient of thermal expansion and metal content. The differential shrinkage of the appropriately differing PCD material adjacent volumes may thus provide for a reduction in the overall shrinkage of the overall PCD material volume.
  • one or more examples may comprise a PCD material volume comprising two or more layers of differing PCD material, the first layer of lowest linear coefficient of thermal expansion and metal content extends from the free surface and encompasses the functional working volume, with the second or subsequent layers of higher linear coefficient of thermal expansion and metal content separating the first layer from the interfacial barrier which separates the PCD material volume and the cemented hard metal substrate.
  • Such examples using simple layers of differing PCD material may be very conveniently made and may significantly reduce the magnitude of critical residual stress tensile maxima. An example which demonstrates this is shown in Figure 12.
  • Figure 12 is a half cross-section of an example intended for drag drill bit applications, which is a rock removal body of overall right cylindrical shape, is 16mm in diameter, 16mm in overall length, with a PCD material volume of 6mm thickness and cemented hard metal substrate of close to 10mm long. This overall shape, and the dimensions and thickness of PCD material volume correspond to the example presented in Figure 7b.
  • Figure 12 shows the form of the residual stress distribution in the example as derived from Finite Element Analysis (FEA).
  • the PCD material volume, 1201 comprises a first layer of PCD material, 1202, of 3.5mm thickness, with linear coefficient of thermal expansion less than a second layer of PCD material, 1203, of thickness 2.5mm which separates the first PCD material layer from the interfacial barrier layer represented by the line 1204.
  • the catalyst/solvent metal forming the metallic network in the PCD material volume 1201 was cobalt.
  • the first layer of PCD material, 1202 had a cobalt content of 6.7 volume per cent and the second layer of PCD material had a cobalt content of 1 1.5 volume per cent.
  • the cemented hard metal substrate 1205 was chosen to comprise a tungsten carbide cobalt cemented hard metal with a cobalt content of 13 weight per cent and a linear coefficient of thermal expansion of 5.6 ppm.°K ⁇ 1 .
  • the principal residual stress distribution is presented in Figure 12 by a series of grey shaded volumes which are delineated and separated by contour lines of equal stress. The zero stress contour lines, separating regions of tensile and compressive residual stress are indicated by dotted lines with the volumes under residual compression being cross- hatched. Note that the principal residual stress in the functional working volume is low.
  • the functional working volume is indicated as the volume of material between the specific point 1206 and the dotted line 1207.
  • 1206 is the specific point on the circumferential edge of the PCD volume which is chosen to initially bear on the rock during the application.
  • the functional working volume extends down the circumferential free surface by a chosen 3mm.
  • the principal tensile residual stress maximum, 1208, is at a position on the circumferential free surface of the PCD material volume immediately above the interfacial barrier layer 1204, forming a ring around the circumference in the second PCD material layer 1203.
  • This residual stress maximum, 1208, is dominated by an axial tensile stress and corresponds in position to the maximum tensile residual stress indicated in Figure 1 1a, 1 107, and Figure 7b, 709.
  • the principal residual stress in the cemented hard metal substrate at the base and circumferential free surface is low, ostensibly neutral.
  • the tensile residual stress progressively increases in magnitude and reaches a maximum immediately below the interfacial barrier layer 1204.
  • the position of this maximum principal tensile residual stress is indicated by 1209.
  • the maximum residual tensile stress 1209 corresponds to the tensile stress maximum in Figure 1 1a, 1 108, and the indicated maximum in Figure 7b, 707. This tensile residual stress maximum is dominated by radial and hoop tensile stress components at this position in the cemented hard metal substrate.
  • the first layer of lowest linear coefficient of thermal expansion and metal content extends from the free surface and encompasses the functional working volume, with the second or subsequent layers of higher linear coefficient of thermal expansion and metal content separating the first layer from the interfacial barrier which separates the PCD material volume and the cemented hard metal substrate.
  • Such examples may be valuable for some applications as these critical stress maxima may be significantly reduced in magnitude. This reduction may provide for a beneficial reduced tendency for the cemented hard metal substrates of these examples to delaminate and split during rock drilling applications.
  • graduating the properties of the cemented hard metal substrate may also be employed to reduce the differential shrinkage indicated by the arrows 1 109 and 1 1 10 in Figure 1 1a and 1 1 b.
  • a reduction in the differential shrinkage may give rise to lowering the bending effect which occurs at the end of the high pressure high temperature manufacturing process which may result in a beneficial reduction of the magnitude of the tensile stress maxima already described and indicated by 1 107 and 1 108.
  • composition and resultant properties of the cemented hard material are altered such that the linear coefficient of thermal expansion decreases in the general direction from the central point of the base of the substrate 1 1 12, towards the interfacial barrier layer 1 103, indicated by the arrows 1 1 13, such a reduction of the magnitude of the tensile residual stress maxima may occur.
  • some of the examples may have a linear coefficient of thermal expansion of the cemented hard metal substrate decreasing in the general direction away from the central point of the base of the body towards the interfacial barrier layer separating the PCD material volume and the cemented hard metal substrate.
  • the cemented hard metal substrate is made of one type of hard metal material such that the cementing metal and the hard compound are invariant as regards metal type and molecular composition, then the amount of cementing metal may decrease in the general direction away from the central point of the base of the body towards the interfacial barrier layer separating the PCD material volume and the cemented hard metal substrate.
  • a convenient way of generally decreasing the linear coefficient of thermal expansion of the cemented hard metal substrate across a macroscopic dimension in a chosen general direction may be to employ discrete adjacent volumes of cemented hard metal materials differing in linear coefficient of thermal expansion and cementing metal content.
  • a set of examples in this regard may use parallel layers of differing hard metal material of varying thickness.
  • the first layer of highest linear coefficient of thermal expansion and metal content may extend from the basal free surface of the substrate, with the second or subsequent layers of lower linear coefficient of thermal expansion and metal content separating the first layer from the interfacial barrier which separates the PCD material volume and the cemented hard metal substrate.
  • Figure 13 is an example based upon the shape and dimensions of the example represented by Figure 7b, which illustrates the potential benefits of employing such appropriately arranged discrete layers of differing cemented hard metal carbide materials.
  • the PCD material volume 1301 may comprise, for example, a homogeneous PCD material with a linear coefficient of thermal expansion of around 4.0 ppm.°K-1 and a cobalt content of around 9 volume per cent (around 20 weight per cent).
  • the cemented hard metal substrate, 1302 comprises two layers of differing material 1303 and 1304. The boundary between these layers is substantially planar and parallel to the base of the substrate.
  • the layer 1303 extending from the base of the substrate may be around 8mm thick and made of a tungsten carbide cobalt hard metal with around 14 weight per cent cobalt (around 22.2 volume per cent) and may have a linear coefficient of thermal expansion of around 6.01 ppm.oK-1.
  • the layer 1304, which separates the layer 1303 from the interfacial barrier layer 1305 may be around 2mm thick and may comprise a tungsten carbide cobalt hard metal with around 6 weight per cent (10.1 volume per cent) cobalt and a linear coefficient of thermal expansion of around 5.09 ppm.oK-1.
  • the principal residual stress distributions in this example are presented as zones of varying shades of grey as before, with the same general qualitative character as exhibited in Figures 7b and 12.
  • the positions of the axial dominated tensile principal residual stress maximum, 1306, in the PCD material volume, 1301 corresponds to 709 in Figure 7b, 1 107 in Figure 1 1a and 1208 in Figure 12.
  • the position of the radial and hoop component dominated tensile principal stress maximum, 1307, in the hard metal substrate 1302 corresponds to 707 in Figure 7b and 1 108 in Figure 1 1a and 1208 in Figure 12.
  • Finite element analysis carried out on this example demonstrated that the magnitude of both the critical tensile stress maxima, 1306 and 1307, is reduced by around 35 per cent as compared to the corresponding maxima 709 and 707 in Figure 7b.
  • this example may be considered to show a significant reduction in the magnitude of these critical tensile stress magnitudes. This may be highly beneficial, leading to a significantly reduced risk and probability of delamination and splitting of the cemented hard metal substrate during rock drilling applications.
  • the examples of Figure 12 and Figure 13 may be combined to form yet another example which is shown in Figure 14.
  • the two layered arrangement of differing PCD materials of Figure 12 are combined with the two layer arrangement of differing tungsten carbide cobalt hard metal of Figure 13.
  • Finite element analysis of this example shows that the magnitude of the tensile principal stress maxima, 1401 and 1402, corresponding to the critical stress maxima, 709 and 707 in Figure 7b, and 1 107 and 1 108 in Figure 1 1a, may reduced by around 60 per cent.
  • This example illustrates the potential value in combining the grading of the PCD material volume in composition and structure such that the linear coefficient of thermal expansion of the PCD material increases in the general direction away from a point which is part of the functional working volume which initially bears upon the rock in use, towards the interfacial barrier layer separating the PCD material volume and the cemented hard metal substrate, with the decreasing of the linear coefficient of thermal expansion of the hard metal substrate in the general direction away from the central point of the base of the body towards the interfacial barrier layer separating the PCD material volume and the cemented hard metal substrate.
  • the metal network in the PCD material volume is cobalt and the cemented hard metal substrate is tungsten carbide cobalt.
  • the examples for drag bit applications shown in Figures 12, 13 and 14 may be generally applicable, and include the examples intended for use in roller cone applications whereby the rock removal body comprises a right circular cylinder with one end forming a generally convex curved surface with an apex.
  • the PCD material volumes in such examples may extend from the apices and the curved free surface.
  • the examples so far described above exhibit a flat planar thin interfacial barrier layer derived from a refractory material which acts as a metal diffusion blocking barrier to the molten bonding material of the hard metal substrate and the molten catalyst solvent sintering aid of the polycrystalline material during the high pressure high temperature manufacturing process.
  • the residual stress distribution in the PCD material volume of general composite PCD hard metal substrate bodies may be favourably altered by employing a non-flat, non-planar interface or boundary between the PCD material volume and the hard metal substrate. More explicitly, such non-planar interfaces or boundaries may have improved value in reducing tensile residual stress maxima, for example if they exhibit a general arcuitly convex curvature towards the PCD material volume.
  • Example 1 Rock removal bodies intended for subterranean rock drilling using drag bit designs and technology were made corresponding to the embodiment illustrated in Figure 14.
  • This example was a combination of the two cylindrical layer PCD material volume of Figure 12 and the two cylindrical layer cemented hard metal substrate of Figure 13.
  • the bodies each comprised a right circular cylinder of 16 mm diameter and overall length 16 mm with one end forming a cylindrical PCD material volume of thickness 6 mm, with a cemented hard metal substrate disposed at the opposite cylindrical end of the body.
  • the PCD material volume of each body was comprised of a first cylindrical layer, 1202, of 3.5 mm thickness extending from the flat top circular free surface of the body and a second layer, 1203, of 2.5 mm thickness separating the first PCD layer from an extant barrier boundary layer and the cemented hard metal substrate.
  • the first layer will completely encompass the functional working volume in use, which extends about 3mm down the barrel free surface of the PCD material volume from a chosen point at a circumferential edge of the body, this point being the point of initial contact with the rock strata.
  • This first layer was made from a multimodal PCD material with an average grain size of close to 10 micro meters, with the grain size distribution extending from about 1 to 30 micro meters.
  • the term multimodal in this context refers to the starting diamond powder, which was produced by combining five separate powers, differing in average particle size distribution.
  • the first layer was made from five component diamond powders having a single maximum in particle size distribution and hence each component being monomodal.
  • the metal employed as catalyst solvent for partial re-crystallization of the diamond was cobalt, resulting in the interpenetrating network of the resultant PCD material being high carbon containing cobalt.
  • the PCD material had a cobalt content of 6.7 % by volume (15.4% by weight). This composition of PCD material is known to have a linear coefficient of thermal expansion of 3.7ppm°K "1 .
  • This second layer was made from a multimodal PCD material with an average grain size of close to 6 micro meters, with the grain size distribution extending from about 1 to 20 micro meters.
  • This layer was made from three component diamond powders having a single maximum in particle size distribution and hence each component being monomodal.
  • the metal employed as catalyst solvent for partial re-crystallization of the diamond was cobalt, resulting in the interpenetrating metallic network of the resultant PCD material being high carbon containing cobalt.
  • the PCD material had a cobalt content of 1 1.5 % by volume (24.7% by weight).
  • This composition of PCD material is known to have a linear coefficient of thermal expansion of 4.4ppm°K ⁇ 1 .
  • the two layer hard metal substrate was made from tungsten carbide cemented with cobalt.
  • This grade of hard metal had a linear coefficient of thermal expansion of 6.01 ppm°K ⁇ 1 .
  • This grade of hard metal had a linear coefficient of thermal expansion of 5.09ppm°K ⁇ .
  • Precursor compounds for the metal in this case cobalt, are precipitated, nucleated and grown on the surface of the diamond particles by using reactions between soluble reactants whilst suspending the diamond powder in water. After removal from suspension, drying and subsequent heat treatment in reducing environments the diamond particle surfaces are decorated in pure metal particles, thus ensuring an extremely high degree of homogeneity of mixing with respect to the diamond and metal components.
  • the stock mass for the material of the first PCD layer was produced using the following procedural steps.
  • 100g of diamond powder was suspended in 2.5 litres of de-ionised water.
  • the diamond powder comprised 5 separate monomodal diamond fractions each differing in average particle size.
  • the diamond powder was thus considered to be multimodal.
  • the 100g of diamond powder was made up as follows: 5g of average particle size 1.8 micro meters, 16g of average particle size 3.5 micro meters, 7g of average particle size 5 micro meters, 44g of average particle size 10 micro meters and 28g of average particle size 20 micro meters. This multimodal particle size distribution extended from about 1 micro meter to about 30 micro meters.
  • the diamond powder had been rendered hydrophilic by prior acid cleaning and washing in de-ionised water.
  • an aqueous solution of cobalt nitrate and a separate aqueous solution of sodium carbonate were simultaneously slowly added while the suspension was vigorously stirred.
  • the cobalt nitrate solution was made by dissolving 93 g of cobalt nitrate hexahydrate crystals, Co(N0 3 ) 2 .6H 2 0, in 200ml of de-ionised water.
  • the sodium carbonate solution is made by dissolving 33.9 g of pure anhydrous sodium carbonate, Na 2 C0 3 in 200ml of de-ionised water.
  • the cobalt nitrate and sodium carbonate reacted in solution precipitating cobalt carbonate C0CO 3 , as per the following equation,
  • the cobalt carbonate crystals In the presence of the suspended diamond powder particles, with their hydrophilic surface chemistry, the cobalt carbonate crystals nucleated and grew on the diamond particle surfaces.
  • the cobalt carbonate precursor compound for cobalt took the form of whisker shaped crystals decorating the diamond particle surfaces.
  • the sodium nitrate product of reaction was removed by a few cycles of decantation and washing in de-ionised water.
  • the powder was finally washed in pure ethyl alcohol, removed from the alcohol by decantation and dried under vacuum at 60°C.
  • the dried powder was then placed in an alumina ceramic boat with a loose powder depth of about 5mm and heated in a flowing stream of argon gas containing 5% hydrogen.
  • the top temperature of the furnace was 750°C which was maintained for 2 hours before cooling to room temperature.
  • This furnace treatment dissociated and reduced the cobalt carbonate precursor to form pure cobalt particles, with some carbon in solid solution decorating the surfaces of the diamond particles. In this way it was ensured that the cobalt particles were always smaller than the diamond particles with the cobalt being homogeneously distributed.
  • the conditions of the heat treatment were chosen with reference to the standard cobalt carbon phase diagram of the literature. At 750°C it may be seen that the solid solubility of carbon in cobalt is low.
  • the stock mass for the material of the second PCD layer was produced using the following procedural steps.
  • 100g of diamond powder was suspended in 2.5 litres of de-ionised water.
  • the diamond powder comprised 3 separate monomodal diamond fractions each differing in average particle size.
  • the diamond powder was thus considered to be multimodal.
  • the 100g of diamond powder was made up as follows: 18g of average particle size 4 micro meters, 70g of average particle size 6 micro meters and 12g of average particle size 12 micro meters. This multimodal particle size distribution extended from about 1 micro meter to about 20 micro meters.
  • the same sequential steps were then carried to precipitate a cobalt carbonate precursor for the cobalt metal onto the surfaces of the diamond particles as that for the stock mass for the first PCD layer material save that the cobalt nitrate solution was made by dissolving 160g of cobalt nitrate hexahydrate crystals, Co(N0 3 )2.6H 2 0, in 200ml of de-ionised water.
  • the sodium carbonate solution is made by dissolving 60g of pure anhydrous sodium carbonate, Na 2 C0 3 in 200ml of de-ionised water.
  • the resultant powder mass of multimodal diamond particles with an overall 24.7 weight % of cobalt metal decorating the diamond particle surfaces was stored under dry nitrogen in an air-tight container to prevent oxidation of the fine cobalt decorating the diamond surfaces.
  • the tantalum encompassed end of the substrate was then inserted into the open end of the diamond mass containing canister, 1503, such that the end wall of the canister, 1506, separated the diamond mass from the substrate, and further uniaxial compacted to form the assembly.
  • the assembly was inserted into a third canister of slightly larger diameter, 1507, vacuum degassed and sealed under vacuum using procedures known in the art.
  • the canister assembly was then subjected to a cold isostatic compaction procedure at a pressure of 200MPa. Several so called green body assemblies were produced in this manner.
  • end wall of canister, 1506 separates the diamond particulate masses which will form the PCD material volume and the hard metal substrate.
  • This thin, about 50 micro meters thick, tantalum end wall layer acted as a barrier to both the molten cementing cobalt of the substrate and the molten cobalt of the PCD material layer during sintering of the diamond PCD layer at high pressure and temperature.
  • the metallic component of the PCD material volume and the cementing metal of the hard metal substrate were independent of one another, independently derived and did not interacted during the high pressure high temperature manufacturing process.
  • an extant partially carburised tantalum layer separated the PCD material volume from the substrate.
  • each green body assembly was then placed in an assembly of compactable ceramic, salt components suitable for high pressure high temperature treatment as well established in the art.
  • the material immediately surrounding the encapsulated green body was made from very low shear strength material such as sodium chloride. This provides for the green bodies being subjected to pressures which approach a hydrostatic condition. In this way pressure gradient induced distortions of the green body may be mitigated.
  • the green body canister assemblies were then subjected to a pressure of 6GPa and a temperature of approximately 1560°C for 1 hour using a belt type high pressure apparatus as well established in the art. During the end phase of the high pressure high temperature procedure the temperature was slowly reduced over several minutes to approximately 750°C, maintained at this value and then the pressure was reduced to ambient conditions. The high pressure assembly was then allowed to cool to ambient conditions before extraction from the high pressure apparatus. This procedure during the end phase of the high pressure high temperature treatment was thought to allow the surrounding salt media to remain in a plastic state during the removal of pressure and so prevent or inhibit shear forces bearing upon the now sintered PCD body.
  • the bodies each comprised a right circular cylinder with one end forming a generally convex surface, specifically a hemisphere, with a PCD material volume extending from the apex, 1001 , of the hemisphere.
  • a hard metal substrate was disposed at the opposite cylindrical end of the body. This substrate was made of a cobalt cemented tungsten carbide hard metal, with 12.75 weight percent of cobalt.
  • the PCD material volume was separated from and bonded to the cemented cylindrical hard metal substrate by a partially carburized tantalum interfacial layer of 50 micro meters thickness, indicated by the line 1003 in figure 10d.
  • This layer acted as a barrier during manufacture and prevented the molten cementing metal of the hard metal substrate and the molten metal of the PCD material volume interacting.
  • the diameter of the cylindrical part of the bodies was finished to be 16 mm.
  • the overall length of each body was 27 mm as measured from the apex, 1001 , along the axis of the body to the center of the circular base.
  • the length of the PCD material volume as measured from the apex, 1001 , to the intersection of the axial line, 1002, with the interfacial layer, 1003, was 16 mm.
  • the length of the tungsten carbide/cobalt substrate was close to 1 1 mm.
  • the PCD material volume was made of a multimodal PCD material with an average grain size of close to 10 micro meters, with the grain size distribution extending from about 1 to 30 micro meters.
  • the term multimodal in this context refers to the starting diamond powder, which was produced by combining five separate powers, differing in average particle size distribution. Each made of five component diamond powders having a single maximum in particle size distribution and hence being monomodal.
  • the metal employed as catalyst solvent for partial re-crystallization of the diamond was cobalt, resulting in the interpenetrating network of the resultant PCD material being high carbon containing cobalt.
  • the PCD material had a cobalt content of 9 % by volume (20% by mass).
  • Precursor compounds for the metal in this case cobalt, are precipitated, nucleated and grown on the surface of the diamond particles by using reactions between soluble reactants whilst suspending the diamond powder in water. After removal from suspension, drying and subsequent heat treatment in reducing environments the diamond particle surfaces are decorated in pure metal particles, thus ensuring an extremely high degree of homogeneity of mixing with respect to the diamond and metal components.
  • 100g of diamond powder was suspended in 2.5 litres of de-ionised water.
  • the diamond powder comprised 5 separate monomodal diamond fractions each differing in average particle size.
  • the diamond powder was thus considered to be multimodal.
  • the 100g of diamond powder was made up as follows: 5g of average particle size 1.8 micro meters, 16g of average particle size 3.5 micro meters, 7g of average particle size 5 micro meters, 44g of average particle size 10 micro meters and 28g of average particle size 20 micro meters. This multimodal particle size distribution extended from about 1 micro meter to about 30 micro meters.
  • the diamond powder had been rendered hydrophilic by prior acid cleaning and washing in de-ionised water.
  • an aqueous solution of cobalt nitrate and a separate aqueous solution of sodium carbonate were simultaneously slowly added while the suspension was vigorously stirred.
  • the cobalt nitrate solution was made by dissolving 125 grams of cobalt nitrate hexahydrate crystals, Co(N0 3 ) 2 .6H 2 0, in 200ml of de-ionised water.
  • the sodium carbonate solution is made by dissolving 45.5g of pure anhydrous sodium carbonate, Na 2 C0 3 in 200ml of de-ionised water.
  • the cobalt nitrate and sodium carbonate reacted in solution precipitating cobalt carbonate C0CO 3 , as per the following equation,
  • the cobalt carbonate crystals In the presence of the suspended diamond powder particles, with their hydrophilic surface chemistry, the cobalt carbonate crystals nucleated and grew on the diamond particle surfaces.
  • the cobalt carbonate precursor compound for cobalt took the form of whisker shaped crystals decorating the diamond particle surfaces.
  • the sodium nitrate product of reaction was removed by a few cycles of decantation and washing in de-ionised water.
  • the powder was finally washed in pure ethyl alcohol, removed from the alcohol by decantation and dried under vacuum at 60°C.
  • the dried powder was then placed in an alumina ceramic boat with a loose powder depth of about 5mm and heated in a flowing stream of argon gas containing 5% hydrogen.
  • the top temperature of the furnace was 750°C which was maintained for 2 hours before cooling to room temperature.
  • This furnace treatment dissociated and reduced the cobalt carbonate precursor to form pure cobalt particles, with some carbon in solid solution decorating the surfaces of the diamond particles. In this way it was ensured that the cobalt particles were always smaller than the diamond particles with the cobalt being homogeneously distributed.
  • the conditions of the heat treatment were chosen with reference to the standard cobalt carbon phase diagram of the literature. At 750°C it may be seen that the solid solubility of carbon in cobalt is low.
  • the resultant powder mass of multimodal diamond particles with an overall 20 weight % of cobalt metal decorating the diamond particle surfaces had a pale light grey appearance.
  • the powder mass was stored under dry nitrogen in an air-tight container to prevent oxidation of the fine cobalt decorating the diamond surfaces.
  • each rock removal body 1 1.4g of the stock particulate mass was then pre-compacted into a hemispherical ended tantalum canister in a uniaxial hard metal compaction die to form a semi-dense hemispherical ended right cylindrical body.
  • the 12.75 weight % cobalt, tungsten carbide cylindrical substrate for each body was inserted into a tantalum canister with wall thickness of 50 micro meters.
  • the tantalum encompassed end of the substrate was then inserted into the open end of the diamond mass containing canister such that the end wall of the canister separated the diamond mass from the substrate, and further uniaxial compacted to form an assembly.
  • the assembly was inserted into a third canister of slightly larger diameter, vacuum degassed and sealed under vacuum using procedures known in the art.
  • the canister assembly was then subjected to a cold isostatic compaction procedure at a pressure of 200MPa. Several so called green body assemblies were produced in this manner.
  • each green body assembly was then placed in an assembly of compactable ceramic, salt components suitable for high pressure high temperature treatment as well established in the art.
  • the material immediately surrounding the encapsulated green body was made from very low shear strength material such as sodium chloride. This provides for the green bodies being subjected to pressures which approach a hydrostatic condition. In this way pressure gradient induced distortions of the green body may be mitigated.
  • the green body canister assemblies were then subjected to a pressure of 6GPa and a temperature of approximately 1560°C for 1 hour using a belt type high pressure apparatus as well established in the art. During the end phase of the high pressure high temperature procedure the temperature was slowly reduced over several minutes to approximately 750°C, maintained at this value and then the pressure was reduced to ambient conditions. The high pressure assembly was then allowed to cool to ambient conditions before extraction from the high pressure apparatus. This procedure during the end phase of the high pressure high temperature treatment was thought to allow the surrounding salt media to remain in a plastic state during the removal of pressure and so prevent or inhibit shear forces bearing upon the now sintered PCD body.
  • the fully dense, hemispherical ended right cylindrical bodies were then brought to dimensions of 16mm diameter and 27mm long by finishing procedure such as fine diamond grinding and polishing as well established in the art.
  • one or more examples including polycrystalline bodies not deriving their required metal from substrate materials may be formed of PCD bodies of high homogeneity with their greatest dimensions possibly being around 150mm or more, limited only by the design and scale of high pressure and high temperature apparatus known in the art and currently available.
  • the PCD materials exploited in such examples may include PCD material compositions not accessible using conventional PCD manufacture, such as fine grained PCD with low metal contents, coarse grain PCD with high metal contents, both outside the band 501 of Figure 5.
  • the range and accuracy of composition of highly specific alloys to aid the diamond particle sintering in the examples may be significantly extended beyond those conventionally accessible, the latter being largely restricted to the cementing metal of sintered hard metal substrates.
  • the PCD bodies may be macroscopically residual stress free at a scale greater than ten times the average grain size of the PCD material where the maximum grain size is no more than three times the average grain size. This distinguishes such PCD bodies over conventional prior art PCD bodies made attached to large substrates where, due to differential expansion and contraction on return-to-room conditions during manufacture, large and significant residual stress distributions may arise in both the PCD volume and substrate volume of the overall body. These large residual stress distributions involving both compressive and tensile regions are taught to be the life determining aspects in rock drilling applications. The PCD bodies of the examples therefore may assist in increasing the life of cutters incorporating such PCD bodies in rock drilling applications.
  • the rock removal bodies of the examples may maintain the conventional overall shape of a simple right cylinder and the well-established custom and practice of brazing these cylinders into the housing bodies of the tools into which they are to be inserted via the cemented hard metal substrate may also be maintained.
  • some of the examples may provide a means of exploiting the key advantages of free standing PCD bodies but with the inclusion of a substrate attached during the PCD material manufacturing procedure. In this way, the standard extremely well-established designs of drill bits and housing bodies together with the brazing related attachment procedures may be exploited and modifications and re-designs of such aspects may not be required.
  • some examples thus concern the means of making rock removal bodies, of general right cylindrical shape, where the attributes of the procedures of making free standing PCD bodies are made use of but substrates of general hard metal materials are attached in-situ during the manufacturing procedures.

Abstract

Corps d'enlèvement de roche comprenant un matériau PCD (601) lié à un substrat (602) le long d'une interface. Le corps est de forme cylindrique circulaire droite et le matériau PCD a une épaisseur (607), depuis le bord circonférentiel axialement le long de la surface de la partie cylindre, d'environ 3 mm ou plus, et un volume actif fonctionnel (606) ayant une étendue maximale telle que la surface d'usure finale ne croise pas l'interface du volume de matériau PCD et du substrat. Le volume de matériau PCD comprend un réseau en diamant et un composant métallique formant un réseau métallique, le substrat comprend un métal de cimentation, le composant métallique et le métal de cimentation étant indépendants l'un de l'autre, indépendamment dérivés, n'ayant pas interagi durant le processus de fabrication à pression élevée et à pression élevée, pouvant être différenciés par mesure et étant présélectionnés pour être différents par rapport à leur composition d'alliage. Le matériau PCD englobe le volume actif fonctionnel et est homogène.
PCT/EP2014/069587 2013-09-16 2014-09-15 Corps d'enlèvement de roche WO2015036585A1 (fr)

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US15/021,828 US20160230473A1 (en) 2013-09-16 2014-09-15 A rock removal body
CN201480061793.6A CN105723047A (zh) 2013-09-16 2014-09-15 岩石去除体

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GBGB1316456.1A GB201316456D0 (en) 2013-09-16 2013-09-16 A rock removal body
GB1316456.1 2013-09-16

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WO2015072250A1 (fr) * 2013-11-15 2015-05-21 住友電工ハードメタル株式会社 Corps lié à un diamant, outil le comportant et procédé de production d'un corps lié à un diamant
GB201703626D0 (en) * 2017-03-07 2017-04-19 Element Six (Uk) Ltd Strike tip for pick up tool
EP3830380A4 (fr) * 2018-08-02 2022-04-06 US Synthetic Corporation Outil de coupe à inserts de diamant polycristallin, systèmes les incorporant et procédés associés
CN110095287B (zh) * 2019-04-18 2020-09-22 杭州电子科技大学 直叶片变量泵定子内表面摩擦磨损测试方法

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GB201416218D0 (en) 2014-10-29
GB2521891A (en) 2015-07-08
US20160230473A1 (en) 2016-08-11
GB2521891B (en) 2016-02-24
GB201316456D0 (en) 2013-10-30
CN105723047A (zh) 2016-06-29

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