WO2016099943A1

WO2016099943A1 - Polycrystalline diamond constructions with enhanced surface features

Info

Publication number: WO2016099943A1
Application number: PCT/US2015/063906
Authority: WO
Inventors: Haibo Zhang; John BELNAP; Yi Fang
Original assignee: Smith International, Inc.
Priority date: 2014-12-18
Filing date: 2015-12-04
Publication date: 2016-06-23

Abstract

Polycrystalline diamond (PCD) constructions and cutting elements include a PCD body having a composite layer with a number of PCD particles dispersed in a surrounding PCD matrix. The composite layer has a wear surface including asperities projecting outwardly therefrom, where the asperities are formed from the PCD particles. In an embodiment, the asperities enhance the efficiency of breaking rock during a drilling operation. The body includes one or more PCD transition layers between the composite layer and a metallic substrate attached to the diamond-bonded body. The one or more transition layers may have a hardness that is the same or less than the hardness of the composite layer.

Description

POLYCRYSTALLINE DIAMOND CONSTRUCTIONS

WITH ENHANCED SURFACE FEATURES

CROSS REFERENCE

[0001] This application claims the benefit of U.S. Provisional Application No. 62/093,893, entitled "POLYCRYSTALLINE DIAMOND CONSTRUCTIONS WITH ENHANCED

SURFACE FEATURES," filed December 18, 2014, the disclosure of which is hereby incorporated herein by reference.

BACKGROUND

[0002] Polycrystalline diamond (PCD) has been widely used as a component in wear and cutting elements in industrial applications, such as for drilling subterranean formations and metal machining, for many years. Typically, such cutting elements including PCD include a PCD body or table that is disposed on or attached to a metallic substrate. The metallic substrate is used to join the cutting element to a desired cutting or drilling device, and the PCD is positioned along a wear surface of the cutting element. Placement of PCD at the cutting element wear surface is desired to take advantage of the relative enhanced wear and abrasion resistant properties of PCD, thereby providing a desired cutting element service life when placed into a drilling or cutting end-use application.

[0003] The PCD body or table used in such conventional PCD cutting elements typically includes a homogeneous structure of intercrystalline bonded diamond forming a continuous matrix phase of diamond extending throughout the PCD material, with interstitial regions dispersed within the diamond matrix phase that may or may not include a catalyst material used to form the PCD during high pressure/high temperature (HPHT) conditions. Such PCD materials are characterized by having a body or table surface that, while having the above-noted properties of enhanced wear resistance and abrasion resistance inherent in PCD, has a surface that is relatively smooth. A known result of using such conventional PCD cutting elements in drilling applications, e.g., when installed on a rotary cone drill bit or a percussion bit and placed into service, is that they tend to cause the earthen formation that they contact to be crushed or pulverized into fine cuttings and powder. The formation of such fines cuttings and powder during the drilling operation actually operates to impair further drilling as the fine cuttings and powder tend to stay near and be impacted around the drill site, thereby reducing drilling efficiency.

[0004] It is, therefore, desired that diamond-bonded constructions and cutting elements including the same be developed and constructed in a manner that operates to provide an enhanced degree of drilling efficiency, when compared to the above-described conventional PCD cutting elements, while still retaining and not sacrificing the desired enhanced properties of wear resistance and abrasion resistance along the wear surface to thereby provide a desired service life.

SUMMARY

[0005] Diamond-bonded, e.g., polycrystalline diamond, constructions and cutting elements as disclosed herein have a diamond-bonded body including a composite layer having a number of polycrystalline diamond particles dispersed in a surrounding polycrystalline diamond matrix phase. The polycrystalline diamond particles have an average particle size of between about 50 to 1,000 micrometers. The composite layer extends inwardly a partial depth from a wear surface of the body and includes a number of asperities projecting outwardly from the wear surface that are formed from the polycrystalline diamond particles. In an example, the composite layer has a thickness of from about 5 to 50 percent of a diameter of the polycrystalline diamond body.

Depending on the diameter, the composite layer thickness can be from about 0.75 to 2 mm. In an example, the polycrystalline diamond particles include from about 10 to 85 volume percent of the composite layer based on the total volume of the composite layer. In an example, the composite layer matrix phase has a hardness in the range of from about 1,800 to 3,200 HV, the polycrystalline diamond particles have a hardness above 3,000 HV, and the polycrystalline diamond particles have a hardness that is at least 500 HV higher than the matrix phase.

[0006] In an example, the asperities project an average distance from the composite layer wear surface of about 20 to 60 percent of the polycrystalline diamond average particle diameter.

Depending on the polycrystalline diamond particle size, the asperities may project an average distance from a wear surface of from about 30 to 210 microns. In an example, the asperities have an average width measured at the wear surface from about 20 to 100 percent of the polycrystalline diamond average particle diameter. In an example, the asperities cause rock in contact with the asperities to be broken into pieces, where greater than 75 percent of such pieces are sized between about 0.2 to 2 mm.

[0007] The diamond-bonded body includes a transition layer disposed beneath the composite layer that is substantially free of the polycrystalline diamond particles. The polycrystalline diamond in the second region has a diamond volume content that is different from that of the total diamond volume content in the first region. In an example, the transition layer has a thickness of from about 0.2 to 0.75 mm. In an example, the diamond volume content of the polycrystalline diamond in the transition layer is less than that of the composite layer polycrystalline diamond matrix phase. In an example, the diamond grains used to form the polycrystalline diamond matrix phase of the composite layer have an average particle size that is different from the diamond grains used to form the polycrystalline diamond of the transition layer region. In an example, the transition layer has a hardness in the range of from about 1,800 to 3,200 HV, and has a hardness equal to or less than the composite layer. The diamond-bonded construction may have more than one transition layer if desired. The diamond bonded construction further includes a metallic substrate attached to the diamond-bonded body.

[0008] Diamond-bonded constructions and cutting elements as disclosed herein, having a number of asperities projecting outwardly from a wear surface, may be made by combining a volume of polycrystalline diamond particles with diamond grains to form a composite layer, where the polycrystalline diamond particles have an average particle size of from about 150 to 350 microns. The polycrystalline diamond particles as used to form the composite layer may be provided in the form of post-sintered particles or as green- state/unsintered granules. A volume of diamond grains is positioned adjacent the composite layer and used to form an intermediate layer. A metallic substrate is positioned adjacent the intermediate layer to form an assembly. The assembly is subjected to high pressure/high temperature conditions in the presence of a catalyst material to sinter the diamond grains in the composite and intermediate layers and to attach the metallic substrate to the intermediate layer to form the cutting element. The asperities may be formed along the wear surface by abrasive process prior to sale and use of the cutting element, or may be formed during use of the cutting element in a wear or cutting end-use application.

[0009] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

BRIEF DESCRIPTION OF DRAWINGS

[0010] These and other features and advantages of diamond-bonded constructions and cutting elements comprising the same as disclosed herein will be appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

[0011] FIG. 1 is schematic side view of an example cutting element comprising the diamond- bonded construction as disclosed herein;

[0012] FIG. 2 is a cross-sectional side view of the example cutting element of FIG. 1 ;

[0013] FIG. 3 is a cross-sectional side view of a section of the example cutting element of FIGS. 1 and 2;

[0014] FIG. 4 is a cross-sectional side view of a further section of the example cutting element of FIG. 3;

[0015] FIG. 5 is a top plan view of an example cutting element comprising the diamond-bonded construction as disclosed herein;

[0016] FIG. 6 is a schematic side view of another example cutting element comprising the diamond-bonded construction as disclosed herein; [0017] FIG. 7 is a cross-sectional side view of the example cutting element of FIG. 6;

[0018] FIG. 8 is a perspective side view of a roller cone drill bit comprising a number of the cutting elements of FIG. 1 ;

[0019] FIG. 9 is a perspective side view of a percussion or hammer bit comprising a number of cutting elements of FIG. 1; and

[0020] FIG. 10 is a perspective side view of a drag bit comprising a number of the cutting elements of FIG. 6.

DETAILED DESCRIPTION

[0021] Ultra-hard constructions and cutting elements as disclosed herein are specially engineered to have a wear surface having surface features in the form of a number of asperities extending therefrom that break earthen formations when placed into contact therewith into a desired size for the purpose of reducing the extent of fine cuttings and powder to thereby enhance drilling efficiency. The ultra-hard constructions as disclosed herein include a composite layer positioned at the cutting element wear surface that includes ultra-hard particles dispersed in a surrounding ultra-hard matrix, where the ultra-hard particles are sized to provide the desired asperities along the wear surface. The ultra-hard constructions as disclosed herein further include one or more transition layers also including an ultra-hard material that are interposed between the composite layer and a substrate, where the one or more transition layers are substantially free of the ultra- hard particles used for forming the asperities along the wear surface.

[0022] As used herein, the term "ultra-hard" refers to a materials selected from the group of materials including diamond, polycrystalline diamond (PCD), cubic boron nitride (cBN), polycrystalline cubic boron nitride (PCBN), and the like. In an example, a ultra-hard material used for forming ultra-hard constructions and cutting elements as disclosed herein is a diamond- bonded material, preferably PCD. [0023] FIG. 1 illustrates a diamond-bonded construction in the form of a cutting element or cutting insert 10 comprising a diamond-bonded body or diamond-bonded table 12 that is attached to a substrate 14, according to an embodiment. In an embodiment, an outer surface of the diamond-bonded table forms a wear surface 16 of the cutting insert. In this example, the cutting insert 10 has a domed wear surface 12 having a hemispherical shape. It is to be understood that cutting inserts as disclosed herein may have a wear surface defined by more than one radius of curvature, and/or having a top section defined by a reduced radius of curvature to provide a relatively pointed top or tip.

[0024] Referring to FIG. 2, the example cutting insert 20 includes a PCD body or table 22 including a first region or composite layer 24 having an outer surface forming a wear surface 26 of the insert, where the composite layer projects inwardly from the wear surface 26 therefrom a depth to a second region or transition or intermediate layer 28. The PCD table 22 is attached via the transition layer 28 with a substrate 30. While the example cutting insert illustrated in FIG. 1 includes a single transition layer 28, it is to be understood that cutting elements as disclosed herein may include more than one transition layers between the composite layer 24 and the substrate 30 depending on such features as the materials selected to form the composite layer and/or the particular end-use application.

[0025] FIG. 3 is a section of the cutting insert 40 of FIG. 2 for better illustrating the materials making up the PCD table 42, according to an embodiment. Referring to FIGS. 3 and 4, the composite layer 44 includes a number of PCD particles 46 that are dispersed within a

surrounding PCD matrix 48. In an example, the PCD particles 46 are in the form of sintered PCD having a microstructure of intercrystalline bonded diamond with interstitial regions disposed therein, where a catalyst material is disposed within the interstitial regions. In an example, PCD particles are engineered to have a size that operates to form asperities 50, along the wear surface 52 of the cutting insert, to cause an earthen formation contacted therewith to be broken in a manner that reduces the amount of fine cuttings and powder. In an example, the asperities 50 are sized to cause an earthen formation to be broken into pieces, where a substantial amount of such pieces (that is, greater than about 75 percent of the total amount of broken pieces) is sized from about 0.2 to 2 mm. While it is understood that there may be a remaining amount of finer sized pieces, a feature of the asperities is that they function to reduce the amount of such fine cuttings and powder and increase the proportion of larger-sized pieces. In addition, the asperities may enhance the operation of crushing and gouging by creating secondary fractures in the earthen formation, providing improved drilling efficiency.

[0026] In an example, PCD particles 46 have an average particle size of about 50 to 1,000 microns, about 100 to 500, or about 150 to 350 microns. Sized in this manner, the asperities 50 disposed along the wear surface of the cutting element may project outwardly an average distance from the wear surface 52 an amount from about 20 to 60 percent of the average diameter of the PCD particles, which in an example may be from about 10 to 600 microns, about 20 to 100 microns, or about 30 to 210 microns depending on the particular average diameter of the PCD particles. Further, the asperities 50 may have a diameter as measured at the wear surface 52 that is from about 20 to 100 percent of the average diameter of the PCD particles, which in an example may be about 10 to 1,000 microns, 30 to 400 microns, or about 30 to 350 microns depending on the particular average diameter of the PCD particles.

[0027] FIG. 5 shows a cutting insert 36 including a wear surface 37 along the outer surface of a PCD diamond table including a plurality of the asperities 38 dispersed along the entire wear surface and projecting upwardly a distance therefrom. The asperities as disclosed herein may be formed before the cutting element is placed into use, e.g., by abrasive clean up processing or the like, or may be formed during use of the cutting element, e.g., whereby the cutting element is initially formed having a smooth wear surface and the asperities are formed shortly after commencement of use by the abrasion and wearing away of the PCD matrix material in the composite layer to thereby expose the PCD particles positioned at the wear surface.

[0028] Referring to FIG. 4, the composite layer 44 is illustrated as having the PCD particles 46 dispersed uniformly therein and within the surrounding PCD matrix 48. Alternatively, the PCD particles may be disposed substantially along the wear surface 52 of the composite layer 44, e.g., extending a partial depth therefrom within the composite layer, such that a remaining region exists within the composite layer that includes the PCD matrix and that is substantially free of the PCD particles. The PCD matrix includes a matrix phase of intercrystalline bonded diamond with interstitial regions dispersed therein. The PCD particles are not disposed within the interstitial regions of the PCD material forming the surrounding PCD matrix, but rather are surrounded by the PCD material in the surrounding PCD matrix (such that both the PCD matrix and its related interstitial regions are displaced by and disposed around the PCD particles).

[0029] Within the composite layer, the relative volume content of the PCD particles and the surrounding PCD matrix may vary depending on the diamond volume content of each of the PCD particles and the PCD matrix. In addition, the relative volume content of the PCD particles and PCD matrix may depend on the particular end-use application. In an example embodiment, the composite layer may include from about 10 to 85 volume percent PCD particles, 15 to 60 volume percent PCD particles, and 20 to 50 volume percent PCD particles. In an embodiment, the remaining volume is the surrounding PCD matrix.

[0030] Within the composite layer, the PCD particles are engineered to have a diamond volume content that may be the same or different from the diamond volume content in the surrounding PCD matrix. In an example, the PCD particles may have a diamond volume content that is from about 70 to 95 percent, 75 to 90 percent, or about 85 to 90 percent. In an example, the surrounding PCD matrix may have a diamond volume content that is from about 30 to 70 percent, or 35 to 60 percent. It is to be understood that the exact diamond volume content for the PCD particles and the surrounding PCD matrix can and will vary depending on the particular end-use application. In an example, the diamond volume content in the PCD surrounding matrix is sufficient to provide a desired hardness, which may be from about 1,800 to 3,200 HV. In an example, the PCD particles have a diamond volume content so as to provide a hardness above about 3,000 HV, and have a hardness greater than that of the surrounding PCD matrix. In an example, the PCD particles have a hardness that is at least 500 HV greater than that of the surrounding PCD matrix, and from about 750 to 1,500 HV greater than the surrounding PCD matrix.

[0031] The intermediate or transition layer includes PCD, and may include a diamond volume content that is the same or different from the diamond volume content of the PCD surrounding matrix in the composite layer. In an example, the PCD diamond volume content in the transition layer is in the range of from about 25 to 75 percent, 30 to 70 percent, or 35 to 55 percent. In an example, the diamond content of PCD in the transition layer may be less than that of the PCD surrounding matrix in the composite layer for the purpose of serving as an intermediate to help bridge the difference in the coefficients of thermal expansion between the composite layer and substrate. The transition layer may have a hardness that is the same or different from that of the surrounding PCD matrix as described above. In an example, the transition layer has a hardness that is equal to or less than that of the surrounding PCD matrix, and that may be in the range of from about 1,800 to 3,200 HV.

[0032] As noted above, diamond-bonded constructions and cutting elements as disclosed herein may include one or more transition layers depending on the particular end-use application. In an example, the cutting element may include two or more such transition layers, where each transition layer includes a different diamond volume content from one another. In an example, the transition layers may have a decreased diamond volume content moving from the composite layer to the substrate. The use of more than one transition layer can be provided for the purpose of enhancing the amount of strength or fracture toughness to the construction, and/or for the purpose of providing an enhanced degree thermal expansion matching between the composite layer and the substrate. These are but a few examples of when a number of transition layers may be useful in diamond-bonded constructions as disclosed herein.

[0033] The composite layer has a thickness sufficient to provide the desired features of the asperities along the wear surface and to do so in a manner so as to avoid the PCD particles from being prematurely expelled or otherwise pulled out during service, and to further provide a desired degree of wear resistance and abrasion resistance to yield a desired service life. The composite layer thickness can and will vary depending on such factors as the PCD particle size, the volume content of the PCD particles, the diamond volume content in the PCD particles and surrounding PCD matrix, and the particular end-use application. In an example, with reference to the dome-shaped cutting insert (as illustrated in FIGS. 1 and 2), the composite layer has a thickness of from about 1 to 50 percent, 2 to 35 percent, or 5 to 25 percent of the cylindrical diameter of the PCD body or table. In an example, the composite layer thickness is from about 0.75 to 2 mm. [0034] The transition layer has a thickness sufficient to provide a desired degree of strength, fracture toughness, and or thermal expansion matching to the diamond-bonded construction as disclosed above. The transition layer thickness can and will vary depending on such factors as the makeup of the composite layer and the substrate, and the particular end-use application. In an example, with reference to the dome-shaped cutting insert (as illustrated in FIGS. 1 and 2), the transition layer has a thickness of from about 0.5 to 50 percent, 1 to 30 percent, or 2 to 15 percent of the diameter of the PCD body or table. In an example, the transition layer thickness is about 0.2 to 1.5 mm.

[0035] FIG. 6 illustrates an example diamond-bonded construction provided as a cutting element in the form of a shear cutter 60, where the shear cutter 60 includes a PCD body 62 attached to a substrate 64. As contrasted with the cutting insert illustrated in FIGS. 1 and 2 above, the shear cutter 60 has a wear surface 66 disposed along a top portion of the cutter that is generally flat or planar. The shear cutter wear surface may include all or at least a portion of a side surface 68 of the PCD body.

[0036] FIG. 7 better illustrates that the PCD body 72 of the shear cutter 70 includes a composite layer 74 and a transition layer 82 that is interposed between the composite layer 74 and a substrate 84. The composite layer 74 includes the same material makeup as described above for the cutting insert (illustrated in FIGS. 1 to 4); namely, including a plurality of PCD particles 76 that are dispersed within a surrounding PCD matrix 78, and where the PCD particles positioned adjacent the wear surface 79 form asperities 80 that project a distance outwardly from the wear surface 79. The PCD particles have the same properties as described earlier, and form asperities having the same properties as described earlier. The composite layer and the transition layer have the same properties as they relate to diamond volume content, PCD volume content, and hardness as described above. The thickness of the composite layer in this example may be from about 1 to 5 mm, 1.5 to 4 mm, or 2 to 3 mm. The thickness of the transition layer in this example may be from about 0.2 to 2 mm, 0.4 to 1.5 mm, or 0.5 to 1 mm. As with the cutting insert example, shear cutters as disclosed herein may have multiple transition layers for the same reasons described above. [0037] Diamond-bonded constructions as disclosed herein may be formed in the following manner. In an example, the PCD particles may be provided in postsintered or already-sintered form in the desired size, that are then combined with precursor diamond grains useful for forming the surrounding PCD matrix in the composite layer under HPHT conditions.

Alternatively, the PCD particles may be provided as green-state granules or the like including precursor diamond grains that are held together by a suitable binder, where such green-state granules are then combined with precursor diamond grains useful for forming the surrounding PCD matrix in the composite layer, and where the green-state granules and the surrounding diamond grains are both sintered under HPHT conditions, i.e., the PCD particles are formed in situ with the surrounding PCD matrix during one or more HPHT process conditions in the presence of one or more catalyst material, where the catalyst material may be provided in powder form along with the diamond grains used for forming the PCD particles and surrounding PCD matrix in the composite layer, or may be provided by infiltration during HPHT processing from an adjacent volume of diamond grains and catalyst used to form the transition layer, or may be provided by infiltration during HPHT processing from an adjacent substrate including a catalyst material constituent, or may be provided by a combination of these methods.

[0038] Suitable catalyst materials useful for forming the PCD particles, PCD matrix, and PCD transition layer include cobalt, nickel, iron, silicon combinations thereof and those metals identified in Group VIII of the Periodic table (CAS version in the CRC Handbook of Chemistry and Physics 75th edition, front cover). Substrates useful for forming the PCD construction can be selected from the same general types of materials conventionally used to form substrates for conventional PCD materials, including carbides, nitrides, carbonitrides, ceramic materials, metallic materials, cermet materials and mixtures thereof. The substrate may include a solvent metal catalyst capable of melting and infiltrating into the adjacent volume of diamond powder to facilitate diamond-to-diamond intercrystalline bonding during HPHT processing to form/sinter the diamond grains in one or both of the composite layer and transition layer. An example substrate material is cemented tungsten carbide (WC-Co). [0039] The PCD particles, surrounding PCD matrix, and the PCD in the transition layer can be formed by combining natural or synthetic diamond grains or powder having an average diameter grain size that ranges from submicrometer to about 100 micrometers, and preferably in the range of from about 1 to 50 micrometers. In an example, the PCD particles are formed using diamond grains having an average grain size of from about 2 to 50 microns, 4 to 45 microns, or 10 to 35 microns. The diamond grain size useful for forming the surrounding PCD matrix in the composite layer may be in the range of from about 0.1 to 100 microns, 1 to 70 microns, or from about 5 to 50 microns. The diamond grain size useful for forming the transition layer may be in the range of from about 0.1 to 100 microns, 1 to 70 microns, or from about 5 to 50 microns. In an example, the diamond grains used to form the PCD particles may be sized differently from that used to form the surrounding PCD matrix, and the diamond grains used to form the transition layer may be sized differently from that used to form the surrounding PCD matrix. In an example, the diamond grains used to form the PCD particles may be finer than those used to form the surrounding PCD matrix. In an example, the diamond grains used to form the transition layer may be coarser than the diamond grains used to form the surrounding PCD matrix.

[0040] As noted above, a feature of diamond-bonded constructions of this invention is the presence of the composite layer and the PCD particles dispersed within the surrounding PCD matrix region 20 for the purpose of providing the asperities along the PCD table working surface. The PCD particles can be formed as a consolidated or sintered part separately from the formation of the surrounding PCD matrix, or can be provided as a green-state unconsolidated or unsintered part that is subsequently consolidated or sintered in situ during sintering of the surrounding PCD matrix.

[0041] In example, the composite layer and the one or more intermediate or transition layers may be formed or sintered together by conventional manner for making PCD, such as by a HPHT sintering of precursor diamond grains to create intercrystalline bonding between the diamond grains. Examples of HPHT processes useful for sintering the PCD in the composite and one or more transition layers can be found, for example, in U.S. Pat. Nos. 4,694,918; 5,370,195; and 4,525,178, which are herein incorporated by reference. Briefly, to form the composite layer and one or more transition layers, a volume of diamond grains useful for forming the one or more transition layers are sequentially loaded with a metal enclosure of a reaction cell of a HPHT apparatus. In one example, the composite layer is disposed above the transition layer and may be provided in the form of presintered PCD particles dispersed within a volume of diamond grains. A metallic substrate may be positioned adjacent the volume of diamond grains used for forming the transition layer, and the reaction cell is then placed under temperature and pressure processing conditions sufficient to cause the intercrystalline bonding between the volumes of diamond grains in the composite layer and one or more transition layers. In an example, PCD constructions as disclosed herein are formed by subjecting precursor diamond grains or powder (in the composite and one or more transition layers) to HPHT sintering conditions in the presence of a catalyst material, e.g., a solvent metal catalyst, that functions to facilitate the direct bonding together of the diamond grains at temperatures of between about 1,350 to 1,500°C, and pressures of 5,000 MPa or higher.

[0042] A suitable HPHT apparatus for this process is described in U.S. Pat. Nos. 2,947,611; 2,941,241; 2,941,248; 3,609,818; 3,767,371; 4,289,503; 4,673,414; and 4,954,139, which are incorporated herein by reference. A catalyst material, such as that disclosed above, may be provided in the form of powder in a mixture with the diamond grains used to form one or both of the composite and transition layers in an amount sufficient to provide a complete sintering of the diamond grains disposed therein. Alternatively, or in addition to catalyst material provided in powder form, the substrate may include a catalyst constituent, e.g., when the catalyst is formed from cemented tungsten carbide (WC-Co) or the like that includes cobalt, that infiltrates into the diamond volume during HPHT processing to provide or assist with the sintering process and bonding together of the diamond grains.

If the PCD particles are provided in the form of an unsintered "green state" granule or the like that is to be sintered in situ during the same process as sintering the surrounding PCD matrix forming the composite layer and the PCD material forming the one or more transition layers, then the HPHT processing conditions can be controlled, e.g., to provide a two-stage sintering process where the temperature or pressure is adjusted during sintering, if it is desired to permit consolidation and sintering of the PCD particles prior to the consolidation and sintering of the remaining volumes of diamond grains making up the surrounding PCD matrix in the composite layer and the PCD in the one or more transition layers.

[0043] In an example, the PCD particles can be sintered first during such two-stage HPHT process by using a catalyst material having a lower melting temperature to form the green state granules than a catalyst material selected to form the remaining PCD materials. For example, the catalyst material used to form the green state granules in such embodiment may be silicon, and the catalyst material used to form the remaining PCD materials may be cobalt, where silicon has a lower melting temperature than cobalt, which may operate to facilitate sintering the PCD particles during a first HPHT condition that is at a temperature sufficient to cause the silicon to melt but below the melting temperature of cobalt. Once the PCD particles have been sintered, e.g., the first HPHT condition is maintained at the first temperature for a period of time, the HPHT condition is controlled to adjust the temperature to the melting temperature of cobalt which then facilitates the sintering of the remaining diamond grains in the composite and transition layers to facilitate PCD formation in each of such respective layers.

[0044] It is to be understood that the exact pressures and temperatures used during such HPHT processing, to achieve the sequential sintering noted above, can and will vary depending on such factors as the particular choice of materials that are used for forming the green-state granules and precursor mixture used to form the surrounding PCD matrix and the PCD material in the one or more transition layers, as well as the type of device that is used to perform the HPHT process. During the second HPHT condition, because the granules have already been consolidated and sintered to form the PCD particles, the binder or catalyst material that is now melted will infiltrate into the diamond grains in the precursor mixture used to form the remaining PCD material in the composite layer and one or more transition layers. It is believed that during this second HPHT condition, the binder or catalyst material in such precursor mixture will not infiltrate the already sintered PCD particles.

[0045] In an example where the PCD particles are provided in form of green state granules for sintering, such granules can be formed as described in U.S. Patent Publication No.

2002/0194955, which is herein incorporated by reference. In such example, the diamond granules can be prepared by blending synthetic diamond powder with a polymer binder and a binder or catalyst material, and pelletizing or otherwise shaping the diamond and polymer mix into small diamond pellets or granules. If desired, the resulting green-state diamond granules can be optionally coated with a material, such as one that can act as a barrier to prevent the infiltration of the binder or catalyst material from the surrounding precursor materials used to form the polycrystalline diamond region during HPHT processing. Such green-state diamond granules can be coated with a metal and/or cermet material.

[0046] In another example, described by U.S. Patent Publication No. 2002/0194955, the green- state granules can be prepared by taking a diamond precursor material (formed from diamond powder, an organic binder, and binder metal), and granulating the diamond precursor material. The resulting granules can be optionally treated or coated with those materials noted above, e.g., with a desired barrier material, metal, or cermet. Suitable diamond precursor materials include diamond tape that is formed by combining synthetic diamond powder with a binder material, e.g., cobalt, and an organic binder, and forming the combined mixture into a desired sheet or web. Diamond powder and binder metal powder can be the same as that described above for forming green-state diamond granules as noted above. The green-state diamond precursor can be granulated into desired size particles, e.g., a diamond precursor in the form of diamond tape is chopped into small particles, where each particle includes a combination of diamond powder, metal binder powder, and organic binder. If desired, the so-formed granulated diamond particles can optionally be coated.

[0047] The PCD particles may also be formed from a process known as "tape casting" in conjunction with high pressure/high temperature (HPHT) diamond synthesis technology, such as that described in U.S. Pat. Nos. 5,766,394 and 5,379,853, which are herein incorporated by reference in their entirety. In the tape casting process, a fine diamond powder is mixed with a temporary organic binder. This mixture is mixed and milled to the most advantageous viscosity and then cast or calendared into a sheet (tape) of a desired thickness. The tape is dried to remove water or organic solvents. The dried tape is flexible and strong enough in this state to be handled and cut into shapes as desired to be dispersed into a PCD composite layer disclosed herein. The tape pieces are initially heated in a vacuum furnace to a temperature high enough to drive off any organic binder material. The temperature is then raised to a level where the crystalline powders fuse to each other. Consolidation/sintering of the pieces may occur either prior to or post mixing with the precursor materials used to form the surrounding PCD matrix. The diamond tape and/or formed pieces may optionally include a coating to reduce/prevent formed pieces from sticking and sintering together.

[0048] Accordingly, in addition to the PCD particles having a potentially different hardness and/or diamond volume content and/or be formed from differently sized diamond grains than that of the surrounding PCD matrix in the composite layer, the PCD particles may also include a catalyst material that is different from that of the surrounding PCD matrix. In an example, where the PCD particles are formed using a silicon catalyst as noted above, the presence of such catalyst material within the interstitial regions of the PCD particles may operate to provide an enhanced degree of thermal stability to the PCD particles, as silicon or silicon carbide is known to not graphitize at elevated temperatures above about 750°C, which operates to promote the stability of the PCD particles during operation at such temperatures that may be desired in certain end-use applications calling for an enhanced degree of thermal stability along the cutting element wear surface. Additionally, the catalyst material selected to form the PCD particles can be ones, e.g., such as silicon, having a CTE that more closely matches diamond when compared to cobalt to thereby operate to resist cracks that may occur in the diamond lattice structure of the PCD particles and that are known to result in deterioration of the PCD.

[0049] As noted above, the PCD particles may be formed using a binder or catalyst material that is different from that used to form the surrounding PCD matrix. In an example embodiment, the binder or catalyst material used to form the PCD particles can be one having a CTE that is closer to diamond than that of conventional solvent metal catalyst material such as cobalt or the like. Examples of such binder or catalyst materials include silicon or silicon carbide. During the manufacturing process, a large portion, 80 to 100 volume percent, of the silicon reacts with carbon in the diamond lattice to form silicon carbide which also has a thermal expansion similar to diamond. Upon heating, any remaining silicon, silicon carbide, and the diamond lattice will expand at more similar rates as compared to rates of expansion for cobalt and diamond, resulting in a more thermally stable material. PCD particles formed by using silicon and/or silicon carbide may have thermal stability and low wear rates even as temperatures reach 1,200°C. U.S. Patent Publication No. 2005/0230156, which is herein incorporated by reference, describes

polycrystalline diamond composites made with a silicon getter material that may also be used in the PCD constructions disclosed herein.

[0050] PCD constructions formed by using PCD particles as provided in a post-sintered state for forming the PCD composite layer may have an exterior surface that is optionally treated, e.g., by coating with a barrier material or the like, to ensure that the solvent catalyst material used to form the surrounding PCD matrix in the composite layer does not infiltrate into the PCD particles during HPHT processing. Examples of suitable materials useful as barrier materials can include ceramic materials, refractory metals, and/or materials that would not have a catalytic impact on the polycrystalline material in the discrete region at sintering and/or end-use operating temperatures.

[0051] The combined PCD particles (postsintered or in a green state), mixture of diamond grains useful for forming the surrounding PCD matrix in the composite layer, the mixture of diamond grains useful for forming PCD in the one or more transition layers, and the metallic substrate are assembled together and loaded into a container that is placed into an HPHT device, and the device is operated to impose a desired HPHT condition onto the contents of the container that is calculated to sinter the precursor mixture and optionally join the resulting PCD body or table to the substrate, thereby resulting in the formation of a cutting element including the PCD construction.

[0052] Accordingly, in the example noted above where silicon is used to form the PCD particles, the so-formed PCD particle includes silicon that may exist interstitially between the bonded together diamond crystals, and/or that may react with carbon in the diamond to form silicon carbide that may also reside in interstitially within the bonded together diamond crystals or that may operate to bond the diamond crystals together as a reaction product. Thus, the PCD particles formed using silicon may include silicon carbide as a reaction product operating to bond together diamond crystals, thereby providing an added level of structural stability to the PCD particle. [0053] In an example where PCD particles used to form the PCD construction are provided in post-sintered form for making the composite layer by HPHT process, such PCD particles may be prepared by sintering under significantly higher pressure and/or higher temperature conditions than those subsequently used during the HPHT process to consolidate and sinter the precursor mixture to form the surrounding PCD matrix, which may assist in providing PCD particles having a high diamond volume content or density and/or relatively higher thermal stability than that of the surrounding PCD matrix.

[0054] PCD constructions and cutting elements as disclosed herein may be engineered and configured for use in variety of wear operations, such as tools for mining, cutting, machining, and construction applications, which the combined properties of thermal stability, wear, and abrasion resistance are desired. PCD cutting elements as disclosed herein may be used in machine tools and drill bits, such as fixed cutter bits, roller cone rock bits, percussion or hammer bits, and diamond bits.

[0055] FIG. 8 illustrates a rotary or roller cone drill bit in the form of a rock bit 90 including a number of the PCD wear or cutting inserts 92 disclosed above and illustrated in FIGS. 1 and 2. The rock bit 90 includes a body 94 having three legs 96 extending therefrom, and a roller cutter cone 98 mounted on a lower end of each leg. The cutting inserts 92 are the same as those described above including the PCD constructions of this invention having the plurality of asperities projecting along the cutting element wear surface, and are projecting outwardly from the surfaces of each cutter cone 98 for engaging and bearing on a rock formation being drilled.

[0056] FIG. 9 illustrates a percussion or hammer bit 100 including a number of the PCD cutting inserts 102 as described above and illustrated in FIGS. 1 and 2. The hammer bit 100 generally includes a hollow steel body 104 having a threaded pin 106 on an end of the body for assembling the bit onto a drill string (not shown) for drilling oil wells and the like. A plurality of the PCD cutting inserts 102 are attached to and projecting outwardly from a surface of a head 108 of the body 104 for engaging and bearing on the subterranean formation being drilled.

[0057] FIG. 10 illustrates a drag bit 120 including a plurality of the PCD cutting elements in the form a shear cutter 122 as described above and illustrated in FIG. 5. The shear cutters 122 are each attached to blades 124 that extend outwardly from a head 126 of the drag bit for cutting against the subterranean formation being drilled. Because the PCD shear cutters of this invention include a metallic substrate, they are attached to the blades by conventional method, such as by brazing or welding or the like.

[0058] A feature of PCD constructions and cutting elements formed therefrom as disclosed herein is that they include PCD composite layer that has been developed to include a plurality of PCD particles that are specially engineered to provide a wear surface including a plurality of asperities projecting outwardly therefrom. For example, the asperities may project outwardly a distance from the surface of the composite layer and be sized so that, when placed into a drilling application, the asperities operate to break earthen formations into relatively larger sized pieces, minimizing the formation of fine cuttings and powder and enhancing the operation of crushing and gouging by creating secondary fractures in the earthen formation to increase drilling efficiency. Additionally, such PCD particles in the PCD constructions as disclosed herein may be engineered to provide a greater degree of thermal stability, hardness, wear resistance, and/or abrasion resistance than that of the surrounding PCD region to increase cutting element service life.

[0059] Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from the concepts as disclosed herein. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words 'means for' together with an associated function.

Claims

What is Claimed is:

1. A diamond-bonded construction comprising:

a polycrystallme diamond body comprising:

a composite layer comprising a plurality of polycrystallme diamond particles dispersed in a polycrystallme diamond matrix phase, wherein the polycrystallme diamond particles have an average particle size of between 50 to 1,000 micrometers, wherein the composite layer extends inwardly a partial depth from a wear surface of the body and comprises a plurality of asperities projecting outwardly from the wear surface that are formed from the polycrystallme diamond particles; and

a transition layer disposed beneath the composite layer that comprises

polycrystallme diamond and that is substantially free of the polycrystallme diamond particles, wherein the volume percent of polycrystallme diamond in the transition layer is different from the volume percent of

polycrystallme diamond in the composite layer; and a metallic substrate attached to the polycrystallme diamond body.

2. The construction as recited in claim 1 wherein the composite layer has a thickness from 1 to 50 percent of a diameter of the polycrystallme diamond body.

3. The construction as recited in claim 1 wherein the composite layer has a thickness from 0.75 to 2 mm, and the transition layer has a thickness from 0.2 to 1.5 mm.

4. The construction as recited in claim 1 wherein the volume percent of polycrystallme diamond in the transition layer is less than the volume percent of polycrystallme diamond in the polycrystallme diamond matrix phase of the composite layer.

5. The construction as recited in claim 1 comprising a further transition layer between the transition layer and the metallic substrate, wherein the volume percent of polycrystallme diamond in the further transition layer is different from the volume percent of

polycrystalline diamond in the transition layer.

6. The construction as recited in claim 1 wherein the composite layer comprises from 10 to 85 volume percent of the polycrystalline diamond particles based on the total volume of the composite layer.

7. The construction as recited in claim 1 wherein diamond grains used to form the

polycrystalline diamond matrix phase of the composite layer have an average particle size that is different from the average particle size of the diamond grains used to form the polycrystalline diamond of the transition layer.

8. The construction as recited in claim 1 wherein the plurality of asperities project an

average distance from the wear surface, and wherein the average distance is from 20 to 60 percent of the average particle diameter of the polycrystalline diamond particles.

9. The construction as recited in claim 1 wherein the plurality of asperities project an

average distance from a wear surface, and wherein the average distance is from 30 to 210 microns.

10. The construction as recited in claim 1 wherein the asperities have an average width

measured at the wear surface that is from 20 to 100 percent of the average particle diameter of the polycrystalline diamond particles.

11. The construction as recited in claim 1 wherein the asperities cause a rock formation in contact therewith to be broken into pieces, wherein greater than 75 percent of such pieces are sized from 0.2 to 2 mm.

12. The construction as recited in claim 1 wherein the composite layer matrix phase has a hardness in the range of 1,800 to 3,200 HV, the polycrystalline diamond particles have a hardness above 3,000 HV, and the polycrystalline diamond particles have a hardness that is at least 500 HV higher than the hardness of the polycrystalline matrix phase.

13. The construction as recited in claim 1 wherein the transition layer has a hardness in the range of 1,800 to 3,200 HV, and the transition layer has a hardness equal to or less than the hardness of the composite layer.

14. A bit for drilling subterranean formations comprising a body and a number of cutting elements connected thereto, wherein one or more of the cutting elements comprises the diamond-bonded construction as recited in claim 1.

15. A cutting element comprising:

a diamond-bonded composite layer having a thickness that extends a depth from an outer surface of the cutting element, the composite layer comprising a plurality of polycrystalline diamond particles dispersed within a surrounding polycrystalline diamond matrix, wherein the hardness of the polycrystalline diamond particles is greater than the hardness of the polycrystalline diamond matrix;

an intermediate layer disposed beneath the diamond-bonded composite layer, wherein the intermediate layer comprises polycrystalline diamond and is substantially free of the polycrystalline diamond particles, the intermediate layer having a volume percent of polycrystalline diamond that is less than the volume percent of polycrystalline diamond in the composite layer; and

a metallic substrate coupled to the intermediate layer;

wherein the cutting element comprises a plurality of asperities projecting outwardly a distance from the outer surface, wherein the asperities are formed from the polycrystalline diamond particles, wherein the distance is 20 to 60 percent of the average diameter of the polycrystalline diamond particles, and wherein the asperities have an average diameter at the outer surface that is from 20 to 100 percent of the average diameter of the polycrystalline diamond particles.

16. The cutting element as recited in claim 15 wherein the diamond-bonded composite layer comprises from 10 to 85 volume percent polycrystalline diamond particles based on the total volume of the diamond-bonded composite layer, and wherein the volume percent polycrystalline diamond in the polycrystalline diamond particles is greater than the volume percent of the polycrystalline diamond in the polycrystalline diamond matrix.

17. The cutting element as recited in claim 15 wherein the composite layer has a thickness of from 0.75 to 2 mm, and wherein the intermediate layer has a thickness of from 0.2 to 1.5 mm.

18. The cutting element as recited in claim 15 wherein the plurality of asperities cause rocks contacted therewith to be broken into pieces, and wherein 75 percent of the pieces are sized from 0.2 to 2 mm.

19. A method for making a diamond-bonded cutting element, the method comprising:

combining a volume of polycrystalline diamond particles with a volume of diamond grains to form a composite layer, wherein the polycrystalline diamond particles have an average particle diameter from 150 to 350 microns;

combining a volume of diamond grains adjacent the composite layer to form an

intermediate layer;

placing a metallic substrate adjacent the intermediate layer to form an assembly; and subjecting the assembly to high pressure/high temperature conditions to form the cutting element, wherein the high pressure/high temperature conditions sinter the diamond grains in each of the composite layer and the intermediate layer, and wherein the high temperature/high pressure conditions attach the metallic substrate to the intermediate layer,

wherein the cutting element comprises a plurality of asperities formed from the

polycrystalline diamond particles and disposed along a wear surface of the composite layer, and wherein the asperities project outwardly a distance from the wear surface that is from 20 to 60 percent of the average particle diameter of the polycrystalline diamond particles.

20. The method as recited in claim 19, wherein the asperities have a diameter at the wear surface that is from 20 to 100 percent of the average particle diameter of the

polycrystalline diamond particles, and wherein the asperities cause rock placed into contact therewith to be broken into pieces, and wherein 75 percent or more of the pieces are sized from 0.2 to 2 mm.