WO1994023090A1 - Procede de formation d'une couche dure sur un substrat - Google Patents

Procede de formation d'une couche dure sur un substrat Download PDF

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Publication number
WO1994023090A1
WO1994023090A1 PCT/GB1994/000697 GB9400697W WO9423090A1 WO 1994023090 A1 WO1994023090 A1 WO 1994023090A1 GB 9400697 W GB9400697 W GB 9400697W WO 9423090 A1 WO9423090 A1 WO 9423090A1
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WO
WIPO (PCT)
Prior art keywords
substrate
mop
boron nitride
particles
layer
Prior art date
Application number
PCT/GB1994/000697
Other languages
English (en)
Inventor
Roger John Wedlake
Aart Jurriaanse
Original Assignee
Roger John Wedlake
Aart Jurriaanse
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 Roger John Wedlake, Aart Jurriaanse filed Critical Roger John Wedlake
Priority to AU63826/94A priority Critical patent/AU6382694A/en
Publication of WO1994023090A1 publication Critical patent/WO1994023090A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas

Definitions

  • This invention relates to a method of forming a hard layer on a substrate, and to substrates coated in accordance with the method.
  • a method of forming a hard layer on a substrate comprises:
  • the particles are preferably particles of cubic boron nitride (CBN).
  • the boron nitride particles are preferably less than 100 microns in size, and more preferably less than 10 microns in size.
  • the particles are preferably rubbed across the substrate at a linear speed of at least 100 m/s, and preferably at least 200 m/s.
  • the speed may be substantially higher, up to about 360 m/s or more.
  • the substrate may comprise, for example, a metal such as steel or stainless steel, a carbide, a hard metal, a ceramic, or glass.
  • the particles may be rubbed across the surface of the substrate by means of a rotating wheel or mop, the particles being applied to the mop or to the interface between the mop and the surface of the substrate.
  • the mop may be impregnated with the particles, or the particles may be directed at the interface between the mop and the surface of the substrate by a gas or liquid jet, or both.
  • the interference between the periphery of the mop and the surface of the substrate is less than about 200 ⁇ m.
  • the mop and the substrate are preferably moved back and forth repeatedly relative to one another.
  • the invention extends to articles comprising a substrate having a boron nitride layer formed thereon by the method of the invention.
  • Figure 1 is a simplified schematic end view of an apparatus for carrying out the method of the invention
  • Figure 2 is a schematic side view of the apparatus of Figure 1, showing one method of carrying out the invention
  • Figure 3 is a schematic side view of the apparatus of Figure 1 illustrating a different method of carrying out the invention
  • Figure 4 is a schematic sectional side view (not to scale) of a portion of a substrate coated with a boron nitride layer according to a method of the invention
  • Figure 5 is a schematic illustration of a practical apparatus for carrying out the method of the invention.
  • Figure 6 is a depth profile of a sample coating produced by the method of the invention.
  • Figure 7 is an optical micrograph of a wear track on the sample coating.
  • FIG. 1 illustrates in a simplified schematic form apparatus which can be used to carry out the method of the invention.
  • the apparatus comprises a "mop" in the form of a cloth wheel or composite buffing wheel 10 which is supported on one side by a high speed bearing 12 and which is arranged to be rotated at high speed by a motor 14.
  • the motor 14 is preferably an air bearing turbine motor driven by compressed air which is designed for rotation at very high speeds, typically between 10 000 and 50 000 rpm or even higher speeds.
  • the axis of the mop 10 is horizontal, and the periphery of the wheel is supported just above the surface 16 of a table or other supporting surface. Fixed to the surface 16 is a substrate 18 which is to be coated with a boron nitride layer.
  • the substrate 18 will typically have a planar upper surface and may comprise, for example, steel or stainless steel, a carbide, a hard metal, a ceramic, or glass.
  • the substrate 18 could have a curved surface.
  • the method of the apparatus is also expected to work with other substrate materials.
  • the mop 10 is used to rub boron nitride particles 20 very rapidly and under pressure across the surface of the substrate 18, resulting in a "smearing" effect, which causes the boron nitride particles to bond to the surface of the substrate and to build up a boron nitride layer on the surface of the substrate.
  • the periphery of the mop 10 is impregnated or coated with fine boron nitride particles, and the mop is then rotated at high speed while in contact with the surface of the substrate 18. This causes the boron nitride particles to be rubbed across the surface of the substrate.
  • the linear speed at which the particles are rubbed across the surface of the substrate is proportional to the speed of rotation of the mop 10 and the radius of the mop, in accordance with the following equation:
  • the linear speed at which the boron nitride particles are rubbed across the surface of the substrate 18 will be approximately 160 m/s.
  • a typical speed of rotation is 25 000 rpm, corresponding to a linear speed of approximately 200 m/s.
  • Speeds of up to 45 000 rpm are envisaged, corresponding to a linear speed of approximately 360 m/s.
  • boron nitride particles will tend to be scattered from the periphery of the mop 10 as it rotates.
  • a fine nozzle 24 is used to direct a thin spray of boron nitride particles 20 into the interface between the periphery of the mop 10 and the surface of the substrate 18, using air or gas pressure. This minimises wastage of the boron nitride particles.
  • a jet of liquid can be used for this purpose.
  • the mop can be impregnated initially with the sprayed particles, with the spray being continued as the coating process progresses.
  • FIG 3 an alternative method is shown.
  • a conduit 26 feeds the boron nitride particles 20 under pressure into the hub 28 of the mop 10, which is perforated, allowing the boron nitride particles 20 to migrate outwardly through the material of the mop 10.
  • This method provides a relatively uniform distribution of boron nitride particles at the periphery of the mop 10.
  • the boron nitride particles are preferably less than 100 microns in size, and more preferably less than 10 microns in size.
  • the boron nitride particles used in the experiments described below were synthetic cubic boron nitride grit particles.
  • the mop 10 was a carbon fibre/epoxy composite mop manufactured from multiple circular woven fibre mat sections.
  • the inner portions of the mops are impregnated with epoxy resin, leaving a peripheral zone of approximately 15 mm width free of resin.
  • the fibre mats are laid down one on top of the other in a staggered arrangement and moulded by conventional techniques to form a mop of approximately 300 mm diameter and approximately 5 mm thickness.
  • After curing of the epoxy resin all loose fibres are removed and the free fibres at the edge of the mop are trimmed.
  • Final finishing and rounding of the mop is carried out by running it against sandpaper on the coating apparatus, and the mop is then balanced to prevent vibrations, which at high speed can damage the bearings of the apparatus.
  • the substrate 18 is supported on a substrate table 30, which is in turn mounted on a pneumatically driven platform 32.
  • the platform is mounted on a heavy machine base 34, and its movements are controlled by a control system 36, allowing the substrate table 30 and thus the substrate 18 to be driven back and forth below the mop by a pneumatic actuator.
  • Fine particles of boron nitride are supplied to the interface between the mop 10 and the substrate 18 by a powder feed system 38.
  • a shroud 40 surrounds the mop to collect surplus powder, and is connected to a powder extraction system 42 which collects surplus powder for recycling.
  • a data acquisition system 44 is also provided, which is connected to sensors in the substrate table 30. The sensors are arranged to measure both the normal force F N and the friction force F F between the mop and substrate.
  • a stainless steel substrate was used. Specimen substrates of 50 by 30 mm were cut from a 2 mm thick sheet and were polished to a surface finish of approximately 0.02 ⁇ m Ra, giving a substantially mirror-like finish. A polished surface was preferred for experimental purposes, as this was useful in subsequent examination and characterisation of the layer formed by the method.
  • the specimen substrate is clamped onto the substrate table of the apparatus and the height of the compressed air turbine is adjusted so that the lowermost edge of the mop 10 contacts the surface of the substrate 18 with a degree of interference.
  • an interference of approximately 100 ⁇ m was found to give good results.
  • Significantly greater interference was found to lead to damage of the substrate by the high speed mop.
  • the turbine is started and the speed of the mop 10 adjusted to approximately 15 000 rpm by regulating the compressed air flow to the turbine. With a mop of 300 mm diameter, this corresponds to a circumferential velocity at the periphery of the mop of approximately 235 m/s.
  • the powder feed system is started and cubic boron nitride (CBN) powder is fed to the interface between the mop and the substrate at a rate of approximately 20 to 30 mg/min.
  • CBN cubic boron nitride
  • De Beers Micron ABN 300 cubic boron nitride powder with a size distribution of 0 to 0.5 ⁇ m was used.
  • the pneumatic actuation and control system 36 is actuated and the substrate table 30 is driven back and forth under the mop at a speed which is much slower than the speed at which the mop rubs the particles across the substrate.
  • the substrate table was moved at a speed of approximately 0.2 m/s. A number of passes are normally required. Typically, 10 back and forth cycles were employed.
  • the data acquisition system 44 records the normal and friction forces between the mop and the substrate. In the above prototype method, normal forces of 8 to 12 N and friction forces of 4 to 8 N were measured.
  • the coatings obtained by the above described method were subjected to examination by TEM, SEM and optical microscopy, and XPS and AES analysis techniques. Pin-on disc wear tests, using a tungsten carbide- cobalt ball sliding on the coated surface were also performed.
  • CBN coatings Microscopic examination of the CBN coatings showed them to be continuous, with a flecked appearance and a wavy surface (see Figure 7). Both XPS and AES analysis of the coatings have shown that they contain primarily boron, nitrogen (CBN) and carbon.
  • the coating is composed of CBN particles in a matrix consisting of metal oxides and possibly carbides (originating from the original steel surface), with carbon introduced from the carbon fibre mop. In a TEM examination of the coating, CBN particles with an average size of less then 100 nm were identified in the matrix.
  • a concentration depth profile, using an Argon sputtering technique in an Auger spectrometer on a CBN coating generated by ten passes under the mop is shown in Figure 6.
  • the time required to sputter through the tested coating indicated that its thickness was approximately 0.3 ⁇ m.
  • the hardness (or softness) of the mop 10 has a significant influence on the effect obtained in carrying out the method.
  • the substrate is eroded until a boron nitride layer begins to form.
  • the erosion of the substrate results in the appearance of striations in the resulting boron nitride layer.
  • the force applied by the mop to the substrate also has an influence on the rate of boron nitride formation on the substrate.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Laminated Bodies (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)

Abstract

Procédé de formation d'une couche dure sur un substrat (18) consistant à frotter des particules de nitrure de bore (20) contre la surface du substrat à une vitesse élevée et sous une pression suffisamment élevée pour faire adhérer une couche de nitrure de bore sur la surface. Une meule en fibres de carbone (10) tournant à une vitesse d'environ 15 000 tr/mn est maintenue contre un substrat tel que de l'acier inoxydable poli, avec une légère force de contact entre la meule et le substrat. Les particules de nitrure de bore cubique, dont la distribution granulométrique se situe entre zéro et 0,5 microns, sont appliquées au niveau de l'interface située entre la meule et le substrat, et le substrat est entraîné d'avant en arrière lentement sous la meule, jusqu'à ce que se forme une couche de nitrure de bore sur la surface du substrat. Les couches d'essai ont permis d'obtenir une épaisseur d'environ 0,3 microns ainsi que d'excellentes caractéristiques d'usure.
PCT/GB1994/000697 1993-03-31 1994-03-31 Procede de formation d'une couche dure sur un substrat WO1994023090A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU63826/94A AU6382694A (en) 1993-03-31 1994-03-31 Method of forming a hard layer on a substrate

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9306745.2 1993-03-31
GB939306745A GB9306745D0 (en) 1993-03-31 1993-03-31 Method of forming a hard layer on a substrate

Publications (1)

Publication Number Publication Date
WO1994023090A1 true WO1994023090A1 (fr) 1994-10-13

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ID=10733101

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1994/000697 WO1994023090A1 (fr) 1993-03-31 1994-03-31 Procede de formation d'une couche dure sur un substrat

Country Status (4)

Country Link
AU (1) AU6382694A (fr)
GB (1) GB9306745D0 (fr)
WO (1) WO1994023090A1 (fr)
ZA (1) ZA942312B (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4440108A (en) * 1982-09-24 1984-04-03 Spire Corporation Ion beam coating apparatus
EP0152204A2 (fr) * 1984-01-24 1985-08-21 Tribohesion Limited Procédé de revêtement
WO1994005430A1 (fr) * 1992-09-01 1994-03-17 Erno Nagy De Nagybaczon Procede de realisation de depots de materiaux comprenant des matieres extremement dures et complexes

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4440108A (en) * 1982-09-24 1984-04-03 Spire Corporation Ion beam coating apparatus
EP0152204A2 (fr) * 1984-01-24 1985-08-21 Tribohesion Limited Procédé de revêtement
WO1994005430A1 (fr) * 1992-09-01 1994-03-17 Erno Nagy De Nagybaczon Procede de realisation de depots de materiaux comprenant des matieres extremement dures et complexes

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Week 9412, Derwent World Patents Index; AN 94-100932 *

Also Published As

Publication number Publication date
ZA942312B (en) 1995-05-02
GB9306745D0 (en) 1993-05-26
AU6382694A (en) 1994-10-24

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