Claims
- 1. A method of producing a coating resistant to at least one of wear and corrosion on a surface of a substrate made of at least one of metal and ceramic, said coating being produced from a coating material, said coating material comprising hard metallic alloys, said method comprising the steps of:
- providing a layer of powder grains of the coating material in powder form bonded together with an organic binder;
- subjecting said layer of bonded powder grains and said binder to a first heating step at a first temperature during which said binder is decomposed, whereby a rudimentary coating comprising said powder grains and decomposed binder is formed on said surface; and
- subjecting said rudimentary coating on said surface to a second heating step being conducted in conjunction with the application of isostatic super-atmospheric pressure to densify said rudimentary coating by isostatic hot pressing of said powder grains and to permanently adhere the densified rudimentary coating to said surface to form said resistant coating,
- wherein no liquid phase is produced in the layer of the powder grains during the first heating step or the second heating step.
- 2. A method as claimed in claim 1, wherein the second heating step provides solid phase sintering.
- 3. A method as claimed in claim 2 in which the process temperatures employed in the second heating step are as high as possible yet avoid the production of a liquid phase.
- 4. A method as claimed in claim 2 in which the coating material comprises by weight 6 to 25% of chromium, molybdenum, tungsten, tantalum, niobium, titanium, hafnium or zirconium, or a mixture thereof, 0 to 2% of carbon in addition to carbon from the organic binder, 0 to 5% boron, 0 to 5% silicon, 0 to 5% iron, 0 to 10% aluminum, 0 to 1% of a rare earth element, 0 to 94% particulate carbide material, the balance being nickel, cobalt or iron.
- 5. A method as claimed in claim 1 in which the organic binder comprises a long-chain hydrocarbon.
- 6. A method as claimed in claim 5 in which the binder comprises a polymer.
- 7. A method as claimed in claim 6 in which the binder comprises a vinyl polymer.
- 8. A method as claimed in claim 1 in which the layer is formed in situ on the metal substrate.
- 9. A method as claimed in claim 1 in which a mixture is produced of the organic binder, the powder material and a binder solvent, and a slip casting process is employed to apply the mixture to the substrate.
- 10. A method as claimed in claim 1 in which a plurality of superimposed layers of said coating material are applied to the substrate, the layers differing in composition.
- 11. A method as claimed in claim 1 in which the layer is produced as an independent pre-form and the pre-form is then assembled to the substrate prior to the heating steps.
- 12. A method as claimed in claim 1 in which the heating steps are performed while the substrate with said layer is mounted in a gas-tight jacket, the jacket being a close fit on the layer at least during the second heating step.
- 13. A method as claimed in claim 1 wherein carbon resulting from decomposition of the binder during the first heating step diffuses into said substrate during said second heating step.
- 14. A method as claimed in claim 1, in which said first and second heating steps are performed without an intermediate cooling step.
- 15. A method of producing a coating resistant to at least one of wear and corrosion from a coating material comprising hard metallic alloys on a surface of a substrate made of at least one of metal and ceramic, comprising:
- providing a layer of powder grains of the coating material in powder form bonded together with said organic binder on said surface;
- subjecting said layer of bonded powder grains to a first heating step during which said binder is decomposed, whereby a rudimentary coating comprising said powder grains and decomposed binder is formed on said surface; and
- subjecting said rudimentary coating on said surface to a second heating step, said second heating step being conducted in conjunction with the application of isostatic super-atmospheric pressure to densify said rudimentary coating by isostatic hot pressing of said powder grains and to permanently adhere the densified rudimentary coating to said surface to form said resistant coating, in which the coating material has substantially the following composition by weight:
- 11.85% Cr
- 2.1% B
- 2.2% Si
- 2.3% Fe
- 0.42% C
- 35% nickel clad tungsten carbide, of minimum dimensions at least 45 microns
- 46.13% Ni.
- 16. A method of producing a coating resistant to at least one of wear and corrosion on a surface of a substrate made of at least one of metal and ceramic from a coating material comprising hard metallic alloys, comprising:
- providing a layer of powder grains of the coating material in powder form bonded together with said organic binder on said surface;
- subjecting said layer of bonded powder grains to a first heating step during which said binder is decomposed, whereby a rudimentary coating comprising said powder grains and decomposed binder is formed on said surface; and
- subjecting said rudimentary coating on said surface to a second heating step, said second heating step being conducted in conjunction with the application of isostatic super-atmospheric pressure to densify said rudimentary coating by isostatic hot pressing of said powder grains and to permanently adhere the densified rudimentary coating to said surface to form said resistant coating, in which the thickness of the layer is at least 1 millimeter and wherein no liquid phase is produced in the layer during the first heating step or the second heating step.
- 17. A method as claimed in claim 16 in which the thickness of the layer is at least 5 millimeters.
- 18. A method of producing a coating resistant to at least one of wear and corrosion from coating material comprising hard metallic alloys on a surface of a substrate made of at least one metal and ceramic comprising bonding together with an organic binder the coating material in powder form to provide a layer of powder grains bonded together with said organic binder on said surface;
- enclosing said surface and said layer in a gas-tight jacket;
- subjecting said layer of bonded powder grains enclosed by said jacket to a first heating step during which said binder is decomposed, whereby a rudimentary coating comprising said powder grains and decomposed binder is formed on said surface; and
- subjecting said rudimentary coating on said surface enclosed by said jacket to a second heating step in conjunction with the application of isostatic super-atmospheric pressure to densify said rudimentary coating by isostatic hot pressing of said powder grains to permanently adhere the densified rudimentary coating to said surface to form said resistant coating,
- wherein no liquid phase is produced in the layer during the first heating step or the second heating step.
- 19. A method as claimed in claim 18 wherein said jacket is being evacuated during said first heating step.
- 20. A method as claimed 18 comprising a cooling step between said first and second heating steps.
- 21. A method as claimed in claim 18 wherein said first heating step is conducted in a furnace, and said first heating step comprises a soak period during which a super-atmospheric pressure is maintained in said furnace.
- 22. A method a claimed in claim 18 in which said pressure in said furnace during said soak period is substantially 200 bar.
Priority Claims (2)
Number |
Date |
Country |
Kind |
9010549 |
May 1990 |
GBX |
|
9027543 |
Dec 1990 |
GBX |
|
Parent Case Info
This application is a continuation of U.S. patent application Ser. No. 07/947,004, filed Sep. 18, 1992 now abandoned which is a continuation of U.S. patent application Ser. No. 07/697,882, filed May 9, 1991, now abandoned.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
3754968 |
Reznik |
Aug 1973 |
|
4351858 |
Hunold et al. |
Jul 1982 |
|
4851188 |
Schaefer et al. |
Jul 1987 |
|
Foreign Referenced Citations (1)
Number |
Date |
Country |
0005285 |
Nov 1979 |
EPX |
Continuations (2)
|
Number |
Date |
Country |
Parent |
947004 |
Sep 1992 |
|
Parent |
697882 |
May 1991 |
|