Claims
- 1. The process of pretreating a hard metal or cemented carbide substrate for the reception of wear resistant oxide coatings, said substrate being provided with a surface layer of a carbide, a nitride or a carbonitride of titanium, zirconium, hafnium, vanadium, columbium, tantalum, chromium, molybdenum, or tungsten, said method comprising:
- (a) treating the substrate and surface layer in a first atmosphere selected from carbide and oxycarbide forming atmospheres to form a bonding layer of metal selected from at least one of tantalum, niobium or vanadium on said substrate; and
- (b) heating the coated substrate of (a) in a second, oxidizing atmosphere until at least portions of the surface are oxidized,
- which steps (a) and (b) are carried out in a coating furnace held at a temperature of from about 800.degree. C. to 1300.degree. C.
- 2. A process as defined in claim 1 including the step of treating the oxidized coated substrate of (b) in a reducing atmosphere with a reducible aluminum compound to diffuse aluminum into the coating.
- 3. A process as defined in claim 1 including the step of superimposing an oxide wear layer on the surface-oxidized coated substrate.
- 4. A process as defined in claim 2 including the step of superimposing an oxide wear layer on the surface-oxidized, aluminum-containing coated substrate.
- 5. A process as defined in claim 1 wherein said substrate is a cemented carbide substrate, said surface layer is titanium carbide and the bonding layer is 0.1 to 0.5 microns thick.
- 6. A process as defined in claim 3 wherein said oxide wear layer is an aluminum oxide wear layer.
- 7. A process as defined in claim 4 wherein said oxide wear layer is an aluminum oxide wear layer.
- 8. A process as defined in claim 1 including the step of metallizing said bonding layer with a metal selected from iron, cobalt, nickel or a mixture thereof.
- 9. A process for applying wear layers on a hard metal or cemented carbide substrate, said substrate being provided with a surface layer of a carbide, nitride or carbonitride of a metal selected from titanium, zirconium, hafnium, vanadium, columbium, tantalum, chromium, molybdenum, or tungsten, said process comprising the following sequential steps, carried out in a coating furnace held at a temperature of about 800.degree. to 1300.degree. C.:
- (a) exposing said carbide-, nitride-, or carbonitride-coated substrate to a gaseous mixture comprising H.sub.2 and 0.5 to 20 volume percent TaCl.sub.5 or NbCl.sub.5 for 5-60 minutes, until a bonding layer is formed on said substrate; and
- (b) exposing the substrate of (a) to a gaseous mixture comprising H.sub.2 and about 1 to 50 volume percent CO.sub.2 for 1-60 minutes, until at least portions of said bonding layer are oxidized.
- 10. The process of claim 9, wherein step (a) is carried out at 1050.degree. C., and step (b) is carried out at 1100.degree. C.
- 11. The process of claim 9, wherein the gaseous mixture of step (a) also includes TiCl.sub.4 and CH.sub.4, for at least part of the 5-60 minutes of exposure time.
- 12. The process of claim 9, which includes the further step, after step (b),
- (c) aluminizing the substrate of (b) by exposing it to a gaseous mixture comprising H.sub.2 and about 0.5 to 20 volume percent AlCl.sub.3 for 5-60 minutes.
- 13. The process of claim 12, which includes the further step, after step (c),
- (d) exposing the substrate of (c) to a gaseous mixture comprising H.sub.2, 2.5 to 20 volume percent AlCl.sub.3, and 1 to 40 or 60 to 95 volume percent CO.sub.2 for 15-240 minutes, until an aluminum oxide wear layer is deposited.
- 14. The process of claim 13, wherein steps (c) and (d) are carried out at a temperature of 1050.degree. C.
- 15. A process for producing a firmly adherent aluminum oxide wear coating on a TiC-coated cemented carbide substrate comprising the following sequential steps, carried out in a furnace held at a temperature of 1050.degree. C.:
- (a) exposing the TiC-coated cemented carbide substrate to an atmosphere of H.sub.2 and approximately 2 volume percent TiCl.sub.4 for 2 minutes,
- (b) adding to said temperature NbCl.sub.5 vapor for about 26 minutes,
- (c) exposing the substrate to an atmosphere of H.sub.2 and 3.5 volume percent CO.sub.2 for 1 minute,
- (d) exposing the substrate to an atmosphere of H.sub.2 and 5 volume percent AlCl.sub.3 for 10 minutes, and
- (e) exposing the substrate to an atmosphere of H.sub.2, 5 volume percent AlCl.sub.3 and 7 volume percent CO.sub.2 for 60 minutes.
- 16. The process of claim 15, wherein iron is applied to the TiC-coated cemented carbide substrate before step (a).
Parent Case Info
This is a divisional of U.S. application Ser. No. 573,867, filed Jan. 25, 1984, now U.S. Pat. No. 4,501,786, which is a continuation of Ser. No. 331,367, filed Dec. 16, 1981, now abandoned.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
4018631 |
Hale |
Apr 1977 |
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4239536 |
Yamamoto et al. |
Dec 1980 |
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4357382 |
Lambert et al. |
Nov 1982 |
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Divisions (1)
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Number |
Date |
Country |
Parent |
573867 |
Jan 1984 |
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Continuations (1)
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Number |
Date |
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Parent |
331367 |
Dec 1981 |
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