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US4250208A
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US
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Method for forming a two-layered carbide surface on a ferrous-alloy article and resulting product
Assignee: Toyota Central R&D Labs Inc
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Filing: 1979-06-12
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Granted: 1981-02-10
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Expires: 1999-06-12
Abstract
Abstract A method for forming a two-layered carbide surface on a ferrous-alloy article containing at least 0.2 percent by weight of carbon. The formation of such a surface is effected by plating the ferrous alloy article with chromium, to form a chromium layer thereon, and heating the thus-plated article in contact with an element of Group Va and/or chromium (a) to diffuse carbon from the ferrous-alloy article into the chromium layer and convert the chromium layer to an intermediate chromium-carbide layer and (b) thereafter to combine carbon in the intermediate chromium-carbide layer with the element (of Group Va or chromium) and thus form a Group-Va-element-carbide layer and/or another chromium-carbide layer on the intermediate chromium-carbide layer.
Inventors
- 👤 Tohru Arai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 01:20
CPC Classifications
C; C23; C23C; C23C12/00; C23C10/00; C23C10/02; C23C10/18; C23C10/26
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
112 words
A method for forming a two-layered carbide surface on a ferrous-alloy article containing at least 0.2 percent by weight of carbon which comprises the steps of plating the surface of the ferrous-alloy article with chromium to form a chromium-plated layer thereon, and heating the resulting plated article in a medium containing at least one element selected from the group consisting of Group-Va elements and chromium to diffuse carbon from the ferrous-alloy article into the chromium-plated layer and thus convert said chromium-plated layer into an intermediate chromium-carbide layer, and thereafter to combine diffused carbon in the intermediate chromium-carbide layer with the element to form an outer carbide layer on the intermediate chromium-carbide layer.
Claim 2
Independent Claim
112 words
A method for forming a two-layered carbide surface on a ferrous-alloy article containing at least 0.2 percent by weight of carbon which comprises the steps of plating the surface of the ferrous-alloy article with chromium to form a chromium-plated layer thereon, and heating the resulting plated article in a medium containing at least one element selected from the group consisting of Group-Va elements and chromium to diffuse carbon from the ferrous-alloy article into the chromium-plated layer and thus convert said chromium-plated layer into an intermediate chromium-carbide layer, and thereafter to combine diffused carbon in the intermediate chromium-carbide layer with the element to form an outer carbide layer on the intermediate chromium-carbide layer.
Claim 3
Dependent Claim
23 words
A method according to claim 1 wherein the thickness of said chromium-plated layer is within a range of from about 2μ to 90μ.
Claim 4
Dependent Claim
39 words
A method according to claim 1 wherein the heating is carried out for from 1 to 30 hours at a temperature within a range of from 700° C. to a point below the melting point of the ferrous-alloy article.
Claim 5
Dependent Claim
17 words
A method according to claim 3 wherein the temperature range is from 800° C. to 1,100° C.
Claim 6
Dependent Claim
53 words
A method according to claim 1 wherein the plated article is heated in a molten treating bath composed of molten boric acid or borate and at least one element selected from the group consisting of Group-Va elements and chromium and held in the bath for enough time to form the two-layered carbide surface.
Claim 7
Dependent Claim
26 words
A method according to claim 5 wherein the borate is a member selected from the group consisting of sodium borate, potassium borate and a mixture thereof.
Claim 8
Dependent Claim
29 words
A method according to claim 5 wherein electricity is applied to the plated article, which is used as a cathode, while said article is immersed in the molten bath.
Claim 9
Dependent Claim
48 words
A method according to claim 1 wherein the plated article is heated in a powder mixture of fluoborate and at least one element selected from the group consisting of Group-Va elements and chromium and maintained in said powder mixture for enough time to form the two-layered carbide surface.
Claim 10
Dependent Claim
31 words
A method according to claim 1 wherein the plated article is heated in a gas comprising at least one gaseous element selected from the group consisting of Group-Va elements and chromium.
Claim 11
Dependent Claim
24 words
A method according to claim 1 wherein the thickness of the outer carbide layer is within a range of from about 2 to 20μ.
References Cited (Backward Citations)
US2685543A
Cited
US3671297A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-02-10 | 1984-08-11 | 1985-02-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-02-10 | 1988-08-11 | 1989-02-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-02-10 | 1992-08-11 | 1993-02-10 | $7700.00 | Window Closed / Lapsed |