US4194930A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ion-nitriding process
Assignee: Kawasaki Motors Ltd
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Filing: 1978-10-20
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Granted: 1980-03-25
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Expires: 1998-10-20
Abstract
Abstract The present invention provides an ion-nitriding process wherein a workpiece having at least one aperture is subjected to a DC voltage in an atmosphere of nitrogen-containing gas, characterized in that a first nitriding step is carried out under a vacuum which is strong enough to suppress arc discharge on the workpiece, and a second nitriding step is carried out under a weaker vacuum as compared to that in the first step so that glow discharge is produced even in the aperture of the workpiece.
Inventors
- 👤 Akio Tanaka
- 👤 Mizuo Edamura
- 👤 Satoshi Furuitsu
- 👤 Satoru Kunise
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 19:29
CPC Classifications
C; C23; C23C; C23C8/00; C23C8/06; C23C8/36; C23C8/38
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
99 words
In an ion-nitriding process including the steps of subjecting a workpiece having at least one aperture to a DC voltage in an atmosphere of nitrogen-containing gas so as to produce a glow discharge on the workpiece, the improvement comprising a first nitriding step which is carried out under a vacuum which is strong enough to suppress arc discharge on the workpiece, and a second nitriding step which is carried out under a vacuum which is weak as compared with the vacuum in the first nitriding step, so that glow discharge is produced even in the aperture of the workpiece.
Claim 2
Dependent Claim
99 words
In an ion-nitriding process including the steps of subjecting a workpiece having at least one aperture to a DC voltage in an atmosphere of nitrogen-containing gas so as to produce a glow discharge on the workpiece, the improvement comprising a first nitriding step which is carried out under a vacuum which is strong enough to suppress arc discharge on the workpiece, and a second nitriding step which is carried out under a vacuum which is weak as compared with the vacuum in the first nitriding step, so that glow discharge is produced even in the aperture of the workpiece.
Claim 3
Dependent Claim
19 words
A process in accordance with claim 1 in which said nitrogen-containing gas is a mixture of nitrogen and hydrogen.
Claim 4
Dependent Claim
24 words
A process in accordance with claim 2 in which the ratio of nitrogen and hydrogen is changed between the first and second nitriding steps.
Claim 5
Dependent Claim
31 words
A process in accordance with claim 3 in which said ratio of nitrogen to hydrogen is increased in the second nitriding step as compared with that in the first nitriding step.
Claim 6
Dependent Claim
36 words
A process in accordance with claim 1 in which said first nitriding step is preceded by a preheating step which is carried out by producing a glow discharge on the workpiece in an atmosphere of hydrogen.
Claim 7
Dependent Claim
35 words
A process in accordance with claim 1 in which the vacuum in the first nitriding step is between 1 and 5 Torr and that in the second nitriding step is between 3 and 10 Torr.
Claim 8
Dependent Claim
27 words
A process in accordance with claim 4 in which the ratio of nitrogen gas to hydrogen gas in the first nitriding step is as low as 1:3.
Claim 9
Dependent Claim
29 words
A process in accordance with claims 4 or 7 in which the ratio of nitrogen gas to hydrogen gas in the second nitriding step is as high as 3:1.
Claim 10
Dependent Claim
21 words
A process in accordance with claim 5 in which the workpiece is heated to a temperature between 300° and 570° C.
Claim 11
Dependent Claim
21 words
A process in accordance with claim 9 in which the workpiece is heated to a temperature between 550° and 560° C.
Claim 12
Dependent Claim
80 words
A process in accordance with claim 10 in which the workpiece is first heated to about 550° C. under an atmosphere of hydrogen, the first nitriding step is carried out under an atmosphere of a mixture of nitrogen and hydrogen present in about a 2:1 ratio and a vacuum pressure of about 1 Torr, and the second nitriding step is carried out in the same gaseous atmosphere as the first nitriding step, but at vacuum pressure of about 3 Torr.
Claim 13
Dependent Claim
64 words
A process in accordance with claim 2 in which the nitriding steps are carried out at a temperature of about 550° C. and under an atmosphere of a mixture of nitrogen and hydrogen present in about a 2:1 ratio, the vacuum pressure of the first nitriding step being about 5 Torr and the vacuum pressure of the second nitriding step being about 7.5 Torr.
Claim 14
Dependent Claim
78 words
A process in accordance with claim 4 in which the nitriding steps are carried out at a temperature of about 550° C., the first nitriding step being in an atmosphere of nitrogen and hydrogen present in a ratio of about 1:3 and under a vacuum pressure of about 3 Torr, the second nitriding step being in an atmosphere of nitrogen and hydrogen present in a ratio of about 3:1 and under a vacuum pressure of about 5 Torr.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-03-25 | 1983-09-24 | 1984-03-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-03-25 | 1987-09-24 | 1988-03-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-03-25 | 1991-09-24 | 1992-03-25 | $7700.00 | Window Closed / Lapsed |