US5211768A
Expired / Lapsed
US
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Method of nitriding work pieces of steel under pressure
Assignee: ALD Vacuum Technologies GmbH
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Filing: 1992-08-07
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Granted: 1993-05-18
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Expires: 2012-08-07
Abstract
Abstract Very low-pore, thick nitride cases may be obtained in a short time during a gas nitriding process in accordance with the invention. This process includes nitriding in a gaseous mixture containing about 5 to 95% by volume ammonia and about 95 to 5% by volume nitrogen. The nitriding process is most preferably carried out at essentially a constant pressure above about 0.2 MPa.
Inventors
- 👤 Friedrich Preisser
- 👤 Rudolf Seif
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 12:05
CPC Classifications
C; C23; C23C; C23C8/00; C23C8/06; C23C8/08; C23C8/24; C23C8/26
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
71 words
A method for nitriding steel work pieces, comprising: nitriding said work pieces by subjecting the work pieces to a temperature above 425° C. and an essentially constant pressure above 0.2 MPa and for a sufficient period of time in a gaseous atmosphere which includes about 5 to 95% by volume ammonia and about 95 to 5% by volume molecular nitrogen, said pressure being sufficient to thereby provide the desired nitride case.
Claim 2
Independent Claim
71 words
A method for nitriding steel work pieces, comprising: nitriding said work pieces by subjecting the work pieces to a temperature above 425° C. and an essentially constant pressure above 0.2 MPa and for a sufficient period of time in a gaseous atmosphere which includes about 5 to 95% by volume ammonia and about 95 to 5% by volume molecular nitrogen, said pressure being sufficient to thereby provide the desired nitride case.
Claim 3
Dependent Claim
18 words
The method according to claim 1, wherein the nitride case so provided is up to 50 micrometers thick.
Claim 4
Dependent Claim
19 words
The method according to claim 1, wherein the work pieces are subjected to the gaseous atmosphere for 4-5 hours.
Claim 5
Dependent Claim
15 words
The method according to claim 1, wherein the nitride case is essentially free from pores.
Claim 6
Dependent Claim
19 words
The method according to claim 1, wherein a white layer which is essentially 100% in the γphase is formed.
Claim 7
Dependent Claim
15 words
The method according to claim 1, wherein the work piece is constructed of austenitic steel.
Claim 8
Dependent Claim
20 words
The method according to claim 1, wherein the work piece is constructed of a steel with a high chromium content.
Claim 9
Dependent Claim
18 words
The method according to claim 1, wherein the pressure is in the range of 0.2 to 10 MPa.
Claim 10
Dependent Claim
16 words
The method according to claim 1, wherein the temperature for nitriding is up to 1200° C.
Claim 11
Dependent Claim
20 words
The method according to claim 1, wherein the temperature for nitriding is in the range of 500° to 900° C.
Claim 12
Dependent Claim
22 words
The method according to claim 1, wherein the gaseous atmosphere includes about 30% by volume ammonia and about 70% by volume nitrogen.
Claim 13
Dependent Claim
15 words
The method according to claim 11, wherein the temperature for nitriding is about 700° C.
Claim 14
Dependent Claim
13 words
The method according to claim 12, wherein the pressure is 2 about MPa.
Claim 15
Dependent Claim
14 words
The method according to claim 13, wherein the nitriding step takes about 1 hour.
Claim 16
Dependent Claim
19 words
The method according to claim 14, wherein a white layer is produced with a thickness of about 40 micrometers.
Claim 17
Dependent Claim
22 words
The method according to claim 1, wherein the gaseous atmosphere includes about 80% by volume ammonia and about 20% by volume nitrogen.
Claim 18
Dependent Claim
13 words
The method according to claim 16, wherein the pressure is about 1 MPa.
Claim 19
Dependent Claim
15 words
The method according to claim 17, wherein the temperature for nitriding is about 580° C.
Claim 20
Dependent Claim
14 words
The method according to claim 18, wherein the nitriding step takes about 4 hours
Claim 21
Dependent Claim
16 words
The method according to claim 19, wherein a diffusion zone about 100 micrometers thick is produced.
Claim 22
Dependent Claim
22 words
The method according to claim 1, wherein the gaseous atmosphere is about 70% by volume ammonia and about 30% by volume nitrogen.
Claim 23
Dependent Claim
15 words
The method according to claim 21, wherein the temperature for nitriding is about 550° C.
Claim 24
Dependent Claim
13 words
The method according to claim 22, wherein the pressure is about 8 MPa.
Claim 25
Dependent Claim
14 words
The method according to claim 23, wherein the nitriding step takes about 2 hours.
Claim 26
Dependent Claim
17 words
The method according to claim 24, wherein a white layer which is 50 micrometers thick is produced.
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) | 1996-05-17 | 1996-11-16 | 1997-05-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-05-17 | 2000-11-16 | 2001-05-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-05-17 | 2004-11-16 | 2005-05-18 | $7700.00 | Window Closed / Lapsed |