# US 8,303,731 B2 · Low pressure carbonitriding method and device

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- Number: US 8,303,731 B2
- Document ID: US8303731B2
- Status: Granted
- Kind: B2
- Application number: 11/918,805
- Filed: 2006-04-19
- Published: 2011-02-17
- Granted: 2012-11-06
- Earliest claimed: 2005-04-19
- Assignees: ECM Technologies
- Inventors: Jean Berlier; Aymeric Goldsteinas; Xavier Doussot
- Web page: https://patentgrep.com/patent/US8303731B2

## CPC

- C23C 8/32: of ferrous surfaces
- C23C 8/34: more than one element being applied in more than one step
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)

## Abstract

A method for carbonitriding a steel part arranged in an enclosure maintained at a reduced internal pressure, the part being maintained at a temperature level, comprising an alternation of first and second steps, a carburizing gas being injected into the enclosure during the first steps only and a nitriding gas being injected into the enclosure only during at least part of at least two second steps.

## Claims

### Claim 1

A method for carbonitriding a steel part arranged in an enclosure, the part being maintained at a temperature level, the method comprising an alternation of first steps and second steps, in which each of the first steps is followed by one of the second steps, a carburizing gas being injected into the enclosure during the first steps only and a nitriding gas being injected into the enclosure only during at least part of at least two second steps, the nitriding gas being injected into the enclosure during each of the at least two second steps for a time shorter than the duration of said each of the at least two second steps, the rest of the second step being carried out in the presence of a neutral gas.

### Claim 2 (depends on 1)

The method of claim 1, wherein the carburizing gas is propane or acetylene.

### Claim 3 (depends on 1)

The method of claim 1, wherein the nitriding gas is ammonia.

### Claim 4 (depends on 1)

The method of claim 1, wherein a neutral gas is injected into the enclosure simultaneously with the nitriding gas.

### Claim 5 (depends on 1)

The method of claim 1, wherein the first and second steps are performed at a constant pressure lower than 1,500 pascals.

### Claim 6 (depends on 1)

The method of claim 1, wherein the temperature level is in the range of −800° C. and 1050° C.

### Claim 7 (depends on 1)

The method of claim 1, wherein the temperature level is higher than 900° C.