# US 2014/0290800 A1 · Carbonitriding Method having a Final Nitridation Step During Temperature Decrease

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- Number: US 2014/0290800 A1
- Document ID: US20140290800A1
- Status: Published application
- Kind: A1
- Application number: 14/354,393
- Filed: 2012-10-08
- Published: 2014-10-02
- Earliest claimed: 2011-10-31
- Assignees: ECM Technologies
- Applicants: ECM Technologies
- Inventors: Philippe Lapierre; Jerome Lardinois; Yves Giraud; Alfred Rallo
- Web page: https://patentgrep.com/patent/US20140290800A1

## CPC

- C23C 8/32: of ferrous surfaces
- C23C 8/02: Pretreatment of the material to be coated (C23C8/04 takes precedence)
- C23C 8/22: of ferrous surfaces
- C23C 8/26: of ferrous surfaces
- C23C 8/34: more than one element being applied in more than one step
- C23C 8/80: After-treatment
- 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 the low-pressure carbonitriding of steel parts, in particular parts used in the manufacture of automobiles comprises a heating step that includes a simple heating phase (M) followed by an initial nitridation phase (Ni) from a temperature between 700° C. to 750° C. to a temperature between 860° and 1000° C. carried out using a reduced temperature gradient relative to the simple heating phase. The method further includes alternate cementing (C1-Cn) and nitridation (N1-Nn) steps at constant temperature, wherein the final nitridation step is accompanied with a decrease in temperature immediately before quenching (T).

## Claims

### Claim 1

A carbonitriding steel parts method, particularly parts used to manufacture automobile vehicles, comprising alternated cementation and nitriding steps at constant temperature, preceded by a heating step and followed by a quenching, wherein it comprises a final nitriding step accompanied by a cooling immediately before the quenching.

### Claim 2 (depends on 1)

The carbonitriding method of claim 1, wherein the cooling is carried out down to a temperature in the range from 900° C. to 800° C.

### Claim 3 (depends on 1)

The carbonitriding method of claim 1, wherein the cooling is carried out with a temperature gradient in the range from 10° C./min to 1° C./min.

### Claim 4 (depends on 1)

The carbonitriding method of claim 1, wherein the final nitriding step comprises a temperature stage.

### Claim 5 (depends on 1)

The carbonitriding method of claim 1, wherein the heating step comprises a simple heating phase followed by an initial nitriding phase during which the heating is carried on.

### Claim 6 (depends on 5)

The carbonitriding method of claim 5, wherein the initial nitriding phase is carried out from a temperature in the range from 700° C. to 750° C. and up to a temperature in the range from 860° C. to 1,000° C.

### Claim 7 (depends on 5)

The carbonitriding method of claim 5, wherein during the initial nitriding phase, the temperature rise is carried out with a decreased temperature gradient as compared with the simple heating phase.

### Claim 8 (depends on 7)

The carbonitriding method of claim 7, wherein the initial nitriding phase comprises a temperature stage.

### Claim 9 (depends on 7)

The carbonitriding method of claim 7, wherein the initial nitriding phase is immediately followed by a first cementation step.

### Claim 10 (depends on 5)

The carbonitriding method of claim 5, wherein the initial nitriding phase is carried out with a temperature gradient in the range from 3.5° C./min to 10° C./min.