# US 8,771,438 B2 · Plasma nitriding surface treatment method for gray cast iron part

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- Number: US 8,771,438 B2
- Document ID: US8771438B2
- Status: Granted
- Kind: B2
- Application number: 13/614,983
- Filed: 2012-09-13
- Published: 2013-10-31
- Granted: 2014-07-08
- Earliest claimed: 2012-04-27
- Assignees: Hyundai Motor Company
- Applicants: Jae Young Lee; Seong Jin Kim; Jai Min Han; Yoon Cheol Kim; Hyun Dal Park
- Inventors: Jae Young Lee; Seong Jin Kim; Jai Min Han; Yoon Cheol Kim; Hyun Dal Park
- Web page: https://patentgrep.com/patent/US8771438B2

## CPC

- C23C 8/02: Pretreatment of the material to be coated (C23C8/04 takes precedence)
- C23C 8/36: using ionised gases, e.g. ionitriding
- C23C 8/38: Treatment of ferrous surfaces
- 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

Disclosed is a plasma nitriding surface treatment method for a gray cast iron part. In the plasma nitriding surface treatment method, a nitride layer is formed on a surface of the gray cast iron part by a selective ion nitriding treatment. The plasma nitriding surface treatment method is carried out such that the surface of the gray cast iron part is prevented from being deformed, and a reduction of the frictional coefficient of the part is prevented.

## Claims

### Claim 1

A plasma nitriding surface treatment method for a gray cast iron part, comprising:
forming a nitride layer on a surface of the gray cast iron part by a selective ion nitriding treatment, and
forming an oxide layer on the surface of the gray cast iron part after forming the nitride layer, wherein the oxide layer is formed using a salt bath oxidation process or vapor to inhibit formation of a porous layer and facilitate infiltration of nitrogen atoms,
wherein the surface of the gray cast iron part is prevented from being deformed, and a frictional coefficient of the gray cast iron part is maintained.

### Claim 2 (depends on 1)

The plasma nitriding surface treatment method of claim 1, wherein the ion nitriding treatment is performed by a plasma nitriding treatment process to minimize generation of an epsilon phase and induce generation of a gamma prime phase.

### Claim 3 (depends on 1)

The plasma nitriding surface treatment method of claim 1, wherein the ion nitriding treatment is performed at a temperature of about 400° C. to about 550° C. for about 120 minutes to about 300 minutes.

### Claim 4 (depends on 1)

The plasma nitriding surface treatment method of claim 1, wherein in an ion nitriding atmosphere during the ion nitriding treatment, carbon is inhibited to induce generation of a single phase of a gamma prime and inhibit generation of a compound phase of the gamma prime.

### Claim 5

The plasma nitriding surface treatment method of claim wherein the oxide layer is (Fe3O4).

### Claim 6 (depends on 1)

The plasma nitriding surface treatment method of claim 1, wherein the salt bath oxidation process is performed for about 20 minutes to 60 minutes to prevent oxidation of the surface of the part and deformation of the part and such that the nitride layer is corroded to reduce a total thickness of the nitride and oxide layers.

### Claim 7 (depends on 1)

The plasma nitriding surface treatment method of claim 1, wherein in the forming of the oxide layer, a temperature of about 200° C. to about 500° C. is maintained to increase an infiltration depth of the oxide layer.