Method of treating the surface of iron alloy materials

• US 4,765,847 A
• Filed: 02/03/1987
• Issued: 08/23/1988
• Est. Priority Date: 06/17/1985
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toyota CHUO Kenkyusho 41-1 AZA Yokomichi OAZA Nagakute-Cho Aichi-Gun Aichi-Ken Japan
• Original Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Inventors: Sugimoto, Yoshihiko, Ohta, Yukio, Arai, Tohru, Endo, Junji, Fujita, Hironori
• Primary Examiner(s): Brody, Christopher W.
• Application Number:
  US07/023,862
• Time in Patent Office: 567 Days
• Field of Search: 148/16, 148/16.6, 148/16.7, 148/15, 148/15.5, 148/14, 148/19
• US Class Current: 148/217
• CPC Class Codes: C23C 12/00 Solid state diffusion of at least one non-metal element other than silicon and at least one metal element or silicon into metallic material surfaces
• CPC Class Codes: C23C 16/34 Nitrides C23C16/303 takes precedence
• CPC Class Codes: C23C 16/36 Carbonitrides

Abstract

A layer of a nitride or carbonitride containing at least one of chromium, Group Va elements, titanium and zirconium is formed on the surface of an iron alloy material which has been nitrided. The layer is formed by heating the iron alloy material at a temperature not exceeding 700° C. with a material containing at least one of chromium, Group Va elements, titanium and zirconium and a treating agent. It is a dense layer bonded tightly to the iron alloy material. As a low temperature not exceeding 700° C. is employed, no large amount of heat energy is required, nor is any thermal strain produced in the iron alloy material.

Claims

1. A method of treating the surface of an iron alloy material which comprises:

nitriding said iron alloy material to form on said surface thereof a layer of a nitride composed of iron and nitrogen or a carbonitride composed of iron, carbon and nitrogen; and

heating said iron alloy material at a temperature up to 580°

C. with a material containing at least one surface layer-forming element selected from the group consisting of chromium, titanium and zirconium, and a treating agent, so that said surface layer-forming element may be diffused into said surface of said iron alloy material to form thereon a surface layer composed of a nitride or carbonitride of said element, said treating agent being at least one compound selected from the group consisting of chlorides, fluorides, borofluorides, oxides, bromides, iodides, carbonates, nitrates and borates of alkali and alkaline earth metals, ammonium halides and metal halides.

2. A method as set forth in claim 1, wherein said nitriding is carried out by a method selected from gas nitriding, gas soft-nitriding, salt bath soft-nitriding and glow discharge nitriding.

3. A method as set forth in claim 1, wherein said material containing at least one surface layer-forming element is at least one material selected from the group consisting of said element in pure metallic form, an alloy containing said element and a compound containing said element.

4. A method as set forth in claim 1, wherein said heating is carried out by immersing said iron alloy material and said material containing said element in a molten bath composed of said treating agent.

5. A method as set forth in claim 1, wherein said heating is carried out by employing said iron alloy material as a cathode and conducting electrolysis in a molten bath composed of said treating agent and holding said material containing said element.

6. A method as set forth in claim 1, wherein said heating is carried out by placing said iron alloy material in a mixed powder composed of said treating agent and said material containing said element.

7. A method as set forth in claim 1, wherein said heating is carried out after a paste prepared from a mixed powder composed of said treating agent and said material containing said element has been applied to said iron alloy material.

8. A method as set forth in claim 1, wherein when said iron alloy material is heated, it is kept away from contact with a mixed powder composed of said treating agent and said material containing said element.

9. A method as set forth in claim 1, wherein said iron alloy material is heated in a fluidized mixed powder composed of said treating agent and said material containing said element.

10. A method as set forth in claim 1, wherein said heating is carried out at a temperature of at least 450°

C.

11. A method of treating the surface of an iron alloy material which comprises:

nitriding said iron alloy material to form on said surface thereof a layer of a nitride composed of iron and nitrogen or a carbonitride composed of iron, carbon and nitrogen, and

heating said iron alloy material at a temperature up to 580°

C. with a material containing (a) at least one surface layer-forming element from the group consisting of Group Va elements of the periodic table and (b) a treating agent, so that said surface layer-forming element may be diffused into said surface of said iron alloy material to form thereon a surface layer composed of a nitride or carbonitride of said element;

said treating agent being at least one compound selected from the group consisting of chlorides, fluorides, borofluorides, oxides, bromides, iodides, carbonates, nitrates and borates of alkali and alkaline earth metals, ammonium halides and metal halides.

12. A method as set forth in claim 11, wherein said nitriding is carried out by a method selected from gas nitriding, gas soft-nitriding, salt bath soft-nitriding and glow discharge nitriding.

13. A method as set forth in claim 11, wherein said material containing at least one surface layer-forming element is at least one material selected from the group consisting of said element in pure metallic form, an alloy containing said element and a compound containing said element.

14. A method as set forth in claims 11, wherein said heating is carried out by immersing said iron alloy material and said material containing said element in a molten bath composed of said treating agent.

15. A method as set forth in claims 11, wherein said heating is carried out by employing said iron alloy material as a cathode and conducting electrolysis in a molten bath composed of said treating agent and holding said material containing said element.

16. A method as set forth in claim 11, wherein said heating is carried out by placing said iron alloy material in a mixed powder composed of said treating agent and said material containing said element.

17. A method as set forth in claim 11, wherein said heating is carried out after a paste prepared from a mixed powder composed of said treating agent and said material containing said element has been applied to said iron alloy material.

18. A method as set forth in claim 11, wherein, when said iron alloy material is heated, it is kept away from contact with a mixed powder composed of said treating agent and said material containing said element.

19. A method as set forth in claim 11, wherein said iron alloy material is heated in fluidized mixed powder composed of said treating agent and said material containing said element.

20. A method as set forth in claim 11, wherein said heating is carried out at a temperature of at least 450°

C.