Method of carburizing austenitic stainless steel and austenitic stainless steel products obtained thereby

• US 5,792,282 A
• Filed: 05/13/1996
• Issued: 08/11/1998
• Est. Priority Date: 04/17/1995
• Status: Expired due to Term

• Current Assignee: Air Water Incorporated
• Original Assignee: Daido Hoxan, Inc. (Air Water Incorporated)
• Inventors: Hayashida, Tadashi, Kitano, Kenzo, Senbokuya, Haruo, Tahara, Masaaki
• Primary Examiner(s): Yee, Deborah
• Application Number:
  US08/645,264
• Time in Patent Office: 820 Days
• Field of Search: 148/206, 148/225, 148/316, 148/319
• US Class Current: 148/206
• CPC Class Codes: C23C 8/02 Pretreatment of the material to be coated C23C8/04 takes precedence
• CPC Class Codes: C23C 8/34 more than one element being applied in more than one step

Abstract

A method of carburizing austenitic stainless steel comprising the steps of holding austenitic stainless steel in a fluorine- or fluoride-containing gas atmosphere with heating prior to carburizing and carburizing the austenitic stainless steel at a temperature not more than 680° C. wherein said austenitic stainless steel is stable austenitic stainless steel having 1 to 6 weight % molybdenum or 13 to 25 weight % chromium, wherein a carburized hard layer having corrosion resistance superior to base material forms and austenitic stainless steel products obtained thereby.

Claims

1. A method of carburizing austenitic stainless steel comprising the steps of holding austenitic stainless steel in a fluorine- or fluoride-containing gas atmosphere with heating prior to carburizing and carburizing the austenitic stainless steel at a temperature not more than 680°

C. wherein said austenitic stainless steel is stable austenitic stainless steel having 1 to 6 weight % molybdenum or 13 to 25 weight % chromium, wherein a carburized hard layer having corrosion resistance superior to base material forms.

2. A method of carburizing austenitic stainless steel according to claim 1, wherein the carburizing temperature is set within a range of 400°

to 500°

C.

3. A method of carburizing austenitic stainless steel according to claim 1 or 2, wherein the temperature in fluorine- or fluoride-containing gas atmosphere in the heating step is set within a range of 250°

to 450°

C.

4. Austenitic stainless steel products wherein base material is stable austenitic stainless steel including 1 to 6 weight % molybdenum or 13 to 25 weight % chromium, a surface layer in depth of 5 to 70 μ

m from the surface is hardened by invasion of carbon atoms so as to be formed into a carburized hard layer whose hardness is 500 to 1050 Hv of Micro Vickers hardness, wherein the carburized hard layer is formed by an austenitic phase in which chromium carbide particles do not exist and whose corrosion resistance is superior to the base material.