METHOD OF PREPARING CORROSION RESISTANT METALLIC ARTICLES

• US 3,660,173 A
• Filed: 06/23/1970
• Issued: 05/02/1972
• Est. Priority Date: 06/25/1969
• Status: Expired due to Term

• Current Assignee: Akira Matsuno, Hiroyuki Kagawa, Humio Kizu, Ikuzo Shimizu, Takao Sasame
• Original Assignee: Akira Matsuno, Hiroyuki Kagawa, Humio Kizu, Ikuzo Shimizu, Takao Sasame
• Inventors: Matsuno, Akira, Sasame, Takao, Shimizu, Ikuzo, Kizu, Humio, Kagawa, Hiroyuki
• Primary Examiner(s): Kendall, Ralph S.
• Application Number:
  US05/049,052
• Time in Patent Office: 679 Days
• Field of Search: 148/6.35,6.3 75/126D,126F,124
• US Class Current: 428/332
• CPC Class Codes: C22C 38/28 with titanium or zirconium
• CPC Class Codes: C23C 8/10 Oxidising
• CPC Class Codes: Y10T 428/26 Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
• CPC Class Codes: Y10T 428/263 Coating layer not in excess of 5 mils thick or equivalent
• CPC Class Codes: Y10T 428/264 Up to 3 mils
• CPC Class Codes: Y10T 428/265 1 mil or less

Abstract

A method of furnishing the surface of ferroalloys with resistance to hot corrosive gases containing halogens or compounds thereof or to general oxidation which comprises the steps of heating in an oxidizing atmosphere at a temperature of 1,000* to 1,400* C for a suitable number of hours articles prepared from a metal consisting of 10 to 25 percent of chromium, 2 to 5 percent of aluminum, less than 0.04 percent of carbon, 0.005 to 0.05 percent of nitrogen, 0.1 to 0.6 percent of titanium, 0.01 to 0.5 percent of zirconium, iron as the remainder and further containing ordinary impurities, in which constitution ratio of Ti% + Zr% to N% ranges from 10 to 60, so as to diffuse by migration in the surface layer of the base body of the article part of oxidizable elements contained therein, thereby forming an oxide layer mainly consisting of Alpha Al2O3 on said surface.

Claims

2. A method of preparing corrosion-resistant metallic articles which comprises forming articles from a metal consisting of 10 to 25 percent of chromium, 2 to 5 percent of aluminum, less than 0.04 percent of carbon, 0.005 to 0.05 percent of nitrogen, 0.1 to 0.6 percent of titanium, 0.01 to 0.2 percent of zirconium, iron as the remainder and further containing ordinary impurities, in which cOnstitution ratio of Ti% + Zr% to N% ranges from 10 to 60, heating the article in an oxidizing atmosphere for a suitable number of hours at a temperature of from 1,000* to 1,400* C to diffuse by migration in the surface layer of the base body of the article part of oxidizable elements contained therein, thereby forming on said surface an oxide layer averaging from 3 to 100 microns in thickness which mainly consists of Alpha Al2O3, and the outermost region of which is constituted by a thin film of Al2O3.TiO2.

3. A method of preparing corrosion-resistant metallic articles which comprises forming articles from a metal consisting of 10 to 25 percent of chromium, 2 to 5 percent of aluminum, less than 0.04 percent of carbon, 0.005 to 0.05 percent of nitrogen, 0.2 to 0.6 percent of titanium, more than 0.2 to 0.5 percent of zirconium, iron as the remainder and further containing ordinary impurities, in which constitution ratio of Ti% + Zr% to N% ranges from 10 to 60 and the ratio of Ti% to Zr% is set at a larger value than 0.9, heating the article in an oxidizing atmosphere for a suitable number of hours at a temperature of from 1,000* to 1,400* C to diffuse by migration in the surface layer of the base body of the article part of oxidizable elements contained therein, thereby forming on said surface an oxide layer 3 to 300 microns thick on average mainly consisting of Alpha Al2O3 settled in the metallic base body in a rooty form.

4. Corrosion-resistant metallic article comprising 10 to 25 percent of chromium, 2 to 5 percent of aluminum, less than 0.04 percent of carbon, 0.005 to 0.05 percent of nitrogen, 0.1 to 0.6 percent of titanium, 0.01 to 0.5 percent of zirconium, iron as the remainder and further containing ordinary impurities, in which the constitution ratio of Ti % + Zr % to N % ranges from 10 to 60, and having a surface oxide layer consisting essentially of Alpha Al2O3 3 to 300 microns thick.

5. Article of claim 4, wherein zirconium is from 0.01 to 0.2 percent, and the oxide layer has a thickness of 3 to 100 microns and the outermost region of which is a thin film of Al2O3.TiO2

6. Article of claim 4, wherein titanium is from 0.2 to 0.6 percent, zirconium is from 0.2 to 0.5 percent, the weight ratio of titanium to zirconium is greater than 0.9, and said oxide layer is settled in the article in a rooty form.