Method of making surface layers with improved corrosion properties on articles of iron-chromium alloys, and a surface layer made by the method
US4168184A · kind A · utility
Inventors
Key dates
| Filing date | Jul 21, 1978 |
| Grant date | Sep 18, 1979 |
| Priority date | — |
| Expiry date | Jul 21, 1998 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T428/265
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
A method of making surface layers, with improved corrosion properties, on articles of iron-chromium alloys, and the article produced thereby. The article is heated in an oxygen containing gaseous atmosphere with a total vacuum of about 10.sup.-1 down to 10.sup.-8 mm Hg, preferably about 10.sup.-5 mm Hg, to a temperature, at which diffusion of the most reactive alloy component or components, primarily chromium, with respect to the tendency of combining with oxygen, to the surface becomes perceptible, at which temperature the remaining properties of the alloy substantially are maintained. For most iron-chromium alloys that temperature is between 300.degree. C. and 600.degree. C. The aforesaid condition of treatment, is maintained until a surface layer containing oxidized chromium has grown to a thickness of preferably 10.sup.-9 -10.sup.-7 m, and with respect to structure and composition is transformed from a condition on the surface to a condition in the matrix of the metal alloy.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.