Patent ID: 6277214
Filing Date: 2001-08-21
Classification: C23C

Abstract:
A process for treating an iron-based alloy material comprising:a) providing a first oxygen supply to the material;b) heating the material to a first temperature for a first period of time in the presence of the first oxygen supply, wherein the first temperature, first period of time and first oxygen supply are together controlled so as to form austenite in the material and to form an external iron oxide scale comprised substantially of wustite on a metallic substrate;c) cooling the material sufficiently rapidly to form martensite or bainite in the material and to substantially prevent the wustite in the scale from decomposing;d) providing a second oxygen supply to the material;e) re-heating the material to a second temperature, lower than the first temperature, for a second period of time in the presence of the second oxygen supply, wherein the second temperature, second period of time and the second oxygen supply are together controlled so as to alter a mechanical property of the material without forming austenite, and so as to transform a surface of the scale substantially to magnetite, to form a magnetite surface, while leaving an intermediate layer composed substantially of wustite between the metallic substrate and the magnetite surface.