Steel article having a nitrided and partly oxidized surface and method for producing same

摘要

Surface-hardening of a steel article which is to be mated with a separate article so as to make a sliding or rolling face-to-face contact is accomplished by heating the steel article in ammonia gas containing from 1 to 10% by volume of air. The treated article has an oxidized layer as an outmost part of a nitride layer. The oxidized layer abrades more readily than the nitride layer, so that the article has the property of smoothly fitting a separate article practically from the start of use and exhibits a good wear resistance during subsequent use.