HARDENING OF FERROUS ALLOYS BY COATING WITH CARBO-NITRIDE OF VANADIAM, NIOBIAM OR TANTALUM

摘要

A method of providing the surface of a ferrous alloy article containing at least 0.2% by weight of carbon with a surface layer composed of the nitrocarbide of an element of Group Va of the periodic table and an inner ferrous alloy layer containing nitrogen located immediately below the surface layer. The layers are formed by (a) nitriding the article surface and (b) a thermal diffusion treatment thereof with a treating agent containing the Group Va element. The formation of the layers can be accomplished easily and rapidly without presenting any problem when the article is later hardened.