PURPOSE: To improve mechanical characteristics of a coating film such as the adhesive strength by successively coating a steel material with metallic Ti and TixAlyN as a solid soln. of Al in TiN.

CONSTITUTION: A steel material is coated with a metallic Ti layer of ≤0.5μm thickness. It is necessary that the Ti layer is formed by impressing bias voltage on the base material. By this impression, Ti ions are implanted in the surface of the base material to enhance the adhesive strength of the Ti layer. The coated steel material is further coated with a TixAlyN layer. In the compsn., the atomic concn. (y) of Al is <0.6 and x+y=1. When the thickness of the Ti layer is >0.5μm and accounts for a larger percentage of the thickness of the resulting coating film, the hardness of the film is lowered and the mechanical strength is deteriorated.