PURPOSE: To obtain a hardened film on the surface of a metal material, by an easy method wherein a paste containing an autogenous alloy is applied to the surface of a metal and the whole is heated to the m.p. of the autogenous alloy or higher.

CONSTITUTION: A homogenous paste consisting of an autogenous alloy powder obtained by adding B and Si to a Ni base, or a Ni-Cr base or a Ni-Co base alloys, a solvent such as α-terpineol and a binder such as methyl cellulose is prepared. This paste is applied to the surface of a metal material by a screen printing method, a dripping method, a brush coating method or a spray method. After the obtained coating is dried, it is heated to the m.p. of the autogenous alloy or higher and the solvent and the binder are removed to obtain an autogenous alloy film.