PURPOSE: To form the wear resistant films having good adhesion and surface smoothness on the engaging surfaces of the power transmission parts made of an aluminum alloy by thermally spraying a high-carbon steel material which contains a large amt. of Cr and is specified in grain size by a high-speed flame spraying method to these engaging surfaces.

CONSTITUTION: The high-carbon steel material which contains the large amt. of the Cr and has the 10 to 45μm range of the grain size is thermally sprayed by the high-speed flame spraying method to an approximately V-shaped groove 11 having slopes 11a, 11b and a slight base 11c, which is the belt engaging surface of the power transmission parts formed of the Al alloy, for example, a pulley 1 formed continuously with the above-mentioned groove 11 on its outer peripheral surface, by which the thermally sprayed film 12 having a uniform thickness is formed on all the surfaces 11a, 11b, 11c of the groove 11. As a result, the pulley 1 having the good wear resistance of the engaging surface is obtd.