Method of treating ferrous surfaces subjected to high friction strains

摘要

In a method of increasing the wear resistance and the corrosion resistance of opposed bearing surfaces of parts subjected to reciprocal friction, in particular when the product of the pressure distributed over the bearing surfaces by the relative speed of the latter exceeds 0.4 MPa.m/s, thermochemical diffusion of nitrogen is effected by nitriding or nitrocarburizing in a molten salt bath at a temperature of 570 DEG C.+/-15 DEG C. followed by an oxidizing or phosphating surface chemical reaction providing resistance to wet corrosion. The nitriding or nitrocarburizing molten salt bath is made up of alkaline carbonates and cyanates and further contains sulfur-containing substances in the following percentages by weight: 30%<CNO-<45% 15%<CO32-<25% 15%<Na+<25% 20%<K+<30% 1%<Li+<6% 1 ppm<S2-<100 ppm The time for which parts are immersed in the bath is between 15 minutes and 45 minutes./!