Sliding wear behaviour of a liquid nitrocarburised precipitation-hardening (PH) stainless steel

A precipitation-hardening stainless steel, of commercial trade name CORRAX, similar to DIN X3CrNiMoAl 13-8-2 grade steel (W.Nr. 1.4534) has been subjected to liquid nitrocarburising in cyanide salt bath to enhance its wear behavior. The wear resistance was evaluated using a pin-on-disk wear testing method with a tungsten carbide counterface against three different steel conditions: nitrocarburised, age-hardened (aged) and solution treated (delivery state). The variation of friction coefficient and wear volume is presented as a function of applied normal load (5, 6, 8 and 10 N) and sliding distance for a constant running speed (0.6 m/s). The pin end (in contact with the disk) had a radius of curvature up to 0.40 mm. The maximum wear resistance of the nitrocarburised specimens is found up to 16 times higher than that of the age-hardened and 31 times higher than that of the solution treated ones. Microscopical observations revealed that the principal wear mechanisms of the nitrocarburized steel are micropolishing and microcutting.