Wear mechanism of ion-sulphurization layer on steel under dry conditions

Sulphide layers were made on the surface of 1045 and 52100 steels by means of low-temperature ion-sulphurization technique. The tribological properties of sulphide layers under dry conditions in air were investigated on a reciprocating tester. The friction coefficient, endurance life and width of wear scar of sulphurized surfaces were measured. The morphologies and compositions of wear scars and wear debris were analyzed by scanning electron microscopy (SEM)+energy-dispersive X-ray spectroscopy (EDX). Finally, the wear mechanisms of sulphide layer were discussed. The results showed that the sulphide layer as a solid lubrication coating could adhere to the rubbing surfaces and impede the metallic contact. The friction coefficient of sulphurized surface was decreased and its wear-resistance was improved. High-hardness substrate could extend the endurance life of sulphide layer and reduce its wear. Moreover, the sulphide layer could promote the formation of oxide, which was beneficial to the shortening of running-in process.