Formation of TiS and Ti4C2S2 in steel matrix composites prepared by the plasma transferred arc (PTA) technique using TiS2 and TiC powders

A powder mixture of TiS2 and TiC was used in order to produce a hard, self-lubricating composite coating on an AISI 1522H plain steel substrate, using the plasma transferred arc technique. The produced coating was 1400 μm thick. It consisted of three microconstituents (TiC large dendrites with branches of Ti4C2S2, peritectic TiS and TiS secondary eutectics), occupying 22.7±2 vol% of the ferritic matrix composite. The hardness of the coating was 645±32 HVN. Analytic microscopy and three-point bending tests verified the existence of Ti4C2S2. Pin-on-disc tests against an Al2O3 counterbody showed that TiS and Ti4C2S2 lower both the friction coefficient and the wear rate, compared to the corresponding values of TiC-AISI 1522H composite and of AISI 1522H plain steel.