Tribological Properties of Plasma Sprayed TiC-Graphite Composite Coatings

Plasma sprayed TiC coating has now been a frequent choice for wear-resistant applications in extreme environments owing to its good comprehensive performance. Meanwhile, graphite is an excellent self-lubricating material. Here, spherical TiC-Graphite composite powders with different contents of graphite (1.25%, 2.5%, 5%, and 10% in mass) were fabricated by spray drying and vacuum sintering, and then TiC-Graphite composite coatings were prepared by atmospheric plasma spray (APS) technology. The phase composition, microstructure and mechanical properties of the coatings were characterized, and its tribological performances were evaluated. The results showed that the TiC-Graphite coatings were mainly composed of TiC and graphite phases. With the increase of graphite addition, the micro-cracks in the section and the roughness of the TiC-Graphite coatings increased while the hardness gradually decreased. Compared with low load, graphite had more significant effect on wear performance of the TiC coating under high load. Under the load of 50 N, wear rate of the TiC-Graphite coating first decreased and then increased, but the friction coefficient kept decreasing with the increase of graphite addition. When the graphite addition was 0.25%, the minimum wear rate of 0.67x10(-5) mm(3)/(N.m) was obtained, whereas the friction coefficient was 0.35, which were reduced by 72.4% and 27.8% compared with the pure TiC coating, respectively.