Influence of doping graphite on microstructure and tribological properties of plasma sprayed 3Al2O3-2SiO2 coating

With the combination of self-lubricating ability and mechanical property, high-performance ceramic-graphite composite coatings are potential candidates for machine components. Mullite/nickel cladded graphite (Ni-graphite) composite coatings with different content of graphite were fabricated by air plasma spraying technique. Results show that doping a suitable amount of Ni-graphite could greatly reduce the defects of mullite coating without significant decrease of their hardness. With the formation of re-graphitization lubricating film on friction surface, the friction coefficient of composite coating with 20 wt% Ni-graphite was observed to be 0.28, which was approximately 52% lower than that of pure mullite coating, and its wear rates was 4.15 times lower than that of pure mullite coating.