Wear Mechanism and Lubrication State of Plasma-Sprayed Cr_2O_3 Coating Against SiC Bulk Under Water Lubrication

Friction and wear properties of plasma-sprayed Cr2O3 coating against SiC bulk at different loads and sliding velocities under water lubrication were investigated. Worn surfaces and wear debris were examined by means of SEM and XPS. The aim was to reveal wear mechanism and lubrication state of the pairs under different testing conditions. The results obtained indicate that friction coefficients and wear coefficients for Cr2O3 coating and SiC bulk pairs are quite low. Wear mechanism of Cr2O3 coating is microfracture along the borders of pores and plastic deformation, and wear mechanism of SiC bulk is formation of SiO2 through tribochemical reaction and dissolution of SiO2 in water. Wear mechanisms of Cr2O3 coating and SiC bulk are steady upon normal loads and sliding velocities. The pairs are in boundary lubrication state at low velocities and high loads and in partial elasto-hydrodynamic lubrication either at high velocities or at low loads.