Microstructure and tribological properties of laser clad NiO/Al₂O₃ self-lubrication wear-resistant ceramic matrix composite coatings

NiO/Al₂O₃ self-lubricating wear resistant ceramic matrix composite coatings with a microstructure composed of Al₂O₃ primary dendrites and the inter-dendritic film-like NiO solid lubricant phase were fabricated on the Al₂O₃ ceramic substrate by laser cladding with Al₂O₃-NiO ceramic powder blends as new materials. Compared with the laser clad monolithic Al₂O₃ ceramic coating, the laser clad NiO/Al₂O₃ self-lubricating composite coating has excellent wear resistance and low friction coefficient under the room-temperature dry sliding, although the hardness of the latter is much lower than that of the former. In order to reduce the friction coefficient and wear weight loss, the optimum content of NiO self-lubricant in the composite coating is approximately 40 wt.%.