Sliding wear behavior of ceramic, plasma sprayed on casting aluminum alloyagainst SiC ball

The wear behavior of Al2O3-40% TiO2 and Cr2O3 deposited on a casting alumin um alloy (ASTM A356) by plasma spray against an SiC ball was investigated. It was found that the voids and porosities of the coating surface generated cracks. As the tensile stresses in the coating increased with an increased friction coefficient, the columnar grain of the coating fractured at the c ritical stress point. It was also found that the cohesiveness of the splats and porosity of the surface both played a role in the wear characteristics . It is suggested that the thermal expansion mismatch of the substrate and coating plays an important role in the wear performance. Tensile, compressi ve, and thermo-mechanical stress may also occur due to this same thermal ex pansion mismatch of the substrate and coating. Crack propagation above the interface was observed with a SEM.