Tribological characteristics of low-pressure plasma-sprayed A1 2O 3 coating from room temperature to 800 °C

Abstract

The tribological characteristics of low-pressure plasma-sprayed (LPPS) Al 2O 3 coating sliding against alumina ball have been investigated from room temperature to 800 °C. These friction and wear data have been compared quantitatively with those of bulk sintered alumina to obtain a better understanding of wear mechanisms at elevated temperatures. The friction and wear of Al 2O 3 coating show a strong dependence on temperature, changing from a mild to a severe wear regime with the increase of temperature. The coefficient of friction at room temperature is approximately 0.17 to 0.42, depending on applied load. The tribochemical reaction between the coating surface and water vapor in the environment and the presence of the hydroxide film on the Al 2O 3 coating reduce the friction and wear at room temperature as contrasted to those of bulk sintered alumina. At intermediate temperatures, from 400 to 600 °C, the friction and wear behavior of Al 2O 3 coating depends on the inter-granular fracture and pull-out of Al 2O 3 grains. At above 700 °C, formation and deformation of fine grain layer, and abrasive wear in the form of removal of fine alumina grains further facilitate the friction and wear process of Al 2O 3 coating.