The friction and wear characteristics of low-pressure plasma-sprayed ZrO2-BaCrO4 composite coating at elevated temperatures

The friction and wear characteristics of low-pressure plasma-sprayed (LPPS) ZrO2-BaCrO4 (ZB) coating at elevated temperatures have been studied using a high-temperature reciprocating wear tester. The ZB coating exhibits a less porous, alternative lamellar structure and a better splat spreading as contrasted to the porous yttria partially stabilized zirconia (YPSZ) coating. The hardness of the ZB coating is 276–435 HV, which is much lower than that of the YPSZ coating (650–727 HV). The ZB coating shows distinct improvements in wear resistance and frictional characteristics at elevated temperatures, as contrasted to the YPSZ coating. At room temperature, the friction coefficient of the ZB coating against sintered Al2O3 is quite high and exhibits an increase in trend with increasing load. At above 300 °C, the ZB coating exhibits low friction and mild wear. But for the YPSZ coating, the situation is reversed with increasing temperature. Brittle fracture and delamination featured by large wear sheets are considered as the dominated wear mechanisms of the ZB coating at low temperatures. However, plastic deformation, formation and transfer of BaCrO4 lubrication films appears as the main wear mechanisms at elevated temperatures. BaCrO4, acting as an effective solid lubricant at above 300 °C, reduces the friction and wear of the coating.