Unlubricated friction and wear behavior of low-pressure plasma-sprayed ZrO2 coating at elevated temperatures

The unlubricated friction and wear behavior of low pressure plasma-sprayed (LPPS) ZrO2 coating were studied by using a standard SRV wear test system with reciprocating motion against sintered Al2O3 ceramic sphere from room temperature to 800 degreesC. Microstructural observations showed that ZrO2 splats appeared as fine lamellae structures together with small amounts of Al2O3 and SiO2 inclusions with different gray levels in the back-scattered electron (BSE) mode. The friction and wear of ZrO2 coating showed a strong dependence on temperature, changing from a low to a high wear regime with the increase of temperature. ZrO2 coating exhibited low friction and wear at room temperature and 200 degreesC. However, when temperature was increased to above 400 degreesC, friction and wear of the coating increased rapidly and reached a maximum at 600 degreesC together with significant noise and distinct vibration caused by severe surface fracture. Intersplat fracture and surface fatigue of ZrO2 splats were demonstrated to be the dominated wear mechanism at room temperature. Delamination caused by subsurface crack propagation and inclusion cracking was the dominated wear mechanism at 600 degreesC. Above 700 degreesC, recrystallization and abrasive wear in the form of removal of fine ZrO2 grains became the dominated wear mechanism together with local plastic flow and viscous deformation. (C) 2001 Elsevier Science Ltd and Techna S.r.l. All rights reserved.