Friction and wear behavior of ZrO2–Al2O3 composite coatings deposited by air plasma spraying: Correlation with physical and mechanical properties

In this paper, ZrO2–15 vol.%Al2O3 (denoted as ZA15) and ZrO2–30 vol.%Al2O3 (denoted as ZA30) composite coatings were deposited by air plasma spraying using nanoscale powders. Coating structures, thermal conductivities and mechanical properties were characterized. The friction and wear behaviors of two composite coatings were investigated using a ball-on-disc tribometer under dry sliding conditions with different sliding velocities and loads. In most studied conditions, ZA30 composite coating displays a better tribological performance, i.e. lower coefficient of frictions and wear rates, than ZA15. With respect to wear mechanisms, ploughs and especially fatigues of the interfacial adhesion between deposited splats and the following severe abrasiveness exerted by large debris contribute to the wear of the two coatings. Interestingly, the increase in nano-Al2O3 fraction (from 15% to 30%) seems to avoid or at least postpone the occurrence of the interfacial fatigue. The tribological behaviors of the two coatings were correlated to their physical and mechanical properties.