Friction and wear behaviors of Al₂O₃–13 wt%TiO₂ coatings

Nanostructured and conventional Al₂O₃–13 wt%TiO₂ coatings were manufactured by air plasma spray. Friction and wear behaviors of coatings were investigated at room and elevated temperatures using an SRV wear test machine. The nanostructured coating has “two regions” microstructure, while the conventional coating has typical layered microstructure with obvious interfaces among splats. The coefficient of friction decreases with rising of temperature because of the formation of tribo-layer at elevated temperatures. The wear resistance of the nanostructured coatings is higher than that of the conventional coating, and the wear threshold of applied load is 30 N for conventional coating and 40 N for nanostructure coating. The wear resistance difference is related to the “two regions” microstructure of nanostructure coating, which could blunt or branch the cracks propagation. In our test ranges, the wear rates rising are more sensitive with the applied wear load rising than with the temperature rising.

Extensive tribo-layer area emerged from the wear scar of nanostructure coating obtained at 500 °C. The tribo-layer area is compact and smooth and plays an important role to reduce the coefficient of friction. The elevated temperature enhanced the formation of tribo-layer, which lead to the decreasement of friction coefficient with rising of temperature.