Dry Sliding Wear Behaviour of Al2O3-Cr2O3 Coatings with Different Contents of Cr2O3

The effect of Cr2O3 on the friction and wear behaviour and wear mechanism of Al2O3-Cr2O3 composite coating sliding against ceramic ball with high hardness is still unknown. Atmospheric plasma spraying is used to deposit Al2O3-Cr2O3 composite coatings with different contents of Cr2O3 to reveal its influential mechanism. The experimental results show that Cr2O3 decreases the voids in the coating obviously. The relative alpha-Al2O3 gamma-Al2O3 content ratios in the composite coatings are larger than 37%. The micro-hardness of Al2O3-40%Cr2O3 composite coating increases by 48% compared with Al2O3 coating, the fracture toughness of which is twice as large as that of Al2O3 coating. Al2O3-40%Cr2O3 composite coating has lower friction factor and wear rates when the wear loads are 5 N, 10 N and 15 N than Al2O3 coating, their wear rates decrease by 60%, 85% and 79% compared with those of Al2O3 coating. But when the wear load is 20 N, Al2O3-20%Cr2O3 composite coating has lower friction factor than Al2O3 coating, its wear rate decreases by 50% compared with that of Al2O3 coating. The main wear mechanism of the coatings is micro-fracture. The wear resistance of the composite coating is determined by the content of Cr2O3 and wear condition. Microstructure, hardness, fracture toughness and coefficient of thermal conductivity are important factors affecting the wear resistance of Al2O3-Cr2O3 composite coating. The research results can provide guidance for the design and application of Al2O3-based coating with high wear resistance.