Abstract: The wear characteristics and wear mechanisms of plasma sprayed Al 2O 3 40%TiO 2 and Cr 2O 3 coatings on casting aluminum alloy (AC4C) were investigated. The bonding strength between the substrate and the coating was measured by scratch tester. The profile of worn coating surface and microstructure of the coatings were observed with SEM. The wear mechanism is discussed as well. The experimental results indicate that the wear resistance of Cr 2O 3 coating is greater than that of Al 2O 3 40%TiO 2 coating. The friction coefficient of Cr 2O 3 coating in sliding against SiC ceramic ball is lower than that of Al 2O 3 40%TiO 2 coating against the same counterface. It has also been found that the bonding strength, voids and porosities of the coating surface govern the friction and wear properties of the coatings. The wear mechanism of Al 2O 3 40%TiO 2 coating is mainly plastic deformation and delamination, whereas that of Cr 2O 3 coating is abrasive wear.