Microstructure and Tribological Properties of Microarc Oxidation Composite Coating Containing Cr2O3 Particles on TC4 Titanium Alloy

Using DC pulse mode, a microarc oxidation (MAO) composite coating containing Cr2O3 particles on TC4 titanium alloy was prepared by adding 1.5 g/L Cr2O3 microparticles into the Na2SiO3-(NaPO3)(6) electrolyte. The morphology and microstructure was analyzed by SEM, EDS and XRD. The dry wear behavior of the composite coating was investigated at room temperature. The results show that the surface pores of composite coating are filled with tiny Cr2O3 particles, and only a small amount of micropores can be observed on the coating surface. The composite coating has a large number of Cr2O3 phase besides rutile-TiO2, anatase-TiO2, Al2TiO5 phase and some amorphous compounds. The MAO composite coating containing Cr2O3 particles has smaller friction coefficient, lower wear loss and better wear resistance under the same wear condition. The composite coating only produces slight adhesive wear, almost without abrasive wear under the load of 10 N. However, the abrasive wear is somewhat intensified, and the loss of second-phase particles appears under the load of 50 N. Cr2O3 particles can reduce the friction coefficient and wear loss and improve the wear resistance of the composite coating by filling the pores of MAO coating, transferring load of Cr2O3 particles and the dispersion strengthening.