Effect of α-Al₂O₃ Additive on the Surface Micro-Arc Oxidation Coating of Ti6Al4V Alloy

α-Al₂O₃ nanoparticles can enter a micro-arc oxidation coating and participate in the coating-formation process through chemical reaction or physical-mechanical combination in the electrolyte. The prepared coating has high strength, good toughness and excellent wear and corrosion resistance. In this paper, 0, 1, 3 and 5 g/L of α-Al₂O₃ nanoparticles were added to a Na₂SiO₃-Na(PO₄)₆ electrolyte to study the effect on the microstructure and properties of a Ti6Al4V alloy micro-arc oxidation coating. The thickness, microscopic morphology, phase composition, roughness, microhardness, friction and wear properties and corrosion resistance were characterized using a thickness meter, scanning electron microscope, X-ray diffractometer, laser confocal microscope, microhardness tester and electrochemical workstation. The results show that surface quality, thickness, microhardness, friction and wear properties and corrosion resistance of the Ti6Al4V alloy micro-arc oxidation coating were improved by adding α-Al₂O₃ nanoparticles to the electrolyte. The nanoparticles enter the coatings by physical embedding and chemical reaction. The coatings' phase composition mainly includes Rutile-TiO₂, Anatase-TiO₂, α-Al₂O₃, Al₂TiO₅ and amorphous phase SiO₂. Due to the filling effect of α-Al₂O₃, the thickness and hardness of the micro-arc oxidation coating increase, and the surface micropore aperture size decreases. The roughness decreases with the increase of α-Al₂O₃ additive concentration, while the friction wear performance and corrosion resistance are improved.