Influence of Nano-ZrO2 Particles on the Microstructure and Properties of Micro-Arc Oxidation Coatings on TC4 Titanium Alloy

To enhance the surface hardness and wear resistance of TC4 titanium alloy, this paper systematically investigates the effects of voltage, time, and nano-ZrO2 particle concentration on the microstructure, phase composition, hardness, and wear resistance of ceramic coatings prepared by micro-arc oxidation (MAO) technology in silicate electrolyte systems. The results indicate that as the voltage increases, the pore size of the coating layer increases while the number decreases; as the time extends, the pore size first increases and then decreases. The addition of nano-ZrO2 particles can fill the micropores in the coating layer, significantly improving its compactness. XRD analysis reveals that the coating layer primarily consists of anatase TiO2, rutile TiO2, and SiO2. The addition of ZrO2 leads to the formation of monoclinic ZrO2 and ZrTiO4 phases. Hardness tests show that the highest hardness (449 ± 4 HV) is achieved at a voltage of 480 V and a duration of 3 min, and further increases to 547 ± 5 HV with the addition of 5 g/L ZrO2. Friction and wear experiments demonstrate that the friction coefficient decreases from 0.12 to 0.06 with the addition of ZrO2, significantly reducing the wear mass loss. The optimal process parameters are a voltage of 480 V, a duration of 3 min, and a ZrO2 concentration of 5 g/L, resulting in a composite coating with a dense surface, high hardness, and excellent wear resistance.