Composite microarc oxidation coatings containing Cu on titanium alloy

A soft and hard composite MAO coating was prepared by adding Cu particles to an alkaline phosphate-borate electrolyte to modify the MAO coating on titanium alloy. The effects of Cu particles on the thickness, structural features, and friction characteristics of the MAO coating were investigated. The MAO coating formed in Cu particle-free electrolyte mainly comprised rutile and anatase TiO₂. Cu and CuO were detected in the oxide coatings obtained in the electrolyte with Cu particles. The hardness of the coating prepared in the base electrolyte was approximately 420 HV, whereas that obtained in the electrolyte containing 2 g L⁻¹ Cu particles increased to 470 HV. While the friction coefficient of the base MAO coating exhibited significant fluctuations, the friction coefficient of the MAO coating containing Cu particles remained relatively stable. The MAO coating formed in the electrolyte containing 2 g L⁻¹ Cu particles demonstrated superior frictional performance, exhibiting a value approximately 3.6 times higher than the base coating. Cu particles enter the MAO coating through electrophoresis, mechanical agitation, and micro-melt adsorption to improve the compactness of the coating. Due to the excellent plasticity of Cu, the friction properties of Cu-containing MAO coating were enhanced.