High Temperature Corrosion and Mechanical Properties of TiC-AlSi12 Composite Coating Fabricated on Ti-6Al-4V Alloy Substrate via High-Energy Mechanical Alloying Method

The TiC-AlSi12 composite coating was successfully prepared on Ti-6Al-4V substrate via mechanical alloying. the process parameters including powder weight ratio and milling duration of coating fabrication were optimized. The effects of annealing treatment on phase compositions, microstructure evolution, microhardness, wear resistance and high temperature oxidation resistance of the TiC-AlSi12 composite coating were investigated. The results show that the as-prepared coating had a composite structure. In which, the TiC reinforcing particles were uniformly dispersed in the AlSi12 matrix and the substrate/coating was well bonded. After annealing treatment, the coating exhibited a double layer structure, which included an inner Al₃Ti diffusion layer and an outer TiC-AlSi12 composite coating layer. The microhardness of the annealed coating is much higher than that of the as-prepared coating. Furthermore, the wear resistance of the annealed composite coating can be remarkably enhanced. The oxidation resistance of the TiC-AlSi12 composite coating was improved owing to the formation of the alloyed layer during annealing process. After 100 h oxidation, the oxidized coating shows a three-layer structure: the inner diffusion layer presented a sandwich structure composed of Si-rich layer + Al₃Ti layer + Si-rich layer; the middle layer represented a composite structure; the outer layer is a Al₂O₃ + SiO₂ + TiO₂ ceramic layer.