High-temperature corrosion of mechanically alloyed Cr-AlSi12 composite coatings on Ti-6Al-4V alloy substrate

In the present work, the Cr-AlSi12 composite coatings were successfully synthesized on the Ti-6Al-4V alloy substrate by using the mechanical alloying method. The effects of raw Cr particle size, milling duration, and annealing treatment on the preparation of the coatings were investigated. The as-prepared coatings consisted of the inner coating layer with coarse Cr particles and the outer coating layer with refined and highly homogenized structure. The annealing treatment could promote element diffusion and alloying; it was favorable to the densification and oxidation resistance of the coatings. There is a highly densified alloyed layer in the outer coating. The annealed coating showed excellent friction and wear resistance. After the oxidation process, the annealed coating showed the best high-temperature oxidation resistance. The oxidized annealed coating exhibited four layers, which included the thin Al2O3 oxide film, the homogenized alloyed layer, the composite layer consisted of Al2O3 and coarse Cr particles surrounded by alloyed layer, and the Al3Ti diffusion layer. This was favorable to the improvement of high-temperature oxidation resistance. The oxidation process of the annealed coating was elaborated.