Long-term oxidation behavior of silicon-aluminizing coating with an in-situ formed Ti5Si3 diffusion barrier on γ-TiAl alloy

In the present study, a novel silicon-aluminizing diffusion coating composed of uniform Ti (Al, Si)(3) phase was manufactured on gamma-TiAl alloy via post heat-treatment of cold-sprayed Al-40Si (wt.%) coating. The high temperature oxidation resistance of the diffusion coating was evaluated under 950 C for 1000 h. During the oxidation process, Ti5Si3 precipitations with network-like structure were shaped in the inner of the diffusion coating, which acted as getters for Ti and promoted the formation of Al2O3 scale. Meanwhile, an in-situ Ti5Si3 diffusion barrier was also formed, which inhibited the interdiffusion between the coating and substrate, especially the fast depletion of Al in the diffusion coating and thus improved the long-term oxidation resistance of gamma-TiAl. The microstructure evolution, formation of the in-situ diffusion barrier and high temperature oxidation resistance mechanisms of the diffusion coating were discussed in detail.