Abstract:A Ti(Al,Si)₃ diffusion coating was prepared on γ-TiAl alloy by cold sprayed Al-20Si alloy coating, followed by a heat-treatment. The isothermal and cyclic oxidation tests were conducted at 900 °C for 1000 h and 120 cycles to check the oxidation resistance of the coating. The microstructure and phase transformation of the coating before and after the oxidation were studied by SEM, XRD and EPMA. The results indicate that the diffusion coating shows good oxidation resistance. The mass gain of the diffusion coating is only a quarter of that of bare alloy. After oxidation, the diffusion coating is degraded into three layers: an inner TiAl₂ layer, a two-phase intermediate layer composed of a Ti(Al,Si)₃ matrix and Si-rich precipitates, and a porous layer because of the inter-diffusion between the coating and substrate.

Key words: Ti(Al,Si)₃ diffusion coating; γ-TiAl alloy; cold spray; heat-treatment; high temperature oxidation