Oxidation resistance of Ti-48Al(at.%) coupons coated with Al-21Ti -23Cr(at.%) film has been assessed by isothermal oxidation test at a temperature range of 800℃ to 1000℃. The coatings of fine grains were prepared by RF magnetron sputtering with the resulting thickness of 10㎛. the TiAl coupons coated at 200W, 6mTorr, and 300℃ have shown the best oxidation resistance. The parabolic stage continued for 100hr at all tested temperature range in isothermal oxidation test. This oxidation manner was attributed to the formation of protective scale at the surface of a Al-21Ti-23Cr film. The activation energy for parabolic oxidation in the present study was almost unanimous with the reported values for the oxidation of alumina-former coatings, especially CoCrAlY coating. In addition, usually the useful life span of antioxidation coatings is limited, to some extent, by the interdiffusion between the coating and the substrate. So, in this study, titanium aluminum nitride ($Ti_{0.67}$,$Al_{0.33}$)N layer was introduced as a diffusion barrier. In this case, the oxidation rate slightly increased though the nitride layer interfered with the interdiffusion of Al at 800℃. But multilayer coating was not effective at 1000℃ because the oxidation rate accelerated after 20hr in isothermal oxidation test. Such difference of oxidation behavior between a Al-21Ti-23Cr/TiAl and a Al-21Ti-23Cr/(Ti,Al)N/TiAl was suggested to exist due to a high oxygen diffusion path in a Al-21Ti-23Cr/(Ti,Al)N coating because this coating has a columnar structure.
