The isothermal and cyclic oxidation behaviour of Ti-48Al-2Cr at 700°C

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Abstract
The effect of the microstructure on the isothermal and cyclic oxidation behaviour of the intermetallic Ti–48A1–2Cr (at.%) alloy was investigated at 700°C in air up to 3000 h. Different microstructures, i.e., duplex, near gamma, nearly lamellar, and fully lamellar, obtained by various heat treatments, were used. Results of thermogravimetry showed a good oxidation resistance at 700°C against both isothermal and cyclic oxidation. The growth rate of the oxide scale, as well as its composition, structure and morphology showed no major relation to the microstructure of the base material. After equal exposure times, cyclic oxidation induced a higher oxidation rate compared to isothermal oxidation. Oxidation of Ti–48A1–2Cr in air, initially resulted in the formation of α-A12O3, TiO2 (rutile), Ti2A1N and TiN, with the latter two near the scale/substrate interface. After longer exposure times, the mixed corrosion scale was overgrown by fast growing TiO2. The oxide scales, formed under isothermal as well as under cyclic conditions, were uniform.