Critical assessment of the cyclic oxidation resistance of the aluminized Ti-48Al-2Cr-2Nb TiAl alloy at 700 °C and its impact on mechanical properties

Surface and Coatings Technology 406 (2021), 126646, DOI: 10.1016/j.surfcoat.2020.126646

A comparative investigation of the oxidation resistance at 700 °C and the mechanical properties of the uncoated and pack aluminized Ti-48Al-2Cr-2Nb (in at. %) TiAl alloy was conducted in this study. Cyclic oxidation tests were performed for up to 1000 h in dry synthetic air. A mixed TiO₂/Al₂O₃ scale formed on the surface of the uncoated TiAl alloy while a thin Al₂O₃-rich scale covered the surface of the aluminized samples. While stable α–Al₂O₃ together with rutile was detected on the surface of the uncoated samples, the oxide scale grown on coated samples consisted of α–Al₂O₃ and metastable θ–Al₂O₃. Four-point bending tests of the exposed samples at room temperature showed a progressive decrease in fracture stress and strain values of the uncoated alloy. The corresponding values of the aluminized samples were lower in the as-coated condition compared to the uncoated alloy, but then showed almost no further deterioration with increasing exposure.