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

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.