Synergistic effect of Y and Nb on the high temperature oxidation resistance of high Nb containing TiAl alloys

The synergistic effect of Y and Nb addition on the long time isothermal and cyclic oxidation behaviors of Ti–45Al–(6–9)Nb alloys containing 0.1–0.4 at.% Y was investigated in air at 900 °C. The results showed that the high temperature oxidation resistance was improved with an increase of Nb content. However, even 9 at.% Nb content was not sufficient to form the perfect Al2O3 layer. Scale spallation still occurred under hundreds of cyclic exposure. Y addition remarkably enhanced the long time oxidation resistance of high Nb containing TiAl alloys, and only a proper amount of Y addition could improve the long time oxidation resistance under both isothermal and cyclic oxidation. In this work, it was concluded that the principle of Y addition was choosing the minimum amount on the premise of meeting enough spallation resistance. Moreover, the optimum amount of Y changed regularly with the variation of Nb content. The reasonable addition of Y decreased from 0.4 at.% to 0.2 at.% with Nb content increasing from 6 at.% to 9 at.%. Based on synergistic effect of Y and Nb, the best oxidation resistance of alloys was achieved.