Oxidation resistance of γ-TiAl based alloy Ti–45Al–8Nb coated with intermetallic Ti–Al–Cr–Y layers and EB-PVD zirconia topcoats at 950 °C in air

Samples of a high niobium bearing γ-TiAl based alloy were coated with intermetallic Ti–52Al–15Cr–0.4Y (in at.%) layers produced by magnetron sputtering. On some of the specimens thermal barrier coatings of 7 wt.% yttria partially stabilised zirconia were deposited using electron-beam physical vapour deposition. The oxidation behaviour of the coated Ti–45Al–8Nb (at.%) alloy with and without thermal protection was investigated at 950 °C under cyclic oxidation conditions in air. The 20 μm thick Ti–Al–Cr–Y layer exhibited excellent oxidation resistance at this exposure temperature associated with the formation of a thin continuous alumina scale. Lifetimes exceeding 1000 cycles of 1 h dwell time at 950 °C were determined for the TBC system consisting of zirconia topcoat and Ti–Al–Cr–Y bond coat.