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

摘要

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.