A microstructural study of the early-stage high-temperature steam oxidation behavior of γ-ΤiAl alloy

摘要

A microstructural characterization of the early -stage steam oxidation behaviors of a γ -TiAl alloy was performed. The γ -TiAl alloy samples were oxidized in water steam at 900, 1000, 1100, and 1200° C for 1 h. The steam oxidation dynamic curves were compared. Multiple characterization techniques, including the XRD, SEM and TEM couple d with EDXS, and GDOES were employed to analyze the microstructures induced by the high temperature steam environment at different temperatures. Multilayered structures were formed. A compact Ti3Al layer was formed next to the TiAl substrate. An outer layer of TiO2 and Al2O3 mixed oxides was observed, where the oxide grains are transferred from long -columnar grains at 900° C to the randomly scattered grains at 1200° C. The ribbon shaped Al2O3 grains extend inward into the Ti3Al layer at 1100° C and above. An intermediate layer with dark speckles and bright background was formed at 1200° C. Fine pores existed in the near-surface areas of the oxide scales for all specimens. The mechanisms for the steam oxidation induced microstructures, water vapour and the temperature effects were discussed in details.