Microstructural characterizations of γ-TiAl alloy after high-temperature steam oxidations at 900, 1000, 1100 and 1200 °C

Abstract

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, and multilayered structures were observed. A compact Ti 3 Al layer was formed next to the TiAl substrate. An outer layer of TiO 2 and Al 2 O 3 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 Al 2 O 3 grains extend inward into the Ti 3 Al 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. • Multilayered structures were observed in γ-TiAl oxidized in water steam at 900–1200 °C. • Surface Rutile-TiO 2 oxides with polyhedron shapes were observed. • A compact Ti 3 Al layer and mixtures of TiO 2 and Al 2 O 3 oxides were identified. • A transformation of the Ti-, Al-oxide mixture morphologies happened from 900 to 1200 °C. • An interior H concentration peak was ascribed to the metal-water reaction.