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

• Published in: Materials characterization 2022-07, Vol.189, p.111979, Article 111979
• Main Authors: Xu, Chi, Zhu, Minghao, Gao, Chuanli, Guan, Haohao, Wang, Xingping, Jin, Xiaoyue, Du, Jiancheng, Xue, Wenbin
• Format: Article
• Language: English
• Subjects: GDOES; High-temperature steam oxidation; TEM characterization; TiAl alloy; XRD
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2022.111979

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 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. •Multilayered structures were observed in γ-TiAl oxidized in water steam at 900–1200 °C.•Surface Rutile-TiO2 oxides with polyhedron shapes were observed.•A compact Ti3Al layer and mixtures of TiO2 and Al2O3 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.