The effect of Ta additions on the oxidation resistance of SPS-produced TiAl alloys

Abstract

The influence of the environment on the properties of TiAl alloys is a concern for elevated temperature applications. One element that stands out in improving the resistance of TiAl alloys against high-temperature oxidation is Nb. Nb promotes the activities of Al and favors the formation of a more protective Al2O3 surface oxide which subsequently stymies oxygen diffusion to the alloy. Ta is an equal replacement of Nb. Thus, this study aims to evaluate the effect of 0.8, 4, and 8 at. % Ta additions on the oxidation resistance of spark plasma sintered Ti-46.5Al (at. %) alloy. Isothermal oxidation tests were carried out for 360 and 100 h at 1123 and 1273 K respectively. Surface oxides examination include scanning electron microscopy with energy-dispersive X-ray spectroscopy and X-ray diffractometry. The results show that 4 and 8 at. % Ta additions significantly support the formation of an interconnected, non-porous Al2O3 layer at the metal-oxide interface. The continuous non-porous Al2O3 layer serves as a diffusion barrier which leads to superior oxidation resistance of the TiAl alloys.