High temperature oxidation behaviour of TiAl–Cr–Nb–Mo alloys

Abstract

The oxidation behaviour of six different TiAl–Cr–Nb–Mo alloys was investigated by thermogravimetric method. Isothermal experiments were carried out at 900 °C and 1000 °C in air.The aim of this work was to evaluate the effect of aluminium and of other alloying elements on the oxidation behaviour of TiAl intermetallic alloys. The alloy's microstructure and composition as well as the composition distribution of the oxide scales were analysed by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffractometry (XRD). The study highlighted that the oxidation resistance of the considered TiAl-based alloys is strongly affected by its aluminium content, while it seems that an increase of Cr, Nb and Mo concentrations does not affect the oxidation behaviour of the alloy. Yttrium addition, at least in the tested quantity, has a detrimental effect since it promotes the formation of a TiO2–Al2O3 mixed oxide instead of a compact and thin alumina layer.