Influence of Trace Y and Hf on the High-Temperature Oxidation Resistance of TiAl Based Alloys with High Nb Content

The interrupted oxidation behavior of Hf and Y micro-alloyed TiAl-based alloys with high Nb content at 900 degrees C in static air was investigated. The results show that the addition of 0.5%Hf (mol%, similarly hereinafter) has few effects on the oxidation resistance of the high-Nb alloy, the addition of 0.1%Y improves the oxidation resistance, while the combined addition of 0.1%Y and 0.5% Hf enhances the adherence of oxide scale but reduces the oxidation resistance. Oxidized samples were examined by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction analysis (XRD). It is found that the addition of 0.1%Y and the combined addition of 0.5%Hf and 0.1%Y promote the formation of continuous and compact Al2O3 oxide scale. The combined addition of 0.5%Hf and 0.1%Y into the high-Nb alloy results in the partial internal oxidation of the alloy, impairing the oxidation resistance of TiAl.