Surface properties of a γ-based titanium aluminide at elevated temperatures

Nano indentation tests have been performed to investigate the mechanical properties of a gamma based titanium aluminides (Ti–48Al–2Nb–2Cr–B) at temperatures ranging from 25 to 400 °C. Indention and nano-scratch test have also been carried out after the samples were cooled down to room temperature to evaluate the effect of higher temperature exposure on the surface properties of the aluminide. The results show that the surface hardness and elastic modulus of the investigated intermetallics are higher at elevated temperatures as compared to those measured at room temperature. XPS analysis reveals that mixed oxides of TiO2, Al2O3 and Nb2O5 have formed on the sample surface during the high temperature indentation tests. The Ti:Al ratio obtained from the integrated peak area of Ti 2p and Al 2p spectra decreases with increasing temperature and reaches a minimum value at 400 °C, indicating surface enrichment of aluminium oxide. The oxide layer formed at the higher temperature improves room temperature abrasive wear resistance of the titanium aluminide, as proved by the nano scratch test.