Nanoindentation and nanoscratch properties of a thermal oxidation treated γ-TiAl based alloy

Titanium aluminides have low surface hardness and poor tribological properties, which could limit their applications in such areas where contact and wear are involved, e.g. valves in an auto-engine. In this study, a γ-based titanium aluminide has undergone a series of thermal oxidation processing to produce an oxide layer on the aluminide surface. The mechanical properties, the scratch resistance, the deformation and the damage behaviours of the oxide layer have been evaluated using nanoindentation and nanoscratch techniques. It has been found that the oxide layer on titanium aluminide surface is multi-layered oxide consisting of predominant TiO2 and Al2O3. Due to increased surface hardness (H) and elastic modulus (Er) as well as reduced Er / H ratio, the surface treatment has improved the scratch resistance and micro-abrasive wear resistance of the titanium aluminide. The nanoscratch properties of the treated titanium aluminide have been correlated with the scratching load, the hardness and the Er / H ratio of the surface oxide layer.