Tribo-layer and its role in dry sliding wear of Ti–6Al–4V alloy

Dry sliding wear tests were performed for Ti–6Al–4V alloy under a load of 50–250 N at 25–500 °C on a pin-on-disk elevated temperature tester. Worn surfaces and subsurfaces were thoroughly investigated for the morphology, composition and structure of tribo-layers. Ti–6Al–4V alloy could not be considered to possess poor wear resistance at all times, and presented a substantially higher wear resistance at 400–500 °C than at 25–200 °C. The tribo-layer, a mechanical mixing layer, was noticed to exist on worn surfaces under various conditions. High wear rate at 25–200 °C was ascribed to no protective tribo-layer containing no or trace tribo-oxides. As more oxides appeared in the tribo-layers, they presented an obviously protective role due to their high hardness, thus giving a reasonable explanation for high wear resistance of Ti–6Al–4V alloy at 400–500 °C.