Effect of softening in near-surface region on wear transition of Ti-6Al-4V alloy at elevated temperatures

Dry sliding wear testing of Ti-6Al-4V alloy was performed at temperatures of 20, 100 and 200°C to investigate it's wear transition mechanism. Each wear rate-applied load curve demonstrated a mild wear stage and a severe wear stage. Morphology and composition of worn surface were analyzed using SEM and EDS techniques. When wear transformed from the mild wear stage to severe wear stage, sever plastic deformation wear mechanism played a dominant role. The analysis of subsurface microstructures revealed that a fine grain microstructure zone was formed beneath the surface after mild to severe wear transition, correspondingly a soften effect was detected in the fine grain microstructure zone by microhardness measurement. Therefore, it is considered that the softening in the near surface is the main reason for mild to severe wear transition.