Effects of combined plasma-carburizing and shot-peening on fatigue and wear properties of Ti-6Al-4V alloy

The effects of combined plasma-carburizing and shot-peening on fatigue and wear properties of Ti-6Al-4V alloy specimen were investigated. Surface morphology and roughness, microstructure, compressive residual stress, work hardening state, and micro-hardness on the surface modified layer in the Ti-6Al-4V alloy specimen were measured and analyzed. The shot-peening effectively induces highly compressive residual stress and work hardening states on the surface layer of the plasma-carburized Ti-6Al-4V alloy specimen. Consequently, the fatigue life of plasma-carburized Ti-6Al-4V alloy specimen has been significantly improved by subsequent shot-peening. The cracks of both shot-peened and shot-peened carburized specimens initiated on the surface at higher applied stress levels. On the contrary, interior-originating fractures occurred at lower applied stress levels. Corresponding to this behavior, the S-N curves show the shape of two-step stages. The wear resistance of Ti-6Al-4V alloy specimen was also significantly improved by the hardness increase on the surface layer by combination of plasma-carburizing and shot-peening.