Evaluation of surface-modified Ti-6Al-4V alloy by combination of plasma-carburizing and deep-rolling

Plasma surface diffusion processes such as plasma-carburizing and nitriding have been used to improve tribological properties of titanium and its alloys. However, the improvement of fatigue strength by these processes has not been successful due to brittleness introduced in the high-hardness surface layer and the disappearance of compressive residual stress and grain growth by heating. In this work, a Ti-6Al-4V alloy sample was plasma-carburized at a relatively low temperature to improve wear resistance, and then, deep-rolled to induce compressive residual stress. Scanning electron microscopy, optical microscopy, laser scanning microscopy, surface roughness tester, X-ray diffractometer, and micro-hardness tester were used to characterize the modified surface layer. The residual stress and work hardening state was analyzed by X-ray diffraction techniques. The effect of deep-rolling on fatigue strength and wear resistance of plasma-carburized Ti-6Al-4V alloy was also investigated. The fatigue properties and wear resistance of Ti-6Al-4V alloy modified by a combination of low-temperature plasma-carburizing and deep-rolling were significantly improved in comparison with those of the unmodified Ti-6Al-4V alloy.