Surface Modification of Ti-6Al-4V by Gas-liquid Mixed EDM

Ti-6Al-4V alloy is widely used in many fields due to its excellent properties. However, its further applications is limited by its low hardness and poor wear resistance. In this paper, gas-liquid mixed electrical discharge machining (EDM) process was applied for surface modification of Ti-6Al-4V alloy. The multi-hole electrode was adopted to flow nitrogen to mix nitrogen with special spark oil. The effect of different parameters (peak current and pulse duration) on surface morphology, cross section morphology, micro hardness and wear resistance were investigated. The results indicated that the gas-liquid mixed EDM process has better performance on sample surface with fewer pores and shallow craters. A continuous and thick recast layer was obtained by gas-liquid mixed EDM process and N element was migrated to the sample surface from nitrogen gas. The XRD results demonstrated that TiN hard phase was formed on the sample surface, thus the micro hardness was nearly three times higher than that of the matrix, reaching 1329.5HV, and the wear resistance is improved accordingly. The surface of Ti-6Al-4V alloy was modified by gas-liquid mixed EDM process.