Experimental study on surface quality and machinability of Ti-6Al-4V rotated parts fabricated by low-speed wire electrical discharge turning

Abstract

This paper firstly focused on analyzing the characteristics of surface damage in low-speed wire electrical discharge machining (LS-WEDM) and introducing the multiple cutting strategy into the LS-WEDT to improve the surface quality and minimize surface defects. Surface and sub-surface damages of Ti-6Al-4V (TC4) workpiece produced in LS-WEDT are discussed, which includes craters, cracks, surface alloying, surface composition, micro-hardness, and white layer. Experimental results indicated that the craters produced in LS-WEDTed surface are extended and very shallow. Although TC4 material has poor thermal conductivity, cracks can completely disappear by decreasing peak current in LS-WEDT, which differs from LS-WEDM. Comparing with LS-WEDMed surfaces, debris adhering on LS-WEDTed surface is very few due to good flushing condition and point contact discharge mechanism. The foreign elements of oxygen and copper are detected on LS-WEDTed surface, but the contents are less than LS-WEDMed surface. The micro-hardness of the heat-affected zone is much lower than substrate and the discontinuous white layer is obtained in LS-WEDT. The LS-WEDTed surface machined after finishing trim cut (FTC) is very smooth with invisible craters, and the white and heat-affected layers’ thickness are greatly reduced. Finally, practical machining is carried out via fabrication of the rotated micro-part and taper pin with diameter of 40 μm.