Machinability of Ti-5Al-2.5Sn for electro-discharge machining: an experimental investigation

Abstract

Present work attempts to investigate machinability of Ti-5Al-2.5Sn for Electro-Discharge Machining (EDM). Extent of machinability is determined through material removal efficiency, tool wear rate, and surface integrity of the EDMed specimen of Ti-5Al-2.5Sn. Detailed analysis of surface morphology followed by study of surface topographical features including surface roughness, crack density, thickness of the recast layer, foreign material migration, metallurgical phase, residual stress, and micro-indentation hardness are carried out. Disappointing morphology is noticed for EDMed work surface at higher values of peak current as well as pulse-on time values. It is experienced that occurrence of surface cracks depends on recast layer thickness. As compared to ‘as received’ workpiece exhibiting compressive residual stresses, tensile stresses are found induced after performing EDM operation. Similar phenomenon is experienced in case of tool electrode. EDM operation improves microhardness of the machined surface. For Ti-5Al-2.5Sn, such improvement is nearly three times than that of ‘as received’ work material. During EDM operation on Ti-5Al-2.5Sn, titanium carbide is formed over tool as well as work surface. Formation of such hard carbides may degrade machining efficiency.