Investigations on Effect of Electrode Polarity on Machining Performance of Ti-5Al-2.5Sn Alloy Using Electric Discharge Machining Process

In electrical discharge machining (EDM) process, electrode polarity plays an important role during machining operation. This paper addresses the issues of EDM utilizing the positive and negative tool-electrode polarity to explore the effects on the performance criteria such as material removal rate (MRR), tool wear rate (TWR), surface roughness (SR) and micro-hardness during machining of Ti–5Al-2.5Sn (GradeVI) Ti alloy. The Ti-5Al-2.5Sn alloy was machined using copper-chromium electrode with positive and negative polarity by varying the peak current and pulse-on-time, while the pulse-off-time was kept constant. The result of study suggests that reverse polarity improves the MRR, TWR, SR while normal polarity improves the surface micro-hardness. The peak current has the maximum affect on machining performance for both types of polarities. Further the migration of different elements and formation of compounds on the machined surface was investigated using EDX and XRD analysis.