Performance Evaluation of Electrode Materials in Electric Discharge Deep Hole Drilling of Inconel 718 Superalloy

In the present study, electric discharge deep hole drilling of Inconel 718 was experimented with three different commercial tube electrodes viz., copper, copper-tungsten and graphite. The pertinent process parameters selected for the study were peak current, pulse on-time, duty factor and electrode rotational speed. The machining performance was investigated by analysing Material Removal Rate (MRR), Electrode Wear Ratio (EWR) and Surface Roughness (SR). The experiments were planned according to Response Surface Method (RSM) and Central Composite Design (CCD). Through holes of diameter around 3.0mm and 25mm depth were drilled. Experimental data was fitted and regression analysis was done. The experimental results indicated that copper electrode outperformed copper-tungsten and graphite electrodes with regard to MRR and SR. Further, the EWR was high in copper electrode followed by copper-tungsten and graphite electrodes. Among the three electrode materials tested, copper is the best choice of electrode material with respect to high MRR and low SR.