Performance study of gas-assisted electric discharge machining on carbon–chromium die steel

Abstract

The present study focuses on studying the effect of liquid cum gas as dielectric during Electric Discharge Machining (EDM) of carbon chromium die steel. In this work, a hybrid process of EDM employing both liquid (commercial kerosene oil) and gas (compressed helium gas) as dielectrics in die-sinking EDM has been explored. Experimentation has been done to the study effect of process factors like discharge current, pulse on time, duty cycle, tool rotation and discharge gas pressure on material removal rate (MRR), electrode wear ratio (EWR) and surface roughness (SR). Further, a comparative study of conventional EDM with liquid dielectric and hybrid EDM with liquid cum gaseous dielectric has been performed. It has been found that high MRR, low EWR and low SR are obtained when liquid cum gaseous dielectric was used as compared to conventional EDM with liquid dielectric. Analysis of surface morphology reveals that the formation of recast layer and surface cracks is less on specimen machined with liquid cum gaseous dielectric with respect to specimen machined with conventional liquid dielectric. The results show that the use of compressed helium gas has a positive impact on the machining performance. Superior surface finish and higher MRR reveal the possible implementation of the process in modern machining.