Analysis and evaluation of heat affected zones in electric discharge machining of EN-31 die steel

In this paper investigations are conducted on the machining of EN-31 die steel with different electrode materials (copper, brass and graphite) with electrical discharge machining (EDM) process. This study presents the analysis and evaluation of heat affected zones (HAZ) of the workpiece surfaces machined using different tool electrodes by EDM. The kerosene oil of commercial grade has been used as dielectric fluid. The effect of various important EDM parameters such as pulse duration, peak current and discharge gap voltage has been investigated to yield the responses in terms of material removal rate (MRR) and surface roughness (SR). Further the detailed analysis of heat affected regions has been carried out by using scanning electron microscopy (SEM) and optical microscopy (OM). Experimental results indicate that copper as a tool electrode shows a good response towards MRR, whereas brass gives superior surface finish as compared to other tool electrodes. From the microstructural analysis study it has been observed that heat affected zone is much deeper in the specimen machined by graphite electrode as compared to other tool electrodes.