Comparison of performance characteristics of dielectrics oil and graphite-mixed machining of EN24 using electric discharge machining process

Materials machined using electro discharge machining (EDM) generally require longer processing times because of slower metal removal. Improving the material removal rate (MRR) often depends on modifying the dielectric medium or employing hybrid EDM techniques. In this study, standard EDM oil and graphite powder-mixed EDM (PMEDM) oil were compared to enhance the machining performance of high-strength EN24 alloy steel. EN24, composed of nickel, chromium, and molybdenum, is widely used for shafts, axles, and heavy-duty offshore components due to its high ductility and tensile strength. Graphite-mixed dielectrics are reported to improve MRR because graphite particles increase spark conductivity and thermal efficiency in the discharge gap. Two sets of experiments were performed: one using standard EDM oil and the other using EDM oil mixed with 2 g/L of graphite powder (0.25 µm size). Machining trials were carried out to evaluate key performance indicators such as MRR, tool wear rate (TWR), overcut, and surface roughness (SR). Comparative analysis revealed that the graphite-mixed dielectric enhanced MRR, TWR, and overcut by 43.14%, 12.27%, and 23.13%, respectively, while SR improved by 7.9%. Overall, the results demonstrate that graphite-PMEDM oil significantly improves the machining efficiency and surface characteristics during EDM of EN24 steel.