The Enhancement of Die Sink EDM Machining Efficiency Incorporating Micro-Flakes of Graphite Powder

The present article investigates the performance of powder-mixed die sink electrical discharge machining (PMEDM) under the influence of micro-flakes graphite (Gr) powder additive in dielectric (1.25 and 2.5 g/l of concentrations) during machining two workpiece materials of D2 steel and mild steel that are extensively employed alloys in the die and mold industry. Micro-flakes are chosen due to the necessity for fewer particles to fill the gap in the machining process, resulting in reduced pollution within the gap. The assessment of the PMEDM procedure’s results is conducted based on several parameters, including the material removal rate (MRR), electrode wear ratio (EWR), average surface roughness (Ra), morphology, machined surface elemental content and recast layer. The results indicated that Gr PMEDM process offers higher machining performance in terms of MRR, EWR and the machined surface quality compared to die sink EDM process in pure dielectric. The optimum concentration was found to be 2.5 g/l Gr powder mixed dielectric for both workpiece materials. Furthermore, it was specified that the chemical composition and mechanical properties of the workpiece considerably affect the performance of die sink EDM and PMEDM. Unlike what has been discussed previously in the literature, present study revealed that formation of micro-crack and its density as well as micro-defects on the machined surface is highly dependent on workpiece elemental composition and mechanical properties. The concentration of cracks was particularly higher in areas with higher Cr atomic concentration, which increased the crack density in D2 steel.