Evaluating surface roughness and hardness of Inconel 718: A comparative study of traditional EDM oil versus graphite mixed EDM oil

In this experimental research, the surface roughness and Hardness of Inconel 718 material were studied by varying four input process parameters in Electro Discharge Machining (EDM) and Powder Mixed Electro Discharge Machining (PMEDM). The input parameters are discharge current, pulse-on time, pulse-off time, and flushing pressure. Two dielectrics are used in this work. One is ST EDM oil, and the second is Graphite mixed EDM oil. The study is specifically designed to determine the optimised values of input process parameters for the best output responses, including Surface Roughness (SR) and Hardness. This experimental research elaborates on a comparative study between the two dielectrics. The One Factor at a Time (OFAT) approach is used to determine the approximate range values. Range values of discharge current fixed 7.80–10.92 A, 500–1000 µs range values are fixed for pulse on time, 150–300 µs range value selected for pulse off time, 0.084–0.140 bar fixed for flushing pressure to record low values of SR and average values of Hardness.