Response surface modelling of tool electrode wear rate and material removal rate in micro electrical discharge machining of Inconel 718

Inconel 718 is a corrosion-resistant and high strength nickel-based alloy with wide range of applications includingcomponents for cryogenic tankage, liquid fueled rockets and casings for aircraft engines. The material is characterizedby high hardness, high temperature strength, low thermal conductivity and high strength causing it extremely difficult tomachine.

Micro-Electrical Discharge Machining (Micro-EDM) is a non-conventional method that has a potential toovercome these restrictions for machining of Inconel 718. Response Surface Method (RSM) was used for modelling thetool Electrode Wear Rate (EWR) and Material Removal Rate (MRR) with the input factors such as voltage (V), peak current(I on) and pulse on-time (Ton ).

The RSM analysis of variance results show that the main input factors’ pulse off-time and p onvoltage are significant in controlling the tool electrode wear rate at 95% confidence level. An increase in voltage from30 to 45 V and pulse on-time from 1 to 3 μs causes a linear decrease in EWR by 35%. Using response surface modeling, a3 3 minimum EWR of 12.3184 μm /min and a maximum MRR of 37.2151 μm /min is obtained at a current of 1.07 A, pulse ontimeof 4.44 μs, pulse off-time of 4.06 μs and voltage of 60 V.