Parametric study on electrode wear rate, microhardness and microstructure behaviour in electrical discharge machining of AISI 304 stainless steel

Abstract

Electrical Discharge Machining (EDM) is widely applied for machining hard metallic materials due to its capability to produce complex geometries with extreme precision. However, machining performance and efficiency are significantly influenced by surface integrity and electrode wear characteristics. In this investigation, effect of current (I), pulse-on time (T on ), and pulse-off time (T off ) on electrode wear rate (EWR) and microhardness (MH) during EDM of AISI 304 stainless steel using copper electrode were systematically examined. A response surface methodology (RSM)-based central composite design was employed to design and analyse the experiments and develop predictive model. Analysis of variance (ANOVA) revealed that ‘I’ was dominant factor, contributing 85% to EWR and 61% to MH. The minimum EWR of 0.0092 g/min was achieved at 6A, 30 μs, 7 μs, whereas the maximum MH of 473.58 was obtained at 6A, 30 μs, 9 μs. The developed regression models exhibited excellent predictive accuracy, with R 2 values of 99.88% and 96.39%, respectively for EWR and MH. EWR increased with increasing in ‘I’, but decreases with increasing T on and T off . Conversely, MH increased with increasing T on and T off , whereas higher ‘I’ leads to decrease MH. Scanning electron microscopy (SEM) revealed formation of deeper craters, a thicker recast layer, and microcracks under greater energy conditions, indicating significant microstructural modification of the machined surface. The developed models and microstructural analysis offer practical framework for optimizing EDM parameters to reduce electrode wear while enhancing hardness and integrity in machining of AISI 304 stainless steel.