Performance optimization of a PTFE-coated electrode in electrochemical micromachining

Electrochemical micromachining (ECMM) is employed to machine Hastelloy C22 a nickel-based alloy, which is applied in chemical, food processing, and pharmaceutical industries. An L-18-mixed orthogonal array (OA) experiment plan was considered along with a polytetrafluoroethylene (PTFE)-coated electrode (CE), normal electrode, and mixed electrolyte (equal weight of sodium nitrate (NaNO3) + oxalic salt (C2H2O4)). Criteria importance through inter-criteria correlation and simple additive weighting methods were used to obtain the optimum levels of factors for higher machining rate, lower overcut, and conicity (K). According to the analysis, the optimal parameter combination was PTFE CE with 20 g/L mixed electrolyte, 8 V, 85% duty cycle, and 90-Hz frequency. An analysis of variance (ANOVA) results showed that the electrode type contributes 21.15% and 41.26% for machining rate (MR) and overcut (OC), respectively. The electrolyte concentration is the most significant factor for conicity, which contributes 64.32%.