Multi-criteria optimization of square electrode wear in electrical discharge machining of Nimonic 90

Abstract

ABSTRACT High-temperature applications like turbine blades and braking discs employ Nimonic 90 superalloy, which is hard and wears electrodes during Electrical Discharge Machining. Under different EDM process conditions (current, duty cycle, pulse duration, and servo voltage), this study examines the wear behavior of square copper electrodes with 0.5, 0.6, 0.7, and 0.8 mm sizes. It focuses on cutting time (CT), electrode radius (ER), electrode wear length (EWL), and electrode taper angle Based on ANOVA, current was most important to ETA, EWL, pulse length to ER, and duty cycle to CT. Current and servo voltage increased ETA and EWL linearly, whereas duty cycle lowered CT. Micro-craters generated on electrode surfaces due to unstable discharges and skin reactions. After 225 µs pulse duration, the electrode radius decreased due to sparking instability. Experiments confirmed that the multi-objective decision-making approach (VIKOR) optimized process parameters, trade-off between ETA and ER maximization and EWL and CT reduction, and improved electrode performance. A new knowledge of micro-scale square electrode wear on Nimonic 90 may be utilized to improve settings and achieve high machining efficiency and electrode life in precision EDM.