Electro-Discharge Machining Performance of Nimonic 80A: An Experimental Observation

The present work reports electro-discharge machining (EDM) performance of superalloy Nimonic 80A. Experiments are conducted using a two-factor three-level full factorial design of experiment in consideration with two important electrical parameters: peak discharge current and pulse-on duration. Machining performance is evaluated in purview of material removal efficiency, rate of electrode wear, and surface integrity of the EDMed part product. Apart from morphological study, surface topographic measures including surface roughness, impact of surface cracking, white layer thickness, material migration, phase alteration, and micro-indentation hardness are studied in detail. Results of qualitative analysis on crater morphology are correlated with roughness value of the machined specimen. Effects of peak current and pulse-on time on influencing EDM performance indicators are also reported. An optimal parametric combination is determined for superior process performance. In doing so, utility theory is utilized to aggregate multi-performance characteristics to compute a unique index (called overall utility degree). The parametric combination which corresponds to maximum overall utility is assumed to be the best. It is determined that maximum material removal efficiency, minimal tool wear rate, and superior surface finish can be achieved at parameters setting: I p = 35 A and T on = 1000 µm. The said optimal setting corresponds to overall utility value of 6.53. Confirmatory test result yields: MRR = 9.05 × 10 −3 g/s, TWR = 1.2 × 10 −5 g/s, and R a = 14.1 µm at optimal setting.