Machinability, parametric and surface behaviour investigation on INC-625 superalloy using electrical discharge machining

The study details how the machinability behaviour of INC-625 superalloy is influenced by the Electrical discharge machining (EDM) parameters with a graphite electrode. The surface roughness (SR) and material removal rate (MRR), the quality of the machined surface is examined by the manipulation of parameters such as servo voltage (SRV), applied current (APC), angle of cut (AGC), pulse off time (PFT), and pulse on time (PNT). Response surface methodology-central composite design is used in the execution of L42 machining trials. Multi-response optimisation using desirability analysis identified the optimum machining conditions resulting in a maximum MRR of 3.28 mm³/min and minimum SR of 4.21 µm, with improvements of 1.21% and 0.9%, respectively. ANOVA revealed that servo voltage was the most influential factor, contributing 77.33% towards MRR and 80.01% towards SR. Experimental validation confirmed the model reliability with low prediction errors of 1.52% for MRR and 0.95% for SR. Surface characterisation using Scanning Electron Microscopy (SEM), 3D profilometry and Atomic Force Microscopy (AFM) revealed the crater formation, recast layer characteristics, and surface morphology. The study provides a comprehensive framework combining statistical modelling, multi-response optimisation, and multi-scale surface characterisation for improved understanding and control of EDM performance in INC-625 machining.