Multi-objective optimization of EDM machining of Waspaloy employing composite electrode

Electrical Discharge Machining (EDM) has emerged as an effective technique for machining difficult-to-cut superalloys such as Waspaloy, which are widely used in aerospace applications due to their superior mechanical strength and thermal stability but exhibit poor machinability under conventional processes. The present study focuses on enhancing EDM performance through the combined use of copper–graphite (Cu–Gr) composite electrodes and eco-friendly dielectric media, along with multi-objective optimization. Composite electrodes with graphite content 5 wt% were fabricated, and machining experiments were conducted under different process parameters, including discharge current, pulse-on time, pulse-off time, and inter-electrode gap. Machining performance was evaluated in terms of material removal rate (MRR), tool wear rate (TWR), and surface roughness (Ra), while surface integrity was analyzed using scanning electron microscopy (SEM). A TOPSIS-based multi-objective optimization approach was employed to determine the optimal machining conditions. The results indicated that discharge current and pulse-on time significantly influence MRR, with a maximum MRR of approximately 0.43 mm 3 /min achieved at 32 A and 30 µs. The minimum TWR of about 0.06 mm 3 /min was also observed at 8 A, indicating optimal discharge stability. Surface roughness was minimized to 1.8 μm using the CuGr5 electrode, while eco-friendly sunflower oil dielectric produced superior surface integrity with Ra as low as 1.013 μm and reduced recast layer thickness. Sensitivity analysis revealed non-linear parameter behavior with distinct optimal regions, and uncertainty analysis confirmed high experimental reliability with minimal variability. Multi-objective optimization identified the optimal condition with a performance index of 0.6213. The study demonstrates that the integration of composite electrode, bio-based dielectrics, and optimization techniques significantly enhances machining efficiency, surface quality, and sustainability in EDM of Waspaloy.