Performance evaluation and optimization of powder mixed EDM of Inconel 718 using composite electrodes and the VIKOR method

Traditional electrical discharge machining (EDM) is characterised by a low material removal rate (MRR), a high tool wear rate (TWR), and poor surface finish (Ra), which restricts its suitability for machining nickel-based superalloys. This research examines Powder Mixed Electric Discharge Machining (PMEDM) of Inconel 718 using aluminium oxide (Al 2 O 3 ) of 1–5 g/L added to the dielectric medium to improve machinability and discharge characteristics along with graphite (5%) reinforced aluminium composite electrode to enhance thermal and electrical performance. Microstructural analysis confirmed uniform graphite distribution, complemented by reduced density and improved thermal conductivity. The effects of peak current (A), pulse on time (Ton), pulse off time (Toff), Spark gap control and Powder Concentration on MRR, TWR, and Ra were analysed using a L25 Taguchi-based experimental design. VIKOR, a multi-criteria decision-making (MCDM) method, was used to rank experimental alternatives and simultaneously identify the best machining parameter combination. The optimised machining conditions were achieved at 15 A, 2 µs Ton, 10 µs Toff, 6 mm spark gap, and 3 g/L powder concentration, resulting in enhanced machinability, improved MRR, reduced TWR, and superior surface finish.