Effect of using SiC powder-added dielectric media during electro-discharge machining of Inconel 718 superalloys

Inconel 718 is a nickel-based superalloy widely applied in aerospace, automotive and defense applications. Low thermal conductivity, extreme high temperature strength, high work-hardening characteristics make them 'difficult-to-machine.' In order to improve EDM performance on Inconel 718, powder-mixed electro-discharge machining is reported herein. PMEDM is carried out by mixing SiC powder in the dielectric media in consideration with varied peak discharge current. As compared to conventional EDM, the morphology and topographical features of the machined surface including surface roughness, crack density, white layer thickness, metallurgical aspects (phase transformation, crystallite size, micro-strain and dislocation density), material migration, residual stress as well as micro-indentation hardness, etc., are studied. Additionally, effects of peak discharge on PMEDM performance features, namely material removal rate, tool wear rate, surface roughness, surface crack density, white layer thickness, are discussed and compared with conventional EDM.