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.

Electro-discharge machining (EDM) is very promising non-traditional machining route to cut 'difficult-to-machine' materials like Inconel 718 superalloy. However, low material removal efficiency and inferior surface integrity restricts EDM application on Inconel 718. In order to improve EDM performance, multi-walled carbon nanotube (MWCNT) dispersed into kerosene is explored as dielectric media. Experiments are conducted by varying peak discharge current with a fixed concentration of MWCNT (0.5 g/l) added to kerosene. EDM performance is assessed in purview of material removal efficiency, tool wear rate, and surface integrity (morphology and topography) of the EDMed specimen. Apart from morphological study, surface topography including surface roughness, crack density, recast layer thickness, metallographic alteration, residual stress, and micro-indentation hardness of the machined specimen are studied in detail. It is concluded that as compared to conventional EDM, use of MWCNT-mixed dielectric media (0.5 g/l) significantly improves machining performance.

Due to increased demand of dimensional accuracy and high precision of manufactured parts, wire electrical discharge machining (WEDM) became very popular, especially for 'difficult-to-cut' materials like titanium alloys. Grade 5 Ti alloy (Ti-6Al-4V) has enormous application in aerospace and biomedical fields. WEDM performance of Ti-6Al-4V is somewhat restricted due to its poor thermal conductivity, formation of hard and brittle carbide-/oxide-rich layer and often surface cracking which affect fatigue performance of the part product. Therefore, multi-cut strategy is adapted to mitigate machining-induced defects. The multi-cut mode consists of one main/rough cut followed by a number of trim/finish cuts. Aspects of surface integrity of the WEDMed Ti-6Al-4V obtained in different modes of cut are delineated in this reporting. Three slots are produced: (1) main cut; (2) main cut followed by one trim cut; and (3) main cut followed by two trim cuts using uncoated brass wire and zinc-coated brass wire, respectively. Surface morphology along with topographical features including roughness average, crack density, recast layer thickness, material immigration, residual stress and micro-indentation hardness is studied. Results obtained thereof are analysed with relevance to kerf width, material removal rate and wire wear.

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