Inconel 718, a nickel-based precipitation-hardened superalloy (UNS N07718), is extensively used in turbine disc assemblies, aerospace fasteners, and cryogenic storage components owing to its outstanding high-temperature tensile strength (1,240 MPa at 650°C), corrosion resistance, and creep stability up to 700°C. However, its very properties that make it thermally and mechanically superior — high work-hardening coefficient, low thermal conductivity (11.4 W/m·K), and strong tendency towards tool-built-up-edge formation — render it among the most difficult-to-machine materials in conventional cutting processes. Wire Electrical Discharge Machining (Wire EDM), which removes material through controlled thermal erosion by spark discharge rather than mechanical contact, circumvents these cutting difficulties and is increasingly preferred for precision net-shape cutting of Inconel 718 components for the Indian aerospace and defence manufacturing sector.This investigation employs a Taguchi L27 orthogonal array to systematically study five Wire EDM process parameters — peak current (Ip), pulse-on time (Tᵒⁿ), open circuit voltage (Vᵒ), wire feed speed (WS), and servo feed rate (FR) — each at three levels, using Material Removal Rate (MRR), surface roughness (Ra), recast layer thickness (RLT), and kerf width (Kw) as response variables. Grey Relational Analysis (GRA) converts the four-response multi-objective optimisation into a single Grey Relational Grade (GRG) ranking, and ANOVA identifies the statistically dominant parameters. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) characterise surface morphology and recast layer composition at optimal and worst-case parameter settings. The optimal parameter combination achieves MRR of 28.7 mm³/min, Ra of 1.14 μm, RLT of 6.2 μm, and Kw of 0.284 mm, with peak current and pulse-on time identified as the dominant parameters by ANOVA (combined contribution: 68.3%).
Aravind Narayanan Prabhakaran Velayudham (Tue,) studied this question.