WEDM of nickel based aerospace alloy: optimization of process parameters and modelling

Abstract

This article presents the experimental data for the machining of Nimonic-90 on wire electrical discharge machining (WEDM). It is a nickel based alloy which possessing creep resistance and high rupture strength at high temperature (up to $$950~^{\circ }\hbox {C}$$ ). Four input process parameters, viz., peak current (Ip), pulse-on time (Ton), pulse-off time (Toff), and servo voltage (SV) were investigated and modelled for three response variables namely cutting speed (CS), surface roughness (SR) and radial overcut (RoC) utilizing Response Surface Methodology (RSM). In present experimentation, quadratic model is suggested for all three responses. Analysis of Variance (ANOVA) indicate that Ip, Ton, Toff and SV are significant process parameters influencing the CS and SR while Ip, Ton and SV were highly significant parameters influencing the RoC. Desirability function was employed to optimize the multi-performance characteristics. Using SEM micrographs and micro-hardness profile, effect of discharge energy (DE) on surface morphology was examined. Topography of machined surface; corresponds to different levels of DE; suggests that high discharge energy results in overlapped and deep craters of large size diameters and high thickness of recast layer whereas low discharge energy results into fine surface with minimum recast layer.