Performance evaluation of electro-spark eroded high-volume fraction of Cr-Fe-Ni superalloy

Abstract

Current research aims to execute a viability study of electro-spark erosion technique to process Inconel 690, a high-volume fraction of Cr-Fe-Ni superalloy (∼32% Cr). The Box-Behnken design of response surface methodology with varying processing conditions is used to execute the experimental trails. Process performance is examined in terms of material removal rate and surface topography. The surface conditions of the processed surface are studied using scanning electron microscopy. The tool wear character and tribological behavior of the processed surface are also scrutinized to check the post-process consequences. The study explores the formation of oxide layers, craters, spherical droplets, and micro-cracks on the surface processed at T_on: 118 mu; T_off: 45 mu; I_p: 130 mu; S_v: 50 V (parametrical settings for maximum material removal rate), and at T_on: 118 mu; T_off: 30 mu; I_p: 220 mu; S_v: 50 V (parametrical settings for maximum surface roughness) attributing a deteriorating surface quality. The maximum material removal rate of 9.38 mm³/min and minimum surface roughness of 0.47 μm are achieved. A significant improvement of approximately 20 HV in micro-hardness is detected owing to the formation of a recast layer on the processed surface. Consequently, a noticeable improvement is observed in the wear resistance of the processed surface.