Analysis on surface characteristics of electro-discharge machined Inconel 718

Abstract

An experimental investigation has been carried out on electro-discharge machining (EDM) of Inconel 718 using copper electrode tool. Based on L25 orthogonal array, experiments have been conducted by utilising five controllable process parameters (viz. gap voltage, peak current, pulse-on time, duty factor and flushing pressure), each varied at five discrete levels, within selected parametric domain. The following responses in relation to surface characteristics of EDMed Inconel 718, i.e., roughness average (Ra), surface crack density (SCD) and white layer thickness (WLT) have been investigated. SEM micro-graphs revealing various surface irregularities associated in surface morphology of the EDMed Inconel 718 have been analysed in detail and correlated with the information obtained through EDAX, XRD and micro-hardness tests of the machined surface. The presence of different types of cracks within EDMed end product has also been identified. Effects of significant process parameters on surface topography in terms of roughness average, SCD, white layer thickness, etc. have been graphically represented. Finally, utility theory in conjugation with Taguchi�s optimisation philosophy has been attempted to select the most favourable process environment (parameters setting) to satisfy optimal Ra, SCD and WLT; thereby, ensuring high product quality along with its specified functional requirements in appropriate application domain.