An approach for increasing the micro-hardness in electrical discharge machining by adding conductive powder to the dielectric

The present study deals with investigations on the effect of process variables on micro-hardness during electro-discharge machining (EDM) and powder mixed electro-discharge machining (PMEDM) of H-11 die steel. Taguchi's L-27 orthogonal array has been used to conduct the experiments using chromium powder mixed dielectric fluid with varying "powder concentration (C-p), peak current (I-p), pulse on time (T-on), duty cycle (DC) and gap voltage (V-g)." Analysis of variance (ANOVA) has been used to establish the optimal setting. Empirical model has been developed to predict micro-hardness. The optimum set of parameters for maximum micro-hardness was identified as C-p of 6 gm/l, I-p of 9Amp, T-on of 150 mu s, DC of 80% and V-g of 50 V. Confirmatory test reveals a relative error of 1.95% between predicted and experimental values of micro-hardness. Material migration from tool to the machined surface, conductive powder and dielectric fluid has been analysed using "Scanning Electron Microscope" (SEM) and " Energy Dispersive Spectroscopy" (EDS). (C) 2017 Published by Elsevier Ltd.