Experimental Investigation on Through Hole making by Electro-Discharge Machining (EDM) of Inconel 625 Super Alloy Using Hollow Copper Tool Electrode

Abstract

A case experimental research towards investigating feasibility of through hole making process on Inconel 625 super alloy by using hollow (tubular) Copper tool electrode in Electro-Discharge Machining (EDM) has been delineated herein. Based on three controllable process variables viz. peak discharge current, pulse-on duration and gap voltage etc., experiments on through hole making have been carried out following the EDM route (die-sinking EDM without flushing). In addition to surface morphology, topographical features of the EDMed work surface have been examined for both internal cylindrical surface of the hole produced and also the external peripheral surface of the removed cylindrical part.
Effects of the process parameters have been analyzed on influencing various process performance features like Material Removal Rate (MRR), Surface Roughness (SR), Surface Crack Density (SCD), White Layer Thickness (WLT), circularity, radial overcut and hole taper. An optimal parameters setting has been identified for sound hole making and thereby to improve EDM performance. Additionally, EDS analysis has been carried out to investigate the extent of carbon enrichment onto the EDMed work surface of Inconel 625 as affected by the pyrolysis of the dielectric fluid whilst executing EDM operation. XRD tests have been carried out to compare metallurgy of the EDMed work surface (various phases/precipitates present in bulk of the matrix material, extent of grain refinement, crystallite size, strain and dislocation density) with respect to that of ‘as received’ Inconel 625. Results, thus obtained, have also been compared to that of micro-hardness test data.