Investigation of Surface Properties in Manganese Powder Mixed Electrical Discharge Machining of OHNS And D2 Die Steels

Abstract

The electrical discharge machining (EDM) process is used for generating accurate internal profiles in hardened materials. An powder additive in the hydrocarbon dielectric affects the energy distribution and sparking efficiency, and consequently the surface finish and micro-hardness. In this paper the Taguchi approach has been used to optimize and compare the surface properties in manganese powder-mixed EDM of oil-hardening non-shrinkable (OHNS) and high-carbon high-chromium (D2) die steels. The results of the study show an improvement of 73% and 71.6% in the micro-hardness of OHNS and D2 die steels, respectively. The machining parameters for the best value of microhardness are found to be the same for both work materials. A scanning electron microscopy and X-ray diffraction analysis of the machined surfaces show a transfer of manganese and carbon from the plasma channel in the form of manganese carbide. The chemical composition of the machined surface has been further checked on an optical emission spectrometer to verify and quantify the results.