Impact of Powder-mixed Electrical Discharge Machining on Surface Hardness of AISI D3 Die Steel

Surface modification through Electrical Discharge Machining (EDM) is an active area of research as it involves only surface alloying without affecting the core material. In the present work, surface hardness of AISI D3, a type of high carbon high chromium (HCHCr) die steel, has been enhanced using powder mixed EDM process. Manganese powder is mixed in different concentrations of 5, 10 and 15 g/litre in the dielectric oil. Design of experiment approach is used to investigate the effect of five process variables, namely electrode material, peak current, pulse on time, pulse off time and powder concentration, on surface hardness of the die steel. Surface hardness of unmachined and EDMed (without powder mixing) HCHCr die steel is 710 HV and 1242 HV respectively, whereas after manganese powder mixed EDM, and using graphite electrode with negative polarity, the micro hardness of this material is obtained as high as 2815 HV due to surface alloying. The material transferred on the machined surface is further investigated through scanning electron microscopy and X-ray diffraction analysis.