Mechanism of material deposition from powder, electrode and dielectric for surface modification of H11and H13 die steels in EDM process

摘要

Surface modifications using the powder mixed electric discharge machining (PMEDM) process has gained a lot of research interest in recent few years. The present paper investigates the material transfer from the powder suspended in dielectric, electrode and dielectric material for enhancing the surface properties measured in terms of the microhardness of the machined surface for two kinds of die steels (H11 and H13). Four different powder materials aluminium, copper, graphite and tungsten were mixed with dielectric during machining with three different dielectric materials namely kerosene, EDM oil and refined mineral oil. Other process parameters were varied at suitable levels. Maximum increase in microhardness was observed with addition of tungsten powder and with tungsten-copper electrode even at lower current. Current significantly affected the transfer mechanism of material on the machined surface but was dwarfed by the very significant affect of powder which had the largest contribution. A relative comparison of microhardness between deposited and non-deposited regions showed an increase of 37% for H11 and 56% for H13 due to addition of powder. The photomicrographs of the machined surface also supported the material transfer from powder, electrode as well as dielectric forming compounds that suitably improve the surface properties of H11 and H13 die steel.