Investigation of micro-hardness of H11 die steel using composite material electrodes in EDM

Abstract

Electrical Discharge Machining (EDM), a non-traditional material removal process has been well recognized for itsability for precision machining of electrically conducting hard materials. Repetitive heating and cooling of the workpiecesurface during the machining make the surface hard. During this process, the transfer of material into workpiece surface dueto diffusion of material from the tool electrodes results in the desire surface modifications. This paper investigates the effectof electric discharge machining on H11 die-steel materials with composite material electrodes fabricated by stir casting aswell as powder metallurgy process. Copper (85% by weight) has been used as matrix material with tungsten and carbonnanotubes (10%-5% by weight). The performance of fabricated composite electrodes has also been compared withconventional copper electrode. Microhardness achieved has been found to be best when H11 die-steel surface ismachined with composite electrodes fabricated by powder metallurgy process. Also, the microhardness has been enhancedby 19.57% with optimal input parameters. Results show that optimum microhardness has been observed at high peak currentvalue when surface is machined with copper conventional electrode while pulse on time has been found to the majorcontributor when surface is machined by composite material electrode. XRD analysis indicates the formation of tungsten-carbide, iron-carbide, chromium- nickel and copper on the machined surface of the workpiece