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

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