Effect of Process Parameters on the Total Heat Damaged Zone (HDZ) during Micro-EDM of Plastic Mold Steel 1.2738

In micro electrical discharge machining, three subsurface layersare formed on the workpiece, they are;recast zone, heat affected zone and converted zone, primarily due to heating-quenching cycles. The HDZ inmicro-EDM is characterized by cracks and weakness in the grain boundary and thermal residual stresses.This paper presents the effect of process parameters on the HDZ in micro-EDM of plastic mold steel 1.2738.As the energy of the sparks increases, the thickness of the HDZ increases and the average coefficient ofcorrelation between energy and HDZ considering three different sections of the zone is 0.8099. Therefore,the effect of process parameters governing the discharge energy are analyzed; they are: average current(Ia), peak current (Ip) and pulse ‘on-time’ (Ton). An overall increase in heat-damaged zone thickness by105% is observed with an increase in pulse on time.