The effects of powder suspended dielectrics on the thermal influenced zone by electrodischarge machining with small discharge energies

EDM is used to machine every electrically conductive material by removing material through electrical discharges in a dielectric fluid. During machining the heat intensity from the spark melts a part of the workpiece. This liquid phase of the material resolidifies rapidly and builds the recast layer. A lot of work has been done before to explain the physical principles governing the process and the thermal influenced zone. Effects on the recast layer by using microJoule-range discharge energies in combination with powder suspended working fluids are examined in this paper. The effects of a capacitor connected parallel to the gap were investigated in relation to the recast layer formation. In addition, transverse section pictures show the morphology and the depth of the thermal influenced zone. The aim was to investigate the influence of the powder particles in micro-sinking-EDM and especially in the gap, on the thermal spread in the dielectric and on the influenced zone. Pictures were taken during the spark generation in different suspended dielectrics with a high speed framing camera. Furthermore, a complete qualitative and quantitative analysis of an EDX spectrum has been performed in order to examine the changes of the recast layer composition by using powder suspended dielectrics at the workpiece surface. (C) 2004 Elsevier B.V. All rights reserved.