The last decade has seen an increasing interest in the application of electrical discharge machining (EDM) as a surface modification process. Erosion of the tool material takes place during machining and some of it gets alloyed with the work piece surface. Deliberate material transfer may be carried out by using composite electrodes or by dispersing metallic powders in the dielectric medium. This paper reports the results of experimental investigations into electrical discharge machining of OHNS die steel with Inconel (an alloy of chromium, nickel and iron) electrode under machining conditions favouring high electrode wear. For comparison, the work material was also machined with copper electrode. Results show 88% improvement in micro-hardness of the machined surface. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis reveal transfer of chromium and nickel from the tool electrode. Chemical composition of the machined surface was further checked on optical emission spectrometer.
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Kumar et al. (2009) studied this question.