In-process Alloying of the White Layer of a Workpiece Machined by Die-sinking EDM

The aim is to improve the surface quality of EDMed workpieces by in-process alloying of the white layer.Two alloying methods are investigated: using compacted powder electrodes and using powder suspended dielectrics.Both methods are able to alloy the white layer of the machined workpiece if inverse polarity is used (workpiece positive, electrode negative).When using powder electrodes, the alloying percentage is inversely proportional to the density of the electrode.Alloying percentages of more than 40 % can be obtained.When using powder suspended dielectrics, the applied regimes have to be even less powerful than with the powder electrodes to enable alloying.In this case, alloying percentages of more than 10 % can be achieved.Test results show that it is possible to obtain a more corrosion resistant surface with a higher hardness and less micro cracks resulting in a longer lifetime of the workpiece.