Microstructure at submicron scale of the white layer produced by EDM technique

Electro-discharge machining (EDM) technique is widely used for machining hard metals and for performing specific tasks which cannot be achieved using conventional techniques. The most frequently used industrial application of die-sinking EDM is mould fabrication. The sparks produced during the EDM process locally melt the metal surface, which then undergoes an ultrarapid quenching. After solidification, a layer is formed at the workpiece surface, the so-called white layer. The white layer is composed of sublayers with particular structures and phases, depending on the machining energy. Crystallographical and metallurgical properties of the white layer are reported in this paper.