Characteristics of Machined Surface Layer of Cemented Carbide by Wire Electrical Discharge Machine

Wire cutting Electrical Discharge Machine (Wire EDM) uses the electrical discharge heat to cut the work piece with thin wire of brass or stainless steel by electrical discharge heat. The electrode and the work piece are melted and the cutting fluid between the electro and the piece is evaporated with burst. The melted material is spread in the shape of very tiny sphere chip. By the abrupt heating and cooling on the cutting surface, residual stress and void occurs on the surface. However the surface of oil Electrical Discharge machining is in hardening due to carbon in oil, the surface of water-wire cutting is in ductile structure. This ductile phenomenon might be due to the penetration of the melted wire brass into surface of the work piece. This paper presents the variation of micro structure and hardness of cemented carbide, cut by Wire cutting EDM with discharge energy. Brass is used for electrode. The mechanical property of the structure is changed by cemented copper from brass. The hardness distribution of the machined surface is evaluated. It is found that the cutting surface layer is in ductile structure. Considering the penetration phenomenon of the melting brass wire into Cu and Zn surface layer, the variation of hardness is investigated. The thickness of WC-Co (material of cemented carbide) ductile layer, generated by WEDM, is evaluated. This result will be useful information for a fine machining.