CHARACTERIZATION OF THE CONDUCTIVE LAYER FORMED DURING μ - ELECTRIC DISCHARGE MACHINING OF NON-CONDUCTIVE CERAMICS

摘要

Electric discharge machining (EDM) widely used to machine hard metals requires both the tool and the work piece to be conductive. However, recently it has been shown that even non-conductive ceramics can be machined effectively with EDM by applying a conducting layer of assisting electrode on top of the insulating ceramics. Discharges are initially triggered by the assisting electrode and a conductive layer which is produced during the spark erosion process ensures that the top layer of the insulating ceramic remains conductive. After the machining process, the conductive layer can be easily removed.This paper presents the investigations made on the conductive layer generated during the μ-EDM of three widely used non-conductive ceramics, namely ZrO_2, Si_3N_4 and SiC. Various aspects of the generated transitional layer including the thickness, the surface resistance, the surface roughness and the surface topography have been reported. Based on the surface topography of the transitional layer, the material removal mechanisms responsible for μ-EDM of different non-conductive ceramics have been discussed.