Experimental Investigation of EDM Parameters for ZrB₂-SiC Ceramics Machining

Ceramics ZrB₂-SiC has been extensively applied in high temperature industry because of its high melting point, hardness, and excellent thermal shock resistance. However, ZrB₂-SiC is difficult to machine with traditional cutting techniques due to its high hardness and brittleness. Electrical discharge machining (EDM) has been becoming one effective cutting technique to machine ZrB₂-SiC components with high shape and dimension precision. In this paper, the process parameters including polarity of electrode, peak current, pulse-on time and pulse-off time are selected to study the influence on material removal rate, side gap, and surface roughness. Machined surfaces are analyzed using scanning electron microscopy (SEM), polygonal material layer and flat area are found on the machined surface. The forming of polygonal material layer is due to different thermal physical properties in the process of resolidification of ZrB₂, SiC and pyrolytic carbon. The flat area is the central point of larger energy discharge channel. Tiny craters with few microns caused by removal of SiC grains are found on the machined surface, the number of them increases with increase of discharge energy.