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Carbides are new ceramic materials which are growingly used as substitute for metals in modem technology. Among these, silicon carbides is more under attention. Machining of this material is very difficult due to its high hardness and resistance to wear. Among traditional
methods, grinding is the most effective one. Nonetheless, specific and expensive wheels, limits on technology parameters and shapes and low machining rate: are
still problems. Electro-discharge machining is the best nonconventional method but it shows high instability and tendency to arcing compared with
machining of steels. This paper aims to
investigate the causes and possible guidelines for instability reduction or elimination. When machining silicon carbide under different pulse-times and number of transistors, experimental results show that, arc discharges have the
highest percentage of 60 among the other
pulse types. Open circuit pulses have the least percentage of 20 and normal discharges percentage is close to open circuit value. SEM pictures show existence of pure silicon on the machined surface which can cause instability due to
its high electrical resistance. Heat
generation within silicon carbide body especially near the discharge surface, may cause development of a thin dielectric vapor layer on the ,surface which can be a
reason for a large and fast growing
plasma channel and as a result' are
formation.