الفهرس 
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Abstract
Electrical Discharge Machining (EDM) is used in cutting special steels accurately; in this thesis the effect of electrode material in EDM has been studied to avoid the surface cracks, surface roughness and residual appeared during EDM. Two types of EDM electrode materials have been chosen, Dura graphite 11, POCO graphite “EDM-C3”. Two grades of tool steel are chosen as test materials, DIN 1.2080 and DIN 1.2379 they are a high carbon, high chromium alloy tool steels with excellent resistance to wear and abrasion. Different machining methods have been chosen “rough, medium, and soft” according to the pulse current (A) and pulse on duration time (μs), and it is found that the Dura graphite 11 exhibits more surface cracks upon DIN 1.2379 while it showed micro-cracks on the white layer surface than on DIN 1.2080, also Residual stresses were studied upon the surface and it was found that Poco Graphite EDM-C3 electrode results higher residual stresses compared with Dura Graphite 11 electrode. Also Soft EDM machining exhibits higher residual stresses as a result of higher pulse on duration time.