Micro-electrode discharge machining of TiN/SI3N4 composites

The feasibility of machining TiN/SI3N4 composites by a micro-EDM method has been explored. Samples of composites containing two different sizes of TiN particles were prepared by hot pressing and the resulting materials characterised in terms of microstructure, strength, fracture toughness, and electrical resistivity. A low electrical resistivity of 1.25x10 ^-3(omega) cm ^-1 was obtained in a 40 vol.-% composition. Micropores of 700 (mu)m depth and 70 (mu)m dia. were successfully machined into TiN/SI3N4 composites by the micro-EDM method. The results demonstrated the possibility of machining engineering ceramics by the micro-EDM method through the incorporation of conducting toughening phases. The size and content of TiN particles were found to have substantial effects on the strength, toughness, and electrical resistivity of the composites. BCT/389 The authors are in the Department of Material Science and Engineering, National Cheng-Kung University, Tainan, Taiwan 701, ROC. Manuscript received 23 June 1999; in final form 12 April 2000.