ガス圧焼結MoSi_2/Si_3N_4複合材料のワイヤー放電加工及び機械的性質 Wire Electrical Discharge Machining and Mechanical Properties of Gas Pressure Sintered MoSi_2/Si_3N_4 Composites

Particulate ceramic composites composed of Si_3N_4 matrix and dispersing MoSi_2 particles were sintered in 1 MPa N_2 atmosphere at 1850℃ for 1 h. The physical and mechanical properties of these composites containing 10, 20, 30, 40 and 50 vol% MoSi_2 were evaluated. The microstructure, strength, fracture toughness and electrical resistivity for the composite fo MoSi_2/Si_3N_4 were investigated. The electrical resistivity of the composites decreases with increasing amount of dispersoids and reaches a minimum (〜10^<-2>Ω・cm) in the 50 vol% MoSi_2/Si_3N_4 composite. Such a conductivity could be machined by wire electric discharge machining (WEDM). The removal rate of MoSi_2/Si_3N_4 composite was found to be dependent on electrical conductivity for constant working voltage. This result demonstrated the feasibility of machining structural ceramics using EDM method through the incorporation of MoSi_2 conductive phase into ceramic matrix composite.