Wire Electrical Discharge Machining and-Mechanical Properties of Gas Pressure Sintered MoSi_2/Si_3N_4 Composites

摘要

Particulate ceramic composites composed of Si3N4 matrix and dispersing MoSi_2 particles were sintered in 1 MPa N2 atmosphere at 1850 deg C for 1 h. The physical and mechanical properties of these composites containing 10, 20, 30, 40 and 50 vol percent MoSi_2 were evaluated. The microstructure, strength, fracture toughness and electrical resistivity for the composite of MoSi_2/Si_3N_4 were investigated. The electrical resistivity of the composites decreases with increasing amount of dispersoids and reaches a minimum (approx 10~(-2) #OMEGA# -cm) in the 50 vol percent 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.