Molybdenum/Niobium Disilicide Composites by Spark PlasmaSintering

Pressure Assisted Field Emission Sintering was employed to produce a fully dense MoSi2-NbSi2 composite containing up to 20% of NbSi2. MoSi-based intermetallics are interesting candidates as structural materials for advanced aerospace and turbine systems. Due to the relatively high oxygen content of the employed commercial silicide powders, it was necessary to add a reducing agent to avoid the formation of a brittle oxide phase during sintering. This strategy, using carbon as a reducing agent, promoted the formation of other silicide phases and silicon carbide, that may possibly improve the mechanical properties of the composites. In order to obtain a homogeneous carbon distribution, phenolic resin was added to the silicide powders and pyrolysed in a thermal treatment realised before sintering. Depending on the phenolic resin content (up to 20% in weight), different microstructures were observed, and their effect on the microhardness was studied.