Machinable ZrB2-SiC-BN composites fabricated by reactive spark plasma sintering

A solid state reaction of ZrH2, Si3N4 and B4C has been proposed to synthesize machinable ZrB2-SiC-BN composites. Dense ZrB2-SiC-BN composites with fine grain size and homogeneous microstructure were fabricated via spark plasma sintering at 1900 °C in vacuum. The kinetics of the reaction process was studied with XRD results. SEM and TEM results showed that the in-situ formed BN phase was composed of micro-sized intergranular and nano-sized intragranular h-BN particles. The influences of the BN content on the mechanical properties as well as the thermal conductivities of the composites were studied. The composites that contained >20 vol% BN exhibited excellent machinability and high strength.