Production and EDM of Si3 N4–TiB2 ceramic composites

Ceramic matrix composites containing TiB2 as a particulate phase have been produced by hot pressing. The problems of the reactivity of TiB2 with the Si3 N4 matrix and with the sintering environment have been successfully addressed. A novel dual atmosphere sintering profile combined with low temperature hot pressing has been used to successfully produce fully dense materials. The effect of TiB2 addition on mechanical properties has been investigated. Composites containing TiB2 show significant improvements in hardness and fracture toughness. The addition of TiB2 at a level of 40 vol.-% raises the conductivity of the composite to a level where electro-discharge machining (EDM) is possible. A comprehensive study of the application of EDM has been carried out and the optimum machining conditions have been identified. Under these conditions Si3 N4–TiB2 composites have been shaped with relative ease and proved to be ‘robust’ materials under EDM.