Production and EDM of Si3 N4–TiB2 ceramic composites

Abstract

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.