SiC Infiltred Diamond Composites

Abstract

Polycrystalline SiC-diamond composites have been fabricated by high pressure and high temperature, HPHT, sintering using a Si infiltration method. However, infiltration of liquid silicon around the diamond particles results not only in SiC but also in free silicon, which causes deterioration of the composite properties. In this work, a novel sintering procedure was developed to avoid the formation of free silicon in the composite structure. A disc composed of a mixture of graphite and silicon was first press-molded at room temperature. The disc was then placed above the diamond powder inside a high pressure chamber used for the HPHT sintering process. This arrangement permitted to preferentially form liquid Si in a C solution, which infiltrates in between the diamond particles. Using this procedure, free silicon formation is inhibited and the SiC-diamond composite forms a rigid structure with improved properties.