A composite comprising a polycrystalline diamentlegeme which is integrally bonded to a substrate of polycrystalline silicon carbide or silicon nitride as well as the process for its preparation

摘要

The composite comprises diamond crystals and a substrate of polycrystalline silicon carbide or silicon nitride bonded by silicon carbide and a carbide and/or silicide of a metal which forms a silicide with silicon. A mass of diamond crystals in contact with a mass of eutectiferous silicon-rich alloy and a silicon carbide or silicon nitride ceramic substrate are disposed in a container and placed within a pressure transmitting powder medium. Pressure is applied to the powder medium resulting in substantially isostatic pressure being applied to the container and its contents sufficient to dimensionally stabilize the container and its contents. The resulting shaped substantially isostatic system of powder-enveloped container is hot-pressed whereby fluid eutectiferous silicon-rich alloy is produced and infiltrated through the interstices between the diamond crystals and contacts the contacting face of the substrate sufficiently producing, upon cooling, an adherently bonded integral composite. In a modification, the use of a container is avoided by pressing a cavity in the pressure transmitting powder medium, placing the silicon-rich alloy, diamond crystals and silicon carbide or silicon nitride substrate in the cavity, covering the cavity with further powder medium, then applying isostatic pressure and hot pressing.