Cast steel rock bit cutter cones having metallurgically bonded cutter

Abstract

Tools, and particularly rock bit cutter cones, having 'hard' cermet cutter inserts enveloped in an intermediate layer or coating of a suitable high melting metal, and embedded in a cast steel matrix, are disclosed. The cermet inserts, which usually comprise tungsten carbide in a cobalt phase (WC-Co), are coated with a layer of a metal or metal alloy, preferably nickel, which does not substantially melt during the subsequent step of casting the steel matrix of the tool. An additional layer of copper is advantageously employed on the cermet insert beneath the layer of the high melting metal, such as nickel. The coated inserts are held in appropriate position in a suitable mold, and the steel matrix of the tool is poured from molten metal. The coatings on the cermet inserts prevent thermal shock to the inserts, prevent deterioration of the cermet due to diffusion of carbon into the adjacent steel, and metallurgically bond the inserts to the embedding steel matrix.