Matrix hard facing by lost wax process

Abstract

A drill bit comprises a main body part having a shank for connection to a drill string, an end face, an internal passage for supplying drilling fluid to the end face, a number of blades extending from the end face outwardly and longitudinally of the central axis of rotation of the bit, and a number of cutters mounted on each said blade. Each blade comprises a central metal core at least partly surrounded by solid infiltrated matrix material. A method of manufacturing such a drill bit includes the steps of forming a main body part from metal, applying to the outer surface of the main body part a coating layer of wax which liquefies at elevated temperature, applying to the coated body part mold-forming material to provide a self-supporting mold surrounding the coated body part, and raising the temperature of the body and surrounding mold sufficiently to liquefy the coating material. The liquefied coating is then drained from the mold, and the cavities left by the coating material are packed with powdered matrix material, which is then infiltrated with a binder alloy at elevated temperature to form a solid infiltrated matrix layer, on the bit body part, corresponding to the layer of wax previously applied.