Rock bits having metallurgically bonded cutter inserts

Abstract From the Canadian patent

A cladding process is disclosed wherein hard carbide cutter inserts, as well as polycrystalline diamond composites, are metallurgically bonded ininto an interior core of a drag, bit body. The cladding is bonded onto the exterior surface of the core of the drag bit by a powder metallurgy process. A thin layer or coating of a suitable metal, preferably nickel is pro-, vided on, for example, the carbide inserts prior to mounting into the core. The coating prevents degradation of the carbide through loss of carbon into the core during the powder metallurgy process and accommodates mismatch of thermal expansion between the cutter insert and the core.