Multiple grade carbide for diamond capped insert

摘要

An insert for a rolling cone earth-boring bit has a cylindrical base that interferingly presses into a mating hole formed in a cone of the bit. The insert has a convex end that extends from the base. A polycrystalline diamond cap is bonded to the convex end. The body is formed of at least two layers of carbide material having different mechanical properties, particularly a different modulus of elasticity. The first layer may have a metallic binder with a lesser percentage than the binder of the second layer to reduce the stress at the interface between the first layer and the diamond cap. The layers may have different average carbide grain sizes, with finer average grain sizes adjoining the diamond cap. Further, the layers may have different binders, with cobalt being the binder in the layer adjoining the diamond cap and either nickel or a nickel-cobalt alloy in another layer.