US Patent 7665552 Superhard insert with an interface

In one aspect of the invention, a superhard insert has a carbide substrate bonded to ceramic layer at an interface. The substrate has a generally frusto-conical end at the interface with a tapered portion leading to a flat portion. The central section of the ceramic layer may have a first thickness immediately over the flat portion of the substrate. The peripheral section of the ceramic layer has a second thickness being less than the first thickness covering the tapered portion of the substrate. The ceramic layer may be formed using HPHT technology.