Cutting elements for rotary drill bits

A preform cutting element comprising a thin superhard cutting table, a substrate material which is less hard than the superhard material, and at least one transition layer between the cutting table and the substrate, the cutting table, transition layer and substrate having been bonded together in a high pressure, high temperature press, the transition layer being substantially continuous across the cutting element and varying in thickness in a manner to provide a plurality of projections on the transition layer which project into the material of the substrate and provide a configured non-planar interface between the substrate and the transition layer.

A perform cutting element comprising a thin cutting table of superhard material, a substrate of material which is less hard than the superhard material, and at least one transition layer between the cutting table and the substrate, the transition layer comprising a transition material which differs in composition from the materials of both the cutting table and the substrate, and the cutting table, transition layer and substrate having been bonded together in a high pressure, high temperature press, the transition layer being non-continuous and comprising regions where the transition material projects into recesses in the cutting table, and other regions where the material of the cutting table extends through the transition layer and is bonded directly to the substrate.

A preform cutting element comprising a thin cutting table of superhard material, a substrate of material which is less hard than the superhard material, and at least one transition layer between the cutting table and substrate, the transition layer comprising a transition material which differs in composition from the materials of both the cutting table and the substrate, and the cutting table, transition layer and substrate having been bonded together in a high pressure, high temperature press, the transition layer comprising a plurality of separate projections, spaced apart across the cutting element and bonded to the substrate, which projections extend into a plurality of corresponding recesses in the cutting table, the surface of the cutting table outside said recesses being bonded directly to the substrate.