Abstract: A polycrystalline diamond abrasive element, particularly a cutting element, comprises a table of polycrystalline diamond bonded to a substrate, particularly a cemented carbide substrate, along a non-planar interface. The non-planar interface typically has a cruciform configuration. The polycrystalline diamond has a high wear-resistance, and has a region adjacent the working surface lean in catalysing material and a region rich in catalysing material. The region lean in catalysing material extends to a depth of 40 to 90 microns, which is much shallower than in the prior art. Notwithstanding the shallow region lean in catalysing material, the polycrystalline diamond cutters have a wear resistance, impact strength and cutter life comparable to that of prior art cutter, but requiring only 20% of the treatment times of the prior art cutters.

Abstract: A polycrystalline diamond abrasive cutting element consists generally of a layer of high grade polycrystalline diamond bonded to a cemented carbide substrate. The polycrystalline diamond layer has a working surface and an outer peripheral surface and is characterized by having an annular region or a portion thereof adjacent the peripheral surface that is lean in catalysing material. A region adjacent the working surface is also lean in catalysing material such that in use, as a wear scar develops, both the leading edge and the trailing edge thereof are located in a region lean in catalysing material.

Abstract: A rotary drag bit comprises a bit body and a plurality of blades extending radially away from the bit body, each blade including a cutting assembly. Each cutting assembly has a plurality of primary cutters orientated in the direction of rotation of the drill bit for drilling or boring into a subterranean rock formation, and a plurality of secondary or brute cutters located behind the primary cutters in relation to the direction of rotation of the drag bit. The invention is concerned primarily with the secondary cutters, which comprise a layer of superabrasive material, such as PCD, PCBN or CVD diamond, bonded to a support substrate. The interface between the superabrasive layer and the substrate has a stepped region that provides the cutter with a skirt or hoop of superabrasive extending into the substrate. The secondary cutter is orientated in use to present a bearing surface to the rock formation and a secondary cutting edge in the direction of rotation of the rotary bit.

Abstract: A tool insert comprises a working layer of ultra-hard abrasive, particularly PCD, bonded to a substrate along an interface. The working layer presents a working surface and a periphery around the working surface which provides a cutting edge for the insert. The working layer of ultra-hard abrasive has a first region extending into the layer from the working surface, and a second region in contact with the first region, the wear resistance of the first region being less than that of the second region. The wear resistance of the first region is between 50% and 95% of that of the second region, preferably between 60% and 90%, most preferably between 70% and 89%.

Abstract: A tool insert comprises a substrate (40), a layer of ultra-hard abrasive material (52) bonded to the substrate and presenting a primary cutting edge (54) for the tool insert, and a protective layer (56) bonded to the ultra-hard abrasive material so as to protect the primary cutting edge thereof. The protective layer provides a secondary cutting edge (58) for the tool insert, the depth of the protective layer being selected so as to be sufficient to protect the primary cutting edge whilst cutting, milling or drilling a window through a first substance, such as a casing or lining of a borehole or shaft, but to expose the primary cutting edge upon encountering a second substance, such as a rockbed. The invention extends to a method of drilling a horizontal or angled hole in a sub-terranean rock formation using a rotary drill string and bit incorporating a tool insert of the invention.

Abstract: A tool insert comprises a substrate (10) having a support surface and a support ring extending laterally from the support surface. The support ring is sized to define a recess (14) within the confines thereof and a shelf about the periphery thereof. A layer (12) of ultra-hard abrasive material is located within the recess and bonded to the substrate and the support ring (16), and presents a primary cutting edge (22) for the tool insert. A protective layer (18) is bonded to the shelf about the support ring so as to protect the primary cutting edge. The protective layer provides a secondary cutting edge (20) for the tool insert, the depth of the protective layer being selected so as to be sufficient to protect the primary cutting edge whilst cutting, milling or drilling through a first substance but to expose the primary cutting edge upon encountering a second substance.

Abstract: A polycrystalline diamond abrasive element, particularly a cutting element, comprises a layer of polycrystalline diamond having a working surface and bonded to a substrate, particularly a cemented carbide substrate, along an interface. The polycrystalline diamond abrasive element is characterised by using a binder phase that is homogeneously distributed through the polycrystalline diamond layer and that is of a fine scale. The polycrystalline diamond also has a region adjacent the working surface lean in catalysing material and a region rich in catalysing material.