Abstract: A cutting element includes a multilayer polycrystalline diamond element bonded to a substrate of a less hard material. The polycrystalline diamond element defines a matrix of interstitial volumes. The interstitial volumes of a first region of the diamond layer are adjacent a working surface thereof being substantially free of a catalyzing material. The interstitial volumes of a second region of the diamond layer are remote from the working surface containing the catalyzing material.

Abstract: A cutting element comprises a multilayer polycrystalline diamond element 42 bonded to a substrate 44 of a less hard material, the polycrystalline diamond element 42 defining a matrix of interstitial volumes, the interstitial volumes of a first region of the diamond layer 42 adjacent a working surface 46 thereof being substantially free of a catalysing material, the interstitial volumes of a second region of the diamond layer 42 remote from the working surface 46 containing catalysing material.

Abstract: A preform element includes a polycrystalline facing table having a front face, a peripheral surface, and a rear surface bonded to the front surface of a tungsten carbide substrate. The front surface of the substrate has a flat central region and an outer peripheral region which is inclined away from the front face of the facing table as it extends outwardly. The outer peripheral region is formed with a number of spaced semi-circular recesses into which extend projections of diamond material formed on the rear surface of the facing table. The outer edge of each recess lies on the periphery of the substrate and the curved inner edge is tangential to the central region of the substrate. Smaller recesses are formed in the bottom surfaces of the semi-circular recesses and at other locations over the front surface of the substrate.

Abstract: A preform element, for example for use as a cutter in a rotary drill bit, includes a facing table of polycrystalline diamond bonded to a substrate of tungsten carbide. The rear surface of the facing table is integrally formed with a plurality of protuberances which project into the substrate and are spaced apart irregularly across the rear surface of the facing table. The protuberances may differ in cross-sectional shape and/or size, and the distribution of the different sizes and/or shapes may also be irregular. The protuberances may also project into the substrate to irregularly varying depths.

Abstract: A preform cutting element, for use on a rotary drill bit, includes a facing table of polycrystalline diamond bonded to a tungsten carbide substrate, a cutting edge being formed by part of the peripheral surface of the facing table. The rear surface of the facing table is integrally formed with a plurality of spaced elongate ribs which project into the substrate, at least the majority of the ribs being located in the vicinity of the cutting edge. The ribs may intersect the cutting edge and extend only part way across the facing table from the cutting edge. The ribs may vary in width and/or depth.

Abstract: A preform element, such as a cutting element for a drag-type drill bit, includes a facing table of superhard material having a front cutting face, a peripheral surface, and a rear surface bonded to a substrate which is less hard than the superhard material. The rear surface of the facing table is integrally formed with a plurality of protuberances, such as ribs or studs, which project into the substrate. The depth to which the protuberances project into the substrate varies in irregular manner across the facing table, so as to inhibit the propagation of cracks across the substrate to the rear of the facing table.

Abstract: A preform element, such as a cutting element for a drag-type drill bit, includes a facing table of superhard material having a front face, a peripheral surface, and a rear surface bonded to a substrate which is less hard than the superhard material. The rear surface of the facing table is integrally formed with a plurality of ribs which project into the substrate and extend in directions outwardly away from an inner area of the facing table towards the peripheral surface thereof.

Abstract: A method of forming a cutter assembly for a rotary drill bit comprises locating in a mould a preform polycrystalline diamond cutting element of a non-thermally stable type, packing powdered matrix-forming material, such as powdered tungsten carbide, around at least part of the cutting element within the mould, and then infiltrating the powdered material with a metal alloy in a furnace to form a body of solid infiltrated matrix in which the cutting element is at least partly embedded. The metal alloy is selected to provide an infiltration temperature, for example of up to about 850.degree., which is not greater than the temperature at which significant thermal degradation of the cutting element would occur.

Abstract: A preform cutting element, particularly for a drag-type rotary drill bit, comprises a thin cutting table of polycrystalline diamond, a substrate of cemented tungsten carbide, and a transition layer between the cutting table and substrate, the cutting table, transition layer, and substrate having been bonded together in a high pressure, high temperature press. The interface between the cutting table and the transition layer is configured and non-planar to reduce the risk of spalling and delamination of the cutting table. The interface between the transition layer and substrate may also be configured, and various methods are described for manufacturing the element with the non-planar interface.

Abstract: A cutting element for a rotary drill bit comprises a thin cutting table of polycrystalline diamond having a front cutting face and a rear surface bonded to a tungsten carbide substrate. The substrate incorporates one or more thin barrier layers which extend at least partly through the thickness of the substrate in a direction transverse to its front surface. Each barrier layer is formed of a material, such as nickel, which is more ductile than the material of the substrate, but is metallurgically compatible with it.

Abstract: A cutter assembly for a rotary drill bit comprises a preform cutting element mounted on a carrier. The cutting element includes a thin cutting table of polycrystalline diamond, defining a front cutting face and a cutting edge bonded to a less hard substrate which is in turn bonded to the carrier. The substrate and/or the carrier comprises a first portion of high erosion resistance, formed for example from tungsten carbide, and a second portion of lower erosion resistance, formed for example from tungsten metal, which is located in the vicinity of the cutting edge of the cutting element so that, in use, the wear flat is mostly formed in the material of lower erosion resistance.

Abstract: A cutting element for a rotary drill bit comprises a thin superhard table of polycrystalline diamond material, defining a front cutting face, bonded to a less hard substrate. The substrate is formed from a material containing at least a proportion of tungsten metal. The substrate may be formed of a metal matrix composite comprising tungsten metal particles in a metal binder phase comprising material selected from: Cu, Co, Ni+Cu, Ni+Fe, Ni+Fe+Mo, Co+Ni. The substrate may also include tungsten carbide in which case the tungsten metal may be replaced by another softer refractory material.

Abstract: A cutter assembly, for a rotary drill bit, comprises a stud to be received in a socket in the surface of the bit body, the stud being formed, adjacent one end, with a plane surface inclined to the longitudinal axis of the stud. A preform cutting element comprises a front surface, a peripheral edge surface, and a flat rear surface which is brazed to the surface on the stud, the peripheral edge surface of the cutting element being wholly exposed. The junction between the peripheral edge surface and the rear surface of the cutting element is chamfered. Any external fillet of brazing alloy is preferably removed or is not allowed to form during brazing, and the space between the chamfer and the surface of the stud may also be free of brazing alloy. Removal of the brazing fillet may also be advantageous in the case of a non-chamfered cutter.

Abstract: A cutting structure, for a rotary drill bit, is of the kind comprising a preform cutting element having a front cutting face formed of superhard material, such as polycrystalline diamond, and a rear face bonded to a carrier of less hard material, such as cemented tungsten carbide. The cutting element is bonded to the carrier by means of an alloy having the following composition:Ni about 30% to about 60%Pd about 30% to about 62%Si about 3% to about 15%wherein % is weight percent.An alternative alloy has the following composition:Cr about 4% to about 10%Fe about 1% to about 5%Si about 2% to about 7%C about 0.01% to about 0.10%B about 2% to about 5%Ni Balancewherein % is weight percent.

Abstract: A rotary drill bit is manufactured by forming a main bit body part from a machinable metal, such as steel, machining sockets in the outer surface of the main bit, inserting in each socket a thermally stable cutting structure or former which substantially fills at least the mouth of the socket and projects beyond the outer surface of the main bit body part, applying to the surface of the main bit body part, at least in an area surrounding each socket, a compound comprising powdered matrix-forming material, such as powdered tungsten carbide, mixed with a binder to form a paste, and infiltrating the matrix-forming compound with a metal alloy in a furnace to form a hard matrix. The size, location and orientation of the sockets may thus be accurately determined using conventional machining techniques, as in the case of an ordinary steel-bodied bit, but the external parts of the bit body are formed of hard solid matrix material and are thus highly resistant to erosion.

Abstract: A cutter assembly, for a rotary drill bit, comprises a preform cutting element mounted on a carrier in the form of a stud or post received in a socket in the bit body. The carrier is a metal matrix composite, formed by sintering, hot-pressing or by an infiltration process, and comprising tungsten metal particles in a metal binder phase, or a mixture of tungsten metal particles and tungsten carbide particles in a metal binder phase.

Abstract: A method of making a rotary drill bit comprises forming a hollow mould for moulding at least a portion of the bit body, packing at least a part of the mould with powdered matrix material, and infiltrating the material with a metal alloy in a furnace to form a matrix, the alloy being a copper based alloy containing phosphorus and being selected to provide an infiltration temperature which is not greater than 850.degree. C. and preferably not greater than 750.degree. C.