Abstract: The present invention provides a superhard polycrystalline diamond or diamond-like element with greatly improved resistance to thermal degradation without loss of impact strength. Collectively called PCD elements, these elements are formed with a binder-catalyzing material in a high-temperature, high-pressure process. The PCD element has a plurality of partially bonded diamond or diamond-like crystals forming at least one continuous diamond matrix, and the interstices among the diamond crystals forming at least one continuous interstitial matrix containing a catalyzing material. The element has a working surface and a body, where a portion of the interstitial matrix in the body adjacent to the working surface is substantially free of the catalyzing material, and the remaining interstitial matrix contains the catalyzing material.

Abstract: Disclosed is a polycrystalline diamond or diamond-like element with greatly improved wear resistance without loss of impact strength. These elements are formed with a binder-catalyzing material in a high-temperature, high-pressure (HTHP) process. The PCD element has a body with a plurality of bonded diamond or diamond-like crystals forming a continuous diamond matrix that has a diamond volume density greater than 85%. Interstices among the diamond crystals form a continuous interstitial matrix containing a catalyzing material. The diamond matrix table is formed and integrally bonded with a metallic substrate containing the catalyzing material during the HTHP process. The diamond matrix body has a working surface, where a portion of the interstitial matrix in the body adjacent to the working surface is substantially free of the catalyzing material, and the remaining interstitial matrix contains the catalyzing material.

Abstract: Disclosed is a polycrystalline diamond or diamond-like element with greatly improved wear resistance without loss of impact strength. These elements are formed with a binder-catalyzing material in a high-temperature, high-pressure (HTHP) process. The PCD element has a body with a plurality of bonded diamond or diamond-like crystals forming a continuous diamond matrix that has a diamond volume density greater than 85%. Interstices among the diamond crystals form a continuous interstitial matrix containing a catalyzing material. The diamond matrix table is formed and integrally bonded with a metallic substrate containing the catalyzing material during the HTHP process. The diamond matrix body has a working surface, where a portion of the interstitial matrix in the body adjacent to the working surface is substantially free of the catalyzing material, and the remaining interstitial matrix contains the catalyzing material.

Abstract: A method of thermally treating a preform element, of the kind having a facing table of polycrystalline diamond bonded to a substrate of cemented tungsten carbide, comprises the steps of: (a) heating the element to a soaking temperature of 550-625° C., and preferably about 600° C., (b) maintaining the element at that temperature for at least one hour, and (c) cooling the element to ambient temperature. The resulting preform element has a substrate with a cobalt binder including a substrate interface zone with at least 30 percent by volume of the cobalt binder a hexagonal close packed crystal structure. This reduces the risk of cracking or delamination of the element in use.

Abstract: A drill bit for drilling a borehole having a bit body with an axis of rotation, a leading face, and a plurality of blades upstanding from the leading face. At least one of the blades terminates in a gauge pad having a gauge surface arranged, in use, to face a wall of the borehole. The gauge surface being devoid of cutting elements and terminating at an end remote from the blade at a junction with a gauge pad end wall. The gauge pad carries a cutter having a face and a cutting edge located radially inward of the gauge surface, and the junction of the gauge surface and the gauge pad end wall crosses, radially, between the face of the cutter and the wall of the borehole. The gauge surface may be a substantially continuous surface, and may have at least one additional cutter located angularly between two adjacent blades of the drill bit.

Abstract: A preform cutting element, for a rotary drill bit, and a rotary drill bit with prefrom cutting elements including a facing table of superhard material having a front face, a rear surface is bonded to the front surface of a substrate which is less hard than the superhard material and has a rim or edge section of the superhard material at least partially covered by a metallic material different from the substrate material. The metallic material is bonded to the edge section of the superhard material through a high pressure bonding step. The superhard material covered by the compliant metallic material is protected from impact forces occurring in drill bit operations such as tripping.

Abstract: A method for use in designing rotary drill bits comprises determining locations in which cutters are to be provided, determining likely wear rates for cutters positioned at those locations, and using the likely wear rates to chose between relatively high and relatively low wear rate cutters for each location. The cutters all have substantially the same impact toughness.

Abstract: The present invention is a drag-type drill bit for drilling a borehole in the earth. The bit is designed to rotate about a central axis of rotation and has a bit body having a leading face, an end face, a gauge region, and a shank for connection to a drill string, a plurality of nozzles in the bit body for delivering drilling fluid to the end face, a plurality of blades upstanding from the leading face of the bit body and extending outwardly away from the central axis of rotation of the bit. Each blade terminates in a gauge pad with a surface which faces a wall of the borehole. A first plurality of cutters are mounted on the blades at the end face of the bit body and a second plurality of cutters are mounted the gauge pads and arranged such that in operation, they cut the wall of the borehole. Each one of the second plurality of cutters has a backrake less than or equal to about 20 degrees.

Abstract: A method of machining a polycrystalline diamond material including a matrix of interstices containing a catalyzing material and a volume close to a working surface thereof substantially free of catalyzing material which comprises the steps of treating the volume to render the polycrystalline diamond electrically conductive, and using an electron discharge machining technique to machine the polycrystalline diamond. In one embodiment, the treatment comprises applying a conductive material layer to a surface of the diamond.

Abstract: A rotary drill bit is manufactured by a method including the step of forming at least a portion of the bit body from a precipitation hardening alloy, and brazing cutters to the bit body by a heating and cooling cycle during which the bit body is first heated to a temperature sufficient to melt the brazing material and is then cooled to room temperature, the heating and cooling brazing cycle being controlled in a manner so as also to effect precipitation hardening of the alloy from which the bit body is formed. In the case where the bit body is formed from solid infiltrated matrix material around a solid preformed mandrel, the heating and cooling cycle of the matrix forming process may also be controlled in a manner to effect precipitation hardening of the alloy from which the mandrel is formed.

Abstract: A cutting element for a rotary drag-type drill bit comprises a body of polycrystalline diamond incorporating a binder-catalyst selected from iron group elements, such as iron, cobalt and nickel, or alloys thereof. The body of polycrystalline diamond is unsupported by an integral substrate. The cutting element may be mounted directly on the body of the drill bit, or may be brazed to a substrate of a different, less hard material which is in turn mounted on the drill bit.

Abstract: A cutting element for a rotary drill bit includes at least one insert of polycrystalline diamond of a kind incorporating a carbonate as a sintering binder-catalyst. The insert is mounted by being at least partly surrounded by a support body of conventional polycrystalline diamond of a kind incorporating a sintering binder-catalyst selected from cobalt and other iron group elements or alloys thereof. The insert and support body may be integrally bonded to a substrate during manufacture. Either the insert or support body may be pre-sintered or sintered during formation of the cutting element.

Abstract: A method of determining characteristics of a rotary drag-type drill bit comprises the steps of: creating a computerized representation of the cutters on the drill bit, and then, with each cutter in turn, projecting the shape of the cutter onto a fixed plane having an array of cells, and assigning a first marker to those cells of the array which overlie the projection of the selected cutter. The representations of the other cutters are then rotated about the bit axis until they have all passed through the plane at least once, the cutters also being moved axially while being rotated so as to represent the axial movement of the bit during drilling. The shapes of the other cutters are projected onto the plane, as they pass through it, and a second marker is assigned to those cells of the array which overlie both the projection of the selected cutter and the projections of any of the other cutters.

Abstract: A method is disclosed comprising the steps of locating, on a surface of a downhole component, a plurality of thermally stable polycrystalline diamond (TSP) bearing elements, and then applying to the surface a settable facing material which bonds to the surface between the bearing elements and embraces the elements to hold them in place. A method in which bearing elements each comprising a body of TSP at least partly surrounded by a layer of less hard material are secured to the surface by welding or brazing part of the surface of each bearing element which comprises said less hard material to said component is also described.

Abstract: The invention provides a method of detecting, at the surface, the occurrence of torsional vibration in a bottomhole assembly mounted on the drill string of a rotary drilling system. The method includes the steps of: ascertaining natural frequencies of torsional vibration of the bottomhole assembly prior to drilling, and noting at least one reference frequency for an integer wavelength mode of torsional vibration of the bottomhole assembly. During subsequent drilling, the drill string mean square torque at the surface is monitored for a bandwidth around the reference frequency. It is found that peaks in the mean square torque, close to the reference frequency, are indicative of the occurrence of torsional vibration in the bottomhole assembly.

Abstract: A method of predicting the walk rate of a design of rotary drag-type drill bit of the kind where the leading face of the bit body is formed with a central depression, or cone, comprises the steps of: calculating the cone volume V.sub.cone of the bit; calculating that ratio ##EQU1## of the total torque generated by the cutters on the bit which is attributable to those cutters which are mounted in said cone; calculating a Walk Factor ##EQU2## and then determining the predicted walk rate W of the bit from a graph, or other database, relating previously established values of F for other drill bits to the respective walk rates W for those drill bits.

Abstract: A cutting structure for a rotary drag-type drill bit includes a cutting element mounted on a member on the bit body, which may be a carrier secured to the bit body or part of the bit body itself. The surface of the member on which the cutting element is mounted is formed with a groove, adjacent the cutting element. The downstream end of the groove is located near a nozzle in the bit body through which a jet of drilling fluid emerges, so that the groove directs to the front of the cutting element the flow of drilling fluid which impinges on the groove. An array of separate grooves may lead from the nozzle to different cutting elements. The flow of drilling fluid directed towards each cutting element serves to break up cuttings removed from the formation by the cutting element and to carry the cuttings away from the element.

Abstract: A method of determining wear characteristics of a rotary drag-type drill bit comprises the steps of: determining the location and shape of a datum profile for the cutters on the bit body: determining the location and shape of a reference profile located inwardly of the datum profile; and ascertaining the volume of superhard material in the cutters between the datum profile and the reference profile. The volume of superhard material in the cutters at discrete radial locations is then plotted against the radial distance of the material from the axis of rotation of the bit body. The predicted wear rate WR.sub.r of superhard material at radius r is also calculated as a function of the volume and the predicted wear rate is plotted against r. The type and location of the cutters may then be modified, if necessary, to give a wear rate which is substantially constant across the radius of the drill bit.

Abstract: A rotary drill bit is manufactured by a powder metallurgy process by placing a metal mandrel in a mold, packing the mold with particulate matrix-forming material, infiltrating the material with a molten binding alloy, and cooling the assembly to form a solid infiltrated matrix bonded to the mandrel. The mandrel comprises an outer part surrounded by the matrix-forming material and an inner part, secured to the outer part but out of contact with the matrix-forming material. The outer part of the mandrel is formed from a material having thermal characteristics close to those of the matrix, so as to reduce the tendency for the matrix to crack under thermal stress, while the inner part of the mandrel is formed from a precipitation-hardening material, the strength and hardness of which increases in the infiltration process and the subsequent heating/cooling cycle for brazing the cutters on to the drill bit.

Abstract: A preform cutting element, for a rotary drag-type drill bit, includes a facing table of polycrystalline diamond having a front face, a peripheral surface, and a rear surface bonded to the front surface of a tungsten carbide substrate. The facing table has at least one peripheral locking portion projecting rearwardly from the rear surface of the facing table into the substrate, the inner surface of the locking portion and the adjacent part of the substrate having interengaging formations whereby part of the substrate overlies at least one part of the locking portion. With this arrangement, forces acting on the facing table tending to lift it from the front surface of the substrate are resisted by the portion of the substrate which overlies the part of the locking portion.