A method for making a cutter element

Abstract

A method of making a cutter element for use in an earth-boring tool, the method includes forming the cutter element to comprise a body of super hard polycrystalline material bonded to a substrate along an interface. The substrate has a distal free end opposite said interface and is formed of a different material to the super hard polycrystalline material. The method includes treating an exterior surface of the body of super hard polycrystalline material and an exterior surface of the substrate by pulsing a laser onto the exterior surface of the body of super hard polycrystalline material and the exterior surface of the substrate under two or more identical machining conditions.

Description

[0001] [OFFICIAL]

[0002] PF1631 -WO-0

[0003] A METHOD FOR MAKING A CUTTER ELEMENT

[0004] Field

[0005] This disclosure relates generally to a method for making a cutter element, for example a cutter element for drilling in the oil and gas industry or as an insert for machine tools.

[0006] Background

[0007] In various fields such as earth-boring, road milling, and mining, tough materials such as rock, asphalt, or concrete are engaged and degraded using cutter elements that are typically coupled to a movable body such as a drill bit secured to a drill string to bring the cutter elements into contact with the material to be degraded as the body moves. For example, when exploring for or extracting subterranean oil, gas, or geothermal energy deposits, a plurality of cutter elements are typically secured to a drill bit attached to the end of a drill string and, as the drill bit is rotated, the cutter elements degrade a subterranean formation forming a wellbore, which allows the drill bit to advance through the formation. In another example, when preparing an asphalt road for resurfacing, cutter elements are typically coupled to tips of picks that may be connected to a rotatable drum. As the drum is rotated, the cutter elements degrade the asphalt leaving a surface ready for application of a fresh layer.

[0008] The cutter elements used in such applications often include super-hard materials, such as polycrystalline diamond material, sintered to a substrate material such as tungsten carbide, in a high-pressure, high-temperature environment. These cutter elements typically include a cutting edge formed in the super-hard material designed to scrape against and shear away a surface. While effective in cutting formation or other materials, such cutter elements may be susceptible to chipping, cracking, or partial fracturing when subjected to high forces.

[0009] In drilling operations, a cutter element, also termed an insert, is subjected to heavy loads and high temperatures at various stages of its useful life. In the early stages of drilling, when the sharp cutting edge of the insert contacts the subterranean formation, it is [OFFICIAL]

[0010] PF1631 -WO-0 subjected to large contact pressures. This results in the possibility of a number of fracture processes such as fatigue cracking being initiated. As the cutting edge of the insert wears, the contact pressure decreases and is generally too low to cause high energy failures. However, this pressure can still propagate cracks initiated under high contact pressures and may eventually result in spalling-type failures. In the drilling industry, PCD cutter performance is determined by a cutter's ability to achieve high penetration rates in increasingly demanding environments, and still retain a good condition post-drilling (enabling re-use if desired). In any drilling application, cutters may wear through a combination of smooth, abrasive type wear and spalling / chipping type wear. Whilst a smooth, abrasive wear mode is desirable because it delivers maximum benefit from the highly wear-resistant PCD material, spalling or chipping type wear is unfavourable. Even fairly minimal fracture damage of this type can have a deleterious effect on both cutting life and performance.

[0011] Cutting efficiency may be rapidly reduced by spalling-type wear as the rate of penetration of the drill bit into the formation is slowed. Once chipping begins, the amount of damage to the diamond table continually increases, as a result of the increased normal force required to achieve a given depth of cut. Therefore, as cutter damage occurs and the rate of penetration of the drill bit decreases, the response of increasing weight on bit may quickly lead to further degradation and ultimately catastrophic failure of the chipped cutter element.

[0012] It has been appreciated that cutter elements and machine tool cutting inserts having cutting surfaces with non-planar, shaped topographies or topologies may be advantageous in various applications. In particular, the surface features and / or shape of the cutting surface may be beneficial in use to divert, for example, chips from the working surface being worked on by the cutter or machine tool, and / or in some instances to act as a chip breaker, with a view to reducing the risk of chipping, or cracking, thereby extending the working life of the cutter element. It has further been appreciated that cutter elements and machine tool cutting inserts that are shaped to provide a non-cylindrical cross-section may also be advantageous in various applications. [OFFICIAL]

[0013] PF1631 -WO-0

[0014] Conventional processing techniques to achieve the final desired shape or surface geometry of such cutting (cutter) elements typically include lapping and / or grinding of the cutter element and may additionally or instead include a laser processing of the cutting surface. However, with increasing complexity of surface geometry designs, conventional lapping and / or grinding techniques may be unsuitable and / or extremely time consuming. Furthermore, conventional cutter elements for drilling in the oil and gas industry are typically formed of a body of super hard material such as polycrystalline diamond material (PCD) bonded to a substrate formed of another material, typically cemented tungsten carbide. To apply a surface geometry or shape to both bodies of material forming such cutter elements without damaging one or other material which could impact performance of the final cutter element is conventionally challenging, and time consuming, due to the different material properties and characteristics of the materials including rates of thermal expansion and degradation, and removal rates so multiple lasers configured to cut the different materials are typically used and manufacturers and users of such cutter elements continually seek improved manufacturing methods.

[0015] There is a need to provide a method of forming super-hard inserts such as inserts for cutting or machine tools such as cutter elements with an applied surface geometry or shape extending through the body of superhard material and substrate attached thereto.

[0016] Summary

[0017] Viewed from a first aspect there is provided a method of making a cutter element for use in an earth-boring tool, the method comprising: forming the cutter element to comprise a body of super hard polycrystalline material bonded to a substrate along an interface, wherein the substrate comprises a distal free end opposite said interface, the substrate being formed of a different material to the super hard polycrystalline material, the cutter element having a longitudinal axis; the method further comprising: treating an exterior surface of the body of super hard polycrystalline material and an exterior surface of the substrate by pulsing a laser onto the exterior surface of the body of [OFFICIAL]

[0018] PF1631 -WO-0 super hard polycrystalline material and the exterior surface of the substrate under two or more identical laser machining conditions.

[0019] Viewed from a second aspect there is provided a cutter element formed according to the above defined method.

[0020] Viewed from a third aspect there is provided a drill bit or a component of a drill bit for boring into the earth, comprising one or more of the above defined cutter elements.

[0021] Brief description of the drawings

[0022] Various examples are now described with reference to the accompanying drawings in which:

[0023] Figure 1 is a schematic drawing of a conventional PCD construction used as a cutter or cutting element comprising a PCD structure bonded to a substrate;

[0024] Figure 2 is a schematic drawing of the microstructure of a conventional body of PCD material;

[0025] Figure 3 is a schematic drawing of a conventional PCD construction used as a cutter or cutter element comprising a PCD structure bonded to a substrate having a chamfered peripheral edge to act as a cutting edge;

[0026] Figure 4 is a schematic perspective view from above and one side of a cutter element formed according to a first example method;

[0027] Figure 5 is a schematic side view of the cutter element of Figure 4 showing the surface geometry applied to the top working surface; and

[0028] Figure 6 is a schematic view of the process steps in an example method for making the cutter element of Figures 4 and 5. [OFFICIAL]

[0029] PF1631 -WO-0

[0030] Detailed description

[0031] Referring in general to the following description and accompanying drawings, various versions of the present disclosure are described and illustrated to show its structure and method of operation. Common elements of the illustrated examples are designated by the same reference numerals.

[0032] As used herein, “drill bit” means and includes any type of bit or tool used for drilling during the formation or enlargement of a wellbore in subterranean formations and includes, for example, fixed cutter bits, rotary drill bits, percussion bits, core bits, eccentric bits, bi-center bits, reamers, mills, drag bits, roller cone bits, hybrid bits and other drilling bits and tools known in the art.

[0033] As used herein, a “superhard material” is a material having a Vickers hardness of at least about 28 GPa. Diamond and cubic boron nitride (cBN) material are examples of superhard materials.

[0034] As used herein, a “superhard construction” means a construction comprising a body of polycrystalline superhard material. In such a construction, a substrate may be attached thereto.

[0035] As used herein, polycrystalline diamond (PCD) is a type of polycrystalline superhard (PCS) material comprising a mass of diamond grains, a substantial portion of which are directly inter-bonded with each other and in which the content of diamond is at least about 80 volume percent of the material. In one example of PCD material, interstices between the diamond grains may be at least partly filled with a binder material comprising a catalyst for diamond. As used herein, “interstices” or “interstitial regions” are regions between the diamond grains of PCD material. In examples of PCD material, some or all interstices or interstitial regions may be substantially or partially filled with a material other than diamond, or they may be substantially empty. PCD material may comprise at least a region from [OFFICIAL]

[0036] PF1631 -WO-0 which catalyst material has been removed from the interstices, leaving interstitial voids between the diamond grains.

[0037] Cutter elements for use in drill bits in the oil and gas industry typically comprise a layer of polycrystalline diamond (PCD) bonded to a cemented carbide substrate. PCD material is typically made by subjecting an aggregated mass of diamond particles or grains to an ultra- high pressure of greater than about 5 GPa, and temperature of at least about 1200°C, typically about 1440°C, in the presence of a sintering aid, also referred to as a solventcatalyst material for diamond. Solvent-catalyst materials for diamond are understood to be materials that are capable of promoting direct inter-growth of diamond grains at a pressure and temperature condition at which diamond is thermodynamically more stable than graphite.

[0038] Examples of solvent-catalyst materials for diamond are cobalt, iron, nickel and certain alloys including alloys of any of these elements.

[0039] As used herein, PCBN (polycrystalline cubic boron nitride) material refers to a type of superhard material comprising grains of cubic boron nitride (cBN) dispersed within a matrix comprising metal or ceramic.

[0040] The term "substrate" as used herein means any substrate over which the superhard material layer is formed. For example, a "substrate" as used herein may be a transition layer formed over another substrate.

[0041] The superhard construction shown in the figures may be suitable, for example, for use as a cutter insert for a drill bit for boring into the earth. Such an earth-boring drill bit (not shown) includes a plurality of cutter elements, and typically includes a bit body which may be secured to a shank by way of a threaded connection and / or a weld extending around the earth-boring drill bit on an exterior surface thereof along an interface between the bit body and the shank. A plurality of cutter elements are attached to a face of the bit body, one or more of which may comprise a cutter element as described herein in further detail below. [OFFICIAL]

[0042] PF1631 -WO-0

[0043] Figures 1 and 2 show a conventional polycrystalline composite construction 1 , 1’ for use as a cutter insert for a drill bit (not shown) for boring into the earth. The polycrystalline composite compact or construction 1 , T comprises a body of polycrystalline super hard material 2, 2’ integrally bonded at an interface 12 to a substrate 10. The super hard material may be, for example, polycrystalline diamond (PCD) and the super hard particles or grains may be of natural or synthetic origin.

[0044] The substrate 10 may be formed of a hard material such as a cemented carbide material and may be, for example, cemented tungsten carbide. The binder metal for such carbides suitable for forming the substrate 10 may be, for example, nickel, cobalt, iron or an alloy containing one or more of these metals. Typically, this binder will be present in an amount of 10 to 20 mass %, but this may be as low as 6 mass % or less. Some of the binder metal may infiltrate the body of polycrystalline super hard material 2, 2’ during formation of the compact 1 , T.

[0045] As shown in Figure 2, during formation of the polycrystalline composite construction 1 , T, the interstices 24 between the grains 22 of super hard material such as diamond grains in the case of PCD, may be at least partly filled with a non-super hard phase material. This non-super hard phase material, also known as a filler material may comprise residual catalyst / binder material, for example cobalt, nickel or iron.

[0046] The polycrystalline composite construction 1 , T when used as a cutter element may be mounted in use in a bit body, such as a drag bit body (not shown).

[0047] The substrate 10 may be, for example, generally cylindrical having a peripheral surface 3, a peripheral top edge 8 and a distal free end.

[0048] The exposed surface of the super hard material 4 opposite to the interface 8 along which the super hard material is bonded to the substrate 10 forms or comprises a working surface which also acts as a rake face in use. In some conventional cutter elements such as that shown in Figure 3, a chamfer 28 typically extends between the working surface 4 and a [OFFICIAL]

[0049] PF1631 -WO-0 cutting edge 6, and at least a part of a flank or barrel 2 of the cutter element, the cutting edge 36 being defined by the edge of the chamfer 28 and the flank 2.

[0050] The working surface or “rake face” 4 of the polycrystalline composite construction 1 , T is the surface or surfaces over which the chips of material being cut flow when the cutter is used to cut material from a body, the rake face 4 directing the flow of newly formed chips. This face 4 is commonly also referred to as the top face or working surface of the cutter element as the working surface 4 is the surface which, along with its edge 6, is intended to perform the cutting of a body in use. It is understood that the term “cutting edge”, as used herein, refers to the actual cutting edge, defined functionally as above, at any particular stage or at more than one stage of the cutter wear progression up to failure of the cutter, including but not limited to the cutter in a substantially unworn or unused state.

[0051] As used herein, “chips” are the pieces of a body removed from the work surface of the body being cut by the polycrystalline composite construction 1 , T in use.

[0052] As used herein, the “flank” 2 of the cutter is the surface or surfaces of the cutter that passes over the surface produced on the body of material being cut by the cutter and is commonly referred to as the side or barrel of the cutter. The flank 2 may provide a clearance from the body and may comprise more than one flank face.

[0053] As used herein, a “wear scar” is a surface of a cutter formed in use by the removal of a volume of cutter material due to wear of the cutter. A flank face may comprise a wear scar. As a cutter wears in use, material may progressively be removed from proximate the cutting edge, thereby continually redefining the position and shape of the cutting edge, rake face and flank as the wear scar forms.

[0054] With reference to Figure 3, the chamfer 28 is formed in the structure adjacent the cutting edge 6 and flank or barrel surface 2.

[0055] The rake face 4 is joined to the flank 2 by the chamfer 28 which extends from the cutting edge 6 to the rake face 4, and lies in a plane at a predetermined angle to the plane [OFFICIAL]

[0056] PF1631 -WO-0 perpendicular to the plane in which the longitudinal axis of the cutter extends. In some examples, this chamfer angle is up to around 45 degrees. The vertical height of the chamfer 28 may be, for example, between 350pm and 450pm, such as around 400pm.

[0057] The substrate 10 has an exposed distal end surface 29 opposite to the interface 12.

[0058] The conventional cutter elements shown in Figure 1 to 3 are typically cylindrical in shape with a substantially planar cutting surface 4.

[0059] A cutter element 60 formed according to a first example method is shown in Figures 4 and 5 and comprises a body of polycrystalline super hard material 62 integrally bonded at an interface 34 to a substrate 40. The super hard material 62 may be, for example, polycrystalline diamond (PCD) and the super hard particles or grains may be of natural or synthetic origin.

[0060] The substrate 40 may be formed of a hard material such as a cemented carbide material and may be, for example, cemented tungsten carbide, cemented tantalum carbide, cemented titanium carbide, cemented molybdenum carbide or mixtures thereof. The binder metal for such carbides suitable for forming the substrate 40 may be, for example, nickel, cobalt, iron or an alloy containing one or more of these metals. Typically, this binder will be present in an amount of 10 to 20 mass %, but this may be as low as 6 mass % or less.

[0061] The substrate 40 has a peripheral surface 38, a distal free end 36 and a peripheral top edge 34 forming an interface with a body of superhard polycrystalline material 62. At the distal free end 41 , the cross sectional outline of the substrate may be generally cylindrical.

[0062] The body of superhard material 62 comprises a substantially cylindrical first region 71 bonded to the substrate 40 along the interface 34 and has a longitudinal axis. A further region 66 extends therefrom to an exposed upper surface 65 of the super hard material 62 opposite the substrate 40 which forms or comprises a working surface, also termed a cutting face which also acts as a rake face in use. This working surface 65 has a recessed portion 67 extending into and from the working surface 65 towards the interface 34. The recessed [OFFICIAL]

[0063] PF1631 -WO-0 portion 67 is substantially non-planar and may, in some examples, be generally concave, and / or have one or more regions that includes a plurality of interconnecting concave portions, or a concave portion and a convex portion, form an undulating profile, or may have one or more protrusions or troughs any or all of which may assist in reducing drag on the lateral surface of the cutter element in use and may improve cutting efficiency by controlling chip flow over the external surfaces of the cutter element 60.

[0064] The body of polycrystalline super hard material 62 may be attached to the substrate 40 by, for example, conventional brazing techniques or by sintering a body of diamond grains together with a pre-formed substrate 40 using a conventional high pressure and high temperature technique. The body of super hard material 62 has a non-cylindrical crosssection in a plane perpendicular to a plane through which the longitudinal axis extends. In the example of Figure 4, the peripheral side surface of the body of super hard polycrystalline material has two planar surface regions 66, wherein adjacent planar surface regions are spaced by a respective arcuate surface region 68 extending therebetween.

[0065] As shown in Figure 4, at least one arcuate surface region of the body of super hard polycrystalline material may beveled to form a chamfer 71 and define a cutting edge and the planar surface regions 55 in the peripheral side surface of the substrate 40 are flush with the two planar surface regions 66 of the body of super hard polycrystalline material.

[0066] Figure 6 is a schematic view of the process steps in an example method for making the cutter element of Figures 4 and 5. In a first stage 100, a cutter element having a body of super hard polycrystalline material bonded to a substrate along an interface is formed according to one or more of the methods described below. The substrate is formed of a different material to the super hard polycrystalline material. In a second stage 120, an exterior surface of the body of super hard polycrystalline material and an exterior surface of the substrate are treated by pulsing a laser onto the exterior surface of the body of super hard polycrystalline material and the exterior surface of the substrate under two or more identical laser machining conditions. [OFFICIAL]

[0067] PF1631 -WO-0

[0068] Examples of such laser machining conditions may include but are not limited to any one or more of a pulse length of the laser, an average output power of the laser, a peak output power of the laser, a frequency of the laser, a wavelength of the laser, a spot size of the laser, a depth of focus of the laser, a dwell time of the laser, a pulse duration of the laser, a pulse energy of the laser, a scan speed of the laser, and a pulse rate of the laser.

[0069] The example method may also include a further stage, either before or after the stage 120 of treating the exterior surfaces, such as treating the cutter element using, for example, a conventional acid leaching treatment to remove at least a portion of residual metal solvent catalyst material from a plurality of the interstitial spaces, resulting in a plurality of the interstitial spaces being substantially free of metal solvent catalyst material in the example where the body of super hard polycrystalline material is a polycrystalline diamond material having inter-bonded diamond grains with interstitial spaces between the inter-bonded diamond grains.

[0070] In the example method, the stage 120 may include treating the exterior surfaces of the polycrystalline super hard material and the substate in a single stage to remove super hard material and substrate material in a single method stage, using a single laser to treat both materials of the cutter element.

[0071] In some examples, the type of laser used may be a 500W nanosecond laser, and the stage 120 of treating the exterior surfaces may include treating the surfaces with the laser generating a power of less than around 500W.

[0072] In the example method, the stage 120 may include treating the exterior surfaces by orienting a beam from the laser to target the exterior surfaces at an angle of incidence of between around 1 ° and 90°.

[0073] In some examples, the stage 120 of treating the exterior surfaces includes pulsing the laser to remove one or more grain layers to a depth of up to around 6 microns of super hard material and substrate material from the exterior surfaces by passing the exterior surfaces [OFFICIAL]

[0074] PF1631 -WO-0 through the laser beam or passing the laser beam over said surfaces in a scanning pattern a plurality of times.

[0075] In some examples the pulse duration may be between around 30 nanoseconds to around 90 nanoseconds.

[0076] In the example of Figure 4, the surface of the substrate 40 is treated to remove substrate material up to a distance spaced from the distal end thereof, and such a distance may, in some examples be between around 3 to around 4mm from said distal free end.

[0077] After stage 120 of treating the exterior surfaces with a laser, a residue material may be deposited on or formed on the exterior surfaces which have been treated or exposed untreated surfaces, and, in a further stage of the example method, the cutter element may be cleaned after stage 120 to remove any such undesired residue material. Alternatively or in addition, the method may include masking one or more portions of the exterior surfaces of any one or more of the substrate and body of super hard material prior to treating in stage 120 to reduce cleaning requirements and protect the materials. In some examples, the masking may include applying a coating to a portion(s) of the exterior surfaces and / or positioning a cap or cover over said one or more portions of the exterior surfaces.

[0078] Example techniques for cleaning the treated cutter element may include a sandblasting technique to clean said surfaces.

[0079] As shown in Figure 4, the example method may be used to create, for example a cutter element in which the exterior surfaces are shaped such that the substrate and the body of super hard polycrystalline material have a non-circular cross section in a plane perpendicular to a plane through which the longitudinal axis extends, peripheral side surfaces of the substrate and the body of supe hard polycrystalline material having two or more planar surface regions, and adjacent planar surface regions are spaced by a respective arcuate region 68 extending therebetween. [OFFICIAL]

[0080] PF1631 -WO-0

[0081] Additionally, as shown in Figure 5, stage 120 of the example method may include treating a working top exterior surface of the body of super hard polycrystalline material to create a non-planar topography or topology.

[0082] The stage 110 of forming the cutter element to have a body of super hard polycrystalline material bonded to a substrate along an interface may be as follows. In a first step, the substrate 40 may be formed.

[0083] In some examples, the substrate 40 may be formed of a cemented carbide material such as tungsten carbide (WC) including a binder phase. The binder phase may include, for example, any one or more of a solid solution of Re, carbon and W and / or any one of more of Fe, Co, and Ni. In some examples, the binder phase may have at least about 0.1 weight percent to at most about 5 weight percent of one or more of V, Cr, Ta, Ti, Mo, Zr, Nb and Hf in solid solution and / or in the form of carbide compounds. In some other examples, the material forming the substrate 30 may have at least about 0.01 weight percent and at most about 2 weight percent of one or more of Ru, Rh, Pd, Os, Ir and Pt.

[0084] An example of a cemented carbide material for use as a substrate 40 in an example polycrystalline super hard construction may be made by a method including milling a cemented carbide mixture containing WC with any one or more of Re, Co, Ni and / or Fe and optionally grain growth inhibitors including V, Cr, Ta, Ti, Mo, Zr, Nb and Hf or their carbides and then pressing a cemented carbide article from the mixture. The article is then sintered at temperatures of above 1450°C in vacuum for 1 to 10 min and afterwards under pressure of Ar (HIP) for 5 to 120 min. The article is then cooled from the sintering temperatures to approximately 1300 degrees Centigrade (°C) in an atmosphere comprising inert gases, nitrogen, hydrogen or a mixture thereof, or in a vacuum, at a cooling rate of approximately 0.2 to 2 degrees per minute.

[0085] In some examples, the substrate 40 may include excess carbon which is understood to be carbon that is in excess of the diamond of the diamond grains provided in an aggregated mass for sintering PCD which is to be bonded to the substrate in the formation of a super [OFFICIAL]

[0086] PF1631 -WO-0 hard construction such as the cutter element of Figure 4, and is also in excess of the carbon included as the carbide of the cemented carbide (stochiometric excess). A carburised substrate or carburised substrate assembly is therefore a substrate or substrate assembly including excess carbon.

[0087] Carbon may be introduced into the substrate 40 in any of a number of ways. In one example a substrate pre-form is prepared by a method including introducing diamond particles into the starting powders for making a cemented carbide to form a starting powder blend; forming the starting powder blend by means of compaction in a mold to form a green body; and sintering the green body at a temperature of greater than about 1 ,400 degrees centigrade at an applied pressure of less than about 1 GPa to produce a sintered substrate. At least some of the diamond particles are converted wholly or partially into graphite during this carbide sintering step, because the pressure is below that for diamond to be thermodynamically stable.

[0088] The sintering pressure at which diamond is thermodynamically stable is preferably at least about 5.5GPa and the temperature is preferably at least about 1 ,400 degrees centigrade.

[0089] In some examples, carbon may be introduced into the substrate in the form of graphite powder.

[0090] In other examples, carbon may be introduced into the substrate in the form of carbonaceous gas, which is caused to permeate or infiltrate the substrate.

[0091] In still further examples, material comprising carbon may be sprayed onto a surface of the substrate. In particular, powder containing cobalt, carbon and tungsten may be deposited onto the substrate surface by means of thermal spraying.

[0092] In other examples, the substrate may be coated with a source of excess carbon, such as graphite. [OFFICIAL]

[0093] PF1631 -WO-0

[0094] In some examples, the substrate is prepared from starting carbide powder having a high content of carbon in the form of carbon black, for example.

[0095] In other examples, a substrate with high carbon content may be prepared by avoiding the removal of some carbon during the preparation of the green body for readiness for sintering. Typically, a green body is heat treated to remove binder or pressing aid material prior to sintering, and carbon is removed during this process. In one example, this process is not thoroughly completed, leaving at least some carbon of binder origin within the green body.

[0096] In one example, the method includes forming a carburised substrate, wherein the source of excess carbon is included in or introduced into the volume of the substrate. In some examples the source of excess carbon is dispersed substantially throughout the entire volume of the carburised substrate. In other examples the source of excess carbon is dispersed in a surface region proximate or adjacent the bonding surface.

[0097] In some examples, the mean content of the source of excess carbon within a surface region of an example carburised substrate or throughout substantially the entire carburised substrate is no greater than about 10 weight percent, more preferably no greater than about 6 weight percent and yet more preferably no greater than about 5.5 weight percent of the material in the surface region or the substrate. For example, the content of the source of excess carbon within the surface region or throughout the entire carburised substrate may be at least about 0.1 weight percent or at least about 0.3 weight percent of the material in the region. In some examples, such a surface region may extend to a depth of at least about 1 mm, at least about 2 mm, or even at least 3 mm from the interface surface 34.

[0098] In some examples, the source of excess carbon is a carbonaceous material other than metal carbide, such as carbon black powder or graphite. In one example, the source of excess carbon may be derived from diamond that has been converted into a non-diamond material. [OFFICIAL]

[0099] PF1631 -WO-0

[0100] In one example, the method includes combining source of excess carbon in particulate or granular form with raw materials for the cemented carbide, forming the combination into a substantially self-supporting green body, and sintering the green body at a pressure at which diamond is not thermodynamically stable to form the carburised substrate. In some examples the raw materials for cemented carbide comprise grains of tungsten carbide and grains comprising cobalt.

[0101] The method of forming an example substrate may include combining diamond grains with raw materials for cemented carbide, forming the combination into a substantially self- supporting green body; subjecting the green body to a temperature of at least 500 degrees centigrade and a pressure at which diamond is not thermodynamically stable to form the carburised substrate. The diamond particles may be wholly or partly converted into a nondiamond material, particularly graphite.

[0102] In a further example, a substrate element for use as the surface region of the substrate 40 for the PCD cutter element of Figures 4 and 5 may be manufactured by blending together diamond particles, tungsten carbide (WC) powder and cobalt powder, forming the blended mixture into a compacted green body, and subjecting the green body to a conventional carbide sintering process. The diamond particles may, for example, have a mean size in the range of 0.75 to 1.5 microns, and constitute 3 weight percent of the blended mixture in one example. The WC powder and the cobalt powder may be pre-mixed, the cobalt constituting 13 weight percent of the WC-Co pre-mix and the WC particles having a mean size in the range from about 1 to 4 microns. About 2 weight percent organic pressing aid may be included in the WC-Co mix in such an example. The blended powder mix may be uniaxially compacted at ambient temperature to form a substantially cylindrical green body, which may be conventionally sintered at a temperature of 1 ,400 degrees centigrade for 2 hours to form a sintered article. By the end of the sintering process, the diamond particles may have completely converted into graphite.

[0103] To form an example super hard polycrystalline construction 60 such as that shown in Figure 4, a layer comprising an unbonded aggregated mass of, for example, diamond grains, may [OFFICIAL]

[0104] PF1631 -WO-0 be deposited onto the interface surface of the substrate 40 formed by example using any one of the above-described methods, to form an unbonded pre-sinter assembly. The assembly may be mounted within a capsule for an HPHT furnace, as is known in the art. The capsule may be subjected to a pressure of at least about 5.5 GPa and a temperature of at least about 1 ,250 degrees centigrade or more for a period of between about 5 minutes to about several hours. After sintering, the substrate element will be bonded to a body of PCD material generated during the sintering process along the interface 34 to form a PCD construction for treatment in the further stage 120 to form the cutter element 60.

[0105] In some examples, the pre-sinter assembly may be subjected to a pressure of at least about 6 GPa, at least about 6.5 GPa, at least about 7 GPa or even at least about 8 GPa.

[0106] The durability of the cutter product 60 may be further enhanced if the super hard material layer 62 is leached of catalyst material, either partially or fully, in subsequent processing, or subjected to a further high pressure high temperature sintering process. The leaching may be performed whilst the super hard material layer 62 is attached to the substrate 40 using conventional leaching techniques known in the art such that at least a portion of the interstitial spaces between inter-bonded super hard grains, such as diamond grains in the case of PCD material, being substantially free of metal solvent catalyst material.

[0107] As described above, the exposed outer surface of the body of super hard polycrystalline material 62 which forms the working surface 65 may be substantially planar or, as shown in the example of Figure 5 it may have a non-planar topography or topology in the form of a surface geometry applied thereto, for example as part of the treatment stage 120, or formed therein.

[0108] As mentioned above, the super hard material 62 may be, for example, polycrystalline diamond (PCD) and the super hard particles or grains may be of natural or synthetic origin. In some examples, the cutter elements may comprise cBN material. Examples of diamond material may include polycrystalline diamond (PCD) material, thermally stable PCD material, crystalline diamond material, diamond material made by means of a chemical [OFFICIAL]

[0109] PF1631 -WO-0 vapour deposition (CVD) method or silicon carbide bonded diamond. An example of cBN material is polycrystalline cubic boron nitride (PCBN).

[0110] Also, the substrate 40 may be formed of a hard material such as a cemented carbide material and may be, for example, cemented tungsten carbide, cemented tantalum carbide, cemented titanium carbide, cemented molybdenum carbide or mixtures thereof. The binder metal for such carbides suitable for forming the substrate 60 may be, for example, nickel, cobalt, iron or an alloy containing one or more of these metals. Typically, this binder will be present in an amount of 10 to 20 mass %, but this may be as low as 6 mass % or less.

[0111] In some examples, both the bodies of, for example, diamond and carbide material plus sintering aid / binder / catalyst are applied as powders and sintered simultaneously in a single UHP / HT process.

[0112] In another example, the substrate may be pre-sintered in a separate process before being bonded to the superhard material in the HP / HT press during sintering of the superhard polycrystalline material.

[0113] As described above, after forming the cutter element in the first method stage, 100, the second method stage 120 includes laser shaping an exterior surface of the superhard material and an exterior surface of the substrate to ablate selected regions of the superhard material and substrate thereby forming the cutter element into a selected shape and size by directing a plurality of laser pulses from a laser onto said exterior surfaces.

[0114] In the second stage 120, the cutter element to be shaped is positioned proximate a laser and the method stage 120 may include at least one of moving the cutter element relative to the laser, moving the laser relative to the cutter element, or directing (e.g., via a mirror) the plurality of laser pulses to ablate selected volumes or regions of cutter element.

[0115] The laser may include any suitable laser, for example, the laser may include a pulse laser, a carbon dioxide laser, a ytterbium laser, a diode laser, a CNC laser. In an example, the laser may include one or more lenses such as a flat field scanning (F theta) lens and / or [OFFICIAL]

[0116] PF1631 -WO-0 mirror that move such that the laser pulses controllably ablate different portions of the cutter element. Whilst not wishing to be bound by theory, it is believed the use of an F Theta lens may assist in allowing the laser beam to remain in focus across the full scanning area with minimal optical distortion.

[0117] The laser emits the laser pulses exhibiting characteristics that are configured to ablate external surface portions of both the superhard material and the substrate material under two or more identical machining conditions.

[0118] In an example, the laser in the second method stage 120 may emit the laser pulses at an average output power of up to about 515 Watts.

[0119] In an example, the laser in the second method stage 120 emit the laser pulses at a pulse repetition frequency of about 25 kHz to about 8000 kHz.

[0120] In an example, the laser in the second method stage 120 may emit the laser pulses at wavelength of between about 1000 microns to about 1070 microns, such as at ranges of between about 1062 microns to about 1066 microns.

[0121] In an example, the laser in the second method stage 120 may emit the laser pulses at pulse duration of between about 20 nanoseconds (“ns”) to about 280 nanoseconds, for example between around 27 ns to around 270 ns. In some examples, nominal pulse lengths used may be around 30ns, 60ns, 120ns, and / or 240ns. Control and selection of pulse lengths in these ranges are believed to reduce the thermal effects on the materials being treated. In particular, whilst not wishing to be bound by any theory, it is believed that use of nanosecond range pulse lengths may assist in balancing the removal rate of the material being ablated whilst minimizing thermal damage.

[0122] In an example, the laser in the second method stage 120 may emit the laser pulses at beam diameter (which is output from the laser before focusing) of between about 5 mm and about 10 mm, such as at ranges of about 6mm to about 9mm. [OFFICIAL]

[0123] PF1631 -WO-0

[0124] In an example, the laser in the second method stage 120 may have a beam quality (M2) of about 1 to about 2, such as in ranges of about 1.2 to about 1.8, or around 1.5 in some examples.

[0125] In an example, the laser in the second method stage 120 may have a nominal pulse energy of about 0.5mJ to about 2.1 mJ, such as in ranges of about 0.5mJ to about 2.06mJ, or around 0.51 mJ in some examples.

[0126] In an example, the laser in the second method stage 120 may have a scanning speed of up to around 20mm / s, such as in ranges of around Omm / s to around 16mm / s, or around 3.5mm / s in some examples.

[0127] In an example, the laser in the second method stage 120 may have a final machining lens focal length of about 20mm to about 300mm, such as in ranges about 25mm to about 300mm, or around 167mm.

[0128] In an example, the laser in the second method stage 120 may have a spot size of between around 10 microns to around 120 microns, such as in ranges around 15 microns to around 100 microns, and in some examples around 52.2 microns.

[0129] In any one or more examples, in the second method stage 120, the average output power, average power per pulse, frequency, wavelength, pulse duration, beam diameter, or beam divergence of the laser pulses or any other laser machining conditions may be less than or greater than any of the above values.

[0130] Any combination of two or more laser machining conditions (parameters) of the methods disclosed above may be used to effectively ablate selected regions of the exterior surfaces of the substrate and superhard materials with high precision.

[0131] In the second method stage 120, the laser used to treat the cutter element may be communicably coupled to a controller configured at least to partially control the operation of the laser with or without user input. For example, the controller may direct the laser to [OFFICIAL]

[0132] PF1631 -WO-0 emit the laser pulses and may move the laser relative to the cutter element using computer executable instructions such as operational instructions to start / cease ablating the cutter element, the selected shape of the cutter element, the characteristics of the laser pulses or other suitable instructions.

[0133] In an example, the second method stage 120 may include using machining techniques such as grinding, lapping, electrical discharge machining, other than a laser processing technique to shape the cutter element prior to laser ablation, for example to form the cutter element into a rough approximation of the desired shape and the cutter element may then be shaped using the laser pulses. Using machining techniques other than laser machining to shape the cutter element prior to laser ablation may be quicker than shaping the entire cutter element solely by using the laser which can then be used to form a topography or shape that is difficult to form using the physical machining techniques.

[0134] Conventionally, to apply a surface geometry or shape to both bodies of material forming such cutter elements without damaging one or other material which could impact performance of the final cutter element multiple different lasers and / or multiple different laser machining conditions / parameters have conventionally been required to cut the superhard material and different material of the substrate bonded thereto due to the different material properties and characteristics of the materials including rates of thermal expansion and degradation, and removal rates which would otherwise affect the wear resistance one or other or both of the superhard material and substrate material.

[0135] In examples, an alternative method to conventional machining techniques to form a cutter element includes treating an exterior surface of the body of super hard polycrystalline material and an exterior surface of the substrate by pulsing a laser onto the exterior surface of the body of super hard polycrystalline material and the exterior surface of the substrate under two or more identical laser machining conditions such as any one or more of a pulse length of the laser, an average output power of the laser, a peak output power of the laser, a frequency of the laser, a wavelength of the laser, a spot size of the laser, a depth of focus of the laser, a dwell time of the laser, a pulse duration of the laser, a pulse energy of the [OFFICIAL]

[0136] PF1631 -WO-0 laser, a scan speed of the laser, and a pulse rate of the laser, and in some examples treating the surfaces in a single stage to remove super hard material and substrate material. Maintaining two or more laser machining conditions identical such as, for example, scan speed and average output power, it is believed a balance may assist in achieving a similar rate of removal for both the superhard material and the substrate material for the full laser machining processing treatment cycle which may assist in reducing the risk of the facet at the superhard material and substrate material being at different angles and assist in exceeding the ablation threshold for both the superhard material and substrate materials. If only one is exceeded such as that of the superhard material, the substrate material for example may be left largely unmachined though likely thermally damaged.

[0137] Whilst not wishing to be bound by a particular theory, the example method of forming cutter elements is therefore believed to assist in providing an economical and efficient method of producing complex and simple shaped cutter elements and surface geometries to improve rock cutting efficiency over conventional PCD cutters.

[0138] The cutter elements 60 of the types shown in Figures 4 and 5 may be provided along blades on the face of a drill bit body (not shown). The cutter elements may be secured to the bit body within pockets therein using, for example a conventional brazing process. Then, in use, the cutter element 60 shears away the surface of the underlying formation and wear scar forms progressively in the superhard material in the region of the cutting edge. As used herein, a “wear scar” is a surface of the cutter formed in use by the removal of a volume of cutter material due to wear of the cutter. As a cutter wears in use, material may progressively be removed from proximate the cutting edge, thereby continually redefining the position and shape of the cutting edge, rake face and flank as the wear scar forms.

[0139] In some examples, the base of the substrate 40 of the cutter elements may have a generally cylindrical shape. In other examples, different shapes may be desired such as conical, or ovoid. Furthermore, in examples where the insert is used as a cutter element, for example for drilling in the oil and gas industry, the cross-sectional shape of the cutter element may be chosen and any surface topography may be chosen and used to direct or divert the rock [OFFICIAL]

[0140] PF1631 -WO-0 or earth away from the drill bit to which the cutter is attached. Alternatively or additionally, for such uses or when used as an insert for a machine tool for machining a work piece, the shape and surface topography may act as a chip breaker suitable for controlling aspects of the size and shape of chips formed in use.

[0141] It will therefore be seen that various versions of the present disclosure include cutter elements and methods of forming same for earth-boring drill bits which may enhance the working life of the cutter elements by one or more of improving the abrasion resistance, thermal stability, durability, sharpness of the cutting edge, spall resistance, and fracture / impact resistance, potentially by cutting the rock more efficiently through the rock crushing action and control of chip and drilling mud flow through the shapes / topography of the cutter elements and may lead to improved drill bit stability of, for example, the earthboring drill bit to which the cutter elements may be mounted.

[0142] Although the foregoing description contains many specifics, these are not to be construed as limiting the scope of the present disclosure, but merely as providing certain exemplary versions.

Claims

[OFFICIAL]PF1631 -WO-0Claims:

1. A method of making a cutter element for use in an earth-boring tool, the method comprising: forming the cutter element to comprise a body of super hard polycrystalline material bonded to a substrate along an interface, wherein the substrate comprises a distal free end opposite said interface, the substrate being formed of a different material to the super hard polycrystalline material, the cutter element having a longitudinal axis; the method further comprising: treating an exterior surface of the body of super hard polycrystalline material and an exterior surface of the substrate by pulsing a laser onto the exterior surface of the body of super hard polycrystalline material and the exterior surface of the substrate under two or more identical laser machining conditions.

2. The method of claim 1 , wherein the body of super hard polycrystalline material comprises polycrystalline diamond material having inter-bonded diamond grains with interstitial spaces between the inter-bonded diamond grains; the method further comprising treating the cutter element before treating the exterior surfaces of the body of super hard polycrystalline material and an the substrate to remove at least a portion of residual metal solvent catalyst material from a plurality of the interstitial spaces, a plurality of the interstitial spaces being substantially free of metal solvent catalyst material.

3. The method of claim 1 , wherein the body of super hard polycrystalline material comprises polycrystalline diamond material having inter-bonded diamond grains with interstitial spaces between the inter-bonded diamond grains; the method further comprising treating the cutter element after treating the exterior surfaces of the body of super hard polycrystalline material and an the substrate to remove at least a portion of residual metal solvent catalyst material from a plurality of the interstitial spaces, a plurality of the interstitial spaces being substantially free of metal solvent catalyst material.

4. The method of any one of the preceding claims, wherein the machining conditions comprise any one or more of a pulse length of the laser, an average output power of the laser, a peak output power of the laser, a frequency of the laser, a wavelength of the laser,24[OFFICIAL]PF1631 -WO-0 a spot size of the laser, a depth of focus of the laser, a dwell time of the laser, a pulse duration of the laser, a pulse energy of the laser, a scan speed of the laser, and a pulse rate of the laser.

5. The method of any one of the preceding claims, wherein treating the exterior surfaces comprises treating the surfaces in a single stage to remove super hard material and substrate material.

6. The method of any one of the preceding claims, wherein treating the exterior surfaces comprises treating the surfaces with the laser generating an average output power of less than around 515W.

7. The method of any one of the preceding claims, further comprising orienting a beam from the laser to target the exterior surfaces at an angle of incidence of between around 1 ° and 90°.

8. The method of any one of the preceding claims, wherein treating the exterior surfaces by pulsing the laser comprises removing one or more grain layers of super hard material and substrate material from the exterior surfaces by passing the exterior surfaces through the laser beam or passing the laser beam over said surfaces in a scanning pattern a plurality of times.

9. The method of any one of the preceding claims, wherein pulsing the laser comprises pulsing the laser with a pulse duration between 27 nanoseconds to 270 nanoseconds.

10. The method of any one of the preceding claims, wherein treating the exterior surfaces comprises treating the surfaces to remove substrate material up to between around 3 to around 6mm from said distal free end.

11. The method of any one of the preceding claims, further comprising masking one or more portions of the exterior surfaces of any one or more of the substrate and body of super hard material prior to treating.

12. The method of claim 12, wherein masking comprises positioning a cap or cover over said one or more portions of the exterior surfaces.[OFFICIAL]PF1631 -WO-013. The method of any one of the preceding claims, further comprising cleaning the exterior surfaces after treating said surfaces.

14. The method of claim 13, wherein cleaning comprises applying a sandblasting technique to clean said surfaces.

15. The method of any one of the preceding claims, wherein treating the exterior surfaces comprises shaping the substrate and the body of super hard polycrystalline material to have a non-circular cross section in a plane perpendicular to a plane through which the longitudinal axis extends; peripheral side surfaces of the substrate and the body of supe hard polycrystalline material having two or more planar surface regions, wherein adjacent planar surface regions are spaced by a respective arcuate region extending therebetween.

16. The method of any one of the preceding claims, wherein the body of superhard polycrystalline material comprises any one or more of polycrystalline diamond, diamondlike carbon, or cubic boron nitride of natural and / or synthetic origin.

17. The method of any one of the preceding claims, wherein treating the exterior surface of the body of super hard polycrystalline material comprises shaping said surface to comprise a non-planar topography or topology.

18. The method of any one of the preceding claims, wherein treating the exterior surfaces comprises generating a portion of the exterior surface of the substrate to comprise two or more planar surface regions, and generating a portion of the exterior surface of the body of super hard polycrystalline material to comprise two or more planar surface regions flush with the two or more planar surface regions of the substrate.

19. The method of claim 18, wherein the two or more planar surface regions of the portion of the substrate are spaced from the distal end of the substrate.

20. The method of any one of the preceding claims, wherein the substrate comprises a cemented carbide material, for example cemented tungsten carbide material.[OFFICIAL]PF1631 -WO-021. The method of claim 20, wherein the substrate further comprises tungsten carbide particles bonded together by a binder material, the binder material comprising an alloy of Co, Ni and Cr, optionally further comprising one or more of Re, Ru, Rh, Pd, Re, Os, Ir and Pt, and / or free carbon.

22. A cutter element formed by the method of any one of claims 1 to 21.

23. An earth boring drill bit comprising the cutter element of claim 22 mounted thereon or therein.

Images