FIELD

This disclosure relates to a superhard construction comprising a body of polycrystalline superhard material, a method of making a polycrystalline superhard construction, and to a wear element comprising a polycrystalline superhard construction.

BACKGROUND

Cutter inserts for machining and other tools may typically comprise a layer of polycrystalline diamond (PCD) bonded to a cemented carbide substrate. PCD is an example of a super hard material, also called super abrasive material.

Components comprising PCD are used in a wide variety of tools for cutting, machining, drilling or degrading hard or abrasive materials such as rock, metal, ceramics, composites and wood-containing materials. PCD comprises a mass of substantially inter-grown diamond grains forming a skeletal mass which defines interstices between the diamond grains. PCD material typically comprises at least about 80 volume % of diamond and may be made by subjecting an aggregated mass of diamond grains to an ultra-high pressure of greater than about 5 GPa, typically about 5.5 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 catalyst material for diamond. 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.

Catalyst materials for diamond typically include any Group VIII element and common examples are cobalt, iron, nickel and certain alloys including alloys of any of these elements. PCD may be formed on a substrate, typically formed of a hard material such as cobalt-cemented tungsten carbide, which may provide a source of cobalt catalyst material for the PCD. During sintering of the body of PCD material, a constituent of the cemented-carbide substrate, such as cobalt in the case of a cobalt-cemented tungsten carbide substrate, liquefies and sweeps from a region adjacent the volume of diamond particles into interstitial regions between the diamond particles. In this example, the cobalt acts as a catalyst to facilitate the formation of bonded diamond grains. Optionally, a metalsolvent catalyst may be mixed with diamond particles prior to subjecting the diamond particles and substrate to the HPHT process. The interstices within PCD material may at least partly be filled with the catalyst material. The intergrown diamond structure therefore comprises original diamond grains as well as a newly precipitated or re-grown diamond phase, which bridges the original grains. In the final sintered structure, catalyst/solvent material generally remains present within at least some of the interstices that exist between the sintered diamond grains. In some cases, the substrate may be brazed or otherwise joined to the body of PCD material.

Although the composition of cutting elements may vary, even between cutters to be brazed into an individual drill bit, the external geometric features of such cutting elements are often substantially identical. This may lead to difficulties in identifying individual cutting elements or distinguishing between differing cutting elements based solely on a visual inspection of the cutting elements. Externally marking cutters with identification markings using a laser is a known solution to this problem however such conventional markings may become eroded during use as the cutting element is exposed to the extreme conditions downhole during drilling. Also, to ameliorate thermal degradation when the PCD material is exposed to elevated temperatures during cutting and/or wear applications due, at least in part, to the presence of residual solvent/catalyst material in the microstructural interstices, it is usual to at least partially remove the solvent/catalyst from interstitial spaces in the PCD by, for example, chemical leaching. However, removal of the catalyst/binder from the diamond lattice structure typically renders it more brittle and prone to fracture and therefore tends to have compromised or reduced resistance to spalling. Subsequent laser processing to etch an identifier on an external surface thereof may further compromise the properties of the material which may impact its working life.

There is therefore a need to overcome or substantially ameliorate the above-mentioned problems. SUMMARY

Viewed from a first aspect there is provided a polycrystalline super hard construction comprising: a body of polycrystalline super hard material bonded to a substrate along an interface surface; the substrate comprising a first material and the body of polycrystalline super hard material comprising a second material, wherein: the first material differs from the second material in any one or more of average grain size of super hard material, coefficient of thermal expansion, super hard material grain size distribution, hardness; and indicia on at least a portion of the interface surface, the indicia comprising any one or more of letters, numbers, graphical symbols and/or combinations thereof.

Viewed from a second aspect there is provided a method of generating indicia within a polycrystalline superhard construction, the method comprising: milling a tungsten carbide powder with a binder material to form a milled powder, the binder material comprising any one or more of Co, Ni, and/or Cr, and/or a chromium carbide; compacting the milled powder to form a green body; sintering the green body in a vacuum or inert gas atmosphere to form a first precomposite body; sintering the first pre-composite body to form a cemented carbide substrate; generating indicia on a surface of the cemented carbide substrate; placing the cemented carbide substrate into a canister and adding a mass of diamond grains or particles onto the surface of the cemented carbide substrate having the indicia thereon to form a second pre-sinter assembly; and treating the second pre-sinter assembly in the presence of a catalyst/solvent material for diamond at a pressure of around 6 GPa or greater and a temperature at which the diamond material is more thermodynamically stable than graphite to sinter together the diamond grains to form the polycrystalline diamond construction comprising a body of polycrystalline diamond material bonded to a substrate along an interface surface; abd indicia on at least a portion of the interface surface, the indicia comprising any one or more of letters, numbers, graphical symbols and/or combinations thereof.

Viewed from a third aspect there is provided a method of using indicia on an interface surface between a body of superhard material and a substrate bonded thereto along said interface surface to distinguish between superhard constructions comprising: identifying a first super hard construction by examining the interface surface between the substrate and the body of super hard material bonded thereto; identifying a second super hard construction by examining the interface surface between the substrate and the body of super hard material bonded thereto; distinguishing the first super hard construction from the second super hard construction based on the indicia on the interface surface of the first and second super hard constructions.

Viewed from a fourth aspect there is provided a drill bit or a cutter or a component therefor comprising the superhard construction described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Various versions will now be described by way of example and with reference to the accompanying drawings in which:

FIG. 1 is a schematic diagram of an example superhard construction in the form of a cutting element having a body of super hard material such as PCD material attached to a substrate;

FIG. 2 is a top plan view of a substrate of the exemplary cutting element of Fig 1 ;

FIG. 3 is a flow diagram of an exemplary method of forming one or more exemplary cutting elements; and

FIG. 4 is a flow diagram of an exemplary method of identifying cutting elements according to at least one example for using indicia on an unexposed portion of the cutting element to distinguish cutting elements. DETAILED DESCRIPTION

As used herein, a “superhard material” is a material having a Vickers hardness of at least about 25 GPa. Diamond and cubic boron nitride (cBN) material are examples of superhard materials. Diamond is the hardest known material with cubic boron nitride (cBN) being considered to be second in this regard. Both materials are termed superhard materials. Hardness numbers are figures of merit, in that they are highly dependent upon the method employed to measure them. Using Knoop indenter hardness measurement techniques at 298° K, diamond has been measured to have a hardness of 9000 kg/mm ² and cBN 4500 kg/mm ² both with 500 g loading. PCD materials typically have a hardness falling in the range 4000 to 5000 kg/mm ² when measured using similar techniques with either Vickers or Knoop indenters. For the purposes discussed herein, materials with measured hardnesses greater than around 4000 kg/mm ² are considered to be super hard materials.

As used herein, a “catalyst material for diamond”, also referred to as “solvent I catalyst for diamond”, is a material that is capable of promoting the nucleation, growth or interbonding of diamond grains at a pressure and temperature at which diamond is thermodynamically stable. Catalyst materials for diamond may be metallic, such as cobalt, iron, nickel, manganese and alloys of these, or non-metallic.

As used herein, “polycrystalline diamond” (PCD) material comprises 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 exemplary PCD material, interstices between the diamond gains 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, interstices or interstitial regions may be substantially or partially filled with a material other than diamond, or they may be substantially empty. As used herein, a “filler” material is a material that wholly or partially fills pores, interstices or interstitial regions within a structure, such as a polycrystalline structure. Thermally stable examples of PCD material may comprise at least a region from which catalyst material has been removed from the interstices, leaving interstitial voids between the diamond grains. As used herein, a “thermally stable PCD” structure is a PCD structure at least a part of which exhibits no substantial structural degradation or deterioration of hardness or abrasion resistance after exposure to a temperature above about 400 degrees centigrade.

As used herein, a “superhard construction” means a construction comprising a body of polycrystalline superhard material. In such a construction, the substrate is bonded or otherwise attached thereto.

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.

As used herein, the term “integrally formed” regions or parts are produced contiguous with each other and are not separated by a different kind of material.

The following will provide, with reference to FIGS. 1 and 2, detailed descriptions of cutting elements having indicia on an unexposed surface such as the interface surface between the substrate and body of super hard material. It is noted, however, that the discussion of cutting elements that follows is also applicable to other super abrasive or PCD elements not configured as cutting elements. A description of a method for using such indicia to, for example, distinguish between cutting elements or inserts having substantially identical external geometric features is additionally provided in connection with FIG.4.

As shown in Figure 1 , a cutting element 1 includes a substrate 10 with a body of superhard material 12 formed on the substrate 10. The substrate 10 may be formed of a hard material such as cemented tungsten carbide. The superhard material 12 may be, for example, polycrystalline diamond (PCD), or a thermally stable product such as thermally stable PCD (TSP). The cutting element 1 may be mounted into a bit body such as a drag bit body (not shown) and may be suitable, for example, for use as a cutter insert for a drill bit for boring into the earth.

The exposed top surface of the superhard material 12 opposite the substrate forms the cutting face 14, which is the surface which, along with its edge 16, performs the cutting in use. At one end of the substrate 10 is an interface surface 18 that forms an interface with the superhard material layer 12 which is attached thereto at this interface surface. As shown in Figure 1 , the substrate 10 is generally cylindrical and has a peripheral surface 20.

FIG. 2 is a view from above of a substrate of the exemplary cutting element of Figure 1 , prior to sintering the grains or particles to form the body of superhard material 12 bonded to the substrate 10 along the interface surface 18. As shown in Figure 2, indicia 100 are generated on a surface of the substrate 10 which is to form the interface surface 18 along which the body of superhard material 12 is to be bonded. Additionally, the interface surface 18 is substantially non planar with a number of protrusions 102, 104 projecting therefrom to manage the residual stress distributions in the construction 1.

The view from above shown in Fig 2 may be obtained by generating an image showing the indicia 100 on the interface surface 18 visible through the body of super hard material bonded therealong using a conventional imaging technique such as acoustic scanning microscopy.

The term interface surface as used in connection with exemplary polycrystalline super hard constructions may be used to denote the interface surface between a body of polycrystalline super hard material and a substrate where the substrate comprises a first material and the body of polycrystalline super hard material comprises a second material, the first material differing from the second material in any one or more of average grain size of super hard material, coefficient of thermal expansion, super hard material grain size distribution, hardness.

The indicia 100 on at least a portion of the interface surface 18 may comprise any one or more of letters, numbers, graphical symbols and/or combinations thereof.

In some examples, the body of super hard material 12 comprises natural and/or synthetic diamond grains, and/or cubic boron nitride grains and in some examples the body of superhard material 12 comprises polycrystalline diamond (PCD) material having interbonded diamond grains and interstices therebetween.

In some examples, where the body of super hard material 12 comprises a body of PCD material, the construction 1 may be subjected to a processing treatment after sintering, such as acid leaching, to remove residual catalyst binder from at least a portion of the body of PCD material to render it substantially free of a catalyst material for diamond. The term substantially free may, in some examples, result in at least a portion of the body of superhard comprising at most 2 weight percent of catalyst material for diamond.

In some examples, the substrate 10 comprises tungsten carbide particles bonded together by a binder material such as one comprising any one or more of Co, Ni and Cr or an alloy thereof. The substrate 10 may comprise between around 8 to 13 weight or volume % binder material.

In some examples, such as that shown in FIG 2, the interface surface 18 is non-planar.

The indicia 100 may, in some examples, comprise at least one of an indicia that indicates a product name of the super hard construction; or an indicia that indicates a manufacturing batch indicator of the super hard construction.

As shown in the flow diagram of Figure 3, an example of a polycrystalline super hard construction such as a polycrystalline diamond (PCD) construction may be made by a method 900 including providing a cemented carbide substrate 902, contacting 904 an aggregated, substantially unbonded mass of diamond particles against the surface of the substrate into which the indicia have been generated, to form an pre-sinter assembly, encapsulating 906 the pre-sinter assembly in a capsule for an ultra-high pressure furnace and subjecting 908 the pre-sinter assembly to a pressure of at least about 5.5 GPa and a temperature of at least about 1 ,250 degrees centigrade, and sintering the diamond particles to form a polycrystalline super hard construction comprising a body of superhard material such as PCD integrally formed on and joined to the cemented carbide substrate along the interface surface. In some versions, 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 7.5 GPa.

The step 902 of providing a substrate includes, in some examples, milling a tungsten carbide powder with a binder material to form a milled powder, the binder material comprising any one or more of Co, Ni, and/or Cr, and/or a chromium carbide, compacting the milled powder to form a green body, sintering the green body in a vacuum or inert gas atmosphere to form a first pre-composite body and sintering the first pre-composite body to form a cemented carbide substrate. The indicia may then be generated on a surface of the cemented carbide substrate.

The method of forming an exemplary construction may then include placing the cemented carbide substrate into a canister and adding a mass of diamond grains or particles onto the surface of the cemented carbide substrate having the indicia thereon to form a second pre-sinter assembly; and treating the second pre-sinter assembly in the presence of a catalyst/solvent material for diamond at a pressure of around 6 GPa or greater and a temperature at which the diamond material is more thermodynamically stable than graphite to sinter together the diamond grains to form the polycrystalline diamond construction comprising a body of polycrystalline diamond material bonded to a substrate along an interface surface; and indicia on at least a portion of the interface surface, the indicia comprising any one or more of letters, numbers, graphical symbols and/or combinations thereof.

The indicia may be generated on a surface of the substrate by, for example, laser processing a surface of the substrate to generate the indicia on the surface which is to form the interface surface with the body of super hard material. Alternatively, conventional Electrical Discharge Machining (EDM) techniques may be used to generate the indicia on a surface of the substrate to generate the indicia on the surface which is to form the interface surface with the body of super hard material. In other examples, the indicia may be generated in situ during the sintering process for the substrate by placing a plug with the interface design including any desired indicia thereon to imprint the indicia into the green body which is then sintered to create the substrate.

As shown in Figure 4, an exemplary method 1000 of using indicia on an interface surface between a body of superhard material and a substrate bonded thereto along said interface surface to distinguish between superhard constructions may comprise, as indicated in step 1002, identifying a first super hard construction by examining the interface surface between the substrate and the body of super hard material bonded thereto and in step 1004 identifying a second super hard construction by examining the interface surface between the substrate and the body of super hard material bonded thereto. In step 1006, the method includes distinguishing the first super hard construction from the second super hard construction based on the indicia on the interface surface of the first and second super hard constructions.

In some examples, the step of examining the interface surface of the first and second constructions comprises using a conventional scanning acoustic microscopy technique to generate an image of the internal interface surfaces and indicia thereon.

The superhard constructions described herein may be used in tools for any one or more of cutting, milling, grinding, drilling, earth boring, rock drilling or other abrasive applications, including but not limited to a tools forming a drill bit for earth boring or rock drilling such as a rotary fixed-cutter bit for use in the oil and gas drilling industry. In other examples the tool may be a rolling cone drill bit, a hole opening tool, an expandable tool, a reamer or another earth boring tool. In some examples, the exemplary construction(s) may form cutting elements for a drill bit or a cutter or a component therefor.

As used herein, the phrase “indicia” may generally refer to any marking (graphical, textual, or otherwise) that conveys information. Examples may include, without limitation, text (such as a manufacturer name, a product name, a cutter type, manufacturing batch information or any other suitable text, graphics (such as company logos, product logos, and other graphics), and any other form of markings, including shapes (such as lines, dots, dashes, or the like) that convey information about or in connection with the construction.

The preceding description has been provided to enable others skilled the art to best utilize various aspects described by way of example herein. This description is not intended to be exhaustive or to be limited to any precise form disclosed. Many modifications and variations are possible. For example, whilst the examples have described forming the indicia on the interface surface of the substrate, in some examples such as where the construction is formed by bonding a pre-formed body of superhard material to a substrate, the indicia may formed instead on the interface surface of the body of super hard material in the same manner as described above for forming the indicia on the substrate.