TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY

[0001 ] The present invention relates generally to superabrasive materials and a method of making superabrasive materials, and more particularly, to polycrystalline diamond compacts (PDC).

SUMMARY

[0002] In one embodiment, a superabrasive compact may comprise a substrate; a diamond table attached to the substrate, wherein the diamond table has a first region and a second region, the second region is sandwiched between the first region and the substrate, wherein the diamond table includes bonded diamond grains defining interstitial channels, the interstitial channels are filled with at least two types of carbides in the first region, the interstitial channels in the second region are filled with a metal catalyst from the substrate.

[0003] In another embodiment, a method of making a superabrasive compact may comprise steps of providing an at least partially leached polycrystalline diamond table that comprises bonded diamond grains defining interstitial channels therein; providing a composite material positioned near a surface of the at least partially leached polycrystalline diamond table; providing a substrate near the at least partially leached polycrystalline diamond table such that the at least partially leached polycrystalline diamond table is sandwiched between the composite material and the substrate; and subjecting the substrate and the at least partially leached polycrystalline diamond table and the composite material to conditions of elevated temperature and pressure suitable for producing the polycrystalline superabrasive compact; wherein the composite material infiltrates into a first region of the at least partially leached polycrystalline diamond table and forms at least two carbides at a first temperature, wherein a catalyst from the substrate sweeps into a second region of the at least partially leached polycrystalline diamond table at a second

temperature.

[0004] In yet another embodiment, a superabrasive compact may comprise a substrate; a diamond table attached to the substrate, wherein the diamond table has a first region and a second region, the second region is sandwiched between the first region and the substrate, wherein the diamond table includes bonded diamond grains defining interstitial channels, the interstitial channels are filled with aluminum carbide and additives in the first region, the interstitial channels in the second region are filled with a metal catalyst from the substrate, wherein the first region occupies from about 20% up to about 95% volume of the at least partially leached

polycrystalline diamond table.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The foregoing summary, as well as the following detailed description of the embodiments, will be better understood when read in conjunction with the appended drawings. It should be understood that the embodiments depicted are not limited to the precise arrangements and instrumentalities shown.

[0006] FIG. 1 is schematic perspective view of a cylindrical shape thermally stable polycrystalline diamond compact produced in a high pressure high temperature (HPHT) process according to an embodiment;

[0007] FIG. 2 is an enlarged cross-sectional view of a part of diamond table on the thermally stable polycrystalline diamond compact as shown in FIG. 1 according to an embodiment; and

[0008] FIG. 3 is a flow chart illustrating a method of making reinforced thermally stable polycrystalline diamond compact.

DETAILED DESCRIPTION

[0009] Before the description of the embodiment, terminology, methodology, systems, and materials are described; it is to be understood that this disclosure is not limited to the particular terminologies, methodologies, systems, and materials described, as these may vary. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions of

embodiments only, and is not intended to limit the scope of embodiments. For example, as used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. In addition, the word "comprising" as used herein is intended to mean "including but not limited to." Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. [0010] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as size, weight, reaction conditions and so forth used in the specification and claims are to the understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are

approximations that may vary depending upon the desired properties sought to be obtained by the invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[001 1 ] As used herein, the term "about" means plus or minus 10% of the numerical value of the number with which it is being used. Therefore, about 50% means in the range of 45%-55%.

[0012] As used herein, the term "superabrasive particles" may refer to ultra-hard particles or superabrasive particles having a Knoop hardness of 3500 KHN or greater. The superabrasive particles may include diamond and cubic boron nitride, for example. The term "abrasive", as used herein, refers to any material used to wear away softer materials.

[0013] The term "particle" or "particles", as used herein, refers to a discrete body or bodies. A particle is also considered a crystal or a grain.

[0014] The term "superabrasive compact", as used herein, refers to a sintered product made using super abrasive particles, such as diamond feed or cubic boron nitride particles. The compact may include a support, such as a tungsten carbide support, or may not include a support. The "superabrasive compact" is a broad term, which may include cutting element, cutters, or polycrystalline cubic boron nitride insert.

[0015] The term "cutting element", as used herein, means and includes any element of an earth-boring tool that is used to cut or otherwise disintegrate formation material when the earth-boring tool is used to form or enlarge a bore in the formation.

[0016] The term "earth-boring tool", as used herein, means and includes any tool used to remove formation material and form a bore (e.g., a wellbore) through the formation by way of removing the formation material. Earth-boring tools include, for example, rotary drill bits (e.g., fixed-compact or "drag" bits and roller cone or "rock" bits), hybrid bits including both fixed compacts and roller elements, coring bits, percussion bits, bi-center bits, reamers (including expandable reamers and fixed- wing reamers), and other so-called "hole-opening" tools.

[0017] The term "feed" or "diamond feed", as used herein, refers to any type of diamond particles, or diamond powder, used as a starting material in further synthesis of PDC compacts.

[0018] The term "polycrystalline diamond", as used herein, refers to a plurality of randomly oriented or highly oriented monocrystalline diamond particles, which may represent a body or a particle consisting of a large number of smaller

monocrystalline diamond particles of any sizes. Polycrystalline diamond particles usually do not have cleavage planes.

[0019] The term "superabrasive", as used herein, refers to an abrasive possessing superior hardness and abrasion resistance. Diamond and cubic boron nitride are examples of superabrasives and have Knoop indentation hardness values of over 3500.

[0020] The terms "diamond particle" or "particles" or "diamond powder", which is a plurality of a large number of single crystal or polycrystalline diamond particles, are used synonymously in the instant application and have the same meaning as "particle" defined above.

[0021 ] Polycrystalline diamond compact (or "PDC", as used hereinafter) may represent a volume of crystalline diamond grains with embedded foreign material filling the inter-grain space. In one particular case, a compact comprises crystalline diamond grains, bound to each other by strong diamond-to-diamond bonds and forming a rigid polycrystalline diamond body, and the inter-grain regions, disposed between the bounded grains and filled in one part with a catalyst material (e.g. cobalt or its alloys), which was used to promote diamond bonding during fabrication, and in other part filled with other materials which may remain after the sintering of diamond compact. Suitable metal solvent catalysts may include the iron group transitional metal in Group VIII of the Periodic table.

[0022] "Thermally stable polycrystalline diamond" as used herein is understood to refer to intercrystalline bonded diamond that includes a volume or region that is or that has been rendered substantially free of the solvent metal catalyst used to form PDC, or the solvent metal catalyst used to form PDC remains in the region of the diamond body but is otherwise reacted or otherwise rendered ineffective in its ability adversely impact the bonded diamond at elevated temperatures as discussed above.

[0023] In another particular case, a polycrystalline diamond composite compact comprises a plurality of crystalline diamond grains, which are not bound to each other, but instead are bound together by foreign bonding materials such as borides, nitrides, carbides, and others, e.g. by silicon carbide bonded diamond material.

[0024] Polycrystalline diamond compacts (or PDC compacts) may be fabricated in different ways and the examples discussed herein do not limit a variety of different types of diamond composites and PDC compacts which may be produced according to an embodiment. In one particular example, polycrystalline compacts may be formed by placing a mixture of diamond powder with a suitable solvent catalyst material (e.g. cobalt powder) on the top of WC-Co substrate, the assembly is then subjected to conditions of HPHT process, where the solvent catalyst promotes desired inter-crystalline diamond-to-diamond bonding resulted in the formation of a rigid polycrystalline diamond body and, also, provides a binding between

polycrystalline diamond body and WC-Co substrate. [0025] In another particular example, a polycrystalline diamond compact is formed by placing diamond powder without a catalyst material on the top of substrate containing a catalyst material (e.g. WC-Co substrate). In this example, necessary cobalt catalyst material is supplied from the substrate and melted cobalt is swept through the diamond powder during the HPHT process. In still another example, a hard polycrystalline diamond composite compact is fabricated by forming a mixture of diamond powder with silicon powder and the mixture is subjected to HPHT process, thus forming a dense polycrystalline compact where diamond particles are bound together by newly formed silicon carbide material.

[0026] The presence of catalyst materials inside the polycrystalline diamond body promotes the degradation of the cutting edge of the compact during the cutting process, especially if the edge temperature reaches a high enough critical value. It is theorized that the cobalt driven degradation may be caused by the large difference in coefficient of thermal expansion between diamond and catalyst (e.g. cobalt metal), and also by the catalytic effect of cobalt on diamond graphitization. Removal of catalyst from the polycrystalline diamond body of PDC compact, for example, by chemical leaching in acids, leaves an interconnected network of pores and a residual catalyst (up to about 10 vol%) trapped inside the polycrystalline diamond body. It has been demonstrated that depletion of cobalt from the polycrystalline diamond body of the PDC compact significantly improves a compact's abrasion resistance. Thus, it is theorized that a thicker cobalt depleted layer near the cutting edge, such as more than about 100 μιη may provide better abrasion resistance of the PDC compact than a thinner cobalt depleted layer, such as less than about 100 μιη.

[0027] A superabrasive compact 10 in accordance with an embodiment is shown in FIG. 1 . Superabrasive compact 10 may be inserted into a downhole of a suitable tool, such as a drill bit, for example. One example of the superabrasive compact 10 may include a diamond table 12 having a top surface 21 .

[0028] In one embodiment, the superabrasive compact 10 may be a standalone compact without a substrate. In another embodiment, the superabrasive compact 10 may include a substrate 20 attached to the diamond table 12 formed by

polycrystalline diamond particles. The substrate 20 may be metal carbide, attached to the diamond table 12 via an interface 22 separating the diamond table 12 and the substrate 20. The interface 22 may have an uneven interface. Substrate 20 may be made from cemented cobalt tungsten carbide, while the diamond table 12 may be formed from a polycrystalline ultra-hard material, such as polycrystalline diamond or diamond crystals bonded by a foreign material.

[0029] Still in FIG. 1 , the diamond table 12 may include at least two layers with a first layer 26 and a second layer 24. The second layer 24 may be closer to the interface 22 and may be sandwiched between the substrate 20 and the first layer 26. The catalyst may include an iron group transitional metal, such as cobalt, nickel, or iron, for example.

[0030] The compact 10 may be referred to as a polycrystalline diamond compact ("PDC") when polycrystalline diamond is used to form the diamond table 12. PDC compacts are known for their toughness and durability, which allow them to be an effective cutter in demanding applications. Although one type of superabrasive compact 10 has been described, other types of superabrasive compacts 10 may be utilized. For example, in one embodiment, superabrasive compact 10 may have a chamfer (not shown) around an outer peripheral of the top surface 21 . The chamfer may have a vertical height of about 0.5 mm or 1 mm and an angle of about 45° degrees, for example, which may provide a particularly strong and fracture resistant tool component. The superabrasive compact 10 may be a subject of procedure depleting catalyst metal (e.g. cobalt) near the cutting surface of the compact, for example, by chemical leaching of cobalt in acidic solutions. The unleached superabrasive compact may be fabricated according to processes known to persons having ordinary skill in the art. Methods for making diamond compacts and composite compacts are more fully described in United States Patent Nos.

3,141 ,746; 3,745,623; 3,609,818; 3,850,591 ; 4,394,170; 4,403,015; 4,794,326; and 4,954,139. [0031 ] In certain applications, it may be desired to have a PDC body comprising a single PDC-containing volume or region, while in other applications, it may be desired that a PDC body be constructed having two or more different PDC- containing volume or regions. For example, it may be desired that the PDC body include a first PDC-containing region extending a distance D from the top surface or a working surface, as shown in FIG. 1 , and a second PDC-containing region extending from the first PDC-containing region to the substrate. The PDC-containing regions may be formed having different diamond densities and/or be formed from different diamond grain sizes, and/or be formed from leaching the PDC with acid solutions partially or fully. It is, therefore, understood that thermally stable polycrystalline diamond constructions of the invention may include one or multiple PDC regions within the PDC body as called for by a particular drilling or cutting application.

[0032] FIG. 2 illustrates the microstructure of the diamond table 12, and more specifically, a section of the thermally stable polycrystalline diamond 10. The diamond table 12 of the thermally stable region may have the first region 26 and the second region 24. The diamond table 12 may include bonded diamond grains 28 defining interstitial channels 42. A matrix of interstitial channels 42 between the bonded diamond grains may be filled with at least two types of carbides 48 with a first carbide comprising silicon carbide, a second carbide comprising aluminum carbide, for example, in the first region 26. Aluminum carbide may have high solubility in water and may be decomposed when aluminum carbide comes into contact with water or drilling mud. The first thermally stable region comprising the interstitial regions free of the catalyst material is shown to extend a distance "D" from a working or cutting surface 21 of the thermally stable polycrystalline diamond 10. In one embodiment, the distance "D" is identified and measured by cross sectioning a thermally stable diamond table construction and using a sufficient level of magnification to identify the interface between the first and second regions.

[0033] The so-formed thermally stable first region 26 may not be subject to the thermal degradation encountered in the remaining areas of the PDC diamond body, resulting in improved thermal characteristics. The remaining region of the interstitial channels 42 in the second region 24 may be filled with a metal catalyst 46. The first region may comprise an additive, such as an inert chemical. The inert chemical may include glass or quartz. Glass filler may be chosen because glass has a low softening and melting point such that it may become liquid at relative low

temperature, e.g., 600 °C. Quartz crystal may be chosen because quartz has the similar coefficient of thermal expansion (CTE) as diamond. The adding of quartz crystal may not cause thermal failure to the diamond table under high temperatures. The first region may occupy about 20% to up to about 95% volume of the diamond table 12. In one embodiment, the diamond table may be a cylindrical shape, therefore the height D of the first region may be from about 20% to up to about 95% the total height of the diamond table 12. If the diamond table is about 2 mm thick, for example, the first region may be from about 0.4 mm to up to about 1 .9 mm, for example.

[0034] In one embodiment, the first region 26 of the diamond table 12 may have about 87.5% aluminum and about 12.5% silicon. The aluminum carbide and silicon carbide may be formed from a eutectic material comprising about 87.5% aluminum and about 12.5% silicon eutectic composition.

[0035] The diamond table 12 may be partially leached according to known methods. The selected region of the PDC body may be rendered thermally stable by removing substantially all of the catalyst material therefrom by exposing the desired surface or surfaces to acid leaching, as disclosed for example in U.S. Pat. No.

4,224,380, which is incorporated herein by reference. Generally, after the PDC body or compact is made by HPHT process, the identified surface or surfaces, e.g., at least a portion of the working or cutting surfaces, are placed into contact with the acid leaching agent for a sufficient period of time to produce the desired leaching or catalyst material depletion depth.

[0036] Suitable leaching agents for treating the selected region to be rendered thermally stable include materials selected from the group consisting of inorganic acids, organic acids, mixtures and derivatives thereof. The particular leaching agent that is selected can depend on such factors as the type of catalyst material used, and the type of other non-diamond metallic materials that may be present in the PDC body, e.g., when the PDC body is formed using synthetic diamond powder. While removal of the catalyst material from the selected region operates to improve the thermal stability of the selected region, it is known that PDC bodies especially formed from synthetic diamond powder can include, in addition to the catalyst material, non-catalyst materials, such as other metallic elements that can also contribute to thermal instability.

[0037] As shown in FIG. 3, a method 30 of making a superabrasive compact may comprise steps of providing at least partially leached polycrystalline diamond table that comprises bonded diamond grains defining interstitial channels therein in a step 32; providing a composite material, such as a eutectic material, positioned near a surface of the at least partially leached polycrystalline diamond table in a step 34; providing a substrate, such as cemented tungsten carbide, near the at least partially leached polycrystalline diamond table such that the at least partially leached polycrystalline diamond table is sandwiched between the composite material and the substrate in a step 36; and subjecting the substrate and the at least partially leached polycrystalline diamond table and the composite material to conditions of elevated temperature and pressure suitable for producing the polycrystalline superabrasive compact in a step 38, wherein the composite material infiltrates into a first region of the at least partially leached polycrystalline diamond table and forms at least two carbides at a first temperature, wherein a catalyst from the substrate sweeps into a second region of the at least partially leached polycrystalline diamond table at a second temperature.

[0038] The method 30 may further include a step of bonding the substrate to the second region of the at least partially leached polycrystalline diamond table.

Providing at least partially leached polycrystalline diamond table that comprises bonded diamond grains defining interstitial channels therein in a step 32 may further include partially leaching the diamond table or fully leaching the diamond table after synthesizing the polycrystalline diamond compact. In one embodiment, the eutectic material may comprise about 87.5% aluminum and about 12.5% silicon eutectic composition. During a first temperature about 1000 °C, aluminum silicon eutectic may infiltrate into the interstitial channels of the diamond table from the top of the diamond table and move toward the cemented tungsten carbide substrate. By the time when the temperature reaches about 1500 °C, the catalyst, such as an iron group transitional metal, e.g., cobalt, from the cemented carbide substrate may sweep into the interstitial channels of the diamonds. The aluminum silicon eutectic may react with diamond to form aluminum carbide and silicon carbide at about first temperature. The aluminum silicon eutectic may keep moving toward cemented tungsten carbide up to the interface between the first region and the second region where cobalt sweeps through from commented tungsten carbide. The first region may occupy from about 20% to up to about 95% volume of the at least partially leached polycrystalline diamond table.

[0039] The composite material may be selected from a group consisting of as a powder, as a disk, as a ring, as a disk with perforated holes, as a triangle, as a rectangular. One or more steps may be inserted in between or substituted for each of the foregoing steps 32-38 without departing from the scope of this disclosure.

[0040] Example 1 :

[0041 ] PDC cutters were produced by the methods described in the prior art, composed of a starting diamond powder with an average grain size of 12 microns in diameter, or with an average grain size of 24 microns in diameter and a metal carbide, such as tungsten carbide, attached to the polycrystalline diamond via an interface between the polycrystalline diamond and tungsten carbide. The cutter was ground and finished to 16mm in diameter, and 13mm in height. A 45 degree bevel was placed on the edge of the diamond, with a thickness of about 0.4mm. Some cutters were fully leached by removing the catalyst from the diamond table.

[0042] The Ta cup was loaded by pushing a WC substrate (OD 0.648") inside and the cup was laid upward. Subsequently, a fully leached porous diamond table (0.648") was loaded on top of the WC substrate. A piece of thin Al-Si eutectic disc (0.002" thick) with a dimension of 0.650" was disposed on top of the diamond table evenly. Then, a Ta disc (0.005" thick and 0.650" OD) was used to cover Al-Si eutectic disc followed by a mica disc and a graphite pill (0.1 " thick). Half of the graphite pill protruded out of the Ta cup. The assembled Ta cup with a graphite sleeve and some graphite pills were encapsulated. The Ta cup was fit inside the graphite sleeve tightly. The encapsulated cup was transferred into cell loading area, and the entire body was loaded into the cell specifically designed for belt pressing. The cell was loaded inside the die and was applied high pressure and high temperature (HPHT) cycle to the cell for 30 minutes. The soak pressure was maintained around 6.0GPa and the soak temperature was about 1550 °C. The soak time for bonding of the thermally stable disc to the carbide was about 15 minutes. After the bonding cycle, the cup was taken out of the pressed cell for further finishing.

[0043] While reference has been made to specific embodiments, it is apparent that other embodiments and variations can be devised by others skilled in the art without departing from their spirit and scope. The appended claims are intended to be construed to include all such embodiments and equivalent variations.