Selectively leached thermally stable cutting element in earth-boring tools, earth-boring tools having selectively leached cutting elements, and related methods

A cutting element comprises a supporting substrate, and a cutting table attached to an end of the supporting substrate. The cutting table comprises a first region and a second region. The first region comprising inter-bonded diamond particles and is substantially free of at least highly catalytic metallic compounds, one or more non-catalytic compounds within interstitial spaces between the inter-bonded diamond particles, and voids within interstitial spaces between the inter-bonded diamond particles. The second region comprising inter-bonded diamond particles, one or more non-catalytic compounds within interstitial spaces between the inter-bonded diamond particles, and one or more metallic phases within interstitial spaces between the inter-bonded diamond particles. The first region of the cutting table has a content of elemental metal of at least about 2.6 wt %. A method of forming a cutting element, and an earth-boring tool are also described.

TECHNICAL FIELD

Embodiments of the disclosure relate to cutting elements, earth-boring tools, and methods of forming the cutting elements.

BACKGROUND

Earth-boring tools for forming wellbores in subterranean earth formations may include a plurality of cutting elements secured to a body. For example, fixed-cutter earth-boring rotary drill bits (e.g., drag bits) include a number of cutting elements fixedly attached to a bit body of a drill bit and configured for removing formation material with a shearing action that are. Similarly, roller cone earth-boring rotary drill bits may include member (e.g., cones) that are mounted on bearing pins extending from legs of a bit body such that each cone is rotatable about the bearing pin on which it is mounted. Cutting elements in the form of so-called “inserts” configured for a crushing and gouging action to remove subterranean formation material may be mounted to each cone of the drill bit. Other earth-boring tools utilizing one or more types of cutting elements include, for example, core bits, bi-center bits, eccentric bits, hybrid bits (e.g., rolling components in combination with fixed cutting elements), reamers, and casing milling tools.

The cutting elements used in such earth-boring tools often include a volume of superabrasive material, typically in the form of polycrystalline diamond (“PCD”) material mounted on and bonded to a supporting substrate. Surfaces of the polycrystalline diamond act as cutting faces of the so-called polycrystalline diamond compact (“PDC”) cutting elements. PCD material is material that includes inter-bonded grains or crystals of diamond material. In other words, PCD material includes direct, inter-granular bonds between the grains or crystals of diamond material. The terms “grain” and “crystal” are used synonymously and interchangeably herein.

PDC cutting elements are conventionally formed by sintering and bonding together relatively small diamond (synthetic, natural or a combination) grains, termed “grit,” under conditions of high temperature and high pressure in the presence of a Group VIII metal catalyst (e.g., cobalt, iron, nickel, or alloys and mixtures thereof) to form one or more layers (e.g., a “compact” or “table”) of PCD material. These processes are often referred to as high temperature/high pressure (or “HTHP”) processes. The supporting substrate may comprise a cermet material (e.g., a ceramic-metal composite material) such as, for example, cobalt-cemented tungsten carbide. In some instances, the PCD material may be formed on the cutting element, for example, during the HTHP process. In such instances, catalyst material (e.g., cobalt) in the supporting substrate may be “swept” into the diamond grains during sintering and serve as a catalyst material for forming the diamond table from the diamond grains. Powdered catalyst material may also be mixed with the diamond grains prior to sintering the grains together in an HTHP process. In other methods, the diamond table may be formed separately from the supporting substrate and subsequently attached thereto, for example by brazing.

Upon formation of a diamond table using a conventional HTHP process and conventional catalyst materials, catalyst material may remain in interstitial spaces between the grains or crystals of diamond in the resulting polycrystalline diamond table. The presence of the catalyst material in the diamond table may contribute to thermal damage in the diamond table when the cutting element is heated during use due to friction at the contact point between the cutting element and the formation. Polycrystalline diamond cutting elements in which the catalyst material remains in the diamond table are generally thermally stable up to a temperature of about seven hundred fifty degrees Celsius (750° C.), although internal stress within the polycrystalline diamond table may begin to develop at temperatures exceeding about three hundred fifty degrees Celsius (350° C.). This internal stress is at least partially due to differences in the rates of thermal expansion between the diamond table and the cutting element substrate to which it is bonded. This differential in thermal expansion rates may result in relatively large compressive and tensile stresses at the interface between the diamond table and the substrate, and may cause the diamond table to delaminate from the substrate. At temperatures of about seven hundred fifty degrees Celsius (750° C.) and above, stresses within the diamond table may increase significantly due to differences in the coefficients of thermal expansion of the diamond material and the catalyst material within the diamond table itself. For example, cobalt thermally expands significantly faster than diamond, which may cause cracks to form and propagate within the diamond table, eventually leading to deterioration of the diamond table and ineffectiveness of the cutting element.

Furthermore, at temperatures at or above about seven hundred fifty degrees Celsius (750° C.), some of the diamond crystals within the diamond table may react with the catalyst material causing the diamond crystals to undergo a chemical breakdown or conversion to another allotrope of carbon. For example, the diamond crystals may graphitize in a reaction termed “back graphitization” at the diamond crystal boundaries, which may substantially weaken the diamond table. Also, at extremely high temperatures, in addition to graphite, some of the diamond crystals may be converted to carbon monoxide and carbon dioxide.

To reduce the problems associated with different rates of thermal expansion in polycrystalline diamond cutting elements, leaching processes are utilized to remove the catalyst material (e.g., cobalt) out from interstitial spaces between the diamond grains in the diamond table using, for example, an acid or combination of acids formulated specifically to remove certain phases of catalyst material from the diamond table. Nearly or substantially all of the catalyst material may be removed from the diamond table, or catalyst may be removed from only a portion of the diamond table. Thermally stable polycrystalline diamond tables in which substantially all catalyst material has been leached from the diamond table have been reported to be thermally stable up to temperatures of about one thousand two hundred degrees Celsius (1,200° C.). It has also been reported, however, that such fully leached diamond tables are relatively more brittle and vulnerable to shear, compressive, and tensile stresses than are non-leached, or partially leached, diamond tables. Therefore, selectively removing catalyst material from only a portion of the diamond table may have many advantages. For example, it is known to leach catalyst material from the cutting face, from the side of the diamond table (e.g., an “annulus leach”), or both, to a desired depth within the diamond table. Conventional leached diamond tables are known to contain between 1.5 wt %-2.5 wt % catalyst metal remaining in the leached portion of the diamond table subsequent to leaching.

BRIEF SUMMARY

Embodiments described herein include cutting elements, and related earth-boring tools, structures, supporting substrates, and methods of forming the cutting elements, structures, and supporting substrates. For example, in accordance with one embodiment described herein, a cutting element comprises a supporting substrate, and a cutting table attached to an end of the supporting substrate. The cutting table comprises a first region and a second region. The first region comprises inter-bonded diamond particles and is substantially free of at least highly catalytic metallic phases between the inter-bonded diamond particles, one or more non-catalytic compounds within interstitial spaces between the inter-bonded diamond particles, and voids within interstitial spaces between the inter-bonded diamond particles. The second region comprises inter-bonded diamond particles, the one or more non-catalytic compounds within interstitial spaces between the inter-bonded diamond particles, and one or more metallic phases within interstitial spaces between the inter-bonded diamond particles. The first region of the cutting table further comprises a content of elemental metal of at least about 2.6 wt %.

In additional embodiments, a method of forming a cutting element comprises providing a diamond-containing material over a substrate. Sintering the diamond-containing material in the presence of a homogenized binder to form a cutting table. During the sintering, converting portions of the homogenized binder within interstitial spaces between the inter-bonded diamond particles into one or more non-catalytic compounds and one or more metallic phases. Substantially removing an amount of at least highly catalytic metal phases of the one or more metallic phases from the cutting table to the a selected depth to form a first region of the cutting table comprising substantially only inter-bonded diamond particles, non-catalytic compounds and voids.

DETAILED DESCRIPTION

In an effort to provide cutting elements having diamond tables that are more thermally stable relative to cutting elements containing conventionally formed and partially leached diamond tables, cutting elements have been developed by the inventors herein that include an already thermally stable polycrystalline diamond table in which certain catalyst material phases have been selectively leached from a portion of the diamond table. The selectively leached diamond table may have greater amounts of metal remaining in the leached portion subsequent to leaching, which may result in cutting elements with not only enhanced thermal stability but also superior mechanical performance. The following description provides specific details, such as specific shapes, specific sizes, specific material compositions, and specific processing conditions, in order to provide a thorough description of embodiments of the present disclosure. However, a person of ordinary skill in the art would understand that the embodiments of the disclosure may be practiced without necessarily employing these specific details. Embodiments of the disclosure may be practiced in conjunction with conventional fabrication techniques employed in the industry. In addition, the description provided below does not form a complete process flow for manufacturing a cutting element or earth-boring tool. Only those process acts and structures necessary to understand the embodiments of the disclosure are described in detail below. Additional acts to form a complete cutting element or a complete earth-boring tool from the structures described herein may be performed by conventional fabrication processes.

As used herein, the terms “comprising,” “including,” “having,” and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method steps, but also include the more restrictive terms “consisting of” and “consisting essentially of” and grammatical equivalents thereof. As used herein, the term “may” with respect to a material, structure, feature, or method act indicates that such is contemplated for use in implementation of an embodiment of the disclosure and such term is used in preference to the more restrictive term “is” so as to avoid any implication that other, compatible materials, structures, features, and methods usable in combination therewith should or must be excluded.

As used herein, the terms “longitudinal,” “vertical,” “lateral,” and “horizontal” and are in reference to a major plane of a substrate (e.g., base material, base structure, base construction, etc.) in or on which one or more structures and/or features are formed and are not necessarily defined by earth's gravitational field. A “lateral” or “horizontal” direction is a direction that is substantially parallel to the major plane of the substrate, while a “longitudinal” or “vertical” direction is a direction that is substantially perpendicular to the major plane of the substrate. The major plane of the substrate is defined by a surface of the substrate having a relatively large area compared to other surfaces of the substrate.

As used herein, spatially relative terms, such as “below,” “lower,” “bottom,” “above,” “over,” “upper,” “top,” and the like, may be used for ease of description to describe one element's or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Unless otherwise specified, the spatially relative terms are intended to encompass different orientations of the materials in addition to the orientation depicted in the figures. For example, if materials in the figures are inverted, elements described as “over” or “above” or “on” or “on top of” other elements or features would then be oriented “below” or “beneath” or “under” or “on bottom of” the other elements or features. Thus, the term “over” can encompass both an orientation of above and below, depending on the context in which the term is used, which will be evident to one of ordinary skill in the art. The materials may be otherwise oriented (e.g., rotated 90 degrees, inverted, flipped) and the spatially relative descriptors used herein interpreted accordingly.

As used herein, the terms “earth-boring tool” and “earth-boring drill bit” each mean and include any type of bit or tool used for drilling during the formation or enlargement of a wellbore in a subterranean formation and include, for example, fixed-cutter bits, roller cone bits, percussion bits, core bits, eccentric bits, bi-center bits, reamers, mills, drag bits, hybrid bits (e.g., rolling components in combination with fixed cutting elements), and other drilling bits and tools known in the art.

As used herein, the term “cutting elements” means and includes, for example, superabrasive (e.g., polycrystalline diamond compact or “PDC”) cutting elements employed as fixed cutting elements, as well as superabrasive inserts comprising a PDC layer over a supporting substrate mounted to a body of an earth-boring tool.

As used herein, the term “inter-granular bond” means and includes any direct atomic bond (e.g., covalent, ionic, etc.) between atoms in adjacent particles of hard material.

As used herein, the term “void” means and includes a space in a polycrystalline material that remains unoccupied and is essentially free of any material.

A cutting element (e.g., a polycrystalline diamond compact cutting element) including a selectively leached region of the diamond table is disclosed. The cutting element is produced by forming a thermally stable cutting element with metallic phases and non-catalytic compounds within interstitial spaces between inter-bonded diamond particles, a portion of the thermally stable cutting element subjected to a process, for example leaching, to remove at least some metallic phases, for example highly catalytic metallic phases. A leach depth may be measured from a cutting face of a cutting table of the cutting element, a side of the cutting table, or both, and selected to further enhance at least one of thermal stability and toughness (e.g., impact resistance) of the cutting table. The cutting element including a selectively leached region may exhibit both improved thermal and mechanical performance compared to a conventional cutting element.

To form a selectively leached thermally stable cutting element according to the disclosure, a thermally stable cutting element may be formed initially in accordance with U.S. Application Ser. No. 15/993,362, and titled “Cutting Elements and Earth-Boring Tools, Supporting Substrates, and Methods,” the contents of which are hereby incorporated herein by this reference and a portion of which is represented inFIGS.1and2of the present disclosure.

The cutting element100ofFIG.1includes a supporting substrate104, and a cutting table102bonded to the supporting substrate104at an interface106. The cutting table102may be disposed directly on the supporting substrate104. The cutting table102may exhibit at least one lateral side surface112(also referred to as the “barrel” of the cutting table102), a cutting face110(also referred to as the “top” of the cutting table102) opposite the interface106, and at least one cutting edge116at a periphery (e.g., outermost boundary) of the cutting face110. As shown, cutting edge116may be chamfered to mitigate any tendency toward chipping before the cutting element100becomes minimally worn.

FIG.2shows a simplified cross-sectional view of a container200in a method for forming a thermally stable cutting element100as shown inFIG.1. A particulate, diamond-containing material201may be provided within the container200, and a supporting substrate204may be provided directly on the diamond-containing material201. The container200may substantially surround and hold the diamond-containing material201and the supporting substrate204. As shown inFIG.2, the container200may include an inner cup208in which the diamond-containing material201and a portion of the supporting substrate204may be disposed, a bottom end piece206in which the inner cup208may be at least partially disposed, and a top end piece210surrounding the supporting substrate204and coupled (e.g., swage bonded) to one or more of the inner cup208and the bottom end piece206. In additional embodiments, the bottom end piece206may be omitted (e.g., absent).

The diamond-containing material201and the supporting substrate204may be subjected to HTHP processing to form the cutting table102. The cutting table102may be formed by sintering the diamond-containing material201with a homogenized binder present in supporting substrate204and converting portions of the binder into non-catalytic compounds and metallic phases between diamond particles of the inter-bonded diamond particles.

The diamond-containing material201(e.g., diamond powder) may be formed of and include discrete diamond particles (e.g., discrete natural diamond particles, discrete synthetic diamond particles, combinations thereof, etc.). The discrete diamond particles may individually exhibit a desired particle size. The discrete diamond particles may comprise, for example, one or more of micro-sized diamond particles and nano-sized diamond particles. In addition, each of the discrete diamond particles may individually exhibit a desired shape, such as at least one of a spherical shape, a hexahedral shape, an ellipsoidal shape, a cylindrical shape, a conical shape, or an irregular shape. Each of the discrete diamond particles of the diamond-containing material201exhibits a substantially spherical shape. The discrete diamond particles may be monodisperse, wherein each of the discrete diamond particles exhibits substantially the same material composition, size, and shape, or may be polydisperse, wherein at least one of the discrete diamond particles exhibits one or more of a different material composition, a different particle size, and a different shape than at least one other of the discrete diamond particles. The diamond-containing material201may be formed by conventional processes, which are not described herein.

In some embodiments, the diamond-containing material201may be formed of and include diamond-containing agglomerates as described in U.S. Patent Publication No. US2021/0245244A1 (to Robertson), the contents of which are hereby incorporated herein by this reference. Precursor diamond-containing agglomerates may include discrete diamond particles intermixed with a binder material and/or a wax material (e.g., paraffin wax or polyethylene glycol (PEG)). The precursor diamond-containing agglomerates may be sintered while exposing the precursor diamond-containing agglomerates to a quantity of catalyst material to form diamond-containing agglomerates. The diamond-containing agglomerates may include discrete quantities of polycrystalline and/or superabrasive material while inhibiting formation of inter-granular bonds among the agglomerates themselves. In some embodiments, the diamond-containing agglomerates may contain include catalytic, non-advantageous metallic compounds or metallic phases (e.g., catalytic cobalt, catalytic iron, catalytic nickel). For example, the non-advantageous metallic compounds or metallic phases may not be leached from the diamond-containing agglomerates (e.g., “non-leached” diamond-containing agglomerates). In additional embodiments, the diamond-containing agglomerates may be at least substantially free of the non-advantageous metallic compounds or metallic phases. For example, the non-advantageous metallic compounds or metallic phases may be leached from the diamond-containing agglomerates (e.g., “leached” diamond-containing agglomerates).

The supporting substrate204may include a consolidated structure including tungsten carbide (WC) particles dispersed within a homogenized binder (e.g., a substantially homogeneous alloy, such as a substantially homogeneous peritectic alloy) including at least one first element selected from Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, Re, Os, Ir, Pt, Au, Hg, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ac, Th, Pa, and U and at least one second element selected from Al, Ga, Sn, Be, Bi, Te, Sb, Se, As, Ge, Si, B, and P; C; and W. The homogenized binder may, for example, include from about 35 weight percent (wt %) to about 95 wt % of the first element; from about 2.0 wt % to about 60 wt % of the second element; from about 0.1 wt % C to about 10 wt % C; and a remainder of W. The supporting substrate204may include from about 80 wt % to about 95 wt % of the WC particles, and from about 5 wt % to about 20 wt % of the homogenized binder. As noted above, homogenized binder of the supporting substrate204may be employed to convert the discrete diamond particles and/or the diamond-containing agglomerates of the diamond-containing material201into inter-bonded diamond particles.

Each of the discrete WC particles may individually exhibit a desired particle size, such as a particle size less than or equal to about 1000 μm. The discrete WC particles may include, for example, one or more of discrete micro-sized WC particles and discrete nano-sized WC particles. In addition, each of the discrete WC particles may individually exhibit a desired shape, such as one or more of a spherical shape, a hexahedral shape, an ellipsoidal shape, a cylindrical shape, a conical shape, or an irregular shape.

The discrete WC particles of the WC powder may be monodisperse, wherein each of the discrete WC particles exhibits substantially the same size and shape, or may be polydisperse, wherein at least one of the discrete WC particles exhibits one or more of a different particle size and a different shape than at least one other of the discrete WC particles. The WC powder has a multi-modal (e.g., bi-modal, tri-modal, etc.) particle size distribution. For example, the WC powder may include a combination of relatively larger, discrete WC particles and relatively smaller, discrete WC particles. The WC powder has a mono-modal particle size distribution. For example, all of the discrete WC particles of the WC powder may exhibit substantially the same particle size. The discrete WC particles may be formed by conventional processes, which are not described herein.

The HTHP processing may include subjecting the diamond-containing material201and the supporting substrate204including WC particles dispersed within the homogenized binder to elevated temperatures and elevated pressures in a directly pressurized and/or indirectly heated cell for a sufficient time to convert the discrete diamond particles and/or the diamond-containing agglomerates of the diamond-containing material201into inter-bonded diamond particles. The temperatures (e.g., sintering temperature(s)) employed within the heated, pressurized cell may be greater than the solidus temperature (e.g., greater than the solidus temperature and less than or equal to the liquidus temperature, greater than or equal to the liquidus temperature, etc.) of the homogenized binder of the supporting substrate204, and pressures within the heated, pressurized cell may be greater than or equal to about 2.0 GPa (e.g., greater than or equal to about 3.0 GPa, such as greater than or equal to about 4.0 GPa, greater than or equal to about 5.0 GPa, greater than or equal to about 6.0 GPa, greater than or equal to about 7.0 GPa, greater than or equal to about 8.0 GPa, or greater than or equal to about 9.0 GPa). The temperature(s) employed during the HTHP processing to form the cutting table102at least partially depend on the pressure(s) employed during the HTHP processing, and on the material composition of the homogenized binder of the supporting substrate204. The diamond-containing material201and the supporting substrate204may be held at selected temperatures and pressures within the heated, pressurized cell for a sufficient amount of time to facilitate the inter-bonding of the discrete diamond particles and/or the diamond agglomerates of the diamond-containing material201, such as a period of time between about 30 seconds and about 20 minutes.

During the HTHP processing, the homogenized binder of the supporting substrate204melts and a portion thereof is swept (e.g., mass transported, diffused) into the diamond-containing material201(FIG.2). The homogenized binder received by the diamond-containing material201catalyzes the formation of inter-granular bonds between the discrete diamond particles and/or the diamond agglomerates of the diamond-containing material201to form inter-bonded diamond particles, the non-catalytic compounds (e.g., perovskite compounds) within interstitial spaces between the inter-bonded diamond particles, and residual Group VIII catalyst materials including highly catalytic metal phases (e.g., catalytic cobalt, catalytic iron, catalytic nickel) within interstitial spaces between the inter-bonded diamond particles. The inter-bonded diamond particles may have a multi-modal particle size distribution. For example, the cutting table102may include relatively larger diamond particles (e.g., larger diamond particles) and relatively smaller diamond particles (e.g., smaller diamond particles). The inter-bonded diamond particles may have a mono-modal particle size distribution (e.g., the smaller diamond particles may be omitted, or the larger diamond particles may be omitted). The cutting table may include direct inter-granular bonds between the larger diamond particles and the smaller diamond particles. The larger diamond particles may be monodisperse, wherein all the larger diamond particles exhibit substantially the same size, or may be polydisperse, wherein the larger diamond particles exhibit a range of sizes and are averaged. In addition, the smaller diamond particles may be monodisperse, wherein all the smaller diamond particles exhibit substantially the same size, or may be polydisperse, wherein the smaller diamond particles exhibit a range of sizes and are averaged.

Following formation of the cutting element, such as the thermally stable cutting element100ofFIG.1, the cutting element may be subjected to selective removal (e.g. selective leaching) of catalytic, non-advantageous metallic compounds or metallic phases. For example, a leaching agent may be introduced to the cutting table102ofFIG.1, the formulation of the leaching agent may be tailored to remove the metallic phases, while non-catalytic compounds may remain within interstitial spaces between inter-bonded diamond particles. As non-limiting examples, non-catalytic compounds may comprise copper and/or lead.

A highly oxidizing leaching agent may be utilized to at least substantially remove metallic phases from the cutting table. Specifically, aqua regia (a mixture of concentrated nitric acid (HNO3) and concentrated hydrochloric acid (HCl)) may be used as a leaching agent. For example, the leaching agent composition may comprise various volumetric ratios of HCL and HNO3. As non-limiting examples, the leaching agent composition may include volumetric ratios ranging from 1 part by volume HCl, and 3 parts by volume HNO3, to 3 parts by volume HCl, and 1 part by volume HNO3. In addition to HNO3and HCl, the leaching agent may include compositions (e.g., mixtures) of sulfuric acid (H2SO4), hydrogen peroxide (H2O2), and/or perchlorate (HClO4) may also be used. For example, the leaching agent composition may comprise various volumetric ratios of H2SO4and H2O2. As non-limiting examples, the leaching agent composition may include volumetric ratios ranging from 3 parts by volume H2SO4, and 1 part by volume H2O2, to 7 parts by volume H2SO4, and 1 part by volume H2O2. The acids (e.g., HCl and HNO3) may be reagent grade in purity and concentration. Additionally, the temperature of the leaching agent composition may be from about 150° F. to about 200° F. (e.g., about 180° F.). By adjusting one or more of the temperature, leach chemistries, or process time, the catalytic, non-advantageous metallic phases may be targeted and removed (e.g. leached) from the cutting table. As non-limiting examples, the leaching process may occur at temperatures of from about 60° C. to about 80° C. Additionally, the duration of the leaching process may be from about 168 hours to about 1008 hours (e.g., about 1 to about 6 weeks), which may at least partially depend on the temperature during the leaching process. In some embodiments, a current may be applied to the leaching agent to provide an “electrolytic boost” and facilitate the leaching process.

Referring collectively toFIGS.3A and3B, a depth of penetration of the leaching agent (e.g., leach depth) may be selected to control one or more physical properties, such as, but not limited to, thermal stability and toughness. The selective leaching of cutting element100(FIG.1) is used to form embodiments of a cutting element300,300′ including a first region308and a second region310of the cutting table302. The leach depth corresponds to a first region308of a cutting table302shown inFIGS.3A and3B. The cutting element300,300′ includes a supporting substrate104, and a cutting table302bonded to the supporting substrate104at an interface106. The cutting table302may exhibit at least one lateral side surface112(also referred to as the “barrel” of the cutting table302), a cutting face114(also referred to as the “top” of the cutting table302) opposite the interface106, and cutting edge316at a periphery (e.g., outermost boundary) of the cutting face314. The interface106located between the supporting substrate104and the cutting table302. The first region308of the cutting table302includes the cutting face314and the cutting edge316. The second region310of the cutting table302opposite the supporting substrate104between the interface106and the first region308.

The cutting table302and the supporting substrate104may each individually exhibit a generally cylindrical column shape, and the interface106between the supporting substrate104and cutting table302may be substantially planar, although use of a non-planar interface is also contemplated. A height (e.g., thickness) of the cutting table302may be within a range of from about 0.3 millimeters (mm) to about 5 mm.

Referring now to the embodiment of the cutting element300ofFIG.3A, the first region308of the cutting table302is formed by selectively removing (e.g. leaching) metallic phases424from a region of cutting table102starting at the cutting face110to the pre-determined leach depth in the direction of the interface106. The leach depth corresponds to the thickness of the first region308. The thickness of the first region308of the cutting table302is measured from the cutting face314to a boundary with the second region310of the cutting table302. The leach depth (e.g., the thickness of the first region308) may extend from the cutting face314toward the supporting substrate104and may be within from about 750 μm to about 1000 μm of the interface106between the supporting substrate104and the cutting table302. In some embodiments, the thickness of the first region308(e.g., the leach depth) may be from about 10 μm to about 1500 μm (about 1.5 mm), from about 20 μm to about 1200 μm (about 1.2 mm), from about 30 μm to about 1000 μm (about 1 mm), from about 40 μm to about 500 μm, from about 50 μm to about 250 μm, such as from about 50 μm to about 100 μm, or from about 100 μm to about 250 μm. In additional embodiments, the thickness of the first region308(e.g., the leach depth) may be from about 50 μm to about 1500 μm.

Referring now to the embodiment of the cutting element300′ ofFIG.3B, the side surface112of cutting table302may also undergo leaching. For example, the cutting table302may include a leached portion318extending around the cutting edge316of the cutting face314and toward the supporting substrate104through a portion of the volume of the cutting table302proximate the side surface112of the cutting table302. Such a portion may be referred to as a “barrel leach” or “annulus leach.” Accordingly, the first region308of the cutting table102may include a first leach depth within an interior (e.g., central) portion320of the first region308, and a second leach depth within an exterior (e.g., annular) portion318of the first region308. The leach depth from the side surface112(e.g., the “barrel leach”) may extend toward the supporting substrate104and may be within from about 750 μm to about 1000 μm of the interface106between the supporting substrate104and the cutting table302. Thus, the “barrel leach” depth may vary with the thickness of the cutting table102. For example, the “barrel leach” may include a leach depth from the side surface112from about 10 μm to about 4000 μm (about 4 mm), from about 20 μm to about 2000 μm (about 2 mm), from about 30 μm to about 1000 μm (about 1 mm), from about 40 μm to about 500 μm, from about 50 μm to about 250 μm, such as from about 50 μm to about 100 μm, or from about 100 μm to about 250 μm. In some embodiments, the “barrel leach” depth may be from about 1000 μm (about 1 mm) to about 4000 μm (about 4 mm).

Referring again collectively toFIGS.3A and3B, the cutting element300,300′ may exhibit improved thermal and mechanical performance in comparison to non-leached thermally stable cutting elements100and are substantially superior to partially leached conventional cutting elements. The content of metal elements of the first region308of the cutting table302after leaching may be within the range of from about 2.6 wt % (weight percent) to about 6 wt %, such as from about 2.6 wt % to about 3 wt %, or from about 3 wt % to about 6 wt %, greater than the elemental metal content of the leached region of a conventional leached cutting element.

FIG.4Ais a simplified cross-sectional view showing how a microstructure of the first region308of cutting table302shown inFIG.3may appear under magnification.FIG.4Bis a simplified cross-sectional view showing how a microstructure of the second region310of cutting table302shown inFIG.3may appear under magnification. Referring toFIGS.4A and4Btogether, the first region308and second region310of the cutting table302includes interspersed and inter-bonded diamond particles414(e.g., inter-bonded diamond particles) that form a three-dimensional (3D) network of polycrystalline diamond (PCD) material. The inter-bonded diamond particles414may have a multi-modal particle size distribution. For example, as depicted inFIGS.4A and4B, the first region308and the second region310of the cutting table302may include relatively larger diamond particles414A (e.g., larger diamond particles) and relatively smaller diamond particles414B (e.g., smaller diamond particles). In additional embodiments, the inter-bonded diamond particles414may have a mono-modal particle size distribution (e.g., the smaller diamond particles414B may be omitted, or the larger diamond particles414A may be omitted). Direct inter-granular bonds between the larger diamond particles414A and the smaller diamond particles414B are represented inFIGS.4A and4Bby dashed lines416. The larger diamond particles414A may be monodisperse, wherein all the larger diamond particles414A exhibit substantially the same size, or may be polydisperse, wherein the larger diamond particles414A exhibit a range of sizes and are averaged. In addition, the smaller diamond particles414B may be monodisperse, wherein all the smaller diamond particles414B exhibit substantially the same size, or may be polydisperse, wherein the smaller diamond particles414B exhibit a range of sizes and are averaged.

As shown inFIG.4A, interstitial spaces are present between the inter-bonded diamond particles414of the first region308of the cutting table302. Voids426are present in the first region308of the cutting table302in locations where the metallic phases424, shown inFIG.4B, previously occupied. The interstitial spaces of the cutting table302are at least partially (e.g., substantially) filled with a non-catalytic compound422and voids426. The first region308is substantially free of at least highly catalytic metallic phases424. For example, 0.5 wt % or less of the highly catalytic metallic phases may remain in the first region308. The second region310of the cutting table302has not been subjected to the selective removal of the metallic phases424from cutting table302, leaving the second region310containing metallic phases424as shown inFIG.4Band substantially free of voids426. As shown inFIG.4B, the interstitial spaces are at least partially (e.g., substantially) filled with non-catalytic compounds422and metallic phases424. The non-catalytic compounds422of the second region310of the cutting table302may be a perovskite compound having the same general chemical formula shown above with reference to the non-catalytic compound422of the first region308of the cutting table302.

The presence of the non-catalytic compound422in combination with the absence of at least the highly catalytic metallic phases424in the first region308may render the first region308of the cutting table302more thermally stable than thermally stable cutting element100ofFIG.1before leaching due to the absence of at least highly catalytic metallic phases424in the first region308of the cutting table as well as more thermally stable than conventional partially leached cutting tables. For example, the non-catalytic compounds422may not significantly promote carbon transformations (e.g., graphite-to-diamond or vice versa) as compared to conventional leached cutting tables including inter-bonded diamond particles and residual Group VIII catalyst materials (e.g., catalytic cobalt, catalytic iron, catalytic nickel) within interstitial spaces between the inter-bonded diamond particles.

Each of the surfaces of the cutting table302may be polished, or one or more of the surfaces of the cutting table302may be at least partially non-polished (e.g., lapped, but not polished). In addition, the cutting edge316of the cutting table302may be at least partially (e.g., substantially) chamfered (e.g., beveled), may be at least partially (e.g., substantially) radiused (e.g., arcuate), may be partially chamfered and partially radiused, or may be non-chamfered and non-radiused. As shown inFIG.3, in some embodiments, the cutting edge316is chamfered. If the cutting edge316is at least partially chamfered, the cutting edge316may include a single (e.g., only one) chamfer, or may include multiple (e.g., more than one) chamfers (e.g., greater than or equal to two (2) chamfers, such as from two (2) chamfers to 1000 chamfers). If present, each of the chamfers may individually exhibit a width less than or equal to about 0.1 inch, such as within a range of from about 0.001 inch to about 0.1 inch.

FIG.5shows a simplified side elevation view of a cutting element500in the form of an insert for a roller cone drill bit, in accordance with another embodiment of the disclosure. WhileFIGS.3A and3Bdepict particular configurations of the cutting element300,300′ including particular configurations of the cutting table302and the supporting substrate104thereof, different configurations may be employed. The cutting table302and/or the supporting substrate104may exhibit any desired shape. For example, the cutting table302and/or the supporting substrate104may exhibit a one or more shapes (e.g., a dome shape, a conical shape, a frusto conical shape, a rectangular column shape, a pyramidal shape, a frusto pyramidal shape, a fin shape, a pillar shape, a stud shape, or an irregular shape), one or more sizes (e.g., diameter, height), and/or the interface106between the supporting substrate104and cutting table302may be non-planar (e.g., convex, concave, ridged, sinusoidal, angled, jagged, v-shaped, u-shaped, irregularly shaped, etc.). In some embodiments, the cutting table302may exhibit substantially the same shape and/or size (e.g., dimensions) as the supporting substrate104. In additional embodiments, the cutting table302may exhibit a different shape and/or size than the supporting substrate104. As specific, non-limiting examples, the cutting element300,300′ may exhibit a shape similar to that described in any of U.S. Pat. No. 10,954,721 B2 to Russell et al. (Mar. 23, 2021), U.S. Pat. No. 10,590,710 B2 to Vempati et al. (Mar. 17, 2020), U.S. Pat. No. 10,465,447 B2 to Stockey et al. (Nov. 5, 2019), U.S. Pat. No. 9,845,642 B2 to Stockey (Dec. 19, 2017), U.S. Pat. No. 8,887,838 B2 to Stowe, II (Nov. 18, 2014), and U.S. Pat. No. 8,061,456 B2 to Patel et al. (Nov. 22, 2011), the contents of each of which are incorporated herein by this reference.

The cutting element500includes a supporting substrate504, and a cutting table502bonded to the supporting substrate504at an interface506. The cutting table502may have a material composition and a material distribution substantially similar to the material composition and the material distribution of the cutting table302previously described with reference toFIGS.3-4B. In other words, a first, outer region of the cutting table502may be substantially devoid of at least highly catalytic metallic phases, while a second, inner region of cutting table502adjacent supporting substrate504may retain the material composition of the cutting table502as formed and before further processing. In addition, the supporting substrate504may have a material composition and a material distribution substantially similar to the material composition and the material distribution of one or more of the supporting substrates104previously described with reference toFIGS.1-3. As shown inFIG.5, the cutting table502exhibits a generally conical shape, and includes a conical side surface508and an apex501(e.g., tip) that at least partially define a cutting face510of the cutting table502. The apex501comprises an end of the cutting table502opposing another end of the cutting table502secured to the supporting substrate504at the interface506. The conical side surface508extends upwardly and inwardly from or proximate the interface506toward the apex501. The apex501may be centered about a central longitudinal axis of the cutting element500, and may be at least partially (e.g., substantially) radiused (e.g., arcuate). The conical side surface508may be defined by at least one angle θ between the conical side surface508and a phantom line503(shown inFIG.5with dashed lines) longitudinally extending from a lateral side surface of the supporting substrate504. The angle θ may, for example, be within a range of from about five degrees (5°) to about eighty-five degrees (85°), such as from about fifteen degrees (15°) to about seventy-five degrees (75°), from about thirty degrees (30°) to about sixty degrees (60°) or from about forty-five degrees (45°) to about sixty degrees (60°).

Embodiments of cutting elements (e.g., cutting elements300,300′ and500, shown inFIG.3A,FIG.3B, andFIG.5, respectively) described herein may be secured to an earth-boring tool and used to remove subterranean formation material in accordance with additional embodiments of the disclosure. The earth-boring tool may, for example, be a rotary drill bit, a percussion bit, a coring bit, an eccentric bit, a reamer tool, a milling tool, etc. As a non-limiting example,FIG.6shows a fixed-cutter type earth-boring rotary drill bit600that includes cutting elements602. One or more of the cutting elements602may be substantially similar to cutting element300,300′ previously described herein with respect toFIGS.3-4B, and may be formed in accordance to the processes previously described herein with reference toFIG.2. The rotary drill bit600includes a bit body604, and the cutting elements602are attached to the bit body604. The cutting elements602may be, for example, brazed, welded, or otherwise secured, within pockets formed in an outer surface of the bit body604.

An example of a cross-sectional view of the first region308(e.g., a leached layer) in accordance with embodiments of the disclosure are shown in the micrographs inFIG.7A. The image on the left shows an example of the leached layer after an exposure to a leaching agent for a duration of 2-days. The image on the right shows an example of a leached layer after an exposure to a leaching agent for a duration of 4-days. In both the left and right images, the dotted line highlights the depth of penetration of the leaching agent, or the thickness of the first region308of the cutting table302. The dotted line also corresponds to the region of the cutting table above which metallic phases424have been selectively removed.

FIG.7Bshows the metal content of the element, specifically normalized cobalt/aluminum content and total metal content as a function of distance from the surface for different leaching process durations, in particular a 2-day leach and a 4-day leach. The leaching agent utilized for the etching illustrated in the micrographs ofFIG.7Aand the chart ofFIG.7Bmay include composition comprising hydrogen chloride (HCl) and/or nitric acid (HNO3). For example, the leaching agent composition may comprise 1 part by volume HCl and 3 parts by volume HNO3. The acids (e.g., HCl and HNO3) may be reagent grade in purity and concentration. Additionally, the temperature of the leaching agent composition may be from about 65.5° C. (about 150° F.) to about 93° C. (about 200° F.), such as about 82° C. (about 180° F.). The depth of the leach layer may be measured, as inFIG.7B, using Energy-dispersive X-ray spectroscopy (EDS) by determining the phase ratios of cobalt to aluminum present in the cutting element300,300′. For example, the region subjected to a leaching agent exhibits lower amounts of cobalt and aluminum phases indicating the region has been leached and a leach layer depth measured from the surface can be determined. The leached layer of a cutting element subjected to a 2-day leach measures about 84 microns from the surface, whereas the leached layer of an element subjected to a 4-day leach measures about 126 microns from the surface as shown in the graph ofFIG.7B. The total metal content of the leached layer measuring about 84 microns of a cutting element subjected to a 2-day leach is about 5.5 wt %. The total metal content of the leached layer measuring about 126 microns of the cutting element after a 4-day leach is about 6 wt %.

FIGS.8A and8Bare a series of photomicrographs showing and accompanying data of the microstructural comparison of a non-leached region vs. a leached region of a cutting table of a selectively leached cutting element of the disclosure compared to like regions of a conventional cutting element. Referring toFIG.8A, the image in the top left corner is of a portion of a conventional cutting element formed using a Group VIII metal catalyst that has not been subjected to leaching. The image in the bottom left corner is of a portion of the conventional cutting element that has been subjected to leaching. The image at the top right corner is of a portion of cutting element according to the disclosure prior to leaching. The image in the bottom right corner is of a cutting element of the disclosure after leaching. With reference toFIG.8B, the table provides data showing that the total metal content of first region of a selectively leached cutting element of the disclosure is greater than the total metal content of a conventional leached structure, both before a leaching process and after a leaching process, as well as a lower reduction in catalytic metal (e.g., Co) weight content after leaching. For example, the total metal content (in wt %) of conventional leached cutting elements is about 2.45 wt %, whereas the selectively leached cutting element has a total metal content of about 5.09 wt %.

FIG.9is a series of images showing the metal content of a non-leached region vs. a leached region of a selectively leached thermally stable cutting element of the disclosure. The series of images show that there is a high reduction in cobalt, a moderate reduction in aluminum, and a high elevation in tungsten in a leached (e.g., first) region of the cutting element. Cobalt in the final structure is undesirable due to its highly catalytic nature in metallic phases and therefore is significantly targeted for removal from a region of the cutting table by a leaching agent.

FIGS.10A and10Bare a series of images representing wear results of a selectively leached cutting element of the disclosure compared to a conventional partially leached cutting element and the accompanying data.FIG.10Arepresents the visual results of a performance test where the mechanical properties of the cutting elements is tested. For conventionally leached cutting elements, a deep leach may be from about 700 μm to about 1000 μm. Cutting elements that have been selectively leached for about 2 days may have a leach depth from about 80 μm to about 90 μm (e.g., about 84 μm). Cutting elements that have been selectively leached for about 7 days may have a leach depth from about 170 μm to about 210 μm (e.g., about 189 μm). With reference toFIG.10B, the graph shows the wear scar area (WSA) as a function of the number of testing passes. During testing, a single cutting element may be positioned at a prescribed back-rake angle and subjected to a constant depth-of-cut and infeed rate while engaging a rock specimen rotating at a substantially constant speed. As may be readily appreciated by those of ordinary skill in the art, while the WSA of a non-leached cutting element of the disclosure is substantially less than the WSA of a non-leached conventional cutting element, selective leaching of cutting elements of the disclosure further enhances reduction in WSA once selective leaching is performed.

Additional non-limiting example embodiments of the disclosure are described below.

Embodiment 1: A cutting element for an earth-boring tool, comprising a supporting substrate and a cutting table attached to an end of the supporting substrate. The cutting table comprising a first region and a second region. The first region comprising inter-bonded diamond particles and substantially free of at least highly catalytic metallic phases between the inter-bonded diamond particles, one or more non-catalytic compounds within interstitial spaces between the inter-bonded diamond particles, and voids within interstitial spaces between the inter-bonded diamond particles. The second region comprising inter-bonded diamond particles, the non-catalytic compound within interstitial spaces between the inter-bonded diamond particles, and metallic phases within interstitial spaces between the inter-bonded diamond particles. The first region of the cutting table has a content of elemental metal of at least about 2.6 wt %.

Embodiment 3: The cutting element of embodiment 1 or embodiment 2, wherein a thickness of the first region of the cutting table is greater than about 50 μm.

Embodiment 4: The cutting element of any of embodiments 1 through 3, wherein the thickness of the first region of the cutting table is between about 150 μm and about 250 μm.

Embodiment 5: The cutting element of any of embodiments 1 through 4, wherein the metallic phases within interstitial spaces between the inter-bonded diamond particles of the second region of the cutting table comprises one or more of cobalt, iron, nickel and/or alloys thereof.

Embodiment 6: The cutting element of any of embodiments 1 through 5, wherein the first region of the cutting table has a content of elemental metal of from about 3 wt % to about 6 wt %.

Embodiment 7: The cutting element of any of embodiments 1 through 6, wherein the second region of the cutting table is substantially free of voids.

Embodiment 8: The cutting element of any of embodiments 1 through 7, wherein the cutting table has one or more of a radiused cutting edge and a chamfered cutting edge.

Embodiment 9: The cutting element of any of embodiments 1 through 8, wherein the cutting table exhibits a thickness within a range of from about 0.3 mm to about 5 mm.

Embodiment 10: The cutting element of any of embodiments 1 through 9, wherein the cutting table comprises an apex and at least one side surface extending from at least one location at or proximate an interface between the supporting substrate and the cutting table toward the apex. The at least one side surface of the cutting table extending at one or more angles within a range of from about 5 degrees to about 85 degrees relative to a side surface of the supporting substrate.

Embodiment 11: A method of forming a cutting element, comprising: providing a diamond-containing material over a substrate; sintering the diamond-containing material with a homogenized binder to form a cutting table; during the sintering, converting portions of the binder within interstitial spaces between the inter-bonded diamond particles into one or more non-catalytic compounds and one or more metallic phases; substantially removing an amount of at least highly catalytic metal phases of the one or more metallic phases from the cutting face of the cutting table to a selected depth to form a first region of the cutting table, comprising substantially only inter-bonded diamond particles, non-catalytic compounds and voids.

Embodiment 12: The method of embodiment 11, further comprising leaving a second region of the cutting table below the selected leach depth comprising inter-bonded diamond particles, one or more non-catalytic compounds and one or more metallic phases.

Embodiment 13: The method of embodiment 11 or embodiment 12, wherein selectively removing the amount of the at least highly catalytic metallic phases comprises leaching the one or more metallic phases from within the interstitial spaces between the inter-bonded diamond particles.

Embodiment 14: The method of embodiment 13, wherein leaching the one or more metallic phases comprises applying a leaching agent formulated to remove the one or more metallic phases without removing the one or more non-catalytic compounds.

Embodiment 15: The method of any of embodiments 13 through 14, wherein leaching the one or more metallic phases comprises subjecting the cutting table to a highly oxidizing leaching agent.

Embodiment 16: The method of any of embodiments 13 through 15, wherein leaching the one or more metallic phases further comprises subjecting the cutting table to the leaching agent, the leaching agent comprising HNO3and HCl.

Embodiment 17: The method of any one of embodiments 13 through 15, wherein leaching the one or more metallic phases further comprises subjecting the cutting table to the leaching agent, the leaching agent comprising H2SO4and H2O2.

Embodiment 18: The method of any of embodiments 11 through 17, further comprising selecting the depth from the cutting face of the cutting table to be greater than about 50 μm.

Embodiment 19: The method of any of embodiments 11 through 18, further comprising selecting the depth from the cutting face of the cutting table to be in a range from about 100 μm to about 250 μm.

Embodiment 20: An earth-boring tool comprising one or more of the cutting elements of any of embodiments 1 through 10.

While the disclosed device structures and methods are susceptible to various modifications and alternative forms in implementation thereof, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the present disclosure is not limited to the particular forms disclosed. Rather, the present invention encompasses all modifications, combinations, equivalents, variations, and alternatives falling within the scope of the present disclosure as defined by the following appended claims and their legal equivalents.