Patent Publication Number: US-8973687-B2

Title: Cutting elements, earth-boring tools incorporating such cutting elements, and methods of forming such cutting elements

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of the filing date of U.S. Provisional Application Ser. No. 61/407,085, filed Oct. 27, 2010, the disclosure of which is incorporated herein in its entirety by this reference. 
    
    
     FIELD 
     Embodiments of the present disclosure relate generally to cutting elements, to earth-boring tools including such cutting elements, and to methods of forming such cutting elements. Specifically, embodiments of the present disclosure relate to cutting elements including asymmetric interface features. 
     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 (also referred to as “drag bits”) include a plurality of cutting elements that are fixedly attached to a bit body of the drill bit. Similarly, roller cone earth-boring rotary drill bits may include cones that are mounted on bearing pins extending from legs of a bit body such that each cone is capable of rotating about the bearing pin on which it is mounted. A plurality of cutting elements may be mounted to each cone of the drill bit. 
     The cutting elements used in such earth-boring tools often include polycrystalline diamond compact (often referred to as “PDC”) cutting elements, also termed “cutters,” which are cutting elements that include a polycrystalline diamond (PCD) material, which may be characterized as a superabrasive or superhard material. Such polycrystalline diamond materials are formed by sintering and bonding together relatively small synthetic, natural, or a combination of synthetic and natural diamond grains or crystals, termed “grit,” under conditions of high temperature and high pressure in the presence of a catalyst, such as, for example, cobalt, iron, nickel, or alloys and mixtures thereof, to form a layer of polycrystalline diamond material, also called a diamond table. These processes are often referred to as high temperature/high pressure (“HTHP”) processes. The cutting element substrate may comprise a cermet material, i.e., a ceramic-metal composite material, such as, for example, cobalt-cemented tungsten carbide. In some instances, the polycrystalline diamond table may be formed on the cutting element, for example, during the HTHP sintering process. In such instances, cobalt or other catalyst material in the cutting element substrate may be swept into the diamond grains or crystals during sintering and serve as a catalyst material for forming a diamond table from the diamond grains or crystals. Powdered catalyst material may also be mixed with the diamond grains or crystals prior to sintering the grains or crystals together in an HTHP process. In other methods, however, the diamond table may be formed separately from the cutting element substrate and subsequently attached thereto. 
     As the diamond table of the cutting elements interacts with the underlying earth formation, for example, by shearing or crushing, the diamond table may delaminate or fracture because of the high stresses placed thereon. Some cutting elements may include recesses, such as, for example, grooves, depressions, indentations, and notches, formed in the cutting element substrate. The diamond table may include correspondingly mating protrusions. Other cutting elements may locate the recesses in the diamond table and the mating protrusions on the substrate. The increased contact area at the interface between the substrate and the diamond table may prevent delamination by strengthening the bond between the diamond table and the substrate. Conventionally, the recesses and correspondingly mating protrusions are symmetrical about at least one axis. An exemplary, conventional type of interface design is depicted in  FIGS. 1 and 2 . As shown in  FIGS. 1 and 2 , a cutting element substrate  10  includes a symmetric interface feature  12 . The symmetric interface feature  12  is a recess or depression formed in an end of the substrate  10 . The interface feature  12  comprises a plurality of radially extending grooves that terminate or truncate before reaching the peripheral edge of the substrate  10 . In other words, the symmetric interface feature  12  may be said to resemble the spokes of a wheel, or an asterisk. Planes  14 - 14  through  24 - 24  (shown in the two-dimensional view of  FIG. 1  as lines or axes) represent six planes intersecting a central axis  26  of the substrate  10 , the intersection comprising the central axis  26 , not merely a single point thereof, about which the symmetric interface feature  12  is symmetrical. In addition, the symmetric interface feature  12  shown in  FIG. 1  is symmetrical about a plane (not shown) parallel with a top end surface of the substrate  10  that lies halfway down the depth of symmetric interface feature  12 . 
     Elastic waves generated from impact and other high-stress short duration events during stable or unstable earth drilling can contribute to diamond table fracture, delamination, and even catastrophic failure of the cutting element, eventually resulting in failure of the drill bit. The elastic stress waves are usually generated at the point of contact between the cutting face of the diamond table and the underlying earth formation, but they may also be generated elsewhere within the cutting element, bit blades, drill bit, or drill string and propagate through the cutting element. Surfaces and interfaces between dissimilar materials, such as, for example, a cutting element and open air, liquid, or rock; the interface between a diamond table and a cemented tungsten carbide substrate; or the interface between a cemented tungsten carbide substrate and a braze material in pockets formed in blades of the a drag bit are just some examples where elastic stress waves can reflect, concentrate, and even cause failure. In addition to material properties, the geometry of the material or materials through which the waves propagate may contribute to stress wave amplification at these interfaces or at the surfaces defining the solid structure, such as the cutting face or periphery of the diamond table. 
     BRIEF SUMMARY 
     In some embodiments, the present disclosure includes cutting elements comprising a substrate, a polycrystalline table, and an asymmetric interface feature. The substrate has a central axis. The polycrystalline table is attached to the substrate at an interface region at an end of the polycrystalline table. The interface feature comprises a shape that is reflectively asymmetric about at least two planes defined by x, y, and z axes of a Cartesian coordinate system defined to align a z axis of the coordinate system with the central axis of the substrate and to locate a center of the coordinate system at a midpoint along an axial height of the asymmetric interface feature 
     In further embodiments, the present disclosure includes earth-boring tools comprising a body and at least one cutting element attached to the body. The cutting element comprises a substrate having a central axis, a polycrystalline table attached to the substrate at an interface, and an interface feature located at the interface between the substrate and the polycrystalline table. The interface feature comprises a shape that is reflectively asymmetric about at least two planes defined by x, y, and z axes of a Cartesian coordinate system defined to align a z axis of the coordinate system with the central axis of the substrate and to locate a center of the coordinate system at a midpoint along an axial height of the asymmetric interface feature. 
     In yet further embodiments, the present disclosure includes methods of forming a cutting element comprising: forming an asymmetric interface feature at an end of a substrate, the asymmetric interface feature being reflectively asymmetric about at least two planes defined by x, y, and z axes of a Cartesian coordinate system defined to align a z axis of the coordinate system with a central axis of the substrate and to locate a center of the coordinate system at a midpoint along an axial height of the asymmetric interface feature; distributing a plurality of superhard particles on the substrate over the asymmetric interface feature in a mold; and bonding the superhard particles in the mold to form a polycrystalline table attached to the substrate. 
     In additional embodiments, the present disclosure includes methods of forming a cutting element, comprising: forming an asymmetric interface feature in a polycrystalline table, the asymmetric interface feature being reflectively asymmetric about at least two planes defined by x, y, and z axes of a Cartesian coordinate system defined to align a z axis of the coordinate system with a central axis of the polycrystalline table and to locate a center of the coordinate system at a midpoint along an axial height of the asymmetric interface feature; distributing a plurality of hard particles and a plurality of particles comprising a matrix material on the polycrystalline table and over the asymmetric interface feature in a mold; and sintering the plurality of hard particles and the plurality of particles comprising a matrix material in the mold to form a substrate attached to the polycrystalline table. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       While the specification concludes with claims particularly pointing out and distinctly claiming what are regarded as embodiments of the present disclosure, various features and advantages of embodiments of this disclosure may be more readily ascertained from the following description of embodiments of the disclosure when read in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates an overhead view of a prior art interface feature formed in a substrate; 
         FIG. 2  illustrates a perspective view of a prior art substrate comprising the interface feature shown in  FIG. 1 ; 
         FIG. 3  illustrates a simplified perspective view of an earth-boring drill bit comprising at least one cutting element in accordance with one or more embodiments of the present disclosure; 
         FIG. 4  illustrates a partial cutaway perspective view of another earth-boring drill bit comprising at least one cutting element in accordance with one or more embodiments of the disclosure; 
         FIG. 5  illustrates a perspective view of a cutting element including an interface feature in accordance with an embodiment of the disclosure; 
         FIG. 6  illustrates a perspective view of another cutting element including an interface feature in accordance with another embodiment of the disclosure; 
         FIG. 7  illustrates an overhead view of an interface feature in accordance with an embodiment of the disclosure; 
         FIG. 8  illustrates a perspective view of a substrate including the interface feature shown in  FIG. 7 ; 
         FIG. 9  illustrates a side view of a cutting element including an interface feature in accordance with an embodiment of the disclosure; 
         FIG. 10  illustrates a side view of a cutting element including an interface feature in accordance with an embodiment of the disclosure; 
         FIG. 11  illustrates a side view of a cutting element including an interface feature in accordance with an embodiment of the disclosure; 
         FIG. 12  illustrates an overhead view of an interface feature in accordance with an embodiment of the disclosure; 
         FIGS. 13 through 16  illustrate overhead views of interface features in accordance with embodiments of the disclosure; 
         FIG. 17  illustrates an overhead view of a cutting element in accordance with an embodiment of the disclosure; 
         FIG. 18  illustrates a perspective view of the cutting element shown in  FIG. 17 ; and 
         FIG. 19  illustrates a side view of a cutting element in accordance with an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Some of the illustrations presented herein are not meant to be actual views of any particular drill bit, cutting element, or interface feature, but are merely idealized representations that are employed to describe embodiments of the present disclosure. Thus, the drawings are not necessarily to scale and relative dimensions may have been exaggerated for the sake of clarity. Additionally, elements common between figures may retain the same or similar numerical designation. 
     Although some embodiments of the present disclosure are depicted as being used and employed in earth-boring drill bits, such as fixed-cutter rotary drill bits and roller cone bits, persons of ordinary skill in the art will understand that cutting elements having interface features in accordance with the present disclosure may be employed in any earth-boring tool employing a structure comprising a polycrystalline superabrasive material joined to a supporting substrate. Accordingly, the terms “earth-boring tool” and “earth-boring drill bit,” as used herein, 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, percussion bits, core bits, eccentric bits, bicenter bits, reamers, mills, drag bits, hybrid bits and other drilling bits and tools known in the art. 
     As used herein, the term “polycrystalline table” means and includes any structure comprising a plurality of grains (i.e., crystals) of material that are bonded directly together by inter-granular bonds. The crystal structures of the individual grains of the material may be randomly oriented in space within the polycrystalline material. 
     As used herein, the term “inter-granular bond” means and includes any direct atomic bond (e.g., covalent, metallic, etc.) between atoms in adjacent grains of superabrasive material. 
     Referring to  FIG. 3 , a simplified illustration of a fixed-cutter earth-boring drill bit  28  is shown. The drill bit  28  includes a plurality of cutting elements  30  including an interface feature according to one or more embodiments of the disclosure, each cutting element  30  attached to blades  32  that extend from a body  34  of the drill bit  28  for shearing material from a subterranean formation during drilling. The drill bit  28  includes a threaded section  36  at an end opposing the drilling face for connection a drill string (not shown). In operation of drill bit  28 , cutting elements  30  shear formation material from the underlying earth formation being drilled. 
       FIG. 4  is a partial cutaway perspective view of a roller cone earth-boring drill bit  38 . The drill bit  38  includes a bit body  40  having legs  42  depending from the body  40 . A roller cone  44  is rotatably mounted to a bearing pin  46  on each of the legs  42 . One of the bearing pins  46  shown in  FIG. 4  is depicted without the roller cone  44 . Cutting elements  30 ′, conventionally called “inserts” when used in roller cone bits, including an interface feature in accordance with one or more embodiments of the disclosure may be attached to each roller cone  44  by insertion in recesses of a pattern of recesses in the exterior frustoconical surface of the roller cone  44 . In operation of drill bit  38 , the cutting elements  30 ′ impact and crush material of the underlying earth formation being drilled. 
     Referring to  FIG. 5 , a perspective view of a cutting element  30  including an interface feature in accordance with an embodiment of the disclosure is shown. The cutting element  30  includes a substrate  48  and a polycrystalline table  50  attached on an end of the substrate  48  along an interface  52 . The polycrystalline table  50  comprises a cylindrical or disc shape. 
       FIG. 6  is a perspective view of another cutting element  30 ′ including an interface feature in accordance with an embodiment of the disclosure. The cutting element  30 ′ includes a substrate  48  and a polycrystalline table  50 ′ attached on an end of the substrate  48  at an interface  52 ′. The polycrystalline table  50 ′ comprises a hemispherical or dome shape. In other embodiments, the cutting element  30 ′ may comprise a tombstone shape, a chisel shape, or any other cutting element shape or configuration as known in the art. 
     Cutting element substrates in accordance with the present disclosure may comprise a cermet material. The cermet material may comprise a plurality of particles and a matrix material. The plurality of particles of the cermet material may comprise particles of a hard material, such as, for example, tungsten carbide. The matrix material may comprise a metal catalyst, such as, for example, cobalt, nickel, iron, or alloys or mixtures thereof. 
     Polycrystalline tables in accordance with the present disclosure may comprise interbonded grains of a superhard, also termed superabrasive, material. For example, grains of the polycrystalline table may comprise, synthetic diamond, natural diamond, a mixture of synthetic and natural diamond, or cubic boron nitride. The polycrystalline table may comprise a matrix material, such as, for example, a metal catalyst used to enhance grain-to-grain bonding during formation of the polycrystalline table of diamond, disposed in interstitial spaces between grains of the polycrystalline table. The use of catalysts is conventional, and such catalysts commonly include cobalt, nickel, iron and alloys and mixtures thereof. The polycrystalline table may also be leached so that interstitial spaces between grains of the polycrystalline table, or at least a portion thereof, are at least substantially free of a matrix material comprising a catalyst in order to provide thermal stability for the polycrystalline table exposed to frictional heat during a subterranean drilling operation. Other, non-metallic carbonate catalysts are known, but require more rigorous high temperature, high pressure processing in diamond table fabrication and so are not widely used. However, carbonate catalysts do not require removal from a diamond table for thermal stability. 
     Referring to  FIGS. 7 and 8 , overhead and perspective views of an asymmetric interface feature  54  is shown. The asymmetric interface feature  54  comprises a recess or depression formed in an end of a substrate  48 . The substrate  48  comprises a central axis  60 . A Cartesian coordinate system having x, y, and z axes, the x, y, and z, axes being at right angles to one another, may be defined to align the z axis with the central axis  60  of the substrate  48 . Orthogonal planes may be defined by the x-y, the x-z, and the y-z planes. The coordinate system may also be defined to position the center (i.e., the intersection of the x, y, and z axes) on the central axis  60  at a midpoint along the axial height of the asymmetric interface feature  54 . In some embodiments, the asymmetric interface feature  54  may be rotationally asymmetric about the central axis  60 . In some embodiments, the asymmetric interface feature  54  may be reflectively asymmetric (also referred to as “mirror asymmetry,” “mirror-image asymmetry,” and “bilateral asymmetry”) about at least two of the x-y, the x-z, and the y-z planes. In other words, a first half of the asymmetric interface feature  54  may not comprise a symmetric mirror image projection of a second half of the asymmetric interface feature  54  when divided by at least two of the x-y, the x-z, and the y-z planes. In other embodiments, the asymmetric interface feature  54  may be reflectively asymmetric about each of the x-y, the x-z, and the y-z planes. In addition, the asymmetric interface feature  54  may comprise a combination of rotational and reflective asymmetry. The coordinate system may be translated or rotated within the substrate  48  to more accurately describe any combination or degree of asymmetry. Furthermore, the asymmetric interface feature  54  may be rotationally and reflectively asymmetric about all planes and axes intersecting with the substrate  48 . 
     For example, the asymmetric interface feature  54  may comprise radially extending grooves or spokes  56  resembling the spokes of a wheel or an asterisk. Each radially extending spoke  56  is curved, regions  58  of the substrate  48  between each spoke  56  being correspondingly curved to point in a counter-clockwise direction as viewed from above. The degree to which each region  58  is curved varies from one region  58  to another region  58 . In other words, the regions  58  between each spoke  56  terminate at different angles. Accordingly, the radial distance to the curved end portion of each region  58  as measured from a central axis  60  of the substrate  48  varies in a non-uniform manner. 
     In addition, each spoke  56  may have a different radial length as measured from the central axis  60  of the substrate  48 . Accordingly, each spoke  56  may terminate at a different radial distance as measured from the perimeter of the substrate  48 . Each side surface of each spoke  56  may exhibit a unique camber. In other words, surfaces of each spoke  56  that are not parallel to the top surface of the substrate  48  may be curved, each surface having a different radius of curvature. Moreover, the radially outer surfaces of each spoke  56 , surfaces proximate the perimeter of the substrate  48 , may be canted to a non-uniform degree. 
       FIG. 9  is a side view of a cutting element  30  including an asymmetric interface feature  54  in accordance with an embodiment of the disclosure. The cutting element  30  includes a substrate  48  and a polycrystalline table  50  attached on an end of the substrate  48  at an interface  52 . The cutting element  30  further comprises an asymmetric interface feature  54  at the interface  52  between the substrate  48  and the polycrystalline table  50 . The asymmetric interface feature  54  comprises a protrusion on an end of the substrate  48  and a corresponding recess in the polycrystalline table  50 . Accordingly, persons of ordinary skill in the art will understand that the asymmetric interface feature  54  may comprise a protrusion formed on a substrate and a corresponding recess formed in a polycrystalline table, a protrusion formed on a polycrystalline table and a corresponding recess formed in a substrate, or a combination of protrusions and recesses in both the polycrystalline table and the substrate. 
     The asymmetric interface feature  54  comprises a plurality of radially extending spokes  56 . Further, the asymmetric interface feature  54  curves in an upward direction toward the polycrystalline table  50  along the central axis  60  of the cutting element  30 . In other words, the asymmetric interface feature  54  comprises domed radially extending spokes  56 . The radius of curvature of the domed spokes  56  may vary across the asymmetric interface feature  54 . In this way, the asymmetric interface feature  54  may be asymmetric about planes and axes that intersect the cutting element  30  and are parallel to the top surface or cutting face of the polycrystalline table  50 . In addition, the radius of curvature of the domed spokes  56  may vary in a different manner along each spoke  56 , contributing to the overall asymmetry of the asymmetric interface feature  54 . 
     Referring to  FIG. 10 , a side view of a cutting element  30  including an asymmetric interface feature  54  in accordance with an embodiment of the disclosure is shown. As shown in  FIG. 10 , spokes  56  of the asymmetric interface feature  54  may exhibit a twist about a radially extending axis in the center of each spoke  56 . Each spoke  56  may be twisted in a non-uniform manner along the radial length of the spoke  56 . Each spoke  56  may exhibit a non-uniform degree of twisting. In addition, the amount of twist in each spoke  56  may vary as the radial distance from the central axis  60  of the cutting element  30  increases. 
       FIG. 11  illustrates a side view of a cutting element  30  including an asymmetric interface feature  54  in accordance with an embodiment of the disclosure. As shown in  FIG. 11 , surfaces of the spokes  56  where the polycrystalline table  50  abuts against and attaches to the substrate  48  may comprise undulations or other irregularities, asperities, or non-symmetric deformations. Though the undulations shown in  FIG. 11  are shown as ridges and depressions across the width of the spoke  56 , undulations may be in any direction, such as, for example, along the radial length of the spoke  56  or diagonally across the spoke  56 . The undulations may be non-uniform within each spoke  56 . Moreover, each spoke  56  may comprise differing undulations from each other spoke  56 . 
     Referring to  FIG. 12 , an overhead view of an interface feature  54 ′ in accordance with an embodiment of the disclosure is shown. The interface feature  54 ′ comprises a plurality of asterisk-shaped recesses formed in a substrate  48 . In other embodiments, the interface feature  54 ′ may comprise a plurality of asterisk-shaped protrusions formed on the substrate  48 . Each asterisk-shaped recess of the interface feature  54 ′ may comprise any or all of the aforementioned features, such as, for example, radially extending spokes, curves, camber, canting, portions at varying non-uniform radial distances, domed surfaces, twisting, and undulations, used in combination to contribute to the overall asymmetry of the interface feature  54 ′. Moreover, the asterisk-shaped recesses may be distributed in the substrate  48  in a non-uniform asymmetric manner. 
       FIGS. 13 through 16  illustrate overhead views of interface features  54 ′ in accordance with embodiments of the disclosure. Interface features  54 ′ in accordance with embodiments of the present disclosure may comprise recesses or protrusions that are not asterisk-shaped. For example, an interface feature  54 ′ may comprise polygons having varying numbers of side surfaces, as shown in  FIG. 13 . An asymmetric interface feature  54  may also comprise a combination of straight and curved side surfaces, as shown in  FIG. 14 . An asymmetric interface feature  54  may also comprise a shape that is not easily geometrically described, as shown in  FIG. 15 . An interface feature  54 ′ may also comprise a plurality of shapes not easily geometrically described, the shapes being distributed in a non-uniform asymmetric manner, as shown in  FIG. 16 . Accordingly, persons of ordinary skill in the art will understand that asymmetric interface feature  54  and interface feature  54 ′, in accordance with the present disclosure, may comprise any shape or shapes employing any of the aforementioned features to contribute to the overall asymmetry of asymmetric interface feature  54  and interface feature  54 ′. 
     In addition, persons of ordinary skill in the art will understand that the interface  52  between the substrate  48  and the polycrystalline table  50  may not comprise readily identifiable boundaries. For example, a mixture of superhard particles, hard particles, and powdered catalyst material may be provided in between the polycrystalline table  50  and the substrate  48  and sintered to form an intermediate region. The intermediate region formed by the mixture of superhard particles, hard particles, and powdered catalyst material may be uniform throughout the layer, or may be graded. Thus, the boundary between the substrate  48  and the polycrystalline table  50  may exhibit a gradient as the material composition transitions from the hard particles of the substrate  48  to the superhard particles of the polycrystalline table  50 . In fact, the gradient may be selectively distributed to be asymmetric about all planes and axes intersecting with the transition region between the substrate  48  and the polycrystalline table  50 . 
     Referring to  FIGS. 17 and 18 , a cutting element  30 ″ in accordance with an embodiment of the disclosure is shown. The cutting element  30 ″ includes a polycrystalline table  50  attached to a substrate  48 . The cutting element  30 ″ may comprise a generally oval cross-section. As best shown in  FIG. 17 , the generally oval cross-section of the cutting element  30 ″ may comprise undulations or other irregularities, asperities, or non-symmetric deformations. Thus, the geometry of the cutting element  30 ″ cross-section may be asymmetric about all planes and axes intersecting with the cutting element  30 ″. Additionally, the lateral side surfaces of the polycrystalline table  50  and the substrate  48  may comprise undulations or other irregularities, asperities, or non-symmetric deformations, as best shown in  FIG. 18 . Thus, the geometry of the lateral side surface of the cutting element  30 ″ may be asymmetric about all axes and planes intersecting with the cutting element  30 ″. 
     Referring to  FIG. 19 , a cutting element  30 ″ in accordance with an embodiment of the disclosure is shown. The cutting element  30 ″ includes a polycrystalline table  50  attached to a substrate  48 . A cutting face  62 , the interface  52  between the polycrystalline table  50  and the substrate  48 , and a back end  64  of the cutting element  30 ″ may comprise undulations or other irregularities, asperities, or non-symmetric deformations. Thus, the geometry of cutting face  62 , the interface  52  between the polycrystalline table  50  and the substrate  48 , and the back end  64  of the cutting element  30 ″ may be asymmetric about all axes and planes intersecting with the cutting element  30 ″. 
     In summary, interface features at the interface region between the polycrystalline table and the substrate of a cutting element may be asymmetric about all planes and axes that intersect with the interface features. Being asymmetric about all planes and axes that intersect with the interface features may mean that substantially all describable feature dimensions of the interface feature may differ in size, shape, and orientation from all other feature dimensions in the interface feature. Any or all of the foregoing asymmetric aspects may be used in combination with one another to contribute to the overall asymmetry of the interface feature. In addition, the cutting element geometry itself may be asymmetric. Variations in the geometry of the cutting element and the interface feature may be selected to attenuate elastic waves by taking into account the wave attenuation enabled by the material properties of the cutting element, and by taking into account the different types of elastic waves, such as, for example, primary waves (“pressure waves” or “P-waves) and secondary waves (“shear waves” or “S-waves”). A finite element analysis may aid in selecting the appropriate geometry and degree of asymmetry for a given application. Moreover, persons of ordinary skill in the art will understand that the foregoing asymmetric aspects may be used in connection with interface features that do not comprise radially extending spokes, such as, for example, annular grooves, speckled protrusions, or any geometric shape. The asymmetric geometry may prevent stress wave reflections from amplifying back on themselves and improve wave dispersion, ultimately increasing the durability of a cutter by reducing the fractures related to the stress amplifications. Stated another way, the presence and configurations of asymmetric interface features may attenuate elastic waves to reduce or eliminate fracturing, cracking, spalling, and delamination of a polycrystalline table from a supporting substrate, and ultimate failure of the cutting element. The required amount of asymmetry will vary depending on the material properties of regions of the cutting element and the stress wave amplitude and frequency or amplitudes and frequencies anticipated to be encountered during a drilling operation. Such required degree of asymmetry can be mathematically modeled using finite element analysis techniques. 
     Asymmetric interface features may be formed integrally with portions of the cutting element. By way of example, an asymmetric interface feature may be formed integrally while forming a substrate. A plurality of hard particles and a plurality of particles comprising a matrix material may be disposed in a mold. The mold may include features formed therein, the features being configured to impart an asymmetric interface feature to a formed substrate. In other embodiments, the mold may not include features configured to impart an asymmetric interface feature to the formed part, but the asymmetric interface feature may be formed into the part subsequently, such as, for example, by conventional machining processes. The hard particles and the particles comprising a matrix material disposed in a mold may then be pressed to form a green part, which may include the asymmetric interface features at one end thereof, or the green part may be removed from the mold and the asymmetric interface features machined from one end thereof. Pressing to form a green part may be sufficient for the green part to retain the shape imparted to it by the mold. In other embodiments, the green part may be partially sintered in the mold to form a brown part, which may also be machinable if the asymmetric interface features are not already formed. In still other embodiments, the green part may be fully sintered in the mold to a final density, the fully sintered part being a substrate comprising an asymmetric interface feature. Diamond grit, or another mixture of superhard particles, and particles comprising a catalyst material may be provided in a mold containing any of the green part, the brown part, or the fully sintered substrate, and may be subjected to an HTHP process to form a polycrystalline table. The HTHP process may also fully sinter the green or brown parts to a fully sintered substrate. A cutting element comprising a polycrystalline table, a substrate, and an asymmetrical interface feature at the interface between the polycrystalline table and the substrate may thus be formed. The polycrystalline table may be partially or completely leached of the catalyst material in subsequent processing. 
     In other embodiments, an asymmetric interface feature may be formed integrally while forming a polycrystalline table. Diamond grit, or another mixture of superhard particles, and particles comprising a catalyst material may be provided in a mold. The mold may include features formed therein, the features being configured to impart an asymmetric interface feature to a formed polycrystalline table. The mixture of superhard particles and particles comprising a catalyst material may then be subjected to an HTHP process to form a polycrystalline table comprising an asymmetric interface feature. The polycrystalline table may then be combined with hard particles and particles comprising a matrix material in a mold. The mold may then be pressed and heated, sintering the hard particles and particles comprising a matrix material into a substrate and attaching the preformed polycrystalline table to the substrate at an interface comprising the asymmetric interface feature. The polycrystalline table may be partially or completely leached of the catalyst material at any time after formation. 
     Of course, both the polycrystalline table and the substrate may each be preformed with mating, asymmetric interface features, and attached, as by brazing or by melting of a metal foil or other metal layer placed between the components or preformed on one of them and heating under application of pressure. 
     While the present disclosure has been described herein with respect to certain example embodiments, those of ordinary skill in the art will recognize and appreciate that it is not so limited. Rather, many additions, deletions, and modifications to the embodiments described herein may be made without departing from the scope of embodiments of the invention as hereinafter claimed, including legal equivalents. In addition, features from one embodiment may be combined with features of another embodiment while still being encompassed within the scope of embodiments of the invention as contemplated by the inventor.