Abstract:
A superabrasive cutting element attachable to a drill bit for drilling subterranean formations is formed of a substrate and a superabrasive table with a three-dimensional interface comprising a continuous wave pattern extending about a central axis. Multiple outwardly directed arches of the wave pattern are oriented and configured to preferentially accommodate loading experienced by the cutting element during drilling to absorb and distribute stresses resulting therefrom. Thus, any tendency toward fracture and spalling of the superabrasive table and delamination thereof from the substrate, any of which may induce catastrophic failure of the cutting element, are substantially reduced. A rotary drill bit including such cutting elements is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to superabrasive cutting elements and, more specifically, to polycrystalline diamond compact cutting elements comprising a polycrystalline diamond table formed and bonded to a supporting substrate or backing during formation of the cutting element and drill bits for subterranean drilling equipped with such cutting elements. 
     2. State of the Art 
     Superabrasive elements are used extensively in drilling, cutting, milling, and other operations relating to the removal of portions of hard materials. A superabrasive element useful in subterranean, drilling may conventionally include a table formed of polycrystalline diamond particles or, less typically, cubic boron nitride particles sintered under high pressure, high temperature conditions into a coherent conglomerate mass termed a “compact.” In order to support the hard but relatively brittle table, it is typically bonded during sintering to a substrate of, e.g., cemented carbide. A plurality of such cutting elements is typically mounted to a rotary drill bit for drilling subterranean formations. 
     Typically, such cutting elements are formed by placing a cemented tungsten carbide substrate preform into a press, and placing, for example, diamond grains, optionally with a catalyst binder, atop the substrate preform. Under the aforementioned high pressure and temperature, the diamond grains are bonded to each other and to the substrate in the sintering process, forming a diamond table. 
     Polycrystalline diamond compact cutting elements, commonly known as PDCs, have been commercially available for more than 20 years and have been widely used, particularly on bits for subterranean drilling. In a variation of the PDC, residual metal and catalyst is leached from the diamond table to form a thermally stable product (TSP), or a silicon-bonded TSP may be formed, silicon having a coefficient of thermal expansion (CTE) similar to that of diamond. 
     The use of PDC and TSP cutting elements in rotary drag bits for earth boring has resulted in major increases in penetration rates and overall reductions in drilling costs for a broadened range of rock formation types. 
     Nevertheless, several problems have become evident in using PDC and TSP cutting elements. High residual stresses attributable to the aforementioned high pressure, high temperature fabrication conditions may be present in such cutting elements, particularly adjacent the table-substrate interface, and may lead to fracturing of the superabrasive table, separation from the substrate and failure of the element. Such stresses are largely attributable to the differences in CTE between the diamond and the carbide; cooling of the cutting element after fabrication results in greater shrinkage of the substrate than of the polycrystalline diamond material. 
     Furthermore, spalling, fracture and delamination of the table material from the substrate may occur during attachment of the cutting element to a tool, or during normal drilling operations, because of high bending forces applied during attachment, or by contact with the subterranean formation itself as weight on bit (WOB) is applied and torque is applied to rotate the bit to engage the formation. Diamond has an extremely low strain rate to failure and cannot tolerate flexing resulting from high applied forces. Fracture or delamination, once initiated, ultimately leads to failure of the cutting element. Any means to reduce the frequency of bit failure will have a significant beneficial economic effect in drilling operations. 
     Various attempts have been made to reduce the incidence of cutting element failures adjacent the table/substrate interface. 
     In U.S. Pat. No. 4,629,373 of Hall, the substrate is eliminated, and the cutting table is directly attached to, e.g., a metal drill bit. The attachment surface is formed with surface irregularities including parallel grooves, crosshatch grooves, wire-mesh grooves, and the like. 
     The disclosure of Griffin in U.S. Pat. No. 5,469,927 teaches the addition of a transition layer between the cutting table and the substrate, in which the transition layer has at least one property intermediate the properties of the cutting table and the substrate. In U.S. Pat. No. 5,011,515 of Frushour, a transition layer has properties which gradually vary from the cutting table to the substrate. 
     The substrate-table interface may be formed with a series of sloping surfaces about a central axis, as depicted in U.S. Pat. Nos. 5,484,330 and 5,486,137 of Flood et al. 
     In U.S. Pat. No. 5,709,279 of Dennis, the table-substrate interface is formed in an undulating sinusoidal wave fonn, the sine wave amplitude varying in a direction parallel to the central axis. 
     As taught in U.S. Pat. No. 5,605,199 of Newton, the cutting table may be formed with increased thickness about its periphery. In addition, a series of adjacent, parallel, straight grooves and ridges in the interface is shown. 
     In U.S. Pat. No. 5,564,511 of Frushour and U.S. Pat. No. 5,622,233 of Griffin, the table/substrate interface is proposed to be formed with a plurality of-discrete protuberances projecting perpendicularly to the general interfacial plane. The protuberances may be bulbous or conical, the interface resembling an egg carton or acoustical foam. 
     In U.S. Pat. No. 5,007,207 of Phaal and U.S. Pat. No. 5,355,969 of Hardy et al., concentric circular or semicircular ridges and grooves about a central axis of the interface are shown. 
     In U.S. Pat. No. of 5,351,772 of Smith, a wide variety of interfacial patterns is shown with radially directed, interleaved grooves and ridges. 
     In U.S. Pat. No. 5,590,728 of Matthias et al., table-substrate interfaces are shown with generally radially directed grooves and ridges having straight, angular, bulbous, or somewhat twisted configurations. 
     In U.S. Pat. No. 5,611,649 of Matthias, a star-shaped pattern of interfacial grooves and ridges is shown. Both U.S. Pat. No. 5,611,649 of Matthias and U.S. Pat. No. 5,617,928 of Matthias et al. teach the use of concentric semicircular grooves and ridges with a central axis outside or nearly outside the circumferential periphery of the table and substrate. 
     Despite all the aforementioned suggested improvements in the interface design, cutting elements continue to fail because of high loads and attendant stresses experienced during drilling operations. Drill bit repair and replacement and consequent lost rig time comprise major expenses in the drilling industry. Thus, further advancements in the art are necessary to enhance the cutting table-substrate bond strength in order to improve drill bit performance reduce downtime and the necessity for cutting element replacement and drill bit replacement and repair. 
     BRIEF SUMMARY OF THE INVENTION 
     The cutting element of the present invention comprises a substantially planar table of circular, polygonal or other suitable cross-section comprising superabrasive material having an underside joined along a three-dimensional interface to a supporting substrate. At the interface, a pattern comprising one or more corresponding grooves and ridges is formed so that the table material projects into the substrate, and/or vice versa. The particular interfacial groove-and-ridge pattern of the present invention includes at least one narrow elongate groove which forms a pattern with a plurality of outwardly extending lobes. The pattern, which may also be characterized as a wave pattern, lies completely within the circumferential periphery of the cutting element, forming a series of generally radially inwardly and outwardly facing arches which alleviate and distribute temperature-induced stress in the interface region upon cooling of the cutting element of the fabrication, as well as enabling the cutting element to better withstand Normal and tangential impact loading-induced stresses experienced during drilling. Preferably, the number of lobes or arches of the interface pattern comprises a whole number from 2 to about 30 and, more preferably, a whole number from about 3 to about 24, although the preferred upper limit may vary with the size (diameter) of the cutting element. 
     A ridge of the pattern may comprise an extension or protrusion of the superabrasive table which fills a complementary groove in the substrate or, alternatively, may comprise an extension of the substrate material which fills a complementary groove in the cutting table. 
     The wave pattern as a whole may comprise a continuous, generally sinusoidal function located within a range of radii about the central axis of the cutting element. Two or more wave patterns may be used, each located within a different radius range, i.e., in a generally concentric configuration. The range of radii of adjacent wave patterns may overlap. The periods as well as the amplitudes of the wave patterns may differ. Thus, an inner wave pattern may have less, the same, or more outwardly directed lobes or arches than a relatively outer wave pattern. 
     Normally, the period and amplitude of a wave pattern may be uniform, i.e., non-variable. However, the period and amplitude within a given wave pattern may be configured to be non-uniform. Thus, a pattern with varied lobe sizes and/or spacings is formed. 
     The continuous wave pattern about a longitudinal, e.g., central axis of the cutting element may comprise a simple or complex sine function. Alternatively, the wave pattern may be a series of semicircles, hemi-ellipses, etc., having their ends joined and arranged in a continuous circumferential pattern about the central axis, wherein the convex faces of the arcuate lobes are directed outwardly. 
     The attachment surface, i.e., underside, of the table is formed on and bonded to the substrate by any method which provides the desired bond strength and hardness characteristics. Typically, the table is integrally formed and bonded to the substrate during sintering under conditions of high temperature and pressure as known in the art. 
     The cutting element is typically configured to be mounted to a drill bit for boring in subterranean formations. 
     The present invention is particularly applicable to PDC, TSP and cubic boron nitride compact cutting elements, but is not so limited. 
     In the present invention, the ability of an arcuate structure to absorb and distribute high applied loads is utilized to advantage. The multiple arches of the wave pattern, facing the direction from which normal drilling stresses occur, distribute such drilling loads to preclude fracture, spalling, and delamination of the superabrasive table. The arcuate wave pattern of ridges and grooves also enhances resistance to interfacial debonding of the table from the substrate during fabrication of the cutting element and during attachment thereof to a drill bit. 
     While it is currently contemplated that the groove and corresponding ridge structures be physically continuous in the sense of being unbroken or unsegmented, as used herein, the term “continuous wave pattern” denotes that the overall pattern itself is substantially continuous, but does not preclude the formation of such patterns using intermittent or segmented ridges and cooperative grooves, so that a given pattern may resemble, or be defined by, a dotted or broken line comprising groove and matching ridge segments, instead of a continuously extending physical structure. Moreover, the ridge and groove segments need not be of equal length throughout a given pattern. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following drawings illustrate various exemplary embodiments of the invention, not necessarily drawn to scale, wherein: 
     FIG. 1 is a perspective view of an exemplary drill bit incorporating cutting elements of the present invention; 
     FIG. 2 is an enlarged perspective view of an exemplary cutting element of the invention; 
     FIG. 3 is a perspective exploded view of an exemplary cutting element of the invention; 
     FIG. 4 is a reduced cross-sectional view of an exemplary cutting element of the invention, as taken along line  4 — 4  of FIG. 2; 
     FIG. 4A is a reduced cross-sectional view of another exemplary cutting element of the invention, as taken along line  4 — 4  of FIG. 2; 
     FIG. 5 is a perspective exploded view of another exemplary embodiment of a cutting element of the invention; 
     FIG. 6 is a reduced cross-sectional view of another exemplary embodiment of a cutting element of the invention, as taken along line  6 — 6  of FIG.  5 . 
     FIG. 7 is an enlarged plan view of a substrate-table interface having an exemplary two-lobe interfacial pattern of a cutting element of the invention; 
     FIG. 8 is an enlarged plan view of a substrate-table interface having an exemplary three-lobe interfacial pattern of a cutting element of the invention; 
     FIG. 9 is an enlarged plan view of a substrate-table interface of an exemplary four-lobe interfacial pattern having a cutting element of the invention; 
     FIG. 10 is an enlarged plan view of a substrate-table interface having an exemplary four-lobe interfacial pattern of a cutting element of the invention; 
     FIG. 10A is a reduced cross-sectional view of an exemplary four-lobe substrate-table interface of a cutting element of the invention, as taken along line  10 A— 10 A of FIG. 10; 
     FIG. 10B is a reduced cross-sectional view of another exemplary four-lobe substrate-table interface of a cutting element of the invention, as taken along line  10 A— 10 A of FIG. 10; 
     FIG. 11 is an enlarged plan view of a substrate-table interface with an exemplary, triple five-lobe interfacial pattern of a cutting element of the invention; 
     FIG. 12 is an enlarged plan view of a substrate-table interface with an exemplary, double six-lobe interfacial pattern of a cutting element of the invention; 
     FIG. 13 is an enlarged plan view of a substrate-table interface with an exemplary, outer eight-lobe interfacial pattern combined with an inner four-lobe pattern of a cutting element of the invention; and 
     FIG. 14 is an enlarged plan view of a substrate-table interface with an exemplary sixteen-lobe interfacial pattern of a cutting element of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In this invention, superabrasive cutting elements for earth boring drill bits are formed in a manner which reduces the incidence of fracture and separation of the cutting table from the underlying substrate along the table-substrate interface. 
     In FIG. 1 is shown an exemplary, but not limiting, drill bit  10  which incorporates cutting elements  20  of the invention. Drill bit  10  is known in the art as a rotary, fixed cutter, or “drag” bit, useful for drilling in subterranean formations such as formations above oil and gas-bearing formations as well as the latter. Cutting elements  20  of this invention may be advantageously used in any of a wide variety of drill bit configurations which use superabrasive cutting elements. Drill bit  10  includes a bit shank  12  having a pin end  14  for threaded connection to a drill string, not shown, and also includes a body  16  having a face  18  on which cutting elements  20  may be secured. Bit  10  typically includes a series of nozzles  22  for directing drilling mud to the bit body face  18  for removal of formation cuttings to the bit gage  24  and passage thereof through junk slots  26 , past the bit shank  12  and drill string to the ground surface. The improved cutting elements  20  of this invention have one or more generally concentric multiple arch or lobe patterns in the table-substrate interface  36  (see FIG.  2 ), which reduces the incidence of spalling, fracture and delamination of the table from the substrate, any of which may lead to catastrophic cutting element failure. 
     The cutting element  20  of the present invention includes a superabrasive table  30  of circular, rectangular or other polygon, oval, truncated circular, or other suitable crosssection, although circular is preferred. The cutting element  20  is formed with a cutting face  34  comprising one side of the table  30  of the superabrasive material such as polycrystalline diamond, the table  30  having an underside (attachment) face  32  joined to a supporting substrate  40  formed of a hard material such as a cemented tungsten or other carbide. The substrate may be preformed in a desired shape such that a crystalline diamond material may be molded into the polycrystalline diamond table  30  thereon and simultaneously strongly bonded to the substrate under sintering conditions. The table  30  which is formed is complementary to the substrate  40  such that a unitary, solid cutting element  20  is formed with essentially no voids at the table substrate interface  36 . 
     The projection of the groove pattern  44  in the substrate  40  or table  30  is essentially identical to that of the ridge pattern  54  in the opposing member, the ridge  50  thus filling the groove  60 . The combined ridge-and-groove pattern will be identified herein by the numeral  38  (also referred to herein as “wave pattern  38 ”). Such a pattern  38  includes a ridge  50  and a groove  60  which together delineate a wave pattern in the interface  36  between table  30  and substrate  40 . 
     As shown in FIGS. 2,  3  and  4 , a cutting element  20  of the invention comprises a table  30  with a cutting face  34  and an attachment face  32 , and a substrate  40  with a matching attachment face  42 . The interface, including both attachment faces  32 ,  42 , ridge pattern  54  and groove pattern  44 , is identified herein by the numeral  36 . 
     The cutting element  20  is depicted as having a central axis  28  and a generally circular cross-section about the axis. Alternatively, the cutting element  20  may have multiple sides or surfaces lying about axis  28 . Thus, for example, the cutting clement  20  may have a hexagonal, rectangular, or oval cross-section. 
     In FIG. 3, a ridge  50  with ridge pattern  54  is shown as comprising a continuous, narrow, elongate extension or protrusion of the material of table  30  from the table attachment face  32 . A groove  60  with matching groove pattern  44  is shown in the attachment face  42  of the substrate  40 . When the table  30  is joined (typically formed on) to the substrate  40 , the ridge  50  fills the groove  60 . 
     In the example of FIGS. 3 and 4, the groove-and-ridge pattern  38  is shown as a continuous, generally angular, sinusoidal configuration of ridge  50  and groove  60  about radius  70 . The amplitude is the maximum deviation from radius  70 , and may be positive or negative. In the convention used herein, a positive amplitude  72  is indicated when the radius  76  from central axis  28  exceeds the radius  70 . A negative amplitude  74  is indicated when the radius  78  from central axis  28  is less than radius  70 . 
     In FIGS. 3 and 4, the groove-and-ridge pattern  38  has a period P of one fourth of a complete revolution about central axis  28 . Thus, the number of outwardly extending lobes or arches  56  on attachment faces  32 ,  42  equals four. 
     The ridge  50  (and matching groove  60 ) is shown as having a generally radiused cross-sectional shape in FIG.  4 . This is the preferred shape from the standpoint of resistance to fracture, but other shapes may be used, including quadrilateral as depicted in FIG.  4 A. The groove depth dimension  62  may be typically about 0.2 to 1.5 times the groove width  66 . In general, it is currently believed that the groove width  66  may preferably vary from about 0.2 to about 1.5 mm, and the groove depth  62  from about 0.04 to about 2.2 mm. The width and depth of the matching ridge  50  will, of course, be in the same range. 
     In this description, an outermost wave pattern  38  may be characterized for convenience as a “primary” wave pattern, inasmuch as additional wave patterns  38 A may be concentrically formed within the primary wave pattern  38 . 
     Turning to FIGS. 5 and 6, the table  30  and substrate  40  of a cutting element  20  are shown. As compared to the embodiment of FIG. 3, the groove pattern  44  and ridge pattern  54  are reversed, so that the ridge  50  projects from the substrate  40  into a groove  60  in the table  30  of superabrasive material. In each of the various patterns  38  which may be used, the ridge  50  may project from either the table  30  or substrate  40 . As will be seen, infra, when multiple generally concentric patterns  38  are used, the ridge  50  of each pattern may project from either the table  30  or substrate  40 . 
     The particular interfacial groove-and-ridge pattern  38  of this invention includes a narrow elongate groove  60  (and matching ridge  50 ) which forms a wave pattern  38  with a plurality of outwardly extending lobes or arches  56 . The pattern  38  is completely within the circumferential periphery  46  of the interface  36 , forming a series of lobes or arches  56  which alleviate and/or distribute both the temperature-induced stress upon cooling of the cutting element after fabrication and the normal and tangential impact stresses experienced during drilling. Preferably, the number of lobes or arches  56  comprises a whole number from 2 to about 30 and, more preferably, from 3 to about 24, although the preferred upper limit is somewhat dependent upon the diameter of the cutting element in question. 
     The wave pattern  38  may be a continuous, generally sinusoidal function about a base radius  70  of the central axis  28 . Two or more wave patterns  38  may be used, each being a function of a different base radius  70 , i.e., in a generally concentric configuration. The number of wave patterns  38  may be up to 6 or more. The periods P as well as the amplitudes  72 ,  74  of the wave patterns  38  may differ, although in a pure sinusoidal pattern, the amplitudes have the same absolute value. Normally, the period P and amplitudes  72 ,  74  of the wave pattern  38  may be uniform, i.e., non-variable. However, the period P and amplitudes  72 ,  74  within a given wave patterns  38  may be configured to be non-uniform. Thus, a pattern  38  with varied sizes and/or spacing of lobes or arches  56  may be formed. 
     The wave pattern  38  may comprise a sine function: 
     
       
         Y=Fb sin( nα+z ) 
       
     
     where: Y=the radial distance from the base radius  70  of the function; 
     F=a function of any kind which changes the shape of the sinusoidal curve. For a simple pattern, F=1; 
     n=the number of outwardly extending lobes or arches  56  in a continuous groove-and-ridge pattern  38 ; 
     α=the distance through which the wave function passes, as an angle about a centerpoint (e.g., center axis  28 ) of the base radius  70 ; 
     b is the amplitude of the sine function; and 
     z is a function which moves the entire sinusoidal pattern about a centerpoint which normally is the center axis  28 . Normally, z is set at zero. 
     The variable α is an angular function comparable to linear variable X of a linear sinusoidal function Y=sin X. The function Y may be positive or negative relative to the base radius  70 . In this application, Y is considered positive when the radial distance  76  from the central axis  28  exceeds the base radius  70 , and negative when the radial distance  78  from the central axis  28  is less than the base radius  70 . 
     FIGS. 7 through 12 are enlarged plan views of the interface  36  of various exemplary embodiments of the invention, not intended to be limitations thereof. The wave functions are depicted as being taken along the outer edge  48  of the ridge  50  or groove  60 . In FIG. 7, a wave pattern  38  of ridge  50  and groove  60  is shown with two outwardly extending lobes or arches  56 . The radial position Y is a function of the positive and negative amplitudes  72 ,  74 , angle α and the value of radius  70 . The period P of the function is 180 degrees and the frequency F is 360/P, i.e., 2.0. 
     In FIG. 8, a wave pattern  38  with three lobes  56  is shown. The positive and negative maximum amplitudes  72 ,  74  of radial position Y are depicted. The period P of the wave function is 120 degrees and the frequency F is 360/P, i.e., 3.0. 
     In FIG. 9, a wave pattern  38  with four lobes  56  is shown with a period P of 90 degrees and a frequency of 4.0. The maximum positive and negative amplitudes  72 ,  74  are shown. 
     FIG. 10 depicts another exemplary cutting element interface  36  with a four-lobed wave pattern  38 . In this embodiment, the amplitudes  72 ,  74  of wave pattern  38  are much reduced, i.e., about one-half the amplitudes of FIG.  9 . In addition, a second wave pattern  38 A, smaller than wave pattern  38 , is positioned generally concentric to wave pattern  38 . The second wave pattern  38 A has a base radius  70 A which is smaller than radius  70 , and has amplitudes  72 A and  74 A which in this case are slightly smaller than amplitudes  72  and  74 . In FIG. 10A, the ridges  50  and  50 A both extend from the table  30  into grooves  60  in the substrate  40 . As shown in FIG. 10B, one or both of the ridge patterns  50 ,  50 A may alternatively extend from the substrate  40  into the table  30 . This is true regardless of how many wave patterns  38  are formed in the interface  36 . 
     FIG. 11 illustrates an exemplary substrate  40  with three interfacial ridge/groove patterns  38 ,  38 A and  38 B arranged concentrically. Each pattern  38 ,  38 A and  38 B has five outwardly extending lobes  56 ,  56 A and  56 B of differing amplitude. Theoretically, a large number of patterns may be formed on an interface  36 , depending upon ridge width. From a practical standpoint, however, the useful number of patterns on a given interface may be one to about twelve, depending on the size of the cutting element  20 . Generally, the amplitudes  72 ,  74  must be reduced to permit higher numbers of concentric wave patterns  38 . As alluded to previously, and as shown in the upper portion of FIG. 11, the interfacial ridge/groove patterns may be segmented or intermittent in physical structure, although substantially continuous in terms of the patterns themselves. It is contemplated that a given pattern will be either structurally continuous or structurally segmented as a whole (i.e., about its entire length), although such is not required. 
     In FIG. 12, an exemplary substrate  40  is shown with two wave patterns  38  and  38 A in generally concentric relationship. Each wave pattern  38 ,  38 A has six lobes or arches  56 ,  56 A, respectively. 
     In another embodiment of the invention shown in FIG. 13, each of two wave patterns  38  and  38 A comprises a series of semicircles  80 ,  80 A having their loci  82 ,  82 A arranged in regular order in a circle  90 ,  90 A about axis  28 . Each semicircle  80 ,  80 A is an outwardly extending lobe or arch  56 ,  56 A. The semicircles  80 ,  80 A have their ends  84 ,  84 A smoothly joined by connecting portions  86 ,  86 A, shown here as arcuate members which themselves form small inwardly directed lobes or arches  58 ,  58 A. The convex face  88 ,  88 A of each semicircle  80 ,  80 A is outwardly directed to face and distribute high loads which impinge on the table  30  and along interface  36  during drilling. 
     In a further embodiment depicted in FIG. 14, a wave pattern  38  comprises a series of outwardly directed hemielliptical lobes or arches  56 . The number of lobes may vary from 2 to about 30. Preferably, the number of lobes varies from 3 to about 24, and in a more preferred embodiment, the number may be from 4 to about 20. The lobes  56  are joined by connecting portions  86  which may be straight or arcuate. In this example, the connecting portions  86  are radial about central axis  28 . 
     As shown in each of the figures, the entire wave pattern(s)  38  is (are) within the periphery  46  of the interface  36 , so that a plurality of outwardly extending arches or lobes  56  and intermediate inwardly extending arches or lobes  58  together form a continuous curve at the interface  36 . Preferably, the curve is sinuous, i.e., has no sharp corners. The series of outwardly extending arches  56  is primarily responsible for the increased resistance to fracture, and the inwardly extending arches  58  provide additional strength and integrity to the interface  36 . 
     The cutting element  20  of the present invention, having an interfacial wave pattern  38  of outwardly extending lobes or arches  56 , has superior resistance to fracture and spalling of the table  30 , delamination thereof from substrate  40  and overall failure of the cutting element  20  itself. In addition, the presence of the interfacial pattern  38  completely around the periphery  46  of the interface  36  of the cutting element  20  enables the cutting element to be removed, rotated about its central axis  28  and remounted in position on the drill bit to expose fresh superabrasive material to engage the formation when an initial cutting edge of the cutting element becomes worn. 
     The foregoing description mentions, by way of example only, some of the variables which fall within the purview of the invention, including the number of wave patterns, numbers, sizes, spacing and shapes of lobes, and the like, and is not limiting to the scope of the invention. 
     This invention may be embodied in many forms without departing from the spirit of essential characteristics of the invention. The embodiments as described herein are therefore intended to be only illustrative and not restrictive, and the scope of the invention is defined by the appended claims rather than the preceding description, and all variations that fall within the metes and bounds of the subject matter claimed, or are equivalent thereto, are therefore intended to be embraced by the claims which follow: