GB2316698A

GB2316698A - PDC compact for cutter element having contoured substrate interface

Info

Publication number: GB2316698A
Application number: GB9717980A
Authority: GB
Inventors: Graham Mensa-Wilmot; Carl W Keith; Tommy G Ray
Original assignee: Smith International Inc
Current assignee: Smith International Inc
Priority date: 1996-08-26
Filing date: 1997-08-22
Publication date: 1998-03-04
Anticipated expiration: 2017-08-22
Also published as: GB2316698B; GB9717980D0

Abstract

A compact for a cutter element wherein substrate/diamond layer interface is contoured according to a mathematical description. Features making up the interface may include spiral, circle (110) or wave (122) configurations and may vary in amplitude and frequency. A plurality or combination of such features may combine to make up the interface, in a regular or irregular manner.

Description

PDC CUTTER ELEMENT HAVING IMPROVED SUBSTRATE CONFIGURATION TECHNICAL FIELD OF ThE INVENTION fli: pDsent invention relates generally to cutting elements for usc in earth-boring drill biz and, more specifically. to a means for increasing the life of cutting elements that comprise a layer of superhard material, such as diamond affixed to a substrate. Still more particularly, the present invention relates to a polycrystalline diamond compact comprising a supporting substrate and a diamond layer supported thereon, wherein the supporting substrate includes a plurality of projections having defined frequencies, amplitudes and/or configurations.

Tn a typical drilling operation a drill hit is rotstal while be no need into a soil or rock formation. The formation is cut by cutting elements on the drill bit and these cuttings are flushed from the borehole by the circulation of drilling fluid toward the top of the borehole. The drilling fluid is delivered to the drill bit through a passage in the drill stem and is ejected outwardly through nozzles in the cutting face of the drill bit The ejected drilling fluid is directed outwardly through the nozzles at high speed to aid in cutting. and to flush the cuttings and cool thc cuttcr clemcats.

Conventional cutting elements typically comprise a stud or cylinder having a supporting surface at one end, and a cutting disk mounted on the supporting surface. The disk comprises a substrate having one surface bonded to the supporting surface and a second surface that carries a diamond substance such as a layer of polycrystalline diamond or thennally stable diamond. The stud and substrate are normally formed of a hard material such as tungsten carbide (WC).

Alternatively, thc diamond layer can be directly applied to LIi carbide stud or cylinder. The techniques for constructing polycrystalline diamond (PDC) cutting elements are generally well known will not be described in detail. They can be summarized as follows: a carbide substrate is fonned having a desired surface configuration on each of its first and second surfaces the substrate is placed in a mold with a superhard material, such as diamond powder, and subjected to high temperature, high pressure pressing, resulting in the formation ot a diamond layer bonded to the substrate sisce; and the substrate is braze-bonded to the stud or cylinder. At presut, the interface between the superhard cutting layer and the substrate is typically planar, although some non-planar diamond/substrate interfaces have been disclosed As used herein, the term "superhard" means a material having a hardness of at least 2,700 Knoop (kg(mm2). PCD grades typically have a hardness range of about 5,000-8,000 Knoop (kg/mm2) while PCBN grades typically have hardncsscs that fall within the range of about 2,7003,500 Knoop Wmm2). By way of comparison, the hardest commonly used grade of cemented tungsten carbide has a hardnessofabout 1475 Knoop (kglmm2).

Although cutting elements having this configuration have significantly expanded the scope of formations for which drilling with diamond bits is economically viable, the interface between the substrate and the diamond layer wnlinues ro be a limiting for, as it is prone to failure, resulting in delamination, spalling andlor chipping of the diamond layer. Theft re several possible explanations for the failure of this interface. One explanation is that the interface between the diamond and the substrate is subject to high residual stresses resulting from the manufacturing processes of the cutting element. Specifically, because manufacturing occurs at elated temperatses and pressures, the different properties of the diamond and substate material, irtcluting thcir differing coefficients of thermal expansion LtdL in thermally-induced stresses. In addition, finite element analysis (FEA) has demonstrated that during cutting high stresses are localized in both the outer diamond layer and at the tungsten carbide interface Finally, the cutting elements are subjected to extremes of temperature and heavy loads when the drill bit is in use. It has been found that during drilling, shock waves may rebound from the internal planar interface berweenthe two layers and interact destructively. All of these phenomena are deleterious to the life of the cutting element during drilling operations, as the stresses, when augmented by stresses attributable to the loading of the tutting element by the formation, may cause spalling, fracture and even delamination of the diamond layer from the substrate. In addition to the foregoing, state of the art cutting elements often lack sufficient diamond volume to cut highly abrasive formations, as the tickness ofthe diamond layer is limited by the resulting high residual stresses and the difficulty of bonding a relatively thick diamond layer to a planar substrate.

Hence, it is desired to provide a new and improved preform cutting element that overcomes or reduces the spalling and delamination problems referred to above.

SUMMARY OF THE INVENTION The present invention provides a supporting substrate for a PDC compact wherein the substrate is provided with an irregular or asymmetric amplitude and/or frequency modulated surface to which the abrasive layer is affixed. The ubs.trate suce may comprise various inegular features, including but not limited to irregular undulations, rings, spirals, or protrusions having various other shapes andlor combinations of shapes. The surface features may vary in height (amplitude), displacement (wavelength) or both. In one embodiment, the amplitude and/or wavelength vary according to defined mathematical equations.

One embodiment of the present invention comprises an asymmetrical substrate surface in which irrt2ular undulations increase in height and/or displacement adjacent one side of the surface and decrease in height andlor spacing adjacent the opposite side of the surface. This produces a dual purpose substrate, whose orientation can be adjusted to maximize performance.

Another embodiment of the present invention comprises a subste having a substantially planar interface from which a plurality of protuberances extend into the diamond table. The preferred protuberances decrease in amplitude toward the center of the interface 3nd this decrease accordingto a prescribed mathematical relationship.

BRIEF DESCRIPTION OF THE DRAWINGS For an introduction to the detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings wherein: Figure 1 is a side elevation of a cutting element according to the present invention; Figures 2A and 2B are cross-sectional and perspective views respectively. of a first embodiment of the present substrate layer, Figures 3A and 3B are crossectiaiaI and perspective views, respectively, of a second embodiment of the present substrate layer; Figures 4A and 4B are cross-sectional and perspective views, respectively, ot a third embodimentof the pest substrate layer, Figures 5A and SB are cross-sectional and perspective views, respectively, of a fouilh embodiment of the present substrate layer; Figures 6A and 6B are cross-sectional and perspective views, respectively, of a fifth embodiment of the present substrate layer; Figures 7A and 'I are cross-sectional and perspective views, xspectively, of a sixth embodiment of the present substrate layer; Figures 8, 9 and 10 are cross-sectional views of alternative embodiments of the surface devices of the present invention; Figures 11A and 1 IB are cross-sectional and perspective views, respectively, of a seventh embodiment of the present substrate layer; Figuxes 12A and 12D are cross-sectional and perspective views, ztiv, uf an eighth embodiment of the present substrate layer, Figures 13A and 13B are cross-sectional and perspective views, respectively, of a ninth embodiment of the present substrate layer Figures 14A and 14B are cross-sectional and perspective views, respectively, of a tenth embodiment of the present substrate layer; Figures 15A and 151 are cross-sectional and perspective views, respectively, of a eleventh embodiment of the present substrate layer; Figures 16A and 16B are cross-sectional and perspective views, respectively, of a twelfth embodimentofthe present substrate layer, and Figures 1 7A and 1 7B are cross-sectional and perspective views, respectively, of a thirteenth embodiment of the present substrate laycr.

DETAILED DESCRIPTION OF THE INVENTION Referring initially to Figure lA, a curling elernent 10 in accordance with the present invention comprises a stud 12 and a disc-shaped cutting compact 14 bonded thereto. As is known in the art, cutting compact 14 comprises a diamond layer 16 affixed to the surface 17 of supporting substrate 18. The present invention is directed to provi ding an improved stress distribution between substrate 18 and diamond layer 16, which enhances performance. Alternatively, cutting element could comprise a cylinder 13 with the cutting compact affixed pe-icularlyto the axis of the cylinder, as shown in Figure 1B, or the diamond compact could be affixed directly to the stud, as shown in Figures 1C and D. In any event, the present invention is directed to providing an improved bond between the diamond compact and the surface on which it is mounted. Thus, while the invention is described hereinafter in terms of the surface 17 of a supporting substate 18, it will be understood that it is equally applicable to all of the configurations shown in Figures lA-D, as well as to otherapplicationsin which diamond compacts and inserts are used.

Referring now to Figures 2A and 2B, one embodiment of the present substrate 20 includes a plurality of undulatioas 22 extending across the face of the subtrate and defining a plurality of ridges 23 and valleys 24. A centerline 26 (shown in phantom) is defined as passing through the center point of each successive ridge face, with the center point being equidistant from the peak and nadir of that face. The height h of a given ridge 23 is defined as the shortest distance from the peak of that ridge to the centerline 26. The depth d of a given valley 24 Is defined as the distance from the nadir of that valley to the certerime 26. Ibe amplitude a of a given ridgetvalley combination is defined as the height of a given ridge plus the depth of an adjacent valley. The waveleo @ of a given ridgelvalley combination is defined as the lateral distance from the peak of a given ridge to the peak of an adjacent ridge.

In accordance with the principles of the present invention, the surface of substrate 20 is configured such that at least one of either the amplitude a or the wavelength w is non-constant across the face of substrate 20. More specifically, the amplitude may be increasing while the wavclcngth is constant or creasing, or the amplitude may be decreasing while the wavelength is constant or increasing. It will be understood that no particular orientation of the subsutesurice is specified, as the principles of the present invention describe relative magnitudes. Thaws, undulations that appear to be "increasing" as drawn may be described as "decreasing" when viewed from another perspective, and vice versa According to the emlsodirnellt shown in Figure 3A and 313, the amplitude and wavelength of the undulations are both greatest at the same side ofthe substrate. In this manner, an asymmetric substrate is formed, having large undulations at one edge, which taper off to much smaller undulations, if any, at the opposite edge. It is believed that the asymmetric compact formed using such an asymmetric substrate will be advantageous. in that it is capable of providing a dual purpose cutting surface in a single insert Thus, the insert can be oriented to provide the optimal balance of abrasion resistance and impact resistance, depenslin. on the aXlication for which it is to be used.

Alternatively, the present invention also includes substrate surfaces wherein the relationship of adjacent pairs of ridges varies or is irregular, rather than constant. That is, as shown in Figures 4A and 4B, the amplitude and wavelength of the undulations 22 can vary simultaneously, independently and without pattem. It will be either understood that the undulations 22 described above can be orientcd so as to lic cithcr across the cutting path or parallel to it without departing from the spirit of the present invention. Likewise, the average amplitude of the undulations can be largest in one portion of the substrate surface, while the average wavelength of the undulations is largest in another portion of the substrate surface. In addition, while the undulations shown in Figures 4A and 4B are substantially straight, it will be understood that the principles of the present invention could be carried our using crooked or wavy undulations.

Still another alternative embodiment of the present invention is shown in Figures SA smd SB, wherein a single ridge 52 and valley 54 define a spiral 53 in which the amplitude of ridge 52 and 52 valley 54 is greatest at the perimeter of the substrate and decreases as the radius of the ridge decreases. Alternatively,as shown in Figures 6A and 6B, the amplitude of ridge 62 and valley 64 can be smallest adjacent the perimeter of the substrate and increase toward the center.

Still another embodiment of the present invention, chn in Figures 7A and 7B, cncompasses a substrate 70 having a contoured surface 71 that includes a plurality of variously sized projections 72 and indentations 74. These serve the same purpose as undulations 22 and valleys 24, namely a reduction in stress concentration and corresponding increase in the ability of the diamond layer to remain affixed to the substrate. It is preferred that projections 72 and indiiuzis 74 vary in height and diameter, including either regular or isTEular variations in at least one ofthese parameters.

In the embodiments described above, undulations 22 are depicted as generally sinusoidal.

The principles of the present invention can also be applied to substrate configurations wherein the surface projections have other shapes. Some alternative shapes are shown in Figures 8 and 9, although the alternative shapes depicted therein are not intended to be an exhaustive list ot possible alternatives. Figure 8 shows 2 pair of ridges 82 and an intervening valley 24, in which the ridges 89 and the valley 84 each include a single inflection or shoulder 86. As used herein, the term shoulder means an inflection at which the absolute value of the slope of the line defining the face decreases and then increases again . Figure 9 shows a pair of ridges 92 and an intervening valley 94, in which the ridges 92 and the valley 94 each include a pair of inflections or shoulders 96. The waveforms shown in Figures 8 and 9, as well as variations thereof, can behave either constant or varying amplitudes and/or frequal es.

As shown in Figure 10, each ridge 101 may include more than one maximum 102 and each valley 103 may include more than one minimum 104. For ease of reference hereinafter, rna:niia 103 and minima 104 are refined to as points of zero slope. In addition, the foregoing waveforms can be combined or superimposed in a variety of ways.

In still another embodiment, thc surfacc of the substrate may includesome combination of the foregoing devices. By way of example only, Figures 1 1A and 11 B show a surface comprising a ring 110 swtoundinga plurality of undulations 122. It will be understood that the reverse is also applicable, in that the surface can include one or more undulations surrounding one or more rings or other devices. It will further be understood that undulations 122, and any other surface device described herein, need not be straight or linear, but may be curvilinear or wavy, or have any other desired configuration.

Likewise, as shown in Figures 12A and 12B, either the substrate itself or the centerline of the features can define a convex or concave shape. If the substrate surface is convex (domed), the diamond layer may be thickest around the perimeterofthe compact, while if the substrate surface is concave (bowl-shaped), the diamond layer will be thickest at the center of the compact It will be understood that neither the concave nor the convex embodimcnt nccd be synurictrical, i.e the center of the domeorhoilowcan be elsewhere than at the center of the substrate surface.

In stil anotherembodiinent,shown in Figures 13A and 13B, the surface can be divided into a plurality of sectors 130, 132 in which the average amplitude of the surface features decreases in opposite dircLion. Alternatively or in addition, the frequencyand/or amplitudeof the features can vary from sector to sector. Furthennore. features that are shown decreasing could increase and features shown to be increasing could decrease in the same manner.

Referring now to Figures 14A and 1 4B another embodiment of the present invention has one or more surface features 140 that each describe a closed loop 142 on the surface. The closed loops 142 can be nested and generally circular, as shown, or not. As best shown in Figure 14A, surface features 140 comprise undulations that comprise both ridges 144 and valleys 146, to which any of the variations described above apply, including, but not limited to, variations in amplitude, variations in wavelength, and the addition of shoulders.

In the alternative, the surface may include either ridges or valleys. These embodiments, shown in Figures 15A-B and 16A-B, are referred to hereinafter as "ridged" and "grooved" surfaces respcctivcly. In each case, approximately one-half of ic wavcrunu is eliminated, leaving only ridges 150 extending into the diamond layer (Figures 15A and 1 SB) or grooves 160 extending into the substrate layer (Figures 16A and 16B). Between the ridges or grooves are relatively flat intervening areas 152, 162. By "reiatively flat" it is meant that the amplitude of any surface modulation in intervening areas 152, 162 is significantly less than the amplitude of ridges 150 or grooves 160. For example, intervening areas 152 and 162 can be slightly convex, flat, slightly concave or wslvy As discussed above with respect to earlier embodiments. the amplitude of ridges 150 and grooves 160 can vary randomly across the surface, increase generally toward the center of the surface (as shown in Figures 15A and 15B), or decrease generally toward the center of the surface (as shown in Figures 16A and 16B). Likewise ridges 172 and grooves 174 can both be used on a single substrate, as shown in Figures 1 7A and 1 7B.

According to another cmbodimcnt, the substrate/diamond interface daibed above includes protuberances whose amplitudes and position relative to the center of the interface, or displacement, are governed by defined mathematical relationships These mathematical relationships can apply over the entire substate interface or over a portion of the interface defined within a restricted region. For example, the amplitudes of the protuberances can be governed by defined mathematical relationshps so that they vary consistently and predictably. An example of an equation that can he used tn define the amplitudes of the protuberancesis Ai=K@ri@A@ where Ao is the amplitude at the commencement of the pattern, Aj is the amplitude at a distance ri from the position of A, n is a real number, and K, is a relational constant for the amplitude function. In this equation the position of at corresponds to t0.

Alteretively,the displacement of cach protubcrancc or feature can be govcmed by defined mathematical relationships such that: Di = K@ rim Do where D0 is the displacement at the commencement of the pattern, D; is the displacement at a distance ri from the position of D, m is a real nurnber, and Kd is a relational constant for the displacement purstiorL In this equation, the position of Do corresponds to @@.

If the foregoing mathematical equations are applied over less than all of the sllrfce of the interface, the balance of the surface can be planar or irregular. The portion of the surface that is defined by the foregoing equations is preferably dependent on the type of protuberance and mathematical relationships describing the amplitude and or displacement. In addition, the surface features described above with respect to Figures 2-17B can be configured so as to be defined by either or both of the foregoing mathematical expression relating to amplitude and displacement.

Likewise, the undulations or protuberances on a first portion of the surface can above consistently varying amplitudes that vary according to a different from consistently varying amplitudes on another portion of the surface, with each set of varying amplitudes being governed by a separate mathematical equation of the form given above. For cxample, in one embodiment, A1; = ri@@k@@A1.0 and A2 = r,n2icN Similarly, portion of said surface which can also be defined by mathematical equations of the for= D11 = r@@k@@andD@ and D,= rEca @@@k2D@@.

While various prefened embodiments of the invention have been shown and described, modifications thereof can be rnade by one skilled in the art without departing from the spirit and teachings ofthe invention. For example, the insert and/or substrate need not be round, but may be ovoid, truncated, or any of several other known cutter shapes.

Claims

What is claimed is: 1. A compact for use on a cutting element fur an earth boring bit, comprising: a cemcnted carbide substrate having a supporting surface; and a superhard layer bonded to said supporting surface. thereby forming a superhard/substrate interfi including a plurality of protuberances having amplitudes and displacements that are governed by defined mathematical relationships.
2. The compact according to claim I wherein said superhard layer is selected from the group consisting of diamond, PCBN and materials having hardness of at least 2,700 Knoop.
3. The compact according to claim 1 wherein said interface comprises features having varying amplitudes, said amplitudes varying consistently according to defined mathematical relationships of the form A@ = K@ rip where A0 is the amplitude at the commencement of the pattern, A; is the amplitude at a distance r, from the position of A0, n is a real number, and Us is a relational constant for the amplitude function.
4. The compact according to claim 1 wherein said interface comprises features having varying displacements, said displacements varying consistently according to defined mathematical relationships of the form D; ~ Kd r,"D, where D, is the displacement at the commencement of the pattern, Di is the displacement at a distance ri from the position of D0, m is a real number, and K@ is a relational constant for the displacement function.
5. The compact according to claim 1 wherein said interface comprises features having varying amplitudes and displacements, said amplitudes varying consistently according to defined mathematical relationships of the form Aj = K@@A@, where A0 is the amplitude at the commencement of the pattern, 4 is the amplitude at a distance r ftom the position of A, n is a real number, and K, is a relational constant for the amplitude function and said displacements verying consistcntly according to defined mathematical relationships of the form Di = Kd r-D where Do is the displacement at the commencement of the pattern, D; is the displacement at a distance ri from the position of D, m is real number, and Kd is a relational constant for the displacement function.
6. The compact according to claim 5 wherein said features include at least two nonintersecting ridges.
7. A compact for use on a cutting element for an earth boring bit, comprising: a substrate having a supporting surface; a superhard layer bonded to said supporting surface, thereby forming a superhard/substrateintezce, said interface being irregular and comprising surface features having varying amplitudes and frequencies, said features include at least two nonintersecting ridgcs; wherein said interface further includes at least one arcuate ridge.
8. The compact accordingto claim 7 wherein said arcuate ridge is circular.
9. The compact according to claim 6 wherein said ridges are substantially straigh
10. The compact according to claim 6 wherein said ridges are not straight.
11. The compact according to claim 6 wherein said ridges are wavy.
12. The compact according to claim 5 wherein l interface.. is substantially planar over a portionofits area
13. The compact according to claim 12 wherein said planar portion of its area comprises at least 20%.
14. A compact fbr use on a cutting element for wi klrLh boring bit, comprising: a substrate having a supporting surface; and an abrasive layer bonded to said supporting surface, thereby forming an abrasiveIsubstrrteintce; wherein said abrasive/substrateinterface includes a spiral shaped ridge, each portion of said ridge projecting from a common defining surface, said ridge being continuous.
15. The compact according to claim 14 wherein said ridge increases in amplitude toward the center of the supporting su:rttce.
16. A compact for use on a cutting element for an earth boring bit, comprising: a substrate having a supporting sluice; and an abrasive layer bonded to said supporting surface, thereby forming an abrasive/substrate interface, said interface including a spiral shapcd ridge, said ridge decreaning in amplitude toward the center of the supporting surface.
17. A cutting element for an earth boring bit, comprising: a stud having first and second ends, said first end being adapted for attachment to a the bit; a substrate having first and second substantially opposed surfaces, said first surface affixed to said second stud end; ne1 an abrasive cutting layer affixed to said second substrate surface; wherein said second substrate surface includes a plurality of protuberances having amplitudesand displacementsthat are governed by defined mathematicalrelationships.
18. The compact according to claim 17 wherein aid interface is substancially planar over a portion of its area
19. The cutting element according to claim 17 wherein said second surface has at least one plane of symmetry.
20. The tihg eleme:rt according to claim 17 wherein said undulations are curvilinear
21. lhe cutting element according to claim 17 wherein said undulations have an average displacement on a first portion of said supporing surface that is greater than the average displacement on another portion of said surface.
22. The cutting element according to claim 17 wherein said undulations have an average amplitude on a first portion of said supporting surface that is greater than the average amplitude on another portion of said surface.
23. A cutting element for an earth boring bit, comprising: asubstratehavingasupportingsurface;and an abrasive layer bonded to said supporting surface, thereby forming an abrasive substate interface; wherein said abrasive/substrate interface includes a plurality of ridges and valleys wherein at least one of said ridges includes at least two faces and at least one shoulder.
24. The cutting, elements according to claim 23 wherein each ridge includes two shoulders.
25. The cutting element according to claim 24 wherein said shoulders are on the same face.
26. The cutting element according to claim 23 wherein said shoulders are on opposite fuzes of each ridge.
27. The cutting element according to claim 23 wht:rein said ridges are non-sinusoidal.
28. The cutting element according to claim 23 wherein the displacement of said ridges varies consistently and can be defined by a mathematical expression.
29. The cutting element according to claim 23 wherein the amplitude of said ridges varies consistently and can be defined by a mathematical expression.
30. A cutting element for an earth boring bit, comprising: a substrate having a supporting surface; and a superhard layer bonded to said supporting surface, thereby forming a superhard/substrateintface; wherein said interface includes a plurality of ridges and valleys wherein at least one of said ridges and said valleys includes at least two points of zero slope.
31. A compact fot use on a cutting element for an tarth boring bit, comprising: a substrate having a supporting surface; and an superhard layer bonded to said supporting surface; wherein said supporting surface includes a surface feature, said surface feature defining at least one closed loop.
32. The compact according to claim 31 wherein said superhard layer is selected from the group consisting of diamond, PCBN and materials having like hardness
33. The compact according to claim 31 wherein said supporting surface includes a plurality of said surface features.
34. The compact according to claim 33 wherein said surface features have varying amplitudes
35. The compact according to claim 33 wherein said surface features have varying frequencies.
36. Thc compact according to claim 33 whcrciu said surface features have varying amplitudes and frequencies.
37. The compact according to claim 33 wherein said closed loop surface features are generally circular.
38. The compact according to claim 37 wherein said closed loop surface features are nested
39. A compact for use on a cutting element for an earth boring bit, comprising: a substrate having a supporting stH ce; and an abrasive layer bonded to said supporting surface; wherein said supporting surface includes a plurality of generally circular ridges.
40. The compact according to claim 39 wherein said ridges increase in amplitude toward the center of the second surface.
41. The compact according to claim 39 whcrcin said ridgcs dccri:asc in amplitude toward the center ofthe second surface.
42. The compact according to claim 39 wherein said ridges define a plurality of nested closed loops.
43. The compact according to claim 39 wherein said ridges are separated by relatively flat areas.
44. The compact accordingto claim 39. further including at least one groove on said surface.
45. A compact for use on a cutting element for an earth boring bit, comprising: a substrate having a supporting surface; and an abrasive layer bonded to said supporting surface; wherein said supporting surface includes a plurality of generally circular grooves.
46. The compact according to claim 45 wherein said groves increase in ainplittd toward tbe center of the second surface.
47. The compact according to claim 45 wherein said grooves decrease in amplitude toward the center of the second surface.
48. The compact according to claim 45 wherein said grooves define a plurality of nested closed loops.
49. The compact according to claim 45 wherein said grooves are separated by relatively flat areas.
50. The compact according to claim 45, further including at least one ridge on said surface.
51. A cut:lng element for an earth boring bit, comprising: a stud having first and second ends, said first end being adapted for attachment to a bit; a substrate having first and second substantially opposed surfaces, said first surface affixed to said second stud end; and an abrasive cuffing layer affixed to said second substrate surface; wherein said second substrate surface includes a plurality of undulations having varying amplirudes, at least one of said undulations defining a generally circular closed loop.
52. The cutting element accordingto claim 51 wherein said undulations have varying frequencies.
53. The cutting element according to claim 51 wherein said undulations comprise a plurality of nested closed loops.