Superabrasive cutting element

Information

  • Patent Grant
  • 6488106
  • Patent Number
    6,488,106
  • Date Filed
    Monday, February 5, 2001
    23 years ago
  • Date Issued
    Tuesday, December 3, 2002
    22 years ago
Abstract
A cutting element for an earth boring bit comprises a cutting compact of a superabrasive material layer bonded to a supporting substrate. The superabrasive material layer has a pattern of radially extending ribs, the ribs extending from the peripheral surface of the layer, and a second pattern of circular ribs radially spaced from the peripheral surface and intersecting the first pattern of radially extending ribs. The supporting substrate comprises a first pattern of radially extending grooves for mating with the first pattern of radially extending ribs. In addition, the supporting substrate comprises a second pattern of circular grooves for mating with the first pattern of circular ribs. The interface between the substrate and the superabrasive material has a dome-shaped configuration.
Description




TECHNICAL FIELD OF THE INVENTION




This invention relates to a cutting element for an earth boring bit, and more particularly to a cutting element having improved stress distribution between a substrate and a superabrasive cutting compact.




BACKGROUND OF THE INVENTION




Cutting compacts used as cutting elements in rotary drill bit construction typically comprise a layer of synthetic diamonds, conventionally in the form of polycrystalline diamond. Polycrystalline diamond compact cutting elements, commonly known as PDC's, have been commercially available for many years. Although there has been some use of PDC's as a self-supporting layer, the more recent utilization of the polycrystalline diamond compact is in the form a substantially planar diamond layer bonded during formation to a supporting substrate.




Previous uses of the PDC have demonstrated that these compacts are resistant to abrasion and erosion, although there are several identified disadvantages. polycrystalline diamond and tungsten carbide, main components of a PDC, are brittle materials that easily fracture on impact. Another recognized disadvantage of the PDC is the different coefficient of thermal expansion between tungsten carbide and polycrystalline diamond. As a result of this different coefficient of thermal expansion, residual stresses have been identified and are a result of the greater contraction of tungsten carbide over synthetic diamond during a cooling phase. This thermally induced stress between the various components of the PDC results in a reduction in the bond strength between the two components.




During use of a PDC, it has been observed that impact forces relieve the residual sheer stresses resulting in fractures in the compact. The result of this fracturing is that the diamond layer spalls and/or delaminates resulting in a separation and loss of the diamond layer resulting in a failure of the PDC.




Heretofore, a common problem with cutting elements of superabrasive compacts bonded to a substrate is spalling and delamination of the superabrasive layer from the substrate. Spalling and delamination result from subjecting the cutting element to extreme temperatures and heavy stress load fluctuation when a drill bit is in use down a bore hole. During operation at extremely high temperatures, thermally induced stresses have been identified at the interface between the superabrasive cutting compact and the supporting substrate, the magnitude of the stresses being a function of the disparity in the thermal expansion coefficients of adjacent materials.




There are numerous patents granted directed to various attempts made to limit the effects of thermal induced stress by modifying the geometry of the interface between the diamond and the tungsten carbide. As illustrated by a review of earlier issued patents, the interface modification many times replaces a planar interface with an irregular, non-planar interface geometry. Many of the early attempts to solve the stress related disadvantages of the PDC claim as an advantage the redistribution of residual stresses. A redistribution of residual stresses does allow an increase in the diamond thickness thereby resulting in an increase in bit life. The non-linear planar interface between the diamond and the tungsten carbide substrate results in an enhanced mechanical interlocking and improved stability and performance of the cutting element and therefore translates into longer bit life.




While cutting elements utilizing the superabrasive cutting compacts employed in rotary drill bits for earth boring have achieved major advances in obtainable rate of penetration at economically viable costs, the interface between the superabrasive cutting compact and the supporting substrate leaves something to be desired. As a result, considerable activity has been directed toward attempts to improve the bond between the superabrasive cutting compact and the supporting substrate by configuring the rear face of the cutting compact so as to provide a degree of mechanical interlocking between the cutting compact and the supporting substrate. Several United States patents directed to solutions for this problem have been granted including U.S. Pat. Nos. 5,617,928; 4,784,023 and 5,351,772, to identify only a few, describe various techniques for improving the bond between the superabrasive cutting compact and the supporting substrate.




The present invention relates to improvements in the interface between the superabrasive cutting compact and the supporting substrate.




SUMMARY OF THE INVENTION




According to the invention there is provided a superabrasive cutting compact integral with a substrate to form a cutting element. The cutting compact comprises a pattern of radially extending ribs where the ribs extend from in proximity to a peripheral edge of the compact. A circular shaped pattern of circular ribs radially spaced from the peripheral edge of the compact intersect the pattern of radially extending ribs. The substrate supporting the cutting compact comprises a pattern of radially extending grooves for mating with the pattern of radially extending ribs. The substrate also comprises a pattern of circular grooves for mating with the pattern of circular ribs of the cutting compact.




The ribs of the cutting compact and the grooves of the substrate have an expanding width dimension from one circumferential segment of a peripheral edge of the cutting element to the opposite circumferential segment. Further, in accordance with this alternate embodiment, the circular pattern of ribs and the circular pattern of grooves comprise segments of concentric circles spaced from the peripheral edge. The ribs and grooves can have different widths and depths.




In another embodiment of the invention, the substrate surface comprises a convex surface and the mating surface of the cutting compact comprises a concave surface.




Alternatively, the cutting element comprises a cylinder with the cutting compact fixed perpendicular to the axis of the cylinder or the superabrasive cutting compact is affixed directly to a stud insert for use with a rotary drill bit.




A technical advantage of the present invention is a cutting element having improved stress distribution between a superabrasive material cutting compact and a supporting substrate resulting in enhanced performance of a cutting element as part of a rotary drill bit. An additional technical advantage of the present invention is providing an improved bond between the superabrasive material cutting compact and the substrate surface affixed thereto.











BRIEF DESCRIPTION OF THE DRAWINGS





FIGS. 1A and 1B

are side elevational views of a cutting element in accordance with the present invention supported on an insert typically utilized in a rotary bit;





FIG. 2

is a side pictorial illustration of a typical cutter assembly incorporating a right cylinder cutting element according to the invention;





FIG. 3

is also a pictorial illustration of a cutter assembly incorporating the cutting element of

FIG. 1B

;





FIG. 4

is a pictorial illustration, partially in section, illustrating the interface layout of radial and concentric grooves between a substrate material and a compact of super hard material;





FIG. 5

is a side elevational view of the cutting element of

FIG. 4

illustrating the depth of the hard facing material in one embodiment of the present invention;





FIG. 6

is a side elevational view of a cutting element in accordance with the present invention for a second depth of super hard material in accordance with the present invention;





FIG. 7

is a section view of the substrate component for the cutting elements of

FIGS. 5 and 6

;





FIG. 8

is a plot of the potential stress on the outer diameter of the diamond compact for the cutting element of

FIG. 5

;





FIG. 9

is a plot of compressive stresses for the cutting element of

FIG. 5

;





FIG. 10

is a plot of tensile stress for the thicker diamond compact of the cutting element of

FIG. 6

;





FIG. 11

is a plot of compressive stress in the diamond compact of the interface for the cutting element as illustrated in

FIG. 6

;





FIG. 12

is a top view of the substrate for forming a plurality of cutting elements in accordance with an alternative embodiment of the invention illustrating the interface layout of radial and concentric grooves;





FIG. 13

is a section view of the substrate component of

FIG. 12

;





FIG. 14

is an exploded view of the superabrasive material cutting compact and the substrate of a cutting element in accordance with the alternate embodiment of the invention;





FIG. 15A

is a view of the surface interface illustrating radial ribs and segments of concentric circular ribs for the cutting compact; and





FIG. 15B

is a view of the substrate for the cutting element of

FIG. 14

showing the interface between the cutting compact and the substrate comprising radial grooves and segments of concentric circle grooves.











DETAILED DESCRIPTION OF THE INVENTION




Referring to

FIGS. 1A and 1B

, there is illustrated a bit insert


10


, that is, an insert for a rotary drag bit, comprises a cylindrical body


12


and a disk shaped cutting element


14


bonded thereto. The bit insert


10


forms a part of a cutter assembly of a rotary drag bit and in accordance with conventional manufacturing techniques the cylindrical body


12


is positioned in a socket in the body of the rotary drag bit. The cutting element


14


has a circular tablet-like configuration comprising a planar compact layer


16


of superabrasive material, usually polycrystalline diamond, bonded to a substrate


18


normally of cemented tungsten carbide. The mating surfaces of the diamond compact layer


16


and the supporting substrate


18


are bonded together typically by braze bonding or LS bonding. The diamond compact layer


16


can be obtained by HPHT process from synthetic diamond powder.




Referring to

FIGS. 2 and 3

, the cutting element


10


of

FIGS. 1A and 1B

may be attached to various types of carrier elements or structure supports


40


and


42


.

FIG. 2

is an illustration of a stud cutter


40


with a right cylinder cutting element


44


attached thereto in a conventional socket. The cutting element


44


is oriented such that the diamond compact layer


16


is positioned such that the face thereof engages the rock formation to be cut.

FIG. 3

illustrates the bit insert


10


of

FIG. 1B

inserted into a socket such as by brazing. Again, the diamond compact layer


16


is positioned to engage the rock formation to be cut.




One form of the disk shaped cutting element


14


for a drill bit in accordance with the present invention is illustrated in FIG.


4


. In this embodiment, the cutting element


14


is in the form of a circular tablet


46


and comprises a diamond compact layer


48


of super hard material, such as PDC, bonded in a high pressure, high temperature press to a supporting substrate


50


of less hard material, such as cemented tungsten carbide. However, other suitable materials may be used for the diamond compact layer


48


and the supporting substrate


50


. The methods of forming such cutting elements are well known and no further description is deemed necessary.




As illustrated in

FIG. 4

, the supporting substrate


50


is preformed with radially extending grooves


52


having a first end and a center disk


54


and a second end extending to the periphery


56


of the substrate


50


. Further, the substrate


50


includes concentric circular grooves


58


, four concentric circular grooves illustrated in

FIG. 4

with the inner circular groove


58


at the center disk


54


and the remaining circular disks spaced therefrom. As illustrated, the radially extending grooves


52


are equally dimensioned along the length thereof. However, it is within the scope of the invention to include radially extending grooves having expanded groove width along the length thereof. Also as illustrated in

FIG. 4

, the concentric circular grooves


58


are all of the same dimension. However, it is within the scope of the invention that the radially extending grooves


52


and concentric circular grooves


58


may have different dimensions in width and depth.




Referring to

FIG. 7

, the supporting substrate


50


has a convex surface configuration and the mating surface of the superabrasive material


48


has a concave surface configuration. The dome-shaped interface, by virtue of its geometry, increases the volume of super hard material available for abrasive formation cutting. In addition, the dome shaped interface, in combination with the radially extending grooves


52


and the concentric circle grooves


58


, minimizes spalling and delamination of the cutting element. The dome-shaped interface provides improvement in spalling and delamination as a result of reduction in sheer stress and compressive stress as applied to the interface during use of the cutting element. Better control over sheer stress and compressive stress is also achieved by variations in the width and depth of the radially extending grooves and the concentric circular grooves. Additionally, the dome shaped interface allows a thick super hard layer to be provided toward the perimeter of the element, thereby increasing durability of the element during cutting of a formation.




Referring to

FIGS. 5 and 6

, there is illustrated two embodiments of the present invention with the dome-shaped interface of FIG.


7


and the radially extending grooves


52


and concentric circle grooves


58


as illustrated in FIG.


4


. In the embodiment of

FIG. 5

, the planar compact layer


16


has a thickness of 0.080 inches (2 millimeters) and in the embodiment of

FIG. 6

the planar compact layer


16


has a thickness of 0.140 inches (3.5 millimeters).




With reference to

FIGS. 4

,


5


,


6


and


7


, the dome-shaped interface with the radially extending grooves


52


and the concentric circular grooves


58


minimize tensile stresses in the diamond. These stresses are caused by differences in coefficients of thermal expansion between the diamond compact and the tungsten carbide substrate. This type of stress is identified in the literature including earlier granted patents as residual stress. It is these residual stresses that can lead to stress fractures exhibited as spalling and microchipping in the area of the cutting face and perimeter of the diamond compact. A cutting element having a flat interface between the diamond compact (layer


16


) and the substrate exhibits area of high stress just above the interface in the diamond compact. This is where a cutter element with a flat interface is most likely to spall or delaminate.




However, an interface between the diamond compact (layer


16


) and the substrate in accordance with the present invention such as illustrated in

FIGS. 4 through 7

reduces the tensile stress, thereby reducing the potential for spalling and delamination.




Referring to

FIGS. 8 and 9

, there is plotted the tensile stress and compressive stress for the cutting element of

FIG. 5

having a diamond compact (layer


16


) 0.080 inches (2 millimeters) thick. The interface of the cutting element has a dome-shaped configuration wherein the dome has a radius of 1.90 inches (48 millimeters). The dome-shaped interface reduces the high tensile stress that is normally observable on the outer diameter of the diamond compact approximately 0.030 inches above the interface. As illustrated in

FIG. 8

, the maximum tensile stress for the tested specimen was 45,000 psi.




Referring to

FIG. 9

, the cutting element of

FIG. 5

exhibits a large region of compressive stress. These compressive stresses reduce the tendency of the cutter to spall and help deflect cracks that may cause massive fractures in the diamond compact. The minimum compressive stress for the cutting element of

FIG. 5

is 30,000 psi.




Referring to

FIGS. 10 and 11

, there is illustrated tensile test measurements and compressive stress measurements for the cutting element of

FIG. 6

having a diamond compact (layer


16


) of 0.140 inches (3.5 millimeters) thickness. Again, the interface between the diamond compact and the substrate has a dome-shaped configuration wherein the radius of the dome is 1.0 inches (25 millimeters). This interface has more of a dome shape than the interface of

FIG. 5

to accommodate the thicker diamond compact. As illustrated in

FIG. 10

the maximum tensile stress is below 40,000 psi.




Referring to

FIG. 11

, the cutting element of

FIG. 6

has a large region of compressive stress. The compressive stress in the diamond compact (layer


16


) of the cutting element of

FIG. 6

is higher than the compressive stress measurements for the cutting element of

FIG. 5

wherein the diamond compact (layer


16


) had a thickness of 0.080 inches (2 millimeters). However, the maximum compressive stress on the top surface of the cutting element of

FIG. 6

is less than the cutting element of FIG.


5


. This is due to the volume of diamond material used in the diamond compact of FIG.


6


. As illustrated in

FIG. 11

, the minimum compressive stress was less than 10,000 psi.




Finite Element Analysis (FEA) was utilized for measuring the principal stress in the cutting element of

FIGS. 5 and 6

. The results indicate a reduction of residual tensile stresses in the superabrasive diamond compact over a compact having a planar interface between the diamond and the supporting substrate.




Referring to

FIG. 12

, there is illustrated a top view of another embodiment comprising a substrate component


20


typically manufactured from cemented tungsten carbide and as illustrated is in the form of a cylinder. The substrate component


20


is preformed with radially extending grooves


22


and concentric circular grooves


24


. The substrate


20


is typically formed by a molding process using conventional molding techniques.




As illustrated in

FIG. 13

, a compact layer of superabrasive material, such as polycrystalline diamond, is applied to the patterned surface of the substrate component


20


such that the superabrasive material fills the radially extending grooves


22


and the concentric circular grooves


24


. The assembly is then placed in a high pressure, high temperature press and is subjected to high temperatures and pressures until the superabrasive layer


26


bonds to the substrate component


20


.




Upon completion of the bonding of the superabrasive layer


16


to the substrate component


20


, a number of cutting elements


28


are cut from the substrate component. For example, as illustrated in

FIG. 12

, four cutting elements


28


are cut from the substrate component


20


. This cutting produces a number of similar cutting elements


28


.




Referring to FIG.


14


and

FIGS. 15A and 15B

, there is illustrated a typical interface layout between the superabrasive compact layer


16


and the supporting substrate


18


for a cutting element


28


. The cutting element


28


as illustrated in

FIGS. 14

,


15


A and


15


B comprises the superabrasive layer


16


bonded to the substrate


18


. The interface between the superabrasive layer


16


and the supporting substrate


18


comprises a pattern of radially extending ribs


32


on the superabrasive layer


16


mating with radially extending grooves


22


on the substrate


18


as best illustrated in

FIGS. 15A and 15B

. In addition, the superabrasive layer


16


includes segments of concentric circular ribs


30


mating with segments of concentric circular grooves


24


as part of the substrate


18


. The radially extending ribs and grooves and the segments of concentric circular ribs and grooves intersect to form an interface providing improved stress distribution between the substrate and the superabrasive material layer not previously achievable in the art of cutting compacts.




Also with reference to

FIGS. 13 and 14

, the patterned surface of the substrate component


20


has a convex surface configuration and the mating surface of the superabrasive material


16


has a concave surface configuration. Thus, each of the cutting elements


28


has a curved interface between the superabrasive material layer


16


and the supporting substrate


18


. This curved surface interface provides a material layer having a thickness that increases smoothly from one circumferential segment of the peripheral surface


34


to the cutting edge


36


of the peripheral surface


34


.




Referring to

FIG. 12

, the concentric grooves


24


may be of equal widths or of different widths and depths. In the case of different groove widths and depths, the width increases from the innermost circular groove to the circular groove closest to the cutting edge


36


. Similarly, the radial grooves


22


are narrower towards that segment of the peripheral surface


34


most removed from the cutting edge


36


. That is, the radial grooves


24


as illustrated in

FIG. 12

increase in width and depth from the center of the substrate component


20


.




The interface layout and the overall shapes of the cutting elements illustrated and described are by way of example only, and it will be appreciated that the interface layout according to the invention may be applied to any shape or size and form of cutting element.




Although the present invention has been described in connection with several embodiments, it will be appreciated by those skilled in the art that modifications, substitutions and additions may be made without departing from the scope of the invention as defined in the claims.



Claims
  • 1. A cutting element for an earth boring bit wherein the cutting element comprises a cutting edge of a peripheral surface, comprising:a superabrasive material cutting compact having a first pattern of a plurality of radially extending ribs, the ribs extending from a center to the peripheral surface of the compact, and a second pattern of a plurality of circular ribs radially spaced from the peripheral surface and intersecting the first pattern of radially extending ribs; and a substrate supporting the cutting compact, the substrate comprising a first pattern of a plurality of radially extending grooves for mating with the first pattern of a plurality of radially extending ribs, and a second pattern of a plurality of circular grooves for mating with the second pattern of a plurality of circular ribs.
  • 2. The cutting element for an earth boring bit as in claim 1, wherein the first pattern of radially extending ribs and the first pattern of radially extending grooves comprises a width dimension that changes in the radial direction.
  • 3. The cutting element for an earth boring bit as in claim 2, wherein the width dimension of the first pattern of ribs and the first pattern of grooves increases in the radial direction from the center toward the peripheral surface.
  • 4. The cutting element for an earth boring bit as in claim 1, wherein the thickness of the cutting compact increases to a maximum toward the peripheral surface.
  • 5. The cutting element for an earth boring bit as in claim 4, wherein the thickness of the cutting compact varies as a concave surface having a maximum dimension toward the cutting edge.
  • 6. The cutting element for an earth boring bit as in claim 1, wherein the second pattern of a plurality of circular ribs and the second pattern of a plurality of circular grooves comprise mating segments of concentric circles.
  • 7. A cutting element for an earth boring bit, wherein the cutting element comprises a peripheral surface having a cutting edge, comprising:a diamond cutting compact layer having a fan shaped pattern of a plurality of ribs, the ribs extending from one part of the peripheral surface to a second part of the peripheral surface of the compact, and a concentric circle pattern of a plurality of circular ribs radially spaced from the peripheral surface and intersecting the pattern of the radially extending ribs; and a substrate supporting the cutting compact, the substrate comprising a fan shaped pattern of a plurality of grooves for mating with the fan shaped pattern of the plurality of ribs, and a concentric circle pattern of a plurality of circular grooves for mating with the circular pattern of a plurality of circular ribs.
  • 8. The cutting element for an earth boring bit as in claim 7, wherein the fan shaped pattern of ribs and the fan shaped pattern of grooves comprise a pattern of expanding width ribs and mating grooves.
  • 9. The cutting element for an earth boring bit as in claim 8, wherein the concentric circle pattern of ribs and the concentric circular pattern of grooves comprise segments of concentric circles.
  • 10. The cutting element for an earth boring bit as in claim 7, wherein the thickness of the cutting compact increases to a maximum toward the cutting edge.
  • 11. The cutting element for an earth boring bit as in claim 10, wherein the thickness of the cutting compact varies as a segment of a concave surface increasing to a maximum toward the cutting edge.
  • 12. A cutting element for an earth boring bit, comprising:a cutting compact having a cutting edge at a peripheral surface; and a substrate supporting the cutting compact at an interface therebetween, wherein the interface between the cutting compact and the substrate comprises a pattern of a plurality of radially extending ribs mating with a pattern of a plurality of radially extending grooves, the ribs extending from a center of the interface to the peripheral surface of the compact, and a pattern of a plurality of circular ribs radially spaced from the peripheral surface and mating with a pattern of a plurality of circular grooves.
  • 13. The cutting element for an earth boring bit as in claim 12, wherein the interface has a concave surface having a maximum dimension toward the cutting edge.
  • 14. The cutting element for an earth boring bit as in claim 12, wherein the plurality of circular ribs and circular grooves comprise segments of concentric circles.
  • 15. The cutting element for an earth boring bit as in claim 12, wherein the plurality of circular ribs and circular grooves comprises concentric circles intersecting the pattern of a plurality of radially extending ribs and radially extending grooves.
  • 16. A cutting element for an earth boring bit, comprising:a cutting compact having a cutting edge of a peripheral surface; and a substrate supporting the cutting compact at an interface therebetween, wherein the interface between the cutting compact and the substrate comprises a fan shaped pattern of a plurality of ribs mating with a fan shaped pattern of a plurality of grooves, the ribs and grooves extending from one part of the interface to a second part of the interface, and a concentric circle pattern of a plurality of circular ribs mating with a concentric circle pattern of a plurality of circular grooves spaced from the peripheral surface of the cutting compact.
  • 17. The cutting element for an earth boring bit as in claim 16, wherein the interface has a concave surface having a maximum dimension toward the cutting edge.
  • 18. The cutting element for an earth boring bit as in claim 16, wherein the plurality of circular ribs and circular grooves comprise segments of concentric circles.
  • 19. The cutting element for an earth boring bit as in claim 16, wherein the plurality of circular ribs and circular grooves comprises concentric circles intersecting the fan shaped pattern of a plurality of radially extending ribs and radially extending grooves.
  • 20. The cutting element for an earth boring bit as in claim 16 wherein the concentric circle pattern of ribs and the concentric circle pattern of grooves comprise segments of concentric circles.
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