SUPERHARD CUTTER HAVING SHIELDED SUBSTRATE

Abstract

A cutter for use with a drill bit includes: a substrate for mounting in a pocket of the drill bit and made from a cermet material; a cutting table made from a polycrystalline superhard material and mounted to the substrate; and a shield disposed in an outer recess of the substrate adjacent to the cutting table, mounted to the substrate, extending from the cutting table along a partial length of the substrate, and made from a composite material comprising the polycrystalline superhard material and a ceramic.

Description

BACKGROUND OF THE DISCLOSURE

Field of the Disclosure

The present disclosure generally relates to a superhard cutter having a shielded substrate.

Description of the Related Art

U.S. Pat. No. 5,605,198 discloses a drill bit employing selective placement of cutting elements engineered to accommodate differing loads such as are experienced at different locations on the bit crown. A method of bit design and cutting element design to achieve optimal placement for maximum ROP and bit life of particularly suitable cutting elements for a given bit profile and design, as well as anticipated formation characteristics and other downhole parameters.

U.S. Pat. No. 5,875,862 discloses a composite body cutting instrument formed of a polycrystalline diamond layer sintered to a carbide substrate with a carbide/diamond transition layer. The transition layer is made by creating carbide projections perpendicular to the plane of the carbide substrate face in a random or nonlinear orientation. The transition layer manipulates residual stress caused by both thermal expansion and compressibility differences between the two materials and thus increases attachment strength between the diamond and carbide substrate by adjusting the pattern, density, height and width of the projections.

U.S. Pat. No. 6,068,071 discloses polycrystalline diamond cutter (PDC) designs which substantially improve the penetration rate of fixed cutter drill bits while simultaneously reducing the wear on the bit during drilling operations are disclosed. The designs are based upon the observation that: 1) the wear pattern of a PDC is roughly a conic section and is parallel to bit rotation, and 2) the cutting surface is perpendicular to the rotation of the bit. The PDC designs provide cutting action both perpendicular and parallel to the direction of bit rotation.

U.S. Pat. No. 6,401,845 discloses an improved cutting element for use with rotating downhole tools. More specifically, a compact cutter which includes unique configurations for the interface regions between the substrate the abrasive element to promote superior impact resistance and adhesion.

U.S. Pat. No. 8,727,043 discloses cutter assemblies including an outer support element and a cutting element disposed therein. The cutting element is immovably attached to the outer support element. Also provided are downhole tools incorporating such cutter assemblies and methods of making such downhole tools.

U.S. Pat. No. 8,727,046 discloses polycrystalline diamond compacts (“PDCs”) that are less susceptible to liquid metal embrittlement damage due to the use of at least one transition layer between a polycrystalline diamond (“PCD”) layer and a substrate. In an embodiment, a PDC includes a PCD layer, a cemented carbide substrate, and at least one transition layer bonded to the substrate and the PCD layer. The at least one transition layer is formulated with a coefficient of thermal expansion (“CTE”) that is less than a CTE of the substrate and greater than a CTE of the PCD layer. At least a portion of the PCD layer includes diamond grains defining interstitial regions and a metal-solvent catalyst occupying at least a portion of the interstitial regions. The diamond grains and the catalyst collectively exhibit a coercivity of about 115 Oersteds or more and a specific magnetic saturation of about 15 Gauss*cm³/grams or less.

U.S. Pat. No. 8,978,788 discloses a cutting element for use in a drill bit for drilling subterranean formations and including a cutting body having a substrate including a rear surface, an upper surface, and a peripheral side surface extending between the rear surface and the upper surface, and a superabrasive layer overlying the upper surface of the substrate. The cutting element further includes a sleeve surrounding the peripheral side surface of the cutting body and comprising a superabrasive layer bonded to an external surface of the sleeve.

SUMMARY OF THE DISCLOSURE

The present disclosure generally relates to a superhard cutter having a shielded substrate. In one embodiment, a cutter for use with a drill bit includes: a substrate for mounting in a pocket of the drill bit and made from a cermet material; a cutting table made from a polycrystalline superhard material and mounted to the substrate; and a shield disposed in an outer recess of the substrate adjacent to the cutting table, mounted to the substrate, extending from the cutting table along a partial length of the substrate, and made from a composite material comprising the polycrystalline superhard material and a ceramic.

In another embodiment, a method for manufacturing a superhard cutter includes: forming a cermet substrate having a recessed outer portion; loading superhard cutting table powder into an inner can; loading shield powder into the inner can, the shield powder comprising superhard material and a ceramic; inserting the recessed outer portion into the inner can; placing an outer can over the inner can; pressing the cans together, thereby forcing the shield powder into the recessed outer portion; sealing the cans, thereby forming a can assembly; and subjecting the can assembly to high pressure and high temperature, thereby forming the superhard cutter.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

FIGS. 1A and 1B illustrate manufacturing of a substrate, according to one embodiment of the present disclosure.

FIG. 2A illustrates cutting table powder loaded into an inner can for a high pressure and high temperature (HPHT) sintering operation. FIG. 2B illustrates shield powder loaded into the inner can. FIG. 2C illustrates the substrate loaded into the inner can and placement of an outer can. FIG. 2D illustrates compaction of the loaded cans.

FIG. 3 illustrates the HPHT sintering operation to from the superhard cutter having the shielded substrate.

FIG. 4A illustrates grinding of the cutter. FIG. 4B illustrates the superhard cutter having the shielded substrate. FIG. 4C illustrates leaching of the cutter. FIG. 4D illustrates brazing the leached cutter into a blade of a drill bit.

FIGS. 5A-5C illustrate alternative cutters having undulating shields, according to other embodiments of the present disclosure.

FIGS. 6A-6E illustrate alternative shaped cutters having shields, according to other embodiments of the present disclosure.

DETAILED DESCRIPTION

FIGS. 1A and 1B illustrate manufacturing of a substrate 1 (FIG. 2C), according to one embodiment of the present disclosure. A quantity of substrate powder 2 may be loaded into a chamber of a die 3d. The substrate powder 2p may be a hard material, such as a cermet. The cermet may be a cemented carbide, such as a group VIIIB metal-tungsten carbide. The group VIIIB metal may be cobalt. The die 3d may be fabricated with a precise inner surface forming the die chamber using a CAD design model (not shown). The precise inner surface may have a shape that is a negative of what will become the substrate 1.

The die 3d may be part of a forming press 3. Once the substrate powder 2p has been loaded into the die chamber, a plunger 3p may be inserted into the die chamber. The plunger 3p may be connected to a ram 3r. The ram 3r may be hydraulically powered 3h to drive the plunger into engagement with the substrate powder 2p, thereby forming a green compact 2c.

The green compact 2c may then be ejected from the die 3d and transported to a furnace 4 for sintering. The furnace 4 may include a housing 4h, a heating element 4e, a controller, such as programmable logic controller (PLC) 4c, a temperature sensor 4t, and a power supply (not shown). The furnace 4 may be preheated to a sintering temperature, such as a melting temperature of the metal component of the green compact 2c. The green compact 2c may be inserted into the furnace 4 and kept therein for a sintering time 4m. The furnace 4 may also be pressurized to a sintering pressure 4p by injection of gas, such as an inert gas. As the green compact 2c is heated by the furnace 4, the metal component of the green compact 2c may melt while the ceramic component thereof remains solid. During sintering, the green compact 2c may be consolidated into the coherent substrate 1.

FIG. 2A illustrates cutting table powder 5 loaded into an inner can 6n for a high pressure and high temperature (HPHT) sintering operation. The cutting table powder 5 may be a superhard material, such as monocrystalline diamond. The diamond may be synthetic. A quantity of the cutting table powder 5 may be poured into the inner can 6n. The inner can 6n may be made from a refractory metal and may have a cylindrical cavity formed therein for receiving the cutting table powder 5. A diameter of the cavity may correspond to a diameter of the substrate, such as being slightly greater than the substrate diameter.

FIG. 2B illustrates shield powder 7 loaded into the inner can 6n. The shield powder 7 may be a composite mixture of superhard material, such as monocrystalline diamond, and a ceramic. The ceramic may be the same ceramic as the ceramic member of the cermet substrate powder 2. The carbide may be tungsten carbide. The diamond may be synthetic. The composite mixture may include more superhard material than ceramic, such as greater than fifty percent by volume of superhard material, to ensure formation of polycrystalline superhard material during HPHT sintering. The amount of superhard material may range between seventy and ninety-five percent by volume. A quantity of the shield powder 7 may be poured into the cavity of the inner can 6n onto the cutting table powder 5.

Alternatively, the shield powder 7 may include a cermet instead of or in addition to the ceramic. The cermet may be a cemented carbide, such as a group VIIIB metal-tungsten carbide. The group VIIIB metal may be cobalt.

FIG. 2C illustrates the substrate 1 loaded into the inner can 6n and placement of an outer can 6o. The substrate 1 may have a cylindrical portion 1y and a truncated conical portion 1n. The conical portion 1n may converge from a junction of the two portions 1n,y to an end of the substrate 1. The conical portion 1n of the substrate 1 may be inserted into the cavity of the inner can 6n and into engagement with the shield powder 7 while the cylindrical portion 1y thereof may protrude from an end of the inner can. The outer can 6o may then placed over the inner can 6n. The outer can 6o may be made from a refractory metal and may have a cylindrical cavity formed therein for receiving the inner can 6n and the cylindrical portion 6y of the substrate 1.

FIG. 2D illustrates compaction of the loaded cans 6n,o. The loaded cans 6n,o may be inserted into a press (not shown). The outer can 6o may then be driven toward the inner can 6n, thereby forcing the shield powder 7 into an outer recess formed between the conical portion 1 n of the substrate 1 and a sidewall of the inner can 6n. The loaded cans 6n,o may then be sealed, thereby forming a can assembly 6.

Alternatively, the substrate 1 may be made into a cylindrical shape and the recess formed by a separate machining operation.

FIG. 3 illustrates the HPHT sintering operation to from the superhard cutter 16 having the shielded substrate. A plurality of can assemblies 6 may be assembled with a liner 8, a heating element 9, a pair of plugs 10, and a cylinder 11 to form a cell 12. The cell 12 may then be inserted into a HPHT press, such as a belt press 13, and the belt press operated to perform the HPHT sintering operation, thereby causing the metal component of the substrate 1 to melt and sweep into the shield powder 7 and cutting table powder 6. The molten metal may act as a catalyst for recrystallization of the superhard monocrystalline material into polycrystalline superhard material, thereby forming a coherent cutting table 14 (FIG. 4B) and a coherent shield 15, while bonding the cutting table, shield, and substrate 1 together to form the superhard cutter 16. A particle size of the polycrystalline superhard material in the shield 7 may be greater than twenty microns or greater than thirty microns.

Alternatively, a cubic press may be used to perform the HPHT sintering operation instead of the belt press 13.

FIG. 4A illustrates grinding of the cutter 16. FIG. 4B illustrates the superhard cutter 16 having the shielded substrate. The cutter 16 may be removed from the cell 12 and inserted into a cylindrical grinder 17 to remove excess material, polish surfaces thereof, and form a chamfer 14c into an outer edge of the cutting table 14 and a chamfer 1c into an outer edge of the substrate 1.

The shield 15 may occupy the outer recess formed in a side of the substrate 1 by the conical portion 1n, thereby restoring a cylindrical shape to the cutter 16. The cutting table 14 may be mounted to the substrate 1 and may be mounted to the shield 15 at a first interface 18f. The shield 15 may have a triangular, such as right-triangular, cross-section and a hypotenuse of the cross-section may form a second interface 18s with the substrate 1 at which the shield is mounted thereto. The second interface 18s may be inclined relative to a side of the cylindrical portion 1y at an inclination angle 19. The shield 15 may extend from the cutting table along the substrate 1 for a length ranging between one-fifth and two-thirds of a length of the substrate. The shield 15 may have a maximum thickness at the first interface 18f with the cutting table and the thickness thereof may decrease along the substrate as the shield extends away from the cutting table towards an end 15e thereof distal from the first interface.

Alternatively, the shield 15 may have a rectangular or trapezoidal cross-section. Alternatively, instead of being annular, the recess of the substrate 1 and the shield 15 may only extend partially around the substrate 1, such as at least around one-eighth of a side thereof.

FIG. 4C illustrates leaching of the cutter 16. A portion of the substrate 1 and a portion of the shield 15 adjacent to the distal end 15e thereof may be masked 20. The cutting table 14 and an unmasked portion of the shield 15 (adjacent to the first interface 18f) may then be submerged into a bath of acid 21, such as Aqua regia, and left therein for a soaking time. The acid 21 may leach at least a substantial portion of the catalyst from a portion of the cutting table 14 adjacent to a working face 14w and side 14s thereof. Since the shield 15 has a greater thickness adjacent to the cutting table 14, the unmasked portion of the shield may protect the substrate from the acid 21 and gain the benefit of increased thermal stability from being leached.

Alternatively, the outer recess may be formed in a substrate of a prior art cutter adjacent to the cutting table thereof. The recessed cutter may then be inserted into the inner can 6n. The shield powder 7 may then be loaded into the inner can 6n having the recessed cutter therein. The outer can 6o may then be placed over the inner can 6n and the can assembly 6n,o sealed. The can assembly 6n,o may be placed into the HPHT press and the cutter re-sintered. The shielded cutter may then ground and leached (re-leached if the shear cutter had been previously leached).

FIG. 4D illustrates brazing the leached cutter 16 into a blade 22 of a drill bit 23. The brazing operation may be manual or automated. A plurality of the cutters 16 may be mounted into pockets formed in a leading edge of the blade 22. Each cutter 16 may be delivered to the pocket by an articulator 24. A brazing material 25 may be applied to an interface formed between the pocket and the cutter 16 using an applicator 26. As the brazing material 25 is being applied to the interface, the articulator 24 may rotate the cutter 16 relative to the pocket to distribute the brazing material 25 throughout the interface. A heater (not shown) may then be operated to melt the brazing material 25. Cooling and solidification of the brazing material 25 may mount the cutter 16 to the blade 22. The brazing operation may then be repeated for mounting additional cutters into additional pockets formed along the leading edge of the blade 22. The pocket may be inclined relative to a bottom face of the blade adjacent thereto by a back-rake angle. The inclination angle 19 may correspond to the back rake angle such that the second interface 18s may be parallel or substantially parallel to rock engaged by the cutter during drilling. Each of the inclination angle 19 and the back rake angle may range between ten and thirty degrees.

The drill bit 23 may include a bit body 26, a shank 27, a cutting face, and a gage section 28. A lower portion of the bit body 26 adjacent to the cutting face may be made from a composite material, such as a ceramic and/or cermet body powder infiltrated by a metallic binder and an upper portion of the bit body adjacent to the shank 27 may be made from a softer material than the composite material of the upper portion, such as a metal or alloy shoulder powder infiltrated by the metallic binder. The bit body 26 may be mounted to the shank 27 during molding thereof. The shank 27 may be tubular and made from a metal or alloy, such as steel, and have a coupling, such as a threaded pin, formed at an upper end thereof for connection of the drill bit 23 to a drill collar (not shown). The shank 27 may have a flow bore formed therethrough and the flow bore may extend into the bit body 26 to a plenum thereof. The cutting face may form a lower end of the drill bit 23 and the gage section 28 may form an outer portion thereof.

Alternatively, the bit body 26 may be metallic, such as being made from steel, and may be hardfaced. The metallic bit body may be connected to a modified shank by threaded couplings and then secured by a weld or the metallic bit body may be monoblock having an integral body and shank.

The cutting face may include one or more primary blades (not shown), one or more secondary blades 22, fluid courses formed between the blades, and the cutters 16. The cutting face may have one or more sections, such as an inner cone, an outer shoulder, and an intermediate nose between the cone and the shoulder sections. The blades 22 may be disposed around the cutting face and each blade may be formed during molding of the bit body 24 and may protrude from a bottom of the bit body. The primary blades and the secondary blades 22 may be arranged about the cutting face in an alternating fashion. The primary blades may each extend from a center of the cutting face, across the cone and nose sections, along the shoulder section, and to the gage section 28. The secondary blades 22 may each extend from a periphery of the cone section, across the nose section, along the shoulder section, and to the gage section 28. Each blade 22 may extend generally radially across the cone (primary only) and nose sections with a slight spiral curvature and along the shoulder section generally longitudinally with a slight helical curvature. Each blade 22 may be made from the same material as the bit body 24. The cutters 16 may be mounted along leading edges of the blades 22.

One or more ports 29 may be formed in the bit body 24 and each port may extend from the plenum and through the bottom of the bit body to discharge drilling fluid (not shown) along the fluid courses. Once the cutters 16 have been mounted to the respective blades 22, a nozzle (not shown) may be inserted into the each port 29 and mounted to the bit body 24, such as by screwing the nozzle therein.

The gage section 28 may define a gage diameter of the drill bit 23. The gage section 28 may include a plurality of gage pads, such as one gage pad for each blade 22 and junk slots formed between the gage pads. The junk slots may be in fluid communication with the fluid courses formed between the blades 22. The gage pads may be disposed around the gage section 28 and each pad may be formed during molding of the bit body 24 and may protrude from the outer portion of the bit body. Each gage pad may be made from the same material as the bit body 24 and each gage pad may be formed integrally with a respective blade 22. Each gage pad may extend upward from a shoulder portion of the respective blade 22 to an exposed outer surface of the shank 27.

In use (not shown), the drill bit 23 may be assembled with one or more drill collars, such as by threaded couplings, thereby forming a bottomhole assembly (BHA). The BHA may be connected to a bottom of a pipe string, such as drill pipe or coiled tubing, thereby forming a drill string. The BHA may further include a steering tool, such as a bent sub or rotary steering tool, for drilling a deviated portion of the wellbore. The pipe string may be used to deploy the BHA into the wellbore. The drill bit 23 may be rotated, such as by rotation of the drill string from a rig (not shown) and/or by a drilling motor (not shown) of the BHA, while drilling fluid, such as mud, may be pumped down the drill string. A portion of the weight of the drill string may be set on the drill bit 23. The drilling fluid may be discharged by the nozzles 12n and carry cuttings up an annulus formed between the drill string and the wellbore and/or between the drill string and a casing string and/or liner string.

Advantageously, the shield 15 may protect the substrate 1 during drilling to prevent an undercut from being formed therein. The undercut could otherwise compromise structural support of the cutting table 14, thereby leading to premature failure of the cutter.

FIGS. 5A-5C illustrate alternative cutters 30, 31 having undulating shields 32, 33, according to other embodiments of the present disclosure. A second cutter 30 may include the cutting table 14, the shield 32, and a substrate 34. The substrate 34 and shield 32 may be similar to the substrate 1 and shield 15 except for having an undulating interface therebetween instead of the constant interface 18s. The undulation of the interface may be sinusoidal alternating between a long portion and a short portion. During brazing of the second cutter 30, the long portion may be oriented to be adjacent to the rock, thereby providing increased protection for the substrate 34 while the short portion may provide additional exposure of the substrate to the brazing material, thereby increasing bonding area of the substrate and the brazing material.

A third cutter 31 may include the cutting table 14, the shield 33, and a substrate 35. The substrate 35 and shield 33 may be similar to the substrate 1 and shield 15 except for having an undulating interface therebetween instead of the constant interface 18s. The undulation of the interface may be parabolic having a long portion straddled by a pair of short portions. During brazing of the third cutter 31, the long portion may be oriented to be adjacent to the rock, thereby providing increased protection for the substrate 35 while the short portions may provide additional exposure of the substrate to the brazing material, thereby increasing bonding area of the substrate and the brazing material.

FIGS. 6A-6E illustrate alternative shaped cutters 36-39 having shields 40-43, according to other embodiments of the present disclosure. A first shaped cutter 36 may include a non-planar cutting table 44, the shield 40, and a substrate 45. The substrate 45 and shield 40 may be similar to the substrate 1 and shield 15. The cutting table 44 may be made from a superhard material, such as polycrystalline diamond. A working face of the cutting table 44 may have a plurality of recessed bases 46a-c, a protruding center section 47, a plurality of protruding ribs 48a-c, and an outer edge. Each base 46a-c may be planar and perpendicular to a longitudinal axis of the first shaped cutter 36. The bases 46a-c may be located between adjacent ribs 48a-c and may each extend inward from a side of the cutting table 44. The outer edge may extend around the working face and may have constant geometry. The outer edge may include a chamfer located adjacent to the side and a round located adjacent to the bases 46a-c and ribs 48a-c.

Each rib 48a-c may extend radially outward from the center section 47 to the side of the cutting table 44. Each rib 48a-c may be spaced circumferentially around the working face at regular intervals, such as at one-hundred twenty degree intervals. Each rib 48a-c may have a triangular profile formed by a pair of curved transition surfaces, a pair of linearly inclined side surfaces, and a round ridge. Each transition surface may extend from a respective base 46a-c to a respective side surface. Each ridge may connect opposing ends of the respective side surfaces. An elevation of each ridge may be constant (shown), declining toward the center section, or inclining toward the center section.

An elevation of each ridge may range between twenty percent and seventy-five percent of a thickness of the cutting table 44. A width of each rib 48a-c may range between twenty and sixty percent of a diameter of the cutting table 44. A radial length of each rib 48a-c from the side to the center section 47 may range between fifteen and forty-five percent of the diameter of the cutting table 44. An inclination of each side surface relative to the respective base 46a-c may range between fifteen and fifty degrees. A radius of curvature of each ridge may range between one-eighth and five millimeters or may range between one-quarter and one millimeter.

The center section 47 may have a plurality of curved transition surfaces, a plurality of linearly inclined side surfaces, and a plurality of round edges. Each set of the features may connect respective features of one rib 18a-c to respective features of an adjacent rib along an arcuate path. The elevation of the edges may be equal to the elevation of the ridges. The center section 47 may further have a plateau formed between the edges. The plateau may have a slight dip formed therein.

The substrate 45 may have a keyway 49 formed therein for each ridge of the respective rib 48a-c. Each keyway 49 may be located at the edge of the substrate 45 and may extend from the pocket end thereof along a portion of a side thereof. Each keyway 49 may be angularly offset from the associated ridge, such as being located opposite therefrom. Each pocket of the drill bit may have a key (not shown) formed therein for properly orienting the respective first shaped cutter 36. During brazing of each first shaped cutter 36 into the respective pocket, one of the keyways 49 may be aligned with the key and engaged therewith to obtain the proper orientation. The proper orientation may be that the operative ridge is perpendicular to a projection (not shown) of the leading edge of the respective blade 22 through the pocket.

A second shaped cutter 37 may include a concave cutting table 50, the shield 41, and a substrate 51. The cutting table 50 may be made from a superhard material, such as polycrystalline diamond. The substrate 51 and shield 41 may be similar to the substrate 1 and shield 15. A working face of the cutting table 50 may have an outer chamfered edge, a planar rim adjacent to the chamfered edge, a conical surface adjacent to the rim, and a central crater adjacent to the conical surface. The thickness of the cutting table 50 may be a minimum at the crater and increase outwardly therefrom until reaching a maximum at the rim. A depth of the concavity may range between four percent and eighteen percent of a diameter of the second shaped cutter 37. The substrate 51 may have a plurality of keyways (not shown) formed therein and spaced therearound. Each keyway may be located at the edge of the substrate 51 and may extend from the pocket end thereof along a portion of a side thereof.

Alternatively, sides of the cutting table 50 and substrate 51 may each be elliptical instead of circular. The keyways may then be used to orient the major axis of the cutter to the proper orientation.

A third shaped cutter 38 may include a non-planar cutting table 52, the shield 42, and a substrate 53. The cutting table 52 may be made from a superhard material, such as polycrystalline diamond. The substrate 53 and shield 42 may be similar to the substrate 1 and shield 15. The cutting table 52 may be made from a superhard material, such as polycrystalline diamond. A working face of the cutting table 52 may have a plurality of recessed bases, a plurality of protruding ribs, and an outer chamfered edge. The bases may be located between adjacent ribs and may each extend inward from a side of the cutting table 52. Each rib may extend radially outward from a center of the cutting table 52 to the side. Each rib may be spaced circumferentially around the working face at regular intervals, such as at one-hundred twenty degree intervals. Each rib may have a ridge 54a-c and a pair of bevels each extending from the ridge to an adjacent base.

The substrate 53 may have the keyway 49 formed therein for each ridge 54a-c. Each keyway 49 may be located at the edge of the substrate 53 and may extend from the pocket end thereof along a portion of a side thereof. Each keyway 49 may be angularly offset from the associated ridge 54a-c, such as being located opposite therefrom.

A fourth shaped cutter 39 may include a non-planar cutting table 55, the shield 43, and a substrate 56. The cutting table 55 may be made from a superhard material, such as polycrystalline diamond. The substrate 56 and shield 43 may be similar to the substrate 1 and shield 15. The cutting table 55 may be made from a superhard material, such as polycrystalline diamond. A working face of the cutting table 55 may have an outer edge and a ridge 57 protruding a height above the substrate and at least one recessed region extending laterally away from the ridge. The ridge 57 may be centrally located in the working face and extend across the working face. The presence of the ridge 57 may result in the outer edge undulating with peaks and valleys. The portion of the ridge 57 adjacent to the outer edge may be an operative portion. Since the ridge 57 extends across the working surface, the ridge may have two operative portions. The working face may further include a pair of recessed regions continuously decreasing in height in a direction away from the ridge 57 to the outer edge that is the valley of the undulation thereof. The ridge 57 and recessed regions may impart a parabolic cylinder shape to the working face. The outer edge of the cutting table 55 may be chamfered (not shown).

The substrate 56 may include a keyway 49 for each operative portion of the ridge 57. Each keyway 49 may be located at the edge of the substrate 56 and may extend from the pocket end thereof along a portion of a side thereof. Each keyway 49 may be angularly offset from the associated operative portion, such as being located opposite therefrom.

Alternatively, any of the shaped cutters may have a knob for orientation thereof instead of the keyway 49. The knob mounted to a back face of the respective substrate. The knob may be formed separately from the rest of the respective shaped cutter and then mounted to the substrate thereof, such as by brazing. The knob may be angularly offset from the respective cutting feature, such as being located opposite therefrom (one-hundred eighty degrees therefrom). The knob may be hemi-spherical and have a diameter ranging between twenty-five and forty-five percent of a diameter of the back face of the substrate. Instead of a key, the drill bit may have a dimple formed in the cutter pocket thereof for mating with the knob, thereby ensuring that the respective shaped cutter has been properly oriented to the operative position. The knob may be made from the same material as the substrate or a different material than the substrate, such as a metal or alloy, such as steel. Alternatively, the knob may be formed integrally with the respective substrate.

Alternatively, either orienting profile (the keyway 49 or the knob) may be used to orient either alternative cutter 30,31. Alternatively, any of the shaped cutters 36-39 may have either of the undulating shields 32,33 instead of their respective shields 40-43 and the long portion(s) thereof may be aligned with the respective cutting feature(s) thereof.

While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope of the invention is determined by the claims that follow.

Claims

1. A cutter for use with a drill bit, comprising:

a substrate for mounting in a pocket of the drill bit and made from a cermet material;

a cutting table made from a polycrystalline superhard material and mounted to the substrate; and

a shield disposed in an outer recess of the substrate adjacent to the cutting table, mounted to the substrate, extending from the cutting table along a partial length of the substrate, and made from a composite material comprising the polycrystalline superhard material and a ceramic.

2. The cutter of claim 1, wherein an amount of superhard material in the composite material ranges between seventy and ninety-five percent by volume.

3. The cutter of claim 1, wherein the shield and the outer recess extend at least around one-eighth of a side of the substrate.

4. The cutter of claim 3, wherein the shield and the outer recess surround the substrate.

5. The cutter of claim 1, wherein the cermet material comprises the ceramic and a metal binder.

6. The cutter of claim 1, wherein the partial length ranges between one-fifth and two-thirds of a length of the substrate.

7. The cutter of claim 1, wherein the shield has a maximum thickness at an interface with the cutting table and the thickness thereof decreases along the substrate as the shield extends away from the cutting table.

8. The bit of claim 1, wherein an interface between the shield and the substrate is inclined at an angle relative to a side of the substrate

9. A bit for drilling a wellbore, comprising:

a shank having a coupling formed at an upper end thereof;

a body mounted to a lower end of the shank; and

a cutting face forming a lower end of the bit and comprising: a blade protruding from the body; and the cutter of claim 8, wherein: the substrate is mounted in a pocket formed in the blade at a back rake angle, and the inclination angle corresponds to the back rake angle such that the interface is parallel or substantially parallel to rock engaged by the cutter during drilling.

10. The cutter of claim 1, wherein a portion of the cutting table adjacent to a working face thereof and a portion of the shield adjacent to the cutting table are at least substantially free of catalyst.

11. The cutter of claim 1, wherein an interface between the shield and the substrate is undulating.

12. The cutter of claim 1, wherein the cutting table has a non-planar working face with a cutting feature.

13. The bit of claim 12, wherein the cutting feature is at least a portion of a protruding ridge.

14. The bit of claim 12, wherein:

the cutting feature is a protruding ridge, and

the working face has a plurality of protruding ridges spaced therearound.

15. The bit of claim 12, wherein:

the working face is concave, and

the cutting feature is an axis of the cutting table.

16. The cutter of claim 12, wherein an interface between the shield and the substrate is undulating and a long portion of the undulation is aligned with the cutting feature.

17. A method for manufacturing a superhard cutter, comprising:

forming a cermet substrate having a recessed outer portion;

loading superhard cutting table powder into an inner can;

loading shield powder into the inner can, the shield powder comprising superhard material and a ceramic;

inserting the recessed outer portion into the inner can;

placing an outer can over the inner can;

pressing the cans together, thereby forcing the shield powder into the recessed outer portion;

sealing the cans, thereby forming a can assembly; and

subjecting the can assembly to high pressure and high temperature, thereby forming the superhard cutter.