This disclosure relates generally to cutting elements for earth-boring tools, to earth-boring tools carrying such cutting elements, and to related methods. More specifically, disclosed embodiments relate to cutting elements for earth-boring tools that may better resist impact damage, induce beneficial stress states within the cutting elements, and improve cooling of the cutting elements.
Some earth-boring tools for forming boreholes in subterranean formations, such as, for example, fixed-cutter earth-boring rotary drill bits (also referred to as “drag bits”) and reamers, include cutting elements comprising superabrasive, conventionally polycrystalline diamond compact (PDC) cutting tables mounted to supporting substrates and secured to the rotationally leading portions of blades. The cutting elements are conventionally fixed in place, such as, for example, by brazing the cutting elements within pockets formed in the rotationally leading portions of the blades. Because formation material removal exposes the formation-engaging portions of the cutting tables to impacts against the subterranean formations, they may chip, which dulls the impacted portion of the cutting element or even spall, resulting in loss of substantial portions of the table. Continued use may wear away that portion of the cutting table entirely, leaving a completely dull surface that is ineffective at removing earth material.
In some embodiments, cutting elements for earth-boring tools may include a substrate and a polycrystalline, superabrasive material secured to an end of the substrate. The polycrystalline superabrasive material may include a first transition surface extending in a direction oblique to a central axis of the substrate, a second transition surface extending in a second direction oblique to the central axis, the second direction being different from the first direction, and a curved, stress-reduction feature located on the second transition surface.
In other embodiments, earth-boring tools may include a body and a cutting element secured to the body. The cutting element may include a substrate and a polycrystalline, superabrasive material secured to an end of the substrate. The polycrystalline superabrasive material may include a first transition surface extending in a direction oblique to a central axis of the substrate, a second transition surface extending in a second direction oblique to the central axis, the second direction being different from the first direction, and a curved, stress-reduction feature located on the second transition surface.
In still other embodiments, methods of making cutting elements for earth-boring tools may involve shaping a polycrystalline, superabrasive material to include: a first transition surface extending in a direction oblique to a central axis of the substrate; a second transition surface extending in a second direction oblique to the central axis, the second direction being different from the first direction; and a curved, stress-reduction feature located on the second transition surface. The polycrystalline, superabrasive material may be secured to a substrate.
While this disclosure concludes with claims particularly pointing out and distinctly claiming specific embodiments, various features and advantages of embodiments within the scope of this disclosure may be more readily ascertained from the following description when read in conjunction with the accompanying drawings, in which:
The illustrations presented in this disclosure are not meant to be actual views of any particular cutting element, earth-boring tool, or component thereof, but are merely idealized representations employed to describe illustrative embodiments. Thus, the drawings are not necessarily to scale.
Disclosed embodiments relate generally to cutting elements for earth-boring tools that may better resist impact damage, induce beneficial stress states within the cutting elements, and improve cooling of the cutting elements. More specifically, disclosed are embodiments of cutting elements that may include multiple transition surfaces proximate a periphery of the cutting elements, at least one curved, stress-reduction feature located on one or more of the transition surfaces, and an optional recess extending from a radially innermost transition surface back toward a substrate of the respective cutting element.
The term “earth-boring tool,” as used herein, means and includes any type of bit or tool used for drilling during the formation or enlargement of a wellbore in a subterranean formation. For example, earth-boring tools include fixed-cutter bits, roller cone bits, percussion bits, core bits, eccentric bits, bicenter bits, reamers, mills, drag bits, hybrid bits, and other drilling bits and tools known in the art.
As used herein, the term “superabrasive material” means and includes any material having a Knoop hardness value of about 3,000 Kgf/mm2 (29,420 MPa) or more. Superabrasive materials include, for example, diamond and cubic boron nitride. Superabrasive materials may also be characterized as “superhard” materials.
As used herein, the term “polycrystalline material” means and includes any structure comprising a plurality of grains (i.e., crystals) of material that are bonded directly together by inter-granular bonds. The crystal structures of the individual grains of the material may be randomly oriented in space within the polycrystalline material.
As used herein, the terms “inter-granular bond” and “interbonded” mean and include any direct atomic bond (e.g., covalent, metallic, etc.) between atoms in adjacent grains of superabrasive material.
The term “sintering” as used herein means temperature driven mass transport, which may include densification and/or coarsening of a particulate component. For example, sintering typically involves shrinkage and removal of at least some of the pores between the starting particles, accompanied by part shrinkage, combined with coalescence and bonding between adjacent particles.
As used herein, the term “tungsten carbide” means any material composition that contains chemical compounds of tungsten and carbon, such as, for example, WC, W2C, and combinations of WC and W2C. Tungsten carbide includes, for example, cast tungsten carbide, sintered tungsten carbide, and macrocrystalline tungsten carbide.
Referring to
The cutting elements 104 may be secured within pockets 118 formed in the blades 106. Nozzles 120 located in the junk slots 108 may direct drilling fluid circulating through the drill string toward the cutting elements 104 to cool the cutting elements 104 and remove cuttings of earth material. The cutting elements 104 may be positioned to contact, and remove, an underlying earth formation in response to rotation of the earth-boring tool 100 when weight is applied to the earth-boring tool 100. For example, cutting elements 104 in accordance with this disclosure may be primary or secondary cutting elements (i.e., may be the first or second surface to contact an underlying earth formation in a given cutting path), and may be located proximate the rotationally leading surface 122 of a respective blade 106 or may be secured to the respective blade 106 in a position rotationally trailing the rotationally leading surface 122.
The polycrystalline, superabrasive material 134 may include an interfacial surface 144 abutting, and secured to, the end surface 140 of the substrate 132. The polycrystalline, superabrasive material 134 may be generally disc-shaped, and may include a side surface 146 extending longitudinally from the interfacial surface 144 away from the substrate 132. The side surface 146 may be curved, and may be, for example, flush with the side surface 138 of the substrate 132.
The polycrystalline, superabrasive material 134 may include a first transition surface 148 extending from the side surface 146 away from the substrate 132. The first transition surface 148 may have a frustoconical shape, and may comprise what is often referred to in the art as a “chamfer” surface. The first transition surface 148 may extend away from the substrate 132 in a first direction oblique to the central axis 150 of the substrate 132. The first transition surface 148 may extend radially from the side surface 146 at the periphery of the polycrystalline, superabrasive material 134 inward toward the central axis 150. In some embodiments, the polycrystalline, superabrasive material 134 may lack the side surface 146, such that the first transition surface 148 may begin at an intersection (e.g., an edge) with the interfacial surface 144 located adjacent to the end surface 140 of the substrate 132.
The polycrystalline, superabrasive material 134 may further include a second transition surface 152 extending from the first transition surface 148 away from the substrate 132. The second transition surface 152 may extend away from the substrate 132 in a second direction oblique to the central axis 150 of the substrate 132. The second direction in which the second transition surface 152 extends may be different from the first direction in which the first transition surface 148 extends. The second transition surface 148 may extend radially from the first transition surface 148 at the radially innermost extent thereof inward toward the central axis 150. For example, the second transition surface 148 may extend radially inward more rapidly than the first transition surface 148.
In some embodiments, such as that shown in
By increasing the number of transition surfaces relative to a cutting element with a single chamfer, the cutting element 130 may increase the time over which an impulse resulting from contact with an earth formation may act on the cutting element. As a result, the cutting element 130 may reduce peak collision force, reducing impact and chip damage and increasing the useful life of the cutting element 130.
The cutting element 130 may further include a curved, stress-reduction feature 156 located on the second transition surface 152. The curved, stress-reduction feature 156 may be sized and shaped to induce a beneficial stress state within the polycrystalline, superabrasive material 134. More specifically, the curved-stress-reduction feature 156 may reduce the likelihood that tensile stresses will occur, and may reduce the magnitude of any tensile stresses that appear, in the polycrystalline, superabrasive material 134. As shown in
The second transition surface 152 may be a truncated dome shape in some embodiments, such as that shown in
As shown in
A frequency at which the bumps 164 may be positioned around the second transition surface 152 may be, for example, between about one every 90° and about ten every 90°. More specifically, the frequency at which the bumps 164 may be positioned around the second transition surface 152 may be, for example, between about two every 90° and about eight every 90°. As a specific, nonlimiting example, the frequency at which the bumps 164 may be positioned around the second transition surface 152 may be, for example, between about three every 90° and about seven every 90° (e.g., about five every 90°). A total number of bumps 164 located around the circumference of the second transition surface 152 may be, for example, between about four and about 40. More specifically, the total number of bumps 164 located around the circumference of the second transition surface 152 may be, for example, between about eight and about 32. As a specific, nonlimiting example, the total number of bumps 164 located around the circumference of the second transition surface 152 may be, for example, between about 12 and about 28 (e.g., about 20).
A radius of curvature R2 of an outer surface of the bumps 164 may be, for example, between about 0.02 inch and about 0.13 inch. More specifically, the radius of curvature R2 of an outer surface of the bumps 164 may be, for example, between about 0.06 inch and about 0.1 inch. As a specific, nonlimiting example, the radius of curvature R2 of an outer surface of the bumps 164 may be, for example, about 0.08 inch. In some embodiments, each bump 164 may have the same radius of curvature R. In other embodiments, at least one bump 164 may have a different radius of curvature R from a radius of curvature of at least one other bump 164.
The surface 178 of the waveform 174 may intersect with a planar surface 180 extending perpendicular to, and intersected by, the longitudinal axis 150. The planar surface 180 may be located, for example, in the same position along the longitudinal axis 150 as the edge defined at the intersection between the first transition surface 148 and the second transition surface 172. A diameter d of the planar surface 180 may be, for example, between about 10% and about 50% of a maximum diameter dmax of the superabrasive, polycrystalline material 134. More specifically, the diameter d of the planar surface 180 may be, for example, between about 20% and about 40% of the maximum diameter dmax of the superabrasive, polycrystalline material 134. As a specific, nonlimiting example, the diameter d of the planar surface 180 may be, for example, between about 25% and about 35% (e.g., about 30%) of the maximum diameter dmax of the superabrasive, polycrystalline material 134. In some embodiments, the planar surface 180 may exhibit a different degree of roughness than a remainder of the exposed surfaces of the superabrasive, polycrystalline material 134. For example, the planar surface 180 may be rougher than (e.g., may be polished to a lesser degree or with a less fine polish) the remainder of the exposed surfaces of the superabrasive, polycrystalline material 134. The change in direction from the surface 178 of the waveform 174 to the planar surface 180, and the optional change in roughness in certain embodiments, may cause cuttings produced by the cutting element 170 to break off, acting as a chip breaker.
A frequency of the waveform 174 may be, for example, between about one peak every 180° and about ten peaks every 90°. More specifically, the frequency of the waveform 174 may be, for example, between about two peaks every 90° and about eight peaks every 90°. As a specific, nonlimiting example, the frequency of the waveform 174 may be, for example, between about three peaks every 90° and about seven peaks every 90° (e.g., about five peaks every) 90°.
In embodiments where the cutting element 170 includes a waveform 174, such as that shown in
Various features of the cutting elements shown in
When forming the cutting element 130, 160, or 170, particles 200 of the superabrasive material may be positioned in the container 190 adjacent to the inverse 198. Catalyst material may be positioned in the container with the particles 200 of the superabrasive material, such as, for example, by intermixing particles of the catalyst material with the particles 200 of the superabrasive material or positioning a mass (e.g., a foil) of the catalyst material adjacent to the particles 200 of the superabrasive material. A preformed substrate or substrate precursor material or materials 202 may be positioned in the container 190 proximate the particles 200 of the superabrasive material. The container 190 may then be closed, and the entire assembly may be subjected to heat and pressure to sinter the particles 200 of the superabrasive material, forming the polycrystalline, superabrasive material 134 (see
As a result of the curved, stress-reduction features 156 shown herein, the stress, and particularly the occurrence of tensile stress, within the cutting elements 130, 160, 170, and 210 may be reduced. For example, the inventors have modeled the stresses experienced by at least one of the cutting elements 130, 160, 170, and 210, and the curved, stress-reduction features 156 may reduce the peak tensile stress within the cutting elements 130, 160, 170, and 210 by at least 15%. More specifically, the curved, stress-reduction features 156 may reduce the peak tensile stress by between about 15% and about 50%. As a specific, nonlimiting example, the curved, stress-reduction features 156 may reduce the peak tensile stress by between about 25% and about 45% (e.g., about 30%). It is expected that the others of the cutting elements 130, 160, 170, and 210 will perform similarly to, if not better than, the simulated results.
Additional, nonlimiting embodiments within the scope of this disclosure include the following:
A cutting element for an earth-boring tool, comprising: a substrate; and a polycrystalline, superabrasive material secured to an end of the substrate, the polycrystalline superabrasive material comprising: a first transition surface extending in a direction oblique to a central axis of the substrate; a second transition surface extending in a second direction oblique to the central axis, the second direction being different from the first direction; and a curved, stress-reduction feature located on the second transition surface.
The cutting element of Embodiment 1, wherein the curved, stress-reduction feature comprises a radiusing of the second transition surface, such that a slope of the second transition surface changes continuously from the first transition surface to a cutting face of the polycrystalline superabrasive material extending perpendicular to the central axis.
The cutting element of Embodiment 2, wherein a radius of curvature of the second transition surface is between 0.042 inch and 0.13 inch.
The cutting element of Embodiment 1, wherein the curved, stress-reduction feature comprises protrusions extending outward from the second transition surface.
The cutting element of Embodiment 4, wherein the protrusions are positioned in a repeating pattern around a circumference of the second transition surface at a frequency of between one every 90° and ten every 90°.
The cutting element of Embodiment 4 or Embodiment 5, wherein a perimeter of each protrusion as viewed in a plane at least substantially normal to the second transition surface at a geometrical center of a respective protrusion is circular.
The cutting element of Embodiment 1, wherein the curved, stress-reduction feature comprises a waveform extending around a circumference of the second transition surface.
The cutting element of Embodiment 7, wherein a surface of the waveform positioned to engage with an underlying earth formation and extending radially from the second transition surface toward the central axis is tapered toward the substrate.
The cutting element of Embodiment 8, wherein the surface of the waveform extends from the second transition surface to a planar surface of the polycrystalline, superabrasive material, the planar surface oriented perpendicular, and located proximate, to the central axis.
The cutting element of any one of Embodiments 7 through 9, wherein a frequency of the waveform is between one every 180° and ten every 90°.
The cutting element of any one of Embodiments 1 through 10, wherein a maximum thickness of the second transition surface as measured in a direction parallel to the central axis is between 0.01 inch and 0.05 inch.
An earth-boring tool, comprising: a body; and a cutting element secured to the body, the cutting element comprising: a substrate; and a polycrystalline, superabrasive material secured to an end of the substrate, the polycrystalline superabrasive material comprising: a first transition surface extending in a direction oblique to a central axis of the substrate; a second transition surface extending in a second direction oblique to the central axis, the second direction being different from the first direction; and a curved, stress-reduction feature located on the second transition surface.
The cutting element of Embodiment 12, wherein the curved, stress-reduction feature comprises a radiusing of the second transition surface, such that a slope of the second transition surface changes continuously from the first transition surface to a cutting face of the polycrystalline superabrasive material extending perpendicular to the central axis.
The cutting element of Embodiment 13, wherein a radius of curvature of the second transition surface is between 0.042 inch and 0.13 inch.
The cutting element of Embodiment 12, wherein the curved, stress-reduction feature comprises protrusions extending outward from the second transition surface.
The cutting element of Embodiment 15, wherein the protrusions are positioned in a repeating pattern around a circumference of the second transition surface at a frequency of between one every 90° and ten every 90°.
The cutting element of Embodiment 15 or Embodiment 16, wherein a perimeter of each protrusion as viewed in a plane at least substantially normal to the second transition surface at a geometrical center of a respective protrusion is circular.
The cutting element of Embodiment 12, wherein the curved, stress-reduction feature comprises a waveform extending around a circumference of the second transition surface.
The cutting element of Embodiment 18, wherein a surface of the waveform positioned to engage with an underlying earth formation and extending radially from the second transition surface toward the central axis is tapered toward the substrate.
The cutting element of Embodiment 19, wherein the surface of the waveform extends from the second transition surface to a planar surface of the polycrystalline, superabrasive material, the planar surface oriented perpendicular, and located proximate, to the central axis.
The cutting element of any one of Embodiments 18 through 20, wherein a frequency of the waveform is between one every 180° and ten every 90°.
The cutting element of any one of Embodiments 12 through 21, wherein a maximum thickness of the second transition surface as measured in a direction parallel to the central axis is between 0.01 inch and 0.05 inch.
A method of making a cutting element for an earth-boring tool, comprising: shaping a polycrystalline, superabrasive material to comprise: a first transition surface extending in a direction oblique to a central axis of the substrate; a second transition surface extending in a second direction oblique to the central axis, the second direction being different from the first direction; and a curved, stress-reduction feature located on the second transition surface; and securing the polycrystalline, superabrasive material to a substrate.
The method of Embodiment 23, wherein shaping the polycrystalline, superabrasive material comprises positioning a precursor material into a container exhibiting an inverse of a final shape of the polycrystalline superabrasive material and sintering the precursor material to form the polycrystalline, superabrasive material.
The method of Embodiment 23 or Embodiment 24, wherein shaping the polycrystalline, superabrasive material to comprise the curved, stress-reduction feature comprises shaping the polycrystalline, superabrasive material to comprise a radiusing of the second transition surface, such that a slope of the second transition surface changes continuously from the first transition surface to a cutting face of the polycrystalline superabrasive material extending perpendicular to the central axis.
The method of Embodiment 23 or Embodiment 24, wherein shaping the polycrystalline, superabrasive material to comprise the curved, stress-reduction feature comprises shaping the polycrystalline, superabrasive material to comprise protrusions extending outward from the second transition surface.
The method of Embodiment 23 or Embodiment 24, wherein shaping the polycrystalline, superabrasive material to comprise the curved, stress-reduction feature comprises shaping the polycrystalline, superabrasive material to comprise a waveform extending around a circumference of the second transition surface.
The method of claim 27, shaping the polycrystalline, superabrasive material to comprise the waveform comprises tapering a surface of the waveform toward the substrate, the surface of the waveform positioned to engage with an underlying earth formation and extending radially from the second transition surface toward the central axis.
The method of claim 28, wherein tapering the surface of the waveform comprises tapering the surface of the waveform to extend from the second transition surface to a planar cutting face of the polycrystalline, superabrasive material, the planar cutting face oriented perpendicular, and located proximate, to the central axis.
The method of any one of Embodiments 23 through 29, wherein shaping the polycrystalline, superabrasive material to comprise the second transition surface comprises rendering a maximum thickness of the second transition surface as measured in a direction parallel to the central axis between 0.01 inch and 0.05 inch.
While certain illustrative embodiments have been described in connection with the figures, those of ordinary skill in the art will recognize and appreciate that the scope of this disclosure is not limited to those embodiments explicitly shown and described in this disclosure. Rather, many additions, deletions, and modifications to the embodiments described in this disclosure may be made to produce embodiments within the scope of this disclosure, such as those specifically claimed, including legal equivalents. In addition, features from one disclosed embodiment may be combined with features of another disclosed embodiment while still being within the scope of this disclosure, as contemplated by the inventor.