U.S. patent application number 12/465441 was filed with the patent office on 2010-11-18 for cutting element for use in a drill bit for drilling subterranean formations.
This patent application is currently assigned to BAKER HUGHES INCORPORATED. Invention is credited to Jorge A. Dovalina, JR., Nicholas J. Lyons.
Application Number | 20100288564 12/465441 |
Document ID | / |
Family ID | 43067610 |
Filed Date | 2010-11-18 |
United States Patent
Application |
20100288564 |
Kind Code |
A1 |
Dovalina, JR.; Jorge A. ; et
al. |
November 18, 2010 |
CUTTING ELEMENT FOR USE IN A DRILL BIT FOR DRILLING SUBTERRANEAN
FORMATIONS
Abstract
A cutting element for use in a drill bit for drilling
subterranean formations including a substrate having a body
including an upper surface extending transversely to a longitudinal
axis of the body, a superabrasive layer overlying the upper surface
of the substrate, wherein the superabrasive layer includes an
annular shape having a central opening defined by an inner surface.
The cutting element further includes an abrasive insert overlying
the upper surface of the substrate and disposed within the central
opening of the superabrasive layer, wherein the abrasive insert has
an upper surface having a surface roughness (R.sub.a) of greater
than about 1 micron.
Inventors: |
Dovalina, JR.; Jorge A.;
(Magnolia, TX) ; Lyons; Nicholas J.; (Houston,
TX) |
Correspondence
Address: |
LARSON NEWMAN & ABEL, LLP
5914 WEST COURTYARD DRIVE, SUITE 200
AUSTIN
TX
78730
US
|
Assignee: |
BAKER HUGHES INCORPORATED
Houston
TX
|
Family ID: |
43067610 |
Appl. No.: |
12/465441 |
Filed: |
May 13, 2009 |
Current U.S.
Class: |
175/428 |
Current CPC
Class: |
E21B 10/5676
20130101 |
Class at
Publication: |
175/428 |
International
Class: |
E21B 10/567 20060101
E21B010/567; E21B 10/55 20060101 E21B010/55 |
Claims
1. A cutting element for use in a drill bit for drilling
subterranean formations comprising: a substrate comprising a body
having an upper surface extending transversely to a longitudinal
axis of the body; a superabrasive layer overlying the upper surface
of the substrate, wherein the superabrasive layer comprises an
annular shape having a central opening defined by an inner surface;
and an abrasive insert overlying the upper surface of the substrate
and disposed within the central opening of the superabrasive layer,
wherein the abrasive insert comprises an upper surface having a
surface roughness (R.sub.3) of greater than about 1 micron.
2. The cutting element of claim 1, wherein the surface roughness
(R.sub.a) of the upper surface is greater than about 3 microns.
3. The cutting element of claim 1, wherein the surface roughness
(R.sub.a) of the upper surface is within a range between about 1
micron and about 50 microns.
4-8. (canceled)
9. The cutting element of claim 1, wherein the abrasive insert
comprises abrasive grit contained within a matrix material.
10. The cutting element of claim 9, wherein the abrasive grit
comprise encapsulated abrasive grit comprising an encapsulating
material substantially surrounding the abrasive grit.
11-15. (canceled)
16. The cutting element of claim 9, wherein the matrix material
comprises a metal.
17-19. (canceled)
20. The cutting element of claim 9, wherein the abrasive grit
comprises a material selected from the group of materials
consisting of oxides, borides, nitrides, carbides, carbon, and a
combination thereof.
21. The cutting element of claim 9, wherein the abrasive grit
comprises a superabrasive material.
22. (canceled)
23. The cutting element of claim 9, wherein the abrasive grit
comprises an average grit size of at least about 25 microns.
24-25. (canceled)
26. The cutting element of claim 23, wherein the abrasive grit
comprises an average grit size within a range between about 25
microns and about 2 mm.
27-34. (canceled)
35. The cutting element of claim 1, wherein the central opening has
a circular cross-sectional contour as viewed perpendicular to the
longitudinal axis.
36. The cutting element of claim 1, wherein the central opening
comprises a polygonal cross-sectional contour as viewed
perpendicular to the longitudinal axis.
37. The cutting element of claim 1, wherein the central opening
comprises a side surface that is tapered at an angle relative to
the longitudinal axis of the body.
38-40. (canceled)
41. A cutting element for use in a drill bit for drilling
subterranean formations comprising: a cutting table comprising: a
superabrasive layer comprising an annular shape having a central
opening defined by an inner surface; and an abrasive insert
overlying the upper surface of the substrate and disposed within
the central opening of the superabrasive layer, wherein the
abrasive insert comprises abrasive grit contained within a matrix
material, wherein an upper region of the abrasive insert comprising
an upper surface has a different amount of abrasive grit than a
lower region of the abrasive insert.
42. The cutting element of claim 41, wherein the upper region
comprises at least about 10% less amount of abrasive grit than the
lower region of the abrasive insert.
43. (canceled)
44. The cutting element of claim 41, wherein the upper region
comprises at least about a 10% greater amount of abrasive grit than
the lower region of the abrasive insert.
45-46. (canceled)
47. The cutting element of claim 41, wherein the abrasive insert
comprises a graded amount of abrasive grit throughout the height of
the abrasive insert.
48. The cutting element of claim 47 wherein the amount of abrasive
grit within the matrix increases from a rear surface to the upper
surface.
49-53. (canceled)
54. A cutting element for use in a drill bit for drilling
subterranean formations comprising: a cutting table comprising: a
superabrasive layer comprising an annular shape having a central
opening defined by an inner surface; and an abrasive insert
disposed within the central opening of the superabrasive layer,
wherein the abrasive insert comprises an upper surface having a
texture comprising protrusions and recesses.
55. The cutting element of claim 54, wherein the abrasive insert
comprises abrasive grit contained within a matrix material and the
protrusions of the upper surface comprise abrasive grit extending
from the upper surface of the matrix material.
56-66. (canceled)
Description
BACKGROUND
[0001] 1. Field of the Disclosure
[0002] The following is directed to cutting elements for use in
drill bits for drilling subterranean formations and more
particularly, cutting elements utilizing a cutting table comprising
a superabrasive layer and an abrasive insert.
[0003] 2. Description of the Related Art
[0004] In the past, rotary drill bits have incorporated cutting
elements employing superabrasive materials, including synthetic
diamond cutters using polycrystalline diamond compacts, otherwise
termed "PDC" cutters. Such PDC cutters have had various shapes and
designs, including self-supported cutters, otherwise a monolithic
object solely of the made of the desired cutting material, or
alternatively, cutters employing a polycrystalline diamond layer or
"table" on a substrate made of a hard metal material suitable for
supporting the diamond layer.
[0005] Despite improvements in PDC cutter designs, certain
obstacles remain, including for example, performance degradation
and failure of cutters due to mechanical strain, thermal-induced
strain, and a combination of such forces. Delamination and fracture
of a cutter can occur given the extreme loading and temperatures
generated during drilling operations. Furthermore, repetitive
heating and cooling of the cutter can amplify damage to the cutter
due to differences in thermal expansion coefficient and thermal
conductivity of the cutter components. Wear characteristics of
cutters have also been studied to mitigate catastrophic damage to
the cutter surfaces.
[0006] Various different configurations of cutters have been used
to overcome some of the above noted obstacles, however, significant
shortcomings are still exhibited by conventional cutters, and there
remains a need in the art for improvements.
SUMMARY
[0007] According to one aspect, a cutting element for use in a
drill bit for drilling subterranean formations includes a substrate
having a body having an upper surface extending transversely to a
longitudinal axis of the body, a superabrasive layer overlying the
upper surface of the substrate, wherein the superabrasive layer
comprises an annular shape having a central opening defined by an
inner surface, and an abrasive insert overlying the upper surface
of the substrate. The abrasive insert can be disposed within the
central opening of the superabrasive layer, wherein the abrasive
insert comprises an upper surface having a surface roughness
(R.sub.a) of greater than about 1 micron.
[0008] In another aspect, a cutting element for use in a drill bit
for drilling subterranean formations includes a cutting table made
of a superabrasive layer comprising an annular shape having a
central opening defined by an inner surface, and an abrasive insert
overlying the upper surface of the substrate and disposed within
the central opening of the superabrasive layer. The abrasive insert
includes abrasive grit contained within a matrix material, wherein
an upper region of the abrasive insert comprising an upper surface
has a different amount of abrasive grit than a lower region of the
abrasive insert.
[0009] In accordance with still another aspect, a cutting element
for use in a drill bit for drilling subterranean formations
includes a cutting table made of a superabrasive layer having an
annular shape having a central opening defined by an inner surface,
and an abrasive insert disposed within the central opening of the
superabrasive layer, wherein the abrasive insert comprises an upper
surface having a texture comprising protrusions and recesses.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The present disclosure may be better understood, and its
numerous features and advantages made apparent to those skilled in
the art by referencing the accompanying drawings.
[0011] FIG. 1 includes an illustration of a subterranean drilling
operation.
[0012] FIG. 2 includes an illustration of a drill bit in accordance
with an embodiment.
[0013] FIGS. 3A-3C include cross-sectional illustrations and a
perspective view of cutter elements in accordance with
embodiments.
[0014] FIG. 4 includes a cross-sectional illustration of a portion
of a cutter element in accordance with an embodiment.
[0015] FIG. 5 includes a cross-sectional illustration of a portion
of a cutter element in accordance with an embodiment.
[0016] FIG. 6 includes a cross-sectional illustration of a portion
of a cutter element in accordance with an embodiment.
[0017] FIGS. 7A-7C include top view illustrations of cutter
elements in accordance with embodiments.
[0018] The use of the same reference symbols in different drawings
indicates similar or identical items.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0019] The following is directed to earth boring drill bits, and
more particularly, towards cutting elements used in such drill
bits. The terms "bit", "drill bit", and "matrix drill bit" may be
used in this application to refer to "rotary drag bits", "drag
bits", "fixed cutter drill bits" or any other earth boring drill
bit incorporating the teachings of the present disclosure. Such
drill bits may be used to form well bores or boreholes in
subterranean formations.
[0020] An example of a drilling system for drilling such well bores
in earth formations is illustrated in FIG. 1. In particular, FIG. 1
illustrates a drilling system including a drilling rig 101 at the
surface, serving as a station for a crew of workers to operate a
drill string 103. The drill string 103 defines a well bore 105
extending into the earth and can include a series of drill pipes
100 and 103 that are coupled together via joints 104 facilitating
extension of the drill string 103 for great depths into the well
bore 105. The drill string 103 may include additional components,
such as tool joints, a kelly, kelly cocks, a kelly saver sub,
blowout preventers, safety valves, and other components known in
the art.
[0021] Moreover, the drill string can be coupled to a bottom hole
assembly 107 (BHA) including a drill bit 109 used to penetrate
earth formations and extend the depth of the well bore 105. The BHA
107 may further include one or more drill collars, stabilizers, a
downhole motor, MWD tools, LWD tools, jars, accelerators, push and
pull directional drilling tools, point stab tools, shock absorbers,
bent subs, pup joints, reamers, valves, and other components. A
fluid reservoir 111 is also present at the surface that holds an
amount of liquid that can be delivered to the drill string 103, and
particularly the drill bit 109, via pipes 113, to facilitate the
drilling procedure.
[0022] FIG. 2 includes a perspective view of a fixed cutter drill
bit according to an embodiment. As shown in FIG. 2, the fixed
cutter drill bit 200 can include a bit body 213 which may be
connected to a shank portion 214 via a weld. The shank portion 214
can include a threaded portion 215 for connection of the drill bit
200 to other components of the BHA. The drill bit body 213 can
further include a breaker slot 221 extending laterally along the
circumference of the drill bit body 213 to aid coupling and
decoupling of the drill bit 200 to other components.
[0023] The drill bit 200 can include a crown portion 222 coupled to
the drill bit body 213. As will be appreciated, the crown portion
222 can be integrally formed with the drill bit body 213 such that
they are a single, monolithic piece. The crown portion 222 can
include gage pads 224 situated along the sides of protrusions or
blades 217 that extend radially from the crown portion 222. Each of
the blades 217 extend from the crown portion 222 and include a
plurality of cutting members 219 bonded to the blades 217 for
cutting, scraping, and shearing through earth formations when the
drill bit 200 is rotated during drilling. The cutting members 219
may be tungsten carbide inserts, polycrystalline diamond compacts
(PDC), milled steel teeth, and particularly those cutting elements
described herein. Coatings or hard facings may be applied to the
cutting members 219 and other portions of the bit body 213 or crown
portion 222 to reduce wear and increase the life of the drill bit
200.
[0024] The crown portion 222 can further include junk slots 227 or
channels formed between the blades 217 that facilitate fluid flow
and removal of cuttings and debris from the well bore. Notably, the
junk slots 227 can further include openings 223 for passages
extending through the interior of the crown portion 222 and bit
body 213 for communication of drilling fluid through the drill bit
200. The openings 223 can be positioned at exterior surfaces of the
crown portion 222 at various angles for dynamic fluid flow
conditions and effective removal of debris from the cutting region
during drilling.
[0025] FIGS. 3A-3C include cross-sectional illustrations and a
perspective view illustration of cutting elements in accordance
with an embodiment. Referring to FIG. 3A, a cross-sectional
illustration of a cutting element is provided. The cutting element
300 includes a substrate 301 which can have a shape suitable for
maintaining a cutting table 306 thereon. The substrate 301 can have
various shapes, for example, a cylindrical shape having a height as
defined by a longitudinal axis 310 extending through the body of
the substrate 301. Substrates herein can have an upper surface 305
that extends transversely to the longitudinal axis 310, and a rear
surface opposite and parallel to the upper surface 305. It will be
appreciated that other geometries may be suitable for the substrate
301.
[0026] The substrate 301 can have a hardness suitable for
withstanding drilling operations. That is, certain substrates 301
can be made of a material having a Mohs hardness of at least about
8, or at least about 8.5, at least about 9.0, or even at least
about 9.5. Particular metals or metal alloy materials may be used
to form the substrate 301. For example, the substrate 301 can be
formed of carbides, nitrides, oxides, borides, carbon-based
materials, and a combination thereof. Reference herein to
carbon-based materials is reference to synthetically-produced
molecules made entirely of carbon and the various carbon
allotropes, such as carbon nanotubes and the like. In some
instances, the substrate 301 may be made of a cemented material
such as a cemented carbide. Some suitable cemented carbides may
include metal carbides, and more particularly cemented tungsten
carbide such that the substrate 301 consists essentially of
cemented tungsten carbide.
[0027] As illustrated, the cutting element 300 can be formed such
that a cutting table 306 overlies the upper surface 305 of the
substrate 301. The cutting table 306 can be formed of two
components, notably including a superabrasive layer 302 having an
annular shape and comprising a central opening 329 as defined by an
inner surface 315 of the superabrasive layer 302. Furthermore, the
cutting table 306 includes an abrasive insert 303 overlying the
upper surface 305 of the substrate 301 and disposed within the
central opening 329 of the superabrasive layer 302 as defined by
the inner surface 315.
[0028] Referring briefly to FIG. 3B, a perspective view
illustration provides an alternative view demonstrating the
orientation between the superabrasive layer 302 and the abrasive
insert 303. The superabrasive layer 302 is formed such that it has
an annular shape, including a central opening 329 extending
radially and axially around a central point at the center of the
cutting table 306. As further illustrated in FIG. 3B, the cutting
table 306 is formed such that the abrasive insert 303 is configured
to fit within the central opening 329 of the superabrasive layer
302.
[0029] Referring again to FIG. 3A, the superabrasive layer 302 can
be formed such that the central opening 329, and therein the
abrasive insert 303, extend through the entire height 333 of the
cutting table 306. However, in other embodiments, the central
opening may extend for a fraction of the height 333, and therein
the abrasive insert 303 extends for only a fraction of the height
333 of the abrasive table 306. In such designs, the superabrasive
layer 302 would be formed with a central recess (as opposed to a
central opening 329) that would contain the abrasive insert
303.
[0030] Moreover, the cutting table 306 can be formed such that the
superabrasive layer 302 comprises a bottom surface 312 that can
directly contact the upper surface 305 of the substrate 301, and
more particularly can be bonded to the upper surface 305 of the
substrate 301. The abrasive insert 303 of the cutting table 306 can
be formed such that it comprises a rear surface 313 that is
directly contacting the upper surface 305 of the substrate 301, and
more particularly is bonded to the upper surface 305 of the
substrate 301. Additionally, the cutting table 306 can be formed
such that the superabrasive layer 302 is bonded to the abrasive
insert 303 at the inner surface 315 defining the interface between
the components.
[0031] The superabrasive layer 302 can include superabrasive
materials such as diamond, boron nitride (e.g., cubic boron
nitride), carbon-based materials, and a combination thereof. Some
superabrasive layers may be in the form of polycrystalline
materials. For instance, the superabrasive layer 302 can consist
essentially of polycrystalline diamond. With reference to those
embodiments using polycrystalline diamond, the superabrasive layer
302 can be made of various types of diamond including
thermally-stable polycrystalline diamond, which can contain a
lesser amount of catalyst materials (e.g., cobalt) than other
diamond materials, making the material stable at higher
temperatures.
[0032] The cutting table 306 can be formed such that the
superabrasive layer 302 comprises a side surface 309 that extends
parallel to the longitudinal axis 310, an upper surface 307 that
extends transversely to the longitudinal axis 310, and a chamfered
surface 308 extending between the side surface 309 and upper
surface 307 at an angle to the longitudinal axis 310. The length
and angle of the chamfered surface 308 may be controlled depending
on the intended application of the cutting element 300. It will
further be appreciated that embodiments herein may utilize cutting
elements having a radiused edge, wherein the edge between the upper
surface and the side surface of the cutting element comprises a
curved or arcuate surface defined by a radius.
[0033] The abrasive insert 303 can be formed such that it includes
abrasive grit 331 contained within a matrix material 332, which may
facilitate improved wear characteristics, mechanical integrity, and
cutting ability of the cutting table 306. As used herein, reference
to a matrix material is reference to a solid material for
containing abrasive grit therein, such as a polycrystalline
material, formed from a metal or cermet material as will be
described in more detail. For some cutter designs, the abrasive
insert 303 can be formed such that the abrasive grit 331 is
dispersed uniformly throughout the entire volume of matrix material
332. In accordance with one embodiment, the abrasive insert 303 is
formed such that it includes at least 10 vol % abrasive grit 331
contained within the matrix material 332 for the entire volume of
the abrasive insert 303. In other designs, the amount of abrasive
grit can be greater, such as on the order of at least 15 vol %, at
least 25 vol %, at least 40 vol %, or even at least about 50 vol %
of abrasive grit 331 contained within the matrix material 332 for
the entire volume of the abrasive insert 303. In particular
instances, the cutting table 306 is designed such that the abrasive
insert 303 contains an amount of abrasive grit within a range
between about 10 vol % and 70 vol %, such as between about 15 vol %
and 60 vol %, and more particularly between about 20 vol % and 50
vol %.
[0034] The abrasive grit 331 can be contained within a matrix
material 332 that comprises a metal or metal alloy material. For
example, the matrix material 332 can be made of a carbide material,
such as a metal carbide. One suitable metal carbide material is
tungsten carbide, and in fact, some cutter designs utilize a matrix
material 332 that consists essentially of tungsten carbide. Some
other suitable metals or metal alloys may include transition metal
elements.
[0035] Additionally, the abrasive grit 331 can be formed of
abrasive material having suitable abrading and cutting
capabilities. For example, suitable abrasive materials can include
oxides, borides, nitrides, carbides, carbon-containing materials,
and a combination thereof. Reference herein to carbon-based
materials is reference to synthetically produced molecules made
entirely of carbon and various carbon allotropes, such as carbon
nanotubes and the like. Certain abrasive materials for use as the
abrasive grit can include alumina, silica, silicon carbide,
combinations thereof and the like. In certain instances, the
abrasive grit 331 is formed of a superabrasive material, such as
diamond, cubic boron nitride, and a combination thereof. Particular
cutting elements are formed such that the abrasive insert 303 uses
only abrasive grit 331 consisting of diamond.
[0036] With particular reference to embodiments employing diamond
abrasive grit, the grit material can have particular multi-faceted
shapes providing a plurality of sharp edges suitable for cutting
and abrading hard formations. For example, the diamond abrasive
grit can be cubo-octahedral, cubic faced, and the like.
[0037] Additionally, the abrasive grit 331 can employ encapsulated
grit, such that each of the particles of abrasive grit 331 are
substantially surrounded by an encapsulating material. The
encapsulating material may improve the mechanical properties of the
abrasive grit (e.g., wear resistance), provide added protection for
the abrasive grit during processing, particularly with regard to
thermal cycling used in various manufacturing processes, and
further improve the bonding characteristics between the abrasive
grit and the matrix material 332. Additionally, provision of
encapsulated grit can facilitate proper spacing and distribution of
the abrasive grit 331 within the matrix material 332. Suitable
compositions for use as the encapsulant material can include
ceramics, such as oxides, carbides, borides, nitrides, and
carbon-based materials. Other encapsulant materials can include
refractory metal or refractory metal alloy compositions.
[0038] Certain sizes of abrasive grit 331 can be used to aid proper
functioning of the abrasive insert 303. For example, the abrasive
grit 331 can have an average grit size of at least about 25
microns, such as at least about 50 microns, at least about 100
microns, or even at least about 200 microns. In certain instances,
the abrasive grit has an average grit size within a range between
about 25 microns and about 2 millimeters and more particularly
between about 100 microns and about 1 millimeters, and even more
particularly between about 100 microns and about 0.5
millimeter.
[0039] FIG. 3C includes a cross-sectional illustration of a cutting
element in accordance with an embodiment. The cutting element 350
includes a cutting table 306 overlying the upper surface 305 of the
substrate 301 as previously described in accordance with FIG. 3A.
Notably, the cutting table 306 of FIG. 3C demonstrates an abrasive
insert 303 having a different shape than the abrasive insert of
embodiment in FIG. 3A. The abrasive insert 303 and particularly,
the superabrasive layer 302 is formed such that the interface
between the abrasive insert 303 and superabrasive layer 303
comprises a tapered surface 325. The tapered surface 325 extends at
an angle to the longitudinal axis 310 such that the diameter of the
central opening 329 at the upper surface 307 of the superabrasive
layer 302 is smaller than the diameter of the central opening 329
at the bottom surface 312.
[0040] FIG. 4 includes a cross-sectional illustration of a portion
of a cutting element in accordance with an embodiment. The cutting
element 400 includes a cutting table 406 comprising the
superabrasive layer 302 and abrasive insert 303 disposed within a
central opening of the superabrasive layer 302. As illustrated, the
abrasive insert 303 is formed such that it has an upper surface 317
having particular features. That is, in accordance with one
embodiment, the abrasive insert 303 can be formed such that the
upper surface 317 has a particular surface roughness, which may be
suitable for conducting certain types of cutting operations and
improving the wear characteristics of the cutting table 406. In
accordance with one embodiment, the abrasive insert 303 can have a
surface roughness (R.sub.a) of greater than about 1 micron. It will
be noted that the reference to surface roughness is an arithmetic
average of the roughness profile as measured through physical
(e.g., a stylus) or optical measuring techniques. In other
embodiments, the abrasive insert 303 is formed such that the upper
surface 317 has a greater surface roughness, such as on the order
of greater than about 3 microns, greater than about 5 microns,
greater than about 10 microns, or even greater than about 15
microns. In particular instances, the abrasive insert 303 can be
formed such that the upper surface 317 has a surface roughness
(R.sub.a) within a range between about 1 micron and about 50
microns, such as between about 1 micron and about 30 microns, and
more particularly between 1 micron and 20 microns or even more
particularly between 1 micron and about 10 microns.
[0041] In addition to the characteristics of surface roughness
described herein, the abrasive insert 303 can be formed with an
upper surface 317 that has a texture defined by projections 403 and
recesses 404 extending across the upper surface 317. Notably, the
projections 403 can be formed by abrasive grit 332 protruding
through the matrix material 332, while the recesses 404 can be
regions along the upper surface 317 that may be absent the abrasive
grit 332. In particular, the recesses 404 can be regions comprising
primarily the matrix material 332 between the projections 403
formed by the abrasive grit 332.
[0042] In certain embodiments, the arrangement of projections 403
along the upper surface 317 of the abrasive insert 303 can be a
random orientation. That is, there is no long range or short range
order between the orientation of the projections 403 with respect
to each other. Moreover, the recesses 404 can have a random
arrangement with no short range order or long range order with
respect to the projections 403 or each other. However, in other
embodiments, the abrasive insert 303 can be formed such that the
upper surface 317 has a pattern of projections 403 and recesses 404
such that they are ordered relative to each other in an array. In
such embodiments, the abrasive insert 303 may be cast or molded
initially to form the pattern of projections 403 and recesses
404.
[0043] Embodiments herein may utilize a particular arrangement
between the amount of superabrasive layer and the amount of
abrasive insert forming the cutting table. For example, in certain
designs the abrasive insert is formed such that it comprises at
least 10 vol % of the total volume of the cutting table. In fact,
certain embodiments may utilize a larger abrasive insert, such that
it comprises at least 20 vol %, at least about 30 vol %, or even at
least about 40 vol % of the total volume of the cutting table.
Still, the size of the abrasive insert 303 may be limited such that
the abrasive insert comprises between about 10 vol % and 60 vol %,
and more particularly between about 10 vol % and 50 vol % of the
total volume of the cutting table.
[0044] Additionally, cutting tables of the cutting elements herein
may utilize a particular arrangement between the superabrasive
layer 302 and abrasive insert 303 such that a certain amount of the
upper surfaces of these components 307 and 317 is exposed. For
example, certain designs utilize a cutting table wherein the upper
surface of the abrasive insert 303 comprises at least about 10% of
the total surface area of the upper surface of the cutting table,
which includes the upper surface 307 of the superabrasive layer 302
and the upper surface 317 of the abrasive insert 303. In other
embodiments, the percentage of the surface area occupied by the
upper surface 317 of the abrasive insert 303 is greater, such as on
the order of at least 20%, at least about 25%, or even at least 30%
of the total surface area of the upper surface of the cutting
table. However, the total surface area occupied by the upper
surface 317 of the abrasive insert 303 may be limited such that it
may be between about 10% and 75%, such as between about 20% and
60%, and more particularly between about 20% and 50% of the total
surface area of the upper surface of the cutting table.
[0045] FIG. 5 includes a cross-sectional illustration of a portion
of a cutting element in accordance with an embodiment. The cutting
element 500 illustrates a cutting table 506 comprising a
superabrasive layer 302 and an abrasive insert 303 disposed within
the central opening of the superabrasive layer 302. In particular,
the abrasive insert 303 comprises a lower region 501 that includes
the rear surface 313, which is bonded to the upper surface 305 of
the substrate 301. Additionally, the abrasive insert 303 comprises
an upper region 503 comprising the upper surface 317 that is
axially spaced apart from the rear surface 313 along the
longitudinal axis 310. Notably, the abrasive insert 303 comprises
at least two distinct regions; the lower region 501 and upper
region 503, which can represent at least two distinct layers within
the abrasive insert 303.
[0046] In particular cutting elements, the abrasive insert 303 can
be formed such that the upper region 503 includes a different
amount of abrasive grit 505 within the matrix material 504 than the
amount of abrasive grit 509 contained within the matrix material
508 of the lower region 501. For example, in particular
embodiments, the bonding interface at the rear surface 313 of the
lower region 501 and the upper surface 305 of the substrate 301 can
be substantially free of abrasive grit 509 to facilitate bonding
between the lower region 501 of the abrasive insert 303 and the
upper surface 305 of the substrate 301. Such a design may
facilitate bonding of the lower region 501 to the upper surface 305
of the substrate 301
[0047] In certain designs, the upper region 503 comprises at least
about 10% greater amount (per unit volume) of abrasive grit than
the lower region 501 of the abrasive insert 303. In other
embodiments, the amount of abrasive grit in the upper region 503 as
compared to the lower region 501 may be greater, such as on the
order of at least about 15% greater, at least about 20% greater, or
even at least about 50% greater amount of abrasive grit within the
upper region 503 than the lower region 501. Such a design may
facilitate a greater amount of abrasive grit in the upper region
for improved cutting and wear resistance and a lower amount of
abrasive grit in the lower region 501 for improved bonding of the
abrasive insert 303 to the substrate 301. In particular
embodiments, the upper region 503 comprises between about 10% and
about 100%, and more particularly between about 15% and about 80%
greater amount of abrasive grit than the lower region 501 of the
abrasive insert 503.
[0048] In alternative embodiments, the upper region 503 can be
formed such that it contains a lesser amount of abrasive grit than
the lower region 501. For instance, particular cutting designs
utilize an upper region 503 having at least about 10% lesser amount
(per unit volume) of abrasive grit than the lower region 501 of the
abrasive insert 303. In other embodiments, the amount of abrasive
grit in the upper region 503 as compared to the lower region 501
may be lesser, such as on the order of at least about 15% less, at
least about 20% less, or even at least about 30% less than the
lower region 501. Such a design can facilitate a greater stiffness
of material within the lower region 501 for supporting the upper
region 503.
[0049] While the cutting table 506 is illustrated as having
distinct or discrete layers defining the lower region 501 and upper
region 503, it will be appreciated that such a change in the amount
of abrasive grit may not necessarily include a layered structure,
but a gradual change in the amount of abrasive grit present within
the matrix material over the height of the abrasive insert 303.
[0050] FIG. 6 includes a cross-sectional illustration of a portion
of a cutting element in accordance with an embodiment. The cutting
element 600 includes a cutting table 606 having a superabrasive
layer 302 of an annular shape and defining a central opening, and
further includes an abrasive insert 303 disposed within the central
opening of the superabrasive layer 302. In accordance with one
particular embodiment, the abrasive insert 303 can comprise a
graded concentration of abrasive grit 625 through the height of the
abrasive insert 303 such that the amount of abrasive grit 625
within the matrix material 626 is different at different positions
along the longitudinal axis 310 from the rear surface 313 of the
abrasive insert 303 to the upper surface 317 of the abrasive
insert.
[0051] In particular designs the amount of abrasive grit at the
upper surface 317 is greater than the amount of abrasive grit at
the rear surface 313 such that the amount of abrasive grains
increases along the height of the abrasive insert 303 as defined by
the longitudinal axis 310. In particular instances, the upper
surface. It will be appreciated, that in certain embodiments, the
abrasive insert 303 can be formed such that the upper surface 317
is formed to have a greater amount of abrasive grit 625 than matrix
material 626.
[0052] Still, in some alternative embodiments, the direction of
abrasive grit concentration grading through the volume of the
abrasive insert 303 can be alternated in an axial direction, radial
direction, or a combination thereof. For example, the graded
direction of abrasive grit may be reversed, such that the amount of
abrasive grit 625 contained within the matrix material 626
decreases at distances along the longitudinal axis 310 away from
the rear surface 313. In still other alternative embodiments, a
cutting element can be formed that includes an abrasive insert
having a graded amount of abrasive grit 625 contained within the
matrix material 626, wherein the concentration of abrasive grit
increases with proximity to the inner surface 605 of the
superabrasive layer 302. That is, the abrasive insert can be formed
such that regions in the center of the abrasive insert along the
longitudinal axis 310 comprise a lesser amount of abrasive grit 625
than regions within the abrasive insert spaced apart from the
longitudinal axis 310 at a radial distance which are closer in
proximity to the inner surface 605 of the superabrasive layer 302.
Such designs may facilitate the formation of a cutting element
capable of maintaining suitable cutting rates when the cutting
table 606 wears into the abrasive insert.
[0053] FIG. 7A-7C provides top view illustrations of cutting
elements in accordance with an embodiment. In particular, FIGS.
7A-7C demonstrate various shapes of the abrasive insert that can be
formed. In particular, FIG. 7A illustrates an abrasive insert 701
contained within a central opening of a superabrasive layer 302,
wherein the abrasive insert 701 comprises an elliptical shape. FIG.
7B includes an abrasive insert 703 having an irregular shaped
abrasive insert 703 containing long arm sections 704 and 705 that
are joined by short arm sections 706 and 707. FIG. 7B illustrates
that various irregular shapes are suitable for use in the abrasive
insert. FIG. 7C includes a polygonal shaped abrasive insert 709, in
particular, an octahedral-shaped abrasive insert 703 contained
within a central opening of a superabrasive layer 302 for use in a
cutting element.
[0054] The cutting elements described herein can be formed using
one or more particular methods. For example, the superabrasive
layer of the cutting table and the substrate can be formed using a
high pressure/high temperature (HP/HT) process, wherein the
substrate material is loaded into a HP/HT cell with the appropriate
orientation and amount of diamond crystal material, typically of a
size of 100 microns or less. Furthermore, a metal catalyst powder
can be added to the HP/HT cell, which can be provided in the
substrate or intermixed with the diamond crystal material. The
loaded HP/HT cell is then placed in a process chamber, and subject
to high temperatures (approximately between 1450-1600.degree. C.)
and high pressures (approximately between 50-70 kilobar), wherein
the diamond crystals, stimulated by the catalytic effect of the
metal catalyst powder, bond to each other and to the substrate
material to form a PDC product.
[0055] For certain cutting elements, the PDC product can be further
processed to form a thermally stable polycrystalline diamond
material (commonly referred to as "TSP") by leaching out the
remaining metal catalyst material in the diamond layer.
Alternatively, silicon, which possesses a coefficient of thermal
expansion similar to that of diamond, may be used to bond diamond
particles to produce a Si-bonded TSP. Such TSP materials are
capable of enduring higher temperatures (on the order of
1200.degree. C.).
[0056] With regard the to the abrasive insert, in certain
processes, the abrasive insert can be formed separately from the
superabrasive layer and the substrate. Certain suitable forming
methods can include molding, casting, heating, pressing, and a
combination thereof to give the abrasive insert the proper shape
such that it fits into the cutting table with the superabrasive
layer as described in embodiments herein. Notably, for more complex
designs of the abrasive insert, such as those having layers or
graded compositions of abrasive grit within the matrix material,
individual layers or films of the appropriate material may be
formed in a molding or casting cell before the final forming
process. For example, a series of layers may be formed in a molding
cell that includes a first layer having a predetermined amount of
abrasive grit, a second layer may be formed on the first layer
having a greater content of abrasive grit than the first layer, and
a third layer may be formed on the second layer having a greater
content of abrasive grit than the second layer, and so on. The
layered structure may then be formed in a single process utilizing
heat and/or pressure, such as a hot isostatic pressing process to
form the abrasive insert.
[0057] After forming the abrasive insert, the insert may be fit
into the cutting table, and may be particularly bonded to the
superabrasive layer and the substrate. Some machining may take
place such that the abrasive insert has the proper dimensions for
fitting into the cutting table. Suitable processes for bonding of
the abrasive insert may include hot pressing, brazing, and the
like.
[0058] In other alternative processes, the abrasive insert can be
formed using a high pressure/high temperature (HP/HT) process, such
as the one used to form the superabrasive layer and the substrate.
In fact, some forming methods may simultaneously form the
superabrasive layer, abrasive insert, and the substrate in the same
chamber at the same time. Such a process may require a special
HP/HT cell capable of accommodating all of the components and
effectively forming said components. Notably, such a process may be
suitable for designs utilizing complex geometries between the
superabrasive layer and the abrasive insert.
[0059] As will be appreciated, after the formation of the cutting
element, finishing processes can be undertaken to prepare the
surfaces for drilling applications. For example, surfaces of the
superabrasive layer may be formed to have chamfers in accordance
with the embodiments herein. Moreover, the surfaces of the cutting
body may be polished.
[0060] The embodiments herein represent a departure from
conventional cutting elements. While changes to cutting elements
for use in drill bits have been disclosed, such changes generally
are directed to the use of different or new materials, combinations
of different materials within the cutting table, and different
arrangements of the cutting table with the substrate to improve
bonding between the components and reduce the likelihood of certain
failure mechanisms. The embodiments herein include a combination of
features not previously recognized including the provision of a
cutting table including a superabrasive layer with an abrasive
insert having unique surface features and employing abrasive grit
in a matrix material. Such features facilitate the formation of
cutting elements using less precious materials, while maintaining
cutting ability and having suitable resistance to thermally-induced
and mechanically induced failure mechanisms. The cutting elements
herein may be particularly suitable for use in impreg drill bits
and PDC drill bits. The cutting elements may be suitable for impreg
drill bits designed to drill through soft formations transitioning
to harder formations. For instance, in transitioning from soft
formations to harder formations, the superabrasive portion of the
cutting table may be worn in an initial drilling operation and as
the surface wears to expose the abrasive insert, the drill bit may
be capable of functioning more like an impregnated drill bit
capable of moving through the harder formations. PDC drill bits may
utilize such cutting elements as backup cutters, or peripheral
cutters proximate to the gauge pads. Notably, such cutting elements
may be utilized as rubbing or depth of cut limiting devices,
strategically positioned on the drill bit at the cone, nose, or
shoulder regions.
[0061] The above-disclosed subject matter is to be considered
illustrative, and not restrictive, and the appended claims are
intended to cover all such modifications, enhancements, and other
embodiments, which fall within the true scope of the present
invention. Thus, to the maximum extent allowed by law, the scope of
the present invention is to be determined by the broadest
permissible interpretation of the following claims and their
equivalents, and shall not be restricted or limited by the
foregoing detailed description.
[0062] The Abstract of the Disclosure is provided to comply with
Patent Law and is submitted with the understanding that it will not
be used to interpret or limit the scope or meaning of the claims.
In addition, in the foregoing Detailed Description of the Drawings,
various features may be grouped together or described in a single
embodiment for the purpose of streamlining the disclosure. This
disclosure is not to be interpreted as reflecting an intention that
the claimed embodiments require more features than are expressly
recited in each claim. Rather, as the following claims reflect,
inventive subject matter may be directed to less than all features
of any of the disclosed embodiments. Thus, the following claims are
incorporated into the Detailed Description of the Drawings, with
each claim standing on its own as defining separately claimed
subject matter.
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