U.S. patent application number 17/613772 was filed with the patent office on 2022-07-21 for a cutting element and methods of making same.
The applicant listed for this patent is Element Six (UK) Limited, Element Six US Corporation. Invention is credited to Richard Stuart BALMER, Branislav DZEPINA, Maweja KASONDE, Jonathan Christopher NEWLAND, Roger William Nigel NILEN, Tanmay RAJPATHAK.
Application Number | 20220228443 17/613772 |
Document ID | / |
Family ID | |
Filed Date | 2022-07-21 |
United States Patent
Application |
20220228443 |
Kind Code |
A1 |
KASONDE; Maweja ; et
al. |
July 21, 2022 |
A CUTTING ELEMENT AND METHODS OF MAKING SAME
Abstract
A cutting element (30) includes a substrate (40) having a
peripheral side edge, the peripheral side edge having an associated
radius of curvature; and a body of superhard polycrystalline
material bonded to the substrate along an interface, the body of
superhard polycrystalline material (39) having a peripheral side
edge and a longitudinal axis. The body of superhard polycrystalline
material (39) has a working surface (54); and a plurality of spaced
apart cutting edges extending to the working surface (54) through
respective chamfer portions (62), the cutting edges (61, 76) being
spaced around the working surface by a further region. The cutting
edges (61, 76) have an associated radius of curvature, the radius
of curvature of one or more of the cutting edges being less than
the radius of curvature of the substrate. A method of making such a
cutting element is also disclosed.
Inventors: |
KASONDE; Maweja;
(Oxfordshire, GB) ; NILEN; Roger William Nigel;
(Oxfordshire, GB) ; BALMER; Richard Stuart;
(Oxfordshire, GB) ; DZEPINA; Branislav;
(Oxfordshire, GB) ; NEWLAND; Jonathan Christopher;
(Oxfordshire, GB) ; RAJPATHAK; Tanmay; (Spring,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Element Six (UK) Limited
Element Six US Corporation |
Oxfordshire
Spring |
TX |
GB
US |
|
|
Appl. No.: |
17/613772 |
Filed: |
June 3, 2020 |
PCT Filed: |
June 3, 2020 |
PCT NO: |
PCT/EP2020/065389 |
371 Date: |
November 23, 2021 |
International
Class: |
E21B 10/567 20060101
E21B010/567; E21B 10/43 20060101 E21B010/43 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 4, 2019 |
GB |
1907976.3 |
Claims
1. A cutting element comprising: a substrate having a peripheral
side edge, the peripheral side edge having an associated radius of
curvature; and a body of superhard polycrystalline material bonded
to the substrate along an interface, the body of superhard
polycrystalline material having a peripheral side edge and a
longitudinal axis; wherein: the body of superhard polycrystalline
material comprises: a working surface; and a plurality of spaced
apart cutting edges extending to the working surface through
respective chamfer portions, the cutting edges being spaced around
the working surface by a further region; wherein the cutting edges
have an associated radius of curvature, the radius of curvature of
one or more of the cutting edges being less than the radius of
curvature of the substrate.
2. A cutting element according to claim 1, further comprising a
protrusion or recessed region extending from the working surface
about a central longitudinal axis of the cutting element.
3. The cutting element of claim 1, wherein the body of superhard
polycrystalline material comprises any one or more of
polycrystalline diamond, diamond-like carbon, or cubic boron
nitride of natural and/or synthetic origin.
4. The cutting element of claim 1, comprising three or more cutting
edges.
5. The cutting element of claim 1 wherein the working surface
comprises an undulating topology.
6. The cutting element of claim 1, wherein the working surface
comprises a recessed region extending to a position between around
0.5 mm to around 2 mm above the interface between the body of
superhard polycrystalline material and the substrate.
7. The cutting element of claim 1, wherein the chamfers extend at
an inclined angle to the plane along which the longitudinal axis of
the cutting element extends.
8. The cutting element of claim 1, wherein the body of superhard
polycrystalline material comprises polycrystalline diamond material
having inter-bonded diamond grains with interstitial spaces between
the inter-bonded diamond grains, at least a portion of the
interstitial spaces being substantially free of metal solvent
catalyst material.
9. The cutting element of claim 1, wherein the radius of curvature
of one or more of the cutting edges is between around 2 mm to
around 16 mm.
10. (canceled)
11. (canceled)
12. (canceled)
13. The cutting element of claim 1, wherein the working surface has
a central recess therein having a depth in a plane parallel to the
longitudinal axis of the cutting element measured from the highest
point on the working surface to the bottom of the recess of between
around 0.5 mm to around 2.5 mm; and/or the distance along said axis
from the bottom of the central recess to the interface with the
substrate is between around 1 to around 2 mm.
14. The cutting element of claim 1, wherein the further region
between the plurality of spaced apart cutting edges extends between
the working surface and the peripheral side edge of the body of
superhard polycrystalline material, the further region being
arcuate in a plane parallel to the longitudinal axis.
15. The cutting element of claim 14, wherein the further region is
concave in a plane parallel to the longitudinal axis.
16. An earth-boring tool, comprising: a body; and at least one
cutting element according to claim 1 attached to the body.
17. A method of making the cutting element of claim 1 comprising:
providing a mass of particles or grains of superhard material to
form a pre-sinter assembly; and treating the pre-sinter assembly in
the presence of a catalyst/solvent material for the superhard
grains at an ultra-high pressure of around 5.5 GPa or greater and a
temperature at which the superhard material is more
thermodynamically stable than graphite to sinter together the
grains of superhard material to form the cutting element.
18. A method according to claim 17, wherein the step of providing a
mass of grains of superhard material comprises providing a mass of
diamond grains to form a body of polycrystalline diamond
material.
19. (canceled)
20. (canceled)
21. A method according to claim 17, wherein the step of treating
the pre-sinter assembly comprises treating the pre-sinter assembly
in a canister that is shaped to create any one or more of the
plurality of spaced apart cutting edges extending to the working
surface through respective chamfer portions, the topology of the
working surface, or the topology of the peripheral side
surface.
22. A method according to claim 17, further comprising processing
the cutting element after the step of treating the pre-sinter
assembly to create any one or more of the plurality of spaced apart
cutting edges extending to the working surface through respective
chamfer portions, the topology of the working surface, or the
topology of the peripheral side surface, wherein the step of
processing comprises using any one or more of laser ablation or EDM
machining.
23. (canceled)
24. (canceled)
25. (canceled)
26. (canceled)
27. A drill bit or a component therefor comprising the cutting
element according to claim 1.
Description
FIELD
[0001] This disclosure relates generally to a cutting element, for
example formed of a super-hard polycrystalline construction that
may be used, for example, as a cutting element for drilling in the
oil and gas industry or as an insert for machine tools, and to
methods for making the same.
BACKGROUND
[0002] In various fields such as earth-boring, road milling, and
mining tough materials such as rock, asphalt, or concrete are
engaged and degraded using cutting elements that are typically
coupled to a movable body such as a drill bit secured to a drill
string to bring the cutting elements into contact with the material
to be degraded as the body moves. For example, when exploring for
or extracting subterranean oil, gas, or geothermal energy deposits,
a plurality of cutting elements are typically secured to a drill
bit attached to the end of a drill string and as the drill bit is
rotated, the cutting elements degrade a subterranean formation
forming a wellbore, which allows the drill bit to advance through
the formation. In another example, when preparing an asphalt road
for resurfacing, cutting elements are typically coupled to tips of
picks that may be connected to a rotatable drum. As the drum is
rotated, the cutting elements degrade the asphalt leaving a surface
ready for application of a fresh layer.
[0003] The cutting elements used in such applications often include
super-hard materials, such as polycrystalline diamond material,
sintered to a substrate material such as tungsten carbide, in a
high-pressure, high-temperature environment. These cutting elements
typically include a cutting edge formed in the super-hard material
designed to scrape against and shear away a surface. While
effective in cutting formation or other materials, such cutting
elements may be susceptible to chipping, cracking, or partial
fracturing when subjected to high forces.
[0004] In, for example, drilling operations, a cutting element,
also termed an insert, is subjected to heavy loads and high
temperatures at various stages of its useful life. In the early
stages of drilling, when the sharp cutting edge of the insert
contacts the subterranean formation, it is subjected to large
contact pressures. This results in the possibility of a number of
fracture processes such as fatigue cracking being initiated. As the
cutting edge of the insert wears, the contact pressure decreases
and is generally too low to cause high energy failures. However,
this pressure can still propagate cracks initiated under high
contact pressures and may eventually result in spalling-type
failures. In the drilling industry, PCD cutter performance is
determined by a cutter's ability to achieve high penetration rates
in increasingly demanding environments, and still retain a good
condition post-drilling (enabling re-use if desired). In any
drilling application, cutters may wear through a combination of
smooth, abrasive type wear and spalling/chipping type wear. Whilst
a smooth, abrasive wear mode is desirable because it delivers
maximum benefit from the highly wear-resistant PCD material,
spalling or chipping type wear is unfavourable. Even fairly minimal
fracture damage of this type can have a deleterious effect on both
cutting life and performance.
[0005] Cutting efficiency may be rapidly reduced by spalling-type
wear as the rate of penetration of the drill bit into the formation
is slowed. Once chipping begins, the amount of damage to the
diamond table continually increases, as a result of the increased
normal force required to achieve a given depth of cut. Therefore,
as cutter damage occurs and the rate of penetration of the drill
bit decreases, the response of increasing weight on bit may quickly
lead to further degradation and ultimately catastrophic failure of
the chipped cutting element.
[0006] It has been appreciated that cutting elements and machine
tool cutting inserts having cutting surfaces with non-planar,
shaped topographies or topologies may be advantageous in various
applications. In particular, the surface features and/or shape of
the cutting surface may be beneficial in use to divert, for
example, chips from the working surface being worked on by the
cutter or machine tool, and/or in some instances to act as a chip
breaker, with a view to reducing the risk of chipping, or cracking,
thereby extending the working life of the cutting element.
[0007] There is a need to provide super-hard inserts such as
inserts for cutting or machine tools having effective performance
and enhanced resistance to chipping or spalling.
SUMMARY
[0008] Viewed from a first aspect there is provided a cutting
element comprising:
[0009] a substrate having a peripheral side edge, the peripheral
side edge having an associated radius of curvature; and
[0010] a body of superhard polycrystalline material bonded to the
substrate along an interface, the body of superhard polycrystalline
material having a peripheral side edge; wherein:
[0011] the body of superhard polycrystalline material
comprises:
[0012] a working surface; and
[0013] a plurality of spaced apart cutting edges extending to the
working surface through respective chamfer portions, the cutting
edges being spaced around the working surface; wherein
[0014] the cutting edges have an associate radius of curvature, the
radius of curvature of one or more of the cutting edges being less
than the radius of curvature of the substrate.
[0015] Viewed from a second aspect there is provided a method of
making the cutting element defined above comprising:
[0016] providing a mass of particles or grains of superhard
material to form a pre-sinter assembly; and
[0017] treating the pre-sinter assembly in the presence of a
catalyst/solvent material for the superhard grains at an ultra-high
pressure of around 5.5 GPa or greater and a temperature at which
the superhard material is more thermodynamically stable than
graphite to sinter together the grains of superhard material to
form the cutting element.
[0018] Viewed from a yet further aspect there is provided a drill
bit or a component of a drill bit for boring into the earth,
comprising one or more of the above defined cutting elements.
[0019] In examples where the insert is used as a cutting element,
for example for drilling in the oil and gas industry, the shape of
the cutting element and any surface topography may be used to
direct or divert the rock or earth away from the drill bit to which
the cutter is attached. Alternatively or additionally, for such
uses or when used as an insert for a machine tool for machining a
work piece, the shape and surface topography may act as a chip
breaker suitable for controlling aspects of the size and shape of
chips formed in use.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Various examples are now described with reference to the
accompanying drawings in which:
[0021] FIG. 1 is a schematic drawing of a conventional PCD compact
comprising a PCD structure bonded to a substrate;
[0022] FIG. 2 is a schematic drawing of the microstructure of a
conventional body of PCD material;
[0023] FIG. 3 is a schematic drawing of a conventional PCD compact
comprising a PCD structure bonded to a substrate having a chamfered
peripheral edge to act as a cutting edge;
[0024] FIG. 4 is a schematic perspective view from above of a
cutting element according to a first example;
[0025] FIG. 5 is a further schematic perspective view from above of
the cutting element of FIG. 4;
[0026] FIG. 6 is a plan view of the cutting element of FIG. 4;
[0027] FIG. 7 is a schematic perspective view from above of a
cutting element according to a second example;
[0028] FIG. 8 is a plan view of the cutting element of FIG. 7;
[0029] FIG. 9 is a plot showing the results of a vertical borer
test comparing an example cutting element with a conventional PCD
cutter element; and
[0030] FIG. 10 is schematic perspective view from above of a
cutting element according to a further example.
DETAILED DESCRIPTION
[0031] Referring in general to the following description and
accompanying drawings, various versions of the present disclosure
are described and illustrated to show its structure and method of
operation. Common elements of the illustrated examples are
designated by the same reference numerals.
[0032] As used herein, "drill bit" means and includes any type of
bit or tool used for drilling during the formation or enlargement
of a wellbore in subterranean formations and includes, for example,
fixed cutter bits, rotary drill bits, percussion bits, core bits,
eccentric bits, bi-center bits, reamers, mills, drag bits, roller
cone bits, hybrid bits and other drilling bits and tools known in
the art.
[0033] As used herein, a "superhard material" is a material having
a Vickers hardness of at least about 28 GPa. Diamond and cubic
boron nitride (cBN) material are examples of superhard
materials.
[0034] As used herein, a "superhard construction" means a
construction comprising a body of polycrystalline superhard
material. In such a construction, a substrate may be attached
thereto.
[0035] As used herein, polycrystalline diamond (PCD) is a type of
polycrystalline superhard (PCS) material comprising a mass of
diamond grains, a substantial portion of which are directly
inter-bonded with each other and in which the content of diamond is
at least about 80 volume percent of the material. In one example of
PCD material, interstices between the diamond grains may be at
least partly filled with a binder material comprising a catalyst
for diamond. As used herein, "interstices" or "interstitial
regions" are regions between the diamond grains of PCD material. In
examples of PCD material, some or all interstices or interstitial
regions may be substantially or partially filled with a material
other than diamond, or they may be substantially empty. PCD
material may comprise at least a region from which catalyst
material has been removed from the interstices, leaving
interstitial voids between the diamond grains.
[0036] Cutter elements for use in drill bits in the oil and gas
industry typically comprise a layer of polycrystalline diamond
(PCD) bonded to a cemented carbide substrate. PCD material is
typically made by subjecting an aggregated mass of diamond
particles or grains to an ultra-high pressure of greater than about
5 GPa, and temperature of at least about 1200.degree. C., typically
about 1440.degree. C., in the presence of a sintering aid, also
referred to as a solvent-catalyst material for diamond.
Solvent-catalyst materials for diamond are understood to be
materials that are capable of promoting direct inter-growth of
diamond grains at a pressure and temperature condition at which
diamond is thermodynamically more stable than graphite.
[0037] Examples of solvent-catalyst materials for diamond are
cobalt, iron, nickel and certain alloys including alloys of any of
these elements.
[0038] As used herein, PCBN (polycrystalline cubic boron nitride)
material refers to a type of superhard material comprising grains
of cubic boron nitride (cBN) dispersed within a matrix comprising
metal or ceramic.
[0039] The term "substrate" as used herein means any substrate over
which the superhard material layer is formed. For example, a
"substrate" as used herein may be a transition layer formed over
another substrate.
[0040] The superhard construction shown in the figures may be
suitable, for example, for use as a cutter insert for a drill bit
for boring into the earth. Such an earth-boring drill bit (not
shown) includes a plurality of cutting elements, and typically
includes a bit body which may be secured to a shank by way of a
threaded connection and/or a weld extending around the earth-boring
drill bit on an exterior surface thereof along an interface between
the bit body and the shank. A plurality of cutting elements are
attached to a face of the bit body, one or more of which may
comprise a cutting element as described herein in further detail
below.
[0041] FIGS. 1 and 2 show a conventional polycrystalline composite
construction 1, 1' for use as a cutter insert for a drill bit (not
shown) for boring into the earth. The polycrystalline composite
compact or construction 1, 1' comprises a body of polycrystalline
super hard material 2, 2' integrally bonded at an interface 12 to a
substrate 10. The super hard material may be, for example,
polycrystalline diamond (PCD) and the super hard particles or
grains may be of natural or synthetic origin.
[0042] The substrate 10 may be formed of a hard material such as a
cemented carbide material and may be, for example, cemented
tungsten carbide. The binder metal for such carbides suitable for
forming the substrate 10 may be, for example, nickel, cobalt, iron
or an alloy containing one or more of these metals. Typically, this
binder will be present in an amount of 10 to 20 mass %, but this
may be as low as 6 mass % or less. Some of the binder metal may
infiltrate the body of polycrystalline super hard material 2,
2'during formation of the compact 1, 1'.
[0043] As shown in FIG. 2, during formation of the polycrystalline
composite construction 1, 1', the interstices 24 between the grains
22 of super hard material such as diamond grains in the case of
PCD, may be at least partly filled with a non-super hard phase
material. This non-super hard phase material, also known as a
filler material may comprise residual catalyst/binder material, for
example cobalt, nickel or iron.
[0044] The polycrystalline composite construction 1, 1' when used
as a cutting element may be mounted in use in a bit body, such as a
drag bit body (not shown).
[0045] The substrate 10 may be, for example, generally cylindrical
having a peripheral surface 3, a peripheral top edge 8 and a distal
free end.
[0046] The exposed surface of the super hard material 4 opposite
the substrate 10 forms or comprises a working surface which also
acts as a rake face in use. In some conventional cutting elements
such as that shown in FIG. 3, a chamfer 28 typically extends
between the working surface 4 and a cutting edge 6, and at least a
part of a flank or barrel 2 of the cutting element, the cutting
edge 36 being defined by the edge of the chamfer 28 and the flank
2.
[0047] The working surface or "rake face" 4 of the polycrystalline
composite construction 1, 1' is the surface or surfaces over which
the chips of material being cut flow when the cutter is used to cut
material from a body, the rake face 4 directing the flow of newly
formed chips. This face 4 is commonly also referred to as the top
face or working surface of the cutting element as the working
surface 4 is the surface which, along with its edge 6, is intended
to perform the cutting of a body in use. It is understood that the
term "cutting edge", as used herein, refers to the actual cutting
edge, defined functionally as above, at any particular stage or at
more than one stage of the cutter wear progression up to failure of
the cutter, including but not limited to the cutter in a
substantially unworn or unused state.
[0048] As used herein, "chips" are the pieces of a body removed
from the work surface of the body being cut by the polycrystalline
composite construction 1, 1' in use.
[0049] As used herein, the "flank" 2 of the cutter is the surface
or surfaces of the cutter that passes over the surface produced on
the body of material being cut by the cutter and is commonly
referred to as the side or barrel of the cutter. The flank 2 may
provide a clearance from the body and may comprise more than one
flank face.
[0050] As used herein, a "wear scar" is a surface of a cutter
formed in use by the removal of a volume of cutter material due to
wear of the cutter. A flank face may comprise a wear scar. As a
cutter wears in use, material may progressively be removed from
proximate the cutting edge, thereby continually redefining the
position and shape of the cutting edge, rake face and flank as the
wear scar forms.
[0051] With reference to FIG. 3, the chamfer 28 is formed in the
structure adjacent the cutting edge 6 and flank or barrel surface
2.
[0052] The rake face 4 is joined to the flank 2 by the chamfer 28
which extends from the cutting edge 6 to the rake face 4, and lies
in a plane at a predetermined angle to the plane perpendicular to
the plane in which the longitudinal axis of the cutter extends. In
some examples, this chamfer angle is up to around 45 degrees. The
vertical height of the chamfer 28 may be, for example, between 350
.mu.m and 450 .mu.m, such as around 400 .mu.m.
[0053] The conventional cutting elements shown in FIG. 1 to 3 are
typically cylindrical in shape with a substantially planar cutting
surface 4.
[0054] A cutting element 30 according to a first example is shown
in FIGS. 4 to 6 and comprises a body of polycrystalline super hard
material 39 integrally bonded at an interface 44 to a substrate 40.
The super hard material 39 may be, for example, polycrystalline
diamond (PCD) and the super hard particles or grains may be of
natural or synthetic origin.
[0055] The substrate 40 may be formed of a hard material such as a
cemented carbide material and may be, for example, cemented
tungsten carbide, cemented tantalum carbide, cemented titanium
carbide, cemented molybdenum carbide or mixtures thereof. The
binder metal for such carbides suitable for forming the substrate
40 may be, for example, nickel, cobalt, iron or an alloy containing
one or more of these metals. Typically, this binder will be present
in an amount of 10 to 20 mass %, but this may be as low as 6 mass %
or less.
[0056] The substrate 40 may be, for example, generally cylindrical
having a peripheral surface 33, a peripheral top edge 44 and a
distal free end.
[0057] The body of superhard material 39 comprises a substantially
cylindrical first region 42 bonded to the substrate 40 along the
interface 44. A further region 46 extends therefrom to an exposed
surface of the super hard material 34 opposite the substrate 40
which forms or comprises a working surface, also termed a cutting
face which also acts as a rake face in use. This working surface
has a central portion which is substantially non-planar and may, in
some examples, be concave, or convex or have one or more regions
that include both a concave and a convex portion to form an
undulating profile. The further region 46 has an undulating
peripheral surface which may assist in reducing drag on the lateral
surface of the cutting element in use and to improve cutting
efficiency by controlling chip flow over the external surfaces of
the cutting element 30.
[0058] A plurality of curved cutting edges 41 are spaced from one
another around the working surface 34 and are formed by the bottom
of a respective chamfer portion 37 extending between the working
surface 34 and further region 46 of the body of superhard material,
the cutting edges 41 being defined by the edge of the chamfer 37
and the top 38 of the further region 46.
[0059] 1. The cutting edges 41 are spaced from each other by a
respective interconnecting region such that the cutting edges 41
form lobes 36 extending from the working surface 34. A fillet
portion 43 may extend from each interconnecting region terminating
at or proximate the interface 38 between the first region 42 and
further region 46 of the body of superhard material. In some
examples, the fillet portion 43 and interconnecting region between
the plurality of spaced apart cutting edges which extend between
the working surface and the peripheral side edge of the body of
superhard polycrystalline material may be arcuate in a plane
parallel to the longitudinal axis, for example concave.
[0060] In some examples, the central portion of the working surface
34 comprises a concavity extending into the body of superhard
material but terminating above the interface with the substrate
40.
[0061] In some examples, the depth of the first region 42 is
between around 1 mm to around 2 mm.
[0062] FIGS. 7, 8 and 10 show further example cutting elements 50,
70 which differ from that shown in FIGS. 4 to 6 in that the radii
of curvature of the cutting edges 61, 76 is smaller in the examples
of FIGS. 7, 8 and 10 than the first example of FIGS. 4 to 6.
[0063] In the example of FIGS. 7 and 8, the cutting element 50
comprises a body of polycrystalline super hard material 56
integrally bonded at an interface 58 to a substrate 60. The super
hard material 56 may be, for example, polycrystalline diamond (PCD)
and the super hard particles or grains may be of natural or
synthetic origin.
[0064] As in the first example, the substrate 60 may be formed of a
hard material such as a cemented carbide material and may be, for
example, cemented tungsten carbide, cemented tantalum carbide,
cemented titanium carbide, cemented molybdenum carbide or mixtures
thereof. The binder metal for such carbides suitable for forming
the substrate 60 may be, for example, nickel, cobalt, iron or an
alloy containing one or more of these metals. Typically, this
binder will be present in an amount of 10 to 20 mass %, but this
may be as low as 6 mass % or less.
[0065] The substrate 60 may be, for example, generally cylindrical
having a peripheral surface 55, a peripheral top edge 58 and a
distal free end.
[0066] The body of superhard material 56 comprises a region 57
extending from the interface 58 with the substrate 60 to an exposed
surface of the super hard material 54 opposite the substrate 60
which forms or comprises a working surface, also termed a cutting
face which also acts as a rake face in use. This working surface 54
has a central portion which is substantially non-planar and may, in
some examples, be concave, or convex or have one or more regions
that include both a concave and a convex portion to form an
undulating profile. The region 57 has an undulating peripheral
surface which may assist in reducing drag on the lateral surface of
the cutting element in use and to improve cutting efficiency by
controlling chip flow over the external surfaces of the cutting
element 50.
[0067] A plurality of curved cutting edges 61 are spaced from one
another around the working surface 54 and are formed by the bottom
of a respective chamfer portion 62 extending between the working
surface 54 and the region 57 of the body of superhard material 56,
the cutting edges 61 being defined by the edge of the chamfer 62
and the working surface 54.
[0068] 2. The cutting edges 61 are spaced from each other by a
respective interconnecting region such that the cutting edges 61
form lobes 63 extending from the working surface 54. A fillet
portion 53 may extend from each interconnecting region terminating
at or proximate the interface 58 between the body of superhard
material 56 and the substrate 60. In some examples, the fillet
portion 53 and interconnecting region between the plurality of
spaced apart cutting edges which extend between the working surface
and the peripheral side edge of the body of superhard
polycrystalline material may be arcuate in a plane parallel to the
longitudinal axis, for example concave.
[0069] In some examples, the central portion of the working surface
54 comprises a concavity extending into the body of superhard
material but terminating above the interface with the substrate
60.
[0070] In the example of FIG. 10, the cutting element 70 comprises
a body of polycrystalline super hard material 75 integrally bonded
at an interface 73 to a substrate 71. The super hard material 75
may be, for example, polycrystalline diamond (PCD) and the super
hard particles or grains may be of natural or synthetic origin.
[0071] As in the first example, the substrate 71 may be formed of a
hard material such as a cemented carbide material and may be, for
example, cemented tungsten carbide, cemented tantalum carbide,
cemented titanium carbide, cemented molybdenum carbide or mixtures
thereof. The binder metal for such carbides suitable for forming
the substrate 71 may be, for example, nickel, cobalt, iron or an
alloy containing one or more of these metals. Typically, this
binder will be present in an amount of 10 to 20 mass %, but this
may be as low as 6 mass % or less.
[0072] The substrate 71 may be, for example, generally cylindrical
having a peripheral surface, a peripheral top edge and a distal
free end.
[0073] The body of superhard material comprises a region 72
extending from the interface 73 with the substrate 71 to an exposed
surface of the super hard material 74 opposite the substrate 71
which forms or comprises a working surface, also termed a cutting
face which also acts as a rake face in use. This working surface 74
has a central portion 77 which is substantially non-planar and may,
in some examples, be concave, or convex or have one or more regions
that include both a concave and a convex portion to form an
undulating profile.
[0074] A plurality of curved cutting edges 75 are spaced from one
another around the working surface 74 and are formed by the bottom
of a respective chamfer portion 76 extending between the working
surface 74 and the region 72 of the body of superhard material, the
cutting edges 75 being defined by the edge of the chamfer 76 and
the working surface 74.
[0075] The cutting edges 75 are spaced from each other by a
respective interconnecting region 78 such that the cutting edges 75
form lobes extending from the working surface 74. The
interconnecting region 78 may have an undulating peripheral surface
which may assist in reducing drag on the lateral surface of the
cutting element in use and to improve cutting efficiency by
controlling chip flow over the external surfaces of the cutting
element 70. In particular, the region 78 which extends between the
working surface 74 and the region 72 may be arcuate, for example
concave, in a plane parallel to the longitudinal axis.
[0076] In some examples, such as those shown in FIGS. 4 to 8 and
10, the depth along a central longitudinal axis of the cutting
element 30, 50, 70 of the concave central feature in the working
surface 34, 54, 74 may be up to around 1mm. In examples, the
central feature is convex, and the height along a central
longitudinal axis of the cutting element 30, 50, 70 of the convex
central feature protruding from the working surface 34, 54, 74 may
be up to around 1 mm.
[0077] In the examples, the radius of curvature of the cutting
edges 41, 61, 75 is less than the radius of curvature of the
substrate 40, 60, 71 (and, in the example of FIGS. 4 to 6, the
first region 42) which may improve the rate of penetration of the
cutting element in use. As an illustration, the radius of curvature
of the cutting edges 41, 61, 75 may, in some examples, be between
around 2 mm to around 16 mm. By way of further example, for a
cutting element 30, 50, 70 in which substrate 40, 60, 71 has a
diameter of around 16 mm, the radius of curvature of one or more of
the cutting edges 41, 61, 75 may be between around 4 mm to around
12 mm; for a cutting element in which the substrate 40, 60, 71 has
a diameter of around 19 mm, the radius of curvature of one or more
of the cutting edges 41, 61, 75 may be between around 6 mm to
around 14 mm; and for a cutting element in which the substrate 40,
60, 71 has a diameter of around 13 mm, the radius of curvature of
one or more of the cutting edges 41, 61, 75 may be between around 3
mm to around 9 mm.
[0078] In some examples, the depth of the central recess in the
working surface 34, 54, 74 in a plane parallel to the longitudinal
axis of the cutting element 30, 50, 70 measured from the highest
point on the working surface 34, 54, 74 to the bottom of the recess
is between around 0.5 mm to around 2.5 mm, and the distance along
said axis from the bottom of the central recess to the interface
44, 58, 73 with the substrate 40, 60, 71 is between around 1 to
around 2 mm, and in some examples is at least around 1.4 mm.
[0079] The wear resistance of the example cutting elements 30, 50,
70 were tested against conventional polycrystalline diamond cutting
elements having the same average grain size of diamond grains as
the super hard grains in the example constructions 30, 50, 70 and
sintered under pressure of around 6.8 GPa. The tests performed
included vertical boring mill tests. The results are shown in FIG.
9 and provide an indication of the total wear scar area plotted
against cutting length. It was seen that the wear resistance of the
example constructions was better than that of the conventional PCD
cutting elements bonded to a WC substrate in which the PCD layer
had the same average grain size as the PCD layer of the examples
and same PCD layer thickness. None of the cutting elements had been
subjected to an acid leaching treatment to remove residual catalyst
from the PCD regions.
[0080] An example method of preparing the cutting element of FIGS.
4 to 8 and 10 is as follows. A pre-sinter mixture was prepared by
combining a mass of diamond particles with a non-diamond phase
mixture designed to act as a solvent/catalyst for diamond, such as
cobalt, and to form up to around 20 wt % in the sintered product.
The pre-sinter mixture was loaded into a cup and placed in an HP/HT
reaction cell assembly together with a mass of carbide to form the
substrate. The contents of the cell assembly were subjected to
HP/HT processing. The HP/HT processing conditions selected were
sufficient to effect inter-crystalline bonding between adjacent
grains of diamond particles and the joining of sintered particles
to the cemented metal carbide support to form a PCD construction
comprising a PCD structure integrally formed on and bonded to the
cemented tungsten carbide substrate. In one example, the processing
conditions generally involved the imposition for about 3 to 120
minutes of a temperature of at least about 1200 degrees C. and a
super high pressure of greater than about 5 GPa. In some examples,
the pre-sinter assembly may be subjected to a pressure of at least
about 6 GPa, at least about 6.5 GPa, at least about 7 GPa or even
at least about 7.5 GPa or more, at a temperature of around 1440 deg
C.
[0081] In some examples, both the bodies of, for example, diamond
and carbide material plus sintering aid/binder/catalyst are applied
as powders and sintered simultaneously in a single UHP/HT
process.
[0082] In another example, the substrate may be pre-sintered in a
separate process before being bonded to the superhard material in
the HP/HT press during sintering of the superhard polycrystalline
material.
[0083] In some examples, the cemented carbide substrate 40, 60, 71
may be formed of tungsten carbide particles bonded together by the
binder material, the binder material comprising an alloy of any one
or more of Co, Ni and Cr. The tungsten carbide particles may form
at least 70 weight percent and at most 95 weight percent of the
substrate.
[0084] After sintering, the PCD constructions 30, 50, 70 were
subjected to further treatment to remove the canister material.
[0085] In some examples, the canister may be shaped to create one
or more of the concave or convex central portion in the working
surface 34, 54, 74 the chamfers 37, 62, to create the cutting edges
41, 61, 75 and the undulating peripheral surface 46, 57, 78 of the
body of superhard material. In other examples, any one or more of
the concave or convex central portion in the working surface 34,
54, 77 the chamfers 37, 62 to create the cutting edges 41, 61, 75
and the undulating peripheral surface 46, 57, 78 may be created
after sintering using additional processing such as laser ablation,
EDM machining another machining process to shape the construction
to the desired cutting element shape and size. Additionally, laser
ablation of different regions of the superhard material/working
surface 34, 54, 74 may be used to create regions of different
surface roughness, for example by ablating using different laser
parameters. This may be used, as desired, to influence chip flow
across the working surface 34, 54, 74 during the cutting
application.
[0086] The number, depth and dimensions of the lobes 36, 56, 75 and
discrete cutting edges 41, 61, 76 may be chosen to suit the desired
application, and in some examples the cutting elements comprise
three or more lobes to provide three or more cutting edges enabling
the cutting element to be spun to increase the working life of the
cutting element and present a new cutting edge to the surface to be
cut.
[0087] In the examples where the body of superhard material
comprises PCD, the PCD material may be, for example, formed of
diamond grains that are of natural and/or synthetic origin.
[0088] The cutting elements 30, 50, 70 of the types shown in FIGS.
4 to 8 and 10 may be provided along blades on the face of a drill
bit body (not shown). The cutting elements may be secured to the
bit body within pockets therein using, for example a conventional
brazing process.
[0089] In some examples, the example constructions may be subjected
to an acid leaching treatment to remove the residual catalyst from
interstitial spaces between the grains of superhard material.
[0090] In use, the cutting element 30, 50, 70 shears away the
surface of the underlying formation and wear scar forms
progressively in the superhard material in the region of the
cutting edge 41, 61, 76. As used herein, a "wear scar" is a surface
of the cutter formed in use by the removal of a volume of cutter
material due to wear of the cutter. As a cutter wears in use,
material may progressively be removed from proximate the cutting
edge, thereby continually redefining the position and shape of the
cutting edge, rake face and flank as the wear scar forms.
[0091] Whilst not wishing to be bound by a particular theory, the
example cutting elements are believed to assist in providing
improved rock cutting efficiency over conventional PCD cutters, as
the geometry of the cutting-edges 41, 61, 76 having a smaller
radius of curvature than the substrate 40, 60, 70 and the
undulating peripheral surface and the undulating working surface
34, 54, 74 is such that the wear scar area will grow at a far
slower rate than for a conventional cylindrical PCD cutter. This is
believed to assist in maintaining a greater load at the cutter-rock
contact point for a longer period, resulting in a slower build up
of thermal loading, both of which are believed to be contributors
to more efficient rock cutting. Also, the undulating working
surface 34, 54, 74 may assist in providing more efficient crushing
and removal of the rock cuttings and chips in application.
[0092] In some examples, the cutting elements may have a generally
cylindrical shape. In other examples, the cutting elements be a
different shape, such as conical, or ovoid.
[0093] In some examples, the body of PCD material may be formed as
a standalone object, that is, a free-standing unbacked body of PCD
material, and may be attached to a substrate in a subsequent
step.
[0094] In some examples, the cutting elements may comprise natural
or synthetic diamond material, or cBN material. Examples of diamond
material include polycrystalline diamond (PCD) material, thermally
stable PCD material, crystalline diamond material, diamond material
made by means of a chemical vapour deposition (CVD) method or
silicon carbide bonded diamond. An example of cBN material is
polycrystalline cubic boron nitride (PCBN).
[0095] It will therefore be seen that various versions of the
present disclosure include cutting elements and methods of forming
same for earth-boring drill bits which may enhance the working life
of the cutting elements by one or more of improving the abrasion
resistance, thermal stability, durability, sharpness of the cutting
edge, spall resistance, and fracture/impact resistance, potentially
by cutting the rock more efficiently through the rock crushing
action and control of chip and drilling mud flow through the
shapes/topography of the cutting elements and may lead to improved
drill bit stability of, for example, the earth-boring drill bit to
which the cutting elements may be mounted.
[0096] Although the foregoing description contains many specifics,
these are not to be construed as limiting the scope of the present
disclosure, but merely as providing certain exemplary versions.
* * * * *