U.S. patent application number 15/276970 was filed with the patent office on 2017-05-25 for solid pcd cutter.
The applicant listed for this patent is Smith International, Inc.. Invention is credited to Daniel J. Belnap, Yuri Yoris Burhan, Ronald K. Eyre, Yuelin Shen, Jibin Shi, Youhe Zhang.
Application Number | 20170144272 15/276970 |
Document ID | / |
Family ID | 48693951 |
Filed Date | 2017-05-25 |
United States Patent
Application |
20170144272 |
Kind Code |
A1 |
Eyre; Ronald K. ; et
al. |
May 25, 2017 |
SOLID PCD CUTTER
Abstract
A method of forming a cutting element may include placing a
plurality of diamond particles adjacent to a substrate in a
reaction cell and subjecting the plurality of diamond particles to
high pressure high temperature conditions to form a polycrystalline
diamond body. The polycrystalline diamond body may include a
cutting face area to thickness ratio ranging from 60:16 to 500:5.
The polycrystalline diamond body may have at least one dimension
greater than 8 mm.
Inventors: |
Eyre; Ronald K.; (Provo,
UT) ; Belnap; Daniel J.; (Provo, UT) ; Zhang;
Youhe; (Houston, TX) ; Shen; Yuelin; (Katy,
TX) ; Shi; Jibin; (Houston, TX) ; Burhan; Yuri
Yoris; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Smith International, Inc. |
Houston |
TX |
US |
|
|
Family ID: |
48693951 |
Appl. No.: |
15/276970 |
Filed: |
September 27, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13719326 |
Dec 19, 2012 |
9482056 |
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15276970 |
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61581707 |
Dec 30, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22C 26/00 20130101;
E21B 10/46 20130101; E21B 10/54 20130101; E21B 10/567 20130101;
C04B 35/52 20130101; B22F 3/14 20130101; B22F 7/008 20130101; B22F
2005/001 20130101; B22F 5/00 20130101; B24D 18/0009 20130101 |
International
Class: |
B24D 18/00 20060101
B24D018/00; E21B 10/567 20060101 E21B010/567 |
Claims
1. A method of forming a cutting element comprising: placing a
plurality of diamond particles adjacent to a substrate in a
reaction cell; and subjecting the plurality of diamond particles to
high pressure high temperature conditions to form a polycrystalline
diamond body; wherein the polycrystalline diamond body comprises a
cutting face area to thickness ratio ranging from 60:16 to 500:5;
and wherein the polycrystalline diamond body has at least one
dimension greater than 8 mm.
2. The method of claim 1, further comprising leaching at least part
of the polycrystalline diamond body.
3. The method of claim 2, wherein the entire polycrystalline
diamond body is leached to form a thermally stable polycrystalline
diamond body.
4. The method of claim 1, further comprising removing the
substrate.
5. The method of claim 1, wherein the substrate comprises a first
region adjacent to the diamond body and at least one additional
region adjacent to the first region opposite from the diamond body,
wherein the first region comprises hard particles having a smaller
median grain size than hard particles of the at least one
additional region.
6. The method of claim 1, further comprising placing a layer of
carbide powder between the substrate and the plurality of diamond
particles.
7. The method of claim 1, wherein the step of placing further
comprises mixing boron powder with the plurality of diamond
particles.
8. The method of claim 1, wherein the polycrystalline diamond body
has a bulk thermal conductivity of greater than 200 W/mK.
9. The method of claim 1, wherein a carbonate solvent catalyst is
provided with the plurality of diamond particles in the reaction
cell.
10. A method of forming a cutting element comprising: placing a
plurality of first diamond particles and a catalyst material source
in a reaction cell; and subjecting the plurality of diamond
particles to high pressure high temperature conditions to form a
first polycrystalline diamond body; and performing a second
sintering process comprising: assembling a second volume comprising
diamond particles adjacent to the first polycrystalline diamond
body; and subjecting the second volume and the first
polycrystalline diamond body to high pressure high temperature
conditions to form a second polycrystalline diamond body.
11. The method of claim 10, wherein the second polycrystalline
diamond body has at least one dimension greater than 8 mm.
12. The method of claim 10, further comprising a third sintering
process comprising: assembling a third volume comprising diamond
particles adjacent to the second polycrystalline diamond body; and
subjecting the third volume and the second polycrystalline diamond
body to high pressure high temperature conditions to form a third
polycrystalline diamond body.
13. The method of claim 12, further comprising a fourth sintering
process comprising: assembling a fourth volume comprising diamond
particles adjacent to the third polycrystalline diamond body; and
subjecting the fourth volume and the third polycrystalline diamond
body to high pressure high temperature conditions to form a fourth
polycrystalline diamond body.
14. The method of claim 10, wherein the catalyst material source is
a substrate.
15. The method of claim 14, wherein after the step of subjecting
and prior to the step of performing a second sintering process, the
substrate is removed.
16. The method of claim 10, wherein after the step of subjecting
and prior to the step of performing a second sintering process, the
first polycrystalline diamond body is treated.
17. The method of claim 10, wherein the catalyst material source is
a powder provided with the plurality of first diamond
particles.
18. The method of claim 10, wherein the catalyst material source
comprises a carbonate solvent catalyst.
19. The method of claim 10, wherein the second volume comprises
diamond particles larger than the first diamond particles.
20. The method of claim 10, wherein the second volume comprises
diamond particles smaller than the first diamond particles.
21. The method of claim 10, wherein the catalyst material source
forms a core of the second polycrystalline diamond body.
22. A method of forming a cutting element comprising: placing a
plurality of diamond particles adjacent to a substrate in a
reaction cell; and subjecting the plurality of diamond particles to
high pressure high temperature conditions of 1300.degree.
C.-1700.degree. C. and 55 to 90 kbar to form a polycrystalline
diamond body; wherein the substrate comprises a first region
adjacent to the diamond particles and at least one additional
region adjacent to the first region opposite from the diamond
particles, wherein the first region comprises hard particles having
a smaller median grain size than hard particles of the at least one
additional region.
23. The method of claim 22, further comprising leaching at least
part of the polycrystalline diamond body.
24. The method of claim 23, wherein the entire polycrystalline
diamond body is leached to form a thermally stable polycrystalline
diamond body.
25. The method of claim 22, further comprising removing the
substrate.
26. The method of claim 22, further comprising placing a layer of
carbide powder between the substrate and the plurality of diamond
particles.
27. The method of claim 22, wherein the step of placing further
comprises mixing boron powder with the plurality of diamond
particles.
28. The method of claim 22, wherein a carbonate solvent catalyst is
provided with the plurality of diamond particles in the reaction
cell.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 61/581,707, filed on Dec. 30, 2011, and U.S.
application Ser. No. 13/719,326, filed on Dec. 19, 2012, which are
incorporated by reference herein.
BACKGROUND
[0002] Technical Field
[0003] Embodiments disclosed herein relate generally to
polycrystalline diamond cutters. In particular, embodiments
disclosed herein related to bulk polycrystalline diamond bodies for
use in downhole drilling applications.
[0004] Background Art
[0005] Drill bits used to drill wellbores through earth formations
generally are made within one of two broad categories of bit
structures. Depending on the application/formation to be drilled,
the appropriate type of drill bit may be selected based on the
cutting action type for the bit and its appropriateness for use in
the particular formation. Drill bits in the first category are
generally known as "roller cone" bits, which include a bit body
having one or more roller cones rotatably mounted to the bit body.
The bit body is typically formed from steel or another high
strength material. The roller cones are also typically formed from
steel or other high strength material and include a plurality of
cutting elements disposed at selected positions about the cones.
The cutting elements may be formed from the same base material as
is the cone. These bits are typically referred to as "milled tooth"
bits. Other roller cone bits include "insert" cutting elements that
are press (interference) fit into holes formed and/or machined into
the roller cones. The inserts may be formed from, for example,
tungsten carbide, natural or synthetic diamond, boron nitride, or
any one or combination of hard or superhard materials.
[0006] Drill bits of the second category are typically referred to
as "fixed cutter" or "drag" bits. Drag bits, include bits that have
cutting elements attached to the bit body, which may be a steel bit
body or a matrix bit body formed from a matrix material such as
tungsten carbide surrounded by a binder material. Drag bits may
generally be defined as bits that have no moving parts. However,
there are different types and methods of forming drag bits that are
known in the art. For example, drag bits having abrasive material,
such as diamond, impregnated into the surface of the material which
forms the bit body are commonly referred to as "impreg" bits. Drag
bits having cutting elements made of an ultra hard cutting surface
layer or "table" (typically made of polycrystalline diamond
material or polycrystalline boron nitride material) deposited onto
or otherwise bonded to a substrate are known in the art as
polycrystalline diamond compact ("PDC") bits.
[0007] PDC cutters have been used in industrial applications
including rock drilling and metal machining for many years. In PDC
bits, PDC cutters are received within cutter pockets, which are
formed within blades extending from a bit body, and are typically
bonded to the blades by brazing to the inner surfaces of the cutter
pockets. The PDC cutters are positioned along the leading edges of
the bit body blades so that as the bit body is rotated, the PDC
cutters engage and drill the earth formation. In use, high forces
may be exerted on the PDC cutters, particularly in the
forward-to-rear direction. Additionally, the bit and the PDC
cutters may be subjected to substantial abrasive forces. In some
instances, impact, vibration, and erosive forces have caused drill
bit failure due to loss of one or more cutters, or due to breakage
of the blades.
[0008] In a typical PDC cutter, a compact of polycrystalline
diamond ("PCD") (or other superhard material, such as
polycrystalline cubic boron nitride) is bonded to a substrate
material, which is typically a sintered metal-carbide to form a
cutting structure. For example, a typical substrate material may
include tungsten carbide interspersed with a binder component,
preferably cobalt, which binds the tungsten carbide particles
together. PCD comprises a polycrystalline mass of diamond grains or
crystals that are bonded together to form an integral, tough,
high-strength mass or lattice. The resulting PCD structure produces
enhanced properties of wear resistance and hardness, making PCD
materials extremely useful in aggressive wear and cutting
applications where high levels of wear resistance and hardness are
desired.
[0009] An example of a prior art PDC bit having a plurality of
cutters with ultra hard working surfaces is shown in FIGS. 1 and 2.
The drill bit 100 includes a bit body 110 having a threaded upper
pin end 111 and a cutting end 115. The cutting end 115 typically
includes a plurality of ribs or blades 120 arranged about the
rotational axis L (also referred to as the longitudinal or central
axis) of the drill bit and extending radially outward from the bit
body 110. Cutting elements, or cutters, 150 are embedded in the
blades 120 at predetermined angular orientations and radial
locations relative to a working surface and with a desired back
rake angle and side rake angle against a formation to be
drilled.
[0010] A plurality of orifices 116 are positioned on the bit body
110 in the areas between the blades 120, which may be referred to
as "gaps" or "fluid courses." The orifices 116 are commonly adapted
to accept nozzles. The orifices 116 allow drilling fluid to be
discharged through the bit in selected directions and at selected
rates of flow between the blades 120 for lubricating and cooling
the drill bit 100, the blades 120 and the cutters 150. The drilling
fluid also cleans and removes the cuttings as the drill bit 100
rotates and penetrates the geological formation. Without proper
flow characteristics, insufficient cooling of the cutters 150 may
result in cutter failure during drilling operations. The fluid
courses are positioned to provide additional flow channels for
drilling fluid and to provide a passage for formation cuttings to
travel past the drill bit 100 toward the surface of a wellbore (not
shown).
[0011] Referring to FIG. 2, a top view of a prior art PDC bit is
shown. The cutting face 118 of the bit shown includes a plurality
of blades 120, wherein each blade has a leading side 122 facing the
direction of bit rotation, a trailing side 124 (opposite from the
leading side), and a top side 126. Each blade includes a plurality
of cutting elements or cutters generally disposed radially from the
center of cutting face 118 to generally form rows. Certain cutters,
although at differing axial positions, may occupy radial positions
that are in similar radial position to other cutters on other
blades.
[0012] During manufacture of the cutting elements, the materials
are typically subjected to sintering under high pressures and high
temperatures. These manufacturing conditions result in dissimilar
materials being bonded to each other. Because of the different
thermal expansion rates between the diamond layer and the substrate
material, thermal residual stresses are induced on the diamond and
substrate layers, and at the interface there between after cooling.
The residual stress induced on the diamond layer and substrate can
often result in insert breakage, fracture or delamination under
drilling conditions.
[0013] Further, a significant factor in determining the longevity
of PDC cutters is the exposure of the cutter to heat. Conventional
polycrystalline diamond is stable at temperatures of up to
700-750.degree. C. in air, above which observed increases in
temperature may result in permanent damage to and structural
failure of polycrystalline diamond. Exposure to heat (through
brazing the cutters to a cutting tool or through frictional heat
generated from the contact of the cutter with the formation) can
cause thermal damage to the diamond table and eventually result in
the formation of cracks (due to differences in thermal expansion
coefficients) which can lead to spalling of the polycrystalline
diamond layer, delamination between the polycrystalline diamond and
substrate, and conversion of the diamond back into graphite causing
rapid abrasive wear. As a cutting element contacts the formation, a
wear flat develops and frictional heat is induced. As the cutting
element is continued to be used, the wear flat will increase in
size and further induce frictional heat. The heat may build-up that
may cause failure of the cutting element due to thermal mis-match
between diamond and catalyst material used to form the PCD. This is
particularly true for cutters that are immovably attached to the
drill bit, as conventional in the art.
[0014] To minimize these deleterious effects, various prior art
techniques have included keeping the thickness of the
polycrystalline diamond layer to a minimum; use of transition
layers (such as polycrystalline cubic boron nitride, or a mixture
of substrate material and diamond); use of non-planar interfaces,
etc.
[0015] However, there exists a continuing need for improvements in
the material properties of composite materials used for drilling or
cutting tool applications.
SUMMARY OF INVENTION
[0016] This summary is provided to introduce a selection of
concepts that are further described below in the detailed
description. This summary is not intended to identify key or
essential features of the claimed subject matter, nor is it
intended to be used as an aid in limiting the scope of the claimed
subject matter.
[0017] In one aspect, embodiments disclosed herein relate to a
method of forming a cutting element that includes placing a
plurality of diamond particles adjacent to a substrate in a
reaction cell; and subjecting the plurality of diamond particles to
high pressure high temperature conditions to form a polycrystalline
diamond body; wherein the polycrystalline diamond body comprises a
cutting face area to thickness ratio ranging from 60:16 to 500:5;
and wherein the polycrystalline diamond body has at least one
dimension greater than 8 mm.
[0018] In another aspect, embodiments disclosed herein relate to a
cutting element that includes a polycrystalline diamond body,
wherein the polycrystalline diamond body has a cutting face; a
thickness extending from the cutting face; and a cutting face area
to thickness ratio ranging from 60:16 to 500:5; wherein at least
one dimension is greater than or equal to 8 mm.
[0019] In another aspect, embodiments disclosed herein relate to a
drill bit that includes a bit body having a rotational axis
extending there through; at least one cutter pocket formed in the
drill bit; and at least one cutting element positioned in the at
least one cutter pocket, wherein the at least one cutting element
comprises a polycrystalline diamond body, and wherein the
polycrystalline diamond body includes a cutting face; a thickness
extending from the cutting face to a distance within the cutter
pocket; and a cutting face area to thickness ratio ranging from
60:16 to 500:5; wherein at least one dimension is greater than or
equal to 8 mm; and wherein the at least one cutting element is
positioned in the at least one cutter pocket such that the cutting
face faces in the direction of rotation of the drill bit.
[0020] In yet another aspect, embodiments disclosed herein relate
to a method of forming a cutting element that includes placing a
plurality of first diamond particles and a catalyst material source
in a reaction cell; and subjecting the plurality of diamond
particles to high pressure high temperature conditions to form a
first polycrystalline diamond body; and performing a second
sintering process comprising: assembling a second volume comprising
diamond particles adjacent to the first polycrystalline diamond
body; and subjecting the second volume and the first
polycrystalline diamond body to high pressure high temperature
conditions to form a second polycrystalline diamond body.
[0021] In yet another aspect, embodiments disclosed herein relate
to a drill bit that includes a bit body having a rotational axis
extending there through; at least one cutter pocket formed in the
drill bit; and at least one cutting element positioned in the at
least one cutter pocket, wherein the at least one cutting element
comprises a polycrystalline diamond body and has a bulk thermal
conductivity of greater than 100 W/mK; wherein the at least one
cutting element is positioned in the at least one cutter pocket
such that the cutting face faces in the direction of rotation of
the drill bit.
[0022] In yet another aspect, embodiments disclosed herein relate
to a method of forming a cutting element that includes placing a
plurality of diamond particles adjacent to a substrate in a
reaction cell; and subjecting the plurality of diamond particles to
high pressure high temperature conditions of 1300.degree.
C.-1700.degree. C. and 55 to 90 kbar to form a polycrystalline
diamond body; wherein the substrate comprises a first region
adjacent to the diamond particles and at least one additional
region adjacent to the first region opposite from the diamond
particles, wherein the first region comprises hard particles having
a smaller median grain size than hard particles of the at least one
additional region.
[0023] Other aspects and advantages of the invention will be
apparent from the following description and the appended
claims.
BRIEF DESCRIPTION OF DRAWINGS
[0024] Embodiments of Rotating Cutting Elements for PDC Bits are
described with reference to the following figures. The same numbers
are used throughout the figures to reference like features and
components.
[0025] FIG. 1 shows a side view of a conventional drag bit.
[0026] FIG. 2 shows a top view of a conventional drag bit.
[0027] FIG. 3 is a schematic of a microstructure of a
polycrystalline diamond material.
[0028] FIG. 4 shows a polycrystalline diamond cutting element
according to embodiments of the present disclosure.
[0029] FIG. 5 shows a polycrystalline diamond cutting element
according to embodiments of the present disclosure.
[0030] FIG. 6 shows a polycrystalline diamond cutting element
according to other embodiments of the present disclosure.
[0031] FIG. 7 shows a diagram of a method for forming
polycrystalline diamond bodies according to embodiments of the
present disclosure.
[0032] FIG. 8 shows steps for forming polycrystalline diamond
bodies according to embodiments of the present disclosure.
[0033] FIG. 9 shows a polycrystalline diamond body according to
embodiments of the present disclosure.
[0034] FIG. 10 shows a polycrystalline diamond body according to
embodiments of the present disclosure.
[0035] FIGS. 11A-11C illustrate a rotatable polycrystalline diamond
body, according to an embodiment of the invention.
DETAILED DESCRIPTION
[0036] Generally, embodiments disclosed herein relate to
polycrystalline diamond ("PCD") cutting elements. PCD cutting
elements of the present disclosure may include a PCD body (also
referred to as a bulk PCD body) attached to a substrate, wherein
the PCD body is thicker than diamond layers of conventional PCD
cutting elements, or alternatively, PCD cutting elements of the
present disclosure may be formed entirely of the PCD body.
[0037] As used herein, "polycrystalline diamond" or "PCD" refers to
a plurality of interconnected diamond crystals having interstitial
spaces there between in which a metal component (such as a metal
catalyst) may reside. The interconnected diamond crystal structure
of PCD includes direct diamond-to-diamond bonding and not diamond
to diamond bonding through an intermediary material such as silicon
carbide. The interconnected diamond crystal structure of PCD may
often be referred to as forming a lattice or matrix structure.
Particularly, a metal catalyst material, such as cobalt, may be
used to promote re-crystallization of the diamond crystals, wherein
the diamond grains are regrow together to form the lattice
structure, thus leaving particles of the remaining metal catalyst
within the interstitial spaces of the diamond lattice.
Additionally, according to some embodiments of the present
disclosure, PCD material may also include boron dopants, as
discussed further below.
[0038] PCD, as defined by the present disclosure, may be formed by
high pressure high temperature ("HPHT") sintering of diamond grains
in the presence of a suitable catalyst or binder material, such as
one or more elements from Group VIII of the Periodic table or a
carbonate solvent catalyst, to achieve intercrystalline bonding
between the diamond grains. Optionally, PCD of the present
disclosure may be formed using boron-doped diamond crystals, or
undoped diamond crystals and a boron additive, in the HPHT
sintering process, as discussed further below. HPHT sintering
typically includes placing an unsintered mass or volume of diamond
grains within a reaction cell of a HPHT apparatus. A metal solvent
catalyst material may be included with the unsintered mass of
diamond crystalline particles in the reaction cell to promote
intercrystalline diamond-to-diamond bonding. The catalyst material
may be provided in the form of powder and mixed with the diamond
grains, or may be infiltrated into the diamond grains during HPHT
sintering. A suitable HPHT apparatus for this process is described
in U.S. Pat. Nos. 2,947,611; 2,941,241; 2,941,248; 3,609,818;
3,767,371; 4,289,503; 4,673,414; and 4,954,139, each of which are
incorporated herein by reference. The contents of the reaction cell
(the mass of diamond grains and metal catalyst) may be subjected to
HPHT conditions, which may conventionally include a minimum
temperature of about 1200.degree. C. and a minimum pressure of
about 35 kbars, and typically temperatures between about
1300-1500.degree. C. and pressures between about 45-60 kbar.
However, due to the increased thickness of PCD bodies according to
embodiments of the present disclosure, higher temperatures and
pressures may be used when compared to the HPHT conditions of
conventionally sized PCD bodies. For example, pressures may range
from about 55 to 90 kbar, and temperatures may range from about
1300.degree. C. to 1700.degree. C. In embodiments, the lower limit
of the pressure may be any of 55, 60, 65, 70, 75, or 80 kbar, and
the upper limit of the pressure may be any of 65, 70, 75, 80, 85,
or 90 kbar, with any lower limit being combinable with any upper
limit. In embodiments, the lower limit of the temperature may be
any of 1300.degree. C., 1350.degree. C., 1400.degree. C.,
1450.degree. C., 1500.degree. C., or 1550.degree. C., and the upper
limit may be any of 1450.degree. C., 1500.degree. C., 1550.degree.
C., 1600.degree. C., 1650.degree. C., or 1700.degree. C., with any
lower limit being combinable with any upper limit. Alternatively,
the PCD material may be formed from a carbonate solvent catalyst,
such as magnesium carbonate, which is typically sintered under
HP/HT conditions of 65-90 kBar and 1800-2500.degree. C.
[0039] As used herein, "thermally stable polycrystalline diamond"
or "TSP" refers to a plurality of interconnected diamond crystals
having a thermal stability greater than that of conventional PCD.
For example, TSP may be formed by removing substantially all metal
from the interstitial spaces between interconnected diamond
crystals of PCD. Alternatively, rather than actually removing the
catalyst material from PCD, the selected region of the PCD can be
rendered thermally stable by treating the catalyst material in a
manner that reduces or eliminates the potential for the catalyst
material to adversely impact the intercrystalline bonded diamond at
elevated temperatures. For example, the catalyst material can be
combined chemically with another material to cause it to no longer
act as a catalyst material, or can be transformed into another
material that again causes it to no longer act as a catalyst
material. Accordingly, as used herein, the terms "removing
substantially all" or "substantially free" as used in reference to
the catalyst material is intended to cover the different methods in
which the catalyst material can be treated to no longer adversely
impact the intercrystalline diamond in the PCD body or compact with
increasing temperature.
[0040] Diamond grains useful for forming PCD may include any type
of diamond particle, including natural or synthetic diamond powders
having a wide range of grain sizes. For example, such diamond
powders may have an average grain size in the range from
submicrometer in size to 100 micrometers, and from 1 to 80
micrometers in other embodiments. Further, one skilled in the art
would appreciate that the diamond powder may include grains having
a mono- or multi-modal distribution.
[0041] The diamond powder may be combined with a desired catalyst
material, and optionally, a boron additive powder, such as
described in U.S. Pat. No. 6,846,341, which is assigned to the
present assignee and herein incorporated by reference in its
entirety. The boron additives may be mixed throughout the diamond
powder, wherein the additives are small enough to diffuse into the
diamond lattice formed as the diamond grains are regrown into the
diamond-to-diamond bonded PCD. In some embodiments, a boron
additive in the amount of about 0.1 to 3.0 wt %, but greater or
lesser amounts may be used in other embodiments. A diamond powder
mixture used to form PCD material of the present disclosure may be
placed in a reaction cell, which is subjected to processing
conditions sufficient to cause the intercrystalline bonding between
the diamond crystals. It should be noted that if too much
additional non-diamond material is present in the powdered mass of
crystalline particles, appreciable intercrystalline bonding is
prevented during the sintering process. Such a sintered material
where appreciable intercrystalline bonding of regrown diamond has
not occurred is not within the definition of PCD. Following such
formation of intercrystalline bonding, a PCD body may be formed
that has, in one embodiment, at least about 70 percent by volume
diamond, with the remaining balance of the interstitial regions
between the diamond grains occupied by the catalyst material. In
other embodiments, the PCD may comprise at least 85 percent by
volume diamond, and in another embodiment at least 90 percent by
volume diamond. However, one skilled in the art would appreciate
that other diamond densities may be used in alternative
embodiments. Thus, PCD in accordance with the present disclosure
may include what is frequently referred to in the art as "high
diamond density" PCD.
[0042] FIG. 3 illustrates an example of a PCD microstructure 10
according to the present disclosure, which comprises a plurality of
diamond grains 12 that are bonded to one another with interstitial
volumes occupied by a binder material 14. Such PCD materials may
comprise a binder material or metal content up to about 20 percent
by volume, up to 10 percent by volume, or up to 8 percent by volume
in other embodiments, and the metals employed as the binder can
include, for example, Co, Ni, Fe, and mixtures thereof. The
particular amount of the metal component that is used is typically
controlled to provide a compromise between properties such as
thermal stability, toughness, and hardness.
[0043] Referring still to FIG. 3, it is evident that the binder
material 14 is not continuous throughout the microstructure in the
PCD material. Rather, the microstructure of the PCD material may
have a uniform distribution of binder among the interconnected
diamond grains, thus forming both diamond grain/binder interfaces
15 and diamond grain/diamond grain interfaces 16. The strength of a
given diamond to diamond bond is limited by particle size,
impurities in the sintered powders, and individual crystal to
crystal misorientation.
[0044] In contrast to the PCD material of the present disclosure,
as defined above, prior art diamond layers have been formed by
chemical vapor deposition ("CVD"). In particular, CVD diamond may
be produced by the reaction of a carbon based gas, such as methane,
acetylene or carbon dioxide, with atomic hydrogen, in the presence
of traces of oxygen. Various methods of activating atomic hydrogen
may include, for example, resistive heating of a metal filament, an
oxy-acetylene torch, or some form of plasma, such as an arc or a
glow discharge plasma. Although CVD diamond includes the growth of
multiple crystals (polycrystalline) of diamond, CVD diamond does
not fall under the present disclosure's definition of PCD. Rather,
CVD diamond has distinct material differences from the PCD material
of the present disclosure, as defined above. For example, CVD
diamond grows in a columnar structure, wherein continuous columnar
grains grow from the CVD nucleation sites, with no appreciable
bonds being formed between adjacent columnar diamond grains,
whereas PCD diamond is formed from an agglomeration of intergrown
diamond crystals. Further, CVD diamond is formed fully dense with
no binder phase.
[0045] Further, other types of manufactured diamond that fall
outside of the present disclosure's definition of PCD may include
high pressure synthetic single-crystal diamonds, carbide-diamond
composites, detonation diamond, diamond-like carbon ("DLC"), and
diamond produced by methods other than the HPHT processing
described above to form polycrystalline diamond. Diamond layers
formed by methods other than the one described in the present
disclosure's definition of PCD have distinct material properties,
and thus may be distinguished from PCD of the present disclosure
not only by the method of formation but also by microstructural
characteristics. For example, because of the random orientation of
its diamond grains, PCD of the present disclosure may be tougher
than natural diamond, synthetic diamond coatings and CVD diamond.
Additionally, while diamond grains are bonded directly to one
another in PCD of the present disclosure, diamond grains of
carbide-diamond composites (such as silicon carbide) are bonded
together through the carbide material (i.e.,
diamond-carbide-diamond). Although some diamond-to-diamond bonding
may also occur in carbide-diamond composites, such
diamond-to-diamond bonding does not form the diamond lattice
structure of PCD, as defined herein. Rather, carbide-diamond
composites include a mass of diamond and carbide, bonded together
by both diamond-carbide bonds and diamond-diamond bonds. However,
the bonds between the diamond grains of the PCD material of the
present disclosure consist of direct diamond-to-diamond bonds with
no other bonds being present between another material and the
diamond grains.
[0046] According to embodiments of the present disclosure, a method
of forming a cutting element may include placing a plurality of
diamond particles, a catalyst material source (such as a substrate
or a catalyst material powder), and optionally a boron additive in
a reaction cell of a HPHT apparatus and subjecting the plurality of
diamond particles to HPHT conditions to form a PCD body. High
pressure high temperature conditions may include temperatures
greater than 1300.degree. C., preferably ranging between
1300.degree. C. and 1700.degree. C., and pressures greater than 5
GPa, preferably ranging between 5.5 GPa and 9.0 GPa. Under the HPHT
conditions, a substantial amount of direct diamond-to-diamond
bonding occurs between the diamond particles to form the PCD
body.
[0047] In some embodiments, a method of forming a bulk PCD body may
include using multiple HPHT sintering processes, such as shown in
FIGS. 7 and 8. In particular, FIG. 7 shows a diagram of steps to
form a bulk PCD body according to methods of the present
disclosure, and FIG. 8 shows examples of the steps recited in FIG.
7. As shown, a first volume may be subjected to HPHT sintering
conditions 710, wherein the first volume may include a plurality of
diamond particles, a catalyst material source (such as a substrate
or a catalyst material powder), and optionally a boron additive.
Upon subjecting the first volume to HPHT sintering conditions, the
plurality of diamond particles are bonded together to form PCD.
Further, in embodiments having a substrate 716 as the catalyst
material source, such as shown in FIG. 8, the sintered first volume
712 includes the PCD body 714 attached to the substrate 716. The
sintered first volumes 712 shown in FIG. 8 have a PCD body 714
formed adjacent to a single substrate 716 at a planar interface
715, a PCD body 714 formed adjacent to two smaller substrates 716
at planar interfaces 715, and a PCD body 714 formed adjacent to two
smaller substrates 716 at non-planar interfaces 717. However,
according to other embodiments, the sintered first volume may
include a PCD body formed adjacent to one or more substrate
catalyst sources having various other shapes and sizes. Further, in
yet other embodiments, the sintered first volume may include a PCD
body formed without a substrate. For example, a first volume may
include mixture of a plurality of diamond particles and a catalyst
material powder, such as cobalt, which may be subjected to HPHT
sintering conditions without a substrate to form a sintered first
volume having a PCD body and no substrate. The sintered first
volume may then optionally be treated 720, such as by any of
removing a substrate from the PCD body 714, cleaning the PCD body
714, and/or leaching the PCD body 714.
[0048] The PCD body 714 may then be assembled 730 together with a
second volume 732, wherein the second volume 732 may include a
plurality of diamond particles 734, a catalyst material source such
as a substrate 736, and optionally a boron additive. However,
according to other embodiments, a second volume may include a
catalyst material source in the form of a powder, either mixed with
the diamond particles or placed adjacent to the diamond particles.
The assembly may then be subjected to HPHT sintering conditions 740
to form a sintered second volume. Upon subjecting the assembly to
HPHT sintering conditions, the plurality of diamond particles 734
in the second volume 732 are bonded together and to the PCD body
714 of the sintered first volume to form a larger PCD body 734. The
second sintered volume may then be treated 750, such as by any of
removing a substrate 736 from the PCD body 734, cleaning the PCD
body 734, and/or leaching the PCD body 734. Additional volumes,
such as a third volume, fourth volume, fifth volume, etc., of
diamond particles, a catalyst source, and optionally a boron
additive may be subsequently sintered with the PCD body 734 until a
desired bulk volume of the PCD body is achieved. Thus, according to
embodiments of the present disclosure, a bulk PCD body may be grown
using multiple HPHT sintering processes, such as shown in FIG. 7,
wherein the PCD body has a larger volume than conventionally formed
PCD layers. Further, in particular embodiments, the pressure used
in the first sintering cycle may be greater than the pressure used
in the second sintering cycle, and with the pressure being
incrementally decreased, with even further sintering cycles.
[0049] Referring now to FIG. 9, a bulk PCD body 900 may be grown
using multiple HPHT sintering processes, wherein a catalyst
material source is provided as a core 905. In particular, a
catalyst material source, such as tungsten carbide cobalt, may be
provided as a core 905. A plurality of diamond particles (and
optionally a boron additive) may be placed around the core 905 and
subjected to HPHT sintering conditions, such as in a reaction cell
of an HPHT apparatus, to form a first PCD layer 910 around the core
905. Another plurality of diamond particles may be placed around
the first PCD layer 910 and subjected to HPHT sintering conditions
to form a second PCD layer 920 around the first PCD layer 910. This
may be repeated so that additional PCD layers may be formed around
the second PCD layer until a desired bulk PCD body is achieved.
According to various embodiments, the plurality of diamond
particles forming various layers of the bulk PCD body may include
additional catalyst source material, such as cobalt powder, and
optionally boron additives. Further, although the core 905 is shown
as having a rod-shape extending the entire length of the bulk PCD
body in FIG. 9, a core may have other shapes and sizes and may
extend the entire length or a partial length of the bulk PCD body.
In some embodiments, the core 905 may form an acid infusion pathway
(as described below) during optional subsequent leaching
processes.
[0050] According to some embodiments of growing a bulk PCD body
using multiple HPHT sintering processes, the bulk PCD body may be
formed to include gradient properties, such as decreasing particle
size from an inner region of the bulk PCD body to an outer surface
of the bulk PCD body. For example, as shown in FIG. 10, a plurality
of diamond particles and a catalyst material may be subjected to
HPHT sintering conditions to form a first PCD body 1010. The
diamond particles may have a particle size ranging from 50 to 150
microns, with a lower limit of any of 50 microns, 75 microns, 100
microns, or 125 microns, and an upper limit of any of 75 microns,
100 microns, 125 microns, or 150 microns, where any lower limit may
be combined with any upper limit. A plurality of diamond particles
and a catalyst material may then be placed around the first PCD
body 1010 and subjected to HPHT sintering conditions to form a
second PCD body 1020 larger than the first PCD body 1010. The
plurality of diamond particles placed around the first PCD body to
form the second PCD body 1020 may be smaller than the diamond
particles used to form the first PCD body 1010, and may range, for
example from 30 microns to 100 microns, with any lower limit of 30
microns, 40 microns, 50 microns, 60 microns, 70 microns, or 80
microns, and any upper limit of 50 microns, 60 microns, 70 microns,
80 microns, 90 microns, or 100 microns, where any lower limit may
be used in combination with any upper limit. A plurality of diamond
particles and a catalyst material may then be placed around the
second PCD body 1020 and subjected to HPHT sintering conditions to
form a third PCD body 1030 larger than the second PCD body 1020.
The plurality of diamond particles placed around the second PCD
body to form the third PCD body 1030 may be smaller than the
diamond particles used to form the second PCD body 1020, and may
range, for example, from about 0.1 microns to 50 microns, with any
lower limit of 0.1 microns, 0.5 microns, 1 micron, 3 microns, 5
microns, 7 microns, 10 microns, 15 microns, 20 microns, or 30
microns, and any upper limit of 10 microns, 20 microns, 30 microns,
40 microns, or 50 microns, where any lower limit may be used in
combination with any upper limit. Additional processes of placing
diamond particles having decreasing particle sizes around PCD
bodies and subjecting the assembly to HPHT sintering conditions may
be preformed until the desired volume of the bulk PCD body 1000 is
achieved. Further, by using decreasing diamond particle sizes in
each subsequent sintering process, the bulk PCD body 1000 may have
a decreasing particle size gradient formed therein, wherein the
largest diamond particles form an inner region of the bulk PCD body
1000, the smallest diamond particles form an outer surface 1005 of
the bulk PCD body 1000, and decreasing diamond particle sizes are
used there between. However, according to other embodiments of the
present disclosure, other gradients may be formed through multiple
sintering processes in a bulk PCD body. For example, an increasing
particle size gradient may be formed from an inner region of the
bulk PCD body to an outer surface of the bulk PCD body. In other
examples, a diamond density gradient may be formed within the bulk
PCD body. For example, a bulk PCD body may have a highest diamond
density in an inner region of the bulk PCD body, a lowest diamond
density at an outer surface of the bulk PCD body, and a decreasing
diamond density from the inner region to the outer surface.
Alternatively, a bulk PCD body may have a lowest diamond density in
an inner region of the bulk PCD body, a highest diamond density at
an outer surface of the bulk PCD body, and an increasing diamond
density from the inner region to the outer surface. Such diamond
grains may range, for example, from 0.1 to 100 microns, as
discussed above, and the diamond densities may fall within the
range of 80 volume percent to 98 volume percent. The incremental
differences in diamond densities between two adjacent regions may
be at least 2 percent or at least 5 percent, thus the particular
densities and incremental differences may depend, for example, on
the total number of regions being used, and the desired density for
the outer, cutting edge, for example.
[0051] According to some embodiments of the present disclosure, PCD
may be formed with boron dopants, such as by subjecting boron-doped
diamond crystals and a catalyst material source to HPHT conditions,
or by subjecting undoped diamond crystals, boron additive powder,
and a catalyst material source to HPHT conditions. In embodiments
formed by subjecting a mixture of diamond crystals, boron additive
powder, and a catalyst material source to HPHT sintering, boron
diffuses into and throughout the diamond lattice, causing the
insulating diamond crystals to transform into semiconductive
diamond crystals, as described in U.S. Pat. No. 6,846,341, which is
incorporated herein by reference. Specifically, during the
transformation of the insulating diamond material to a
semiconductive material, some or all of the diamond crystals are
converted to diamond crystals having a semiconductive surface due
to diffusion of the boron. This diffusion phenomenon takes place
during the HPHT sintering process used to solidify the PCD, during
which the additive species are free to diffuse throughout the PCD.
Thus, according to this method, undoped diamond crystals are
converted to diamond crystals that include semiconductive surface
layers. Advantageously, cutting elements of the present disclosure
formed with boron-doped PCD may have enhanced thermal conductivity,
which may improve the ability of the PCD to conduct heat away from
the cutting surface of the cutting element.
[0052] PCD bodies of the present disclosure include a cutting face
and a thickness extending from the cutting face. For example,
referring to FIG. 4, a cutting element 400 includes a PCD body 410
disposed on a substrate 420, wherein an interface 405 is formed
between the PDC body 410 and substrate 420. The PCD body 410 has a
cutting face 415 and extends a thickness t from the cutting face
415 to the interface 405. As used herein, a cutting face of a PCD
body refers to an outer surface of the PCD body that may contact an
earthen formation to be cut. The cutting face of the PCD body may
cut the earthen formation by a shearing action. Thus, cutting
elements of the present disclosure may often be referred to as
shear cutters. The shape and size of the cutting face may vary. For
example, as shown, the cutting face 415 of the embodiment shown in
FIG. 4 has a circular shape, wherein the diameter may range between
8 and 19 mm, or up to 22 mm. In such embodiments, the PCD body 410
may extend a thickness t from the circular-shaped cutting face 415
to form a cylindrical-shaped PCD body. However, according to other
embodiments, a PCD body may have other shapes, such as an ellipsoid
or a prism.
[0053] Further, a PCD body may have a cutting face area ranging,
for example, from about 60 mm.sup.2 to about 500 mm.sup.2, with a
lower limit of any of 60, 80, 100, 150, or 250 mm.sup.2 and an
upper limit of any of 150, 175, 260, 400, or 500 mm.sup.2, where
any lower limit may be combined with any upper limit. In some
embodiments, a PCD body may have a non-planar cutting face. For
example, a PCD body may have a curved cutting face, such as a
concave or convex cutting face. In such embodiments, the cutting
face area may be measured by including the surface area of the
curve. Alternatively, a PCD cutting face may have multiple surface
alterations, such as grooves or multiple convex/concave formations,
formed in the cutting face. In such embodiments, the cutting face
area may be measured by excluding the surface area of any surface
alterations formed therein. Furthermore, a PCD cutting face may
include part of a core (such as described in FIG. 9) that may be
used to form an acid infusion pathway for leaching processes
(described below). Such core material or acid infusion pathways are
not considered when measuring the cutting face area.
[0054] Advantageously, the inventors of the present disclosure have
found a way to form PCD bodies having a thickness greater than
conventional PCD bodies formed in PCD cutting elements. The
thickness of PCD bodies according to the present disclosure may be
described using a cutting face area to thickness ratio. For
example, PCD bodies according to the present disclosure may have a
cutting face area to thickness ratio ranging from 60:16 to 500:5.
According to some embodiments, the cutting face area to thickness
ratio may have an upper limit selected from 500:5, 400:5, 350:9,
300:10, and 250:11, and a lower limit selected from 65:15, 70:14,
and 75:13, wherein any lower limit may be used in combination with
any upper limit. In other embodiments, a PCD body thickness may be
described using the distance the thickness extends transversely or
perpendicularly from the cutting face. For example, referring back
to FIG. 4, the thickness t of the PCD body 410 may extend
perpendicularly from the cutting face 415 a distance of at least 5
mm or at least 8 mm in another embodiment. According to some
embodiments disclosed herein, a PCD body may extend a uniform
thickness ranging between 5 mm and 12 mm, and up to 16 mm in other
embodiments. According to other embodiments, a PCD body may have a
non-uniform thickness that varies along the area of the cutting
face, for example, in a PCD body having a non-planar cutting face
and/or a non-planar interface, such that the thickness of the PCD
body ranges between 8 mm and 16 mm.
[0055] Further, PCD cutting elements of the present disclosure
formed by HPHT processing may or may not include a substrate
attached thereto, and if included, it can optimally be removed
after formation prior to installation on a cutting tool. For
example, embodiments of the present disclosure may include placing
a plurality of diamond particles (and optionally boron additives)
adjacent to a suitable substrate material in a reaction cell and
subjecting the contents of the reaction cell to HPHT conditions
(such as described in FIGS. 7 and 8). The substrate material may
comprise a catalyst or binder material that will melt and
infiltrate into the diamond volume during HPHT processing. Further,
the substrate may be provided in a powder, green, or sintered
state, and may be selected from those substrates conventionally
used to form PCD, that include carbides, nitrides, carbonitrides,
ceramics, metallic materials, cermet materials, and combinations
thereof. For example, substrate material may include hard
particles, such as tungsten carbide particles, and a binder
material, such as cobalt. Tungsten carbide particles used in a
substrate composition may include, for example, cemented tungsten
carbide, cast tungsten carbide, and/or other forms of tungsten
carbide known in the art. A substrate composition may include hard
particles having a median particle grain size ranging from about 2
microns to 6 microns according to some embodiments, from about 2
microns to 3 microns in other embodiments, and less than 2 microns
in yet other embodiments. Further, a substrate composition may
include a binder material comprising between about 12 and 16
percent by weight of the substrate composition.
[0056] Advantageously, the inventors of the present disclosure have
found that the bulk thermal conductivity of a PCD cutting element
may be increased by forming a PCD cutting element having no
substrate or a smaller substrate mounted to a thicker PCD body when
compared with conventional PCD cutting elements. For example,
conventional cutting elements having a PCD cutting layer mounted to
a substrate may have an estimated bulk thermal conductivity of 100
W/mK or less (where bulk thermal conductivity may be estimated from
volumetrically weighted averages of the thermal conductivity
properties of the PCD and substrate). However, PCD cutting elements
of the present disclosure made of a solid PCD body (having no
substrate mounted thereto) may have a bulk thermal conductivity of
200 W/mK or greater, and may range, for example, from 200 W/mK to
400 W/mK. PCD cutting elements of the present disclosure made of a
substrate mounted to a PCD body having a thickness greater than
conventionally formed PCD bodies may have a bulk thermal
conductivity ranging from 100 W/mK to 200 W/mK in some embodiments.
Additionally, as mentioned above, the inventors of the present
disclosure have found that PCD bodies according to embodiments
herein may be doped with boron to further increase the bulk thermal
conductivity of the PCD cutting element. For example, PCD cutting
elements of the present disclosure made with a boron-doped PCD body
may have a bulk thermal conductivity of 400 W/mK or greater, and
may range from 450 W/mK to 650 W/mK in some embodiments.
[0057] Conventional PCD cutting elements have been limited in their
ability to conduct heat away from the cutting surface due to the
relatively poor thermal conductivity of the substrate. However, the
inventors of the present disclosure have advantageously found that
the bulk thermal conductivity of a PCD cutting element may be
increased by forming PCD cutting elements according to the present
disclosure, which may be made of solid PCD bodies or relatively
thicker PCD bodies mounted to smaller substrates when compared with
conventional cutting elements. Specifically, replacing
conventionally used substrates with additional PCD material allows
for greater heat sinking capability of the cutting element due to
the larger bulk thermal conductivity, thereby drawing more heat
away from the cutting surface and reducing temperatures near the
wear surfaces. Additionally, having no substrate (or a smaller and
thus less critical substrate) mounted to PCD bodies of the present
disclosure may allow for the use of boron dopants without concern
for cutting element degradation. Specifically, while boron doping
in conventional PCD cutting elements tend to embrittle the attached
substrates, thus making them difficult to use in practice, the PCD
cutting elements of the present disclosure are made with no
substrate or a comparatively smaller substrate and thus less
critical component of the cutting element. Thus, PCD cutting
elements according to the present disclosure may be doped with
boron to further enhance the cutting element's bulk thermal
conductivity.
[0058] According to embodiments of the present disclosure, such as
cutting element 500 shown in FIG. 5, a PCD body 510 may be formed
on a substrate 520 at an interface 505, wherein the PCD body 510
has a cutting face 515 and a thickness t extending from the cutting
face 515 to the interface 505. The substrate 520 may include two
regions, a first region 522 adjacent to the PCD body 510 and a
second region 524 adjacent to the first region 522 and opposite
from the PCD body 510. The first region 522 may include a substrate
composition having hard particles with a median grain size smaller
than the median grain size of the hard particles forming the
substrate composition of the second region 524. For example, the
first region 522 may include a plurality of hard particles, such as
tungsten carbide particles, disposed in a binder matrix, wherein
the hard particles have a grain size ranging from about 2 microns
to about 3 microns, and wherein the binder matrix material forms
between 12 and 15 percent by weight of the first region
composition. The second region 524 may include a plurality of hard
particles disposed in a binder matrix, wherein the hard particles
have a grain size ranging from about 4 microns to about 6 microns,
and wherein the binder matrix material forms between 12 and 15
percent by weight of the first region composition. In some
embodiments, the first region may form from about 10 vol % up to
100 vol % of the substrate, with the balance being the second
region. In other embodiments, the first region may occupy a lower
limit of any of 10, 25, 50, 70, or 90 volume percent and an upper
limit of any of 10, 25, 50, 70, 90, or 100 volume percent, where
any lower limit may be combined with any upper limit, and where the
balance of the substrate is formed of the second region. In other
embodiments, the second region may occupy a lower limit of any of
10, 25, 50, 70, or 90 volume percent and an upper limit of any of
10, 25, 50, 70, 90, or 100 volume percent, where any lower limit
may be combined with any upper limit, and where the balance of the
substrate is formed of the first region. Further, the first region
522 may be provided in a reaction cell of an HPHT apparatus (for
forming a PCD body thereon) in powder or sintered form, and the
second region 524 may be provided adjacent to the first region in
powdered or sintered form.
[0059] In another embodiment, a PCD cutting element may be formed
by placing a layer of hard particle powder, such as carbide powder,
between a pre-formed substrate region and a plurality of diamond
particles in a reaction cell of a HPHT apparatus, and subjecting
the contents of the reaction cell to HPHT conditions. The
pre-formed substrate region may include a hard particle phase, such
as a tungsten carbide, disposed in a binder matrix, such as cobalt.
The layer of carbide powder may include carbide particles having a
smaller median grain size than the median grain size of the hard
particle phase in the pre-formed substrate region. During the HPHT
processing of the plurality of diamond particles, the carbide
powder layer, and the pre-formed substrate region, the binder
matrix material of the pre-formed substrate region may infiltrate
through the carbide powder layer and into the plurality of diamond
particles, thereby forming a PCD body interfacing a substrate
having two regions, wherein the region adjacent to the PCD body
(formerly the carbide powder layer) has a hard particle median
grain size less than the hard particle median grain size of the
region distant from the PCD body (formerly the pre-formed substrate
region).
[0060] By using a smaller hard particle size in a substrate region
adjacent to the PCD body than in an additional substrate region(s)
distant from the PCD body, a hard particle size gradient may be
formed throughout the substrate. According to embodiments of the
present disclosure, two or more substrate regions may be used to
form a substrate having a hard particle size gradient, wherein the
region interfacing the PCD body has a hard particle median grain
size smaller than the hard particle median grain size of the
additional region(s) (opposite from the PCD body), and wherein
subsequent regions have increasingly larger hard particle median
grain sizes. Advantageously, the inventors of the present
disclosure have found that a hard particle size gradient may help
to slow the infiltration rate of the substrate binder material into
the PCD body. A slower infiltration rate may prevent holes or
eruptions from forming in the PCD body during HPHT processing.
Other means of slowing the infiltration rate may include, for
example, using substrates with lower magnetic saturation, such as
described in U.S. Application No. 61/564,577, which is incorporated
herein by reference.
[0061] According to other embodiments, as shown in FIG. 4, a
substrate 420 may be formed of a single continuous substrate
composition. For example, the substrate 420 may include a hard
particle phase, wherein the hard particles have a grain size of
less than 6 microns, preferably ranging from about 2 microns to
about 3 microns, and a binder phase, wherein the binder phase may
form between 12 and 16 percent by weight of the substrate
composition. According to other embodiments, hard particles having
a grain size less than 2 microns or even less than 1 microns may be
used to form the substrate. Such smaller particle sizes may be used
in combination with higher sintering temperatures, such as
temperatures ranging from 1500 to 1700.degree. C. Hard particles
having a grain size of 6 microns or less may be referred to herein
as "fine grain hard particles." By using fine grain hard particles
to form the substrate, a smaller mean free path between the hard
particles may be achieved.
[0062] Advantageously, according to embodiments disclosed herein,
PCD bodies having a thickness greater than conventionally made PCD
bodies may be formed and used on downhole cutting tools. For
example, the inventors of the present disclosure have found that by
creating a smaller mean free path between the hard particles, the
infiltration rate of the binder material into the adjacent PCD body
during HPHT processing may be slower when compared with the
infiltration rate occurring in substrate compositions having a
larger mean free path between hard particles. Using a slower
infiltration rate may prevent cracks from forming in the PCD body
during processing and use, thus providing a thicker PCD body that
may be used in downhole drilling operations or the like. Further,
thick PCD bodies of the present disclosure may be formed using
higher pressures than in HPHT processes used to form conventional
PCD. Particularly, according to conventional methods of forming a
PCD body on a substrate, the substrate material may contribute to
pressure generation within a reaction cell of an HPHT apparatus.
However, the thicker PCD bodies of the present disclosure formed
with a relatively smaller substrate material (or no substrate
material) may lack the pressure generation found in conventional
PCD body formation. Thus, according to embodiments disclosed
herein, a thick PCD body may be formed by an HPHT process having
higher than conventional pressures, for example, by a 4-5% increase
in pressure for forming a PCD body of the present disclosure on a
relatively small substrate, or a 8-10% increase in pressure for
forming a PCD body of the present disclosure without the use of a
substrate.
[0063] In embodiments having a PCD body formed upon a substrate,
the substrate may be subsequently removed from the PCD body to form
a PCD cutting element made entirely of PCD. For example, a
substrate may be removed from a PCD body by grinding or blasting
off the substrate, by acid digestion, or by other removal methods
known in the art.
[0064] Furthermore, PCD bodies of the present disclosure may be at
least partially leached (i.e., leached at least a partial distance
from a surface of the PCD body), whereby the catalyst material is
removed from the leached part of the PCD body. As used herein, the
term "removed" refers to the reduced presence of catalyst material
in the PCD body, and is understood to mean that a substantial
portion of the catalyst material no longer resides in the PCD body.
However, one skilled in the art would appreciate that trace amounts
of catalyst material may still remain in the microstructure of the
PCD body within the interstitial regions and/or adhered to the
surface of the diamond grains. Alternatively, rather than actually
removing the catalyst material from the PCD body, the selected
region of the PCD body can be rendered thermally stable by treating
the catalyst material in a manner that reduces or eliminates the
potential for the catalyst material to adversely impact the
intercrystalline bonded diamond at elevated temperatures. For
example, the catalyst material may be combined chemically with
another material to cause it to no longer act as a catalyst
material (or to have less thermal mismatch with diamond), or can be
transformed into another material that again causes it to no longer
act as a catalyst material (or to have less thermal mismatch with
diamond). Accordingly, as used herein, the terms "removing
substantially all" or "substantially free" as used in reference to
the catalyst material is intended to cover the different methods in
which the catalyst material can be treated to no longer adversely
impact the intercrystalline diamond in the PCD body with increasing
temperature.
[0065] The quantity of the catalyst material remaining in the
material PCD microstructure after the PCD body has been subjected
to a leaching treatment may vary, for example, on factors such as
the treatment conditions, including treatment time. Further, one
skilled in the art would appreciate that it may be acceptable or
desired in certain applications to allow a small amount of catalyst
material to stay in the PCD body. In a particular embodiment, the
PCD body may include up to 1-2 percent by weight of the catalyst
material. However, one skilled in the art would appreciate that the
amount of residual catalyst present in the leached PCD body may
depend on the diamond density of the material, and the body
thickness.
[0066] A PCD body of the present disclosure may be leached by
exposing the PCD body to a leaching agent, such as described in
U.S. Pat. No. 4,224,380, which is herein incorporated by reference
in its entirety. In select embodiments, the leaching agent may be a
weak, strong, or mixtures of acids. In other embodiments, the
leaching agent may be a caustic material such NaOH or KOH. Suitable
acids may include, for example, nitric acid, hydrofluoric acid,
hydrochloric acid, sulfuric acid, phosphoric acid, or perchloric
acid, or combinations of these acids. In addition, caustics, such
as sodium hydroxide and potassium hydroxide, have been used to the
carbide industry to digest metallic elements from carbide
composites. In addition, other acidic and basic leaching agents may
be used as desired. Those having ordinary skill in the art will
appreciate that the molarity of the leaching agent may be adjusted
depending on the time desired to leach, concerns about hazards,
etc.
[0067] Further, accelerated leaching techniques may be used to
treat a PCD body of the present disclosure, such as described in
U.S. Provisional Application No. 61/081,626, which is assigned to
the present assignee and herein incorporated by reference in its
entirety. For example, the leaching of a PCD body may be
accelerated by forming acid infusion pathway(s) in the PCD body, so
that the acid (or other leaching agent) may more readily access the
interior portions of the PCD body, leading to a faster and cleaner
leaching treatment. Acid infusion pathways may include any passage
or structure through which a leaching agent (often acid) flows with
less resistance than compared to an intercrystalline network of
diamond grains so that such leaching agent may more readily infuse
into interior regions of the polycrystalline diamond layer. Thus,
such acid infusion pathways may include cavities formed from
removal of PCD material from the PCD body, as well as a material
structure through which a leaching agent may more easily diffuse as
compared to PCD, such as for example, through incorporation of a
metal, cermet, or ceramic fiber into a diamond mixture such that a
metal-, cermet-, or ceramic-filled channel or passageway is formed
in the PCD body. For example, according to some embodiments, a PCD
body may have at least one acid infusion pathway that is a cavity
or channel extending a distance through the PCD body up to the
entire thickness of the PCD body and that has a diameter ranging
from microns to 1 mm, and up to about 7 mm, depending on the
diameter of the PCD body. Further, an acid infusion pathway
extending through a PCD body may be formed before or during a
leaching process. Methods of forming cavities in a PCD body are
described in U.S. Provisional Application No. 61/081,619, which is
assigned to the present assignee and herein incorporated by
reference in its entirety. Moreover, other accelerating leaching
techniques may be used, such as application of increased
temperatures, pressures, ultrasound, etc., including the techniques
described in U.S. Patent Application No. 2008/0185189, which is
assigned to the present assignee and herein incorporated by
reference in its entirety. Leaching a PCD body may be desirable for
some rolling cutter embodiments, as well as fixed cutter
embodiments.
[0068] According to embodiments of the present disclosure, at least
part of a PCD may be leached to form thermally stable
polycrystalline diamond. For example, a PCD body may be subjected
to a leaching process along at least part of the thickness of the
PCD body. According to some embodiments, at least 2 mm along the
thickness of the PCD body may be leached. However, according to
other embodiments, the entire PCD body may be leached.
Advantageously, because embodiments of the present disclosure may
include a cutting element made only of a PCD body with no
substrate, the entire cutting element may be subjected to a
leaching process (e.g., the entire cutting element may be placed in
a leaching agent or in an accelerated leaching vessel), whereas
conventional cutting elements having a PCD body mounted to a
substrate requires the substrate to be masked from the leaching
process.
[0069] Referring to FIG. 6, a cutting element 600 according to
embodiments of the present disclosure may have an acid infusion
pathway 605 formed through the PCD body 610 and subjected to a
leaching process to form thermally stable polycrystalline diamond.
As shown, the cutting element 600 has a PCD body 610, wherein the
PCD body 610 has a cutting face 615 and extends a thickness t from
the cutting face 610. The PCD body 610 has a cavity forming an acid
infusion pathway 605 extending through the PCD body 610 along the
shortest dimension of the PCD body. However, according to other
embodiments of the present disclosure, an acid infusion pathway may
extend partially through the PCD body. One or more acid infusion
pathways may be formed in a PCD body of the present disclosure.
Further, one or more acid infusion pathways may be formed in a PCD
body along the shortest dimension of the PCD body and/or along
other dimensional directions.
[0070] PCD cutting elements according to the present disclosure may
be fixed cutters or rolling cutters, and may be used on downhole
cutting tools, such as drill bits, reaming tools, fishing tools,
and milling tools. For example, PCD cutting elements of the present
disclosure may be rolling cutters, such as those described in
Examples of rolling cutters that may be used in the present
disclosure may be found at least in U.S. Pat. No. 7,703,559, U.S.
Patent Publication No. 2011/0297454, and U.S. Patent Application
Nos. 61/351,035, 61/479,151, 61/479,183, 61/566,875, 61/566,859,
61/561,016, 61/559,423, which are assigned to the present assignee
and hereby incorporated by reference in their entirety, wherein the
PCD cutting elements are rotatably mounted to a cutter pocket of a
downhole drilling tool. In other embodiments, a PCD cutting element
of the present disclosure may be fixed to a downhole cutting tool,
such as in a cutter pocket formed in a blade of a drag bit, by
brazing through an intermediary sleeve material or by mechanical
attachment. In embodiments having a PCD cutting element attached to
a cutting tool by brazing, the PCD cutting element may be brazed
within a cutter pocket by vacuum or induction brazing, for example.
During a brazing process, a braze alloy, such as a material
selected from silver, copper, zinc, tin, boron, gallium, indium,
and thallium, or other braze alloys known in the art, may be placed
in the cutter pocket between the surfaces of the cutter pocket and
the PCD cutting element, either before or after the PCD cutting
element is positioned in the cutter pocket. Heat is applied to the
braze alloy to melt the braze alloy, and as the braze alloy cools,
a bond is formed between the PCD cutting element and the cutter
pocket. According to some embodiments, use of boron in the braze
alloy may be preferred due to its enhanced ability to bond to
diamond.
[0071] PCD cutters of the present disclosure may be secured to a
downhole cutting tool such that the cutting face of the PCD cutter
faces in the direction of rotation of the downhole cutting tool.
Thus, as the cutting tool rotates, the cutting face of the PCD
cutter contacts and scrapes the earthen formation being cut. Due to
this shearing-type engagement with the earthen formation, such
cutters are often referred to as shear cutters. According to
embodiments of the present disclosure, a PCD cutter of the present
disclosure may be placed in a cutter pocket formed in a cutting
tool and secured thereto. In embodiments having the PCD cutter
rotatably secured in the cutter pocket (wherein the PCD cutter is a
rolling cutter), the PCD cutter may be secured to the cutting tool
mechanically, such as described in U.S. Publication No.
2007/0278017. In embodiments having the PCD cutter fixedly secured
in the cutter pocket, the PCD cutter may be attached to the cutting
tool by brazing and/or by mechanical attachment. The PCD cutter,
whether fixed to or rotatably secured to the cutting tool, may be
positioned in a cutter pocket so that the cutting face of the PCD
cutter faces in the direction of rotation of the cutting tool and
wherein the thickness of the PCD cutter extends from the cutting
face a distance within the cutter pocket.
[0072] For example, according to embodiments of the present
disclosure, a downhole cutting tool, such as a drill bit, may have
a body and a rotational axis extending there through. A plurality
of cutter pockets may be formed in the drill bit, and any of the
PCD cutters of the present disclosure placed therein. As discussed
above, PCD cutters according to embodiments of the present
disclosure may be made of a PCD body having a cutting face, a
thickness extending from the cutting face, and a cutting face area
to thickness ratio ranging from 60:16 to 400:8. A PCD cutter of the
present disclosure may be positioned within one of the cutter
pockets of the cutting tool such that the cutting face of the PCD
cutter faces in the direction of rotation of the cutting tool and
wherein the thickness of the PCD cutter extends from the cutting
face a distance within the cutter pocket.
[0073] Referring now to FIGS. 11A-C, a cross-sectional view of a
cutter assembly having a rotatable cutting element 2020, according
to an embodiment of the invention. According to an embodiment, a
rotatable cutting element may be retained in a cutter pocket. For
example, a segment of a bit blade 2000 has a rotatable cutting
element 2020 assembled within a cutter pocket 2010. Particularly,
the rotatable cutting element 2020 has a cutting face 2022, an
outer circumferential surface 2024, and a circumferential channel
2026 formed within the outer circumferential surface 2024. The
cutter pocket 2010 has a back surface 2012 and a side surface 2014,
wherein a receptacle 2015 (represented by the shaded area) is
formed within the side surface 2014 to receive a partial sleeve
2040. The receptacle 2015 extends from the leading side 2002 of the
blade 2000 a distance D along the length of the cutter pocket 2010
and a radial distance around the side surface of the cutter pocket
2010. A partial sleeve 2040 may be positioned adjacent to the
rotatable cutting element 2020, such that the partial sleeve 2040
extends partially around the outer circumferential surface 2024 of
the rotatable cutting element 2020. Further, the partial sleeve
2040 may have a lip 2046 formed thereon that mates with the
circumferential channel 2026 of the rotatable cutting element 2020.
The rotatable cutting element 2020 and the partial sleeve 2040 may
then be inserted into the cutter pocket 2010. The partial sleeve
2040 may be attached to the cutter pocket 2010 to form part of the
cutter pocket side surface, wherein the rotatable cutting element
2020 may rotate within the cutter pocket 2010 and partial sleeve
2040. Methods of attaching the partial sleeve 2040 to the cutter
pocket 2010 may include, for example, brazing, welding, mechanical
locking, or other means known in the art.
[0074] As shown, the partial sleeve 2040 and the cutter pocket side
surface 2014 may form an arc A. The arc may extend around the
rotatable cutting element 2020 greater than 180 degrees. In some
embodiments having an arc extending greater than 180 degrees, a
rotatable cutting element may be retained within a cutter pocket
using only the side wall of the cutter pocket. For example, a side
wall retention mechanism (the mating lip formed along the cutter
pocket side wall and circumferential channel formed within the
rotatable cutting element) may retain the rotatable cutting element
axially within the cutter pocket, while the extension of the cutter
pocket side wall greater than 180 degrees may inhibit the rotatable
cutting element from being dislodged (pulled out from the top face)
from the cutter pocket.
[0075] Any of the PCD cutting elements described herein may be
installed on a bit to shear an earthen formation. For example, in
some embodiments, a PCD cutting element according to the present
disclosure may have a channel formed therein (described above). In
such embodiments, the PCD cutting element may be positioned within
a cutter pocket formed on a bit and at least partially retained to
the bit using the channel. For example, a mechanical retention
mechanism may be at least partially inserted into the channel and
either attached to the bit or formed integrally with the bit to
retain the PCD cutting element within the cutter pocket. The PCD
cutting element may be retained to the bit using various mechanical
retention mechanisms, such that the cutting face of the PCD cutting
element faces in the direction or rotation of the bit.
[0076] Although only a few example embodiments have been described
in detail above, those skilled in the art will readily appreciate
that many modifications are possible in the example embodiments
without materially departing from this invention. Accordingly, all
such modifications are intended to be included within the scope of
this disclosure as defined in the following claims.
* * * * *