U.S. patent application number 17/569798 was filed with the patent office on 2022-04-28 for polycrystalline diamond cutting elements having lead or lead alloy additions.
The applicant listed for this patent is DIAMOND INNOVATIONS, INC.. Invention is credited to Andrew Gledhill, Christopher Long.
Application Number | 20220127909 17/569798 |
Document ID | / |
Family ID | |
Filed Date | 2022-04-28 |
United States Patent
Application |
20220127909 |
Kind Code |
A1 |
Long; Christopher ; et
al. |
April 28, 2022 |
Polycrystalline Diamond Cutting Elements Having Lead or Lead Alloy
Additions
Abstract
Polycrystalline diamond cutting elements having enhanced thermal
stability, drill bits incorporating the same, and methods of making
the same are disclosed herein. In one embodiment, a cutting element
includes a substrate having a metal carbide and a polycrystalline
diamond body bonded to the substrate. The polycrystalline diamond
body includes a plurality of diamond grains bonded to adjacent
diamond grains by diamond-to-diamond bonds and a plurality of
interstitial regions positioned between adjacent diamond grains. At
least a portion of the plurality of interstitial regions comprise
lead or lead alloy, a catalyst material, metal carbide, or
combinations thereof. At least a portion of the plurality of
interstitial regions comprise lead or lead alloy that coat portions
of the adjacent diamond grains such that the lead or lead alloy
reduces contact between the diamond and the catalyst.
Inventors: |
Long; Christopher;
(Westerville, OH) ; Gledhill; Andrew;
(Westerville, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DIAMOND INNOVATIONS, INC. |
Worthington |
OH |
US |
|
|
Appl. No.: |
17/569798 |
Filed: |
January 6, 2022 |
Related U.S. Patent Documents
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Application
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Filing Date |
Patent Number |
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16167902 |
Oct 23, 2018 |
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17569798 |
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14707278 |
May 8, 2015 |
10167675 |
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16167902 |
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International
Class: |
E21B 10/567 20060101
E21B010/567; B24D 3/10 20060101 B24D003/10; B24D 18/00 20060101
B24D018/00; B22F 5/00 20060101 B22F005/00; B24D 99/00 20060101
B24D099/00; C22C 11/00 20060101 C22C011/00; C22C 26/00 20060101
C22C026/00; E21B 10/573 20060101 E21B010/573; B22F 3/14 20060101
B22F003/14; B22F 3/24 20060101 B22F003/24 |
Claims
1-11. (canceled)
12. A method of forming a polycrystalline diamond compact,
comprising: assembling a reaction cell comprising a plurality of
diamond particles, lead or lead alloy having lead present in an
amount of at least about 90 wt. % of the lead alloy, a catalyst
material, and a substrate comprising a metal carbide within a
refractory metal container; subjecting the reaction cell and its
contents to a high pressure high temperature sintering process to
form a continuous diamond volume in which the diamond particles are
compacted into a densified unbonded diamond region in which at
least some of the diamond particles are separated by interstitial
regions, the lead or lead alloy is melted and is present in a
liquid state in at least some of the interstitial regions between
diamond particles, and the catalyst material is melted and is
present in at least some of the interstitial regions between the
individual diamond grains, wherein the catalyst material promotes
formation of diamond-to-diamond bonds between adjacent diamond
particles; and returning the reaction cell to ambient pressure and
temperature to form the polycrystalline diamond compact such that
the polycrystalline diamond compact comprises a diamond body bonded
to the metal carbide substrate. wherein the lead or lead alloy
coats surfaces of at least a portion of the plurality of diamond
particles present in the diamond body of the polycrystalline
diamond compact after the high pressure high temperature sintering
operation is completed, wherein the lead or lead alloy comprises of
0.1 vol. % to about 5.0 vol. % of the diamond body, and wherein the
volume of lead or lead alloy introduced to the diamond particles is
less than a volume of interstitial regions between diamond
particles.
13. The method of claim 12, wherein the catalyst material is swept
through at least a portion of the plurality of unbonded diamond
particles while molten and displaces a portion of the lead or lead
alloy from the interstitial regions between diamond particles.
14. The method of claim 12, wherein the lead or lead alloy is swept
through at least a portion of the plurality of unbonded diamond
particles while molten.
15. The method of claim 12, wherein the lead or lead alloy is mixed
with the diamond particles prior to the step of compaction of the
diamond particles.
16. (canceled)
17. The method of claim 12, wherein when the lead or lead alloy and
the catalyst material are held at a temperature above the melting
or liquidus temperature of the catalyst material, the lead or lead
alloy has a lower viscosity than the catalyst material.
18. The method of claim 12, further comprising subjecting the
diamond volume to a leaching process in which a leaching agent
removes at least portions of the catalyst material and lead or lead
alloy from the interstitial regions of the diamond volume.
19. The method of claim 12, wherein the diamond grains have higher
wettability with the catalyst material than the lead or lead alloy
when both are molten.
20. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] None.
TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY
[0002] The present disclosure relates generally to cutting elements
made from superhard abrasive materials and, more particularly, to
cutting elements made from polycrystalline diamond having a lead or
lead alloy addition that surround the individual diamond grains,
and methods of making the same.
BACKGROUND
[0003] Polycrystalline diamond ("PCD") compacts are used in a
variety of mechanical applications, for example in material removal
operations, as bearing surfaces, and in in wire-drawing operations.
PCD compacts are often used in the petroleum industry in the
removal of material in downhole drilling. The PCD compacts are
formed as cutting elements, a number of which are attached to drill
bits, for example, roller-cone drill bits and fixed-cutting element
drill bits.
[0004] PCD cutting elements typically include a superabrasive
diamond layer, referred to as a polycrystalline diamond body, which
is attached to a substrate. The polycrystalline diamond body may be
formed in a high pressure high temperature (HPHT) process, in which
diamond grains are held at pressures and temperatures to cause the
diamond particles bond to one another.
[0005] As is conventionally known, the diamond particles are
introduced to the HPHT process in the presence of a catalyst
material that, when subjected to the conditions of the HPHT
process, promotes formation of interparticle diamond bonds. The
catalyst material may be embedded in a substrate, for example, a
cemented tungsten carbide substrate having cobalt. The catalyst
material may infiltrate the diamond particles from the substrate.
Following the HPHT process, the diamond particles are sintered to
one another and may be attached to the substrate.
[0006] While the catalyst material promotes formation of the
inter-diamond bonds during the HPHT process, the presence of the
catalyst material in the sintered diamond body after the completion
of the HPHT process may also reduce the stability of the
polycrystalline diamond body at elevated temperatures. Some of the
diamond grains may undergo a back-conversion to a softer
non-diamond form of carbon (for example, graphite or amorphous
carbon) at elevated temperatures. Further, mismatch of the thermal
expansion of the materials may induce stress into the diamond
lattice causing microcracks in the diamond body. Back-conversion of
diamond and stress induced by the mismatch of thermal expansion of
the materials may contribute to a decrease in the toughness,
abrasion resistance, arid/or thermal stability of the PCD cutting
elements during operation.
[0007] Accordingly, polycrystalline diamond cutting elements that
have improved thermal stability may be desired.
SUMMARY
[0008] In one embodiment, a cutting element includes a substrate
having a metal carbide and a polycrystalline diamond body bonded to
the substrate. The polycrystalline diamond body includes a
plurality of diamond grains bonded to adjacent diamond grains by
diamond-to-diamond bonds and a plurality of interstitial regions
positioned between adjacent diamond grains. At least a portion of
the plurality of interstitial regions include lead or lead alloy
where lead is present in an amount of at least about 90 wt. % of
the lead alloy, a catalyst material, metal carbide, or combinations
thereof. At least a portion of the plurality of interstitial
regions include lead or lead alloy that coat portions of the
adjacent diamond grains such that the lead or lead alloy reduces
contact between the diamond and the catalyst.
[0009] In another embodiment, a polycrystalline diamond volume
includes a plurality of diamond grains bonded to adjacent diamond
grains by diamond-to-diamond bonds forming a continuous diamond
matrix and a plurality of interstitial regions positioned between
adjacent diamond grains and forming a continuous interstitial
matrix. At least a portion of the continuous interstitial matrix
includes catalyst material that is separated from the diamond
grains by lead or lead alloy where lead is present in an amount of
at least about 90 wt. % of the lead alloy such that the lead or
lead alloy reduces contact between the diamond and the catalyst
material.
[0010] In yet another embodiment, a cutting element includes a
substrate that includes a metal carbide and a polycrystalline
diamond body bonded to the substrate. The polycrystalline diamond
body includes a plurality of diamond grains bonded to adjacent
diamond grains by diamond-to-diamond bonds forming a continuous
diamond matrix and a plurality of interstitial regions positioned
between adjacent diamond grains and forming a continuous
interstitial matrix. At least a portion of the continuous
interstitial matrix includes catalyst material that is separated
from the diamond grains by lead or lead alloy, where lead is
present in an amount of at least about 90 wt% of the lead alloy,
such that the lead or lead alloy reduces contact between the
diamond and the catalyst material.
[0011] In yet another embodiment, a method of forming a cutting
element includes assembling a reaction cell comprising a plurality
of diamond particles, lead or lead alloy having lead present in an
amount of at least about 90 wt. % of the lead alloy, a catalyst
material, and a substrate within a refractory metal container. The
method further includes subjecting the reaction cell and its
contents to a high pressure high temperature sintering process to
form a continuous diamond volume. The diamond particles are
compacted into a densified unbonded diamond region in which at
least some of the diamond particles are separated by interstitial
regions. The lead or lead alloy is melted and is present in a
liquid state in at least some of the interstitial regions between
diamond particles. The catalyst material is melted and is present
in at least some of the interstitial regions between the individual
diamond grains, where the catalyst material promotes formation of
diamond-to-diamond bonds between adjacent diamond particles. The
lead or lead alloy coats surfaces of at least a portion of the
plurality of diamond particles after the high pressure high
temperature sintering operation is completed.
[0012] In yet another embodiment, a drill bit includes a material
removal portion having a plurality of shanks. The material removal
portion having an axis of rotation that is relative to a base
portion. The drill bit also includes at least one cutting element
that is bonded to the material removal portion at one of the
plurality of shanks. The cutting elements include a substrate
comprising a metal carbide and a polycrystalline diamond body
bonded to the substrate. The polycrystalline diamond body includes
a plurality of diamond grains bonded to adjacent diamond grains by
diamond-to-diamond bonds and a plurality of interstitial regions
positioned between adjacent diamond grains. At least a portion of
the plurality of interstitial regions include lead or lead alloy
where lead is present in an amount of at least about 90 wt. % of
the lead alloy, a catalyst material, metal carbide, or combinations
thereof. At least a portion of the plurality of interstitial
regions include lead or lead alloy that coat portions of the
adjacent diamond grains such that the lead or lead alloy reduces
contact between the diamond and the catalyst.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The patent or application file contains at least one
photomicrograph executed in color. Copies of this patent or patent
application publication with color photomicrographs will be
provided by the Office upon request and payment of the necessary
fee.
[0014] The foregoing summary, as well as the following detailed
description of the embodiments, will be better understood when read
in conjunction with the appended drawings. It should be understood
that the embodiments depicted are not limited to the precise
arrangements and instrumentalities shown.
[0015] FIG. 1 is a schematic side cross-sectional view of a PCD
cutting element according to one or more embodiments shown or
described herein;
[0016] FIG. 2 is a detailed schematic side cross-sectional view of
the PCD cutting element of FIG. 1A shown at location A;
[0017] FIG. 3 is a transmission electron micrograph of a cutting
element according to one or more embodiments shown or described
herein; and
[0018] FIG. 4 is a plot of energy dispersive X-ray spectroscopy for
cobalt in the region of the cutting element depicted in FIG. 3;
[0019] FIG. 5 is a plot of energy dispersive X-ray spectroscopy for
lead in the region of the cutting element depicted. in FIG. 3;
[0020] FIG. 6 is a schematic flow chart depicting a manufacturing
process of a PCD cutting element; and
[0021] FIG. 7 is a schematic perspective view of a drill bit having
a plurality of PCD cutting elements according to one or more
embodiments shown or described herein.
DETAILED DESCRIPTION
[0022] The present disclosure is directed to polycrystalline
diamond cutting elements having enhanced thermal stability, drill
bits incorporating the same, and methods of making the same. A
cutting element may include a substrate and a polycrystalline
diamond body bonded to the substrate. The polycrystalline diamond
body may include a plurality of diamond grains bonded to adjacent
diamond grains by diamond-to-diamond bonds and a plurality of
interstitial regions positioned between adjacent diamond grains. At
least a portion of the plurality of interstitial regions include
lead or lead alloy that coat portions of the adjacent diamond
grains such that the lead or lead alloy reduces contact between the
diamond and the catalyst introduced to aid in sintering of the
diamond particles. Polycrystalline diamond cutting elements having
enhanced thermal stability, drill bits incorporating the same, and
methods of making the same are described in greater detail
below.
[0023] It is to be understood that this disclosure is not limited
to the particular methodologies, systems and materials described,
as these may vary. It is also to be understood that the terminology
used in the description is for the purpose of describing the
particular versions or embodiments only, and is not intended to
limit the scope. For example, as used herein, the singular forms
"a," "an," and "the" include plural references unless the context
clearly dictates otherwise. En addition, the word "comprising" as
used herein is intended to mean "including but not limited to."
Unless defined otherwise, all technical and scientific terms used
herein have the same meanings as commonly understood by one of
ordinary skill in the art.
[0024] Unless otherwise indicated, all numbers expressing
quantities of ingredients, properties such as size, weight,
reaction conditions and so forth used in the specification and
claims are to the understood as being modified in all instances by
the term "about". Accordingly, unless indicated to the contrary,
the numerical parameters set forth in the following specification
and attached claims are approximations that may vary depending upon
the desired properties sought to be obtained by the end user. At
the very least, and not as an attempt to limit the application of
the doctrine of equivalents to the scope of the claims, each
numerical parameter should at least be construed in light of the
number of reported significant digits and by applying ordinary
rounding techniques.
[0025] As used herein, the term "about" means plus or minus 10% of
the value of the number with which it is being used. Therefore,
"about 40" means in the range of 36-44. As used herein, all
numerical values should be interpreted to include "about" prior to
their recitation.
[0026] Polycrystalline diamond compacts (or "PCD compacts", as used
hereafter) may represent a volume of crystalline diamond grains
with embedded non-diamond material filling the inter-granular
spaces. In one example, a PCD compact includes a plurality of
crystalline diamond grains that are bonded to each other by strong
interparticle diamond bonds and forming a continuous
polycrystalline diamond body, and the inter-granular regions,
disposed between the bonded grains and filled with a non-diamond
material (e.g., a catalyst material such as cobalt or its alloys),
which was used to promote diamond bonding during fabrication of the
PCD compact. Suitable metal solvent catalysts may include the metal
in Group VIII of the Periodic table. Polycrystalline diamond
cutting elements (or "PCD cutting element", as is used hereafter)
include the above mentioned polycrystalline diamond body attached
to a suitable substrate (for example, cemented tungsten
carbide-cobalt (WC--Co)). The attachment between the
polycrystalline diamond body and the substrate may be made by
virtue of the presence of a catalyst, for example cobalt metal. In
another embodiment, the polycrystalline diamond body may be
attached to the substrate by brazing. In another embodiment, a PCD
compact includes a plurality of crystalline diamond grains that are
strongly bonded to each other by a hard amorphous carbon material,
for example a-C or t-C carbon. In another embodiment, a PCD compact
includes a plurality of crystalline diamond grains, which are not
bonded to each other, but instead are bound together by foreign
bonding materials such as borides, nitrides, or carbides, for
example, SiC.
[0027] 100271 As discussed above, conventional. PCD cutting
elements are used in a variety of industries and applications in
material removal operations. PCD cutting elements are typically
used in non-ferrous metal removal operations and in downhole
drilling operations in the petroleum industry. Conventional PCD
cutting elements exhibit high toughness, strength, and abrasion
resistance because of the inter-granular inter-diamond bonding of
the diamond grains that make up the polycrystalline diamond bodies
of the PCD cutting elements. The inter-diamond bonding of the
diamond grains of the polycrystalline diamond body are promoted
during an HPHT process by a catalyst material. However, at elevated
temperature, the catalyst material and its byproducts that remain
present in the polycrystalline diamond body after the HPHT process
may promote back-conversion of diamond to non-diamond carbon forms
and may induce stress into the diamond lattice due to the mismatch
in the thermal expansion of the materials. The performance of the
PCD cutting element at elevated temperature may be referred to as
the "thermally stable" performance of the cutting element.
[0028] It is conventionally known to remove or deplete portions of
the catalyst material to improve the thermal stability of the
diamond body. The most common method of removing the catalyst
material is a leaching process in which the PCD compact is
introduced to a leaching agent, for example, an aqueous acid
solution. The leaching agent may be selected from a variety of
conventionally-known compositions in which the catalyst material is
known to dissolve. By dissolving and removing at least a portion of
the catalyst material from the PCD compact, the service life of the
PCD compact may be increased due to the reduction in
back-conversion rate of the diamond in the polycrystalline diamond
body to non-diamond carbon forms and the reduction in materials
having mismatched thermal expansion. However, a portion of catalyst
material may still remain in the diamond body of the PCD compact
that have been subjected to the leaching process. The interstitial
regions between diamond grains may form "trapped" or "entrained"
volumes into which the leaching agent has limited or no
accessibility. Therefore, these trapped volumes remain populated
with the constituents of the PCD formation process. The trapped
volumes that contain catalyst material contribute to the
degradation of the abrasion resistance of the PCD cutting element
at elevated temperature that is generated during use of the PCD
cutting element to remove material. Thus, reduction of trapped
catalyst material may improve the abrasion resistance of PCD
compact cutting elements.
[0029] The present disclosure is directed to polycrystalline
diamond cutting elements that incorporate lead or lead alloy that
is distributed throughout the polycrystalline diamond body. In one
embodiment, the lead or lead alloy may be lead or lead alloy having
at least about 90 wt. % lead. The lead or lead alloy may be
introduced to the diamond particles prior to or concurrently with
the HPHT process. The lead or lead alloy may be distributed
throughout the polycrystalline diamond body evenly or unevenly, as
well as by forming a distribution pattern. The lead or lead alloy
may reduce the amount of catalyst material that is present in the
polycrystalline diamond body following the HPHT process. Further,
the lead or lead alloy may reduce the amount of catalyst material
that is present in the polycrystalline diamond body following a
leaching process in which at least portions of both the lead or
lead alloy and the catalyst material are removed from the
interstitial regions of the polycrystalline diamond body.
Additionally, the lead or lead alloy may increase the removal rate
(or the "leaching rate") of the catalyst material from the
polycrystalline diamond body. In some embodiments, the lead or lead
alloy coats the diamond grains, thereby maintaining a spacing
between the catalyst material and the diamond grains for a
plurality of diamond grains in the diamond body.
[0030] Because of the reduction of the catalyst material in the
polycrystalline diamond body and because of the separation between
the diamond grains and the catalyst material, polycrystalline
diamond cutting elements according to the present disclosure
exhibit performance that exceeds that of conventional PCD cutting
elements in at least one of toughness, strength, and abrasion
resistance.
[0031] Referring now to FIGS. 1 and 2, a PCD cutting element 100 is
depicted. The PCD cutting element 100 includes a substrate 110 and
a polycrystalline diamond body 120 that is attached to the
substrate 110. The polycrystalline diamond body 120 includes a
plurality of diamond grains 122 that are bonded to one another,
including being bonded to one another through inter-diamond
bonding. The bonded diamond grains 122 form a diamond lattice that
extends along the polycrystalline diamond body 120. The diamond
body 120 also includes a plurality of interstitial regions 124
between the diamond grains. The interstitial regions 124 represent
a space between the diamond grains. In at least some of the
interstitial regions 124, a non-carbon material is present. in some
of the interstitial regions 124, lead or lead alloy is present. In
other interstitial regions 124, catalyst material is present. In
yet other interstitial regions 124, both lead or lead alloy and
catalyst material are present. In yet other interstitial regions
124, at least one of catalyst material, lead or lead alloy, swept
material of the substrate 110, for example, cemented tungsten
carbide, and reaction by-products of the HPHT process are present.
Non-carbon, lead or lead alloy, or catalyst materials may be bonded
to diamond grains. Alternatively, non-carbon, lead or lead alloy,
or catalyst materials may be not bonded to diamond grains.
[0032] The catalyst material may be selected from a variety of
materials that interact with the diamond particles to form
interparticle diamond bonds. Examples of such materials include,
for example and without limitation, elemental metallic catalyst
such as elements selected from Group VIII of the periodic table,
for example, cobalt, nickel, iron, or alloys thereof, as well as
magnesium, chromium, tantalum, and niobium, metallic alloy
catalysts selected Group IV, V, or VI of the periodic table alloyed
with silver, copper, or gold, alkaline and alkaline earth compounds
or carbonates thereof, and non-metallic elemental catalysts such as
phosphorus and sulphur. The catalyst material may be present in a
greater concentration in the substrate 110 than in the
polycrystalline diamond body 120, and may promote attachment of the
substrate 110 to the polycrystalline diamond body 120 in the HPHT
process, as will be discussed below. The polycrystalline diamond
body 120 may include an attachment region 128 that is rich in
catalyst material promotes bonding between the polycrystalline
diamond body 120 and the substrate 110. In other embodiments, the
concentration of the catalyst material may be greater in the
polycrystalline diamond body 120 than in the substrate 110. In yet
other embodiments, the catalyst material may differ from the
catalyst of the substrate 110. The catalyst material may be a
metallic catalyst reaction-byproduct, for example catalyst-carbon,
catalyst-tungsten, catalyst-chromium, or other catalyst compounds,
which also may have lower catalytic activity towards diamond than a
metallic catalyst.
[0033] The lead or lead alloy may be selected from a variety of
materials that are non-catalytic with the carbon-diamond
conversion. The lead or lead alloy may be generally immiscible with
the catalyst material when both are liquid such that the lead or
lead alloy and the catalyst material do not alloy with one another
when both are liquid. In some embodiments, the lead or lead alloy
may have a lower liquidus or melting temperature than the liquidus
or melting temperature of the catalyst material.
[0034] Both lead or lead allay and catalyst material may be present
in a detectable amount in the polycrystalline diamond body of the
PCD cutting element both before and after subjecting the
polycrystalline diamond body to leaching. Presence of such
materials may be identified by X-ray fluorescence, for example
using a XRF analyzer available from Bruker AXS, Inc. of Madison,
Wis., USA. Presence of such material may also be identified using
X-ray diffraction, energy dispersive spectroscopy, or other
suitable techniques.
[0035] The lead or lead alloy may be introduced to the unbonded
diamond particles prior to the HPHT process that bonds the diamonds
particles in an amount that is in a range from about 0.1 vol. % to
about 5 vol. % of the diamond body 120, for example an amount that
is in a range from about 0.2 vol. % to about 4 vol. % of the
diamond body 120, for example an amount that is in a range from
about 0.5 vol. % to about 3 vol. %. In an exemplary embodiment,
lead or lead alloy may be introduced to the unbonded diamond in an
amount from about 0.33 to about 1.5 vol. %. Following this HPHT
process and leaching, the lead or lead alloy content in the leached
region of the diamond body 120 is reduced by at least about 50%,
including being reduced in a range from about 50% to about 90%.
[0036] In the HPHT process that bonds the diamond particles,
catalyst material may be introduced to the diamond powders. The
catalyst material may be present in an amount that is in a range
from about 0.1 vol. % to about 30 vol. % of the diamond body 120,
for example an amount that is in a range from about 0.3 vol. % to
about 10 vol. % of the diamond body 120, including being an amount
of about 5 vol. % of the diamond body 120. In an exemplary
embodiment, catalyst material may be introduced to the unbonded
diamond is an amount from about 4.5 vol. % to about 6 vol %.
Following this HPHT process and leaching, the catalyst material
content in the leached region of the diamond body 120 is reduced by
at least about 50%, including being reduced in a range from about
50% to about 90%.
[0037] The lead or lead alloy and the catalyst material may be
non-uniformly distributed in the bulk of the polycrystalline
diamond cutting element 100 such that the respective concentrations
of lead or lead alloy and catalyst material vary at different
positions within the polycrystalline diamond body 120. In one
embodiment the lead or lead alloy may be arranged to have a
concentration gradient that is evaluated along a longitudinal axis
102 of the polycrystalline diamond cuffing element 100. The
concentration of the lead or lead alloy may be higher at positions
evaluated distally from the substrate 110 than at positions
evaluated proximally to the substrate 110. In opposite, the
concentration of the catalyst material may be greater at positions
evaluated proximally to the substrate 110 that at positions
evaluated distally from the substrate 110. In yet another
embodiment, the concentrations of the lead or lead alloy and the
catalyst material may undergo a step change when evaluated in a
longitudinal axis 102 of the polycrystalline diamond cutting
element 100. In yet another embodiment, the concentrations of the
lead or lead alloy and the catalyst material may exhibit a variety
of patterns or configurations. Independent of the concentration of
the lead or lead alloy and the catalyst material in the
polycrystalline diamond body 120, however, both lead or lead alloy
and catalyst material may be detectible along surfaces proximately
and distally located relative to the substrate 110.
[0038] In another embodiment, the polycrystalline diamond body 120
may exhibit relatively high amounts of the catalyst material at
positions proximate to the substrate 110 and at which the catalyst
material forms a bond between the polycrystalline diamond body 120
and the substrate 110. In some embodiments, at positions outside of
such an attachment zone, the lead or lead alloy and the catalyst
material maintain the concentration variation described above.
[0039] PCD cutting elements 100 according to the present disclosure
may exhibit improved performance as compared to conventionally
produced PCD cutting elements when evaluated in terms of abrasion
resistance and/or toughness. The performance of PCD cutting
elements 100 according to the present disclosure may particularly
exhibit improved performance when subjected to conditions of
elevated temperature. Such conditions may occur when the PCD
cutting elements 100 are used in material removal operations, for
example, downhole drilling operations in the petroleum industry.
Performance of the PCD cutting element 100 with respect to abrasion
resistance may be quantified in laboratory testing, for example
using a simulated cutting operation in which the PCD cutting
element 100 is used to machine an analogous material that
replicates an end user application.
[0040] In one example used to replicate a downhole drilling
application, the PCD cutting element 100 is held in a vertical
turret lathe ("VTL") to machine granite. Parameters of the VTL test
may be varied to replicate desired test conditions. In one example,
the cutting element that is subjected to the VTL test is water
cooled. In one example, the PCD cutting element 100 was positioned
to maintain a depth of cut of about 0.017 inches/pass at a
cross-feed rate of about 0.17 inches/revolution and a cutting
element velocity of 122 surface feet per minute and a backrake
angle of 15 degrees. The VTL test introduces a wear scar into the
PCD cutting element 100 along the position of contact between the
PCD cutting element 100 and the granite. The size of the wear scar
is compared to the material removed from the granite to evaluate
the abrasion resistance of the PCD cutting element 100. The service
life of the PCI) cutting element 100 may be calculated based on the
material removed from the granite as compared to the size of the
wear scar abrades through the polycrystalline diamond body 120 and
into the substrate 110.
[0041] In another example, the PCD cutting element 100 is subjected
to an interrupted milling test that implements a fly cutting tool
holder and workpiece arrangement in which the PCD cutting element
100 is periodically removes material from a workpiece and then is
brought out of contact with the workpiece. The interrupted milling
test is described in U.S. patent application Ser. No. 13/791,277,
the entire disclosure of which is hereby incorporated by reference.
The interrupted milling test may evaluate thermal resistance of the
PCD cutting element 100.
[0042] In some embodiments, PCD cutting elements 100 according to
the present disclosure exhibit increased abrasion resistance as
compared to conventionally produced PCD cutting elements. In some
embodiments, PCD cutting elements 100 according to the present
disclosure may exhibit at least about 30% less wear with an
equivalent amount of material removed from the granite as compared
to conventionally produced PCD cutting elements, including
exhibiting about 75% less wear than a conventional cutting element,
including exhibiting about 90% less wear than a conventional,
cutting element.
[0043] PCD cutting elements 100 according to the present disclosure
exhibit a lower concentration of catalyst material in trapped
interstitial regions between the bonded diamond grains as compared
to conventionally processed cutting elements. As discussed above,
because the catalyst material that is positioned within the trapped
interstitial regions may contribute to back-conversion of the
diamond grains to non-diamond forms of carbon. The propensity of
the polycrystalline diamond body 120 of the PCD cutting element 100
to back-convert to non-diamond forms of carbon and/or the stress
induced to the polycrystalline diamond body 120 by the mismatch in
thermal expansion of co joined material may be correlated to the
high-temperature abrasion resistance of the PCD cutting element
100. Reducing the amount of the catalyst material within the
trapped interstitial regions between diamond grains of the
polycrystalline diamond body 120 may reduce the rate of
back-conversion of the PCD cutting element 100. Further, reducing
the amount of catalyst material within the trapped interstitial
regions between diamond grains of the polycrystalline diamond body
120 may reduce stress that is induced into the diamond lattice
caused by a mismatch in the thermal expansion of the diamond grains
and the catalyst material. Therefore, the reduction in the catalyst
material within the trapped interstitial regions between the
diamond grains resulting from the introduction of lead or lead
alloy into the polycrystalline diamond body 120, improves
performance of the PCD cutting element 100 as compared to
conventionally produced PCD cutting elements.
[0044] Still referring to FIG. 1, some embodiments of the PCD
cutting element 100 include a crown portion 402 that is positioned
within the polycrystalline diamond body 120 and along a surface
opposite the substrate 110. The crown portion 402 is made from a
material that is dissimilar from the material of the
polycrystalline diamond body 120 and the substrate 110. The crown
portion 402 may extend into the diamond body 120 from the top
surface of the PCD cutting element 100. The crown portion 402 may
extend to a depth that is less than about 1 mm from the substrate
110 including being about 300 .mu.M from the substrate 110. The
crown portion 402 may limit the depth that the catalyst material 94
sweeps into the polycrystalline diamond body 120 from the second
substrate 110 during the second HPHT process. The crown portion 402
may provide locally modified material properties of the PCD cutting
element 100. In one embodiment, the crown portion 402 may include,
in addition to the bonded diamond grains and the lead or lead alloy
and the catalyst material in detectable amounts, a material
selected from the group consisting of aluminum, aluminum carbide,
silicon, and silicon carbide. In some embodiments, the
polycrystalline diamond body 120 may be free of such materials
outside of the attachment region 128.
[0045] PDC cutting elements according to the present disclosure may
be fabricated using so-called "single press" or "double press" HPHT
process. In a single press HPHT process, diamond particles may be
subjected to a high pressure high temperature sintering process in
which diamond particles are subjected to elevated pressure to form
an unbonded diamond volume having a plurality of diamond particles
that contact one another and a plurality of interstitial regions
positioned between adjacent diamond particles. Lead or lead alloy
is melted and collects in interstitial regions. in some
embodiments, the lead or lead alloy may be mixed with the diamond
particles prior to initiation of the HPHT process. In other
embodiments, the lead or lead alloy may be swept into the
interstitial regions between the diamond particles during the HPHT
process from an external source. In yet other embodiments, the lead
or lead alloy may be both mixed with the diamond particles prior to
initiation of the HPHT process and swept into the interstitial
regions between the diamond particles during the HPHT process from
an external source. The volume of lead or lead alloy introduced to
the diamond particles may be less than the total volume of the
interstitial regions of the diamond region, such that the lead or
lead alloy present in the diamond volume cannot fill all of the
interstitial regions between adjacent diamond grains.
[0046] Subsequent to melting of the lead or lead alloy, the
catalyst material may be melted. The lead or lead alloy and the
catalyst material may be selected such that the melting or liquidus
temperature of the lead or lead alloy is lower than the melting or
liquidus temperature of the catalyst material. In some embodiments,
the melting or liquidus temperature of the lead or lead alloy may
be lower than the solidus temperature of the catalyst material. In
some embodiments, the catalyst material may be mixed with the
diamond particles prior to initiation of the HPHT process. In other
embodiments, the catalyst material may be swept into the
interstitial regions between the diamond particles during the HPHT
process from an external source, for example a substrate having a
hard metal composition that includes a metal carbide and a catalyst
material. In yet other embodiments, the catalyst material may be
both mixed with the diamond particles prior to initiation of the
HPHT process and swept into the interstitial regions between the
diamond particles during the HPHT process from an external source.
The components of the reaction cell may be maintained at a
sintering temperature at which the diamond particles, aided by the
catalyst material, form diamond-to-diamond bonds between adjacent
diamond particles. In some embodiments, the lead or lead alloy may
exhibit a lower viscosity than the viscosity of the catalyst
material at the sintering temperature of the HPHT process. The
catalyst material may be forced through the interstitial regions
between diamond particles by the elevated pressure at which the
components of the reaction cell are held. The volume and
composition of the catalyst material may displace portions of the
lead or lead alloy from the interstitial regions between diamond
particles, thereby pushing lead or lead alloy away from many
surfaces of the diamond particles.
[0047] With the catalyst material molten in a liquid state, the
catalyst may dissolve at least a portion of the carbon from the
diamond particles. As is conventionally known, the molten catalyst
material may act as a solvent catalyst that, when cooled, diamond
may re-precipitate from, such that the diamond particles form
diamond-to-diamond bonds between one another, thereby forming a
polycrystalline diamond body. The polycrystalline diamond body
includes a plurality of diamond grains that are coupled to one
another through diamond-to-diamond bonds, and having a plurality of
interstitial regions positioned therebetween. The diamond grains
that are bonded to one another may form an interconnected
continuous diamond matrix of diamond grains. Most of the
interstitial regions between the diamond grains are connected to
one another such that the interstitial regions form an
interconnected continuous matrix of interstitial regions. However,
some of the interstitial regions within the polycrystalline diamond
body may be "trapped" such that they are separated from the
interconnected continuous matrix of interstitial regions. The
polycrystalline diamond body may be attached to a substrate.
Following the HPHT process, the trapped interstitial regions and
the continuous interstitial matrix between the diamond grains may
be tilled with lead or lead alloy, catalyst material, hard metal,
or combinations thereof.
[0048] In such embodiments, the catalyst material that is present
in the trapped interstitial regions and/or the continuous
interstitial matrix may be spaced apart from the diamond grains in
the continuous diamond matrix by the lead or lead alloy. This
result is surprising, because the catalyst material is generally
better at "wetting" the surfaces of the diamond particles than any
lead or lead alloy that is present in the diamond region. Further,
in embodiments according to the present disclosure, some surfaces
of the diamond grains may be coated by the lead or lead alloy, such
that spacing between the diamond grains and the catalyst material
is preserved following the HPHT process.
[0049] As conventionally known, the diamond body may be contacted
with a leaching agent that removes at least a portion of the
materials present in the interstitial regions that are positioned
proximate to the location of leaching agent application. For
example, the polycrystalline diamond body may be submerged in a
leaching agent such that surfaces of the polycrystalline diamond
body contact the leaching agent, while surfaces of the substrate,
to which the polycrystalline diamond body are attached, are
maintained spaced apart from contact with the leaching agent. The
leaching agent may be selected to attack the lead or lead alloy and
the catalyst material while preserving the diamond grains.
[0050] The lead or lead alloy and the catalyst material may undergo
an oxidation-reduction reaction with the leaching agent. The lead
or lead alloy may be more reactive with the leaching agent than the
catalyst material such that the rate of the leaching reaction per
unit distance within the diamond body is faster for diamond bodies
formed with lead or lead alloy and catalyst material as compared to
diamond bodies formed without the introduction of lead or lead
alloy. The lead or lead alloy may exhibit a lower activation energy
than the catalyst material with the leaching agent such that the
rate of reaction is greater for the lead or lead alloy than the
catalyst material.
[0051] The incorporation of lead or lead alloy into the diamond
body during the HPHT process may result in a decrease in the total
catalyst content both prior to and following leaching as compared
to conventional cutting elements that do not include lead or lead
alloy. The decrease in catalyst content as compared to conventional
cutting elements may increase cutting element life by decreasing
internal mechanical stresses attributable to mismatch between the
coefficients of thermal expansion and modulus of the diamond
grains, the lead or lead alloy, and the catalyst material, and any
back-conversion to non-diamond forms of carbon, which may be
accelerated due to the presence of catalyst material. Further, the
increase in leaching rate may reduce manufacturing time associated
with producing a cutting element according to embodiments disclosed
herein, in particular, by reducing the cycle time associated with
leaching the lead or lead alloy and catalyst material from the
interstitial regions of the diamond body.
[0052] Additionally, the incorporation of lead or lead alloy into
the diamond body during the HPHT process may result in a decrease
in the hard metal concentration in the diamond body as compared to
conventional diamond bodies made without the introduction of lead
or lead alloy. Hard metals are typically introduced to the diamond
bodies during the HPHT process from the substrate. In one
embodiment, the hard metal concentration within diamond bodies
according to the present disclosure may be less than 70% of the
hard metal concentration of a conventional diamond body, for
example being less than about 50% of the hard metal concentration
of a conventional diamond body.
[0053] Further, the incorporation of the lead or lead alloy to the
polycrystalline diamond body may modify the microstructural
configuration of the polycrystalline diamond body as compared to
conventional polycrystalline diamond cutting elements. Referring
now to FIG. 3, a transmission electron micrograph of the
microstructure of a polycrystalline diamond cutting element that is
manufactured according to the present disclosure is depicted. In
this embodiment, lead particles were mixed with the diamond
particles prior to positioning the diamond particles in the
refractory cup for manufacturing. Lead particles were added at a
concentration of about 0.5 wt. % of the lead-diamond mixture. The
substrate included cemented tungsten carbide with about 12.5 wt. %
cobalt, which acted as the catalyst in the HPHT process for
sintering the diamond particles. The contents of the cell assembly
used to manufacture the cutting element was subjected to a maximum
temperature of about 1550.degree. C. and a maximum pressure of 7.5
GPa, and were held above the melting temperature of cobalt for
about 3 minutes. The PCD compact recovered from the HPHT process
was further processed according to conventionally known procedures
to a shape of a cutting element.
[0054] Following this processing, portions of the diamond volume
were removed and prepared as a sample for the transmission electron
microscopy. The sample of the diamond volume to be investigated was
prepared using a dual beam focused ion beam ("FIB") to cut and
extract a sufficiently thin section to allow for electron
transmission. The sample was then examined in a transmission
electron microscope ("TEM") at 200 kV.
[0055] The diamond grains (dark grey) are bonded to one another to
form a continuous polycrystalline diamond matrix. The diamond
volume also includes a continuous interstitial matrix (light grey)
that is positioned between the diamond grains at positions spaced
apart from the locations of diamond-to-diamond bonding. Note that
the portion of the diamond volume from which the depicted sample
has been taken from was unleached, such that none of the lead or
lead alloy and catalyst material have been removed.
[0056] Referring to FIGS. 4 and 5, plots of energy dispersive X-ray
spectroscopy data gathered from the location depicted in FIG. 3 are
provided for lead in FIG. 4 and for catalyst material (here,
cobalt) in FIG. 5. As can be seen in FIG. 4, a thin layer of lead
or lead alloy coats portions of the diamond grains. In contrast,
FIG. 5 depicts that cobalt fills the substantial majority of the
remaining portions of the interstitial region.
[0057] The micrographs of FIGS. 4 and 5 indicate that there is a
thin layer of lead or lead alloy that remains on some of the
surfaces of the diamond grains following the HPHT process. The lead
may he present along all of the surfaces of the diamond grain, but
not visible in this sample configuration. Note that this lead or
lead alloy remains present along the surfaces of the diamond grains
following the HPHT process in which catalyst material is melted,
molten catalyst material dissolves portions of the unbonded diamond
particles, and the catalyst material solidifies and re-precipitates
diamond at positions of diamond-to-diamond contact of the diamond
grains in the presence of catalyst material.
[0058] In comparison to a conventional cutting element that does
not include a lead or lead alloy addition, it is believe that
catalyst material remains present along the surfaces of the diamond
grains following subjecting the cutting element to a leaching
process. Therefore, as compared to conventional cutting elements,
cutting elements according to the present disclosure are believed
to have lower catalyst content along the surfaces of the diamond
grains. This reduction in catalyst content may reduce the total
concentration of catalyst in the cutting element.
[0059] Further, the catalyst material positioned along surfaces of
diamond grains of cutting elements according to the present
disclosure may be functionally displaced by lead or lead alloy.
Without being bound by theory, the lead or lead alloy does not have
the same detrimental performance effects relating to the thermal
stability of the diamond volumes on the cutting element when
operating at elevated temperatures. Therefore, by incorporating the
lead or lead alloy along the surfaces of the diamond grain (and
thereby displacing the catalyst material), the thermal stability of
cutting elements according to the present disclosure may be
enhanced as compared to conventional cutting elements that do not
include a lead or lead alloy addition.
[0060] In various embodiments, the lead or lead alloy and the
catalyst material may be selected based on the interactive
properties of the lead or lead alloy and the catalyst material. In
one embodiment, the lead or lead alloy may exhibit a melting or
liquidus temperature that is lower than the melting or liquidus
temperature of the catalyst material. in one embodiment, the lead
or lead alloy may be substantially immiscible with the catalyst
material when both are in a liquid state. Such substantial
immiscibility may be defined as less than about 10 at. % alloying
of the materials. In one embodiment, the lead or a lead alloy may
have greater than about 90 wt. % lead.
[0061] In one manufacturing process, cutting elements may be
produced in a "single press" HPHT process in which diamond
particles are bonded to one another and a substrate to form a
cutting element having an integral diamond body with diamond grains
bonded to one another in diamond-to-diamond bonds and interstitial
regions between the diamond grains. Some of the interstitial
regions include lead or lead alloy, catalyst material, hard metal,
or combinations thereof. Portions of the diamond body are
maintained in contact with a leaching agent that removes
substantially all of the lead or lead alloy and catalyst material
from a leached region positioned at the working surface of the
cutting element and extending toward the substrate to a transition
zone in which the leached region abuts the unleached region that is
rich with lead or lead alloy and catalyst material.
[0062] Referring now to FIG. 6, a flowchart depicting a
manufacturing procedure 200 is provided. Diamond particles 90 are
mixed with the lead or lead alloy 92 in step 202. The size of the
diamond particles 90 may be selected based on the desired
mechanical properties of the polycrystalline diamond cutting
element that is finally produced.. it is generally believed that a
decrease in grain size increases the abrasion resistance of the
polycrystalline diamond cutting element, but decreases the
toughness of the polycrystalline diamond cutting element. Further,
it is generally believed that a decrease in grain size results in
an increase in interstitial volume of the PCD compact. In one
embodiment, the diamond particles 90 may have a single mode median
volumetric particle size distribution (D50) in a range from about
10 .mu.m to about 100 for example having a D50 in a range from
about 14 .mu.m to about 50 .mu.m, for example having a D50 of about
30 .mu.m to about 32 .mu.m. In other embodiments, the diamond
particles 90 may have a D50 of about 14 .mu.m, or about 17 .mu.m,
or about 30 .mu.m, or about 32 .mu.m. In other embodiments, the
diamond particles 90 may have a multimodal particle size, wherein
the diamond particles 90 are selected from two or more single mode
populations having different values of D50, including multimodal
distributions having two, three, or four different values of
D50.
[0063] The lead or lead alloy 92 may be introduced to step 402 as a
powder. In other embodiments, the lead or lead alloy 92 may be
coated onto the unbonded diamond particles. The particle size of
the lead or lead alloy may be in a range from about 0.005 .mu.m to
about 100 .mu.m, for example being in a range from about 10 .mu.m
to about 50 .mu.m.
[0064] The diamond particles 90 and the lead or lead alloy 92 may
be dry mixed with one another using, for example, a commercial
TURBULA (R) Shaker-Mixer available from Glen Mills, Inc. of
Clifton, N.J. or an acoustic mixer available from Resodyn Acoustic
Mixers, Inc. of Butte, Mont. to provide a generally uniform and
well mixed combination. In other embodiments, the mixing particles
may be placed inside a bag or container and held under vacuum or in
a protective atmosphere during the blending process.
[0065] In other embodiments, the lead or lead alloy 92 may be
positioned separately from the diamond particles 90. During the
first HPHT process, the lead or lead alloy 92 may "sweep" from
their original location and through the diamond particles 90,
thereby positioning the lead or lead alloy 92 prior to sintering of
the diamond particles 90. Subsequent to sweeping of the lead or
lead alloy 92, the catalyst material 94 may be swept through the
diamond particles 90 during the first HPHT process, thereby
promoting formation of inter-diamond bonds between the diamond
particles 90 and sintering of the diamond particles 90 to form the
polycrystalline diamond body 120 of the polycrystalline diamond
compact 80.
[0066] The diamond particles 90 and the lead or lead alloy 92 may
be positioned within a cup 142 that is made of a refractory
material, for example tantalum, niobium, vanadium, molybdenum,
tungsten, or zirconium, as shown in step 204. The substrate 110 is
positioned along an open end of the cup 142 and is optionally
welded to the cup 142 to form cell assembly 140 that encloses
diamond particles 90 and the lead or lead alloy 92. The substrate
110 may be selected f um a variety of hard phase materials having
metal carbides including, for example, cemented tungsten carbide,
cemented tantalum carbide, or cemented titanium carbide. In one
embodiment, the substrate 110 may include cemented tungsten carbide
having free carbons, as described in U.S. Provisional Application
Nos. 62/055,673, 62/055,677, and 62/055,679, the entire disclosures
of which are hereby incorporated by reference. The substrate 110
may include a pre-determined quantity of catalyst material 94.
Using a cemented tungsten carbide-cobalt system as an example, the
cobalt is the catalyst material 94 that is infiltrated into the
diamond particles 90 during the HPHT process. In other embodiments,
the cell assembly 140 may include additional catalyst material (not
shown) that is positioned between the substrate 110 and the diamond
particles 90. In further other embodiments, the cell assembly 140
may include lead or lead alloy 92 that is positioned between the
diamond particles 90 and the substrate 110 or between the diamond
particles 90 and the additional catalyst material (not shown).
[0067] The cell assembly 140, which includes the diamond particles
90, the lead or lead alloy 92, and the substrate 110, is introduced
to a press that is capable of and adapted to introduce ultra-high
pressures and elevated temperatures to the cell assembly 140 in an
HPHT process, as shown in step 208. The press type may be a belt
press, a cubic press, or other suitable presses. The pressures and
temperatures of the HPHT process that are introduced to the cell
assembly 140 are transferred to contents of the cell assembly 140.
In particular, the HPHT process introduces pressure and temperature
conditions to the diamond particles 90 at which diamond is stable
and inter-diamond bonds form. The temperature of the HPHT process
may be at least about 1000.degree. C. (e.g., about 1200.degree. C.
to about 1800.degree. C., or about 1300.degree. C. to about
1600.degree. C.) and the pressure of the HPHT process may be at
least 4.0 GPa (e.g., about 4.0 GPa to about 12.0 GPa, or about 5.0
GPa to about 10 GPa, or about 5.0 GPa to about 8.0 GPa) for a time
sufficient for adjacent diamond particles 90 to bond to one
another, thereby forming an integral PCD compact having the
polycrystalline diamond body 120 and the substrate 110 that are
bonded to one another.
[0068] An integral PCD compact 82 having a polycrystalline diamond
body 120 that is bonded to the substrate 110 may be recovered from
the HPHT cell, as depicted in step 210. The introduction of the
lead or lead alloy 92 to the polycrystalline diamond body 120 prior
to the HPHT process may result in a reduction of catalyst material
94 that is present in the polycrystalline diamond body 120
following the HPHT process and prior to initiation of any
subsequent leaching process. As compared to conventional cutting
elements that are produced without the introduction of the lead or
lead alloy 92, unleached diamond bodies 120 produced according to
the present disclosure may contain, for example, about 10% less
catalyst material 94 when evaluated prior to leaching.
[0069] The polycrystalline diamond body 120 may undergo a leaching
process in which the catalyst material, is removed from the
polycrystalline diamond body 120. In one example of a leaching
process, the polycrystalline diamond body 120 is introduced to a
leaching agent of an acid bath to remove the remaining substrate
110 from the polycrystalline diamond body 120, as shown in step
212. The leaching process may also remove lead or lead alloy 92 and
catalyst material 94 from the polycrystalline diamond body 120 that
is accessible to the acid. Suitable acids may be selected based on
the solubility of the lead or lead alloy 92 and the catalyst
material 94 that is present in the polycrystalline diamond body.
Examples of such acids including, for example and without
limitation, ferric chloride, cupric chloride, nitric acid,
hydrochloric acid, hydrofluoric acid, aqua regia, or solutions or
mixtures thereof. The acid bath may be maintained at an
pre-selected temperature to modify the rate of removal of the lead
or lead alloy 92 and the catalyst material 94 from the
polycrystalline diamond body 120, including being in a temperature
range from about 10.degree. C. to about the boiling point of the
leaching agent. In some embodiments, the acid bath may be
maintained at elevated pressures that increase the liquid boiling
temperature and thus allow the use of elevated temperatures, for
example being at a temperature of greater than the boiling point of
the leaching agent at atmospheric pressure. The polycrystalline
diamond body 120 may be subjected to the leaching process for a
time sufficient to remove the desired quantity of lead or lead
alloy 92 and catalyst material 94 from the polycrystalline diamond
body. The polycrystalline diamond body 120 may be subjected to the
leaching process for a time that ranges from about one hour to
about one month, including ranging from about one day to about 7
days.
[0070] In some embodiments, the polycrystalline diamond body 120
may be maintained in the leaching process until the polycrystalline
diamond body 120 is at least partially leached. In polycrystalline
diamond bodies 120 that are partially leached, the exterior regions
of the polycrystalline diamond bodies 120 that are positioned along
the outer surfaces of the polycrystalline diamond bodies 120 have
the accessible interstitial regions depleted of lead or lead alloy
92 and/or catalyst material 94, while the interior regions of the
polycrystalline diamond bodies 120 are rich with lead or lead alloy
92 and/or catalyst material 94. In such partially leached
polycrystalline diamond bodies 120, all of the accessible
interstitial regions between the diamond grains may be fully
depleted of lead or lead alloy 92 and/or catalyst material 94. In
some embodiments, hard metal that is introduced to the
polycrystalline diamond body 120 during the HPHT process may remain
in the accessible interstitial regions.
[0071] In some embodiments, the extent of the leaching may be
monitored by weighing the polycrystalline diamond body 120 after a
pre-defined period of time. As the change in the weight loss of the
polycrystalline diamond body 120 approaches a threshold value (for
example, 10% loss of the unleached polycrystalline diamond body
120), the polycrystalline diamond body 120 may be considered to be
completely leached. Because the polycrystalline diamond body 120 is
leached without the substrate 110, the leach fronts may extend from
opposing sides of the polycrystalline diamond body 120 and from the
perimeter surface of the polycrystalline diamond body 120. When the
leach fronts from the opposing sides of the polycrystalline diamond
body 120 meet, the polycrystalline diamond body 120 may be
considered to be completely leached. In some embodiments, the
extent of leaching may be monitored by the loss of density of the
diamond body.
[0072] In some embodiments, an unleached polycrystalline diamond
body may have lead or lead alloy 92 and catalyst material 94 at
greater than about 4 vol. % of the polycrystalline diamond body
120, including being from about 4 vol. % to about 15 vol. %. In
comparison, a completely leached portion of a polycrystalline
diamond body 120 may have lead or lead alloy 92 and catalyst
material 94 that is less than about 80% less than the unleached
polycrystalline diamond body 120, for example being in a range from
about 60% to about 80% less than the unleached polycrystalline
diamond body 1.20. A completely leached polycrystalline diamond
body 120 may have lead or lead alloy 92 and catalyst material 94
being from about 0.25 vol. % to about 6 vol. %, for example, being
from about 0.2 vol. % to about 1 vol. %. In general, the extent of
loss of lead or lead alloy and catalyst material in a completely
leached polycrystalline diamond body 120 is determined the material
structure and composition, for example by the precursor diamond
grain size and the particle size distribution.
[0073] As discussed above, the introduction of the lead or lead
alloy to the polycrystalline diamond body 120 reduces the
concentration of the catalyst material 94 in the polycrystalline
diamond body 120 prior to any leaching process. Further, subsequent
to leaching regions of the polycrystalline diamond body 120, the
introduction of the lead or lead alloy 92 to the polycrystalline
diamond body 120 also reduces the concentration of the catalyst
material 94 that remains present in the trapped interstitial
volumes of the polycrystalline diamond body 120 of the leached
region of the polycrystalline diamond body 120. As compared to
conventional cutting elements that are produced without the
introduction of the lead or lead alloy 92, diamond bodies 120
produced according to the present disclosure contain from about 30
vol. % to about 90 vol. % less catalyst material 94 following
complete leaching of both of the compared diamond bodies.
[0074] The introduction of the lead or lead alloy 92 to the
polycrystalline diamond body 120 may also increase the leaching
rate of the polycrystalline diamond body 120, such that the
duration of time required to obtain complete leaching of the
polycrystalline diamond body 120 is reduced as compared to
conventionally produced diamond bodies. For example, complete
leaching of the polycrystalline diamond body 120 having lead or
lead alloy 92 according to the present disclosure may be obtained
from about 30% to about 60% less time as compared to conventional
cutting elements that are produced without the introduction of the
lead or lead alloy 92, In one example, when evaluated after 7 days
of introduction to the leaching process, polycrystalline diamond
bodies 120 produced according to the present disclosure exhibited
from about 40% to about 70% more mass loss than conventional PCD
compacts.
[0075] Following substantially complete leaching of the
polycrystalline diamond body 120, the polycrystalline diamond body
120 continues to exhibit non-diamond components that are present in
the trapped interstitial regions of the polycrystalline diamond
body 120 that are positioned between bonded diamond grains in at
least detectable amounts. However, the reduction of the non-diamond
components (including catalyst material 94) in the leaching process
accessible interstitial regions reduces the content of catalyst
material 94 in the polycrystalline diamond body 120 and increases
the thermal stability of the polycrystalline diamond body 120.
[0076] Following formation of the integral PCD compact 82, the PCD
compact 82 may be processed through a variety of finishing
operations to remove excess material from the PCD compact 82 and
configure the PCD compact 82 for use by an end user, including
formation of a cutting element 84, as shown in step 418. Such
finishing operations may include, for example, grinding and
polishing the outside diameter of the PCD compact 82, cutting,
grinding, lapping, and polishing the opposing faces (both the
support-substrate-side face and the diamond-body-side face) of the
PCD compact 82, and grinding and lapping a chamfer into the PCD
compact 82 between the diamond-body-side face and the outer
diameter of the PCD compact 82.
[0077] In an alternative manufacturing process, cutting elements
may be produced in a "double press" HPHT process in which diamond
particles are bonded to one another to form the diamond body in a
first HPHT process, the diamond body is fully leached of lead or
lead alloy and catalyst material from the interstitial regions
between the diamond grains, and the diamond body is attached to a
substrate in a second. HPHT process. The diamond particles may
first be subjected to a first HPHT process to form a
polycrystalline diamond compact having a polycrystalline diamond
body that is formed through sintering with a catalyst material
source. In one embodiment, the catalyst material source is provided
integrally with a substrate (a first substrate). Substantially all
of the substrate is removed from the polycrystalline diamond body,
the polycrystalline diamond body is machined to a desired shape,
and the polycrystalline diamond body is leached to remove
substantially all of the accessible lead or lead alloy and catalyst
material from the interstitial regions of the polycrystalline
diamond body. The leached polycrystalline diamond body is
subsequently cleaned of leaching debris and bonded to a substrate
in a second HPHT process, thus forming a PCD compact. This PCD
compact is subsequently finished according to conventionally known
procedures to the final shape desirable of the PCD cutting elements
for the end user application.
[0078] Referring now to FIG. 7, a plurality of PCD cutting elements
100 according to the present disclosure may be installed in a drill
bit 310, as conventionally known, to perform a downhole drilling
operation. The drill bit 310 may be positioned on a drilling
assembly 300 that includes a drilling motor 302 that applies torque
to the drill bit 310 and an axial drive mechanism 304 that is
coupled to the drilling assembly for moving the drilling assembly
300 through a borehole and operable to modify the axial force
applied by the drill bit 310 in the borehole. Force applied to the
drill bit 310 is referred to as "Weight on Bit" ("WOB"). The
drilling assembly 300 may also include a steering mechanism that
modifies the axial orientation of the drill assembly 300, such that
the drill bit 310 can be positioned for non-linear downhole
[0079] The drill bit 310 includes a stationary portion 312 and a
material removal portion 314. The material removal portion 314 may
rotate relative to the stationary portion 312. Torque applied by
the drilling motor 302 rotates the material removal portion 314
relative to the stationary portion 312. A plurality of PCD cutting
elements 100 according to the present disclosure are coupled to the
material removal portion 314. The plurality of PCD cutting elements
100 may be coupled to the material removal portion 314 by a variety
of conventionally known methods, including attaching the plurality
of PCD cutting elements 100 to a corresponding plurality of shanks
316 that are coupled to the material removal portion 314. The PCD
cutting elementss 100 may be coupled to the plurality of shanks 316
by a variety of methods, including, for example, brazing, adhesive
bonding, or mechanical affixation. In embodiments in which the PCD
cutting elements 100 are brazed to the shanks 316 with a braze
filler 318, at least a portion of the shanks 316, the braze filler
318, and at least a portion of the substrate 110 of the PCD cutting
elements 100 is heated to an elevated temperature while in contact
with one another. As the components decrease in temperature, the
braze filler 318 solidifies and forms a bond between the substrate
110 of the PCD cutting elements 100 and the shanks 316 of the
material removal portion 314. In one embodiment, the brazing filler
318 has a melting temperature that is greater than a melting
temperature of the lead or lead alloy of the polycrystalline
diamond body 120 at ambient pressure conditions. In another
embodiment, the brazing filler 318 has a melting temperature that
is less than the catalyst material 94 of the polycrystalline
diamond body 120 at ambient pressure conditions. In yet another
embodiment, the brazing filler 318 has a melting temperature that
is less than the liquidus temperature of the catalyst material of
the polycrystalline diamond body at ambient pressure
conditions.
[0080] When the drill bit 310 is positioned in the borehole, the
material removal portion 314 rotates about the stationary portion
312 to reposition the PCD cutting elements 100 relative to the
borehole, thereby removing surrounding material from the borehole.
Force is applied to the drill bit 310 by the axial drive mechanism
304 in generally the axial orientation of the drill bit 310. The
axial drive mechanism 304 may increase the WOB, thereby increasing
the contact force between the PCD cutting elements 100 and the
material of the borehole. As the material removal portion 31.4 of
the drill bit 310 continues to rotate and WOB is maintained on the
drill bit 310, the PCD cutting elements 100 abrade material of the
borehole, and continue the path of the borehole in an orientation
that generally corresponds to the axial direction of the drill bit
310.
[0081] It should now be understood that PCD cutting elements
according to the present disclosure include a lead or lead alloy
addition to the diamond volume that is positioned within
interstitial regions between adjacent diamond grains. The lead or
lead alloy may reduce contact between the diamond grains and a
catalyst material that the diamond grains dissolve into when the
catalyst material is molten. By preserving spacing between the
catalyst material and the diamond grains, the PCD cutting element
may exhibit improved performance at elevated temperatures as
compared to conventional PCD cutting elements.
* * * * *