U.S. patent application number 17/704437 was filed with the patent office on 2022-07-21 for polycrystalline diamond composite compact element, tools incorporating same and method for making same.
The applicant listed for this patent is Element Six (Production) (Pty) Ltd.. Invention is credited to Geoffrey John DAVIES, Roger William Nigel NILEN, Mhlonishwa Cyprian NZAMA.
Application Number | 20220226965 17/704437 |
Document ID | / |
Family ID | |
Filed Date | 2022-07-21 |
United States Patent
Application |
20220226965 |
Kind Code |
A1 |
DAVIES; Geoffrey John ; et
al. |
July 21, 2022 |
POLYCRYSTALLINE DIAMOND COMPOSITE COMPACT ELEMENT, TOOLS
INCORPORATING SAME AND METHOD FOR MAKING SAME
Abstract
The invention relates to a PCD composite compact element
comprising a PCD structure integrally bonded at an interface to a
cemented carbide substrate; the PCD structure comprising coherently
bonded diamond grains having a mean size no greater than 15
microns; the cemented carbide substrate comprising carbide
particles dispersed in a metallic binder, the carbide particles
comprising a carbide compound of a metal; wherein the ratio of the
amount of metallic binder to the amount of the metal at points in
the substrate deviates from a mean value by at most 20 percent of
the mean value. The invention further relates to a method for
making a PDC compact element comprising a PCD structure integrally
bonded to a substrate formed of cemented carbide; the method
including introducing a source of excess carbon to the substrate at
a bonding surface of the substrate to form a carburised substrate;
contacting an aggregated mass of diamond grains with the carburised
substrate; and sintering the diamond grains in the presence of a
solvent/catalyst material for diamond; wherein the mean size of the
diamond grains in the aggregated mass is no greater than 30
microns.
Inventors: |
DAVIES; Geoffrey John;
(Springs, ZA) ; NZAMA; Mhlonishwa Cyprian;
(Springs, ZA) ; NILEN; Roger William Nigel;
(Springs, ZA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Element Six (Production) (Pty) Ltd. |
Springs |
|
ZA |
|
|
Appl. No.: |
17/704437 |
Filed: |
March 25, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16933531 |
Jul 20, 2020 |
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17704437 |
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16048887 |
Jul 30, 2018 |
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16933531 |
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15052086 |
Feb 24, 2016 |
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16048887 |
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13124867 |
Jun 23, 2011 |
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PCT/IB2009/054645 |
Oct 21, 2009 |
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15052086 |
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International
Class: |
B24D 3/10 20060101
B24D003/10; B22F 7/06 20060101 B22F007/06; C22C 26/00 20060101
C22C026/00; C22C 29/06 20060101 C22C029/06; E21B 10/46 20060101
E21B010/46; E21B 10/573 20060101 E21B010/573; B23B 27/14 20060101
B23B027/14; B24D 18/00 20060101 B24D018/00; E21B 10/567 20060101
E21B010/567 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 21, 2008 |
GB |
0819257.7 |
Claims
1. A method for making a polycrystalline diamond composite (PDC)
compact element comprising a polycrystalline diamond (PCD)
structure integrally bonded to a substrate formed of cemented
carbide; the method including introducing a source of excess carbon
to the substrate at or proximate a bonding surface of the substrate
to form a carburised substrate or carburised substrate assembly;
contacting an aggregated mass of diamond grains with the carburised
substrate or carburised substrate assembly adjacent or proximate
the bonding surface to form an unbonded assembly; and sintering the
diamond grains in the presence of a solvent/catalyst material for
diamond at a temperature and pressure at which diamond is
thermodynamically stable to form POD; wherein the mean size of the
diamond grains in the aggregated mass is no greater than about 30
microns.
2. A method according to claim 1, including introducing at least
0.1 weight percent source of excess carbon to the substrate at or
proximate the bonding surface of the substrate wherein the weight
percent is expressed as of the total substrate material within the
region in which the carbon is introduced.
3. A method according to claim 1, including forming the aggregated
mass from diamond grains having a multi-modal size
distribution.
4. A method according to claim 1, wherein the source of excess
carbon is in the form of carbon black powder or graphite.
5. A method according to claim 1, including introducing diamond to
the substrate at or proximate the bonding surface of the substrate
and converting at least some of the diamond into graphite to serve
as a source of excess carbon.
6. A method according to claim 1, including combining source of
excess carbon in particulate or granular form with raw materials
for the cemented carbide, forming the combination into a
substantially self-supporting green body, and sintering the green
body at a pressure at which diamond is not thermodynamically
stable.
7. A method according to claim 1, including combining diamond
grains with raw materials for cemented carbide, forming the
combination into a substantially self-supporting green body;
subjecting the green body to a temperature of at least 500 degrees
centigrade and a pressure at which diamond is not thermodynamically
stable.
8. A method according to claim 1, including introducing refractory
metal carbide particles into the aggregated mass of diamond grains,
the refractory metal carbide particles being selected from the
group consisting of tungsten carbide, tantalum carbide, niobium
carbide and vanadium carbide and/or introducing a refractory metal
precursor for metal carbide into the aggregated mass of diamond
grains, the refractory metal being selected from the group
consisting of tungsten, tantalum, niobium and vanadium in
non-carbide compound or in elemental form.
9. A method according to claim 1, wherein the step of introducing
the source of excess carbon comprises dispersing the source of
excess carbon is throughout the volume of the carburised substrate
or carburised substrate assembly.
10. A method according to claim 1, wherein prior to the step of
contacting the aggregated mass of diamond grains with the
carburised substrate or carburised substrate assembly the method
further comprising forming the carburised substrate by sintering a
mixture comprising tungsten carbide grains, a binder material and
the source of excess carbon.
11. A method according to claim 1, wherein the step of introducing
the source of excess carbon comprises introducing no greater than
about 10 weight percent of the of the source of excess carbon in
the surface region or the substrate.
12. A method according to claim 1, wherein the content of the
source of excess carbon within the surface region or throughout the
entire carburised substrate is at least about 0.1 weight percent of
the surface region or substrate.
13. A method according to claim 1, wherein the content of the
source of excess carbon within the surface region or throughout the
entire carburised substrate is at least about 0.3 weight percent of
the surface region or substrate.
14. A method according to claim 1, wherein the surface region
extends to a depth of at least about 1 mm, at least about 2 mm, or
even at least 3 mm from the bonding surface.
15. A method according to claim 1, wherein the source of excess
carbon is introduced in the form of a gas.
16. A method according to claim 1, comprising combining the source
of excess carbon in particulate or granular form with raw materials
for the cemented carbide, forming the combination into a
substantially self-supporting green body, and sintering the green
body at a pressure at which diamond is not thermodynamically stable
to form the carburised substrate
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 16/933,531, filed on Jul. 20, 2020, which is a
continuation of U.S. patent application Ser. No. 16/048,887, filed
on Jul. 30, 2018, which is a continuation of U.S. patent
application Ser. No. 15/052,086, filed on Feb. 24, 2016, which is a
continuation of U.S. patent application Ser. No. 13/124,867, filed
on Jun. 23, 2011, which is the National Stage of International
Application No. PCT/IB2009/054645, filed on Oct. 21, 2009, which
claims benefit of U.K. Patent Application Serial No. 0819257.7,
filed on Oct. 21, 2008, all of which are incorporated by reference
in their entireties as if recited in full herein.
FIELD
[0002] The invention relates to polycrystalline diamond (PCD)
composite compacts comprising a PCD structure bonded to a cemented
carbide substrate, tools incorporating same and methods for making
same.
BACKGROUND
[0003] Polycrystalline diamond (PCD) is a super-hard material
comprising a mass of inter-grown diamond grains and interstices
between the diamond grains. PCD is typically made by subjecting an
aggregated mass of diamond grains to an ultra-high pressure of at
least about 5.5 GPa and temperature of at least about 1,400 degrees
centigrade. As used herein, the term polycrystalline diamond, or
PCD, is understood to mean a material that comprises at least 80
volume percent of diamond grains, a substantial portion of which
are directly inter-bonded, alternatively referred to as coherently
bonded. Material wholly or partly filling the interstices is
referred to as filler material. PCD is typically formed in the
presence of a sintering aid such as cobalt, which promotes the
inter-growth of diamond grains. The sintering aid is commonly
referred to as a solvent/catalyst material for diamond, owing to
its function of dissolving diamond to some extent and catalysing
its re-precipitation. A solvent/catalyst material for diamond is
understood to be a material capable of promoting the growth of
diamond and the formation of direct diamond-to-diamond bonds at a
temperature and pressure at which diamond is thermodynamically
stable. Generally preferred solvent/catalyst materials are Fe, Ni,
Co and Mn, and alloys including any of these. Consequently the
interstices within the sintered PCD product are wholly or partially
filled with residual solvent/catalyst material. Typically, PCD is
often formed on a cobalt-cemented tungsten carbide substrate, which
provides a source of cobalt solvent/catalyst for the PCD.
[0004] PCD is used in a wide variety of tools for cutting,
machining, drilling or degrading hard or abrasive materials such as
rock, metal, ceramics, composites and wood-containing materials.
For example, PCD inserts are widely used within drill bits used for
boring into the earth in the oil and gas drilling industry. In many
of these applications the temperature of the PCD material becomes
elevated as it engages a rock formation, workpiece or body with
high energy. Unfortunately, mechanical properties of PCD such as
hardness and strength tend to deteriorate at high temperatures,
largely as a result of residual solvent/catalyst material dispersed
within it.
[0005] U.S. Pat. No. 4,694,914 discloses an insert including at
least one outer layer containing polycrystalline diamond and at
least one transition layer between the polycrystalline diamond
layer and the cemented carbide body. The transition layer comprises
a composite material containing diamond crystals, cobalt and
pre-cemented tungsten carbide particles.
[0006] U.S. Pat. No. 4,694,918 discloses inserts including a
cemented metal carbide insert body, an outer layer of
polycrystalline diamond, and at least one transition layer of a
composite material. The composite material includes polycrystalline
diamond and particles of pre-cemented metal carbide.
[0007] Delwiche et al. (Petroleum Division, v 40, and Drilling
Technology 1992, 1992, p 51-60, American Society of Mechanical
Engineers) disclose PCD inserts for oil and gas drilling, wherein a
PCD layer is secured to a substrate comprising a back-up component
containing coarse diamond grains dispersed within a matrix of
cemented carbide.
[0008] There is a need to provide composite PCD compacts comprising
a PCD structure, and particularly a PCD structure formed from fine
or ultra-fine grains of diamond, bonded to a cemented carbide
substrate and having reduced defects proximate the interface
between the PCD structure and the cemented carbide substrate.
SUMMARY
[0009] According to a first aspect of the invention there is
provided a PCD composite compact element comprising a PCD structure
integrally bonded at an interface to a cemented carbide substrate;
the PCD structure comprising coherently bonded diamond grains
having a mean size no greater than about 30 microns, preferably no
greater than about 20 microns, more preferably no greater than
about 15 microns, even more preferably no greater than about 10
microns, yet more preferably no greater than about 5 microns, still
more preferably no greater than about 2 microns, and even more
preferably no greater than about 1 micron; the cemented carbide
substrate comprising carbide particles dispersed in a metallic
binder, the carbide particles comprising a carbide compound of a
metal; wherein the ratio of the amount of metallic binder to the
amount of the metal at points in the substrate deviates from a mean
value by at most about 20 percent of the mean value.
[0010] In one embodiment the ratio of the amount of metallic binder
to the amount of the metal at points in the substrate deviates from
a mean value by at most about 20 percent of the mean value from the
interface to a depth of at least 2 mm into the substrate.
[0011] Embodiments of this aspect of the invention have been found
to exhibit reduced exaggerated grain growth proximate the interface
between the PCD structure and the substrate, and are believed to be
even more advantageous the lower the mean diamond grain size within
the PCD structure.
[0012] In one embodiment of this aspect to the invention, the ratio
of the amount of metallic binder to the amount of the metal at
points in the substrate deviates from the mean value by at most
about 10 percent of the mean value.
[0013] In some embodiments, the mean size of the diamond grains may
be at least about 0.05 microns or at least about 0.1 microns.
[0014] In some embodiments the metal of the carbide particles may
be a refractory metal such as W, or even Ti, Ta, or Cr, and in some
embodiments the metallic binder comprises a solvent/catalyst for
diamond, such as Co.
[0015] In some embodiments diamond particles are dispersed within a
surface region of the substrate or substantially throughout the
entire substrate. In some embodiments, the content of the diamond
particles within the surface region or within the substrate may be
no greater than about 6 weight percent or no greater than about 5.5
weight percent of the material in the surface region or in the
substrate as the case may be. In some embodiments, the content of
the diamond particles within the surface region or within the
substrate may be at least about 0.1 weight percent or at least
about 0.3 weight percent. The surface region of the substrate may
extend from the interface to a depth of at least about 1 mm, at
least about 2 mm, or even at least 3 mm. In some embodiments, the
surface region extends from the interface and has a volume of at
least 2 times that of the PCD structure or at least 3 times that of
the PCD structure. In some embodiments the volume of the surface
region extending from the interface may be at least ten times
greater than the volume of the PCD structure.
[0016] In some embodiments, the diamond particles dispersed in the
substrate or in the surface region of the substrate have mean size
in the range from 0.1 to 100 microns, 0.1 to 50 microns or even 0.1
to 20 microns. In some embodiments the diamond particles may be
substantially uniformly dispersed throughout the substrate or the
surface region of the substrate. This may help reduce the
occurrence of grain growth-related defects more uniformly over the
interfacial area.
[0017] In some embodiments, the diamond content within the
substrate or within the surface region of the substrate may be at
least 1 volume percent, at least 2 volume percent and less than 20
volume percent, in the range from 1 to 15 volume percent, or in the
range from 1 to 10 volume percent. It has been found that diamond
content within these ranges may be sufficient to substantially
reduce certain defects proximate the interface.
[0018] In some embodiments the PCD structure comprises a first and
a second region, the mean size of the diamond grains of the first
region being greater than that of the diamond grains in the second
region; the first region being proximate the substrate and the
second region being remote from the substrate. In one embodiment
the second region defines a working surface.
[0019] In some embodiments, the mean size of the diamond grains in
the first region of the PCD structure may be greater than 2 microns
and the mean size of the diamond grains in the second region of the
PCD structure may be in the range from 0.01 micron to 1.5 microns
or in the range from 0.01 micron to 1 micron. These embodiments may
have substantially reduced incidence of grain growth defects
proximate the interface between the PCD structure and the substrate
in the case of very fine-grained PCD structures. Very fine-grained
(less than about 2 microns) PCD structures may be desirable because
they have certain desirable mechanical properties, such as
increased toughness.
[0020] The PCD structure may have an axial thickness of at least 1
mm from an interface with the substrate.
[0021] The ratio of the amount of metallic binder to the amount of
carbon at points in the PCD structure may be substantially constant
about a mean value, from the interface to a depth of at least 0.5
mm, more preferably at least 0.75 mm and yet more preferably at
least 1 mm into the PCD structure. In one embodiment, the ratio of
the amount of metallic binder to the amount of carbon at points in
the PCD structure deviates from the mean value by at most 20
percent of the mean value, more preferably at most about 10 percent
from the mean value.
[0022] The substrate may have a thickness of at least 1 mm, at
least 1.5 mm or at least 5 mm.
[0023] The diamond grains in PCD structure may have a multi-modal
size distribution. In some embodiments the bonded diamond grains of
the PCD structure have the size distribution characteristic that at
least 50 percent of the grains have mean size greater than 5
microns, and at least 20 percent of the grains have mean size in
the range from 10 to 15 microns. Embodiments of PCD structures
having a multi-modal diamond grain size distribution and mean grain
size within these ranges have been found to have sufficient
strength to retain better their mechanical integrity and key
properties after bonding to the substrate, such as by brazing.
[0024] In one embodiment a plurality of PCD or diamond-rich fingers
extend from the PCD structure into the substrate, more preferably a
plurality of PCD fingers extend from the PCD structure into the
substrate, a finger being a generally elongate structure. In some
embodiments, at least one of the PCD fingers has length at least 20
microns, at least 30 microns, or at least 40 microns.
[0025] Embodiments of a PCD composite compact element according to
the invention may be made using an embodiment of the method
according to an aspect of the invention.
[0026] Excess carbon is understood to be carbon that is in excess
of the diamond of the diamond grains provided in the aggregated
mass for sintering PCD, and is also in excess of the carbon
included as the carbide of the cemented carbide (stochiometric
excess). A carburised substrate or carburised substrate assembly is
therefore a substrate or substrate assembly including excess
carbon.
[0027] A green body is a term known in the art and refers to an
article intended to be sintered, but which has not yet been
sintered. It is generally self-supporting and has the general form
of the intended finished article. A green body is typically formed
by combining a plurality of particles in a vessel and then
compacting them to form self-supporting article.
[0028] Carbon may be introduced into the substrate in any of a
number of ways. In one embodiment a substrate pre-form is prepared
by a method including introducing diamond particles into the
starting powders for making a cemented carbide to form a starting
powder blend; forming the starting powder blend by means of
compaction in a mould to form a green body; and sintering the green
body at a temperature of greater than about 1,400 degrees
centigrade at an applied pressure of less than about 1 GPa to
produce a sintered substrate. At least some of the diamond
particles are converted wholly or partially into graphite during
this carbide sintering step, because the pressure is below that for
diamond to be thermodynamically stable.
[0029] The sintering pressure at which diamond is thermodynamically
stable is preferably at least about 5.5 GPa and the temperature is
preferably at least about 1,400 degrees centigrade.
[0030] In some embodiments, carbon is introduced into the substrate
in the form of graphite powder.
[0031] In some embodiments, carbon is introduced into the substrate
in the form of carbonaceous gas, which is caused to permeate or
infiltrate the substrate.
[0032] In some embodiments, material comprising carbon is sprayed
onto a surface of the substrate. In particular, powder containing
cobalt, carbon and tungsten may be deposited onto the substrate
surface by means of thermal spraying.
[0033] In some embodiments, the substrate is coated with a source
of excess carbon, such as graphite.
[0034] In some embodiments, the substrate is prepared from starting
carbide powder having a high content of carbon in the form of
carbon black, for example.
[0035] In some embodiments, a substrate with high carbon content is
prepared by avoiding the removal of some carbon during the
preparation of the green body for readiness for sintering.
Typically, a green body is heat treated to remove binder or
pressing aid material prior to sintering, and carbon is removed
during this process. In one embodiment, this process is not
thoroughly completed, leaving at least some carbon of binder origin
within the green body.
[0036] The size distribution of unbonded or free-flowing diamond
grains is measured by means of a laser diffraction method, wherein
the grains are suspended in a fluid medium and an optical
diffraction pattern is obtained by directing a laser beam at the
suspension. The diffraction pattern is interpreted by computer
software and the size distribution is expressed in terms of
equivalent circle diameter. In effect, the grains are treated as
being spherical and the size distribution is expressed in terms of
a distribution of equivalent diameters of spheres. A
Mastersizer.TM. apparatus from Malvern Instruments Ltd, United
Kingdom, may be used for his purpose.
[0037] A multi-modal size distribution of a mass of grains is
understood to mean that the grains have a size distribution that is
formed of more than one peak, each peak corresponding to a
respective "mode". Multimodal polycrystalline bodies are typically
made by providing more than one source of a plurality of grains,
each source comprising grains having a substantially different mean
size, and blending together the grains from the sources.
Measurement of the size distribution of the blended grains
typically reveals distinct peaks corresponding to distinct modes.
When the grains are sintered together to form the polycrystalline
body, their size distribution is further altered as the grains are
compacted against one another and fractured, resulting in the
overall decrease in the sizes of the grains. Nevertheless, the
multimodality of the grains is usually still clearly evident from
image analysis of the sintered article.
[0038] In order to obtain a measure of the sizes of diamond grains
within PCD, a method known as "equivalent circle diameter" is used.
In this method, a scanning electron micrograph (SEM) image of a
polished surface of the PCD material is used. The magnification and
contrast should be sufficient for at least several hundred diamond
grains to be identified within the image. The diamond grains can be
distinguished from metallic phases in the image a circle equivalent
in size for each individual diamond grain can be determined by
means of conventional image analysis software. The collected
distribution of these circles is then evaluated statistically.
Wherever diamond mean grain size within PCD material is referred to
herein, it is understood that this refers to the mean equivalent
circle diameter.
[0039] "Binder pooling" refers to the existence of a region within
the PCD structure adjacent the interface, the region having a
substantially higher content of binder material (typically cobalt)
than the mean or desired content within the PCD structure. The
diamond content within the pooling region may be less than 50% in
known PCD compacts, particularly those having a cemented carbide
substrate thicker than about 1 millimetre and a PCD structure
having thickness greater than about 0.6 millimetres. Pooling is a
problem particularly in PCD compacts having relatively thick
substrate and PCD structure. A corresponding region occurs within
the substrate adjacent the interface, wherein the content of binder
material is lower than the mean for the substrate. This is
sometimes called a "binder denuded zone". Binder pooling and
depletion may be undesirable because it is associated with several
related defects, including so-called "plume" defects and
exaggerated diamond grain growth, and because it reduces the
abrasion resistance of the compact in a region adjacent the
interface. Reduced abrasion resistance at the interface may result
in under-cutting of the PCD structure, which may be accelerated by
the presence of erosion-promoting material in the environment.
[0040] Plume defects are relatively large grains of metal carbide
formed within the PCD structure proximate the interface. While
wanting not to be bound by theory, it is believed that plumes may
be reduced in embodiments of the invention because material
infiltrating from the substrate into the PCD during the sintering
step has reduced tungsten content or is substantially free of
tungsten.
[0041] Embodiments of the method of the invention may also result
in reduced exaggerated grain growth of diamond within the PCD,
which is more a problem the finer the diamond grains starting
aggregated mass. For this reason the method is particularly
advantageous where the mean grain size within the PCD is low. While
wanting not to be bound by theory, when plumes of molten binder
material, e.g. cobalt, invade the diamond layer and the plumes have
a relatively low content of carbon, fine diamond grains readily
dissolve and re-precipitate onto the larger grains, resulting in
exaggerated grain diamond grain growth proximate the interface
between the PCD structure and the substrate. The resulting grains
can be an order of magnitude greater than the starting grain size.
However, when the binder material contains relatively more carbon,
as is the case where the source of excess carbon has been
introduced into the substrate prior to the sintering step, then
dissolution of finer grains is suppressed or retarded and instead,
the carbon precipitates evenly onto all grains. Since this
precipitation is spread out over many grains, there is little or
reduced exaggerated grain growth.
[0042] Substantially constant is understood to mean that the ratio
is a constant value with a statistical confidence interval of at
least 68 percent, or even 90 or 95 percent.
[0043] The ratio of the amount of binder material in the substrate
to the amount of carbide material within the substrate, and the
ratio of amount of binder material to the amount of diamond within
the PCD structure may be expressed as a weight ratio, volume ratio
or other ratio indicative of the relative amounts of binder
material and carbide material, or of binder material and diamond,
respectively. The ratio may be expressed as a percentage value.
[0044] Where the substrate contains diamond particles in a region
adjacent the interface with the PCD structure, it has been found
that a type of "reverse pluming" occurs, where PCD "fingers" extend
from the PCD structure into the region. It is hypothesised that
these fingers may result in reduced internal stress proximate the
interface and reduced incidence of delamination of the structure.
The size of the fingers may be controlled by selecting the size of
the diamond particles introduced into the substrate green body; the
longer the fingers desired, the larger should be the diamond
particles, in general. The number of fingers and to some extent
their size is controlled by the number of diamond particles
introduced into the substrate.
[0045] According to a second aspect to the present invention there
is provided a method for making a polycrystalline diamond composite
(PDC) compact element comprising a polycrystalline diamond (PCD)
structure integrally bonded to a substrate formed of cemented
carbide; the method including introducing a source of excess carbon
to the substrate at or proximate a bonding surface of the substrate
to form a carburised substrate or carburised substrate assembly;
contacting an aggregated mass of diamond grains with the carburised
substrate or carburised substrate assembly adjacent or proximate
the bonding surface to form an unbonded assembly; and sintering the
diamond grains in the presence of a solvent/catalyst material for
diamond at a temperature and pressure at which diamond is
thermodynamically stable to form POD; wherein the mean size of the
diamond grains in the aggregated mass is no greater than about 30
microns.
[0046] The mean size of the diamond grains in the aggregated mass
may be no greater than about 20 microns, preferably no greater than
about 15 microns, even more preferably no greater than about 10
microns, yet more preferably no greater than about 5 microns, still
more preferably no greater than about 2 microns and even more
preferably no greater than about 1 micron.
[0047] Preferably, the mean size of the diamond grains in the
aggregated mass is at least about 0.05 microns, more preferably at
least about 0.1 microns.
[0048] Embodiments of the invention have been found to reduce
exaggerated grain growth proximate the bonding surface, and may be
even more advantageous the lower the mean diamond grain size.
[0049] In one embodiment, the method includes forming a carburised
substrate, wherein source of excess carbon is included in or
introduced into the volume of the substrate. In some embodiments
the source of excess carbon is dispersed substantially throughout
the entire volume of the carburised substrate. In other embodiments
the source of excess carbon is dispersed in a surface region
proximate or adjacent the bonding surface.
[0050] Preferably, the mean content of the source of excess carbon
within a surface region of the carburised substrate or throughout
substantially the entire carburised substrate is no greater than
about 10 weight percent, more preferably no greater than about 6
weight percent and yet more preferably no greater than about 5.5
weight percent of the material in the surface region or the
substrate. Preferably, the content of the source of excess carbon
within the surface region or throughout the entire carburised
substrate is at least about 0.1 weight percent and more preferably
at least about 0.3 weight percent of the material in the region. In
some embodiments the surface region extends to a depth of at least
about 1 mm, at least about 2 mm, or even at least 3 mm from the
bonding surface. In some embodiments, the surface region has a
volume of at least 2 times that of the PCD structure or at least 3
times that of the PCD structure. In some embodiments the volume of
the surface region may be at least ten times greater than the
volume of the PCD structure.
[0051] The weight percent is expressed of the total substrate
material within the region in which the carbon is introduced
[0052] In one embodiment the diamond grains in the aggregated mass
have a multi-modal size distribution.
[0053] Preferably, the source of excess carbon is a carbonaceous
material other than metal carbide, such as carbon black powder or
graphite. In one embodiment the source of excess carbon may be
derived from diamond that has been converted into a non-diamond
material. Such materials may consist essentially of carbon and may
not substantially introduce unwanted material into the substrate or
PCD. In some embodiments the source of excess carbon may be in the
form of organic molecules. In some embodiments the source of excess
carbon may be introduced in the form of a gas, such as a gas of
organic molecules such as methane.
[0054] In one embodiment, the method includes combining source of
excess carbon in particulate or granular form with raw materials
for the cemented carbide, forming the combination into a
substantially self-supporting green body, and sintering the green
body at a pressure at which diamond is not thermodynamically stable
to form the carburised substrate. In some embodiments the raw
materials for cemented carbide comprise grains of tungsten carbide
and grains comprising cobalt.
[0055] The method may include combining diamond grains with raw
materials for cemented carbide, forming the combination into a
substantially self-supporting green body; subjecting the green body
to a temperature of at least 500 degrees centigrade and a pressure
at which diamond is not thermodynamically stable to form the
carburised substrate. The diamond particles may be wholly or partly
converted into a non-diamond material, particularly graphite. In
one embodiment, substantially all of the converted diamond
re-converts to diamond during the step of sintering the PCD. This
embodiment has been found to result in PCD fingers extending into
the substrate, which may result in improved bonding of the PCD to
the substrate and reduced incidence of delamination.
[0056] In one embodiment of this aspect to the invention, the
substrate is substantially free of diamond.
[0057] In embodiments where the substrate includes diamond
particles formed from converted graphite, for example where the
source of excess carbon is graphite, the diamond particles may have
little or substantially no plastic deformation within at least a
peripheral volume of each diamond particle. In some embodiments the
diamond particles have substantially no plastic deformation.
[0058] In some embodiments, the source of excess carbon may be
deposited onto a bonding surface of the substrate to form a
carburised substrate or carburised substrate assembly. In some
embodiments the source of excess carbon may be deposited onto the
substrate bonding surface by means of a thermal or other spraying
method. In one embodiment a disc or film comprising a refractory
metal, such as tungsten may be placed over the deposited source of
excess carbon to form a carburised substrate assembly.
[0059] The method may include introducing metal carbide or a
precursor or precursors for metal carbide into the aggregated mass
of diamond grains. More preferably, the method includes introducing
refractory metal carbide particles, for example tungsten carbide,
tantalum carbide, niobium carbide or vanadium carbide, into the
aggregated mass of diamond grains. In some embodiments the method
includes introducing a refractory metal precursor for metal
carbide, for example tungsten, tantalum, niobium or vanadium in
non-carbide compound or in elemental form, into the aggregated mass
of diamond grains. In embodiments of the method where a source of
excess carbon may be introduced to or into the substrate, the
introduction of metal carbide into the aggregated mass of diamond
grains, directly or via the introduction of precursor or
precursors, may significantly enhance the abrasion or erosion
resistance of the sintered PCD structure.
[0060] In some embodiments the metal carbide or a precursor or
precursors for metal carbide may be introduced in particulate form
into the aggregated mass of diamond grains by blending the
particles with the diamond grains.
[0061] In some embodiments the cemented carbide comprises grains of
metal carbide cemented together by a metal binder, the metal binder
comprising a solvent/catalyst material for diamond, such as cobalt.
Such metal binder may infiltrate the aggregated mass of diamond
particles during the sintering step and function as a sintering aid
for diamond.
[0062] Embodiments of the invention have been found to reduce or
eliminate pooling of the metal binder material within the PCD
adjacent the interface with the substrate and the corresponding
depletion of metal binder material within the substrate adjacent
the bonding surface/interface, and may reduce or eliminate certain
defects associated with carbide or diamond grain growth proximate
the bonding surface.
[0063] According to a third aspect of the invention there is
provided a PCD cutter insert for a drill bit, such as a drill bit
for boring into the earth, the PCD cutter insert comprising a PCD
composite compact element according to the invention.
[0064] According to a fourth aspect of the invention there is
provided a drill bit for boring into the earth, the drill bit
comprising a PCD cutter insert according to the invention.
[0065] Boring into the earth as carried out in the oil and gas
drilling industry exerts high forces on a cutter insert and PCD
cutter inserts according to the invention may exhibit reduced
failure rate in use.
DRAWING CAPTIONS
[0066] Non-limiting embodiments will now be described with
reference to the accompanying drawings of which:
[0067] FIG. 1 shows (a) a schematic drawing of a perspective view
of an embodiment of a PCD composite compact element, as well as
longitudinal side cross-sectional views of two embodiments, (b) and
(c).
[0068] FIGS. 2 to 7 are schematic drawings of perspective views of
embodiments of PCD composite compact elements.
[0069] FIG. 8 shows a graph of number of grains versus equivalent
circle diameter grain size for a fine-grained bi-modal size
distribution of diamond grains within an embodiment of PCD
material.
[0070] FIG. 9 shows a graph of number of grains versus equivalent
circle diameter grain size for diamond grains within an embodiment
of PCD material.
[0071] FIG. 10 shows a schematic graph of binder content as well as
the carbon content in the PCD and the substrate as a function of
depth from the PCD working surface in the case of a prior art PCD
composite compact as well as in the case of an embodiment of the
invention.
[0072] FIG. 11 is a graph showing the ratio of cobalt to tungsten
content as a function of distance into the substrate from the
interface with the PCD structure, in the case of an embodiment of
the invention (data shown as filled squares) and a control
according to the prior art (data shown as unfilled diamonds).
[0073] FIG. 12 is a graph showing the ratio of cobalt to carbon
content as a function of distance into the PCD structure from the
interface with the substrate, in the case of an embodiment of the
invention (data shown as filled squares) and a control according to
the prior art (data shown as unfilled diamonds).
[0074] FIG. 13 shows a scanning electron micrograph of a
cross-section of a bonding interface between a PCD structure and a
cobalt-cemented WC substrate enhanced with diamond.
DETAILED DESCRIPTION OF EMBODIMENTS
[0075] With reference to FIG. 1, an embodiment of a polycrystalline
diamond composite compact (PCD) element, 100, comprises a PCD
structure, 110, integrally bonded to a cemented carbide substrate,
120, at an interface, 125. In some embodiments the interface
between the embodiment shown in (a) The PCD structure, 110, has an
axial thickness t.sub.PCD and the substrate, 120, has an axial
thickness t.sub.sub, the axial thickness being measured from an
interface, 125, between the PCD structure, 110, in an axial
direction indicated by the line marked "axial". In an embodiment
shown in (b), the interface, 125, is substantially planar, and in
an embodiment shown in (c), the interface, 125, is non-planar and
the PCD structure, 110, has at least two thicknesses, t.sub.PCD-1
and t.sub.PCD-2.
[0076] With reference to FIG. 2, an embodiment of a polycrystalline
diamond composite compact (PCD) element, 100, comprises a PCD
structure, 110, integrally bonded to a cemented carbide substrate,
120, at an interface, 125, and the PCD structure comprises a first
region, 112, and a second region, 111, the mean size of the diamond
grains of the first region, 112, being greater than that of the
diamond grains in the second region, 111; the first region, 112,
being proximate the substrate, 120, and the second region, 111,
being remote from the substrate, 120.
[0077] With reference to FIG. 3, an embodiment of a polycrystalline
diamond composite compact (PCD) element, 100, comprises a PCD
structure, 110, integrally bonded to a cemented carbide substrate,
120, at an interface, 125, wherein the substrate, 120, includes
diamond particles dispersed within a surface region, 221, extending
from the interface to a depth. The remaining region, 122, of the
substrate, 120, is substantially free of diamond. In some
embodiments the depth is at least 1 millimetre, at least 2
millimetres or at least 3 millimetres. In some embodiments the
surface region, 121, of the substrate has a volume of at least 2
times that of the PCD structure, 110, at least 3 times that of the
PCD structure, 110, or even at least ten times greater than the
volume of the PCD structure, 110.
[0078] With reference to FIG. 4, an embodiment of the method of the
invention includes introducing a source of excess carbon to the
substrate, 220, at or proximate a bonding surface, 225, to form a
carburised substrate assembly, 250; contacting an aggregated mass,
210, of diamond grains with the carburised substrate assembly, 250,
adjacent or proximate the bonding surface, 225, to form an unbonded
assembly, 200; wherein the source of excess carbon is in the form
of graphite dispersed in a surface region, 221, of the substrate,
220, the surface region extending from proximate the bonding
surface, 125, to a depth. In some embodiments the depth is at least
1 millimetre, at least 2 millimetres or at least 3 millimetres.
With reference to FIG. 5, the source of excess carbon is in the
form of graphite dispersed substantially throughout the entire
volume of the substrate, 220.
[0079] With reference to FIG. 6, an embodiment of the method of the
invention includes introducing a source of excess carbon to the
substrate, 220, at or proximate a bonding surface, 225, to form a
carburised substrate assembly, 250; contacting an aggregated mass,
210, of diamond grains with the carburised substrate assembly, 250,
adjacent or proximate the bonding surface, 225, to form an unbonded
assembly, 200; wherein the source of excess carbon, 230, is
deposited onto a bonding surface, 125, of the substrate. With
reference to FIG. 7, an embodiment of the method of the invention
includes placing a disc or film, 240, comprising tungsten over the
deposited source of excess carbon, 230.
[0080] For example, FIG. 8 shows a graph of number of grains versus
equivalent circle diameter grain size for a fine-grained bi-modal
size distribution of diamond grains within an embodiment of PCD
material; and FIG. 9 shows a graph of number of grains versus
equivalent circle diameter grain size for diamond grains within an
embodiment of a multi-modal PCD material.
[0081] The PCD material having the diamond grain size distribution
shown in FIG. 8 is an example of an embodiment of PCD material that
may benefit particularly well from the invention, wherein the mean
size of the diamond grains within the sintered PCD is in the range
from about 1.5 to about 6 microns and the size distribution can be
resolved into at least two distinct peaks. FIG. 8 shows the
distribution of equivalent circle diameters, with no Saltykov
correction having been applied to convert the size distribution
obtained from the two-dimensional image data to a grain size
distribution in three dimensions.
[0082] With reference to FIG. 9, the relative (e.g. weight percent)
content of cobalt, 200, within a prior art PCD composite compact,
210, and a PCD composite compact according to an embodiment of the
invention, 220, are compared in respect of qualitative features. In
some embodiments of the invention binder pooling is substantially
reduced. In some embodiments the incidence of plume defects is
substantially reduced. Also shown in FIG. 9 are the corresponding
relative content of carbon, 400, within a prior art PCD composite
compact, 410, and a PCD composite compact according to an
embodiment of the invention, 420, are compared in respect of
qualitative features. The region of the graphs indicated by 110
corresponds to the PCD structure and the region indicated by 121
corresponds to the carbide substrate.
[0083] FIG. 10 is a graph showing the ratio of cobalt to tungsten
as a function of axial distance into the substrate from the
interface with the PCD structure, in the case of an embodiment of
the invention (data shown as filled squares) and a control
according to the prior art (data shown as unfilled diamonds). The
interface corresponds to zero millimetres. In an embodiment of the
invention, the ratio (shown as filled squares) remains
substantially constant from the interface into the bulk of the
substrate, the standard deviation of the data being less than about
5 percent of the mean value, M. The upper and lower standard
deviations are indicated as SU and SL, respectively. The upper and
lower percent limits or M(1+20%) and M(1-20%), are shown as LU and
LL, respectively. In the case of a control material, made according
to the prior art, the mean ratio of cobalt to tungsten is
substantially lower within a depth of approximately 1.5 millimetres
is substantially and systematically less than the mean value in the
bulk of the substrate, and is less than the lower limit M(1-20%)
within a depth of about 1 millimetre from the interface. This is
called the "depleted zone".
[0084] FIG. 11 is a graph showing the ratio of cobalt to carbon as
a function of axial distance into the PCD structure from the
interface with the substrate, in the case of an embodiment of the
invention (data shown as filled squares) and a control according to
the prior art (data shown as unfilled diamonds). The interface
corresponds to zero millimetres. In an embodiment of the invention,
the ratio (shown as filled squares) remains substantially constant
from the interface into the bulk of the PCD structure, even within
the first 0.2 millimetres from the interface, where the ratio in
the control material increases dramatically to greater than
M(1+20%), corresponding to binder pooling within the PCD structure
adjacent the interface.
[0085] With reference to FIG. 12, an SEM micrograph of the region
straddling an interface between a PCD structure, 40, and a cemented
carbide substrate, 50, of a PCD composite compact according to an
embodiment of the invention is shown. The substrate, 50, contains
particles of diamond, 46. A "finger", 45, comprising contiguous
polycrystalline diamond and having a length in the range of about
30 to 50 microns extends from the PCD structure, 40, into the
substrate, 50.
[0086] As previously noted, embodiments of the invention may
comprise relatively thick PCD caps and substrates without the need
for using higher temperatures in the sintering step. In general,
the thicker the PCD layer, the higher must be the sintering
temperature in order to urge molten solvent/catalyst material from
the substrate to infiltrate the entire PCD layer. A serious
consequence of this not occurring is the presence of "soft spot"
defects wherein the diamond grains remote from the interface have
not adequately sintered. Unfortunately, higher sintering
temperatures result in excessive dissolution of diamond proximate
the interface and may result in plume defects in the form of
exaggerated large acicular metal carbide grains. On the other hand,
higher sintering temperatures tend to promote exaggerated diamond
grain growth, which is also undesirable. This is less of a problem
where the PCD structure is relatively thin, since the minimum
sintering temperature for the avoidance of soft spots is lower the
thinner the PCD structure. However, many applications require that
the PCD structure is several millimetres thick and that the
substrate is tens of millimetres thick. In particular, PCD compacts
used for boring into earth and rock in the oil and gas industry
comprise relatively thick PCD caps and substrates.
[0087] The invention will now be described with reference to the
following non-limiting examples.
Example 1
[0088] A first substrate element for use as the surface region of a
substrate for a PCD compact was manufactured by blending together
diamond particles, tungsten carbide (WC) powder and cobalt powder,
forming the blended mixture into a compacted green body, and
subjecting the green body to a conventional carbide sintering
process. The diamond particles had mean size in the range of 0.75
to 1.5 microns, and constituted 3 weight percent of the blended
mixture. The WC powder and the cobalt powder had been pre-mixed,
the cobalt constituting 13 weight percent of the WC-Co pre-mix and
the WC particles having a mean size in the range from about 1 to 4
microns. About 2 weight percent organic pressing aid was included
in the WC-Co mix. The blended powder mix was uniaxially compacted
at ambient temperature to form a substantially cylindrical green
body, which was conventionally sintered at a temperature of 1,400
degrees centigrade for 2 hours to form a sintered article. By the
end of the sintering process, the diamond particles had completely
converted into graphite. The substrate had a diameter of about 17.4
millimetres and a height of about 6 millimetres after final
machining.
[0089] A second substrate element for use as a region of a
substrate substantially free of diamond was manufactured in the
same way and using the same raw materials as the first substrate
element, except that no diamond was introduced and the height of
the second substrate element was about 7 millimetres.
[0090] The first substrate element was placed on top of the second
substrate element, the first and second substrate elements being
substantially in registration, to form a substrate assembly, having
an upper surface being the exposed end surface of the first
substrate element.
[0091] A layer comprising an unbonded aggregated mass of diamond
grains was deposited onto the upper surface of the substrate
assembly end surface of the sintered article to form an unbonded
assembly. The diamond grains had mean size of about 0.5 microns and
were coated with cobalt, which constituted 5 weight percent of the
aggregated mass. The coated grains were then subjected to heat
treatment in a hydrogen rich atmosphere at 850 degrees centigrade
in order to terminate the surfaces with hydrogen.
[0092] The unbonded assembly was mounted within a capsule for an
ultra-high pressure furnace, as is known in the art. The capsule
was subjected to a pressure of about 5.5 GPa and a temperature of
about 1,400 degrees centigrade for a period of about 5 minutes.
After sintering, the first and second substrate elements had
sintered together and the PCD composite compact was processed in
the usual way to form an insert having a diameter of about 15.9
milimetres and a PCD structure with thickness in the range of about
1.7 to 2.1 millimetres.
[0093] The insert was analysed using scanning electron micrography
(SEM). Particularly noteworthy was the absence of discernable
"pooling" of cobalt binder adjacent the interface between the PCD
and the substrate, which is a typical feature of known inserts,
especially those having relatively thick PCD and substrate, of
which the insert was an example. The sample displayed an abrupt
transition between the cemented carbide of the substrate and the
PCD. In addition, no substantial exaggerated diamond or WC grains
were observed within the PCD layer proximate the interface, as
occur in known inserts.
Example 2
[0094] A substrate a PCD compact was manufactured by blending
together diamond particles, tungsten carbide (WC) powder and cobalt
powder, forming the blended mixture into a compacted green body,
and subjecting the green body to a conventional carbide sintering
process. The diamond particles had mean size of about 22 microns
and constituted about 5.8 weight percent of the blended mixture.
The WC powder and the cobalt powder had been pre-mixed, the cobalt
constituting 13 weight percent of the WC-Co pre-mix and the WC
particles having a mean size in the range from about 1 to 4
microns. About 2 weight percent organic pressing aid was included
in the WC-Co mix. The blended powder mix was uniaxially compacted
at ambient temperature to form a substantially cylindrical green
body, which was conventionally sintered at a temperature of 1,400
degrees centigrade for 2 hours to form a sintered article. By the
end of the sintering process, the diamond particles had completely
converted into graphite. The substrate had a diameter of about 17.4
millimetres and a height of about 13 millimetres after final
machining.
[0095] A layer comprising an unbonded aggregated mass of diamond
grains was deposited onto the upper surface of the substrate of the
sintered article to form an unbonded assembly. Raw material diamond
powder for the aggregated mass was prepared by blending diamond
grains from three sources, each source having a different average
grain size distribution.
[0096] The unbonded assembly was mounted within a capsule for an
ultra-high pressure furnace, as is known in the art. The capsule
was subjected to a pressure of about 5.5 GPa and a temperature of
about 1,400 degrees centigrade for a period of about 5 minutes.
After sintering, the first and second substrate elements had
sintered together and the PCD composite compact element was
processed in the usual way to form an insert having a diameter of
about 15.9 milimetres and a PCD structure with thickness in the
range of about 1.7 to 2.1 millimetres.
[0097] The insert was analysed using scanning electron micrography
(SEM). The Analysis of the material was carried out at several
points on a polished cross-section longitudinally through the
interface between the PCD structure and the substrate. The contents
of tungsten (W) and cobalt (Co) were measured within the substrate
at several different points from proximate the interface into the
bulk of the substrate, and the contents of carbon (C) and cobalt
(Co) were measured within the PCD structure at several different
points from proximate the interface into the bulk of the PCD
structure. The results of these measurements are shown as ratios as
functions of distance from the interface in FIGS. 11 and 12,
respectively. Particularly noteworthy was the absence of
substantial "pooling" of cobalt binder adjacent the interface
between the PCD and the substrate, which is a typical feature of
known inserts, especially those having relatively thick PCD and
substrate. The sample displayed an abrupt compositional transition
between the cemented carbide of the substrate and the PCD. In
addition, substantially no exaggerated diamond or WC grains were
observed within the PCD layer proximate the interface, as occur in
known inserts.
Example 3
[0098] A substrate a PCD compact was manufactured as in example 2,
except that the diamond particles had mean size of about 2 microns
and constituted about 2.7 weight percent of the blended mixture. A
layer comprising an unbonded aggregated mass of diamond grains as
described in example 2 was deposited onto the upper surface of the
substrate of the sintered article to form an unbonded assembly,
which was sintered as in example 2 to form a PCD composite compact
element.
[0099] As in example 2, the absence of substantial "pooling" of
cobalt binder adjacent the interface between the PCD and the
substrate was observed, and substantially no exaggerated diamond or
WC grains were observed within the PCD layer proximate the
interface.
Example 4
[0100] A substrate for a PCD compact was manufactured in the same
way and using the same raw materials as the first substrate element
of example 1, except that the height of the substrate was 13
millimetres. In other words, the whole substrate had substantially
the same composition, shape and diameter as the first substrate
element described in example 1.
[0101] A layer of unbonded aggregated mass of diamond grains was
deposited onto an end surface of the substrate to form an unbonded
assembly. The diamond grains had an ultra-fine bi-modal
distribution, having a mean size in the range from about 0.1 to 1
micrometre and were coated with cobalt, which constituted 5 weight
percent of the aggregated mass. The coated grains were then
subjected to heat treatment in a hydrogen rich atmosphere at 850
degrees centigrade in order to terminate the surfaces with
hydrogen.
[0102] The unbonded assembly was mounted within a capsule for an
ultra-high pressure furnace, as is known in the art. The capsule
was subjected to a pressure of about 5.5 GPa and a temperature of
about 1,400 degrees centigrade for a period of about 5 minutes.
After sintering, the PCD composite compact was processed in the
usual way to form an insert having a diameter of about 15.9
milimetres and a PCD structure with thickness in the range of about
1.7 to 2.1 millimetres.
[0103] The insert was analysed using scanning electron micrography
(SEM). Particularly noteworthy was the absence of discernable
pooling of cobalt binder adjacent the interface between the PCD and
the substrate. The sample displayed an abrupt transition between
the cemented carbide of the substrate and the PCD. In addition, no
substantial exaggerated diamond or WC grains were observed within
the PCD layer proximate the interface, as occur in known
inserts.
Example 5
[0104] A substrate for a PCD compact was manufactured in the same
way and using the same raw materials as the first substrate element
of example 1, except that the height of the substrate was 13
millimetres. In other words, the whole substrate had substantially
the same composition, shape and diameter as the first substrate
element described in example 1.
[0105] A first diamond layer formed of an unbonded aggregated mass
of diamond grains was deposited onto an end surface of the
substrate, and a second diamond layer formed of an unbonded
aggregated mass of diamond grains was deposited onto the first
layer to form an unbonded assembly. The first diamond layer had a
mean thickness of about 0.5 millimetres and the second diamond
layer had a mean thickness of about 2.5 millimetres, the first
diamond layer being sandwiched between the substrate and the second
diamond layer. The diamond grains of the first diamond layer had a
fine-grain bi-modal distribution and the diamond grains of the
second diamond layer had an ultra-fine-grain distribution. The
diamond grains of the second diamond layer had been coated with
cobalt, which constituted 5 weight percent of the aggregated mass,
and had then been subjected to heat treatment in a hydrogen rich
atmosphere at 850 degrees centigrade in order to terminate the
surfaces with hydrogen.
[0106] The unbonded assembly was mounted within a capsule for an
ultra-high pressure furnace, as is known in the art. The capsule
was subjected to a pressure of about 5.5 GPa and a temperature of
about 1,400 degrees centigrade for a period of about 5 minutes.
After sintering, the PCD composite compact was processed in the
usual way to form an insert having a diameter of about 15.9
milimetres and a PCD structure with thickness in the range of about
2.2 millimetres.
[0107] The insert was analysed using scanning electron micrography
(SEM). Particularly noteworthy was the absence of discernable
pooling of cobalt binder adjacent the interface between the PCD and
the substrate. The sample displayed an abrupt transition between
the cemented carbide of the substrate and the PCD. In addition, no
substantial exaggerated diamond or WC grains were observed within
the PCD layer proximate the interface, as occur in known
inserts.
Example 6
[0108] As example 2, except that the capsule was subjected to a
pressure of about 6.8 GPa and a temperature of about 1,500 degrees
centigrade for a period of about 5 minutes.
[0109] Although the foregoing description of consolidated superhard
materials, production methods, and various applications of them
contain many specifics, these should not be construed as limiting
the scope of the present invention, but merely as providing
illustrations of some exemplary embodiments. Similarly, other
embodiments of the invention may be devised which do not depart
from the spirit or scope of the present invention. The scope of the
invention is, therefore, indicated and limited only by the appended
claims and their legal equivalents, rather than by the foregoing
description. All additions, deletions, and modifications to the
invention, as disclosed herein, which fall within the meaning and
scope of the claims are to be embraced.
* * * * *