U.S. patent application number 14/229203 was filed with the patent office on 2015-10-01 for reinforced thermally stable polycrystalline diamond cutter.
This patent application is currently assigned to DIAMOND INNOVATIONS, INC.. The applicant listed for this patent is DIAMOND INNOVATIONS, INC.. Invention is credited to Frank Gao, Suresh Shankarappa Vagarali, Kai Zhang.
Application Number | 20150273662 14/229203 |
Document ID | / |
Family ID | 54189048 |
Filed Date | 2015-10-01 |
United States Patent
Application |
20150273662 |
Kind Code |
A1 |
Zhang; Kai ; et al. |
October 1, 2015 |
REINFORCED THERMALLY STABLE POLYCRYSTALLINE DIAMOND CUTTER
Abstract
A superabrasive compact and a method of making the superabrasive
compact are disclosed. A superabrasive compact may comprise a
diamond table and a substrate. The diamond table may be attached to
the substrate. The diamond table may include bonded diamond grains
defining interstitial channels. The interstitial channels may be
filled with at least two types of carbides in the first region. The
interstitial channels in the second region may be filled with a
metal catalyst from the substrate.
Inventors: |
Zhang; Kai; (Westerville,
OH) ; Vagarali; Suresh Shankarappa; (Columbus,
OH) ; Gao; Frank; (Columbus, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DIAMOND INNOVATIONS, INC. |
Worthington |
OH |
US |
|
|
Assignee: |
DIAMOND INNOVATIONS, INC.
Worthington
OH
|
Family ID: |
54189048 |
Appl. No.: |
14/229203 |
Filed: |
March 28, 2014 |
Current U.S.
Class: |
51/309 |
Current CPC
Class: |
B24D 18/0009 20130101;
B24D 3/06 20130101 |
International
Class: |
B24D 3/06 20060101
B24D003/06; B24D 18/00 20060101 B24D018/00 |
Claims
1. A superabrasive compact, comprising: a substrate; a diamond
table attached to the substrate, wherein the diamond table has a
first region and a second region, the second region is sandwiched
between the first region and the substrate, wherein the diamond
table includes bonded diamond grains defining interstitial
channels, the interstitial channels are filled with at least two
types of carbides in the first region, the interstitial channels in
the second region are filled with a metal catalyst from the
substrate.
2. The superabrasive compact of the claim 1, wherein a first
carbide in the first region comprises silicon carbide.
3. The superabrasive compact of the claim 1, wherein a second
carbide in the first region comprises aluminum carbide.
4. The superabrasive compact of the claim 1, wherein the first
region comprises an additive.
5. The superabrasive compact of the claim 4, wherein the additive
comprises an inert chemical.
6. The superabrasive compact of the claim 5, wherein the inert
chemical comprises glass or quartz.
7. A method of making a superabrasive compact, comprising:
providing at least a partially leached polycrystalline diamond
table that comprises bonded diamond grains defining interstitial
channels therein; providing a composite material positioned near a
surface of the at least partially leached polycrystalline diamond
table; providing a substrate near the at least partially leached
polycrystalline diamond table such that the at least partially
leached polycrystalline diamond table is sandwiched between the
composite material and the substrate; and subjecting the substrate
and the at least partially leached polycrystalline diamond table
and the composite material to conditions of elevated temperature
and pressure suitable for producing the polycrystalline
superabrasive compact; wherein the composite material infiltrates
into a first region of the at least partially leached
polycrystalline diamond table and forms at least two carbides at a
first temperature, wherein a catalyst from the substrate sweeps
into a second region of the at least partially leached
polycrystalline diamond table at a second temperature.
8. The method of the claim 7, wherein the substrate is cemented
tungsten carbide.
9. The method of the claim 7, wherein the composite material is a
eutectic material.
10. The method of the claim 7, wherein the first carbide is silicon
carbide.
11. The method of the claim 7, wherein the second carbide is
aluminum carbide.
12. The method of the claim 9, wherein the eutectic material
comprises about 87.5% aluminum and about 12.5% silicon eutectic
composition.
13. The method of the claim 7, wherein the first region occupies
from about 20% to up to about 95% volume of the at least partially
leached polycrystalline diamond table.
14. The method of the claim 7, wherein the composite material is
selected from a group consisting of as a powder, as a disk, as a
ring, as a disk with perforated holes, as a triangle, as a
rectangular.
15. The method of claim 7, further comprising bonding the substrate
to the second region of the at least partially leached
polycrystalline diamond table.
16. The method of claim 7, wherein the catalyst from the substrate
is cobalt.
17. A superabrasive compact, comprising: a substrate; a diamond
table attached to the substrate, wherein the diamond table has a
first region and a second region, the second region is sandwiched
between the first region and the substrate, wherein the diamond
table includes bonded diamond grains defining interstitial
channels, the interstitial channels are filled at least with
aluminum carbide and additives in the first region, the
interstitial channels in the second region are filled with a metal
catalyst from the substrate, wherein the first region occupies from
about 20% to up to about 95% volume of the diamond table.
18. The superabrasive compact of the claim 17, wherein the diamond
table further comprises silicon carbide.
19. The superabrasive compact of the claim 17, wherein the additive
comprises quartz or glass.
20. The superabrasive compact of the claim 17, wherein the first
region of the diamond table has about 87.5% aluminum and about
12.5% silicon.
21. The superabrasive compact of the claim 17, wherein the
substrate is cemented tungsten carbide.
22. The superabrasive compact of the claim 17, wherein the metal
catalyst is an iron group transitional metal.
23. The superabrasive compact of the claim 22, wherein the iron
group transitional metal is cobalt.
Description
TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY
[0001] The present invention relates generally to superabrasive
materials and a method of making superabrasive materials, and more
particularly, to polycrystalline diamond compacts (PDC).
SUMMARY
[0002] In one embodiment, a superabrasive compact may comprise a
substrate; a diamond table attached to the substrate, wherein the
diamond table has a first region and a second region, the second
region is sandwiched between the first region and the substrate,
wherein the diamond table includes bonded diamond grains defining
interstitial channels, the interstitial channels are filled with at
least two types of carbides in the first region, the interstitial
channels in the second region are filled with a metal catalyst from
the substrate.
[0003] In another embodiment, a method of making a superabrasive
compact may comprise steps of providing an at least partially
leached polycrystalline diamond table that comprises bonded diamond
grains defining interstitial channels therein; providing a
composite material positioned near a surface of the at least
partially leached polycrystalline diamond table; providing a
substrate near the at least partially leached polycrystalline
diamond table such that the at least partially leached
polycrystalline diamond table is sandwiched between the composite
material and the substrate; and subjecting the substrate and the at
least partially leached polycrystalline diamond table and the
composite material to conditions of elevated temperature and
pressure suitable for producing the polycrystalline superabrasive
compact; wherein the composite material infiltrates into a first
region of the at least partially leached polycrystalline diamond
table and forms at least two carbides at a first temperature,
wherein a catalyst from the substrate sweeps into a second region
of the at least partially leached polycrystalline diamond table at
a second temperature.
[0004] In yet another embodiment, a superabrasive compact may
comprise a substrate; a diamond table attached to the substrate,
wherein the diamond table has a first region and a second region,
the second region is sandwiched between the first region and the
substrate, wherein the diamond table includes bonded diamond grains
defining interstitial channels, the interstitial channels are
filled with aluminum carbide and additives in the first region, the
interstitial channels in the second region are filled with a metal
catalyst from the substrate, wherein the first region occupies from
about 20% up to about 95% volume of the at least partially leached
polycrystalline diamond table.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] 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.
[0006] FIG. 1 is schematic perspective view of a cylindrical shape
thermally stable polycrystalline diamond compact produced in a high
pressure high temperature (HPHT) process according to an
embodiment;
[0007] FIG. 2 is an enlarged cross-sectional view of a part of
diamond table on the thermally stable polycrystalline diamond
compact as shown in FIG. 1 according to an embodiment; and
[0008] FIG. 3 is a flow chart illustrating a method of making
reinforced thermally stable polycrystalline diamond compact.
DETAILED DESCRIPTION
[0009] Before the description of the embodiment, terminology,
methodology, systems, and materials are described; it is to be
understood that this disclosure is not limited to the particular
terminologies, 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 of embodiments only, and is not intended to
limit the scope of embodiments. For example, as used herein, the
singular forms "a," "an," and "the" include plural references
unless the context clearly dictates otherwise. In 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.
[0010] 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 invention. 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.
[0011] As used herein, the term "about" means plus or minus 10% of
the numerical value of the number with which it is being used.
Therefore, about 50% means in the range of 45%-55%.
[0012] As used herein, the term "superabrasive particles" may refer
to ultra-hard particles or superabrasive particles having a Knoop
hardness of 3500 KHN or greater. The superabrasive particles may
include diamond and cubic boron nitride, for example. The term
"abrasive", as used herein, refers to any material used to wear
away softer materials.
[0013] The term "particle" or "particles", as used herein, refers
to a discrete body or bodies. A particle is also considered a
crystal or a grain.
[0014] The term "superabrasive compact", as used herein, refers to
a sintered product made using super abrasive particles, such as
diamond feed or cubic boron nitride particles. The compact may
include a support, such as a tungsten carbide support, or may not
include a support. The "superabrasive compact" is a broad term,
which may include cutting element, cutters, or polycrystalline
cubic boron nitride insert.
[0015] The term "cutting element", as used herein, means and
includes any element of an earth-boring tool that is used to cut or
otherwise disintegrate formation material when the earth-boring
tool is used to form or enlarge a bore in the formation.
[0016] The term "earth-boring tool", as used herein, means and
includes any tool used to remove formation material and form a bore
(e.g., a wellbore) through the formation by way of removing the
formation material. Earth-boring tools include, for example, rotary
drill bits (e.g., fixed-compact or "drag" bits and roller cone or
"rock" bits), hybrid bits including both fixed compacts and roller
elements, coring bits, percussion bits, bi-center bits, reamers
(including expandable reamers and fixed-wing reamers), and other
so-called "hole-opening" tools.
[0017] The term "feed" or "diamond feed", as used herein, refers to
any type of diamond particles, or diamond powder, used as a
starting material in further synthesis of PDC compacts.
[0018] The term "polycrystalline diamond", as used herein, refers
to a plurality of randomly oriented or highly oriented
monocrystalline diamond particles, which may represent a body or a
particle consisting of a large number of smaller monocrystalline
diamond particles of any sizes. Polycrystalline diamond particles
usually do not have cleavage planes.
[0019] The term "superabrasive", as used herein, refers to an
abrasive possessing superior hardness and abrasion resistance.
Diamond and cubic boron nitride are examples of superabrasives and
have Knoop indentation hardness values of over 3500.
[0020] The terms "diamond particle" or "particles" or "diamond
powder", which is a plurality of a large number of single crystal
or polycrystalline diamond particles, are used synonymously in the
instant application and have the same meaning as "particle" defined
above.
[0021] Polycrystalline diamond compact (or "PDC", as used
hereinafter) may represent a volume of crystalline diamond grains
with embedded foreign material filling the inter-grain space. In
one particular case, a compact comprises crystalline diamond
grains, bound to each other by strong diamond-to-diamond bonds and
forming a rigid polycrystalline diamond body, and the inter-grain
regions, disposed between the bounded grains and filled in one part
with a catalyst material (e.g. cobalt or its alloys), which was
used to promote diamond bonding during fabrication, and in other
part filled with other materials which may remain after the
sintering of diamond compact. Suitable metal solvent catalysts may
include the iron group transitional metal in Group VIII of the
Periodic table.
[0022] "Thermally stable polycrystalline diamond" as used herein is
understood to refer to intercrystalline bonded diamond that
includes a volume or region that is or that has been rendered
substantially free of the solvent metal catalyst used to form PDC,
or the solvent metal catalyst used to form PDC remains in the
region of the diamond body but is otherwise reacted or otherwise
rendered ineffective in its ability adversely impact the bonded
diamond at elevated temperatures as discussed above.
[0023] In another particular case, a polycrystalline diamond
composite compact comprises a plurality of crystalline diamond
grains, which are not bound to each other, but instead are bound
together by foreign bonding materials such as borides, nitrides,
carbides, and others, e.g. by silicon carbide bonded diamond
material.
[0024] Polycrystalline diamond compacts (or PDC compacts) may be
fabricated in different ways and the examples discussed herein do
not limit a variety of different types of diamond composites and
PDC compacts which may be produced according to an embodiment. In
one particular example, polycrystalline compacts may be formed by
placing a mixture of diamond powder with a suitable solvent
catalyst material (e.g. cobalt powder) on the top of WC--Co
substrate, the assembly is then subjected to conditions of HPHT
process, where the solvent catalyst promotes desired
inter-crystalline diamond-to-diamond bonding resulted in the
formation of a rigid polycrystalline diamond body and, also,
provides a binding between polycrystalline diamond body and WC--Co
substrate.
[0025] In another particular example, a polycrystalline diamond
compact is formed by placing diamond powder without a catalyst
material on the top of substrate containing a catalyst material
(e.g. WC--Co substrate). In this example, necessary cobalt catalyst
material is supplied from the substrate and melted cobalt is swept
through the diamond powder during the HPHT process. In still
another example, a hard polycrystalline diamond composite compact
is fabricated by forming a mixture of diamond powder with silicon
powder and the mixture is subjected to HPHT process, thus forming a
dense polycrystalline compact where diamond particles are bound
together by newly formed silicon carbide material.
[0026] The presence of catalyst materials inside the
polycrystalline diamond body promotes the degradation of the
cutting edge of the compact during the cutting process, especially
if the edge temperature reaches a high enough critical value. It is
theorized that the cobalt driven degradation may be caused by the
large difference in coefficient of thermal expansion between
diamond and catalyst (e.g. cobalt metal), and also by the catalytic
effect of cobalt on diamond graphitization. Removal of catalyst
from the polycrystalline diamond body of PDC compact, for example,
by chemical leaching in acids, leaves an interconnected network of
pores and a residual catalyst (up to about 10 vol %) trapped inside
the polycrystalline diamond body. It has been demonstrated that
depletion of cobalt from the polycrystalline diamond body of the
PDC compact significantly improves a compact's abrasion resistance.
Thus, it is theorized that a thicker cobalt depleted layer near the
cutting edge, such as more than about 100 .mu.m may provide better
abrasion resistance of the PDC compact than a thinner cobalt
depleted layer, such as less than about 100 .mu.m.
[0027] A superabrasive compact 10 in accordance with an embodiment
is shown in FIG. 1. Superabrasive compact 10 may be inserted into a
downhole of a suitable tool, such as a drill bit, for example. One
example of the superabrasive compact 10 may include a diamond table
12 having a top surface 21.
[0028] In one embodiment, the superabrasive compact 10 may be a
standalone compact without a substrate. In another embodiment, the
superabrasive compact 10 may include a substrate 20 attached to the
diamond table 12 formed by polycrystalline diamond particles. The
substrate 20 may be metal carbide, attached to the diamond table 12
via an interface 22 separating the diamond table 12 and the
substrate 20. The interface 22 may have an uneven interface.
Substrate 20 may be made from cemented cobalt tungsten carbide,
while the diamond table 12 may be formed from a polycrystalline
ultra-hard material, such as polycrystalline diamond or diamond
crystals bonded by a foreign material.
[0029] Still in FIG. 1, the diamond table 12 may include at least
two layers with a first layer 26 and a second layer 24. The second
layer 24 may be closer to the interface 22 and may be sandwiched
between the substrate 20 and the first layer 26. The catalyst may
include an iron group transitional metal, such as cobalt, nickel,
or iron, for example.
[0030] The compact 10 may be referred to as a polycrystalline
diamond compact ("PDC") when polycrystalline diamond is used to
form the diamond table 12. PDC compacts are known for their
toughness and durability, which allow them to be an effective
cutter in demanding applications. Although one type of
superabrasive compact 10 has been described, other types of
superabrasive compacts 10 may be utilized. For example, in one
embodiment, superabrasive compact 10 may have a chamfer (not shown)
around an outer peripheral of the top surface 21. The chamfer may
have a vertical height of about 0.5 mm or 1 mm and an angle of
about 45.degree. degrees, for example, which may provide a
particularly strong and fracture resistant tool component. The
superabrasive compact 10 may be a subject of procedure depleting
catalyst metal (e.g. cobalt) near the cutting surface of the
compact, for example, by chemical leaching of cobalt in acidic
solutions. The unleached superabrasive compact may be fabricated
according to processes known to persons having ordinary skill in
the art. Methods for making diamond compacts and composite compacts
are more fully described in U.S. Pat. Nos. 3,141,746; 3,745,623;
3,609,818; 3,850,591; 4,394,170; 4,403,015; 4,794,326; and
4,954,139.
[0031] In certain applications, it may be desired to have a PDC
body comprising a single PDC-containing volume or region, while in
other applications, it may be desired that a PDC body be
constructed having two or more different PDC-containing volume or
regions. For example, it may be desired that the PDC body include a
first PDC-containing region extending a distance D from the top
surface or a working surface, as shown in FIG. 1, and a second
PDC-containing region extending from the first PDC-containing
region to the substrate. The PDC-containing regions may be formed
having different diamond densities and/or be formed from different
diamond grain sizes, and/or be formed from leaching the PDC with
acid solutions partially or fully. It is, therefore, understood
that thermally stable polycrystalline diamond constructions of the
invention may include one or multiple PDC regions within the PDC
body as called for by a particular drilling or cutting
application.
[0032] FIG. 2 illustrates the microstructure of the diamond table
12, and more specifically, a section of the thermally stable
polycrystalline diamond 10. The diamond table 12 of the thermally
stable region may have the first region 26 and the second region
24. The diamond table 12 may include bonded diamond grains 28
defining interstitial channels 42. A matrix of interstitial
channels 42 between the bonded diamond grains may be filled with at
least two types of carbides 48 with a first carbide comprising
silicon carbide, a second carbide comprising aluminum carbide, for
example, in the first region 26. Aluminum carbide may have high
solubility in water and may be decomposed when aluminum carbide
comes into contact with water or drilling mud. The first thermally
stable region comprising the interstitial regions free of the
catalyst material is shown to extend a distance "D" from a working
or cutting surface 21 of the thermally stable polycrystalline
diamond 10. In one embodiment, the distance "D" is identified and
measured by cross sectioning a thermally stable diamond table
construction and using a sufficient level of magnification to
identify the interface between the first and second regions.
[0033] The so-formed thermally stable first region 26 may not be
subject to the thermal degradation encountered in the remaining
areas of the PDC diamond body, resulting in improved thermal
characteristics. The remaining region of the interstitial channels
42 in the second region 24 may be filled with a metal catalyst 46.
The first region may comprise an additive, such as an inert
chemical. The inert chemical may include glass or quartz. Glass
filler may be chosen because glass has a low softening and melting
point such that it may become liquid at relative low temperature,
e.g., 600.degree. C. Quartz crystal may be chosen because quartz
has the similar coefficient of thermal expansion (CTE) as diamond.
The adding of quartz crystal may not cause thermal failure to the
diamond table under high temperatures. The first region may occupy
about 20% to up to about 95% volume of the diamond table 12. In one
embodiment, the diamond table may be a cylindrical shape, therefore
the height D of the first region may be from about 20% to up to
about 95% the total height of the diamond table 12. If the diamond
table is about 2 mm thick, for example, the first region may be
from about 0.4 mm to up to about 1.9 mm, for example.
[0034] In one embodiment, the first region 26 of the diamond table
12 may have about 87.5% aluminum and about 12.5% silicon. The
aluminum carbide and silicon carbide may be formed from a eutectic
material comprising about 87.5% aluminum and about 12.5% silicon
eutectic composition.
[0035] The diamond table 12 may be partially leached according to
known methods. The selected region of the PDC body may be rendered
thermally stable by removing substantially all of the catalyst
material therefrom by exposing the desired surface or surfaces to
acid leaching, as disclosed for example in U.S. Pat. No. 4,224,380,
which is incorporated herein by reference. Generally, after the PDC
body or compact is made by HPHT process, the identified surface or
surfaces, e.g., at least a portion of the working or cutting
surfaces, are placed into contact with the acid leaching agent for
a sufficient period of time to produce the desired leaching or
catalyst material depletion depth.
[0036] Suitable leaching agents for treating the selected region to
be rendered thermally stable include materials selected from the
group consisting of inorganic acids, organic acids, mixtures and
derivatives thereof. The particular leaching agent that is selected
can depend on such factors as the type of catalyst material used,
and the type of other non-diamond metallic materials that may be
present in the PDC body, e.g., when the PDC body is formed using
synthetic diamond powder. While removal of the catalyst material
from the selected region operates to improve the thermal stability
of the selected region, it is known that PDC bodies especially
formed from synthetic diamond powder can include, in addition to
the catalyst material, non-catalyst materials, such as other
metallic elements that can also contribute to thermal
instability.
[0037] As shown in FIG. 3, a method 30 of making a superabrasive
compact may comprise steps of providing at least partially leached
polycrystalline diamond table that comprises bonded diamond grains
defining interstitial channels therein in a step 32; providing a
composite material, such as a eutectic material, positioned near a
surface of the at least partially leached polycrystalline diamond
table in a step 34; providing a substrate, such as cemented
tungsten carbide, near the at least partially leached
polycrystalline diamond table such that the at least partially
leached polycrystalline diamond table is sandwiched between the
composite material and the substrate in a step 36; and subjecting
the substrate and the at least partially leached polycrystalline
diamond table and the composite material to conditions of elevated
temperature and pressure suitable for producing the polycrystalline
superabrasive compact in a step 38, wherein the composite material
infiltrates into a first region of the at least partially leached
polycrystalline diamond table and forms at least two carbides at a
first temperature, wherein a catalyst from the substrate sweeps
into a second region of the at least partially leached
polycrystalline diamond table at a second temperature.
[0038] The method 30 may further include a step of bonding the
substrate to the second region of the at least partially leached
polycrystalline diamond table. Providing at least partially leached
polycrystalline diamond table that comprises bonded diamond grains
defining interstitial channels therein in a step 32 may further
include partially leaching the diamond table or fully leaching the
diamond table after synthesizing the polycrystalline diamond
compact. In one embodiment, the eutectic material may comprise
about 87.5% aluminum and about 12.5% silicon eutectic composition.
During a first temperature about 1000.degree. C., aluminum silicon
eutectic may infiltrate into the interstitial channels of the
diamond table from the top of the diamond table and move toward the
cemented tungsten carbide substrate. By the time when the
temperature reaches about 1500.degree. C., the catalyst, such as an
iron group transitional metal, e.g., cobalt, from the cemented
carbide substrate may sweep into the interstitial channels of the
diamonds. The aluminum silicon eutectic may react with diamond to
form aluminum carbide and silicon carbide at about first
temperature. The aluminum silicon eutectic may keep moving toward
cemented tungsten carbide up to the interface between the first
region and the second region where cobalt sweeps through from
commented tungsten carbide. The first region may occupy from about
20% to up to about 95% volume of the at least partially leached
polycrystalline diamond table.
[0039] The composite material may be selected from a group
consisting of as a powder, as a disk, as a ring, as a disk with
perforated holes, as a triangle, as a rectangular. One or more
steps may be inserted in between or substituted for each of the
foregoing steps 32-38 without departing from the scope of this
disclosure.
Example 1
[0040] PDC cutters were produced by the methods described in the
prior art, composed of a starting diamond powder with an average
grain size of 12 microns in diameter, or with an average grain size
of 24 microns in diameter and a metal carbide, such as tungsten
carbide, attached to the polycrystalline diamond via an interface
between the polycrystalline diamond and tungsten carbide. The
cutter was ground and finished to 16 mm in diameter, and 13 mm in
height. A 45 degree bevel was placed on the edge of the diamond,
with a thickness of about 0.4 mm. Some cutters were fully leached
by removing the catalyst from the diamond table.
[0041] The Ta cup was loaded by pushing a WC substrate (OD 0.648'')
inside and the cup was laid upward. Subsequently, a fully leached
porous diamond table (0.648'') was loaded on top of the WC
substrate. A piece of thin Al--Si eutectic disc (0.002'' thick)
with a dimension of 0.650'' was disposed on top of the diamond
table evenly. Then, a Ta disc (0.005'' thick and 0.650'' OD) was
used to cover Al--Si eutectic disc followed by a mica disc and a
graphite pill (0.1'' thick). Half of the graphite pill protruded
out of the Ta cup. The assembled Ta cup with a graphite sleeve and
some graphite pills were encapsulated. The Ta cup was fit inside
the graphite sleeve tightly. The encapsulated cup was transferred
into cell loading area, and the entire body was loaded into the
cell specifically designed for belt pressing. The cell was loaded
inside the die and was applied high pressure and high temperature
(HPHT) cycle to the cell for 30 minutes. The soak pressure was
maintained around 6.0 GPa and the soak temperature was about
1550.degree. C. The soak time for bonding of the thermally stable
disc to the carbide was about 15 minutes. After the bonding cycle,
the cup was taken out of the pressed cell for further
finishing.
[0042] While reference has been made to specific embodiments, it is
apparent that other embodiments and variations can be devised by
others skilled in the art without departing from their spirit and
scope. The appended claims are intended to be construed to include
all such embodiments and equivalent variations.
* * * * *