U.S. patent application number 14/255740 was filed with the patent office on 2014-08-14 for alloys with low coefficient of thermal expansion as pdc catalysts and binders.
This patent application is currently assigned to VAREL INTERNATIONAL IND., L.P.. The applicant listed for this patent is William W. King, Gary M. Thigpen. Invention is credited to William W. King, Gary M. Thigpen.
Application Number | 20140223835 14/255740 |
Document ID | / |
Family ID | 45466037 |
Filed Date | 2014-08-14 |
United States Patent
Application |
20140223835 |
Kind Code |
A1 |
Thigpen; Gary M. ; et
al. |
August 14, 2014 |
ALLOYS WITH LOW COEFFICIENT OF THERMAL EXPANSION AS PDC CATALYSTS
AND BINDERS
Abstract
A cutting table includes a lattice structure and a catalyst
material deposited within voids formed within the lattice
structure. The catalyst material is deposited in the voids during a
sintering process that forms the lattice structure. The catalyst
material facilitates the growth of the lattice structure. The
catalyst material has a coefficient of thermal expansion that is
less than that of cobalt.
Inventors: |
Thigpen; Gary M.; (Houston,
TX) ; King; William W.; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Thigpen; Gary M.
King; William W. |
Houston
Houston |
TX
TX |
US
US |
|
|
Assignee: |
VAREL INTERNATIONAL IND.,
L.P.
Carrollton
TX
|
Family ID: |
45466037 |
Appl. No.: |
14/255740 |
Filed: |
April 17, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13180414 |
Jul 11, 2011 |
|
|
|
14255740 |
|
|
|
|
61364122 |
Jul 14, 2010 |
|
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Current U.S.
Class: |
51/309 ;
51/307 |
Current CPC
Class: |
C22C 26/00 20130101;
B22F 2005/001 20130101; B24D 3/10 20130101; B24D 99/005 20130101;
C22C 2204/00 20130101; E21B 10/5735 20130101 |
Class at
Publication: |
51/309 ;
51/307 |
International
Class: |
B24D 3/10 20060101
B24D003/10 |
Claims
1. A cutting table, comprising: a lattice structure forming
interstitial spaces therein; and a catalyst material deposited
within the interstitial spaces during a sintering process that
forms the lattice structure, the catalyst material facilitating the
growth of the lattice structure, the catalyst material having a
coefficient of thermal expansion that is less than the coefficient
of thermal expansion of cobalt.
2. The cutting table of claim 1, wherein the catalyst material is
selected from a group consisting of chromium, tantalum, and
ruthenium.
3. The cutting table of claim 1, wherein the catalyst material is
selected from a group consisting of alloys of cobalt, alloys of a
Group VIII metal and at least one non-catalyst metal, and alloys of
two or more Group VIII metals.
4. The cutting table of claim 1, wherein the catalyst material
comprises a eutectic alloy, the eutectic alloy comprising a
eutectic composition.
5. The cutting table of claim 1, wherein the catalyst material
comprises a near eutectic alloy.
6. The cutting table of claim 1, wherein the catalyst material has
a thermal conductivity that is greater than the thermal
conductivity of cobalt.
7. The cutting table of claim 1, wherein the lattice structure
comprises a polycrystalline diamond.
8. A cutter, comprising: a substrate comprising a top surface; a
cutting table, comprising: a cutting surface; an opposing surface
coupled to the top surface; a cutting table outer wall extending
from the circumference of the opposing surface to the circumference
of the cutting surface; a lattice structure forming interstitial
spaces therein; and a catalyst material deposited within the
interstitial spaces during a sintering process that forms the
lattice structure, the catalyst material facilitating the growth of
the lattice structure, the catalyst material having a coefficient
of thermal expansion that is less than the coefficient of thermal
expansion of cobalt.
9. The cutter of claim 8, wherein the catalyst material is selected
from a group consisting of chromium, tantalum, and ruthenium.
10. The cutter of claim 8, wherein the catalyst material is
selected from a group consisting of alloys of cobalt, alloys of a
Group VIII metal and at least one non-catalyst metal, and alloys of
two or more Group VIII metals.
11. The cutter of claim 8, wherein the catalyst material comprises
a eutectic alloy, the eutectic alloy comprising a eutectic
composition.
12. The cutter of claim 8, wherein the catalyst material comprises
a near eutectic alloy.
13. The cutter of claim 8, wherein the catalyst material has a
thermal conductivity that is greater than the thermal conductivity
of cobalt.
14. The cutter of claim 8, wherein the lattice structure comprises
a polycrystalline diamond.
15. The cutter of claim 8, wherein the substrate is formed from a
substrate powder and a binder material, the binder material
cementing the substrate powder to form the substrate, the binder
material being the same as the catalyst material.
16. The cutter of claim 15, wherein the catalyst material
originates in the substrate and infiltrates into the cutting
table.
17. The cutter of claim 8, wherein the substrate is formed from a
substrate powder and a binder material, the binder material
cementing the substrate powder to form the substrate, the binder
material being different than the catalyst material.
18. The cutter of claim 17, wherein the melting point of the
catalyst material is lower than the melting point of the binder
material.
Description
RELATED APPLICATIONS
[0001] The present application is a divisional application of and
claims priority to U.S. patent application Ser. No. 13/180,414,
filed on Jul. 11, 2011, and titled "Alloys With Low Coefficient Of
Thermal Expansion As PDC Catalysts And Binders," which claims
priority to U.S. Provisional Patent Application No. 61/364,122,
titled "Alloys With Low Coefficient Of Thermal Expansion As PDC
Catalysts And Binders" and filed on Jul. 14, 2010. Both
applications are hereby incorporated by reference herein.
TECHNICAL FIELD
[0002] The present invention relates generally to polycrystalline
diamond compact ("PDC") cutters; and more particularly, to PDC
cutters having improved thermal stability.
BACKGROUND
[0003] Polycrystalline diamond compacts ("PDC") have been used in
industrial applications, including rock drilling applications and
metal machining applications. Such compacts have demonstrated
advantages over some other types of cutting elements, such as
better wear resistance and impact resistance. The PDC can be formed
by sintering individual diamond particles together under the high
pressure and high temperature ("HPHT") conditions referred to as
the "diamond stable region," which is typically above forty
kilobars and between 1,200 degrees Celsius and 2,000 degrees
Celsius, in the presence of a catalyst/solvent which promotes
diamond-diamond bonding. Some examples of catalyst/solvents for
sintered diamond compacts are cobalt, nickel, iron, and other Group
VIII metals. PDCs usually have a diamond content greater than
seventy percent by volume, with about eighty percent to about
ninety-five percent being typical. An unbacked PDC can be
mechanically bonded to a tool (not shown), according to one
example. Alternatively, the PDC can be bonded to a substrate,
thereby forming a PDC cutter, which is typically insertable within
a downhole tool (not shown), such as a drill bit or a reamer.
[0004] FIG. 1 shows a side view of a PDC cutter 100 having a
polycrystalline diamond ("PCD") cutting table 110, or compact, in
accordance with the prior art. Although a PCD cutting table 110 is
described in the exemplary embodiment, other types of cutting
tables, including cubic boron nitride ("CBN") compacts, are used in
alternative types of cutters. Referring to FIG. 1, the PDC cutter
100 typically includes the PCD cutting table 110 and a substrate
150 that is coupled to the PCD cutting table 110. The PCD cutting
table 110 is about one hundred thousandths of an inch (2.5
millimeters) thick; however, the thickness is variable depending
upon the application in which the PCD cutting table 110 is to be
used.
[0005] The substrate 150 includes a top surface 152, a bottom
surface 154, and a substrate outer wall 156 that extends from the
circumference of the top surface 152 to the circumference of the
bottom surface 154. The PCD cutting table 110 includes a cutting
surface 112, an opposing surface 114, and a PCD cutting table outer
wall 116 that extends from the circumference of the cutting surface
112 to the circumference of the opposing surface 114. The opposing
surface 114 of the PCD cutting table 110 is coupled to the top
surface 152 of the substrate 150. Typically, the PCD cutting table
110 is coupled to the substrate 150 using a high pressure and high
temperature ("HPHT") press. However, other methods known to people
having ordinary skill in the art can be used to couple the PCD
cutting table 110 to the substrate 150. In one embodiment, upon
coupling the PCD cutting table 110 to the substrate 150, the
cutting surface 112 of the PCD cutting table 110 is substantially
parallel to the substrate's bottom surface 154. Additionally, the
PDC cutter 100 has been illustrated as having a right circular
cylindrical shape; however, the PDC cutter 100 is shaped into other
geometric or non-geometric shapes in other embodiments. In certain
embodiments, the opposing surface 114 and the top surface 152 are
substantially planar; however, the opposing surface 114 and the top
surface 152 can be non-planar in other embodiments. Additionally,
according to some exemplary embodiments, a bevel (not shown) is
formed around at least the circumference of the PCD cutting table
110.
[0006] According to one example, the PDC cutter 100 is formed by
independently forming the PCD cutting table 110 and the substrate
150, and thereafter bonding the PCD cutting table 110 to the
substrate 150. Alternatively, the substrate 150 is initially formed
and the PCD cutting table 110 is then formed on the top surface 152
of the substrate 150 by placing polycrystalline diamond powder onto
the top surface 152 and subjecting the polycrystalline diamond
powder and the substrate 150 to a high temperature and high
pressure process. Alternatively, the substrate 150 and the PCD
cutting table 110 are formed and bonded together at about the same
time. Although a few methods of forming the PDC cutter 100 have
been briefly mentioned, other methods known to people having
ordinary skill in the art can be used.
[0007] According to one example for forming the PDC cutter 100, the
PCD cutting table 110 is formed and bonded to the substrate 150 by
subjecting a layer of diamond powder and a mixture of tungsten
carbide and cobalt powders to HPHT conditions. The cobalt is
typically mixed with tungsten carbide and positioned where the
substrate 150 is to be formed. The diamond powder is placed on top
of the cobalt and tungsten carbide mixture and positioned where the
PCD cutting table 110 is to be formed. The entire powder mixture is
then subjected to HPHT conditions so that the cobalt melts and
facilitates the cementing, or binding, of the tungsten carbide to
form the substrate 150. The melted cobalt also diffuses, or
infiltrates, into the diamond powder and acts as a catalyst for
synthesizing diamonds and forming the PCD cutting table 110. Thus,
the cobalt acts as both a binder for cementing the tungsten carbide
and as a catalyst/solvent for the sintering of the diamond powder
to form diamond-diamond bonds. The cobalt also facilitates in
forming strong bonds between the PCD cutting table 110 and the
cemented tungsten carbide substrate 150.
[0008] Cobalt has been a preferred constituent of the PDC
manufacturing process. Traditional PDC manufacturing processes use
cobalt as the binder material for forming the substrate 150 and
also as the catalyst material for diamond synthesis because of the
large body of knowledge related to using cobalt in these processes.
The synergy between the large bodies of knowledge and the needs of
the process have led to using cobalt as both the binder material
and the catalyst material. However, as is known in the art,
alternative metals, such as iron, nickel, chromium, manganese, and
tantalum, can be used as a catalyst for diamond synthesis. When
using these alternative metals as a catalyst for diamond synthesis
to form the PCD cutting table 110, cobalt, or some other material
such as nickel chrome or iron, is typically used as the binder
material for cementing the tungsten carbide to form the substrate
150. Although some materials, such as tungsten carbide and cobalt,
have been provided as examples, other materials known to people
having ordinary skill in the art can be used to form the substrate
150, the PCD cutting table 110, and form bonds between the
substrate 150 and the PCD cutting table 110.
[0009] FIG. 2 is a schematic microstructural view of the PCD
cutting table 110 of FIG. 1 in accordance with the prior art.
Referring to FIGS. 1 and 2, the PCD cutting table 110 has diamond
particles 210, one or more interstitial spaces 212 formed between
the diamond particles 210, and cobalt 214 deposited within the
interstitial spaces 212. During the sintering process, the
interstitial spaces 212, or voids, are formed between the
carbon-carbon bonds and are located between the diamond particles
210. The diffusion of cobalt 214 into the diamond powder results in
cobalt 214 being deposited within these interstitial spaces 212
that are formed within the PCD cutting table 110 during the
sintering process.
[0010] Once the PCD cutting table 110 is formed, the PCD cutting
table 110 is known to wear quickly when the temperature reaches a
critical temperature. This critical temperature is about 750
degrees Celsius and is reached when the PCD cutting table 110 is
cutting rock formations or other known materials. The high rate of
wear is believed to be caused by the differences in the thermal
expansion rate between the diamond particles 210 and the cobalt 214
and also by the chemical reaction, or graphitization, that occurs
between cobalt 214 and the diamond particles 210. The coefficient
of thermal expansion for the diamond particles 210 is about
1.0.times.10.sup.-6 millimeters.sup.-1.times.Kelvin.sup.-1
("mm.sup.-1 K.sup.-1"), while the coefficient of thermal expansion
for the cobalt 214 is about 13.0.times.10.sup.-6 mm.sup.-1
K.sup.-1. Thus, the cobalt 214 expands much faster than the diamond
particles 210 at temperatures above this critical temperature,
thereby making the bonds between the diamond particles 210
unstable. The PCD cutting table 110 becomes thermally degraded at
temperatures above about 750 degrees Celsius and its cutting
efficiency deteriorates significantly.
[0011] Efforts have been made to slow the wear of the PCD cutting
table 110 at these high temperatures. These efforts include
performing an acid leaching process of the PCD cutting table 110
which removes the cobalt 214 from the interstitial spaces 212.
Typical leaching processes involve the presence of an acid solution
(not shown) which reacts with the cobalt 214 that is deposited
within the interstitial spaces 212 of the PCD cutting table 110.
According to one example of a typical leaching process, the PDC
cutter 100 is placed within an acid solution such that at least a
portion of the PCD cutting table 110 is submerged within the acid
solution. The acid solution reacts with the cobalt 214 along the
outer surfaces of the PCD cutting table 110. The acid solution
slowly moves inwardly within the interior of the PCD cutting table
110 and continues to react with the cobalt 214. However, as the
acid solution moves further inwards, the reaction byproducts become
increasingly more difficult to remove; and hence, the rate of
leaching slows down considerably. For this reason, a tradeoff
occurs between leaching process duration, wherein costs increase as
the leaching process duration increases, and the leaching depth.
Thus, the leaching depth is typically about 0.2 millimeter, but can
be more or less depending upon the PCD cutting table 110
requirements and/or the cost constraints. The removal of cobalt 214
alleviates the issues created due to the differences in the thermal
expansion rate between the diamond particles 210 and the cobalt 214
and due to graphitization. However, the leaching process is costly
and also has other deleterious effects on the PCD cutting table
110, such as loss of strength.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The foregoing and other features and aspects of the
invention are best understood with reference to the following
description of certain exemplary embodiments, when read in
conjunction with the accompanying drawings, wherein:
[0013] FIG. 1 shows a side view of a PDC cutter having a PCD
cutting table in accordance with the prior art;
[0014] FIG. 2 is a schematic microstructural view of the PCD
cutting table of FIG. 1 in accordance with the prior art;
[0015] FIG. 3A is a side view of a pre-sintered PDC cutter in
accordance with an exemplary embodiment of the present
invention;
[0016] FIG. 3B is a side view of a PDC cutter formed from sintering
the pre-sintered PDC cutter of FIG. 3A in accordance with an
exemplary embodiment of the present invention;
[0017] FIG. 4A is a side view of a pre-sintered PDC cutter in
accordance with another exemplary embodiment of the present
invention;
[0018] FIG. 4B is a side view of a PDC cutter formed from sintering
the pre-sintered PDC cutter of FIG. 4A in accordance with another
exemplary embodiment of the present invention; and
[0019] FIG. 5 is a phase diagram of cobalt and Element X in
accordance with an exemplary embodiment of the present
invention.
[0020] The drawings illustrate only exemplary embodiments of the
invention and are therefore not to be considered limiting of its
scope, as the invention may admit to other equally effective
embodiments.
BRIEF DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0021] The present invention is directed generally to
polycrystalline diamond compact ("PDC") cutters; and more
particularly, to PDC cutters having improved thermal stability.
Although the description of exemplary embodiments is provided below
in conjunction with a PDC cutter, alternate embodiments of the
invention may be applicable to other types of cutters or compacts
including, but not limited to, polycrystalline boron nitride
("PCBN") cutters or PCBN compacts. As previously mentioned, the
compact is mountable to a substrate to form a cutter or is
mountable directly to a tool for performing cutting processes. The
invention is better understood by reading the following description
of non-limiting, exemplary embodiments with reference to the
attached drawings, wherein like parts of each of the figures are
identified by like reference characters, and which are briefly
described as follows.
[0022] FIG. 3A is a side view of a pre-sintered PDC cutter 300 in
accordance with an exemplary embodiment of the present invention.
FIG. 3B is a side view of a PDC cutter 350 formed from sintering
the pre-sintered PDC cutter 300 of FIG. 3A in accordance with an
exemplary embodiment of the present invention. FIGS. 3A and 3B
provide one example for forming the PDC cutter 350. Referring to
FIGS. 3A and 3B, the pre-sintered PDC cutter 300 includes a
substrate layer 310 and a PCD cutting table layer 320, while the
PDC cutter 350 includes a substrate 360 and a PCD cutting table
370. The substrate layer 310 is positioned at the bottom of the
pre-sintered PDC cutter 300 and forms the substrate 360 upon
performing the sintering process. The PCD cutting table layer 320
is positioned atop the substrate layer 310 and forms the PCD
cutting table 370 upon performing the sintering process. Thus, the
PCD cutting table 370 is positioned atop the substrate 360.
[0023] The substrate layer 310 is formed from a mixture of
substrate powder 332 and a binder/catalyst material 334. The
substrate powder 332 is tungsten carbide powder; however, the
substrate powder 332 is formed from other suitable material known
to people having ordinary skill in the art without departing from
the scope and spirit of the exemplary embodiment according to other
exemplary embodiments. The binder/catalyst material 334 is any
material capable of behaving as a binder material for the substrate
powder 310 and as a catalyst material for the diamond powder 336,
or any other material, that forms the PCD cutting table layer 320.
Additionally, the binder/catalyst material 334 has a coefficient of
thermal expansion that is less than the coefficient of thermal
expansion of cobalt and/or has a higher thermal conductivity than
the thermal conductivity of cobalt. The coefficient of thermal
expansion for cobalt is about 13.0.times.10.sup.-6 mm.sup.-1
K.sup.-1. The thermal conductivity for cobalt is about 100.0
Watts/(meters.times.Kelvin) ("W/(mK)"). Some examples of the
binder/catalyst material 334 includes, but is not limited to,
chromium, tantalum, ruthenium, certain alloys of cobalt such as
cobalt/molybdenum, cobalt/chromium, or cobalt/nickel/chrome,
certain alloys of a Group VIII metal and at least one non-catalyst
metal, and certain alloys of two or more Group VIII metals, wherein
the alloys furnish a net reduction in the coefficient of thermal
expansion and/or a net increase in the thermal conductivity. Other
examples of suitable alloys are determinable by people having
ordinary skill in the art once having the benefit of the present
disclosure. The binder/catalyst material 334 includes any eutectic
or near eutectic alloy that is effective as a catalyst material for
diamond synthesis while exhibiting either a lower coefficient of
thermal expansion than cobalt and/or a higher thermal conductivity
than cobalt. A near eutectic alloy is defined to include alloy
compositions that are within plus or minus ten atomic weight
percent from the eutectic composition as long as the melting point
of cobalt is not exceeded.
[0024] If the binder/catalyst material 334 has a lower coefficient
of thermal expansion than cobalt, the carbon-carbon bonds which
form the PCD cutting table 370 are more stable than if cobalt were
used because the binder/catalyst material 334 expands at a lesser
rate than cobalt. Hence, the carbon-carbon bonds are better able to
withstand the expansion of the binder/catalyst material 334 than
the expansion of cobalt at the same temperature. If the
binder/catalyst material 334 has a higher thermal conductivity than
cobalt, the heat generated within the PCD cutting table 370
dissipates better when the binder/catalyst material 334 is used to
form the PCD cutting table 370 than when cobalt is used. Thus, the
PCD cutting table 370 is able to withstand more heat generation and
hence higher temperatures when the binder/catalyst material 334 is
used to form the PCD cutting table 370.
[0025] Once subjected to high pressure and high temperature
conditions, the substrate layer 310 forms the substrate 360. The
substrate layer 310 includes a top layer surface 312, a bottom
layer surface 314, and a substrate layer outer wall 316 that
extends from the circumference of the top layer surface 312 to the
circumference of the bottom layer surface 314. The substrate layer
310 is formed into a right circular cylindrical shape according to
one exemplary embodiment, but can be formed into other geometric or
non-geometric shapes.
[0026] The PCD cutting table layer 320 is formed from a diamond
powder 336; however, other suitable materials known to people
having ordinary skill in the art can be used without departing from
the scope and spirit of the exemplary embodiment. Although not
depicted, according to some exemplary embodiments, the PCD cutting
table layer 320 includes the diamond powder 336 and the
binder/catalyst material 334. Once subjected to high pressure and
high temperature conditions, the PCD cutting table layer 320 forms
the PCD cutting table 370. The PCD cutting table layer 320 includes
a cutting layer surface 322, an opposing layer surface 324, and a
PCD cutting table layer outer wall 326 that extends from the
circumference of the cutting layer surface 322 to the circumference
of the opposing layer surface 324.
[0027] Once the pre-sintered PDC cutter 300 is formed, the
pre-sintered PDC cutter 300 is subjected to high pressure and high
temperature conditions to form the PDC cutter 350. During the HPHT
conditions, the binder/catalyst material 334 liquefies within the
substrate layer 310 and advances, or infiltrates, into the PCD
cutting table layer 320. The binder/catalyst material 334 behaves
as a binder material for the substrate powder 332, which then is
cemented, or binded, to form a cemented substrate powder 382. This
cemented substrate powder 382, along with the binder/catalyst
material 334 being interspersed therein, forms the substrate 360
upon completion of the sintering process. The liquefied
binder/catalyst material 334 diffuses into the PCD cutting table
layer 320 from the substrate layer 310 and also behaves as a
catalyst material for the diamond powder 336 within the PCD cutting
table layer 320. The binder/catalyst material 334 facilitates
diamond crystal intergrowth, thereby transforming the diamond
powder 336 into a diamond lattice 386. The diamond lattice 386
includes interstitial spaces (not shown), which is similar to the
interstitial spaces 212 (FIG. 2), that are formed during the
sintering process. The binder/catalyst material 334 is deposited
within these interstitial spaces. Thus, the diamond lattice 386,
along with the binder/catalyst material 334 deposited within the
interstitial spaces, forms the PCD cutting table 370 upon
completion of the sintering process. Although the diamond lattice
386 is formed in the PCD cutting table 370, other lattices are
formed in the PCD cutting table 370 when other materials, different
than diamond powder 336, is used. The binder/catalyst material 334
also facilitates in forming bonds between the PCD cutting table 370
and the substrate 360.
[0028] The PDC cutter 350 is formed once the substrate 360 and the
PCD cutting layer 370 are completely formed and the substrate 360
is bonded to the PCD cutting layer 370. The substrate 360 includes
a top surface 362, a bottom surface 364, and a substrate outer wall
366 that extends from the circumference of the top surface 362 to
the circumference of the bottom surface 364. The substrate 360
includes cemented substrate powder 382 and binder/catalyst material
334 interspersed therein. The substrate 360 is formed into a right
circular cylindrical shape according to one exemplary embodiment,
but can be formed into other geometric or non-geometric shapes
depending upon the application for the PDC cutter 350.
[0029] The PCD cutting table 370 includes a cutting surface 372, an
opposing surface 374, and a PCD cutting table outer wall 376 that
extends from the circumference of the cutting surface 372 to the
circumference of the opposing surface 374. The PCD cutting table
370 includes the diamond lattice 386 and the binder/catalyst
material 334 deposited within the interstitial spaces formed within
the diamond lattice 386. The opposing surface 374 is bonded to the
top surface 362. According to some exemplary embodiments, a bevel
(not shown) is formed around the circumference of the PCD cutting
table 370.
[0030] The PCD cutting table 370 is bonded to the substrate 360
according to methods known to people having ordinary skill in the
art. In one example, the PDC cutter 350 is formed by independently
forming the PCD cutting table 370 and the substrate 360, and
thereafter bonding the PCD cutting table 370 to the substrate 360.
In another example, the substrate 360 is initially formed and the
PCD cutting table 370 is then formed on the top surface 362 of the
substrate 360 by placing polycrystalline diamond powder 336 onto
the top surface 362 and subjecting the polycrystalline diamond
powder 336 and the substrate 360 to a high temperature and high
pressure process.
[0031] In one exemplary embodiment, upon coupling the PCD cutting
table 370 to the substrate 360, the cutting surface 372 of the PCD
cutting table 370 is substantially parallel to the bottom surface
364 of the substrate 360. Additionally, the PDC cutter 350 has been
illustrated as having a right circular cylindrical shape; however,
the PDC cutter 350 is shaped into other geometric or non-geometric
shapes in other exemplary embodiments. In certain exemplary
embodiments, the opposing surface 374 and the top surface 362 are
substantially planar; however, the opposing surface 374 and the top
surface 362 can be non-planar in other exemplary embodiments.
[0032] FIG. 4A is a side view of a pre-sintered PDC cutter 400 in
accordance with another exemplary embodiment of the present
invention. FIG. 4B is a side view of a PDC cutter 450 formed from
sintering the pre-sintered PDC cutter 400 of FIG. 4A in accordance
with another exemplary embodiment of the present invention. FIGS.
4A and 4B provide one example for forming the PDC cutter 450.
Referring to FIGS. 4A and 4B, the pre-sintered PDC cutter 400
includes a substrate layer 410 and a PCD cutting table layer 420,
while the PDC cutter 450 includes a substrate 460 and a PCD cutting
table 470. The substrate layer 410 is positioned at the bottom of
the pre-sintered PDC cutter 400 and forms the substrate 460 upon
performing the sintering process. The PCD cutting table layer 420
is positioned atop the substrate layer 410 and forms the PCD
cutting table 470 upon performing the sintering process. Thus, the
PCD cutting table 470 is positioned atop the substrate 460.
[0033] The substrate layer 410 is formed from a mixture of a
substrate powder 432 and a binder material 434. The substrate
powder 432 is tungsten carbide powder; however, the substrate
powder 432 is formed from other suitable material known to people
having ordinary skill in the art without departing from the scope
and spirit of the exemplary embodiment according to some other
exemplary embodiments. The binder material 434 is any material
capable of behaving as a binder for the substrate powder 410. Some
examples of the binder material 434 include, but are not limited
to, cobalt, nickel chrome, and iron. Once subjected to high
pressure and high temperature conditions, the substrate layer 410
forms the substrate 460. The substrate layer 410 includes a top
layer surface 412, a bottom layer surface 414, and a substrate
layer outer wall 416 that extends from the circumference of the top
layer surface 412 to the circumference of the bottom layer surface
414. The substrate layer 410 is formed into a right circular
cylindrical shape according to one exemplary embodiment, but can be
formed into other geometric or non-geometric shapes.
[0034] The PCD cutting table layer 420 is formed from a mixture of
a diamond powder 436 and a catalyst material 438. Although diamond
powder 436 is used to form the PCD cutting table layer 420, other
suitable materials known to people having ordinary skill in the art
can be used without departing from the scope and spirit of the
exemplary embodiment. The catalyst material 438 is any material
capable of behaving as a catalyst for the diamond powder 436 that
forms the PCD cutting table layer 420 or for any other material
that is used to form the PCD cutting table 470. Additionally, the
catalyst material 438 has a coefficient of thermal expansion that
is less than the coefficient of thermal expansion of cobalt and/or
has a higher thermal conductivity than the thermal conductivity of
cobalt. The coefficient of thermal expansion for cobalt is about
13.0.times.10.sup.-6 mm.sup.-1 K.sup.-1. The thermal conductivity
for cobalt is about 100.0 W/(mK). Some examples of the catalyst
material 438 include, but are not limited to, chromium, tantalum,
ruthenium, certain alloys of cobalt such as cobalt/molybdenum,
cobalt/chromium, or cobalt/nickel/chrome, certain alloys of a Group
VIII metal and at least one non-catalyst metal, and certain alloys
of two or more Group VIII metals, wherein the alloys furnish a net
reduction in the coefficient of thermal expansion and/or a net
increase in the thermal conductivity. Other examples of suitable
alloys are determinable by people having ordinary skill in the art
once having the benefit of the present disclosure. The catalyst
material 438 includes any eutectic or near eutectic alloy that is
effective as a catalyst for diamond synthesis while exhibiting a
lower coefficient of thermal expansion than cobalt and/or a higher
thermal conductivity than cobalt.
[0035] If the catalyst material 438 has a lower coefficient of
thermal expansion than cobalt, the carbon-carbon bonds which form
the PCD cutting table 470 are more stable than if cobalt were used
because the catalyst material 438 expands at a lesser rate than
cobalt. Hence, the carbon-carbon bonds are better able to withstand
the expansion of the catalyst material 438 than the expansion of
cobalt at the same temperature. If the catalyst material 438 has a
higher thermal conductivity than cobalt, the heat generated within
the PCD cutting table 470 dissipates better when the catalyst
material 438 is used to form the PCD cutting table 470 than when
cobalt is used. Thus, the PCD cutting table 470 is able to
withstand more heat generation and hence higher temperatures when
the catalyst material 438 is used to form the PCD cutting table
470.
[0036] According to some exemplary embodiments, the melting point
of the catalyst material 438 is lower than the melting point of the
binder material 434. The melting point of cobalt, which can be used
as the binder material 434, is about 1495 degrees Celsius.
According to some exemplary embodiments, the binder material 434
and the catalyst material 438 are different materials; however, the
binder material 434 and the catalyst material 438 can be the same
material according to some exemplary embodiments. Once subjected to
high pressure and high temperature conditions, the PCD cutting
table layer 420 forms the PCD cutting table 470. The PCD cutting
table layer 420 includes a cutting layer surface 422, an opposing
layer surface 424, and a PCD cutting table layer outer wall 426
that extends from the circumference of the cutting layer surface
422 to the circumference of the opposing layer surface 424.
According to some exemplary embodiments, a bevel (not shown) is
formed around the circumference of the PCD cutting table 470.
[0037] According to exemplary embodiments where the melting point
of the catalyst material 438 is lower than the melting point of the
binder material 434, once the pre-sintered PDC cutter 400 is
formed, the pre-sintered PDC cutter 400 is subjected to high
pressure and high temperature conditions to form the PDC cutter
450. During the HPHT conditions, the temperature is initially
brought to a first temperature, which is the melting point of the
catalyst material 438 according to some exemplary embodiments.
According to some exemplary embodiments, the first temperature is
higher than the melting point of the catalyst material 438, but
maintained below a second temperature, which is discussed in
further detail below. The first temperature can be varied within
this range that is between the first temperature and the second
temperature. At this first temperature, the catalyst material 438
liquefies within the PCD cutting table layer 470 and facilitates
diamond crystal intergrowth, thereby transforming the diamond
powder 436 into a diamond lattice 486. The diamond lattice 486
includes interstitial spaces (not shown), which is similar to the
interstitial spaces 212 (FIG. 2), that are formed during the
sintering process. The catalyst material 438 is deposited within
these interstitial spaces. Thus, the diamond lattice 486, along
with the catalyst material 438 deposited within the interstitial
spaces, forms the PCD cutting table 470 upon completion of the
sintering process. Although the diamond lattice 486 is formed in
the PCD cutting table 470, other lattices are formed in the PCD
cutting table 470 when other materials, different than diamond
powder 436, is used.
[0038] Once the PCD cutting table 470 is formed, the temperature is
then increased from the first temperature to at least a second
temperature, which is the melting point of the binder material 434
or some other higher temperature above the melting point of the
binder material 434. The binder material 434 liquefies within the
substrate layer 410 and facilitates cementing of the substrate
powder 432, thereby transforming the substrate powder 432 into a
cemented substrate powder 482. This cemented substrate powder 482,
along with the binder material 434 being interspersed therein,
forms the substrate 460 upon completion of the sintering process.
The binder material 434 and/or the catalyst material 438 facilitate
forming bonds between the PCD cutting table 470 and the substrate
460.
[0039] The PDC cutter 450 is formed once the substrate 460 and the
PCD cutting layer 470 are completely formed and the substrate 460
is bonded to the PCD cutting layer 470. The substrate 460 includes
a top surface 462, a bottom surface 464, and a substrate outer wall
466 that extends from the circumference of the top surface 462 to
the circumference of the bottom surface 464. The substrate 460
includes cemented substrate powder 482 and binder material 434
interspersed therein. The substrate 460 is formed into a right
circular cylindrical shape according to one exemplary embodiment,
but can be formed into other geometric or non-geometric shapes
depending upon the application for the PDC cutter 450.
[0040] The PCD cutting table 470 includes a cutting surface 472, an
opposing surface 474, and a PCD cutting table outer wall 476 that
extends from the circumference of the cutting surface 472 to the
circumference of the opposing surface 474. The PCD cutting table
470 includes the diamond lattice 486 and the catalyst material 438
deposited within the interstitial spaces formed within the diamond
lattice 486. The opposing surface 474 is bonded to the top surface
462.
[0041] The PCD cutting table 470 is bonded to the substrate 460
according to methods known to people having ordinary skill in the
art. In one example, the PDC cutter 450 is formed by independently
forming the PCD cutting table 470 and the substrate 460, and
thereafter bonding the PCD cutting table 470 to the substrate 460.
In another example, the substrate 460 is initially formed and the
PCD cutting table 470 is then formed on the top surface 462 of the
substrate 460 by placing polycrystalline diamond powder 436 onto
the top surface 462 and subjecting the polycrystalline diamond
powder 436 and the substrate 460 to a high temperature and high
pressure process.
[0042] In one exemplary embodiment, upon coupling the PCD cutting
table 470 to the substrate 460, the cutting surface 472 of the PCD
cutting table 470 is substantially parallel to the bottom surface
464 of the substrate 460. Additionally, the PDC cutter 450 has been
illustrated as having a right circular cylindrical shape; however,
the PDC cutter 450 is shaped into other geometric or non-geometric
shapes in other exemplary embodiments. In certain exemplary
embodiments, the opposing surface 474 and the top surface 462 are
substantially planar; however, the opposing surface 474 and the top
surface 462 can be non-planar in other exemplary embodiments.
[0043] As previously mentioned, the binder/catalyst material 334
(FIG. 3) and the catalyst material 438 are an alloy of cobalt or
some other group VIII metal which exhibit a lower coefficient of
thermal expansion than cobalt and/or a higher thermal conductivity
than cobalt according to some exemplary embodiments. An alloy is a
combination, either in solution or compound, of two or more
elements, at least one of which is a metal, and where the resultant
material alloy has metallic properties. Unlike pure metals, many
alloys do not have a single melting point. Instead, many alloys
have a temperature range where the material begins melting at one
lower temperature and is completely melted at another higher
temperature. Thus, during the melting of the alloy, the material is
a mixture of solid and liquid phases when subjected to a
temperature between these two temperatures. The temperature at
which the alloy starts melting is referred to as the solidus, while
the temperature at which the alloy is completely melted is referred
to as the liquidus. However, also as previously mentioned and
according to some exemplary embodiments, the binder/catalyst
material 334 (FIG. 3) and the catalyst material 438 are a eutectic
alloy or near eutectic alloy which exhibits a lower coefficient of
thermal expansion than cobalt and/or a higher thermal conductivity
than cobalt. Eutectic alloys are fabricated to melt at a single
melting point temperature and not within a temperature range. The
eutectic alloy is an alloy formed from the mixture of two or more
elements which has a lower melting point that any of its elements
that are used to form the eutectic alloy. In one example, the alloy
or eutectic alloy is formed by preparing a homogeneous mixture of
the two or more elements that form the alloy or eutectic alloy. The
proper ratios of components to obtain a eutectic alloy is
identified by the eutectic point on a phase diagram, which is
discussed in further detail with respect to FIG. 5.
[0044] Provided below in Table I is a list of elements that can be
alloyed with cobalt to form a eutectic alloy that has a resulting
coefficient of thermal expansion that is lower than the coefficient
of thermal expansion for cobalt. The elements of carbon and cobalt
are provided as references in Table I since carbon is used to form
the PCD cutting table, while cobalt is the typical catalyst
material 438 or binder/catalyst material 334 (FIG. 3) that is
deposited within the interstitial spaces formed between the carbon
bonds in the PCD cutting table 370 and 470. Thus, the eutectic
alloy being used as the catalyst material 438 or the
binder/catalyst material 334 (FIG. 3) in exemplary embodiments of
the present invention should have a lower resulting coefficient of
thermal expansion and/or a higher resulting thermal conductivity
than cobalt alone. Although cobalt is being chosen as one of the
alloying elements, any other group VIII metal can be chosen as the
alloying element according to other exemplary embodiments.
TABLE-US-00001 TABLE I Thermal Expansion Melting Thermal Co-Eu
.times.10.sup.-6 m Point conductivity Element Sym C. m.sup.-1
K.sup.-1 C. W/(m K) Carbon C 1.0 3675 900.00 Silicon Si 1195 2.6
1410 149.00 Tungsten W 1471 4.5 3407 173.00 Molybdenum Mo 1335 4.8
2617 138.00 Chromium Cr 1402 4.9 1857 93.90 Osmium Os 1590 5.1 3027
87.60 Zirconium Zr 1232 5.7 1852 22.60 Hafnium Hf 1270 5.9 2227
23.00 Boron B 6.0 2300 27.40 Germanium Ge 810 6.0 938 60.20 Rhenium
Re 1520 6.2 3180 48.00 Cerium Ce 6.3 798 11.30 Tantalum Ta 1276 6.3
2996 57.50 Iridium Ir 6.4 2443 147.00 Ruthenium Ru 1390 6.4 2250
117.00 Praseodymium Pr 541 6.7 931 12.50 Niobium Nb 1237 7.3 2468
53.70 Rhodium Rh 1390 8.2 1966 150.00 Vanadium V 1242 8.4 1902
30.70 Titanium Ti 1020 8.6 1660 21.90 Platinum Pt 1430 8.8 1772
71.60 Gadolinium Gd 650 9.4 1312 10.60 Neodymium Nd 566 9.6 1016
16.50 Dysprosium Dy 714 9.9 1407 10.70 Lutetium Lu 9.9 1663 16.40
Scandium Sc 790 10.2 1539 15.80 Terbium Tb 960 10.3 1357 11.10
Yttrium Y 715 10.6 1526 17.20 Promethium Pm 11.0 931 17.90 Antimony
Sb 623 11.0 631 24.40 Thorium Th 975 11.0 1755 54.00 Holmium Ho 770
11.2 1470 16.20 Beryllium Be 11.3 1287 200.00 Iron Fe 1476 11.8
1535 80.40 Palladium Pd 1219 11.8 1552 71.80 Lanthanum La 500 12.1
920 13.40 Erbium Er 800 12.2 1522 14.50 Samarium Sm 575 12.7 1072
13.30 Cobalt Co 13.0 1495 100.00
[0045] As shown in the above table, each element is provided with
values for a "Co--Eu," a "thermal expansion," a "melting point,"
and a "thermal conductivity." The value for the "Co--Eu" is the
eutectic melting temperature, or eutectic melting point, when the
corresponding element is alloyed with cobalt in accordance with a
eutectic composition. The value for the "thermal expansion" is the
coefficient of thermal expansion for the corresponding element.
These coefficients of thermal expansion are less than the
coefficient of thermal expansion for cobalt. Once the element is
alloyed with cobalt, the resulting coefficient of thermal expansion
for the alloy is less than the coefficient of thermal expansion for
cobalt. Hence, the coefficient of thermal expansion for the
eutectic alloy also is less than the coefficient of thermal
expansion for cobalt. The value for the "melting point" is the
melting point for the corresponding element. As seen the eutectic
melting temperature for when the corresponding element is alloyed
with cobalt is less than the melting point of either the cobalt and
the corresponding element. The value for the "thermal conductivity"
is the thermal conductivity for the corresponding element. These
thermal conductivity values are higher or lower than the thermal
conductivity for cobalt. Once the element is alloyed with cobalt,
the resulting thermal conductivity value for the alloy is between
the thermal conductivity for the corresponding element and the
thermal conductivity for cobalt. Hence, depending upon the
applications that the PDC cutter 350 and 450 is to be used in, the
alloy, or eutectic alloy, that is to be used for the catalyst
material 438 and the binder/catalyst material 334 (FIG. 3) can be
chosen appropriately to have either a lower coefficient of thermal
expansion and/or a higher thermal conductivity.
[0046] FIG. 5 is a phase diagram of cobalt and Element X 500 in
accordance with an exemplary embodiment of the present invention.
Although phase diagram of cobalt and Element X 500 is provided as
an example according to one exemplary embodiment, different phase
diagrams of cobalt and one or more other elements or a group VIII
element with one or more other elements can be used for obtaining a
eutectic point, which is described in further detail below,
according to other exemplary embodiments. Referring to FIG. 5, the
phase diagram of cobalt and Element X 500 includes a composition
axis 510, a temperature axis 520, a liquidus line 534, a solidus
line 536, and a eutectic point 538.
[0047] The composition axis 510 is positioned on the x-axis and
represents the composition of the alloy used as the catalyst
material and/or the binder/catalyst material. The composition is
measured in atomic weight percent of Element X. Proceeding from
left to right along the composition axis 510, the composition of
Element X increases. Thus, at the extreme left of the composition
axis 510, the material is one hundred percent cobalt. Conversely,
at the extreme right of the composition axis 510, the material is
one hundred percent element X. The composition axis 510 includes a
eutectic composition 540, which is discussed in further detail
below.
[0048] The temperature axis 520 is positioned on the y-axis and
represents the various temperatures that can be subjected on the
alloy. The temperature is measured in degrees Celsius. Proceeding
from top to bottom along the temperature axis 520, the temperature
decreases. The temperature axis 520 includes a cobalt melting
temperature 532, an Element X melting temperature 530, and a
eutectic melting temperature 539, which is discussed in further
detail below. The cobalt melting temperature 532 is the temperature
at which a material having one hundred percent cobalt melts. The
Element X melting temperature 530 is the temperature at which a
material having one hundred percent Element X melts.
[0049] The phase diagram of cobalt and Element X 500 provides
information on different phases of the cobalt and Element X alloy
and under what compositions and temperatures these different phases
exist. These phases include the total liquid phase 550 ("Liquid"),
the total solid phase 552 ("Solid"), a cobalt slurry phase 554
("L+Co.sub.s"), an Element X slurry phase 556 ("L+X.sub.s"), a
cobalt solid phase 558 ("Co.sub.s"), and a Element X solid phase
560 ("X.sub.s"). The total liquid phase 550 occurs when both cobalt
and Element X are both completely in the liquid phase. The total
solid phase 552 occurs when both cobalt and Element X are both
completely in the solid phase. The cobalt slurry phase 554 occurs
when the material has cobalt crystals that is suspended in a slurry
which also includes liquid cobalt. The Element X phase 556 occurs
when the material has Element X crystals that is suspended in a
slurry which also includes liquid Element X. The cobalt solid phase
558 occurs when all the cobalt is in solid phase and at least some
portion of the Element X is in liquid phase. The Element X solid
phase 560 occurs when all the Element X is in solid phase and at
least some portion of the cobalt is in liquid phase.
[0050] The liquidus line 534 extends from the cobalt melting
temperature 532 to a eutectic point 538 and then to the Element X
melting temperature 530. The liquidus line 534 represents the
temperature at which the alloy completely melts and forms a liquid.
Thus, at temperatures above the liquidus line 534, the alloy is
completely liquid. The solidus line 536 also extends from the
cobalt melting temperature 532 to a eutectic point 538 and then to
the Element X melting temperature 530. The solidus line 536 is
positioned below the liquidus line 534, except for at the eutectic
point 538. The solidus line 536 represents the temperature at which
the alloy begins to melt. Thus, at temperatures below the solidus
line 536, the alloy is completely solid. At the eutectic point 538,
the liquidus line 534 intersects with the solidus line 536. The
eutectic point 538 is defined on the phase diagram 500 as the
intersection of the eutectic temperature 539 and the eutectic
composition 540. The eutectic composition 540 is the composition
where the alloy behaves as a single chemical composition and has a
melting point where the total solid phase turns into a total liquid
phase at a single temperature. Thus, one benefit for using the
eutectic alloy for the catalyst material and/or the binder/catalyst
material is that the eutectic alloy behaves as a single
composition.
[0051] Although each exemplary embodiment has been described in
detail, it is to be construed that any features and modifications
that are applicable to one embodiment are also applicable to the
other embodiments. Furthermore, although the invention has been
described with reference to specific embodiments, these
descriptions are not meant to be construed in a limiting sense.
Various modifications of the disclosed embodiments, as well as
alternative embodiments of the invention will become apparent to
persons of ordinary skill in the art upon reference to the
description of the exemplary embodiments. It should be appreciated
by those of ordinary skill in the art that the conception and the
specific embodiments disclosed may be readily utilized as a basis
for modifying or designing other structures or methods for carrying
out the same purposes of the invention. It should also be realized
by those of ordinary skill in the art that such equivalent
constructions do not depart from the spirit and scope of the
invention as set forth in the appended claims. It is therefore,
contemplated that the claims will cover any such modifications or
embodiments that fall within the scope of the invention.
* * * * *