U.S. patent application number 14/995340 was filed with the patent office on 2016-05-12 for high toughness thermally stable polycrystalline diamond.
The applicant listed for this patent is VAREL EUROPE S.A.S.. Invention is credited to Federico Bellin.
Application Number | 20160129554 14/995340 |
Document ID | / |
Family ID | 45816718 |
Filed Date | 2016-05-12 |
United States Patent
Application |
20160129554 |
Kind Code |
A1 |
Bellin; Federico |
May 12, 2016 |
HIGH TOUGHNESS THERMALLY STABLE POLYCRYSTALLINE DIAMOND
Abstract
A mixture for fabricating a cutting table, the cutting table,
and a method of fabricating the cutting table. The mixture includes
a cutting table powder and a binder. The binder includes at least
one carbide formed from an element selected from at least one of
Groups IV, V, and VI of the Periodic Table. The carbide is in its
nonstoichiometric and/or stoichiometric form. The binder can
include the element. In certain embodiments, the binder includes
one or more of the cutting table powder and a catalyst. The cutting
table is formed by sintering the mixture using a solid phase
sintering process or a near solid phase sintering process. When
forming or coupling the cutting table to a substrate, a divider is
positioned and coupled therebetween to ensure that the sintering
process that forms the cutting table occurs using the solid phase
sintering process or the near solid phase sintering process.
Inventors: |
Bellin; Federico; (Tomball,
TX) |
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Applicant: |
Name |
City |
State |
Country |
Type |
VAREL EUROPE S.A.S. |
PAU |
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FR |
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|
Family ID: |
45816718 |
Appl. No.: |
14/995340 |
Filed: |
January 14, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13968257 |
Aug 15, 2013 |
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14995340 |
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12884446 |
Sep 17, 2010 |
8522900 |
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13968257 |
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Current U.S.
Class: |
51/309 |
Current CPC
Class: |
C22C 2026/006 20130101;
B22F 7/06 20130101; C22C 26/00 20130101; C22C 29/08 20130101; B22F
2005/001 20130101; B24D 3/06 20130101; E21B 10/5735 20130101; B24D
18/0009 20130101 |
International
Class: |
B24D 3/06 20060101
B24D003/06; B24D 18/00 20060101 B24D018/00 |
Claims
1. A method for fabricating a cutter, comprising: preparing a
binder material, the binder material comprising a metal carbide
formed from a single metal, wherein: the single metal is selected
from Groups IV, V, and VI, at least one of: the metal carbide is
non-stoichiometric, and the metal carbide is stoichiometric and the
binder material further comprises a free portion of the single
metal, mixing the binder material with a diamond powder; performing
a sintering process on the diamond powder and the binder material,
wherein the sintering process causes the diamond powder to form a
polycrystalline diamond structure having modified binder material
deposited within interstitial spaces thereof, wherein: the metal
carbide of the modified binder material is stoichiometric, and the
modified binder material is void of the free portion of the
metal.
2. The method of claim 1, wherein the sintering process is a solid
phase sintering process.
3. The method of claim 1, wherein: the sintering process is a near
solid phase sintering process, a transient liquid phase is formed
during the near solid phase sintering process, and the transient
liquid phase is present during ten percent or less of the duration
of the sintering process.
4. The method of claim 3, wherein the transient liquid phase is
present during six percent or less of the duration of the sintering
process.
5. The method of claim 1, wherein the metal carbide of the binder
material is non-stoichiometric.
6. The method of claim 1, wherein the binder material comprises the
stoichiometric carbide and the free portion of the single
metal.
7. The method of claim 1, wherein the binder material further
comprises a catalyst material selected from a group consisting of
cobalt, nickel, and iron.
8. The method of claim 7, wherein the binder material comprises ten
percent by volume or less of the catalyst material.
9. The method of claim 7, wherein the binder material comprises one
percent by volume or less of the catalyst material.
10. The method of claim 7, wherein a composition of the catalyst
material in the polycrystalline diamond structure is
non-eutectic.
11. The method of claim 1, further comprising: forming a substrate
from at least a substrate powder and a second binder material; and
bonding a divider to the polycrystalline diamond structure and to
the substrate, the divider being positioned therebetween, the
divider preventing the second binder material from migrating into
the polycrystalline diamond structure.
12. The method of claim 11, wherein the divider is formed using the
single metal.
13. The method of claim 1, further comprising: positioning a metal
divider atop a substrate layer; and positioning the mixture atop
the metal divider, wherein the sintering process is also performed
on the substrate layer and the divider.
14. The method of claim 13, wherein: the substrate layer comprises
tungsten carbide powder and a second binder material, the second
binder material is selected from a group consisting of cobalt,
nickel chrome, and iron, and the divider prevents the second binder
material from migrating into the polycrystalline diamond
structure.
15. The method of claim 1, wherein the mixture is homogenous.
16. The method of claim 1, wherein the binder material further
comprises diamond powder.
17. The method of claim 1, wherein a constant temperature is
maintained during the sintering process.
18. The method of claim 17, wherein the constant temperature is
greater than a eutectic melting temperature of the metal
carbide.
19. The method of claim 17, wherein the constant temperature is
less than a eutectic melting temperature of the metal carbide.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to polycrystalline
diamond compact ("PDC") cutters; and more particularly, to PDC
cutters having improved thermal stability and toughness.
BACKGROUND
[0002] Polycrystalline diamond compacts ("PDC") have been used in
industrial applications, including rock drilling applications and
metal machining applications. Such compacts have demonstrated
advantages, such as better wear resistance and impact resistance,
over some other types of cutting elements. Many different PDC
grades have been developed trying to achieve at the same time the
best wear abrasion 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
typically used for sintering 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] According to a typical 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 within a
press. The HPHT conditions are typically at pressures equal to or
greater than fifty-five kilobars and temperatures equal to or
greater than 1300 degrees Celsius. 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
the HPHT conditions within the press so that the cobalt liquefies
and facilitates the cementing, or binding, of the tungsten carbide
to form the substrate 150. The liquefied cobalt also diffuses, or
infiltrates, from the substrate 150 into the diamond powder and
acts as a catalyst for synthesizing diamonds and forming the PCD
cutting table 110. During the sintering process of the diamond
powder, the carbon from the diamond powder dissolves into the
liquefied cobalt and subsequently re-precipitates to create the
diamond to diamond bonding, which then forms the PCD cutting table
110. 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. This traditional process
where the catalyst/solvent, for example, cobalt, is liquefied and
the diamond powder is then sintered entirely with liquefied
catalyst/solvent is defined as a liquid phase pressure assisted
sintering process. Within the press, the catalyst/solvent is in the
liquid phase for about sixty percent of the time or greater.
[0007] 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, the conventional diamond
sintering process still occurs entirely once the catalyst is
liquefied.
[0008] 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. The cobalt 214 deposited within the interstitial
spaces 212 has a eutectic composition or near-eutectic
composition.
[0009] 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 hard 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.-1K.sup.-1"), while the coefficient of thermal expansion
for the cobalt 214 is about 13.0.times.10.sup.-6 mm.sup.-1K.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.
[0010] 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. Efforts within the industry are
ongoing to develop improved thermally stable polycrystalline
diamond that has improved toughness characteristics.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] 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:
[0012] FIG. 1 shows a side view of a PDC cutter having a PCD
cutting table in accordance with the prior art;
[0013] FIG. 2 is a schematic microstructural view of the PCD
cutting table of FIG. 1 in accordance with the prior art;
[0014] FIG. 3A is a side view of a pre-sintered PCD cutting table
in accordance with an exemplary embodiment of the present
invention;
[0015] FIG. 3B is a side view of a PCD cutting table formed from
sintering the pre-sintered PCD cutting table of FIG. 3A in
accordance with an exemplary embodiment of the present
invention;
[0016] FIG. 4 is a phase diagram of carbon and Element M in
accordance with an exemplary embodiment of the present
invention;
[0017] FIG. 5 is a schematic microscopic view of a diffusion
process occurring between two solid elements in accordance with an
exemplary embodiment of the present invention;
[0018] FIG. 6A is a side view of a pre-sintered PDC cutter in
accordance with an exemplary embodiment of the present invention;
and
[0019] FIG. 6B is a side view of a PDC cutter formed from sintering
the pre-sintered PDC cutter of FIG. 6A 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 and
hardness. Although the description of exemplary embodiments is
provided below in conjunction with a PDC cutter and/or a PCD
cutting table, 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 PCD cutting table
300 in accordance with an exemplary embodiment of the present
invention. FIG. 3B is a side view of a PCD cutting table 350 formed
from sintering the pre-sintered PCD cutting table 300 of FIG. 3A in
accordance with an exemplary embodiment of the present invention.
FIGS. 3A and 3B provide one example for forming the PCD cutting
table 350. Referring to FIGS. 3A and 3B, the pre-sintered PCD
cutting table 300 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. The
pre-sintered PCD cutting table 300 is fabricated using a diamond
powder 336 and a binder material 334.
[0023] The binder material 334 is premixed with the diamond powder
336 and forms the shape of the pre-sintered PCD cutting table 300,
which eventually forms the PCD cutting table 350. Although diamond
powder 336 is used in some of the exemplary embodiments, other
powder types, such as CBN powder or other known suitable powders,
are usable in other exemplary embodiments without departing from
the scope and spirit of the exemplary embodiment.
[0024] The binder material 334 includes at least one carbide 302 of
an element belonging to at least one of Groups IV, V, and VI of the
Periodic Table. Group IV of the Periodic Table includes elements of
Titanium (Ti), Zirconium (Zr), Hafnium (Hf), and Ununquadium (Unq).
Group V of the Periodic Table includes elements of Vanadium (V),
Niobium (Nb), Tantalum (Ta), and Ununpentium (Unp). Group VI of the
Periodic Table includes elements of Chromium (Cr), Molybdenum (Mo),
Tungsten (W), and Ununhexium (Unh). According to some exemplary
embodiments, the carbide 302 includes a carbide of a single element
from Groups IV, V, and VI. According to alternative exemplary
embodiments, the carbide 302 includes carbides of two or more
elements from Groups IV, V, and VI.
[0025] According to some exemplary embodiments, the carbide 302 is
in its non-stoichiometric form, for example, molybdenum carbide
(Mo.sub.2C.sub.x) and titanium carbide (TiC.sub.x) where x is less
than one. In alternative exemplary embodiments, however, the
carbide 302 is in its stoichiometric form, for example, molybdenum
carbide (Mo.sub.2C) and titanium carbide (TiC). In some exemplary
embodiments, the carbide 302 includes a combination of carbides
that are in their stoichiometric form and their non-stoichiometric
form. In some exemplary embodiments where at least a portion of the
carbide 302 is in its stoichiometric form, the binder material 334
also includes small quantities of metals 304 belonging to Group IV,
V, and VI of the Periodic Table that are used in forming the
carbide 302. Adding small quantities of metal 304 to the binder
material 334 when the carbide 302 includes carbides in their
stoichiometric form creates an imbalance between metal atoms and
carbon atoms, which thereby facilitates the diffusion process
between the metal 304 and the carbon. The binder material 334 is a
homogenized mixture when more than one component forms the binder
material 334.
[0026] The average particle size of the binder material 334 is in
the nanometer range, or at least in the submicron range, which
thereby increases the chemical reactivity of the binder material
334 and enhances the diamond sintering process. In certain
exemplary embodiments, the binder material 334 includes diamond
powder 336 to help the uniform mixing of the carbide 302 and the
metal 304. The diamond powder 336 used in the binder material 334
has an average particle size that is in the submicron range.
[0027] According to yet other exemplary embodiments, the binder
material 334 includes small quantities of catalyst metal (not
shown) which includes, but is not limited to, cobalt, nickel, iron,
and/or other catalyst materials known to people having ordinary
skill in the art. The catalyst metal facilitates the sintering
process and also behaves as a toughening agent. The catalyst metal
occupies a volumetric percentage that is about one percent or less
of the volume of the binder material 334. In some exemplary
embodiments, the catalyst metal occupies a volumetric percentage
that is about one-half percent or less of the volume of the binder
material 334. However, the catalyst metal can occupy a volumetric
percentage that is as much as about ten percent or less of the
volume of the binder material 334 according to alternative
exemplary embodiments.
[0028] One example of the components included in the binder
material 334 are ninety-five percent by volume of titanium carbide
and five percent by volume of titanium. Another example of the
components included in the binder material 334 are forty percent by
volume of tungsten carbide, fifty percent by volume of molybdenum
carbide, five percent by volume of tungsten, and five percent by
volume of molybdenum. In certain exemplary embodiments, one or more
of the tungsten carbide and the molybdenum carbide include the
carbides in their stoichiometric form and their non-stoichiometric
forms, for example, WC/W.sub.2C and Mo.sub.2C/MoC. In some
examples, small quantities of either or both of diamond powder and
catalyst metal are included within the binder material 334.
[0029] Once the binder material 334 is prepared and homogeneously
mixed, the binder material 334 is mixed with different cuts of
diamond powder 336 to form the pre-sintered PCD cutting table 300.
The diamond powder 336 occupies a volumetric percentage of about
seventy percent or more, while the binder material 334 occupies a
volumetric percentage of about thirty percent or less. In some
exemplary embodiments, the diamond powder 336 occupies a volumetric
percentage ranging from about eighty-five percent to about
ninety-five percent, while the binder material 334 occupies a
volumetric percentage ranging from about five percent to about
fifteen percent. In certain exemplary embodiments, the diamond
powder 336 undergoes a powder cleaning process that is known to
people having ordinary skill in the art. The pre-sintered PCD
cutting table 300 is treated in an HPHT system, or press, which
delivers the proper amount of pressure and temperature for the
diamond sintering process. The delivered pressure is about seventy
kilobars or greater, and the temperature is about 1600 degrees
Celsius or greater. However, in other exemplary embodiments, the
delivered pressure is about sixty kilobars or greater, and the
temperature is about 1500 degrees Celsius or greater.
[0030] According to some exemplary embodiments, the diamond
sintering process occurs entirely in the solid phase, which is
referred to as a solid phase sintering process. In some exemplary
embodiments, however, a transient liquid phase is formed during a
small time portion of the sintering process, but is then
transformed entirely into the solid phase where the sintering
process continues. When a transient liquid phase is formed during
the sintering process, the process is referred to as a near solid
phase sintering process. The transient liquid phase forms about 0.1
percent or less of the volume during the sintering process. This
small time portion of the sintering process where the transient
liquid phase exists is about ten percent or less of the total
sintering time. In some exemplary embodiments, this small time
portion of the sintering process where the transient liquid phase
exists is about eight percent or less of the total sintering time.
In some exemplary embodiments, this small time portion of the
sintering process where the transient liquid phase exists is about
six percent or less of the total sintering time. In some exemplary
embodiments, this small time portion of the sintering process where
the transient liquid phase exists is about four percent or less of
the total sintering time. This transient liquid phase forms in some
exemplary embodiments within a narrow concentration range and is
due to the concentration changes occurring between the carbon and
the metal during the sintering, or diffusion, process, which is
explained in further detail with respect to FIGS. 4 and 5.
[0031] Once the sintering process on the pre-sintered PCD cutting
table 300 is completed, the PCD cutting table 350 is formed. The
PCD cutting table 350 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
350 includes a diamond lattice 386, which is formed from the
diamond powder 336, and a modified binder material 384 deposited
within the interstitial spaces formed within the diamond lattice
386. The modified binder material 384 is similar to the binder
material 334, except that substantially all the metals have been
transformed into its respective carbides. According to some
exemplary embodiments, a bevel (not shown) is formed around the
circumference of the PCD cutting table 350. Depending upon the
exemplary embodiment, the PCD cutting table 350 is used for cutting
a hard material by either using it independently, coupling a
portion of the PCD cutting table 350 to a tool, or coupling the
opposing surface 374 to a substrate (not shown).
[0032] Within the PCD cutting table 350, there are substantially no
free metals that remain present since the metals have completely
reacted with the carbon diffusing from the diamond powder. Hence,
more carbides are formed within the PCD cutting table 350 until the
stoichiometric composition is reached. There are no eutectic or
close to eutectic catalyst metal that remains within the PCD
cutting table 350, which thereby increases the thermal stability of
the PCD cutting table 350.
[0033] FIG. 4 is a phase diagram of carbon and Element M 400 in
accordance with an exemplary embodiment of the present invention.
Although phase diagram of carbon and Element M 400 is provided as
an example of a binary phase diagram according to one exemplary
embodiment, different phase diagrams of carbon and one or more
other elements, such as Titanium, Chromium, or Tungsten, can be
used for illustrating the solid phase sintering process or near
solid phase sintering process. Element M is a metal capable of
forming a carbide. Referring to FIG. 4, the phase diagram of carbon
and Element M 400 includes a composition axis 410, a temperature
axis 420, a liquidus line 434, a solidus line 436, and a eutectic
point 438.
[0034] The composition axis 410 is positioned on the x-axis and
represents the composition of the PCD cutting table. The
composition is measured in atomic weight percent of carbon.
Proceeding from left to right along the composition axis 410, the
percentage composition of carbon increases. Thus, at the extreme
left of the composition axis 410, the material is one hundred
percent Element M. Conversely, at the extreme right of the
composition axis 410, the material is one hundred percent carbon,
or diamond. The composition axis 410 includes a eutectic
composition 440 (Ce), which is discussed in further detail
below.
[0035] The temperature axis 420 is positioned on the y-axis and
represents the various temperatures that can be subjected on the
carbon and Element M composition. The temperature is measured in
degrees Celsius. Proceeding from top to bottom along the
temperature axis 420, the temperature decreases. The temperature
axis 420 includes an Element M melting temperature 432, a diamond
melting temperature 430, and a eutectic melting temperature 439,
which is discussed in further detail below. The Element M melting
temperature 432 is the temperature at which a material having one
hundred percent Element M melts. The diamond melting temperature
430 is the temperature at which a material having one hundred
percent diamond melts.
[0036] The phase diagram of carbon and Element M 400 provides
information on different phases of the carbon and Element M
compositions and under what compositions and temperatures these
different phases exist. These phases include the total liquid phase
450 ("L"), the metal and metal carbide solid phase 452
(".alpha.+MC"), a metal slurry phase 454 (".alpha.+L"), a metal
carbide slurry phase 456 ("L+MC"), a metal solid phase 458
(".alpha."), a metal carbide solid phase 460 ("MC"), a metal
carbide and diamond solid phase 462 ("MC+D"), and a diamond slurry
phase 464 ("L+D"). The total liquid phase 450 occurs when both
carbon and Element M are both completely in the liquid phase. The
metal and metal carbide solid phase 452 occurs when both metal
carbide and Element M are both completely in the solid phase. Thus,
the carbon is all bonded with the metal to form a carbide and there
is no free solid carbon. The metal slurry phase 454 occurs when the
material has Element M crystals that is suspended in a slurry which
also includes liquid Element M. The metal carbide slurry phase 456
occurs when the material has metal carbide crystals that is
suspended in a slurry which also includes liquid metal carbide. The
metal solid phase 458 occurs when all the Element M is in solid
phase and some solid metal carbide is mixed with the solid Element
M. The metal carbide solid phase 460 occurs when all the metal
carbide is in solid phase and some solid metal is mixed with the
solid metal carbide. The metal carbide and diamond solid phase 462
occurs when the material has formed diamond in the solid phase and
some of the metal carbide also is in the solid phase. The diamond
slurry phase 464 occurs when the material has diamond crystals that
is suspended in a slurry which also includes liquid carbon.
[0037] The liquidus line 434 extends from the Element M melting
temperature 432 to a eutectic point 438 and then to the diamond
melting temperature 430. The liquidus line 434 represents the
temperature at which the composition completely melts and forms a
liquid. Thus, at temperatures above the liquidus line 434, the
composition is completely liquid. The solidus line 436 is
positioned below the liquidus line 434, except for at the eutectic
point 438. The solidus line 436 represents the temperature at which
the composition begins to melt. Thus, at temperatures below the
solidus line 436, the composition is completely solid for one or
more compounds within the material. At the eutectic point 438, the
liquidus line 434 meets with the solidus line 436. The eutectic
point 438 is defined on the phase diagram 400 as the intersection
of the eutectic temperature 439 and the eutectic composition 440.
The eutectic composition 440 is the composition where the
carbon-Element M mixture behaves as a single chemical composition
and has a melting point where the total solid phase 452 turns into
a total liquid phase 450 at a single temperature.
[0038] According to one example for forming the PCD cutting table
350 (FIG. 3) in a solid phase sintering process, the sintering
process is performed with an initial mixture composition 480
(X.sub.0). The temperature of the initial mixture composition 480
is raised to a temperature of T.sub.1 486, which forms a first
mixture point 490. The initial mixture composition 480 is at the
metal and metal carbide solid phase 452 when the initial mixture
composition 480 is at T.sub.1 486. Hence, the metal and the metal
carbides are both entirely solid. As the sintering process
continues and the temperature is held relatively constant, the
carbon atoms diffuse into the metal, which is Element M according
to the phase diagram 400, and the metal atoms diffuse into the
carbon. Each of these diffusion rates are different and result in
altering the composition of the mixture during the sintering
process. The composition of Element M within the mixture decreases
and the composition of carbon increases according to some exemplary
embodiments. Even though the temperature is maintained as
substantially constant, the composition of the mixture changes from
the initial mixture composition 480 to an intermediate mixture
composition 482 (X.sub.1). Thus, the mixture proceeds from the
first mixture point 490 to a second mixture point 492, which is in
the metal carbide solid phase 460. If the sintering process was
allowed to continue for infinite time duration, the mixture
composition with respect to Element M would further decrease, while
the mixture composition with respect to carbon would further
increase. Thus, the mixture composition proceeds from the
intermediate mixture composition 482 to a final mixture composition
484 (X.sub.2), and the second mixture point 492 proceeds to a third
mixture point 494. The third mixture point 494 is in the metal
carbide and diamond solid phase 462. However, in actuality, the
sintering process does not proceed for an infinite time duration
and thus the final composition of the mixture after completion of
the solid phase sintering process lies at a point between the
intermediate mixture composition 482 and the final mixture
composition 484. Thus, as seen in this exemplary embodiment, the
sintering process is a solid phase sintering process where no
liquid or transient liquid phase is formed. In the solid phase
sintering process, the pressures within the press are typically
higher than the pressures used in the prior art.
[0039] According to one example for forming the PCD cutting table
350 (FIG. 3) in a near solid phase sintering process, the sintering
process also is performed with the initial mixture composition 480.
However, the temperature of the initial mixture composition 480 is
raised to a temperature of T.sub.2 488, which forms an initial
mixture point 496. The initial mixture point 496 is in the metal
carbide slurry phase 456. Thus, the initial mixture composition 480
is transformed from a solid phase into a transient liquid phase, or
temporary liquid phase, during this temperature rise to T.sub.2
488. As the sintering process continues, the carbon atoms diffuse
into the metal, which is Element M according to the phase diagram
400, and the metal atoms diffuse into the carbon. Each of these
diffusion rates are different and result in altering the
composition of the mixture during the sintering process. The
composition of Element M within the mixture decreases and the
composition of carbon increases according to some exemplary
embodiments. Even though the temperature is maintained as
substantially constant, the composition of the mixture changes from
the initial mixture composition 480 to the intermediate mixture
composition 482. Thus, the mixture proceeds from the initial
mixture point 496 to a secondary mixture point 497, which is in the
metal carbide solid phase 460. Thus the transient liquid phase
disappears and the mixture is now solid. If the sintering process
was allowed to continue for an infinite time duration, the mixture
composition with respect to Element M would further decrease, while
the mixture composition with respect to carbon would further
increase. Thus, the mixture composition proceeds from the
intermediate mixture composition 482 to a final mixture composition
484, and the secondary mixture point 497 proceeds to an end mixture
point 498. The end mixture point 498 is in the metal carbide and
diamond solid phase 462. However, in actuality, the sintering
process does not proceed for an infinite time duration and thus the
final composition of the mixture after completion of the near solid
phase sintering process lies at a point between the intermediate
mixture composition 482 and the final mixture composition 484.
Thus, as seen in this exemplary embodiment, the sintering process
is a near solid phase sintering process where a transient, or
temporary, liquid phase is formed. In the near solid phase
sintering process, the pressures within the press are typically
higher than the pressures used in the prior art.
[0040] FIG. 5 is a schematic microscopic view of a diffusion
process 500 occurring between two solid elements 510 and 520 in
accordance with an exemplary embodiment of the present invention.
Referring to FIG. 5, the diffusion process includes a first solid
element 510 adjacent a second solid element 520. According to an
exemplary embodiment, the first solid element 510 is a solid
carbon; however, other solid elements can be used in lieu of the
solid carbon without departing from the scope and spirit of the
exemplary embodiment. The second solid element 520 is a solid
Element M, which is a metal capable of forming a carbide.
[0041] The solid carbon 510 includes carbon atoms 512, which are
represented in FIG. 5 as squares. The solid Element M 520 includes
Element M atoms 522, which are represented in FIG. 5 as circles.
During the diffusion process, some carbon atoms 512 diffuse into
solid Element M 520 and tum into migrated carbon atoms 514.
Similarly, during the diffusion process, some Element M atoms 522
diffuse into solid carbon 510 and tum into migrated Element M atoms
524. The rate in which Element M atoms 522 diffuse into the solid
carbon 510 is different than the rate in which carbon atoms 512
diffuse into solid Element M 520 according to some exemplary
embodiments. As seen in FIG. 5, there are five migrated carbon
atoms 514, while there are three migrated Element M atoms 524.
Thus, the composition of the mixture during the sintering process
changes as previously mentioned with respect to FIGS. 3 and 4.
[0042] FIG. 6A is a side view of a pre-sintered PDC cutter 600 in
accordance with an exemplary embodiment of the present invention.
FIG. 6B is a side view of a PDC cutter 650 formed from sintering
the pre-sintered PDC cutter 600 of FIG. 6A in accordance with an
exemplary embodiment of the present invention. FIGS. 6A and 6B
provide one example for forming the PDC cutter 650. Referring to
FIGS. 6A and 6B, the pre-sintered PDC cutter 600 includes a
substrate layer 610, a PCD cutting table layer 620, and a metal
divider 640, while the PDC cutter 650 includes a substrate 660, a
PCD cutting table 670, and a divider 690. The substrate layer 610
is positioned at the bottom of the pre-sintered PDC cutter 600 and
forms the substrate 660 upon completion of the sintering process.
The metal divider 640 is positioned atop the substrate layer 610
and forms the divider 690 upon completion of the sintering process.
The PCD cutting table layer 620 is positioned atop the metal
divider 640 and forms the PCD cutting table 670 upon completion of
the sintering process. Thus, the metal divider 640 is positioned
between the PCD cutting table layer 620 and the substrate layer 610
and prevents components from the substrate layer 610 migrating into
the PCD cutting table layer 620 during the sintering process.
[0043] The substrate layer 610 is formed from a mixture of a
substrate powder 632 and a first binder material 634 The substrate
powder 632 is tungsten carbide powder; however, the substrate
powder 632 is formed from other suitable materials 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 first binder material 634 is any
material capable of behaving as a binder for the substrate powder
610. Some examples of the first binder material 634 include, but
are not limited to, cobalt, nickel chrome, and iron. Once subjected
to high pressure and high temperature conditions, the substrate
layer 610 forms the substrate 660. The first binder material 634
melts and facilitates the sintering of the substrate layer 610. The
substrate layer 610 includes a top layer surface 612, a bottom
layer surface 614, and a substrate layer outer wall 616 that
extends from the circumference of the top layer surface 612 to the
circumference of the bottom layer surface 614. The first binder
material 634 is interspersed within the substrate 660 after
completion of the sintering process. The substrate layer 610 is
formed into a right circular cylindrical shape according to one
exemplary embodiment, but can be formed into other geometric or
non-geometric shapes.
[0044] The PCD cutting table layer 620 is formed from a mixture of
a diamond powder 636 and a second binder material 638. Although
diamond powder 636 is used to form the PCD cutting table layer 620,
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 second binder material 638 is similar
to the binder material 334 (FIG. 3A) and includes the several
different exemplary embodiments that have previously been described
with reference to the binder material 334 (FIG. 3A). Once subjected
to high pressure and high temperature conditions, the PCD cutting
table layer 620 forms the PCD cutting table 670 in a similar manner
as the sintering process which occurs when transforming the
pre-sintered PCD cutting table 300 (FIG. 3A) into the PCD cutting
table 350 (FIG. 3B). Hence the sintering process occurring within
the PCD cutting table layer 620 is a solid phase sintering process
or a near solid phase sintering process, wherein a transient liquid
phase is formed temporarily. The PCD cutting table layer 620
includes a cutting layer surface 622, an opposing layer surface
624, and a PCD cutting table layer outer wall 626 that extends from
the circumference of the cutting layer surface 622 to the
circumference of the opposing layer surface 624. According to some
exemplary embodiments, a bevel (not shown) is formed around the
circumference of the PCD cutting table layer 620.
[0045] The metal divider 640 is positioned between the substrate
layer 610 and the PCD cutting table layer 620. The metal divider
640 is fabricated from a metal or alloy capable of bonding itself
to both the PCD cutting table layer 620 and the substrate layer 610
upon completion of the sintering process. Additionally, the metal
divider 640 prevents the first binder material 634 that is located
within the substrate layer 610 from migrating into the PCD cutting
table layer 620. The metal divider 640 allows the PCD cutting table
layer 670 to be bonded indirectly to the substrate 660 thereby
forming the PDC cutter 650, while ensuring that the sintering
process that forms the PCD cutting table 670 occurs as a solid
phase sintering process or a near solid phase sintering process.
According to some exemplary embodiments, the metal divider 640 is
formed from the same metals or alloys using the same metals as used
within the second binder material 638. For example, if the second
binder material 638 includes molybdenum and/or molybdenum carbide,
the metal divider 640 also is fabricated using molybdenum or a
molybdenum alloy. According to some exemplary embodiments, the
metal divider 640 is a thin disc. Alternatively, the metal divider
640 is formed using conventional chemical vapor deposition (CVD)
techniques, plasma vapor deposition (PVD) techniques, or any other
techniques known to people having ordinary skill in the art.
Although the metal divider 640 is used as one example for
preventing the first binder material 634 from migrating into the
PCD cutting table layer 620 during the sintering process, other
methods or devices known to people having ordinary skill in the art
can be used for achieving the same or similar effects without
departing from the scope and spirit of the exemplary
embodiments.
[0046] Once the pre-sintered PDC cutter 600 is formed, the
pre-sintered PDC cutter 600 is treated in a high pressure and high
temperature system, or press, which delivers the proper amount of
pressure and temperature for the sintering process. The delivered
pressure is about seventy kilobars or greater, and the temperature
is about 1600 degrees Celsius or greater. However, in other
exemplary embodiments, the delivered pressure is about sixty
kilobars or greater, and the temperature is about 1500 degrees
Celsius or greater.
[0047] Within the substrate layer 610, the first binder material
634 liquefies and facilitates the sintering of the substrate powder
610 to form the substrate 660. The liquefied first binder material
634 does not migrate into the PCD cutting table layer 620. Within
the PCD cutting table layer 620, the diamond powder 636 is sintered
with the second binder material 638. The sintering process within
the PCD cutting table layer 620 occurs in the solid phase or near
solid phase. The diamond powder 636 forms a diamond lattice 686 and
the second binder material 638 forms a modified second binder
material 688 which is deposited within interstitial spaces that are
formed within the diamond lattice 686. The modified second binder
material 688 is similar to the modified binder material 384 (FIG.
3B) and provides toughness and thermal stability to the PCD cutting
table 670. Within the metal divider 640, the carbon atoms from the
PCD cutting table layer 620 reacts with the metal within the metal
divider 640 to form metal carbides, and hence form strong bonds
between the divider 690 and the PCD cutting table 670. Similarly,
within the metal divider 640, the carbon atoms from the substrate
layer 610 reacts with the metal within the metal divider 640 to
form metal carbides, and hence form strong bonds between the
divider 690 and the substrate 660.
[0048] The PDC cutter 650 is formed once the substrate 660, the PCD
cutting layer 670, and the divider 690 are completely formed and
the divider 690 is bonded to both the substrate 660 and the PCD
cutting layer 670. The substrate 660 includes a top surface 662, a
bottom surface 664, and a substrate outer wall 666 that extends
from the circumference of the top surface 662 to the circumference
of the bottom surface 664. The substrate 660 includes cemented
substrate powder 682 and the first binder material 634 interspersed
therein. The substrate 660 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 in which the PDC cutter 650 is to be used.
[0049] The PCD cutting table 670 includes a cutting surface 672, an
opposing surface 674, and a PCD cutting table outer wall 676 that
extends from the circumference of the cutting surface 672 to the
circumference of the opposing surface 674. The PCD cutting table
670 includes the diamond lattice 686 and the modified second binder
material 688 deposited within the interstitial spaces formed within
the diamond lattice 686. The modified second binder material 688
has been slightly modified when compared to the second binder
material 638. The free metal within the second binder material 638,
which was present before the sintering process, has reacted with
carbon to form more carbides. Thus, within the PCD cutting table
670, there are substantially no free metals that remain present
since the metals have completely reacted with the carbon diffusing
from the diamond powder. Hence, more carbides are formed within the
PCD cutting table 670 until the stoichiometric composition is
reached. There are no eutectic or close to eutectic catalyst metal
that remains within the PCD cutting table 670, thereby increasing
the thermal stability of the PCD cutting table 670,
[0050] The divider 690 is formed from the metal divider 640 and is
bonded to the opposing surface 674 of the PCD cutting table 670 and
to the top surface 662 of the substrate 660. The divider 690
includes at least some metal carbides therein. According to some
exemplary embodiments, the divider 690 includes metals and/or metal
alloys, along with their respective carbides. According to other
exemplary embodiments, the divider 690 is formed entirely from
carbides.
[0051] The PCD cutting table 670 is indirectly bonded to the
substrate 660 using the divider 690 according to methods known to
people having ordinary skill in the art. In one example, the PDC
cutter 650 is formed by independently forming the PCD cutting table
670 and the substrate 660, and thereafter placing the metal divider
640 between the PCD cutting table 670 and the substrate 660 and
bonding the PCD cutting table 670 to the divider 690 and bonding
the substrate 660 to the divider 690. In another example, the
substrate 660 is initially formed and the metal divider 640 is
placed atop the substrate 660 and the PCD cutting table layer 620
is placed atop the metal divider 640. The substrate 660, the metal
divider 640, and the PCD cutting table layer 620 are then sintered
under high pressure and high temperature conditions to form the PDC
cutter 650.
[0052] In one exemplary embodiment, upon coupling the PCD cutting
table 670 to the substrate 660, the cutting surface 672 of the PCD
cutting table 670 is substantially parallel to the bottom surface
664 of the substrate 660. Additionally, the PDC cutter 650 has been
illustrated as having a right circular cylindrical shape; however,
the PDC cutter 650 is shaped into other geometric or non-geometric
shapes in other exemplary embodiments. In certain exemplary
embodiments, the opposing surface 674 and the top surface 662 are
substantially planar; however, the opposing surface 674 and the top
surface 662 can be non-planar in other exemplary embodiments.
[0053] 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.
* * * * *