U.S. patent application number 13/671019 was filed with the patent office on 2013-03-28 for methods of forming thermally stable polycrystalline diamond cutters.
The applicant listed for this patent is Yuelin Shen, Youhe Zhang. Invention is credited to Yuelin Shen, Youhe Zhang.
Application Number | 20130074420 13/671019 |
Document ID | / |
Family ID | 41551035 |
Filed Date | 2013-03-28 |
United States Patent
Application |
20130074420 |
Kind Code |
A1 |
Zhang; Youhe ; et
al. |
March 28, 2013 |
METHODS OF FORMING THERMALLY STABLE POLYCRYSTALLINE DIAMOND
CUTTERS
Abstract
A method for forming a thermally stable cutting element that
includes forming at least one acid infusion pathway in a
polycrystalline abrasive body containing a catalyzing material to
be leached; and contacting at least a portion of the at least one
acid infusion pathway in the polycrystalline abrasive body with a
leaching agent is disclosed.
Inventors: |
Zhang; Youhe; (Spring,
TX) ; Shen; Yuelin; (Spring, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zhang; Youhe
Shen; Yuelin |
Spring
Spring |
TX
TX |
US
US |
|
|
Family ID: |
41551035 |
Appl. No.: |
13/671019 |
Filed: |
November 7, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12505316 |
Jul 17, 2009 |
8328891 |
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13671019 |
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11745726 |
May 8, 2007 |
8066087 |
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12505316 |
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60799104 |
May 9, 2006 |
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61081626 |
Jul 17, 2008 |
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Current U.S.
Class: |
51/297 ; 51/307;
51/309 |
Current CPC
Class: |
C22C 26/00 20130101;
B24D 3/06 20130101; B22F 2003/244 20130101; E21B 10/5735
20130101 |
Class at
Publication: |
51/297 ; 51/307;
51/309 |
International
Class: |
B24D 3/06 20060101
B24D003/06 |
Claims
1.-18. (canceled)
19. A method for foil ling a then tally stable cutting element,
comprising: forming a polycrystalline diamond compact of a
polycrystalline diamond body attached to a substrate comprising:
placing a mixture of diamond particles and a catalyst material
adjacent a substrate; and subjecting the mixture and substrate to
high-pressure/high temperature conditions; detaching the
polycrystalline diamond body from the substrate; forming at least
one cavity in the detached polycrystalline diamond body; and
contacting the detached polycrystalline diamond body with a
leaching agent.
20. The method of claim 19, further comprising: re-attaching the
polycrystalline diamond body to a substrate.
21. The method of claim 20, further comprising: contacting an upper
surface of the polycrystalline diamond body attached to the
substrate to a leaching agent.
22. The method of claim 19, further comprising: filling at least a
portion of the at least one cavity with an intermediate material;
placing the polycrystalline diamond body adjacent a substrate
material; and subjecting the polycrystalline diamond body and
substrate material to high temperature/high pressure
conditions.
23. The method of claim 19, wherein the cavity comprises a channel
extending through an entire thickness of the polycrystalline
abrasive body.
24. The method of claim 10, wherein the cavity extends a partial
thickness into the polycrystalline abrasive body.
25. The method of claim 19, wherein the cavity has an opening with
at least one dimension of less than 1 mm.
26. The method of claim 25, wherein the cavity has an opening with
a diameter between about 10 microns and 1 millimeter.
27. The method of claim 19, wherein the forming occurs by at least
one of machining, laser cutting, and etching.
28. A thermally stable cutting element, comprising: a
polycrystalline abrasive body having at least one cavity formed in
an interior portion of a working surface of the polycrystalline
abrasive body.
29. The thermally stable cutting of claim 28, further comprising: a
substrate attached to a surface opposite the working surface of the
polycrystalline abrasive body.
30. The thermally stable cutting element of claim 28, wherein the
polycrystalline abrasive body comprises at least one of
polycrystalline diamond, polycrystalline diamond having at least a
portion of catalyzing material removed therefrom, and
polycrystalline cubic boron nitride.
31. The thermally stable cutting element of claim 28, wherein the
cavity comprises a channel extending through an entire thickness of
the polycrystalline abrasive body.
32. The thermally stable cutting element of claim 28, wherein the
cavity extends a partial thickness into the polycrystalline
abrasive body.
33. The thermally stable cutting element of claim 28, wherein the
cavity has an opening with at least one dimension of less than 1
mm.
34. The thermally stable cutting element of claim 33, wherein the
cavity has an opening with at least one dimension of less than 50
microns.
35. A method for forming a thermally stable cutting element,
comprising: forming at least one acid infusion pathway in a
polycrystalline abrasive body containing a catalyzing material to
be leached, wherein the step of forming comprises: removing
polycrystalline abrasive material from a surface of the
polycrystalline abrasive body; contacting at least a portion of the
at least one acid infusion pathway in the polycrystalline abrasive
body with a leaching agent; and attaching the surface of the
leached polycrystalline abrasive body to a substrate by subjecting
the polycrystalline abrasive body and the substrate to high
pressure/high temperature sintering conditions to form a non-planar
locking interface therebetween, wherein the substrate locks with
the at least one acid infusion pathway of the polycrystalline
abrasive body upon attachment.
36. The method of claim 35, wherein the acid infusion pathway has
an opening with at least one dimension of less than 3 mm.
37. A method for forming a thermally stable cutting element,
comprising: forming at least one acid infusion pathway in a
polycrystalline abrasive body containing a catalyzing material to
be leached, wherein the at least one acid infusion pathway has a
diameter of less than 100 nanometers; and contacting at least a
portion of the at least one acid infusion pathway in the
polycrystalline abrasive body with a leaching agent.
38. The method of claim 37, further comprising: attaching the
polycrystalline abrasive body to an upper surface of a
substrate.
39. The method of claim 38, wherein the step of attaching comprises
subjecting the polycrystalline abrasive body and the substrate to
high pressure/high temperature sintering conditions.
40. The method of claim 38, wherein the substrate has a non-planar,
non-mating upper surface.
41. The method of claim 38, wherein the substrate has a
substantially planar upper surface.
42. The method of claim 37, wherein the at least one acid infusion
pathway is formed by incorporation of a metal, cermet, or ceramic
fiber into the polycrystalline abrasive body to form a material
structure through which a leaching agent may more easily diffuse as
compared to the polycrystalline abrasive body material.
43. The method of claim 37, wherein the at least one acid infusion
pathway is formed by incorporation of at least one discrete region
into the polycrystalline abrasive body, and wherein the at least
one discrete region is removed from the polycrystalline abrasive
body chemically, prior to leaching.
44. The method of claim 37, wherein the at least one acid infusion
pathway is formed by incorporation of at least one discrete region
into the polycrystalline abrasive body, and wherein the at least
one discrete region is removed from the polycrystalline abrasive
body chemically, during leaching.
45. A method for forming a thermally stable polycrystalline diamond
body, comprising: incorporating a filler material into a diamond
mixture; subjecting the filler material and the diamond mixture to
a high pressure/high temperature sintering process to form a
polycrystalline diamond body comprising a discrete region; wherein
the discrete region comprises the filler material and has a
material microstructure distinct from the remaining polycrystalline
diamond body; and contacting at least a portion of the
polycrystalline diamond body with a leaching agent.
46. The method of claim 45, wherein the step of contacting removes
at least a portion of the discrete region.
47. The method of claim 45, wherein the filler material comprises
at least one material selected from the group consisting of a metal
and a ceramic.
48. The method of claim 47, wherein the filler material comprises
tungsten carbide.
49. The method of claim 45, further comprising attaching the
surface of the leached polycrystalline diamond body to an upper
surface of a substrate.
50. The method of claim 49, wherein the step of attaching comprises
subjecting the polycrystalline diamond body and the substrate to
high pressure/high temperature sintering conditions.
51. The method of claim 49, wherein the substrate has a non-planar,
non-mating upper surface.
52. The method of claim 49, wherein the substrate has a
substantially planar upper surface.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of, and claiming
priority under 35 U.S.C. .sctn.120 to, U.S. patent application Ser.
No. 11/745,726, filed on May 8, 2007, which claims priority under
35 U.S.C. .sctn.119 to U.S. Patent Application No. 60/799,104,
filed on May 9, 2006. This application also claims priority under
35 U.S.C. .sctn.119 to U.S. Patent Application No. 61/081,626,
filed on Jul. 17, 2008. All of these applications are incorporated
by reference in their entirety.
BACKGROUND OF INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates generally to polycrystalline diamond
composites and cutting structures. More particularly, this
invention relates to polycrystalline diamond cutting structures
that have a high thermal stability.
[0004] 2. Background Art
[0005] Polycrystalline diamond compact ("PDC") cutters have been
used in industrial applications including rock drilling and metal
machining for many years. In a typical application, a compact of
polycrystalline diamond (PCD) (or other superhard material) is
bonded to a substrate material, which is typically a sintered
metal-carbide to form a cutting structure. PCD comprises a
polycrystalline mass of diamonds (typically synthetic) that are
bonded together to form an integral, tough, high-strength mass or
lattice. The resulting PCD structure produces enhanced properties
of wear resistance and hardness, making PCD materials extremely
useful in aggressive wear and cutting applications where high
levels of wear resistance and hardness are desired.
[0006] A PDC cutter may be formed by placing a cemented carbide
substrate into the container of a press. A mixture of diamond
grains or diamond grains and catalyst binder is placed atop the
substrate and treated under high pressure, high temperature
conditions. In doing so, metal binder (often cobalt) migrates from
the substrate and passes through the diamond grains to promote
intergrowth between the diamond grains. As a result, the diamond
grains become bonded to each other to form the diamond layer, and
the diamond layer is in turn bonded to the substrate. The substrate
often comprises a metal-carbide composite material, such as
tungsten carbide. The deposited diamond layer is often referred to
as the "diamond table" or "abrasive layer."
[0007] Conventional PCD includes 85-95% by volume diamond and a
balance of the binder material, which is present in PCD within the
interstices existing between the bonded diamond grains. Binder
materials that are typically used in forming PCD include Group VIII
elements, with cobalt (Co) being the most common binder material
used.
[0008] An example of a drag bit for earth formation drilling using
PDC cutters is shown in FIG. 1. FIG. 1 shows a rotary drill bit 10
having a bit body 12. The lower face of the bit body 12 is formed
with a plurality of blades 14, which extend generally outwardly
away from a central longitudinal axis of rotation 16 of the drill
bit. A plurality of PDC cutters 18 are disposed side by side along
the length of each blade. The number of PDC cutters 18 carried by
each blade may vary. The PDC cutters 18 are individually brazed to
a stud-like carrier (or substrate), which may be formed from
tungsten carbide, and are received and secured within sockets in
the respective blade.
[0009] A significant factor in determining the longevity of PDC
cutters is the generation of heat at the cutter contact point,
specifically at the exposed part of the PDC layer, caused by
friction between the PCD and the work material. This heat causes
thermal damage to the PCD in the faun of cracks (due to differences
in thermal expansion coefficients) which lead to spalling of the
polycrystalline diamond layer, delamination between the
polycrystalline diamond and substrate, and back conversion of the
diamond to graphite causing rapid abrasive wear. The thermal
operating range of conventional PDC cutters is typically
700.degree. C. or less.
[0010] As mentioned, conventional polycrystalline diamond is stable
at temperatures of up to 700.degree. C., after which observed
increases in temperature may result in permanent damage to and
structural failure of polycrystalline diamond. This deterioration
in polycrystalline diamond is due to the significant difference in
the coefficient of thermal expansion of the binder material,
cobalt, as compared to diamond. Upon heating of polycrystalline
diamond, the cobalt and the diamond lattice will expand at
different rates, which may cause cracks to form in the diamond
lattice structure and result in deterioration of the
polycrystalline diamond. However, thermal fatigue does not only
occur at temperatures above 700.degree. C. Rather, the differential
expansion (between cobalt and diamond) even occurs at temperatures
as low as 300-400.degree. C., still causing thermal fatigue in the
diamond body. Further, damage to polycrystalline diamond can also
result from the loss of some diamond-to-diamond bonds (from the
initiation of a graphitization process) leading to loss of
microstructural integrity and strength loss.
[0011] In order to overcome this problem, strong acids may be used
to "leach" the cobalt from the diamond lattice structure (either a
thin volume or entire tablet) to at least reduce the damage
experienced from heating diamond-cobalt composite at different
rates upon heating. Examples of "leaching" processes can be found,
for example, in U.S. Pat. Nos. 4,288,248 and 4,104,344. Briefly, a
strong acid, typically nitric acid or combinations of several
strong acids (such as nitric and hydrofluoric acid) may be used to
treat the diamond table, removing at least a portion of the
co-catalyst from the PDC composite. By leaching out the cobalt,
thermally stable polycrystalline (TSP) diamond may be formed. In
certain embodiments, only a select portion of a diamond composite
is leached, in order to gain thermal stability without losing
impact resistance. As used herein, the term TSP includes both of
the above (i.e., partially and completely leached) compounds.
Interstitial volumes remaining after leaching may be reduced by
either furthering consolidation or by filling the volume with a
secondary material, such as by processes known in the art and
described in U.S. Pat. No. 5,127,923, which is herein incorporated
by reference in its entirety.
[0012] While leaching processes with nitric/hydrofluoric acid are
successful, they tend to be lengthy and dangerous. Further,
leaching with stronger concentrations of acid would create an
extremely hazardous working environment. Using mixtures of acids
can easily take many weeks in order to leach out the cobalt.
Additionally for higher diamond density materials (used when
greater abrasion resistance is desired), leaching of the high
density material may be extremely difficult because it is more
difficult for a leaching agent to diffuse through a diamond body
having such a low porosity that accompanies the high density.
[0013] Accordingly, there exists a continuing need for methods that
accelerate the leaching process.
SUMMARY OF INVENTION
[0014] In one aspect, embodiments disclosed herein relate to a
method for forming a thermally stable cutting element that includes
forming at least one acid infusion pathway in a polycrystalline
abrasive body containing a catalyzing material to be leached; and
contacting at least a portion of the at least one acid infusion
pathway in the polycrystalline abrasive body with a leaching
agent.
[0015] In another aspect, embodiments disclosed herein relate to a
method for forming a thermally stable cutting element that includes
forming a polycrystalline diamond compact of a polycrystalline
diamond body attached to a substrate where the formation of the
polycrystalline diamond compact includes placing a mixture of
diamond particles and a catalyst material adjacent a substrate; and
subjecting the mixture and substrate to high-pressure/high
temperature conditions; then, once the polycrystalline diamond
compact is formed, detaching the polycrystalline diamond body from
the substrate; forming at least one cavity in the detached
polycrystalline diamond body; and contacting the detached
polycrystalline diamond body with a leaching agent.
[0016] In yet another aspect, embodiments disclosed herein relate
to a thermally stable cutting element that includes a
polycrystalline abrasive body having at least one cavity formed in
an interior portion of a working surface of the polycrystalline
abrasive body.
[0017] Other aspects and advantages of the invention will be
apparent from the following description and the appended
claims.
BRIEF DESCRIPTION OF DRAWINGS
[0018] FIG. 1 is an illustration of a PDC drill bit.
[0019] FIGS. 2A-2E show cross-sectional side views of various
embodiments of the present disclosure.
[0020] FIGS. 3A-3B show top views of various embodiments of the
present disclosure.
[0021] FIGS. 4A-4E is an illustration of steps for forming a PDC
cutter in accordance with an embodiment of the present
disclosure.
DETAILED DESCRIPTION
[0022] In one aspect, embodiments disclosed herein relate to
thermally stable cutting elements and methods for decreasing the
amount of time required to leach a polycrystalline diamond body or
cutter to a desired depth. More specifically, embodiments disclosed
herein involve accelerating techniques used in conjunction with
treatments of a leaching agent to remove undesired material (such
as a catalyst) used in the manufacture of a diamond table. In
particular, the accelerating techniques that may be used in
conjunction with conventional leaching include formation of acid
infusion pathways in a polycrystalline abrasive body such as
polycrystalline diamond (PCD) to increase the access of the
leaching agent to the interior regions of the polycrystalline
body.
[0023] As used herein, the term "PCD" refers to polycrystalline
diamond that has been formed, at high pressure/high temperature
(HPHT) conditions, through the use of a solvent metal catalyst,
such as those included in Group VIII of the Periodic table. The
term "thermally stable polycrystalline diamond," as used herein,
refers to intercrystalline bonded diamond that includes a volume or
region that has been rendered substantially free of the solvent
metal catalyst used to form PCD, or the solvent metal catalyst used
to form PCD remains in the region of the diamond body but is
otherwise reacted or rendered ineffective in its ability to
adversely impact the bonded diamond at elevated temperatures as
discussed above.
[0024] Forming Polycrystalline Diamond
[0025] A polycrystalline diamond body may be formed in a
conventional manner, such as by a high pressure, high temperature
sintering of "green" particles to create intercrystalline bonding
between the particles. "Sintering" may involve a high pressure,
high temperature (HPHT) process. Examples of high pressure, high
temperature (HPHT) process can be found, for example, in U.S. Pat.
Nos. 4,694,918; 5,370,195; and 4,525,178. Briefly, to form the
polycrystalline diamond object, an unsintered mass of diamond
crystalline particles is placed within a metal enclosure of the
reaction cell of a HPHT apparatus. A suitable HPHT apparatus for
this process is described in U.S. Pat. Nos. 2,947,611; 2,941,241;
2,941,248; 3,609,818; 3,767,371; 4,289,503; 4,673,414; and
4,954,139. A metal catalyst, such as cobalt or other Group VIII
metals, may be included with the unsintered mass of crystalline
particles to promote intercrystalline diamond-to-diamond bonding.
The catalyst material may be provided in the form of powder and
mixed with the diamond grains, or may be infiltrated into the
diamond grains during HPHT sintering An exemplary minimum
temperature is about 1200.degree. C. and an exemplary minimum
pressure is about 35 kilobars. Typical processing is at a pressure
of about 45 kbar and 1300.degree. C. Those of ordinary skill will
appreciate that a variety of temperatures and pressures may be
used, and the scope of the present invention is not limited to
specifically referenced temperatures and pressures.
[0026] Diamond grains useful for forming a polycrystalline diamond
body may include any type of diamond particle, including natural or
synthetic diamond powders having a wide range of grain sizes. For
example, such diamond powders may have an average grain size in the
range from submicrometer in size to 100 micrometers, and from 1 to
80 micrometers in other embodiments. Further, one skilled in the
art would appreciate that the diamond powder may include grains
having a mono- or multi-modal distribution.
[0027] Moreover, the diamond powder used to prepare the PCD body
may be synthetic diamond powder or natural diamond powder.
Synthetic diamond powder is known to include small amounts of
solvent metal catalyst material and other materials entrained
within the diamond crystals themselves. Unlike synthetic diamond
powder, natural diamond powder does not include such solvent metal
catalyst material and other materials entrained within the diamond
crystals. It is theorized that that inclusion of materials other
than the solvent catalyst in the synthetic diamond powder can
operate to impair or limit the extent to which the resulting PCD
body can be rendered thermally stable, as these materials along
with the solvent catalyst must also be removed or otherwise
neutralized. Because natural diamond is largely devoid of these
other materials, such materials do not have to be removed from the
PCD body and a higher degree of thermal stability may thus be
obtained. Accordingly, for applications calling for a particularly
high degree of thermal stability, one skilled in the art would
appreciate that the use of natural diamond for forming the PCD body
may be preferred. The diamond grain powder, whether synthetic or
natural, may be combined with or already includes a desired amount
of catalyst material to facilitate desired intercrystalline diamond
bonding during HPHT processing. Suitable catalyst materials useful
for forming the PCD body include those solvent metals selected from
the Group VIII of the Periodic table, with cobalt (Co) being the
most common, and mixtures or alloys of two or more of these
materials. In a particular embodiment, the diamond grain powder and
catalyst material mixture may comprise 85 to 95% by volume diamond
grain powder and the remaining amount catalyst material.
Alternatively, the diamond grain powder can be used without adding
a solvent metal catalyst in applications where the solvent metal
catalyst can be provided by infiltration during HPHT processing
from the adjacent substrate or adjacent other body to be bonded to
the PCD body.
[0028] The diamond powder may be combined with the desired catalyst
material, and the reaction cell is then placed under processing
conditions sufficient to cause the intercrystalline bonding between
the diamond particles. In the event that the formation of a PCD
compact comprising a substrate bonded to the PCD body is desired, a
selected substrate is loaded into the container adjacent the
diamond powder mixture prior to HPHT processing. Additionally, in
the event that the PCD body is to be bonded to a substrate, and the
substrate includes a metal solvent catalyst, the metal solvent
catalyst needed for catalyzing intercrystalline bonding of the
diamond may be provided by infiltration, in which case it may not
be necessary to mix the diamond powder with a metal solvent
catalyst prior to HPHT processing.
[0029] In an example embodiment, the device is controlled so that
the container is subjected to a HPHT process comprising a pressure
in the range of from 4 to 7 GPa and a temperature in the range of
from about 1320 to 1600.degree. C., for a sufficient period of
time. During this HPHT process, the catalyst material in the
mixture melts and infiltrates the diamond grain powder to
facilitate intercrystalline diamond bonding. During the formation
of such intercrystalline diamond bonding, the catalyst material may
migrate into the interstitial regions within the microstructure of
the so-formed PCD body that exists between the diamond bonded
grains It should be noted that if too much additional non-diamond
material is present in the powdered mass of crystalline particles,
appreciable intercrystalline bonding is prevented during the
sintering process. Such a sintered material where appreciable
intercrystalline bonding has not occurred is not within the
definition of PCD. Following such formation of intercrystalline
bonding, a polycrystalline diamond body may be formed that has, in
one embodiment, at least about 80 percent by volume diamond, with
the remaining balance of the interstitial regions between the
diamond grains occupied by the catalyst material. In other
embodiments, such diamond content may comprise at least 85 percent
by volume of the formed diamond body, and at least 90 percent by
volume in yet another embodiment. However, one skilled in the art
would appreciate that other diamond densities (or gradients of
diamond densities) may be used in alternative embodiments. In
particular embodiments, the polycrystalline diamond bodies being
leached in accordance with the present disclosure include what is
frequently referred to in the art as "high density" polycrystalline
diamond, which refers to a diamond body having a diamond content of
at least 90 percent by volume. However, in other embodiments, the
high density polycrystalline diamond used in the method of the
present disclosure may have a density of at least 92 percent by
volume up to 97 percent by volume. One skilled in the art would
appreciate that conventionally, as diamond density increases, the
leaching time (and potential inability to effectively leach)
similarly increases.
[0030] Further, one skilled in the art would appreciate that,
frequently, a diamond layer is sintered to a carbide substrate by
placing the diamond particles on a preformed substrate in the
reaction cell and sintering. However the present disclosure is not
so limited. Rather, the polycrystalline diamond bodies treated in
accordance with the present disclosure may or may not be attached
to a substrate.
[0031] In a particular embodiment, the polycrystalline diamond body
is formed using solvent catalyst material provided as an infiltrant
from a substrate, for example, a WC--Co substrate, during the HPHT
process. In such embodiments where the polycrystalline diamond body
is formed with a substrate, it may be desirable to remove the
polycrystalline diamond portion from the substrate prior to
leaching so that leaching agents may attack the diamond body in an
unshielded manner, i.e., from all sides of the diamond body without
substantial restriction.
[0032] Further, one skilled in the art would appreciate that the
same techniques used with polycrystalline diamond may be applied to
polycrystalline cubic boron nitride (PCBN). Similar to
polycrystalline diamond, PCBN may be formed by sintering boron
nitride particles (typically CBN) via a HPHT process, similar to
those for PCD, to sinter "green" particles to create
intercrystalline bonding between the particles. CBN refers to an
internal crystal structure of boron atoms and nitrogen atoms in
which the equivalent lattice points are at the corner of each cell.
Boron nitride particles typically have a diameter of approximately
one micron and appear as a white powder. Boron nitride, when
initially formed, has a generally graphite-like, hexagonal plate
structure. When compressed at high pressures (such as 106 psi), CBN
particles will be formed with a hardness very similar to diamond,
and a stability in air at temperatures of up to 1400.degree. C.
[0033] According to one embodiment of the invention, PCBN may
include a content of boron nitride of at least 50% by volume; at
least 70% by volume in another embodiment; at least 85% by volume
in yet another embodiment. In another embodiment, the cubic boron
nitride content may range from 50 to 80 percent by volume, and from
80 to 99.9 percent by volume in yet another embodiment. The
residual content of the polycrystalline cubic boron nitride
composite may include at least one of Al, Si, and mixtures thereof,
carbides, nitrides, carbonitrides and borides of Group IVa, Va, and
VIa transition metals of the periodic table. Mixtures and solid
solutions of Al, Si, carbides, nitrides, carbonitrides and borides
of Group IVa, Va, and VIa transition metals of the periodic table
may also be included.
[0034] Accelerated Leaching
[0035] In various embodiments, a formed PCD body having a catalyst
material in the interstitial spaces between bonded diamond grains
is subjected to a leaching process in conjunction with at least one
accelerating technique, whereby the catalyst material is removed
from the PCD body. As used herein, the term "removed" refers to the
reduced presence of catalyst material in the PCD body, and is
understood to mean that a substantial portion of the catalyst
material no longer resides in the PCD body. However, one skilled in
the art would appreciate that trace amounts of catalyst material
may still remain in the microstructure of the PCD body within the
interstitial regions and/or adhered to the surface of the diamond
grains. Alternatively, rather than actually removing the catalyst
material from the PCD body or compact, the selected region of the
PCD body or compact can be rendered thermally stable by treating
the catalyst material in a manner that reduces or eliminates the
potential for the catalyst material to adversely impact the
intercrystalline bonded diamond at elevated temperatures. For
example, the catalyst material may be combined chemically with
another material to cause it to no longer act as a catalyst
material (or to have less thermal mismatch with diamond), or can be
transformed into another material that again causes it to no longer
act as a catalyst material (or to have less thermal mismatch with
diamond). Accordingly, as used herein, the terms "removing
substantially all" or "substantially free" as used in reference to
the catalyst material is intended to cover the different methods in
which the catalyst material can be treated to no longer adversely
impact the intercrystalline diamond in the PCD body or compact with
increasing temperature.
[0036] The quantity of the catalyst material remaining in the
material PCD microstructure after the PCD body has been subjected
to a leaching treatment may vary, for example, on factors such as
the treatment conditions, including treatment time. Further, one
skilled in the art would appreciate that it may be acceptable or
desired in certain applications to allow a small amount of catalyst
material to stay in the PCD body. In a particular embodiment, the
PCD body may include up to 1-2 percent by weight of the catalyst
material. However, one skilled in the art would appreciate that the
amount of residual catalyst present in a leached PCD body may
depend on the diamond density of the material, and body
thickness.
[0037] As described above, a conventional leaching process involves
the exposure of an object to be leached with a leaching agent, such
as described in U.S. Pat. No. 4,224,380, which is herein
incorporated by reference in its entirety. In select embodiments,
the leaching agent may be a weak, strong, or mixtures of acids. In
other embodiments, the leaching agent may be a caustic material
such as NaOH or KOH. Suitable acids may include, for example,
nitric acid, hydrofluoric acid, hydrochloric acid, sulfuric acid,
phosphoric acid, or perchloric acid, or combinations of these
acids. In addition, caustics, such as sodium hydroxide and
potassium hydroxide, have been used to the carbide industry to
digest metallic elements from carbide composites. In addition,
other acidic and basic leaching agents may be used as desired.
Those having ordinary skill in the art will appreciate that the
molarity of the leaching agent may be adjusted depending on the
time desired to leach, concerns about hazards, etc.
[0038] While conventional leaching techniques may require many
weeks for sufficient removal of catalyst material from a PCD body
to occur, in accordance with the present disclosure, accelerating
techniques may be applied to the leaching process to decrease the
amount of treatment time required to reach the same level of
catalyst removal. Additionally, the use of the accelerating
techniques of the present disclosure may also result in a more
effective leaching. For example, for a given diamond body leached
using conventional techniques that may have 2% of the catalyst
material left in the diamond body, the application of the
accelerative techniques of the present disclosure may result in a
reduction in the remaining catalyst material to 1% or even 0.5%.
Further, because the effectiveness/amount of metal remaining after
leaching when using conventional leaching may largely depend on the
diamond density of the given diamond body, the amount of reduction
in the remaining catalyst material may also similarly depend on the
diamond density. In a particular embodiment, the leaching of a PCD
body may be accelerated by forming acid infusion pathways in the
PCD body, so that the acid (or other leaching agent) may more
readily access the interior portions of the PCD body, leading to a
faster and cleaner leaching treatment. As used herein, the term
"acid infusion pathways" refers to any passage or structure through
which a leaching agent (often acid) flows with less resistance than
compared to an intercrystalline network of diamond grains so that
such leaching agent may more readily infuse into interior regions
of the polycrystalline diamond layer. Thus, for example, such acid
infusion pathways may include cavities formed from removal of PCD
material from the PCD body, as well as a material structure through
which a leaching agent may more easily diffuse as compared to
polycrystalline diamond, such as for example, through incorporation
of a metal, cermet, or cermic fiber into a diamond mixture such
that a metal-, cermet- or ceramic-filled channel or passageway is
formed in the PCD body. Moreover, it is also within the scope of
the present disclosure that the techniques of the present
disclosure may be combined with other accelerating techniques, such
as application of increased temperatures, pressures, ultrasound,
etc., including the techniques described in U.S. Patent Application
No. 2008/0185189, which is assigned to the present assignee and
herein incorporated by reference in its entirety.
[0039] Cavities formed by removal of PCD material may include
partial cavities (cavities extending partially into the diamond
layer) and/or through-cavities or channels (cavities extending the
entire thickness of the diamond layer). Thus, by removing such
material to form voids (reducing the distance across the thickness
of a PCD body between acid contact points and also increasing the
exposed diamond surface area into which a leaching agent may infuse
the PCD body), a leaching agent's infusion into the PCD body and
thus subsequent removal of (or reaction with) the catalyzing
material disposed in interstitial spaces between the interconnect
diamond grains may be accelerated as compared to infusion into a
conventional PCD wafer or compact. Such cavities may be formed on
any surface of the PCD body to provide greater access to the
leaching agent of the diamond; however, it may be desirable, in
some embodiments, to form the cavities on the surface of a PCD body
that will subsequently form the interface between the leached PCD
body and a substrate so that cavities may give rise to a non-planar
locking interface between the leached PCD body and the substrate.
In other embodiments, it may be desirable to form the cavities on
the top or working surface of the PCD body so that upon later use
on a bit in drilling, the cavities may help to cool the cutter.
Such cavities may be formed using any technique known in the art of
cutting diamond, including, for example, methods such as EDM, laser
micro machining, ion beam milling (also referred to as ion
bombardment etching), etc. In yet other embodiments, the cavities
may be formed by molding during the HPHT sintering process whereby
the polycrystalline diamond body is initially formed interfacing a
substrate having projections extending from an upper surface
thereof. Thus, once the diamond body is detached from the
substrate, the depressions in the diamond body may be considered
equivalent to the cavities discussed herein for purposes of
accelerating leaching.
[0040] Alternatively, the cavity may be formed by incorporation of
a discrete region of an aiding material into the diamond mixture
prior to sintering, where the aiding material may be removed by
chemical or physical methods prior to leaching, such that once
subsequently removed, cavities are present in the polycrystalline
diamond body. For example, a tungsten carbide aiding material may
be formed in the diamond body, and then subsequently removed (or at
least partially removed) by machining or other physical methods so
that a cavity remains in the diamond body to allow for accelerated
leaching. Further, aiding materials other than tungsten carbide,
such as other ceramics, may also easily be used so long as the
aiding material is removable by physical or chemical methods. Use
of such an aiding material may be desirable if the aiding material
more easily removed than cutting diamond.
[0041] In another embodiment, the acid infusion pathways may be
formed during the HPHT sintering process using a filler material to
form a discrete region in the diamond body that is not removed
prior to leaching to form a cavity, but that may present a less
resistant pathway (as compared to the surrounding interconnected
diamond network) through which a leaching agent may diffuse into
the PCD body. Specifically, in such an instance the discrete region
may be differentiated as having a material microstructure distinct
from the remaining PCD (being without or with fewer
diamond-to-diamond bonds). Depending on the type of material
selected, the leaching process may result in a void or cavity being
foamed simultaneously with the leaching. For example, if cobalt or
another metal filler is used, the leaching process may remove the
cobalt or other metal discrete region, thereby resulting in the
formation of a void or cavity in the diamond body. However, the
present disclosure is not so limited. For example, the use of a
tungsten carbide (e.g., monotungsten carbide) filler material or
other ceramics would not necessarily result in the formation of a
cavity during the leaching process, but would provide a less
resistant pathway through which the leaching agent may diffuse.
Specifically, in the case of discrete regions of tungsten carbide
being formed at the diamond surface, during the initial HPHT
sintering process (wherein the polycrystalline diamond body is
formed), the metal binder used to form the diamond layer will also
sweep through the carbide region, forming a cermet in situ. Thus,
similar to as described above, the metal binder (and potentially
some of the tungsten carbide particles) present in tungsten carbide
region may be removed by the leaching process, resulting a more
porous body, and thus a pathway through which a leaching agent may
more readily diffuse (than the surrounding polycrystalline abrasive
body). Thus, the filler material may include various ceramics,
metals, known to those skilled in the art, in various shapes (rods,
powder, etc.) and dimensions (which may be selected based the
desired pathway size, mean free path between carbide particles,
etc.). In a particular embodiment, metal fibers such as cobalt or
nickel fibers (or rods), may be used in forming the PCD body so
that the resulting body has a metal filled pathway though which a
leaching agent may more readily diffuse. In the case of some
metals, the leaching agent may actually remove the metal filling as
it contacts the PCD body, forming a cavity in situ.
[0042] Referring to FIGS. 2A-2E, various embodiments of PCD bodies
30 having acid infusion pathways 35 formed therein are shown. As
shown in FIG. 2A, acid infusion pathways 35 are through-cavities or
channels, extending the entire thickness or depth of PCD body 30,
from a top surface 31 to a bottom surface 33. In FIG. 2B, acid
infusion pathways 35 are partial cavities, extending partially from
bottom surface 33 a depth less than top surface 31. Moreover, while
FIGS. 2A and 2B show pathways 35 formed perpendicular to surfaces
31, 33, the present invention is not so limited. Rather, as shown
in FIGS. 2C and 2D, such pathways 35 may extend into or through PCD
body 30 at an angle to surfaces 31, 33. Additionally, such pathways
or cavities 35 may take any geometrical (regular or irregular)
shape or form, including for example, having a generally equal or
varying (e.g., pathway 35 may be a dimple as shown in FIGS. 2D and
2E) diameter along the length of the pathway 35. Additionally, as
shown by comparing the general representative size of the various
pathways 35 shown in FIGS. 2A-2E, pathways 35 may be selected to
have different general relative dimensions depending, for example,
on the methods by which the pathways 35 are being formed, among
other design considerations. Thus, in some embodiments, for
example, as shown in FIG. 2E, a pathway 35 may be selected to have
a generally large diameter at the intersection between the pathway
and a surface 31 or 33 of the PCD body 30, ranging as large as the
cutter diameter or one-half the diameter of the PCD body 30, or may
be smaller as illustrated shown in FIGS. 2A-2D. In particular
embodiments, the diameters of the pathways (including both
later-formed cavities as well as preformed filler- or aiding
material-filled pathways) may range from millimeter scale (up to 3
mm in some embodiments) to microscale (less than 1 mm and less than
50 microns) to nanoscale (down to 100, 50, or 10 nm in various
embodiments). In an even more particular embodiment, pathways
(including both later-formed cavities and/or preformed filler- or
aiding material-filled pathways) of diameter ranging from 10
microns to 1 mm (or to 0.5 mm in another embodiment) are formed in
the diamond body. However, one skilled in the art would appreciate
that the selected size may be based on factors such as the size of
the PCD body, degree of acceleration in leaching desired, the
techniques by which the pathways are formed, any effect on the
material and mechanical properties of the PCD body, etc. It is also
within the scope of the present disclosure that various
combinations of type, number, shape, size of pathways may be made,
such as shown in FIG. 2D.
[0043] Moreover, there is also no limit on the placement or pattern
of the pathways formed in the PCD body. For example, as shown in
FIGS. 3A and 3B, the pathways 35 may take any regular array of even
spaced pathways or form a pattern of concentric circles. However,
the pathways may also be randomly distributed across a PCD
body.
[0044] Further, as mentioned above, while the above discussion has
applied to PCD cutting elements or bodies, those having ordinary
skill in the art will appreciate that these techniques may be more
generally applied to any material that requires the leaching of a
material (such as a catalyst) from its surrounding matrix. In
particular, embodiments disclosed herein apply to "free-standing"
PCD bodies, such as, PCD wafers having no carbide substrate. Such
PCD bodies may have been formed "free-standing" or may have been
detached from a carbide substrate prior to leaching. However, in
other embodiments, the acid infusion pathways may also be formed in
PCD bodies attached to a carbide substrate. In a particular
embodiment, the PCD bodies may be at least 1 mm thick, and at least
1.5 or 2 mm thick in alternate embodiments.
[0045] Further when such "free-standing" PCD bodies are leached, in
particular embodiments, the leached PCD bodies may be attached (or
reattached) to a substrate, to facilitate attached to a bit,
cutting tool, or other end use, for example. Such methods of
reattachment may include sintering a leached PCD body with a
substrate material (either preformed or powder) in a second HPHT
sintering step, such as discussed in U.S. Patent Publication No.
2008/0223623, which is assigned to the present assignee and herein
incorporated by reference in its entirety. The HPHT sintering used
to attach a diamond body to the substrate may be performed in a
similar manner as described above with respect to formation of
polycrystalline diamond, but in particular embodiments, such
conditions may include a temperature ranging from 1350 to
1500.degree. C. and a pressure ranging from 4 to 7 GPa. When
attaching a PCD body to a substrate, the PCD body may be placed
such the surface intersecting the openings of the partial acid
infusion pathway may either be adjacent or not adjacent the
substrate. Selection between such embodiments may be based factors
such as desire for non-planar interface or desire for cooling
during drilling.
[0046] Attachment or (reattachment) of the PCD body to a substrate
may be achieved by placing the two pieces together and subjecting
the two to sintering conditions to join the two bodies together. In
embodiments in which the pathway openings are placed adjacent the
substrate upper surface, during and due to the sintering
conditions, some amount of carbide materials from the substrate may
"bulge" into the open space of the cavities which have been formed
in the PCD body, forming mechanical locking known in the art of
non-planar interfaces. Alternatively, an intermediate material,
such as a refractory powder (tungsten or tungsten carbide powder in
particular embodiments) may be used to fill at least a portion of
the cavities in the PCD, such that the intermediate material will
be sintered and bond together with the carbide substrate during the
sintering conditions. In such embodiments, the substrate may have a
substantially planar upper surface or may have a non-planar but
non-mating upper surface. In the embodiment having the non-planar,
but non-mating upper surface to the substrate, a diamond body may
have a "larger" cavity than the projections that exist on the
substrate upper surface. Thus, while the surfaces are non-mating
(defined herein as having a gap of at least 10% of at least one
dimension of the cavities between the substrate and diamond body),
the geometries would align based on location at the interface. In
another embodiment, the gap between the diamond and substrate may
be at least 25% of at least one dimension of the cavities. Further,
in such embodiments, the intermediate material may be used to fill
the gaps between the corresponding cavity and projection to aid in
the attachment process. Other intermediate materials, such as
diamond powder in combination with the refractory powder, may also
be used. Another alternative embodiment may use a carbide substrate
machined to have mating (less than 10% gap) geometrical projections
that may occupy the cavities upon placement of the two pieces
together. In such an embodiment, an intermediate material may be
used between the diamond body and the substrate to minimize any
mismatches therebetween, which may result in cracking during the
HPHT sintering. U.S. Patent Application No. 61/081,619 entitled
"Method of Forming a Polycrystalline Diamond Cutter," filed on Jul.
17, 2008, which is herein incorporated by reference in its entity,
is directed at the use of cavities in a PCD body for forming a
non-planar interface between a diamond body and a substrate.
[0047] Further, infiltrant materials present in the substrate may
infiltrate into these openings, as well as into the interstitial
regions (or at least a portion thereof) previously occupied by the
catalyzing material that has been removed by the leaching process,
as discussed in U.S. Patent Application No. 60/941,616. Such
infiltration with a variety of infiltrants or replacement materials
using any number of techniques, including liquid-phase sintering
under HPHT conditions, pressure techniques. The type of infiltrant
or replacement material is not a limitation on the scope of the
present disclosure. Rather any type of infiltrant or replacement
materials may be used, including, for example, non-refractory
metals such as copper or other Group IB metals or alloys thereof,
Group VIII metals such as cobalt, nickel, and iron, ceramics,
silicon, and silicon-containing compounds, ultra-hard materials
such as diamond and cBN. In a particular embodiment, the source of
infiltrant or replacement material may be a substrate that is
attached to the leached PCD body during an HPHT process. Substrates
useful in this regard may include those substrates that are used to
form conventional PCD, including those formed from metals,
ceramics, and/or cermet materials that contain a desired
infiltrant, such as a substrate formed from WC--Co.
[0048] Additionally, although a substrate may be attached to the
leached PCD body during the introduction of the replacement
infiltrant material, it is also understood that the substrate may
alternatively be attached to the PCD body after the desired
infiltrant has been introduced. In such an embodiment, the
infiltrant material may be introduced, for example, by an HPHT
process that does not use the substrate material as an infiltrant
source, and the desired substrate may be attached to the diamond
body by a separate HPHT process or other method, such as by
brazing, welding, or the like. Alternatively, no replacement
infiltrant may be used, and the substrate may be attached by
brazing, welding, sintering, or the like. Further, one skilled in
the art would also appreciate that, as described in U.S. Patent
Application No. 60/941,616, an intermediate material may be
attached between the PCD body and a substrate to facilitate
attachment or acting as a barrier to prevent or minimize the
migration of catalyst material within the substrate into the PCD
body.
[0049] Referring to FIGS. 4A-4E, collectively, an embodiment of the
process steps of the present disclosure is shown. As shown in FIG.
4A, a polycrystalline diamond body 30 having a catalyzing material
found in the interstitial regions between the diamond grains (as
described above) may be formed attached to a carbide substrate 34.
The polycrystalline diamond body 30 may be detached (shown in FIG.
4B) from the substrate 34 prior to formation of acid infusion
pathways 35 and treatment of the polycrystalline diamond body 30 by
leaching techniques disclosed herein. Alternatively, a
polycrystalline diamond body 30 may be formed without a substrate.
While FIG. 4C shows formation of acid infusion pathways 35 in the
polycrystalline diamond body 30 after formation of the diamond
body, alternatively, the pathways may be formed during HPHT
sintering as described above. Leaching of polycrystalline diamond
body 30 removes at least a substantial portion of the catalyzing
material from the interstitial regions, leaving a polycrystalline
diamond body 32 (shown in FIG. 4D) having voids (other than
pathways 35) dispersed in the diamond matrix or regions that were
previously occupied by catalyzing material. Further, as shown in
FIG. 4E, the polycrystalline diamond body 32 may then be attached
(or reattached) to a substrate 36 through sintering. In the
embodiment shown in FIG. 4E, the openings of pathways 35 are placed
adjacent the substrate so that after reattachment sintering, an
non-planar interface may be formed with a portion of substrate 37
filling any previously open space of pathways 35.
[0050] Following all processing and treatment steps, the cutting
elements of the present disclosure may have a polycrystalline
diamond body having diamond grains with an average grain size of
less than 20 microns, and ranging from about 9 to 15 microns in a
particular embodiment. Such average grain sizes after treatment may
be estimated by using electron backscatter diffraction of
cross-sections of multiple PCD bodies with a scanning electron
microscope, and using a mean linear intercept method.
[0051] Embodiments of the present disclosure may provide for at
least one of the following advantages. Conventional leaching
techniques, such baths may take as much as twelve weeks (for low
density diamond) or more (greater diamond density and/or thickness)
to achieve the desired removal of catalyzing material. However,
formation of acid infusion pathways in the polycrystalline diamond
body may reduce the leach time by allowing for greater access of
the leaching agents into the interior regions of the diamond body.
Additionally, if the leached PCD bodies are later attached (or
reattached) to a substrate and if the openings of the pathways are
adjacent the substrate, risk of delamination may be decreased due
to the mechanical locking which may result from carbide bulging
into the cavities or a refractory powder added to the cavities
bonding with the substrate. Conversely, advantages may also result
from having the openings lay on the ultimate working or top surface
of the formed cutter. In such embodiments, the pathways may form
cooling channels to more quickly cool the cutting edge from the
elevated temperatures experienced during drilling. By having such
pathway exposed to the top surface, drilling fluids may more
readily be brought to the contact interface to reduce friction and
frictional heat generation. Moreover, for any fluid which may fill
the cavities, the fluid may act as a coolant exposed to interior
portions of the PDC body, which may cool the PCD by convective
cooling when the temperature rises. When the temperature rises
rapidly, the fluid may vaporize and absorb a large amount of heat,
protecting the cutting edge from thermal damage.
[0052] While the invention has been described with respect to a
limited number of embodiments, those skilled in the art, having
benefit of this disclosure, will appreciate that other embodiments
can be devised which do not depart from the scope of the invention
as disclosed herein. Accordingly, the scope of the invention should
be limited only by the attached claims.
* * * * *