U.S. patent application number 11/531389 was filed with the patent office on 2007-03-15 for sintered polycrystalline diamond material with extremely fine microstructures.
Invention is credited to Ram Raghavan, Steven Webb.
Application Number | 20070056778 11/531389 |
Document ID | / |
Family ID | 37853916 |
Filed Date | 2007-03-15 |
United States Patent
Application |
20070056778 |
Kind Code |
A1 |
Webb; Steven ; et
al. |
March 15, 2007 |
SINTERED POLYCRYSTALLINE DIAMOND MATERIAL WITH EXTREMELY FINE
MICROSTRUCTURES
Abstract
A sintered polycrystalline diamond material (PCD) of extremely
fine grain size is manufactured by sintering a diamond powder with
pre-blended catalyst metal under high pressure/high temperature
(HP/HT) processing. The PCD material has an average sintered
diamond grain structure of less than 1.0 .mu.m.
Inventors: |
Webb; Steven; (Worthington,
OH) ; Raghavan; Ram; (Galena, OH) |
Correspondence
Address: |
PEPPER HAMILTON LLP
ONE MELLON CENTER, 50TH FLOOR
500 GRANT STREET
PITTSBURGH
PA
15219
US
|
Family ID: |
37853916 |
Appl. No.: |
11/531389 |
Filed: |
September 13, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60717227 |
Sep 15, 2005 |
|
|
|
Current U.S.
Class: |
175/434 |
Current CPC
Class: |
C04B 2235/95 20130101;
C04B 2235/722 20130101; C22C 26/00 20130101; B01J 2203/062
20130101; C04B 35/52 20130101; B22F 7/062 20130101; B01J 2203/0655
20130101; B01J 3/062 20130101; B22F 2005/002 20130101; C04B
2235/785 20130101; B22F 2998/00 20130101; C04B 2235/782 20130101;
B01J 2203/0685 20130101; B22F 2998/00 20130101; C04B 2235/723
20130101; C04B 2235/427 20130101; B22F 3/15 20130101 |
Class at
Publication: |
175/434 |
International
Class: |
E21B 10/36 20060101
E21B010/36 |
Claims
1. A polycrystalline diamond (PCD) body comprising diamond crystals
having an arithmetic mean, as-sintered, diamond grain size less
than 1 .mu.m.
2. The PCD body of claim 1 wherein the grain size is greater than
0.1 .mu.m.
3. The PCD body of claim 1 wherein the body has an oxygen content
below about 0.05 weight-percent.
4. The PCD body of claim 1 wherein the body has a nitrogen content
below about 0.01 weight-percent.
5. The polycrystalline diamond (PCD) body of claim 1 comprising
diamond crystals, wherein at least 63% of the crystals have a grain
size that is less than 1.0 .mu.m.
6. The polycrystalline diamond (PCD) body of claim 1, wherein the
thickness of the sintered diamond body is greater than about 0.5
mm.
7. The PCD body of claim 1 further comprising a cemented metal
carbide support.
8. A method for producing a polycrystalline diamond (PCD) body with
an arithmetic mean as-sintered grain size less than 1 .mu.m,
comprising: providing diamond particles having a volumetric mean
particle size of less than about 1.0 .mu.m and greater than about
0.1 .mu.m; blending, with the diamond particles, a catalyst metal
having an average particle size that is less than that of the
diamond grain size, to form a diamond powder blend; and processing
the diamond powder blend using a pressure and a temperature for a
time sufficient to cause intercrystalline bonding between adjacent
diamond grains.
9. The method of claim 8 wherein the catalyst metal comprises an
iron group metal.
10. The method of claim 8 wherein the metal catalyst comprises
cobalt.
11. The method of claim 8 wherein the metal catalyst comprises
about 0.5% to about 15% by weight of the diamond powder blend.
12. The method of claim 8 wherein the metal catalyst comprises
nanocrystalline particles.
13. The method of claim 12 wherein the nanocrystalline particles
are directly adhered to the diamond particles.
14. The method of claim 8 wherein the pressure is between about 20
Kbar and 70 Kbar, and wherein the temperature is at least about
1000.degree. C., and wherein the time is between about 3 minutes to
about 120 minutes.
15. The method of claim 8 further comprising processing the diamond
powder blend together with a cemented metal carbide support.
16. The method of claim 8 wherein the metal carbide support
comprises a support annulus and the diamond power blend is disposed
within the support annulus.
17. A polycrystalline diamond (PCD) wear component comprising a PCD
body comprising diamond crystals having an arithmetic mean,
as-sintered, diamond grain size between about 0.1 .mu.m and about
1.0 .mu.m.
18. The component of claim 17 wherein the PCD body is
monolithic.
19. The component of claim 17 wherein the PCD body is bonded to a
substrate.
20. The component of claim 17 wherein the substrate comprises a
cemented metal carbide.
21. The component of claim 17 wherein the cemented metal carbide
comprises cemented tungsten carbide.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application claims priority to co-pending U.S.
provisional patent application No. 60/717,227, filed Sep. 15, 2005
entitled "Sintered, Polycrystalline Diamond Compact with Extremely
Fine Microstructures", the disclosure of which is incorporated
herein by reference in its entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] Not applicable.
NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT
[0003] Not applicable.
SEQUENCE LISTING
[0004] Not applicable.
BACKGROUND
[0005] 1. Technical Field
[0006] The disclosed embodiments generally relate to the field of
sintered diamond cutting and forming tools and more particularly to
such diamond tools having extremely fine microstructures imparting
improved tool properties, machinability, and an ability to impart
improved surface finish to workpiece materials.
[0007] 2. Description of the Related Art
[0008] Polycrystalline diamond (PCD) is used extensively in
industrial applications including metal cutting wire drawing,
drilling, and as wear parts. As defined herein, PCD is a two phase
polycrystalline diamond product in which the diamond crystals are
sintered together to form a continuous diamond lattice. This
lattice, the majority phase, comprises interparticle
diamond-to-diamond bonds without interposed, non-diamond, bonding
phases. A volume of residual catalyst metal, the minor phase, may
be disposed in interstices between diamond crystals.
[0009] PCD production methods were first discovered in the 1960's
and are well described in patent literature. U.S. Pat. Nos.
3,831,428; 4,063,909; 5,488,268, the disclosures of each of which
are incorporated herein by reference, describe high pressure/high
temperature (HP/HT) methods that produce cutting tools, wire
drawing dies, and earth boring drilling cutters with resistance to
abrasive and chemical wear. Because PCD exhibits more uniform
mechanical properties than single crystal diamond and is available
in larger sizes than single crystal diamond, PCD offers substantial
design advantages over natural or synthetic single crystal diamond.
However, PCD as currently produced, does not provide extremely
smooth cut, drawn or otherwise formed workpiece surfaces. Single
crystal diamond, while expensive, anisotropic, and limited in size,
remains the preferred tool material for single point turning of
optical materials or drawing of highly finished, fine wire.
Mechanical failure, from limited strength and impact resistance, of
PCD tools is also common
[0010] Available PCD components have parts having diamond grain
sizes after HP/HT sintering ("as-sintered") of 1 .mu.m to 100
.mu.m. Finer, uniform, as-sintered diamond grain sizes, for
example, of about 0.1 .mu.m to about 1.0 .mu.m (referred to as
"submicron") have proven challenging to produce commercially using
the PCD manufacturing process described above. Submicron diamond
particles are difficult to produce, and have proven difficult to
handle during blending and mixing due to their high surface area's
ability to attract and retain contaminants that affect the
sintering process and product properties.
[0011] Submicron diamond particles have low packing densities that
cause problems during loading of shielding enclosures and HP/HT
processing. The very fine pores between the submicron diamond
grains in the initial diamond particle mass are difficult to
uniformly penetrate with catalyst metal, leading to incomplete
bonding and sintering between diamond particles. It is almost
always observed that the high surface area of submicron diamond
powders causes the diamond solution-reprecipitation process to
occur non-uniformly. This leads to non-uniform detrimental diamond
grain growth and other complications that make the production of
larger parts unfeasible when final diamond grain sizes less than 1
micron are attempted.
[0012] Prior attempts to produce submicron monolithic PCD have not
yielded product having any substantial uniformity, either as (i) a
monolithic, free-standing body, or (ii) PCD attached to a
substrate, known as supported PCD. PCD, as used herein, refers to a
sintered PCD body that is comprised of a continuous diamond matrix,
diamond to diamond bonds, with or without catalyst metal. PCD is
generally a two-phase material (diamond and catalyst), and does not
contain any significant amount of a third phase interposed between
diamond grains, such as bonding carbides, nitrides, or borides.
[0013] Non PCD diamond products containing at least some submicron
diamond grains are well known. U.S. Pat. No. 4,505,746, the
disclosure of which is incorporated herein by reference, describes
the use of 3 .mu.m and submicron diamond particles, a catalyst
metal, and additional carbide, carbonitride, nitride, and boride
phases to make a tougher, abrasion resistant sintered diamond
compact body. U.S. Pat. No. 4,303,442 to Hara et al., the
disclosure of which is incorporated herein by reference, describes
a method to sinter diamond materials for a cutting tool or wire die
in which the grain size of the diamond is less than 1 .mu.m. Hara
et al. discusses the benefits of submicron grain structure in
providing high dimensional precision and superb surface finish on
workpieces. In order for Hara et al. to produce useful sintered
diamond tools, it was necessary to add a third bonding phase of one
or more carbides, nitrides, and borides of IVB, VB, VIB group
metals (otherwise known as International Union of Pure and Applied
Chemistry (IUPAC) Group 4, Group 5, and Group 6 elements,
respectively) and an iron group catalyst metal to the submicron
diamond particles. Additionally, Hara et al. teaches the difficulty
of producing submicron PCD. Example 1 of Hara et al. shows that
submicron diamond powders with less than 5% of the bonding
additions undergo grain growth to over 300 .mu.m diameters during
HP/HT sintering. These non-uniform materials were not hard enough
to be useful as cutting tools. Neither of the patents listed above
describes the production of a submicron PCD diamond body. Both
sintered products contained a third phase beyond the diamond and
catalyst of true PCD.
[0014] U.S. Pat. No. 6,319,460, the disclosure of which is
incorporated herein by reference, describes a sintered diamond tool
with improved overall toughness achieved by reducing the grain size
of the diamond particles. In this case, the diamond particles were
surrounded by a continuous metal matrix; no intergranular diamond
bonds were formed. The product was not PCD but rather a composite
with diamond grains no finer than 1 .mu.m. The wear resistance,
strength, and thermal stability of this product will be
substantially inferior to true PCD.
[0015] U.S. Patent Application Publication 2005/0019114, filed by
Sung, the disclosure of which is incorporated herein by reference,
describes the production of nanocrystalline diamond materials,
those with grain size less than 0.1 .mu.m. This application teaches
alternative methods of sintering expensive nanocrystalline diamond
and specifically excluding submicron (0.1 .mu.m to 1 .mu.m) diamond
particles and excluding the use of a liquid metal catalyst. Because
no catalyst metal is present, the application does not describe a
true PCD product; the product will have significant defects, and
will be difficult to produce due to inherent problems of handling
fine powders.
[0016] The prior art falls short of achieving a submicron particle
size. U.S. Pat. Nos. 5,855,996 and 5,468,268, the disclosures of
which are incorporated herein by reference, describe the effect of
particle size distribution (PSD) of the PCD compact on its
performance characteristics. In this case, the submicron particles
are used as a portion of the diamond particle mass as a way to
increase diamond concentration in the sintered PCD product. 15
volume percent is the maximum fraction of submicron diamond
possible in the prior art. The micrographs in U.S. Pat. No.
5,855,996 show that far less than 15 volume percent submicron
diamond is actually present.
[0017] There remains a need to produce a monolithic PCD material
with uniform, as-sintered, diamond grains sizes below 1 .mu.m.
Applicants have surprisingly found a method to achieve several of
the advantages of submicron PCD without adding additional bonding
phases or resorting to expensive nanocrystalline diamond.
[0018] The disclosure contained herein describes attempts to
address one or more of the problems described above.
SUMMARY
[0019] In an exemplary embodiment, a polycrystalline (PCD) body has
diamond crystals that have an arithmetic mean, as-sintered diamond
grain size less than 1 .mu.m. In another embodiment, the PCD body
comprises grain sizes greater than about 0.1 .mu.m and less than
about 1.0 .mu.m. In still another embodiment the as-sintered grain
size of a PCD body is substantially uniform. In a further
embodiment, the PCD body is monolithic; there are no added bonding
phases, such as carbides, nitrides, or borides, in the PCD body. An
embodiment of a PCD body may have an oxygen content less than about
0.05 weight percent. In still another embodiment of a PCD body, the
nitrogen content is less than about 0.01 weight-percent. A PCD body
embodied herein may have diamond crystals wherein at least 63% of
the crystals have a grain size that is less than 1.0 .mu.m. Another
embodiment is a PCD body which has a mean as-sintered grain size
between about 0.1 .mu.m and 1.0 .mu.m, with a body thickness
greater than about 0.5 mm.
[0020] An embodiment includes a method for producing a
polycrystalline diamond (PCD) body an average as-sintered grain
size less than about 1.0 .mu.m by: starting with diamond particles
having a mean volumetric particle size less that about 1.0 .mu.m;
blending, with the diamond particles, a catalyst metal having an
arithmetic mean particle size that is less than that of the diamond
grain size, to form a diamond powder blend; and processing the
diamond powder blend using a pressure and a temperature for a time
sufficient to affect intercrystalline bonding between adjacent
diamond particles. In an embodiment of the method the catalyst
metal may be an iron group metal. In yet another embodiment the
catalyst metal may be cobalt. The catalyst metal may be about 0.5%
to about 15% by weight of the diamond powder blend. An embodiment
uses the catalyst metal as nanocrystals, and a further embodiment
has the catalyst metal nanocrystals adhered to the diamond
particles. The processing pressure may be between about 20 Kbar and
about 70 Kbar. The processing temperature may be at least about
1000.degree. C., and the processing time may be between about 3
minutes to about 120 minutes. In an embodiment of the method, the
processing further includes inclusion of a cemented metal carbide
support with the diamond powder blend. A further embodiment uses a
metal cemented carbide support in the shape of an annulus, with the
diamond powder blend disposed within the support annulus.
[0021] Still another embodiment includes a polycrystalline diamond
(PCD) wear component, such as, but not limited to, a machining
tool, wear pad, punch or die, comprising a PCD body that has a mean
as-sintered diamond grain size between about 0.1 .mu.m and about
1.0 .mu.m. In another embodiment of the tool, the PCD body is
monolithic. In yet another embodiment of the tool, the PCD body is
bonded to a substrate, and the substrate may be a cemented metal
carbide, such as for example, but not limited to, cemented tungsten
carbide.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a scanning electron microscope ("SEM") image of an
exemplary cobalt-diamond powder blend.
[0023] FIG. 2 describes a process of making a PCD body with average
submicron as-sintered grain size.
[0024] FIG. 3 is an SEM image of one embodiment using 0.8 .mu.m
diamond powder.
[0025] FIG. 4 is an SEM image of one embodiment using 0.5 .mu.m
diamond powder.
[0026] FIG. 5 is an SEM image of a product of the prior art.
DETAILED DESCRIPTION
[0027] Before the present methods, systems and materials are
described, it is to be understood that this disclosure is not
limited to the particular methodologies, systems and materials
described, as these may vary. It is also to be understood that the
terminology used in the description is for the purpose of
describing the particular versions or embodiments only, and is not
intended to limit the scope. For example, as used herein and in the
appended claims, the singular forms "a," "an," and "the" include
plural references unless the context clearly dictates otherwise. In
addition, the word "comprising" as used herein is intended to mean
"including but not limited to." Further, the word "HP/HT" refers to
the processing of a material at high pressures (i.e., between 25
Kbar and 75 Kbar or higher) and high temperature (i.e., about
1000.degree. C. or higher). Unless defined otherwise, all technical
and scientific terms used herein have the same meanings as commonly
understood by one of ordinary skill in the art,
[0028] In an embodiment, a body is made of submicron
polycrystalline diamond ("PCD"), that is, a liquid metal catalyzed
sintered diamond product having a sintered arithmetic mean (i.e.,
average) diamond grain size below 1 .mu.m and above 0.1 .mu.m.
Average sintered grain size was determined using the line-intercept
method. This method is based on the grain dimension determined
through the intersection of randomly drawn lines on a
microstructure photo, and is familiar to those skilled in the
art.
[0029] Using a diamond powder with pre-blended catalyst material,
such as cobalt, a method embodiment may produce high quality PCD
with average as-sintered grain sizes from 0.1 .mu.m to 1.0 .mu.m.
In another embodiment, no bonding agents such as carbides, nitrides
or borides are present in the PCD bodies. Thus, the PCD bodies
described herein comprise substantially only diamond and catalyst.
Prior PCD technology, as demonstrated in the art, was not capable
of producing as-sintered monolithic PCD with grain sizes below 1.0
.mu.m in substantial amounts.
[0030] Diamond Powder Blend. The raw material diamond particles may
be natural or HP/HT synthetic (preferably not nanocrystalline
"shock" diamond) single crystal particles or polycrystalline
aggregates with a submicron particle size, between about 0.1 .mu.m
and about 1.0 .mu.m. The raw material diamond particle size is the
volumetric mean particle size measured by a particle size analyzer
such as a Microtrac or any other suitable analyzer. In one
embodiment, the mean volumetric particle size of the diamond
particles was 0.8 .mu.m. In another embodiment the mean volumetric
particle size was 0.5 .mu.m. In a third embodiment, particles of
0.3 .mu.m mean volumetric particle size were effectively sintered.
The diamond powder blend further contained one or more pre-blended
catalyst metals such as cobalt or other iron group metals.
Preferably, the metal catalyst is pure metal or substantially pure
with only minor impurities. In particular, the catalyst was in the
form of nanocrystalline particles adhered directly to the diamond
particles made by any method known now or hereafter to one of
ordinary skill in the art. In some embodiments, the metal catalyst
may an average particle size that is less than that of the diamond
grains.
[0031] FIG. 1 shows a Scanning Electron Micrograph of the powder
raw material 100 that may be used in one embodiment. In FIG. 1, 0.8
.mu.m mean volumetric size diamond particles 110 have 100 nanometer
(nm) average size cobalt particles 120 adhered to their surfaces.
Other iron group metals could also be used. In one embodiment,
catalyst metals of 0.5% to up to 10% by weight were contained in
the raw material blend. The catalyst may be present in varying
amounts in the blend. In some embodiments, the catalyst may make up
from about 1% to about 10% of the blend by weight. In other
embodiments, the catalyst may make up from about 0.5% to about 15%
by weight of the blend. In other embodiments, the catalyst may make
up from about 5% to about 7% percent by weight of the blend.
[0032] FIGS. 2A and 2B represent a process of making a supported
submicron PCD body. FIG. 2A refers to the system before HP/HT
processing 200. FIG. 2B refers to the HP/HT processed supported
submicron PCD body 250. In an embodiment of FIG. 2A, a diamond
powder blend 210 (diamond particles with metal catalyst, described
supra) and a cemented metal carbide support 220 may be disposed in
a protective enclosure 230. The blended diamond particles 210 and
the metal carbide support 220 may be sintered simultaneously in a
single HP/HT process. In an embodiment, the metal carbide support
220 reacts only with a layer of diamond particles at the interface
240 with the metal carbide support, to adhere the resultant PCD
body to the support. The resulting product 250 is a sintered PCD
body 260 adhered to a metal carbide support 220. The PCD body 260,
comprises diamond to diamond bonds. The product 250 is subsequently
removed from the protective enclosure 230. It should be understood
that the methods described herein can be used to make a monolithic
(i.e., unsupported) structure. In such a case, the method shown in
FIGS. 2A and 2B could be used, without the support 220.
[0033] The HP/HT processing conditions selected are sufficient to
provide intercrystalline bonding between adjacent diamond grains
and, optionally, the joining of sintered diamond particles to the
cemented metal carbide support. In one embodiment, the processing
conditions generally involve the imposition for about 3 to about
120 minutes of a temperature of at least 1000.degree. C. and a
pressure of at least 20 kilobars (kbar). In another embodiment,
pressures between about 50 and about 70 kbar, and temperatures
between about 1400.degree. C. and about 1600.degree. C., may be
used. Other temperatures and pressures are possible. Pressures,
temperatures, and process duration are selected to minimize diamond
grain growth during sintering and may be now or hereafter known to
one of skill in the art. Temperatures and pressures described
herein are approximate.
[0034] In yet another embodiment, the diamond and catalyst may be
sintered in an HP/HT process without the metal carbide support. A
subsequent HP/HT or brazing process may be used to attach a
cemented metal carbide support.
[0035] In yet another embodiment, the metal carbide support may be
an annulus and the mass of diamond particles with catalyst (diamond
powder blend) may be disposed within the support annulus. These
maybe sintered together in the HP/HT process with or without the
addition of additional catalyst metal.
[0036] The disclosure contained herein relates to sintered PCD with
improved strength and toughness in machining, for example,
non-ferrous metals, ceramics, and wood-based composites. In
addition, it relates to improved machinability during fabrication
of wear components such as PCD machining tools, wear pads, punches,
and dies. Finally, it relates to the ability of such tools to give
an improved surface finish on workpieces, including, for example,
aluminum castings or steel wire. Tools as described herein may
include, for example, monolithic sintered PCD, a sintered PCD layer
bonded to a substrate (such as one of a cemented metal carbide,
such as cemented tungsten carbide or other material), and sintered
PCD inside an annulus of cemented metal carbide such as cemented
tungsten carbide or other material as would be used in wire
drawing.
[0037] In the commercial production of PCD in general, it is common
for the product or blank which is recovered from the reaction cell
of the HP/HT apparatus to be subjected to a variety of finishing
operations which include cutting, such as by electrode discharge
machining or with lasers, milling, and especially grinding to
remove any adherent shield metal from the outer surfaces of the
compact. Such operations additionally may be employed to machine
the compact into a shape which meets product specifications as to
diamond layer thickness and/or carbide support thickness.
[0038] In the resulting PCD body, the average, as-sintered diamond
grain size measured by the line intercept method may be less than
one micron. It may also be greater than 0.1 .mu.m. In various
embodiments, the average grain size may be less than 0.9 .mu.m, 0.8
.mu.m, 0.7 .mu.m, 0.6 .mu.m or 0.5 .mu.m. The PCD body may be
substantially uniform, These embodiments, based on symmetrical
normal grain size distributions, may contain 50%, 63%, 77%, 90%,
98% and 100% of the diamond grains below 1 .mu.m. Other embodiments
may have other ranges. It may also have a low oxygen content, such
as an oxygen content below 0.05%, below 0.01% or between a device
detection limit and either of the above numbers. The PCD bodies
contained herein may have thicknesses (i.e., top surface to
substrate interface) of about 0.5 millimeters (mm) to about 1 mm,
up to about 1.5 mm, greater than 1 mm, up to about 2 mm, or another
size.
[0039] As used herein, bodies having a "uniform" grain size or a
"substantially uniform" grain size are intended to encompass bodies
where the average grain size is less than 1 micron, meaning that
more than 50% of the particles are below 1 .mu.m after
sintering.
[0040] In addition, during manufacture, various amounts of cobalt
or other catalyst metal may be used. In some embodiments, some or
all of the catalyst metal may remain in the finished product. In an
embodiment where some or all of the catalyst metal may remain in
the material, it not present as a bonding agent phase. The metal
catalyst does not form chemical bonds with the diamond carbon, and
is present only as a residual contaminant.
EXAMPLES
[0041] Examples are provided herein to illustrate various
embodiments but are not intended to limit the scope of the
invention.
Example 1
[0042] Referring again to FIGS. 2A and 2B, this example
demonstrates the ability to make PCD composites in which the
sintered diamond is integrally bonded to a cemented metal carbide
substrate. A diamond-cobalt powder blend with approximately 7%
cobalt by weight, distributed as shown in FIG. 1 with approximately
0.8 .mu.m volumetric mean raw material diamond size 210, was
disposed between a tantalum (Ta) shielding enclosure 230 and a
cemented tungsten carbide (WC)+13 weight-percent cobalt disk. This
assembly was subjected to HP/HT processing at about 55 Kbar at
temperature of about 1400.degree. C. for about 20 minutes to form
the sintered submicron PCD tool blank 260. The PCD tool blank 250
was finished to produce a diamond layer 260 1.5 mm thick, and the
overall thickness of the blank 250 was 3.2 mm. The average
as-sintered diamond grain size, assessed by direct line intercept
measurement of the microstructure with a field emission scanning
electron microscope, was 0.87 .mu.m. Several variations of this
process were made using differing initial diamond powder sizes,
diamond layer thicknesses, and cobalt blend amounts. These
variations are summarized in Table 1. TABLE-US-00001 TABLE 1
Average as-sintered grain size and body thickness of submicron PCD
embodiments described herein. Average Grain Amount of Cobalt in
Average thickness of Size (.mu.m) Powder Blend (weight %) PCD body
(millimeters) 0.5 7 0.5 0.4 7 0.5 0.25 7 0.5 0.8 1 0.5 0.8 2 0.5
0.8 5 0.5 0.8 7 0.5 0.8 7 1.0 0.8 7 1.5 0.8 7 2 0.8 10 1.5
[0043] The sintered PCD bodies in Example 1 were analyzed using the
following techniques: scanning electron microscope (SEM), Oxygen
and Nitrogen determination. As a comparison, PCD bodies made with
prior technology and commercially available materials were also
analyzed. Table 2 highlights a few of the differences seen.
TABLE-US-00002 TABLE 2 Comparison of samples with and without
cobalt blending. Analytical Technique New PCD Material Prior Art
LECO-Nitrogen 0.009% 0.0165% LECO-Oxygen 0.046% 0.087%
[0044] Table 2 shows that the PCD materials of the embodiments
herein have low nitrogen and oxygen concentrations, as compared
with Prior Art PCD materials. Embodiments described herein may have
nitrogen contents below about 0.01% (w/w), Embodiments described
herein may have oxygen contents below about 0.05% (w/w).
[0045] SEM images in FIG. 3 show the submicron grain size of a PCD
body embodiment described herein prepared using diamond powder with
a volumetric mean size of 0.8 .mu.m. FIG. 4 shows the submicron
grain size of a PCD body embodiment described herein prepared using
diamond powder with a volumetric mean size of 0.5 .mu.m. FIG. 5
shows the grain size of a Sumitomo Grade DA2200 PCD body, which is
a commercially available product.
[0046] Table 3 shows measurements of the sintered diamond
microstructure of the same three materials as FIGS. 5-7, using the
line-intercept method. This method is based on the grain dimension
determined through the intersection of randomly drawn lines on a
microstructure photo. TABLE-US-00003 TABLE 3 Comparison of measured
grain sizes using line-intercept method. (sizes in microns)
Standard Average grain Deviation Product size (.mu.m) (.mu.m) 0.8
.mu.m Starting 0.87 0.41 Powder 0.5 .mu.m Starting 0.88 0.24 Powder
Sumitomo 1.46 0.79 DA2200
[0047] These evaluations show that the new PCD materials described
herein have a lower oxygen and nitrogen content, have much finer
grain sizes, and achieve an average grain size below 1 .mu.m, which
is much finer than the finest available commercial product.
Example 2
[0048] Referring to FIG. 8, this example illustrates the ability to
make carbide supported wire die blanks 800. These are materials in
which the diamond portion 810 is sintered into a carbide annulus
820 using a separate metal source as the catalyst rather than
sintering using the cobalt binder phase from the carbide substrate.
In this example, diamond powder 810 with a volumetric mean particle
size of 0.5 .mu.m further containing 7% by weight of the fine,
dispersed cobalt similar to Example 1 was used. The diamond and
cobalt powder blend 810 were loaded into the center of a carbide
cylinder 820 encased in a tantalum (Ta) enclosure 830. A cobalt
(Co) disc 840 (shown in exploded view) was placed on top of the
powder followed by a Ta shielding enclosure 850 (also in exploded
view), Several of these assemblies were loaded into a HP/HT
reaction cell and subjected to pressures of about 55 Kbar at
temperatures between about 1300.degree. C. and about 1500.degree.
C. for about 15 minutes to form the sintered PCD wire die. The PCD
wire dies are recovered from the reaction cell and finished such
that the entire PCD sintered volume was about 7 mm in diameter and
6 mm thick. The overall diameter of the wire die including the
carbide annulus surrounding the diamond was about 14 mm
[0049] It will be appreciated that various of the above-disclosed
and other features and functions, or alternatives thereof, may be
desirably combined into many other different systems or
applications. Also that various presently unforeseen or
unanticipated alternatives. modifications, variations or
improvements therein may be subsequently made by those skilled in
the art which are also intended to be encompassed by the following
claims.
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