U.S. patent application number 12/847500 was filed with the patent office on 2011-02-03 for polycrystalline diamond composite compact elements and tools incorporating same.
Invention is credited to Antionette Can, Kurtis Karl Schmitz, Danny Eugene Scott, Clement David Van Der Riet.
Application Number | 20110024201 12/847500 |
Document ID | / |
Family ID | 43525952 |
Filed Date | 2011-02-03 |
United States Patent
Application |
20110024201 |
Kind Code |
A1 |
Scott; Danny Eugene ; et
al. |
February 3, 2011 |
POLYCRYSTALLINE DIAMOND COMPOSITE COMPACT ELEMENTS AND TOOLS
INCORPORATING SAME
Abstract
A polycrystalline diamond (PCD) composite compact element 100
comprising a substrate 130, a PCD structure 120 bonded to the
substrate 130, and a bond material in the form of a bond layer 140
bonding the PCD structure 120 to the substrate 130; the PCD
structure 120 being thermally stable and having a mean Young's
modulus of at least about 800 GPa, the PCD structure 120 having an
interstitial mean free path of at least about 0.05 microns and at
most about 1.5 microns; the standard deviation of the mean free
path being at least about 0.05 microns and at most about 1.5
microns. Embodiments of the PCD composite compact element may be
for a tool for cutting, milling, grinding, drilling, earth boring,
rock drilling or other abrasive applications, such as the cutting
and machining of metal.
Inventors: |
Scott; Danny Eugene;
(Houston, TX) ; Schmitz; Kurtis Karl; (Yukon,
OK) ; Van Der Riet; Clement David; (County Clare,
IE) ; Can; Antionette; (Springs, ZA) |
Correspondence
Address: |
BRYAN CAVE LLP
211 NORTH BROADWAY, SUITE 3600
ST. LOUIS
MO
63102-2750
US
|
Family ID: |
43525952 |
Appl. No.: |
12/847500 |
Filed: |
July 30, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61230316 |
Jul 31, 2009 |
|
|
|
Current U.S.
Class: |
175/428 ;
428/312.2; 428/408; 51/296 |
Current CPC
Class: |
E21B 10/5735 20130101;
B22F 7/062 20130101; Y10T 428/30 20150115; B23K 35/00 20130101;
E21B 10/567 20130101; Y10T 428/249967 20150401; B24D 99/005
20130101; C22C 26/00 20130101; E21B 10/573 20130101; B22F 7/004
20130101; B22F 7/064 20130101; B23K 2101/002 20180801; B23K 1/0008
20130101; C22C 2204/00 20130101 |
Class at
Publication: |
175/428 ;
428/312.2; 51/296; 428/408 |
International
Class: |
E21B 10/46 20060101
E21B010/46; B24D 3/10 20060101 B24D003/10 |
Claims
1. A PCD composite compact element comprising a substrate, a PCD
structure bonded to the substrate, and a bond material bonding the
PCD structure to the substrate; the PCD structure being thermally
stable and having a mean Young's modulus of at least about 800 GPa,
the PCD structure having an interstitial mean free path of at least
about 0.05 microns and at most about 1.5 microns; the standard
deviation of the mean free path being at least about 0.05 microns
and at most about 1.5 microns.
2. A PCD composite compact element as claimed in claim 1, in which
the bond material is a braze alloy in the form of a braze layer
between the PCD structure and the substrate.
3. A PCD composite compact element as claimed in claim 2, in which
the braze alloy has a melting onset temperature of at most about
1,050 degrees centigrade and contains at least one element selected
from the group consisting of Ti, V, Cr, Mn, Zr, Nb, Mo, Hf, Ta, W
and Re.
4. A PCD composite compact element as claimed in claim 1, in which
the bond material comprises an epoxy material for joining ceramic
materials.
5. A PCD composite compact element as claimed in claim 3, in which
the substrate comprises PCD material.
6. A PCD composite compact element as claimed in claim 3, in which
there is less than about 5 volume percent of solvent/catalyst for
diamond in the PCD structure.
7. A PCD composite compact element as claimed in claim 2, in which
the PCD structure is at least partially porous.
8. A PCD composite compact element as claimed in claim 3, in which
the PCD structure has a mean diamond grain contiguity of at least
about 60 percent.
9. A PCD composite compact element as claimed in claim 3, in which
the PCD structure has transverse rupture strength of at least about
900 MPa.
10. A PCD composite compact element as claimed in claim 2, in which
the substrate includes diamond particles dispersed within it.
11. A PCD composite compact element as claimed in claim 3, in which
the PCD structure is not substantially entirely porous and has a
mean Young's modulus of at least about 900 GPa, and a transverse
rupture strength of least about 1,000 MPa.
12. A PCD composite compact element as claimed in claim 2, secured
to a drill bit or other earth boring tool.
13. A PCD composite compact element comprising a PCD structure
bonded to a substrate by means of a bond material; the PCD
structure being thermally stable and having a mean Young's modulus
of at least about 800 GPa and a mean diamond grain contiguity
greater than about 60 percent.
14. A PCD composite compact element as claimed in claim 13, in
which the bond material is a braze alloy in the form of a braze
layer between the PCD structure and the substrate.
15. A PCD composite compact element as claimed in claim 14, in
which the braze alloy has a melting onset temperature of at most
about 1,050 degrees centigrade and contains at least one element
selected from the group consisting of Ti, V, Cr, Mn, Zr, Nb, Mo,
Hf, Ta, W and Re.
16. A PCD composite compact element as claimed in claim 13, in
which the bond material comprises an epoxy material for joining
ceramic materials.
17. A PCD composite compact element as claimed in claim 15, in
which there is less than about 5 volume percent of solvent/catalyst
for diamond in the PCD structure.
18. A PCD composite compact element as claimed in claim 14, in
which the PCD structure is at least partially porous.
19. A PCD composite compact element as claimed in claim 15, secured
to a drill bit or other earth boring tool.
20. A PCD composite compact element as claimed in claim 15, in
which the PCD structure has an interstitial mean free path in the
range from about 0.05 micron to about 1.5 microns; and the standard
deviation of the mean free path is in the range from about 0.05
micron to about 1.5 microns.
21. A PCD composite compact element as claimed in claim 15, in
which the PCD structure has transverse rupture strength of at least
about 900 MPa.
22. A PCD composite compact element as claimed in claim 14, in
which the substrate includes diamond particles dispersed within
it.
23. A PCD composite compact element as claimed in claim 14, in
which the PCD structure is not substantially entirely porous and
has a mean Young's modulus of at least about 900 GPa, and a
transverse rupture strength of least about 1,000 MPa.
24. A PCD composite compact element comprising a PCD structure
bonded to a substrate by means of a braze layer comprising braze
alloy; the PCD structure being thermally stable and containing
braze material.
25. A PCD composite compact element as claimed in claim 24, in
which the braze alloy has a melting onset temperature of at most
about 1,050 degrees centigrade and contains at least one element
selected from the group consisting of Ti, V, Cr, Mn, Zr, Nb, Mo,
Hf, Ta, W and Re.
26. A method of making a PCD composite compact element as claimed
in claim 25, the method including providing a PCD structure,
treating the PCD structure to remove filler material from between
diamond grains and create pores, crevices or irregularities at a
boundary of the PCD structure; and brazing the PCD structure to a
substrate at the boundary.
Description
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/230,316, filed Jul. 31, 2009, which is
incorporated herein by reference in its entirety.
FIELD
[0002] Embodiments of the invention relate to polycrystalline
diamond (PCD) composite compact elements comprising a PCD
structure, particularly but not exclusively for a rock boring tool,
and to tools comprising the elements.
BACKGROUND
[0003] Polycrystalline diamond (PCD) is a super-hard, also known as
superabrasive material comprising a mass of inter-grown diamond
grains and interstices between the diamond grains. PCD may be made
by subjecting an aggregated mass of diamond grains to an ultra-high
pressure and temperature. A material wholly or partly filling the
interstices may be referred to as filler material. PCD may be
formed in the presence of a sintering aid such as cobalt, which is
capable of promoting the inter-growth of diamond grains. The
sintering aid may be referred to as a solvent/catalyst material for
diamond, owing to its function of dissolving diamond to some extent
and catalyst its re-precipitation. A solvent/catalyst for diamond
is understood be a material that is capable of promoting the growth
of diamond or the direct diamond-to-diamond inter-growth between
diamond grains at a pressure and temperature condition at which
diamond is thermodynamically stable. Consequently the interstices
within the sintered PCD product may be wholly or partially filled
with residual solvent/catalyst material. PCD may be formed on a
cobalt-cemented tungsten carbide substrate, which may provide a
source of cobalt solvent/catalyst for the PCD.
[0004] PCD may be used in a wide variety of tools for cutting,
machining, drilling or degrading hard or abrasive materials such as
rock, metal, ceramics, composites and wood-containing materials.
For example, PCD elements may be used as cutting elements on drill
bits used for boring into the earth in the oil and gas drilling
industry. In many of these applications the temperature of the PCD
material may become elevated as it engages a rock formation,
workpiece or body with high energy. Unfortunately, mechanical
properties of PCD such as hardness and strength tend to deteriorate
at high temperatures, largely as a result of residual
solvent/catalyst material dispersed within it.
[0005] PCT patent publication number WO9929465 discusses that
drilling hard rock and dealing with high well bore temperature
gradients have been persistent problems in the drilling industry.
The then current state-of-the-art TSP diamond cutter attachment
procedure is to braze thermally stable polycrystalline diamond (TSP
diamond) to carbide substrates. However, TSP brazing methods using
TiCuSil alloy result in an undesirable discontinuous layer of TiC
adjacent to the TSP diamond surface. Maximum strength properties
are not realized unless a thin continuous layer of reaction product
forms on the TSP surface (i.e. unless wetting is complete).
[0006] U.S. Pat. No. 7,377,341 discusses that a PCD body that is
substantially free of the solvent catalyst material is precluded
from subsequent attachment to a metallic substrate by brazing or
other similar bonding operation. The attachment of such substrates
to the PCD body is highly desired to provide a PCD compact element
that can be readily adapted for use in many desirable applications.
However, it is very difficult to bond the thermally stable PCD body
to conventionally used substrates. Since conventionally formed
thermally stable PCD bodies are devoid of a metallic substrate,
they cannot be attached to a drill bit by conventional brazing
process. Rather, the use of such a thermally stable PCD body in
drilling application requires that the PCD body itself be mounted
to the drill bit by mechanical or interference fit during
manufacturing of the drill bit, which is labour intensive, time
consuming, and which does not provide a most secure method of
attachment.
[0007] U.S. Pat. No. 7,435,377 discusses that polycrystalline
diamond (PCD) and other ultra-hard materials may be joined to a
supporting mass by means of brazing. However, a disadvantage of
brazing is relates to concerns over potential heat damage of the
PCD product, which has been a limiting factor in the past.
[0008] U.S. Pat. No. 7,487,849 discusses that because TSP
(thermally stable product) is made by removing cobalt from a
diamond layer, attachment of TSP to a substrate is significantly
more complicated, as compared to the attachment of PDC to a
substrate.
[0009] U.S. Pat. No. 7,533,740 discloses a cutting element
comprising TSP material bonded to a tungsten carbide substrate by
brazing (this patent uses the term "TSP" as described in U.S. Pat.
Nos. 7,234,550 and 7,426,696, which use the term "TSP" to mean
"thermally stable product", including both partially and completely
leached polycrystalline diamond compounds).
[0010] United States patent publication number 2008/0085407
discloses a super-abrasive compact element wherein a super-abrasive
volume including a tungsten carbide layer may be brazed, soldered,
welded (including frictional or inertial welding), or otherwise
affixed to a substrate.
[0011] There is a need for PCD composite compact elements,
particularly thermally stable PCD elements, having superior
mechanical properties.
SUMMARY
[0012] An embodiment of the invention provides a polycrystalline
diamond (PCD) composite compact element comprising a substrate, a
PCD structure bonded to the substrate, and a bond material bonding
the PCD structure to the substrate; the PCD structure being
thermally stable and having a mean Young's modulus of at least
about 800 GPa, at least about 850 GPa, or at least 870 GPa, the PCD
structure having an interstitial mean free path of at least about
0.05 microns and at most about 1.5 microns; the standard deviation
of the mean free path being at least about 0.05 microns and at most
about 1.5 microns.
[0013] An embodiment of the invention provides a PCD composite
compact element comprising a PCD structure bonded to a substrate by
means of a bond material; the PCD structure being thermally stable
and having a mean Young's modulus of at least about 800 GPa, at
least about 850 GPa, or at least 870 GPa, and a mean diamond grain
contiguity greater than about 60 percent or greater than 60.5
percent.
[0014] In one embodiment of the invention, the bond material may
comprise an epoxy material for joining ceramic materials.
[0015] In one embodiment of the invention, the PCD structure may be
brazed to the substrate, the bond material being a braze alloy in
the form of a braze layer between the PCD structure and the
substrate.
[0016] In one embodiment of the invention, the braze alloy may have
a melting onset temperature, at which the alloy begins to melt, of
at most about 1,050 degrees centigrade, at most about 950 degrees
centigrade, at most about 900 degrees centigrade or even at most
about 850 degrees centigrade, and may contain at least one element
selected from the group consisting of Ti, V, Cr, Mn, Zr, Nb, Mo,
Hf, Ta, W and Re. In some embodiments, the braze alloy may contain
Ti and Ag, or Ti and Cu.
[0017] An embodiment of the invention provides a PCD composite
compact element comprising a PCD structure bonded to a substrate by
means of a braze layer comprising braze material; the PCD structure
being thermally stable and containing braze material.
[0018] In some embodiments of the invention, the PCD structure may
contain braze alloy material within pores, crevices or
irregularities formed at a boundary of the PCD structure. In one
embodiment, pores, crevices or irregularities may formed at a
boundary of the PCD structure by removing filler material from
between diamond grains, such as by means of acid treatment.
[0019] In some embodiments of the invention, the PCD structure may
have a mean Young's modulus of at least about 800 GPa, at least
about 850 GPa, or at least 870 GPa.
[0020] In one embodiment of the invention, the PCD structure may
contain braze alloy material to a depth of at least about 2 microns
from an interface or boundary, such as an interface with the braze
layer or with the substrate. In some embodiments of the invention,
the PCD structure may contain braze material to a depth from an
interface with the braze layer, the depth being in the range from
about 2 microns to about 1,000 microns, in the range from about 2
microns to about 25 micron, or in the range from about 5 microns to
about 15 microns. In one embodiment, the PCD structure may contain
braze material substantially throughout the whole of the PCD
structure.
[0021] In some embodiments of the invention, the PCD structure may
have an interstitial mean free path in the range from about 0.05
micron to about 1.3 microns, in the range from about 0.1 micron to
about 1 micron, or in the range from about 0.5 micrometers to about
1 micron; and the standard deviation of the mean free path may be
in the range from about 0.05 micron to about 1.5 microns, or in the
range from about 0.2 micron to about 1 micron.
[0022] In some embodiments of the invention, the PCD structure may
have a mean diamond grain contiguity of at least about 60 percent,
in the range from 60.5 percent to about 80 percent, in the range
from 60.5 percent to about 77 percent, or in the range from 61.5
percent to about 77 percent. In one embodiment of the invention,
the PCD structure may have a mean diamond grain contiguity of at
most about 80 percent.
[0023] In some embodiments of the invention, the PCD structure may
have a transverse rupture strength of at least about 900 MPa, at
least about 950 MPa, at least about 1,000 MPa, at least about 1,050
MPa, or even at least about 1,100 MPa.
[0024] In some embodiments of the invention, the substrate may be
formed of cemented carbide, such as cobalt-cemented tungsten
carbide, or the substrate may comprise PCD material, or the
substrate may be a composite compact element comprising cemented
carbide and PCD material. In one embodiment of the invention, the
PCD structure may be brazed to a further PCD structure, and in one
embodiment, the PCD structure may be more thermally stable than the
further PCD structure.
[0025] In some embodiments of the invention, the substrate may
include superhard particles such as diamond particles dispersed
within it. In one embodiment, the substrate may include diamond
particles, the content of which may be in the range from about 20
volume percent to about 60 volume percent.
[0026] In some embodiments of the invention, the PCD structure may
exhibit no substantial structural degradation or deterioration of
hardness or abrasion resistance after exposure to a temperature
above about 400 degrees centigrade or in the range from about 750
degrees centigrade to about 800 degrees centigrade, or even in the
range from about 760 degrees centigrade to about 810 degrees
centigrade.
[0027] In one embodiment, the PCD structure may be substantially
free of material capable of functioning as solvent/catalyst for
diamond. In some embodiments, there may be less than about 5 volume
percent, less than about 2 volume percent, less than about 1 volume
percent or less than about 0.5 volume percent of solvent/catalyst
for diamond in the PCD structure. In some embodiments, the PCD
structure may be at least partially porous, or substantially the
entire PCD structure may be porous.
[0028] In some embodiments of the invention, the PCD structure may
have an oxidation onset temperature of at least about 800 degrees
centigrade, at least about 900 degrees centigrade or even at least
about 950 degree centigrade.
[0029] In some embodiments of the invention, the PCD structure may
not be substantially entirely porous and may have a mean Young's
modulus of at least about 900 GPa, at least about 950 GPa, at least
about 1,000 GPa; and the transverse rupture strength is at least
about 1,000 MPa, at least about 1,100 Mpa, at least about 1,400
MPa, at least about 1,500 MPa, or even at least about 1,600
MPa.
[0030] In one embodiment of the invention, PCD structure may
include a filler material comprising a ternary carbide of the
general formula: Mx M'y Cz wherein; M is at least one metal
selected from the group consisting of the transition metals and the
rare earth metals; M' is a metal selected from the group consisting
of the main group metals or metalloid elements and the transition
metals Zn and Cd; x is from 2.5 to 5.0; y is from 0.5 to 3.0; and z
is from 0.1 to 1.2.
[0031] In some embodiments, the PCD structure may include a filler
material comprising a tin-based inter-metallic or ternary carbide
compound formed with a metallic solvent/catalyst for diamond. In
one embodiment, the metallic solvent/catalyst material for diamond
may comprise cobalt.
[0032] In one embodiment of the invention, the shear strength of
the bond between the PCD structure and the substrate may be greater
than about 100 MPa. In some embodiments, the shear strength of the
bond between the PCD structure and the substrate may be in the
range from about 100 MPa to about 500 MPa, in the range from about
100 MPa to about 300 MPa, or in the range from about 200 MPa to
about 300 MPa.
[0033] In some embodiments of the invention, the PCD structure may
comprise at least about 90 volume percent inter-bonded diamond
grains having a mean size in the range from about 0.1 microns to 25
microns, in the range from about 0.1 micron to 20 microns, in the
range from about 0.1 micron to about 15 microns, in the range from
about 0.1 microns to about 10 microns, or in the range from about
0.1 micron to about 7 micron. In one embodiment, the PCD structure
may comprise a diamond content in the range from about 90 to about
99 volume percent of the PCD structure, and in one embodiment, the
PCD structure may comprise at least 92 volume percent diamond.
[0034] In one embodiment of the invention, the PCD structure may
comprise diamond grains having a multi-modal size distribution. In
some embodiments, the PCD structure may comprise bonded diamond
grains having the size distribution characteristic that at least
about 50 percent of the grains have mean size greater than about 5
microns, and at least about 20 percent of the grains have mean size
in the range from about 10 to about 15 microns.
[0035] In some embodiments of the invention, the PCD structure may
be made by a method including forming a plurality of diamond grains
into an aggregated mass and sintering them in the presence of a
solvent/catalyst material for diamond, the sintering including
subjecting the aggregated mass and the solvent/catalyst material to
a temperature sufficiently high for the solvent/catalyst to melt
and to a pressure of greater than 6.0 GPa, at least 6.2 GPa, at
least about 6.5 GPa, at least about 7 GPa or at least about 8
GPa.
[0036] In some embodiments of the invention, the PCD structure may
comprise at least two portions, each portion being formed of PCD
material having different microstructure, composition or diamond
particle size distribution, or combination of these, and different
properties, such as strength or Young's modulus. In some
embodiments, at least one portion may comprise diamond particles
having a multi-modal size distribution with mean particle size in
the range from about 5 microns to about 20 microns, or in the range
from about 5 microns to 15 about microns.
[0037] In one embodiment of the invention, the PCD composite
compact element may be suitable for a drill bit for boring into the
earth, such as a rotary shear-cutting bit for use in the oil and
gas drilling industry. In one embodiment, the PCD composite compact
element may comprise a cutting element for a rolling cone, hole
opening tool, expandable tool, reamer or other earth boring
tools.
[0038] An embodiment of the invention provides a polycrystalline
diamond (PCD) composite compact element, comprising a PCD structure
bonded to a substrate; the PCD structure being substantially free
of material capable of functioning as solvent/catalyst for diamond
and having a mean Young's modulus of at least about 800 GPa, at
least about 850 GPa, or at least about 870 GPa.
[0039] An embodiment of the invention provides a tool comprising an
embodiment of a PCD composite compact element according to the
invention, the tool being for cutting, milling, grinding, drilling,
earth boring, rock drilling or other abrasive applications, such as
the cutting and machining of metal.
[0040] A method of making an embodiment of a PCD composite compact
element according to the invention is provided, the method
including providing a PCD structure, treating the PCD structure to
remove filler material from between diamond grains and create
pores, crevices or irregularities at a boundary of the PCD
structure; and brazing the PCD structure to a substrate at the
boundary. The method is an aspect of the invention.
[0041] In one version of the method, pores, crevices or
irregularities may be formed on a surface of the PCD structure by
means of treating the PCD structure with acid. In one embodiment,
the pores, crevices or irregularities may have a mean size
substantially the same as the mean size of the interstices between
the diamond grains, and in some embodiments, the mean size may be
at least about 2 microns or at least about 5 microns, and at most
about 10 microns.
DRAWINGS
[0042] Non-limiting embodiments will now be described with
reference to the accompanying drawings of which:
[0043] FIG. 1A shows a schematic perspective view of an embodiment
of a PCD composite compact element, and FIG. 1B shows schematic
longitudinal cross-section view of the embodiment of the PCD
composite compact element shown in FIG. 1A.
[0044] FIG. 2, FIG. 3, FIG. 4, FIG. 5 and FIG. 6 show drawings of
schematic longitudinal cross-section views of embodiments of PCD
composite compact elements.
[0045] FIG. 7 shows a perspective view of a rotary drill bit for
boring into the earth.
[0046] FIG. 8 shows an image of a PCD polished section, showing
calculated lines indicating diamond-to-diamond contact.
[0047] FIG. 9, FIG. 10 and FIG. 11 show graphs of number of grains
versus grain size for examples of multimodal size distributions of
the diamond grains within embodiments of polycrystalline diamond
structures.
[0048] FIG. 12 shows a schematic side view of an apparatus for
measuring the transverse rupture strength of a specimen.
[0049] The same reference numbers refer to the same features in all
drawings.
DETAILED DESCRIPTION OF EMBODIMENTS
[0050] As used herein, a "catalyst material for diamond", also
referred to as "solvent/catalyst for diamond", is a material that
is capable of promoting the nucleation, growth or inter-bonding of
diamond grains at a pressure and temperature at which diamond is
thermodynamically stable. Catalyst materials for diamond may be
metallic, such as cobalt, iron, nickel, manganese and alloys of
these, or non-metallic.
[0051] As used herein, "polycrystalline diamond" (PCD) material
comprises a mass of diamond grains, a substantial portion of which
are directly inter-bonded with each other and in which the content
of diamond is at least about 80 volume percent of the material. In
one embodiment of PCD material, interstices between the diamond
gains may be at least partly filled with a binder material
comprising a catalyst for diamond. As used herein, "interstices" or
"interstitial regions" are regions between the diamond grains of
PCD material. In embodiments of PCD material, interstices or
interstitial regions may be substantially or partially filled with
a material other than diamond, or they may be substantially empty.
As used herein, a "filler" material is a material that wholly or
partially fills pores, interstices or interstitial regions within a
structure, such as a polycrystalline structure. Thermally stable
embodiments of PCD material may comprise at least a region from
which catalyst material has been removed from the interstices,
leaving interstitial voids between the diamond grains. As used
herein, a "thermally stable PCD" structure is a PCD structure at
least a part of which exhibits no substantial structural
degradation or deterioration of hardness or abrasion resistance
after exposure to a temperature above about 400 degrees
centigrade.
[0052] With reference to FIG. 1A and FIG. 1B, an embodiment of a
PCD composite compact element 100 may comprise a thermally stable
PCD structure 120 bonded to the substrate 130 by means of a bond
material in the form of a bond layer 140 between the PCD structure
120 and the substrate 130. In one version of the embodiment, the
PCD structure 120 may be substantially free of material capable of
functioning as solvent/catalyst for diamond. In another version of
the embodiment, the PCD structure 120 may include non-metallic
solvent/catalyst for diamond.
[0053] With reference to FIG. 2, an embodiment of a PCD composite
compact element 100 may comprise a first PCD structure 122 bonded
to a second PCD structure 124 by means of a bond material in the
form of a bond layer 140 between the first PCD structure 122 and
the second PCD structure 124. The first PCD structure 122 may be
more thermally stable than the second PCD structure 124. The second
PCD structure 124 may be integrally bonded to a cemented carbide
substrate 130.
[0054] With reference to FIG. 3, an embodiment of a PCD composite
compact element 100 may comprise a first PCD structure 122 bonded
to a second PCD structure 124 by means of a bond material in the
form of a bond layer 140 between the first PCD structure 122 and
the second PCD structure 124. The second PCD structure 124 may be
bonded by means of a bond material in the form of a bond layer 142
between the second PCD structure 124 and the substrate 140.
[0055] With reference to FIG. 4, an embodiment of a PCD composite
compact element 100 may comprise a first PCD structure 122 bonded
to a second PCD structure 124 by means of a bond material in the
form of a bond layer 140 between the first PCD structure 122 and
the second PCD structure 124. The second PCD structure 124 may not
be bonded or otherwise joined to a cemented carbide substrate.
[0056] With reference to FIG. 5, an embodiment of a PCD composite
compact element 100 may comprise a PCD structure 120 bonded to the
substrate 130 by means of a bond material in the form of a bond
layer 140, and the substrate 130 may include diamond particles 132
dispersed within it.
[0057] "Young's modulus" is a type of elastic modulus and is a
measure of the uniaxial strain in response to a uniaxial stress,
within the range of stress for which the material behaves
elastically. A preferred method of measuring the Young's modulus E
is by means of measuring the transverse and longitudinal components
of the speed of sound through the material, according to the
equation E=2.rho..C.sub.T.sup.2(1+.upsilon.), where
.upsilon.=(1-2(C.sub.T/C.sub.L).sup.2)/(2-2(C.sub.T/C.sub.L).sup.2),
C.sub.L and C.sub.T are respectively the measured longitudinal and
transverse speeds of sound through it and .rho. is the density of
the material. The longitudinal and transverse speeds of sound may
be measured using ultrasonic waves, as is well known in the art.
Where a material is a composite of different materials, the mean
Young's modulus may be estimated by means of one of three formulas,
namely the harmonic, geometric and rule of mixtures formulas as
follows: E=1/(f.sub.1/E.sub.1+f.sub.2/E.sub.2));
E=E.sub.1.sup.f1+E.sub.1.sup.f2; and E=f.sub.1 E.sub.1+f.sub.2
E.sub.2; in which the different materials are divided into two
portions with respective volume fractions of f.sub.1 and f.sub.2,
which sum to one.
[0058] With reference to FIG. 6, an embodiment of a PCD composite
compact element 100 may comprise a PCD structure 120 bonded to a
cemented carbide substrate 130 by means of a bond material in the
form of a bond layer 140, in which the PCD structure 120 may
comprise a first portion 122 integrally formed with a second
portion 124 and the first and second portions may have different
microstructure, composition or diamond particle size distribution,
or combination of these, and different properties, such as strength
or Young's modulus.
[0059] In the embodiments described with reference to FIG. 1A, FIG.
1B, FIG. 2, FIG. 3, FIG. 4, FIG. 5 and FIG. 6, the bond material
may comprise or consist of a braze alloy material and the bond
layer 140 may be a braze layer. In one embodiment, the bond
material may comprise or consist of an epoxy material for bonding
or joining ceramic materials.
[0060] With reference to FIG. 7, an embodiment of an earth-boring
rotary drill bit 200 of the present invention includes, for
example, a plurality of cutting elements 100 as previously
described herein with reference to FIG. 1. The earth-boring rotary
drill bit 200 includes a bit body 202 that is secured to a shank
204 having a threaded connection portion 206 (e.g., a threaded
connection portion 206 conforming to industry standards such as
those promulgated by the American Petroleum Institute (API)) for
attaching the drill bit 200 to a drill string (not shown). The bit
body 202 may comprise a particle-matrix composite material or a
metal alloy such as steel. The bit body 202, may be secured to the
shank 204 by one or more of a threaded connection, a weld, and a
braze alloy at the interface between them. In some embodiments, the
bit body 202 may be secured to the shank 204 indirectly by way of a
metal blank or extension between them, as known in the art.
[0061] The bit body 202 may include internal fluid passageways (not
shown) that extend between the face 203 of the bit body 202 and a
longitudinal bore (not shown), which extends through the shank 204
the extension 208 and partially through the bit body 202. Nozzle
inserts 224 also may be provided at the face 203 of the bit body
202 within the internal fluid passageways. The bit body 202 may
further include a plurality of blades 216 that are separated by
junk slots 218. In some embodiments, the bit body 202 may include
gage wear plugs 222 and wear knots 228. A plurality of PDC cutting
elements 100 of one or more of embodiments as previously described
herein may be mounted on the face 203 of the bit body 202 in
cutting element pockets 212 that are located along each of the
blades 216. In other embodiments, PDC cutting elements 100 as
previously described with reference to FIG. 1, FIG. 2, FIG. 3, FIG.
4, FIG. 5, FIG. 6 or any other embodiment of a PDC cutting element
of the present invention, may be provided in the cutting element
pockets 212.
[0062] The cutting elements 100 are positioned to cut a
subterranean formation being drilled while the drill bit 200 is
rotated under weight on bit (WOB) in a bore hole about centreline
L200.
[0063] In the field of quantitative stereography, particularly as
applied to cemented carbide material, "contiguity" is understood to
be a quantitative measure of inter-phase contact. It is defined as
the internal surface area of a phase shared with grains of the same
phase in a substantially two-phase microstructure (Underwood, E. E,
"Quantitative Stereography", Addison-Wesley, Reading Mass. 1970;
German, R. M. "The Contiguity of Liquid Phase Sintered
Microstructures", Metallurgical Transactions A, Vol. 16A, July
1985, pp. 1247-1252). As used herein, "diamond grain contiguity"
.kappa. is a measure of diamond-to-diamond contact or bonding, or a
combination of contact and bonding within PCD material, and is
calculated according to the following formula using data obtained
from image analysis of a polished section of PCD material:
.kappa.=100*[2*(.delta.-.beta.)]/[(2*(.delta.-.beta.))+.delta.],
where .delta. is the diamond perimeter, and .beta. is the binder
perimeter.
[0064] As used herein, the "diamond perimeter" is the fraction of
diamond grain surface that is in contact with other diamond grains.
It is measured for a given volume as the total diamond-to-diamond
contact area divided by the total diamond grain surface area. The
binder perimeter is the fraction of diamond grain surface that is
not in contact with other diamond grains. In practice, measurement
of contiguity is carried out by means of image analysis of a
polished section surface. The combined lengths of lines passing
through all points lying on all diamond-to-diamond interfaces
within the analysed section are summed to determine the diamond
perimeter, and analogously for the binder perimeter.
[0065] FIG. 8 shows an example of a processed SEM image of a
polished section of a PCD structure, showing the boundaries 360
between diamond grains 320. These boundary lines 360 were
calculated by the image analysis software and were used to measure
the diamond perimeter and subsequently for calculating the diamond
grain contiguity. The non-diamond regions 340, which may be filled
interstices or voids, for example, are indicated as dark areas. The
binder perimeter was obtained from the cumulative length of the
boundaries 360 between the diamond 320 and the non-diamond or
interstitial regions 340.
[0066] FIG. 9, FIG. 10 and FIG. 11 show non-limiting examples of
multimodal grain size distributions of diamond grains within
embodiments of PCD structures, for the purpose of illustration. As
used herein, a "multimodal" size distribution of a mass of grains
is understood to mean that the grains have a size distribution with
more than one peak 400, each peak 400 corresponding to a respective
"mode". Multimodal polycrystalline bodies may be made by providing
more than one source of a plurality of grains, each source
comprising grains having a substantially different average size,
and blending together the grains or grains from the sources.
Measurement of the size distribution of the blended grains may
reveal distinct peaks corresponding to distinct modes. When the
grains are sintered together to form the polycrystalline body,
their size distribution may be further altered as the grains are
compacted against one another and fractured, resulting in the
overall decrease in the sizes of the grains. Nevertheless, the
multimodality of the grains may still be clearly evident from image
analysis of the sintered article.
[0067] The size of grains is expressed in terms of equivalent
circle diameter (ECD). As used herein, the "equivalent circle
diameter" (ECD) of a particle is the diameter of a circle having
the same area as a cross section through the particle. The ECD size
distribution and mean size of a plurality of particles may be
measured for individual, unbonded particles or for particles bonded
together within a body, by means of image analysis of a
cross-section through or a surface of the body. Unless otherwise
stated herein, dimensions of size, distance, perimeter, ECD, mean
free path and so forth relating to grains and interstices within
PCD material, as well as the grain contiguity, refer to the
dimensions as measured on a surface of, or a section through a body
comprising PCD material and no stereographic correction has been
applied. For example, the size distributions of the diamond grains
as shown in FIG. 9, FIG. 10 and FIG. 11 were measured by means of
image analysis carried out on a polished surface, and a Saltykov
correction was not applied.
[0068] In one embodiment of the invention, the PCD structure may
comprise a first portion formed of a PCD material comprising
diamond grains having at least three modes in the multimodal size
distribution as shown in FIG. 9, and a second portion formed of a
PCD material comprising diamond grains having at least four-modes
multimodal size distribution as shown in FIG. 10, the mean size of
the grains in the first portion being substantially less than that
in the second portion, and the first and second portions of the PCD
structure being integrally formed with each other. The PCD
structure may be brazed to the substrate with the second portion of
the PCD structure proximate the substrate and the first portion of
the PCD structure remote from the substrate.
[0069] In one embodiment of the invention, the PCD structure may
comprise a first portion formed a PCD material comprising diamond
grains having two modes in the multimodal size distribution as
shown in FIG. 11, and a second portion formed of a PCD material
comprising diamond grains having at least three modes in the
multimodal size distribution as shown in FIG. 9, the first and
second portions of the PCD structure being integrally formed with
each other. The PCD structure may be brazed to the substrate with
the second portion of the PCD structure proximate the substrate and
the first portion of the PCD structure remote from the
substrate.
[0070] In some embodiments, the PCD structure may be as taught in
PCT publication number WO2009/027948, which discloses a PCD
structure comprising a diamond phase and a filler material, the
filler material comprising a ternary carbide of the general
formula: Mx M'y Cz wherein; M is at least one metal selected from
the group consisting of the transition metals and the rare earth
metals; M' is a metal selected from the group consisting of the
main group metals or metalloid elements and the transition metals
Zn and Cd; x is from 2.5 to 5.0; y is from 0.5 to 3.0; and z is
from 0.1 to 1.2.
[0071] In some embodiments, the PCD structure may be as taught in
PCT publication number WO2009/027949, which discloses PCD composite
material comprising inter-grown diamond grains and a filler
material, the filler material comprising a tin-based inter-metallic
or ternary carbide compound formed with a metallic
solvent/catalyst. The use of CoSn may facilitate PCD sintering at
high-pressure high temperature conditions at which the temperature
is between about 1,300 and about 1,450 degrees centigrade and the
pressure is between about 5.0 and about 5.8 GPa. In some
embodiments, substantially all of the cobalt may be removed from
the PCD structure prior to brazing the structure to a
substrate.
[0072] The homogeneity of the microstructure may be characterised
in terms of the combination of the mean thickness of the
interstices between the diamonds, and the standard deviation of
this thickness. The homogeneity or uniformity of a PCD structure
may be quantified by conducting a statistical evaluation using a
large number of micrographs of polished sections. The distribution
of a filler phase or of pores within the PCD structure may be
easily distinguishable from that of the diamond phase using
electron microscopy and can be measured in a method similar to that
disclosed in EP 0 974 566 (see also WO2007/110770). This method
allows a statistical evaluation of the average thicknesses or
interstices along several arbitrarily drawn lines through the
microstructure. The mean binder or interstitial thickness is also
referred to as the "mean free path". For two materials of similar
overall composition or binder content and average diamond grain
size, the material that has the smaller average thickness will tend
to be more homogenous, as this indicates a finer scale distribution
of the binder in the diamond phase. In addition, the smaller the
standard deviation of this measurement, the more homogenous is the
structure. A large standard deviation indicates that the binder
thickness varies widely over the microstructure and that the
structure is not uniform.
[0073] As used herein, the "interstitial mean free path" within a
polycrystalline material comprising an internal structure including
interstices or interstitial regions, such as PCD, is understood to
mean the average distance across each interstitial between
different points at the interstitial periphery. The average mean
free path is determined by averaging the lengths of many lines
drawn on a micrograph of a polished sample cross section. The mean
free path standard deviation is the standard deviation of these
values. The diamond mean free path is defined and measured
analogously.
[0074] In measuring the mean value and deviation of a quantity such
as grain contiguity, or other statistical parameter measured by
means of image analysis, several images of different parts of a
surface or section are used to enhance the reliability and accuracy
of the statistics. The number of images used to measure a given
quantity or parameter may be at least about 9 or even up to about
36. The number of images used may be about 16. The resolution of
the images needs to be sufficiently high for the inter-grain and
inter-phase boundaries to be clearly made out. In the statistical
analysis, typically 16 images are taken of different areas on a
surface of a body comprising the PCD material, and statistical
analyses are carried out on each image as well as across the
images. Each image should contain at least about 30 diamond grains,
although more grains may permit more reliable and accurate
statistical image analysis.
[0075] In some embodiments, the PCD structure may be as taught in
PCT publication number WO2007/020518, which discloses
polycrystalline diamond a polycrystalline diamond abrasive element
comprising a fine grained polycrystalline diamond material
characterised in that it has an interstitial mean-free-path value
of less than 0.60 microns, and a standard deviation for the
interstitial mean-free-path that is less than 0.90 microns. In one
embodiment, the polycrystalline diamond material may have a mean
diamond grain size of from about 0.1 micron to about 10.5
microns.
[0076] In some embodiments, the PCD structure may be manufactured
using a method including sintering of diamond grains in an
ultra-high pressure and temperature (HPHT) process in the presence
of a solvent/catalyst material for diamond and then removing
solvent/catalyst material from interstices within the PCD
structure. Catalyst material may be removed from the PCD table
using methods known in the art such as electrolytic etching, acid
leaching and evaporation techniques. In some embodiments, a masking
or passivating medium may be introduced into pores within the PCD
structure.
[0077] Solvent/catalyst material may be introduced to an aggregated
mass of diamond grains for sintering in various ways known in the
art. One way includes depositing metal oxide onto the surfaces of a
plurality of diamond grains by means of precipitation from an
aqueous solution prior to forming their consolidation into an
aggregated mass. Such methods are disclosed in PCT publications
numbers WO2006/032984 and also WO2007/110770. Another way includes
preparing or providing metal alloy including a catalyst material
for diamond, such as cobalt-tin alloy, in powder form and blending
the powder with the plurality of diamond grains prior to their
consolidation into an aggregated mass. The blending may be carried
out by means of a ball mill. Other additives may be blended into
the aggregated mass.
[0078] In one embodiment, the aggregated mass of diamond grains,
including any solvent/catalyst material particles or additive
material particles that may have been introduced, may be formed
into an unbonded or loosely bonded structure, which may be placed
onto a cemented carbide substrate. The cemented carbide substrate
may contain a source of catalyst material for diamond, such as
cobalt. The assembly of aggregated mass and substrate may be
encapsulated in a capsule suitable for an ultra-high pressure
furnace apparatus and subjecting the capsule to a pressure of
greater than 6 GPa. Various kinds of ultra-high pressure apparatus
are known and can be used, including belt, torroidal, cubic and
tetragonal multi-anvil systems. The temperature of the capsule
should be high enough for the source of catalyst material to melt
and low enough to avoid substantial conversion of diamond to
graphite. The time should be long enough for sintering to be
completed but as short as possible to maximise productivity and
reduce costs.
[0079] As noted previously, the PCD structure may have an oxidation
onset temperature of at least about 800 degrees centigrade.
Embodiments of such PCD may have superior thermal stability and
exhibit superior performance in applications such as oil and gas
drilling, wherein the temperature of a PCD cutter element can reach
several hundred degrees centigrade. Oxidation onset temperature is
measured by means of thermo-gravimetric analysis (TGA) in the
presence of oxygen, as is known in the art.
[0080] In some embodiments of the invention, the bond material may
comprise a high shear strength epoxy resin or epoxy paste material
for joining ceramic materials, for example epoxy paste under the
trade name ES550.TM. from Permabond.TM., or solder material. In one
embodiment, the bond material may comprise or consist of an organic
adhesive.
[0081] In some embodiments the PCD structure may be brazed to the
substrate by means of microwave brazing, wherein the braze material
is heated by means of microwave energy. Brazing the PCD using an
active braze material in a very high vacuum may result in braze
strength high enough for the PCD compact element to be technically
and economically viable. Active brazing is discussed by H. R.
Prabhakara (in "Vacuum brazing of ceramics and graphite to metals",
Bangalore Plasmatek Pvt. Ltd, 129, Block-14, Jeevanmitra Colony
I-Phase, Bangalore 560 078).
[0082] In some embodiments, the braze alloy may have a melting
onset temperature, at which the alloy begins to melt, of at most
about 1,050 degrees centigrade, at most about 1,000 degrees
centigrade or at most about 950 degrees centigrade. Such
embodiments may have the advantage of permitting a PCD structure to
be brazed to a substrate at a temperature sufficiently low that
thermally-induced degradation the PCD may be reduced or avoided.
The process of brazing PCD to a substrate may be carried out in a
substantially inert atmosphere that inhibits oxidation, which may
have the advantage of resulting in a stronger braze bond.
[0083] In one embodiment, the braze alloy may comprise an element
that readily reacts with carbon to form carbide, and in one
embodiment, the braze alloy may be a reactive braze alloy, which
may effectively wet the surface of diamond.
[0084] In one embodiment, the braze alloy may contain Ti, which may
effectively wet the surface of the diamond. In some embodiments,
the braze alloy may contain Cu, Ni, Ag or Au, which may effectively
wet a cemented carbide substrate. One type of reactive braze alloy
may modify the surface of the diamond operative to make it more
readily wettable. Examples of this type of reactive braze alloys
may comprise Mo, W, Ti, Ta, V and Zr. In some embodiments, the
braze alloy may comprise or consist essentially of Ti, Cu and Ag,
also referred to as "TiCuSil" braze alloys, which may comprise a
eutectic composition of Ag and Cu, as well as an amount of Ti. For
example, the weight ratio of Ti to Cu to Ag may be 4.5:26.7:68.8,
or the ratio of Ti to Cu to Ag may be 10.0:25.4:64.6, or the ratio
of Ti to Cu to Ag may be 15.0:24.0:61.0. In one embodiment, the
braze alloy may comprise about 63.00% Ag, about 32.25% Cu and about
1.75% Ti, and may be available under the trade name of Cusil.TM.
ABA. In one embodiment, the braze alloy may comprise about 70.5%
Ag, about 26.5% Cu and about 3.0% Ti, available under the trade
name of CB4,
[0085] Braze alloys having a high strength may include Cu, alloys
comprising Ni and Cr alloys, and brazes containing high percentages
of elements such as Pd and similar high strength materials, and
Cr-based active brazes. In one embodiment, the braze alloy may
comprise or consist essentially of Ni, Pd and Cr. In some
embodiments, the ratio of the weight ratio of Pd to Ni may be in
the range from about 0.4 to about 0.8. In one embodiment, the braze
alloy may comprise Ni, Pd, Cr, B and Si, and in one embodiment, the
weight ratio of Ni to Pd to Cr to B to Si may be about
50:36:10.5:3:0.5, or the weight ratio of Ni to Pd to Cr to B to Si
may be about 57:30:10.5:2.4. Braze alloy material comprising Ni,
Pd, Cr, B may be obtained under the trade name Palnicro.TM. 36M
from WESGO Metals.TM.. In one embodiment, the braze alloy may
comprise Ag, Cu, Ni, Pd and Mn, and in one embodiment, the weight
ratio of Ag to Cu to Ni to Pa and Mn may be about 25:37:10:15 and
13. Such a braze alloy may be available under the trade name
PALNICUROM.TM. 10. In one embodiment, the braze alloy may comprise
about 64% iron and about 36% nickel, which may be referred to as
Invar. In one embodiment, the braze material may comprise a
substantially unalloyed metal such as Co. In some embodiments, the
braze alloy may comprise at least one element selected from the
group consisting of Cr, Fe, Si, C, B, P, Mo, Ni, Co, W, and Pd. One
example of a suitable braze alloy may be available from Metglas.TM.
under the trade name MBF 15.
[0086] In some embodiments, the braze alloy may comprise at least
one of Cu, Ag or Au, and in some embodiments, the braze alloy may
further comprise at least one of Ti, V, Cr, Mn, Zr, Nb, Mo, Hf, Ta,
W or Re. For example, the braze alloy may contain Au and Ta, or the
braze alloy may contain Ag, Cu and Ti. In some embodiments, the
braze material may comprise at least one of Fe, Co, Ni or Mn.
[0087] In one embodiment of the invention, the method may include
coating a surface of the PCD structure to prepare it form brazing,
and then brazing the PCD structure to the substrate. Examples of
coatings for this purpose and methods of applying them are
described in U.S. Pat. Nos. 5,500,248; 5,647,8781; 5,529,805 and
PCT patent application publication number 2008/142657.
[0088] In one embodiment, the braze layer may contain dispersed
ceramic particles, and in one embodiment, the ceramic particles may
comprise a carbide material, such as silicon carbide, or a
super-hard material such as diamond. In some embodiments, the
ceramic particles may have mean size of less than about 20 microns
or less than about 10 microns. In some embodiments of the
invention, the presence of the ceramic particles in the braze layer
may to strengthen it and may reduce the likelihood of the composite
compact element failing as a result of the braze.
[0089] Embodiments of the invention may be used as gauge trimmers
on other types of earth-boring tools, such as cones of roller cone
drill bits, reamers, mills, bi-centre bits, eccentric bits, coring
bits and so-called hybrid bits that include both fixed cutters and
rolling cutters.
[0090] Grain contiguity may be determined from SEM images by means
of image analysis software. In particular, software having the
trade name analySIS Pro from Soft Imaging System.RTM. GmbH (a
trademark of Olympus Soft Imaging Solutions GmbH) may be used. This
software has a "Separate Grains" filter, which according to the
operating manual only provides satisfactory results if the
structures to be separated are closed structures. Therefore, it is
important to fill up any holes before applying this filter. The
"Morph. Close" command, for example, may be used or help may be
obtained from the "Fillhole" module. In addition to this filter,
the "Separator" is another powerful filter available for grain
separation. This separator can also be applied to colour- and
grey-value images, according to the operating manual.
[0091] As used herein, "transverse rupture strength" (TRS) is
measured by subjecting a specimen in the form of a disc to a load
applied at three points, two applied on one side of the specimen
and one applied on the opposite side, and increasing the load at a
loading rate until the specimen fractures. Such a measurement may
also be referred to as a three-point bending test, and has been
described by Borger et al. (Borger, A., P. Supansic and R. Danner,
"The ball on three balls test for strength testing of brittle
discs: stress distribution in the disc", Journal of the European
Ceramic Society, 2002, volume 22, pp. 1425-1436). With reference to
FIG. 12, a specimen 510 of the material to be tested is placed
between a load ball 520 and two support balls 530, and supported by
a guide body 570. The load ball 520 is supported by a stamp 560,
which is supported laterally and guided by a guide body 570, and a
chock 580 is disposed between respective parts of the guide body
570 and the stamp 560 and establishes a proximity limit to the
movement of the stamp 560 with respect to the guide body 570. A
punch 550 abuts support balls 530, which are disposed between the
punch 550 and the specimen 510. An axial load 540 is applied to the
punch 550 causing the load ball 520 and the support balls 530 to be
urged against the specimen 510 from opposite sides. The load is
increased at a certain loading rate from a lower limit until
evidence of fracture is observed in the specimen 510. As a
non-limiting example, an Instron.TM. 5500R universal testing
machine having a load cell of 10 KN may be used for measuring
transverse rupture strength as described above. The loading rate
may be about 0.9 mm/min. The transverse rupture strength .sigma. in
MPa is calculated as f(F).F/t.sup.2, where F is the measured load,
in Newtons, at which the specimen begins to fracture, t is the
thickness of the specimen and f(F) is a dimensionless constant
dependent on the load and the material being tested. In the case of
PCD, f(F)=1.620211-0.0082.times.(F-3000)/1000.
[0092] The specimen in the form of a round disc for use in the TRS
measurement described above is prepared as follows. A PCD
construction comprising a PCD structure joined to a substrate is
provided, the outer diameter of which is ground to 16 mm or 19 mm.
The substrate is removed, leaving a free-standing the PCD disc,
which is then lapped to a thickness in the range from about 1.30 mm
to about 2.00 mm. The PCD disc may be treated in acid to remove
some or substantially all of the material in the interstices
between the diamond grains.
[0093] The K1C toughness of a PCD disc is measured by means of a
diametral compression test, which is described by Lammer
("Mechanical properties of polycrystalline diamonds", Materials
Science and Technology, volume 4, 1988, p. 23.) and Miess (Miess,
D. and Rai, G., "Fracture toughness and thermal resistances of
polycrystalline diamond compacts", Materials Science and
Engineering, 1996, volume A209, number 1 to 2, pp. 270-276).
[0094] Embodiments of the invention are described in more detail
with reference to the examples below, which are not intended to
limit the invention.
Example 1
[0095] A PCD disc having thickness of about 2.2 millimetres and
diameter of about 16 mm was provided using a known high-pressure
high temperature method. The substrate to which the PCD was bonded
during the sintering step was removed by grinding, leaving an
un-backed, free-standing PCD disc. The PCD comprised coherently
bonded diamond grains having a multi-modal size distribution with
mean equivalent circle diameter of about 9 microns. Microstructural
data for the PCD is shown in Table 1, in which the mean grain size
is expressed in terms of equivalent circle diameter and the values
shown in parentheses are the respective standard deviations.
TABLE-US-00001 TABLE 1 Mean diamond grain size, Diamond content
Filler mean free Diamond grain microns of PCD, volume % path,
microns contiguity, % 9.0 (4.0) 91 (0.4) 0.6 (0.5) 62.0 (1.7)
[0096] The PCD disc was then treated (leached) in acid to remove
substantially all of the cobalt solvent/catalyst material
throughout the entire PCD structure.
[0097] Several additional discs, each having a diameter of about 19
mm, were made as described above and subjected to a range of tests
to measure mechanical properties. Mechanical properties of the PCD
discs after acid treatment are shown in Table 2, in which the
values shown in parentheses are the respective standard deviations.
It was found that the TRS of the PCD disc decreased from about
1,493 MPa before leaching to about 1,070 MPa after leaching (i.e.
by approximately 28%), and the Young's modulus decreased from about
1,025 GPa to about 864 GPa (i.e. by about 15% to 16%).
TABLE-US-00002 TABLE 2 Transverse rupture K.sub.1C toughness,
Young's strength, MPa MPa m.sup.1/2 modulus, GPa 1,070 (100) 6.8
(0.2) 864 (14)
[0098] A cobalt-cemented tungsten carbide substrate having
substantially the same diameter as the 16 mm PCD disc was provided.
A foil of active braze material having thickness of about 100
microns was sandwiched between the PCD disc and the substrate to
form a pre-compact element assembly. The braze material comprised
63.00% Ag, 32.25% Cu and 1.75% Ti, and is available under the trade
name of Cusil.TM. ABA. Prior to brazing, the PCD disc was
ultrasonically cleaned, and both the tungsten carbide substrate and
the braze foil was slightly ground and then ultrasonically
cleaned.
[0099] The pre-compact element assembly was subjected to heat
treatment in a vacuum. The temperature was increased to 920 degrees
centigrade over 15 minutes, held at this level for 5 minutes and
then reduced to ambient temperature over about 8 to 9 hours. A
vacuum of at least 10.sup.-5 millibar was maintained during the
heat treatment. Care was taken to avoid or minimise the amount of
oxygen and other impurities in the furnace environment.
Furthermore, a furnace with convection heating and low temperature
gradients was used because the components to be brazed and the
braze material should all reach the desired temperature in
relatively short time.
[0100] The molten braze material was found to infiltrate into the
PCD disc to a depth in the range from 10 to 20 microns, leaving a
braze layer of about 50 microns to about 80 microns between the PCD
and WC substrate. The shear strength of the braze bond was measured
to be in the range from 110 MPa to 150 MPa.
[0101] A control PCD composite compact element that had not been
detached from its original substrate and had not been treated in
acid was provided for comparison. The brazed and control composite
compacts were processed to form respective cutter elements and
subjected to a wear test involving using them to machine a granite
block mounted on a vertical turret milling apparatus. The test
result is expressed in terms of the depth of the wear scar at the
cutting edge of the compact element after a given number of passes.
The smaller the wear scar depth, the better. After 55 passes, the
wear scar depth of the compact element was about 3.5 mm, compared
to about 4 mm for the control element.
Example 2
[0102] A PCD compact element having a diameter of 16 mm was
prepared as described in Example 1, except that a different braze
material was used. The braze material comprised 70.5% Ag, 26.5% Cu
and 3.0% Ti, available under the trade name of CB4, and the brazing
step was carried out at a temperature of 950 degrees centigrade.
The molten braze material was found to infiltrate into the PCD disc
to a depth in the range from 5 to 10 microns. The shear strength of
the braze bond was found to be in the range from 110 MPa to 150
MPa.
[0103] The brazed compact element was subjected to a wear test as
described in Example 1. After 55 passes, the wear scar depth of the
compact element was about 2 mm.
Example 3
[0104] Example 1 was repeated, except that the PCD disc comprised
coherently bonded diamond grains having a multi-modal size
distribution with mean equivalent circle diameter of about 4.6
micrometres. Microstructural data for the PCD is shown in table
3.
TABLE-US-00003 TABLE 3 Mean diamond grain size, Diamond content
Filler mean free Diamond grain microns of PCD, volume % path,
microns contiguity, % 4.6 (1.3) 90.2 (0.3) 0.4 (0.3) 58.7 (1.7)
[0105] The PCD disc was then treated in acid to remove
substantially all of the cobalt solvent/catalyst material within
the interstices between the diamond grains, as is well known in the
art.
[0106] Several additional discs, each having a diameter of about 19
mm, were made as described above and subjected to a range of tests
to measure mechanical properties. Key mechanical properties of the
PCD after acid treatment are shown in table 4.
TABLE-US-00004 TABLE 4 Transverse rupture K.sub.1C toughness,
Young's strength, MPa MPa m.sup.1/2 modulus, GPa 1,200 (120) 7.8
(0.8) Not measured
[0107] The molten braze material was found to infiltrate into the
PCD disc to a depth in the range from about 10 microns to 20 about
microns. The shear strength of the braze bond was measured to be in
the range from 110 MPa to 150 MPa.
[0108] The brazed PCD compact element was subjected to a further
wear test, wherein the compact element was used to mill a block of
granite. After a cutting length of at least 6,000 millimetres, no
failure due to the braze joint was observed.
Example 4
[0109] PCD composite compact elements each comprising a layer of
PCD material having a diameter of 16 mm, in which the mean diamond
grain size was about 9 microns and the content of cobalt was about
9.0 volume % were provided by sintering the diamond grains onto
respective cemented carbide substrates at a pressure of about 5.5
GPa and a temperature of about 1400 degrees centigrade.
Microstructural data for the PCD is shown in Table 5, in which the
mean grain size is expressed in terms of equivalent circle
diameter.
TABLE-US-00005 TABLE 5 Mean diamond grain size, Diamond content
Filter mean free Diamond grain microns of PCD, volume % path,
microns contiguity, % 9.0 (4.0) 91 (0.4) 0.6 (0.5) 62.0 (1.7)
[0110] The substrates were removed from the PCD layers, which were
then treated in acid to remove substantially all of the cobalt
filler material. Inductively coupled plasma (ICP) analysis
confirmed the residual presence of about 2 weight %, which is about
1.1 volume % Co in the PCD structure. The residual cobalt may have
been trapped within substantially closed pores of the PCD
structure. Key mechanical properties of the PCD discs after acid
treatment are shown in Table 6, in which the values shown in
parentheses are the respective standard deviations. The oxidation
onset temperature of the PCD in this cutter was measured to be 870
degrees centigrade.
TABLE-US-00006 TABLE 6 Transverse rupture K.sub.1C toughness,
Young's strength, MPa MPa m.sup.1/2 modulus, GPa 831 5.6 (0.3)
844
[0111] A treated PCD structure was brazed onto a cemented tungsten
carbide substrate using an alloy comprising 70.5 weight % Ag, 26.5
weight % Cu and 3.0 weight % Ti, a formulation available under the
trade name CB4 from BrazeTec.TM.. The brazing was carried out in a
vacuum furnace, under a vacuum of 10.sup.-6 mbar, at 950 degrees
centigrade for about 5 minutes. The shear strength of the braze
bond between the PCD structure and the substrate was about 287 MPa
at room temperature and about 224 MPa at 300 degrees
centigrade.
[0112] A control PCD composite compact element that had not been
detached from its original substrate and had not been treated in
acid was provided for comparison. The brazed compact and the
control composite compacts were processed to form respective cutter
elements and subjected to a wear test involving using them to
machine a granite block mounted on a vertical turret milling
apparatus. The test result can be expressed in terms of the depth
of the wear scar or area of wear scar at the cutting edge of the
compact element after a given number of passes. The smaller the
wear scar depth or area, the better. After 55 passes, the wear scar
area of the example compact element was about 5.2 mm.sup.2,
compared to about 18.9 mm.sup.2 for the control element.
Example 5
[0113] PCD structures in the form of discs having a diameter of 16
mm and in which the diamond grains had a mean size of about 9
microns were manufactured by sintering the grains onto respective
substrates at a pressure of about 6.8 GPa and a temperature of
about 1,400 degrees centigrade. Microstructural data for the PCD is
shown in Table 7, in which the mean grain size is expressed in
terms of equivalent circle diameter.
TABLE-US-00007 TABLE 7 Mean diamond grain size, Diamond content
Filler mean free Diamond grain microns of PCD, volume % path,
microns contiguity, % 9 (4) 91.4 (0.4) 0.7 (0.6) 63.0 (1.5)
[0114] The substrates were removed and the PCD structures were
treated in acid to remove substantially all of the cobalt filler
material. Key mechanical properties of the PCD discs after acid
treatment are shown in Table 8, in which the values shown in
parentheses are the respective standard deviations.
TABLE-US-00008 TABLE 8 Transverse rupture K.sub.1C toughness,
Young's strength, MPa MPa m.sup.1/2 modulus, GPa 983 Not measured
927
[0115] A treated PCD disc was brazed onto a cemented tungsten
carbide substrate using an alloy comprising 70.5 weight % Ag, 26.5
weight % Cu and 3.0 weight % Ti, a formulation available under the
trade name CB4 from BrazeTec.TM., as described in Example 4.
[0116] The brazed compact was processed to form a cutter element
and subjected to a wear test involving using it to machine a
granite block mounted on a vertical turret milling apparatus. The
test result can be expressed in terms of the depth of the wear scar
or area of wear scar at the cutting edge of the compact element
after a given number of passes. The smaller the wear scar depth or
area, the better. After 55 passes, the wear scar area of the
example compact element was about 3.26 mm.sup.2, compared to about
18.9 mm.sup.2 for the control element described in Example 4.
Example 6
[0117] PCD structures in the form of discs having a diameter of 16
mm and in which the diamond grains had a mean size of about 4
microns and which contained about 10 volume % cobalt, were
manufactured by sintering the grains onto respective substrates at
a pressure of about 5.5 GPa and a temperature of about 1,400
degrees centigrade. Microstructural data for the PCD is shown in
Table 9, in which the mean grain size is expressed in terms of
equivalent circle diameter.
TABLE-US-00009 TABLE 9 Mean diamond grain size, Diamond content
Filler mean free Diamond grain microns of PCD, volume % path,
microns contiguity, % 4.2 (1.6) 89.2 (0.5) 0.4 (0.3) 65 (1)
[0118] The substrate was removed and the PCD structure was treated
in acid to remove substantially all of the cobalt filler material.
Key mechanical properties of the PCD disc after acid treatment are
shown in Table 8, in which the values shown in parentheses are the
respective standard deviations.
TABLE-US-00010 TABLE 10 Transverse rupture K.sub.1C toughness,
Young's strength, MPa MPa m.sup.1/2 modulus, GPa 1,058 6.9 846
[0119] The treated PCD disc was brazed onto a cemented tungsten
carbide substrate using an alloy comprising 70.5 weight % Ag, 26.5
weight % Cu and 3.0 weight % Ti, a formulation available under the
trade name CB4 from BrazeTec.TM., as described in Example 4.
[0120] A control PCD composite compact element that had not been
detached from its original substrate and had not been treated in
acid was provided for comparison. The brazed and control composite
compacts were processed to form respective cutter elements and
subjected to a wear test involving using them to machine a granite
block mounted on a vertical turret milling apparatus. The test
result can be expressed in terms of the depth of the wear scar or
area of wear scar at the cutting edge of the compact element after
a given number of passes. The smaller the wear scar depth or area,
the better. After 55 passes, the wear scar area of the example
compact element was about 3.33 mm.sup.2, compared to about 4.09
mm.sup.2 for the control element.
Example 7
[0121] PCD structures in the form of discs, in which the diamond
grains had a mean size of about 4 microns and containing about 10
volume % cobalt, were manufactured by sintering the grains onto
respective substrates at a pressure of about 6.8 GPa and a
temperature of about 1,400 degrees centigrade. Microstructural data
for the PCD is shown in Table 11, in which the mean grain size is
expressed in terms of equivalent circle diameter.
TABLE-US-00011 TABLE 11 Mean diamond Diamond content Diamond grain
grain size, of PCD, volume Filler mean free contiguity, microns
percent path, microns percent 4.3 (1.2) 89 (1) 1 (1.6) 57.8 (1)
[0122] The substrates were removed and the PCD structures were
treated in acid to remove substantially all of the cobalt filler
material.
[0123] A treated PCD was brazed onto a cemented tungsten carbide
substrate using an alloy comprising 70.5 weight % Ag, 26.5 weight %
Cu and 3.0 weight % Ti, a formulation available under the trade
name CB4 from BrazeTec.TM., as described in Example 4.
[0124] The brazed composite compact was processed to form a utter
element and subjected to a wear test involving using it to machine
a granite block mounted on a vertical turret milling apparatus. The
test result can be expressed in terms of the depth of the wear scar
or area of wear scar at the cutting edge of the compact element
after a given number of passes. The smaller the wear scar depth or
area, the better. After 55 passes, the wear scar area of the
example compact element was about 3.28 mm.sup.2, compared to about
4.09 mm.sup.2 for the control element described in Example 6.
Example 8
[0125] PCD discs were provided and treated as described in Example
4, and a treated PCD disc was brazed onto a cemented tungsten
carbide substrate using a braze alloy comprising 86.0 weight % Cu,
12.0 weight % Mn and 2.0 weight % Ni at 1050 degrees centigrade for
about 5 minutes in vacuum. The braze material was available as
21/80 from BrazeTec.TM..
[0126] The brazed composite compact was processed to form a cutter
element and subjected to a wear test involving using it to machine
a granite block mounted on a vertical turret milling apparatus. The
test result can be expressed in terms of the depth of the wear scar
or area of wear scar at the cutting edge of the compact element
after a given number of passes. The smaller the wear scar depth or
area, the better. After 55 passes, the wear scar area of the
example compact element was about 3.65 mm.sup.2, compared to about
18.9 mm.sup.2 for the control element described in Example 4.
Example 9
[0127] PCD discs were provided and treated as described in Example
4, and a treated disc was glued onto a cemented tungsten carbide
substrate using Permabond ES550.TM. epoxy resin at about 100
degrees centigrade for about 2 hours.
[0128] The brazed and control composite compact was processed to
form a cutter element and subjected to a wear test involving using
it to machine a granite block mounted on a vertical turret milling
apparatus. The test result can be expressed in terms of the depth
of the wear scar or area of wear scar at the cutting edge of the
compact element after a given number of passes. The smaller the
wear scar depth or area, the better. After 55 passes, the wear scar
area of the example compact element was about 4.44 mm.sup.2,
compared to about 18.9 mm.sup.2 for the control element described
in Example 4.
Example 10
[0129] A PCD disc was provided and treated as described in Example
4, and was brazed onto a cemented tungsten carbide substrate using
a braze alloy comprising 68.8 weight % Ag, 26.7 weight % Cu and 4.5
weight % Ti alloy at about 950 centigrade for about 5 minutes in
vacuum. The braze material was available under the product name
Ticusil.TM. from Wesgo.TM..
Example 11
[0130] A PCD disc was provided and treated as described in Example
4, and was brazed onto a cemented tungsten carbide substrate using
a braze alloy comprising 68.8 weight % Ag, 26.7 weight % Cu and 4.5
weight % Ti alloy at about 950 centigrade for about 5 minutes in an
argon atmosphere. The braze material was available under the
product name Ticusil.TM. from Wesgo.TM.. The shear strength of the
braze bond was about resultant cutting element had bond shear
strength of 215 MPa at room temperature.
[0131] Known PCD composite compact elements comprising PCD
structures brazed to substrates have lacked commercially success,
particularly in harsh applications such as drilling into rock,
especially in the oil and gas drilling industry. Such applications
require cutter compact elements capable of maintaining extreme
abrasion resistance and high strength at high temperatures
experienced in use, typically in excess of 600 degrees centigrade.
While wanting not to be bound by theory, brazing of PCD to carbide
may give rise to high internal stresses within the compact element
proximate the braze interface, resulting in cracking of the PCD
and/or the substrate or the delamination of the PCD even before the
compact element is used to bore into rock. Embodiments of PCD
composite compact elements according to the invention, particularly
embodiments in which the PCD structure is thermally stable may be
economically viable and commercially successful.
[0132] Embodiments of the invention in which the PCD structure has
a mean Young's modulus of at least about 800 GPa may better retain
its mechanical integrity and robustness after being bonded to the
substrate. If the Young's modulus is substantially less than about
800 GPa, or if the transverse rupture strength is substantially
less than about 900 MPa, the PCD structure may not be able to cut
rock efficiently and may wear too rapidly. Embodiments of PCD that
have a homogeneous microstructure, characterised in terms of the
combination of the interstitial mean free path and the standard
deviation of the interstitial mean free path, may have enhanced
resistance to mechanical and thermal stress and shock, as may be
experience when brazing the PCD to a substrate and using the
composite compact to degrade or bore into rock.
[0133] Embodiments having the combination of the high contiguity
and/or high homogeneity and/or reduced content of metallic
solvent/catalyst within the PCD structure, and a size distribution
comprising at least two or three peaks or modes, have the advantage
of bonding particularly well using conventional brazing.
Embodiments may exhibit superior durability over prior art cutter
elements comprising PCD brazed to a substrate.
[0134] Embodiments of the invention may have the advantage that the
strength with which the PCD structure is bonded to the substrate
may be substantially enhanced. In particular, embodiments in which
the PCD structure is brazed to the substrate and in which the PCD
structure contains braze material to a depth of at least about 2
microns from an interface with the braze layer may have exhibit a
particularly enhanced strength of bonding. Consequently, the
mechanical properties and working life of such embodiments may be
enhanced, particularly when used to bore into rock.
[0135] Embodiments of the invention in which the shear strength of
the bond between the PCD structure and the substrate is at least
about 100 MPa and at most about 500 MPa, may have the advantage
that conventional brazing methods may be adequate.
[0136] Embodiments of the invention in which the PCD structure is
thermally stable may have the advantage that the PCD structure
better retains its structural integrity and key mechanical
properties after being bonded to the substrate by means of a method
involving heating the PCD structure, such as brazing. Embodiments
of the invention in which the PCD structure has a filler comprising
carbide or inter-metallic compounds may have enhanced thermal
stability and better retain key mechanical properties after being
bonded to the substrate, such as by brazing.
[0137] Embodiments of the invention in which the substrate
comprises cemented carbide and includes diamond particles dispersed
in it may have enhanced mechanical robustness, particularly
fracture resistance.
[0138] Embodiments of the invention in which the PCD structure
comprises at least 90 volume percent diamond grains having a mean
size of at most about 10 microns may be especially advantageous.
Embodiments of PCD structures having a multi-modal diamond grain
size distribution have sufficient strength to retain better their
mechanical integrity and key properties after bonding to the
substrate, such as by brazing.
[0139] Embodiments of the invention may have the advantage that the
composition of the PCD structure, particularly the composition of
the filler material, may be selected with fewer constraints
associated with the composition of the substrate. PCD structures
having desirable properties, particularly high thermal stability,
can be made separately from the substrate and then bonded to the
substrate using known brazing materials and methods, thereby
improving the performance of the PCD tool without incurring
substantial additional costs.
[0140] Although the foregoing description of PCD composite compact
element, tools, manufacturing methods and various applications
contain many specific details, these should not be construed as
limiting the scope of the invention, but merely as providing
illustrations of some example embodiments. Similarly, other
embodiments of the invention may be devised which do not depart
from the spirit or scope of the present invention. The scope of the
invention is indicated and limited only by the appended claims and
their legal equivalents, rather than by the foregoing description.
All additions, deletions, and modifications to the invention, as
disclosed herein, which fall within the meaning and scope of the
claims are to be embraced.
* * * * *