U.S. patent application number 16/733099 was filed with the patent office on 2020-05-14 for polycrystalline diamond.
The applicant listed for this patent is Element Six Limited Baker Hughes Incorporated. Invention is credited to Michael Lester FISH, Bronwyn Annette KAISER, John Hewitt LIVERSAGE, Kaveshini NAIDOO, Danny Eugene SCOTT, Humphrey Samkelo Lungisani SITHEBE.
Application Number | 20200147759 16/733099 |
Document ID | / |
Family ID | 42154253 |
Filed Date | 2020-05-14 |
United States Patent
Application |
20200147759 |
Kind Code |
A1 |
LIVERSAGE; John Hewitt ; et
al. |
May 14, 2020 |
POLYCRYSTALLINE DIAMOND
Abstract
An embodiment of a PCD insert comprises an embodiment of a PCD
element joined to a cemented carbide substrate at an interface. The
PCD element has internal diamond surfaces defining interstices
between them. The PCD element comprises a masked or passivated
region and an unmasked or unpassivated region, the unmasked or
unpassivated region defining a boundary with the substrate, the
boundary being the interface. At least some of the internal diamond
surfaces of the masked or passivated region contact a mask or
passivation medium, and some or all of the interstices of the
masked or passivated region and of the unmasked or unpassivated
region are at least partially filled with an infiltrant
material.
Inventors: |
LIVERSAGE; John Hewitt;
(Springs, ZA) ; SCOTT; Danny Eugene; (Houston,
TX) ; SITHEBE; Humphrey Samkelo Lungisani; (Springs,
ZA) ; NAIDOO; Kaveshini; (Springs, ZA) ;
KAISER; Bronwyn Annette; (Springs, ZA) ; FISH;
Michael Lester; (Springs, ZA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Element Six Limited
Baker Hughes Incorporated |
County Clare
Houston |
TX |
IE
US |
|
|
Family ID: |
42154253 |
Appl. No.: |
16/733099 |
Filed: |
January 2, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15052481 |
Feb 24, 2016 |
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16733099 |
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13254643 |
Nov 10, 2011 |
9297213 |
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PCT/IB2010/050975 |
Mar 8, 2010 |
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15052481 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C04B 41/81 20130101;
C04B 35/645 20130101; C04B 2237/61 20130101; C04B 2235/428
20130101; B24D 18/0027 20130101; C22C 26/00 20130101; E21B 10/56
20130101; C04B 2235/80 20130101; C04B 41/4529 20130101; C04B 41/88
20130101; B24D 18/0009 20130101; C04B 35/52 20130101; C04B 2235/402
20130101; C04B 2235/3826 20130101; B22F 2999/00 20130101; C04B
35/6316 20130101; C04B 2235/786 20130101; C04B 37/021 20130101;
C04B 2235/3817 20130101; C04B 2235/6567 20130101; B22F 2999/00
20130101; E21B 10/5735 20130101; B22F 2005/001 20130101; C04B
2237/363 20130101; C04B 2235/616 20130101; C04B 2235/783 20130101;
C04B 41/4523 20130101; C04B 2237/60 20130101; C04B 2237/401
20130101; C22C 26/00 20130101; C04B 2235/656 20130101; B22F 2207/03
20130101 |
International
Class: |
B24D 18/00 20060101
B24D018/00; E21B 10/56 20060101 E21B010/56; C04B 41/88 20060101
C04B041/88; C04B 41/81 20060101 C04B041/81; C04B 41/45 20060101
C04B041/45; E21B 10/573 20060101 E21B010/573; C22C 26/00 20060101
C22C026/00; C04B 37/02 20060101 C04B037/02; C04B 35/645 20060101
C04B035/645; C04B 35/63 20060101 C04B035/63; C04B 35/52 20060101
C04B035/52 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 6, 2009 |
GB |
0903822.5 |
Mar 6, 2009 |
GB |
0903834.0 |
Claims
1. A method for manufacturing a PCD element; the method including
providing a PCD body having internal diamond surfaces, the internal
diamond surfaces defining interstices, the PCD body containing a
thermally stable region and a porous region, in which at least some
of the interstices contain at least partly unfilled pores;
introducing a mask or passivation medium proximate or into the
thermally stable region; and introducing at least one infiltrant
material into the porous region, the mask or passivation medium at
least partly isolating diamond of the thermally stable region from
chemical interaction with the at least one infiltrant material,
wherein a controlled temperature cycle is employed in such a manner
as to allow sufficient or a certain amount of the mask or
passivation medium or its precursor to be introduced proximate or
into the thermally stable region prior to the at least one
infiltrant material melting and infiltrating into the porous PCD
body.
2. A method as claimed in claim 1, in which the thermally stable
region is at least partly porous.
3. A method as claimed in claim 1, the method including coating
some or all of the internal diamond surfaces of the thermally
stable region, at least partially, with a mask or passivation
medium.
4. A method as claimed in claim 1, the method including chemically
isolating diamond from chemical interaction with the infiltrant
material.
5. A method as claimed in claim 1, in which the PCD body is porous
throughout.
6. A method for manufacturing a PCD element; the method including
providing a PCD body having internal diamond surfaces, the internal
diamond surfaces defining interstices, the PCD body containing a
thermally stable region and a porous region, in which at least some
of the interstices contain at least partly unfilled pores;
introducing a mask or passivation medium proximate or into the
thermally stable region; and thereafter introducing at least one
infiltrant material into the porous region, the mask or passivation
medium at least partly isolating diamond of the thermally stable
region from chemical interaction with the at least one infiltrant
material.
7. A method as claimed in claim 1, the method including introducing
the mask or passivation medium under HPHT conditions.
8. A method for manufacturing a PCD element; the method including
providing a PCD body having internal diamond surfaces, the internal
diamond surfaces defining interstices, the PCD body containing a
thermally stable region and a porous region, in which at least some
of the interstices contain at least partly unfilled pores;
introducing a mask or passivation medium proximate or into the
thermally stable region; and introducing at least one infiltrant
material into the porous region, the mask or passivation medium at
least partly isolating diamond of the thermally stable region from
chemical interaction with the at least one infiltrant material, the
mask or passivation medium being introduced proximate or into the
thermally stable region under conditions other than HPHT
conditions.
9. A method as claimed in claim 8, the method including introducing
the mask or passivation medium in a gas or vapour phase, as an
inert salt or ceramic phase, or using surface chemistry
modification of the internal diamond surfaces in the masked or
passivated region.
10. A method as claimed in claim 9, the method including
introducing the mask or passivation medium by atomic layer
deposition, infiltration with a liquid pre-ceramic polymer or
polymer solution, using a sol gel or other solution-based chemical
route, or a vapour comprising a metal composition.
11. A method as claimed in claim 10, the method including
introducing tungsten hexafluoride as a vapour, thereby to deposit
tungsten as the mask or passivation medium.
12. A method as claimed in claim 1, the method including
introducing the infiltrant material into a volume of the PCD body,
the volume being at least about 10 percent of the total volume of
the PCD body.
13. A method as claimed in claim 1, the method including
introducing the infiltrant material into a volume of the PCD body
that is proximate a surface of the PCD body, the surface being
remote from or opposing the interface, the volume having a depth
from the surface of at least about 0.1 mm.
14. A method as claimed in claim 1, in which the masked or
passivated region defines a barrier between the thermally stable
region and the infiltrant material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 15/052,481, filed Feb. 24, 2016 which is a continuation of U.S.
application Ser. No. 13/254,643 filed Nov. 10, 2011, which is a
.sctn.371 filing from PCT Application PCT/IB2010/050975 filed Mar.
8, 2010, which claims priority to GB Application No. 0903822.5
filed Mar. 6, 2009 and to GB Application No. 0903834.0 filed Mar.
6, 2009, each of which are hereby incorporated by reference in
their entirety.
FIELD
[0002] This invention relates to polycrystalline diamond (PCD)
elements, bodies and tool inserts, particularly for use in tools
for boring into the earth, and to a method for making PCD
elements.
BACKGROUND
[0003] Cutter inserts for drill bits for use in boring into the
earth may comprise a layer of polycrystalline diamond (PCD) bonded
to a cemented carbide substrate. Such cutter inserts may be
referred to as polycrystalline diamond compacts (PDC).
[0004] PCD is an example of a superhard, also called superabrasive,
material comprising a mass of substantially inter-grown diamond
grains, forming a skeletal mass defining interstices between the
diamond grains. PCD material comprises at least about 80 volume %
of diamond and may be made by subjecting an aggregated mass of
diamond grains to an ultra-high pressure of greater than about 5
GPa and temperature of at least about 1,200 degrees centigrade in
the presence of a sintering aid.
[0005] Suitable sintering aids for PCD may also be referred to as a
catalyst material for diamond. Catalyst material for diamond is
understood to be material that is capable of promoting direct
inter-growth of diamond grains at a pressure and temperature
condition at which diamond is thermodynamically more stable than
graphite. Some catalyst materials for diamond may promote the
conversion of diamond to graphite at ambient pressure, particularly
at elevated temperatures. Examples of catalyst materials for
diamond are cobalt, iron, nickel and certain alloys including any
of these. PCD may be formed on a cobalt-cemented tungsten carbide
substrate, which may provide a source of cobalt catalyst material
for the PCD. The interstices with PCD may be at least partly be
filled with a material, which may be referred to as a binder or a
filler material. In particular the interstices may be wholly or
partially filled with catalyst material for diamond.
[0006] Components comprising PCD are 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 bodies are commonly
used as cutter inserts on drill bits used for boring into the earth
in the oil and gas drilling industry. PCD bodies are also used for
machining and milling metal-containing bodies, such as may be used
in the auto manufacturing industry. In many of these applications
the temperature of the PCD material becomes elevated as it engages
a rock formation, workpiece or body with high energy.
[0007] PCD is extremely hard and abrasion resistant, which is the
reason it is the preferred tool material in some of the most
extreme machining and drilling conditions, and where high
productivity is required. A disadvantage of PCD containing certain
catalyst materials for diamond as a filler material may be its
relatively poor thermal stability above about 400 degrees
centigrade. The catalyst material may promote the degradation of
the PCD at elevated temperature, particularly at temperatures
greater than about 750 degrees centigrade, as may be experienced in
manufacture and use of PCD compacts.
[0008] U.S. Pat. No. 7,377,341 discloses thermally stable
ultra-hard compact constructions comprising a body formed from an
ultra-hard material such as PCD, including a thermally stable
region positioned adjacent a working surface of the body. The
ultra-hard material body can be attached to a desired substrate,
thereby forming a compact, and an intermediate material can be
interposed between the substrate and the body. The intermediate
material may be one that does not infiltrate into the ultra-hard
material body during high pressure/high temperature processing and
that can operate as a barrier to prevent migration of constituent
materials from the substrate to the ultra-hard material body.
[0009] U.S. Pat. No. 7,473,287 discloses thermally-stable
polycrystalline diamond materials comprising a first material phase
that includes a plurality of bonded together diamond crystals, and
a second material phase that includes a reaction product formed
between a binder/catalyst material used to facilitate diamond
crystal bonding and a material that is reactive with the
binder/catalyst material. A barrier layer may be placed between PCD
material and a substrate to prevent unwanted infiltration of extra
cobalt therein which could adversely impact the thermal stability
of the resultant PCD material.
[0010] U.S. patent application publication number 2007/0079994
discloses thermally stable diamond-bonded compacts that include a
diamond-bonded body comprising a thermally stable region that
extends a distance below a diamond-bonded body surface. The
thermally stable region has a material microstructure comprising a
matrix first phase of bonded together diamond crystals, and a
second phase interposed within the matrix first phase. The second
phase comprises one or more reaction products formed between one or
more infiltrant material and the diamond crystals at high
pressure/high temperature (HPHT) conditions. The infiltrant or
replacement material may include one or more of the following
elements: Si, Cu, Sn, Zn, Ag, Au, Ti, Cd, Al, Mg, Ga, Ge, which may
also be used in compounds containing conventional solvent-catalyst
materials (transition metals) where the solvent catalyst is
rendered inactive by reaction with another material.
[0011] U.S. patent application publication number 2008/0115421
discloses a method of fabricating a superabrasive article, in which
at least a portion of interstitial regions of a
pre-sintered-polycrystalline-diamond body may be infiltrated with
silicon from a silicon-containing material. At least a portion of
metal-solvent catalyst located within the at least a portion of
interstitial regions of the pre-sintered-polycrystalline-diamond
body may be displaced into a porous mass. The silicon and the
pre-sintered-polycrystalline-diamond body are reacted to form
silicon carbide within the at least a portion of the interstitial
regions.
[0012] There is a need to provide a polycrystalline diamond (PCD)
element having enhanced thermal stability. There is also a need to
provide a PCD element having enhanced thermal stability combined
with enhanced resistance to fracture.
SUMMARY
[0013] A purpose of the invention is to provide a polycrystalline
diamond (PCD) element having enhanced thermal stability, and a
further purpose of the invention is to provide a method for making
same.
[0014] A first aspect of the invention provides a polycrystalline
diamond (PCD) element having internal diamond surfaces, the
internal diamond surfaces defining interstices between them; the
PCD element comprising a masked or passivated region and an
unmasked or unpassivated region, the unmasked or unpassivated
region defining a boundary with another region or body, and
extending a depth of between about 5 microns and about 600 microns
from the boundary, in which at least some of the internal diamond
surfaces of the masked or passivated region contact a mask or
passivation medium, and wherein some or all of the interstices of
the masked or passivated region and of the unmasked or unpassivated
region are at least partially filled with an infiltrant
material.
[0015] In one embodiment, the PCD element is bonded to a substrate
at an interface and the unpassivated or unmasked region is adjacent
the interface. In some embodiments, the boundary defined by the
unmasked or unpassivated region is the interface between the PCD
element and the substrate, the unmasked or unpassivated region
extending a depth from the interface, the depth being at most about
400 microns, at most about 200 microns, at most about 100 microns,
at most about 50 microns, at most about 10 microns or even at most
about 5 microns. In some embodiments, the unmasked or unpassivated
region extends a depth into the PCD element from the interface
between the PCD element and the substrate, the depth being at least
about 5 microns, at least about 10 microns, at least about 50
microns, at least about 100 microns, or even at least about 200
microns.
[0016] In one embodiment, at least some of the internal diamond
surfaces of the masked or passivated region are coated with a mask
or passivation medium.
[0017] In one embodiment, some or all of the interstices of the
masked or passivated region and of the unmasked or unpassivated
region are at least partially filled with an infiltrant material
having substantially the same composition.
[0018] In one embodiment, the thermally stable region is proximate
a peripheral surface of the PCD element. In one embodiment, the PCD
element has a peripheral surface and a generally annular region
adjacent the peripheral surface, at least part of the annular
region being thermally stable and being masked or passivated.
[0019] In one embodiment, the infiltrant material comprises a
catalyst material for diamond, and in one embodiment, the catalyst
material comprises cobalt, iron or nickel, or an alloy including
any of these elements. In one embodiment, the infiltrant comprises
a material that is not a catalyst material for diamond, and in some
embodiments the infiltrant material comprises silicon or
aluminium.
[0020] In some embodiments, the mask or passivation medium
comprises an inert salt, ceramic precursor material, organometallic
precursor material or carbonaceous material. In some embodiments,
the mask or passivation medium is a ceramic material selected from
silicon carbide, titanium carbide, tantalum carbide, tungsten
carbide, hafnium carbide, molybdenum carbide, zirconium carbide,
vanadium carbide and aluminium carbide. In one embodiment, the mask
or passivation medium, or at least a portion thereof, is formed by
reaction of a mask or passivation precursor material and diamond
from the internal diamond surfaces. In some embodiments, the mask
or passivation precursor material comprises silicon, titanium,
tantalum, tungsten, hafnium, molybdenum, zirconium, vanadium or
aluminium. In some embodiments, remnants of the mask or passivation
precursor material remain within interstices of the PCD element and
may also function as mask or passivation media.
[0021] In some embodiments, the interstices within the masked or
passivated region are least about 50 percent, at least about 70
percent, at least about 80 percent or even at least about 90
percent filled with silicon carbide or aluminium carbide.
[0022] In one embodiment, at least 40 percent of the total surface
area of the internal diamond surfaces of the masked or passivated
region is coated with the mask or passivation medium.
[0023] In one embodiment, the masked or passivated region is
located adjacent a working surface or peripheral surface, or both,
of the PCD element.
[0024] In some embodiments, the masked or passivated region extends
a depth into the PCD element from a working surface, the depth
being at most about 1,000 microns, at most about 500 microns or at
most about 100 microns. In some embodiments, the masked or
passivated region extends a depth into the PCD element from a
working surface, the depth being at least about 5 microns, at least
about 10 microns, at least about 50 microns, at least about 100
microns, or even at least about 200 microns.
[0025] In one embodiment, the thermally stable region is in the
form of a stratum or layer. In some embodiments, the masked or
passivated region is in the form of a layer or stratum that extends
to a depth of at least about 40 microns, at least about 100 microns
or even at least about 200 microns from a working surface.
[0026] Embodiments of the invention may have the advantage of
enhanced thermal stability combined with enhanced resistance to
fracture, which may result from reduced residual stresses.
[0027] In one embodiment, the infiltrant material is dispersed
through at least some of the masked or passivated region and is
chemically substantially isolated from and substantially unable to
interact chemically with the PCD by the coated mask or passivation
medium.
[0028] In one embodiment, the masked or passivated region and the
thermally stable region overlap each other. In one embodiment, the
masked or passivated region is contiguous with the thermally stable
region of the PCD element.
[0029] In one embodiment, the PCD element comprises a thermally
stable region that is separated from a region of the PCD element
containing a catalyst material by a barrier, the barrier comprising
a mask or passivation medium.
[0030] In one embodiment, the barrier is in the form of a stratum
or layer.
[0031] In one embodiment, the PCD element is joined to a substrate
and the region containing a catalyst material is adjacent the
substrate.
[0032] In one embodiment, the porous region extends throughout the
PCD element.
[0033] Embodiments of the invention have the advantage of enhanced
thermal stability. Embodiments of the invention have the advantage
of enhanced thermal stability and reduced internal stress, both of
which alone or in combination may extend the working life of the
PCD compact.
[0034] A second aspect of the invention provides a method for
manufacturing a PCD element; the method including providing a PCD
body having internal diamond surfaces, the internal diamond
surfaces defining interstices, the PCD body containing a thermally
stable region and a porous region, in which at least some of the
interstices contain at least partly unfilled pores; introducing a
mask or passivation medium proximate or into the thermally stable
region; and introducing at least one infiltrant material into the
porous region, the mask or passivation medium at least partly
isolating diamond of the thermally stable region from chemical
interaction with the at least one infiltrant material.
[0035] In one embodiment of the invention, a controlled temperature
cycle is employed in such a manner as to allow sufficient or a
certain amount of the mask or passivation medium or its precursor
to be introduced proximate or into the thermally stable region
prior to the at least one infiltrant material melting and
infiltrating into the porous PCD body.
[0036] In one embodiment, the thermally stable region is at least
partly porous, and in one embodiment, the porous region and the
thermally stable region wholly or partially overlap, occupying a
common volume within the PCD body. In one embodiment, the thermally
stable region is at least partly porous and the method includes
introducing the mask or passivation medium by filling part or the
majority of the pores with the mask or passivation medium.
[0037] In one embodiment, the method includes introducing mask or
passivation material into part or the majority of a porous region
disposed adjacent a thermally stable region, the mask or
passivation material functioning as a barrier to infiltrant
material, and then introducing an infiltrant material into the PCD
body; the mask or passivation materials preventing the infiltrant
material from interacting with the thermally stable region.
[0038] In one embodiment, the method includes coating some or
substantially all of the internal diamond surfaces of the thermally
stable region, at least partially, with a mask or passivation
medium such as an inert material in order to mask or passivate the
thermally stable region, in whole or in part.
[0039] In one embodiment, the method includes substantially
chemically isolating diamond from chemical interaction with the
infiltrant material.
[0040] In one embodiment, the method includes introducing the
infiltrant material into the polycrystalline diamond body
simultaneously with introducing the mask or passivation medium
proximate or into the thermally stable region. In one embodiment,
the method includes introducing the mask or passivation medium
proximate or into the thermally stable region and then introducing
the infiltrant material into the polycrystalline diamond body. In
one embodiment, the infiltrant material is introduced into a volume
of the PCD body, the volume being at least 10 percent of the total
volume of the PCD body.
[0041] In one embodiment, the polycrystalline diamond body is
integrally bonded to a substrate, which may comprise a cemented
carbide material, during the same step in which infiltrant material
is introduced, and in one embodiment, the substrate provides the
source of the infiltrant material, which may comprise cobalt.
[0042] In one embodiment, the PCD body is joined at an interface to
a substrate comprising cemented tungsten carbide, and in one
embodiment, the infiltrant material is introduced into a volume of
the PCD body that is proximate a surface of the PCD body, the
surface being remote from or opposing the interface, the volume
having a depth from the surface of at least about 0.1 mm.
[0043] In one embodiment, the method includes removing catalyst
material from interstices of a PCD body. In one embodiment, the
thermally stable region is devoid or substantially devoid of
catalyst material.
[0044] In one embodiment, the infiltrant material is a catalyst
material. More preferably the infiltrant material comprises cobalt,
iron or nickel, or an alloy including any of these elements.
[0045] In one embodiment, the method includes removing catalyst
material from substantially the entire volume of the PCD body,
thereby providing a thermally stable PCD body that is porous
throughout.
[0046] Embodiments of the method of the invention have the
advantage of permitting a PCD body to be infiltrated with a
catalyst material without substantially reducing the thermal
stability of the thermally stable region.
[0047] In an embodiment of the method in which the PCD body is
joined to a substrate during the infiltration step, catalyst
material such as cobalt within the substrate may infiltrate into
pores within the PCD body, which may promote the formation of a
strong bond between the PCD body and substrate.
[0048] Embodiments of the method of the invention have the
advantage of producing PCD compacts having both enhanced thermal
stability and reduced internal stress, which may extend the working
life of the PCD compact. The infiltration of catalyst material to a
depth within the PCD body may reduce the internal stress that may
be generated when two bodies having very different
thermo-mechanical properties are bonded together. Mere
surface-to-surface bonding of a thermally stable diamond body to a
cemented carbide substrate may result in significant
thermo-mechanical stresses proximate the interface between them,
which may lead to failure of the compacts both during manufacturing
and in use, making such compacts uneconomical.
[0049] Embodiments of the method that include coating the internal
diamond surfaces of the PCD body in the masked or passivated region
have the advantage that a generally porous microstructure may be
retained. This may allow for infiltration of infiltrant material
into the porous microstructure whilst keeping catalyst material
isolated from the thermally stable region. This may preserve the
thermal stability of at least part of the PCD body.
[0050] Embodiments of the method of the invention have the
advantage that the nature and type of carbide substrate used in the
final product may be different from that used in the manufacture of
the starting PCD body. This may permit the use of a substrate most
suitable for sintering the starting PCD body, and then the use of a
different substrate that may be more suitable for the finished
product. In other words, the substrate of embodiments of the final
product is not limited to that used for sintering the PCD body and
may be selected to have better properties for use in a given
application.
[0051] A third aspect of the invention provides a PCD insert for a
tool, the insert comprising an embodiment of a PCD element
according to the invention.
[0052] A fourth aspect of the invention provides a tool comprising
an embodiment of an insert according to an aspect of the
invention.
[0053] In some embodiments, the tool is for machining, drilling,
boring, cutting or otherwise forming or degrading a hard or
abrasive workpiece or other body, such as rock, concrete, asphalt,
metal or hard composite materials. In some embodiments, the tool is
a drill bit for use in earth boring, rock drilling or rock
degradation, as may be used in the oil and gas drilling and mining
industries. In one embodiment, the tool is a rotary drag bit for
use in earth-boring and rock drilling in the oil and gas
industry.
[0054] A fifth aspect of the invention provides a rotary drill bit
containing a plurality of PCD inserts, each comprising a respective
embodiment of a PCD element according to the invention.
DRAWING CAPTIONS
[0055] Non-limiting embodiments of the invention will now be
described in more detail, by way of example only, with reference to
the accompanying drawings, of which:
[0056] FIG. 1 shows a schematic longitudinal cross sectional view
of an embodiment of a PCD element.
[0057] FIG. 2 shows a schematic expanded cross sectional view of a
region of the embodiment shown in FIG. 1.
[0058] FIG. 3 to FIG. 6 show schematic longitudinal cross sectional
views of embodiments of PCD elements.
[0059] FIG. 7A shows schematic perspective views of components used
in an embodiment of a method for manufacturing PCD compacts or
inserts.
[0060] FIG. 7B shows a schematic perspective view of a PCD compact
or insert.
[0061] FIG. 8 shows a perspective view of a rotary drill bit for
boring into the earth.
[0062] The same references in all drawings refer to the same
features, unless otherwise indicated.
DETAILED DESCRIPTION OF EMBODIMENTS
[0063] As used herein, a "mask" is a physical barrier that is
capable of retarding or preventing diffusion or chemical reactions
across it.
[0064] As used herein, "mask medium" or "mask material" is a medium
or material that is suitable for forming a mask or functioning as a
mask.
[0065] As used herein, a "passivation medium" is a medium that is
capable of retarding or preventing certain chemical reactions or
phase transformations, such as the transformation of diamond to
graphite.
[0066] As used herein, the term "unpassivated or unmasked" in
relation to a region of a PCD body means that the region is
substantially free of the mask or passivation medium substantially
present within a masked or passivated region of the polycrystalline
diamond body.
[0067] As used herein, the term "interstices" is understood to mean
"interstices or interstitial regions". Interstices may be filled or
unfilled, or partly filled with a binder or filler material.
[0068] With reference to FIG. 1 and FIG. 2, an embodiment of a PCD
insert 200 comprises an embodiment of a PCD element 100 joined to a
cemented carbide substrate 220 at an interface 116. The embodiment
of the PCD element 100 has internal diamond surfaces 102, the
internal diamond surfaces 102 defining interstices 104 between
them. The PCD element 100 comprises a masked or passivated region
111 and an unmasked or unpassivated region 112, the unmasked or
unpassivated region 112 defining a boundary 116 with the substrate
220, the boundary being the interface (both indicated by reference
116), and extending a depth of between about 5 microns and about
600 microns from the boundary 116, in which at least some of the
internal diamond surfaces 102b of the masked or passivated region
111 contact a mask or passivation medium, and wherein some or all
of the interstices 104b of the masked or passivated region 111 and
of the unmasked or unpassivated region 112 are at least partially
filled with an infiltrant material.
[0069] With reference to FIG. 3 to FIG. 6, embodiments of PCD
elements 100 are joined to cemented carbide substrates 220 to form
embodiments of PCD inserts 200 having respective working surfaces
114. The PCD elements 100 each have a respective masked or
passivated region 111, wherein the microscopic interstices (not
shown) are substantially filled with a mask or passivation medium,
and an unmasked or unpassivated region 112, proximate the substrate
220. The embodiments shown in FIG. 3, FIG. 4 and FIG. 5 each
comprise a respective further region 113, in which both the mask or
passivation medium, or precursor thereof, and the catalyst material
are present.
[0070] In the embodiment shown in FIG. 3, the volume of the masked
or passivated region 111 is substantially greater than that of the
unmasked or unpassivated region 112.
[0071] In the embodiment shown in FIG. 4, the volume of the masked
or passivated region 111 is substantially smaller than that of the
unmasked or unpassivated region 112.
[0072] In the embodiment shown in FIG. 5, the PCD element 100 is
bonded to the substrate 220 via an intermediate layer 225. The
intermediate layer 225 comprises diamond grains, metal carbide and
a metal.
[0073] In the embodiment shown in FIG. 6, the PCD element 100
comprises a porous region 115 proximate the working surface 114.
The microscopic interstices (not shown) within the porous region
115 are substantially devoid of mask or passivation medium and of
catalyst material. The masked or passivated region 111 is located
intermediate the porous region 115 and the unmasked or unpassivated
region 112.
[0074] Embodiments of PCD elements or inserts of the invention may
have particular application as cutter elements for drill bits, in
which applications the enhanced thermal stability may extend the
working life of the tool.
[0075] As used herein, a catalyst material for diamond is a
material that is capable of promoting the precipitation, growth
and/or sintering-together of grains of diamond under a condition of
pressure and temperature at which diamond is more thermodynamically
stable than graphite. Examples of catalyst materials for diamond
are iron, nickel, cobalt, manganese and certain alloys including
any of these elements. Some catalyst materials for diamond are
capable of promoting the conversion of diamond into graphite at
ambient pressure, particularly at elevated temperatures.
[0076] As used herein, "thermally stable" when used in relation to
a PCD body or element or region therein is understood to mean that
the PCD within that region has enhanced resistance to degradation
at elevated temperatures, particularly temperatures in the range
from about 400 degrees centigrade to about 800 degrees centigrade.
In some embodiments, this may be achieved if less than about 10% of
the area of the internal diamond surfaces of the body or portion
thereof is in contact with a catalyst material that is capable of
promoting the conversion of diamond into graphite at ambient
pressure.
[0077] In one embodiment, the thermally stable region is adjacent a
working surface or periphery, or adjacent a working surface and
periphery of the PCD element.
[0078] With reference to FIG. 7A, an embodiment of a method for
making a PCD element includes providing a PCD insert 300 that has
been manufactured using an ultra-high pressure and high temperature
(HPHT) method well-known in the art. The insert 300 comprises a PCD
element 310 integrally bonded to a cemented carbide hard-metal
substrate 320. The microscopic interstices (not shown) of the PCD
element 310 are substantially filled with cobalt catalyst material.
At least a part of PCD element 310 is detached from the insert 300
to produce a PCD body 311. One way of detaching the PCD element 310
is to grind away the substrate 320. The PCD body 311 is treated to
remove catalyst material from the interstices to produce a porous
and thermally stable PCD element 312. The porous PCD element 312 is
then contacted on one side with a second cemented carbide substrate
340 and on the opposite side with a source 330 of mask or
passivation medium, or a precursor for a mask or passivation
medium. The source 330 may be in the form of a thin foil or disc,
or powder. The substrate 340 includes tungsten carbide grains and a
cobalt metal binder, the metal binder being capable of acting as a
catalyst material to promote the growth and sintering of diamond
grains. The porous PCD element 312, thus "sandwiched" between the
substrate 340 and the foil or disc 330 is treated at an ultra-high
pressure in excess of about 5 GPa at temperatures sufficiently high
to melt the mask or passivation medium or its precursor and to melt
the cobalt metal binder of the substrate 340, resulting in some of
it infiltrating as an infiltrant material into the porous PCD
element 312. The temperature cycle may be controlled in such a
manner as to allow sufficient or a certain amount of the mask or
passivation medium or its precursor to be introduced into the
porous PCD element 312 prior to the cobalt metal binder material
melting and infiltrating into the porous PCD element 312. After
this treatment, the resulting insert is removed and processed to
final dimensions and tolerances to produce an embodiment of a
finished PCD insert 200 shown in FIG. 7B, comprising a PCD element
100 joined to a cemented carbide substrate 220.
[0079] One embodiment of the method of the invention includes
contacting the PCD body with a source of mask or passivation
medium, or of a mask or passivation precursor material, and with a
source of infiltrant material. In one embodiment, the PCD body has
a thickness between a pair of opposite surfaces of at least about
1.5 mm or at least about 1.8 mm, one of the pair contacted with a
source of mask or passivation medium, or of a mask or passivation
precursor material, and the other of the pair contacted with a
source of infiltrant material.
[0080] One embodiment of the method of the invention includes
heating a source of mask or passivation medium, or of a mask or
passivation precursor material, to a temperature within the range
between the melting point of the mask or passivation medium, or the
mask or passivation precursor material, and the melting point of
the infiltrant material, maintaining the temperature within this
range for a period of time sufficient for the introduction of the
mask or passivation medium, or the mask or passivation precursor
material, to be completed. In one embodiment, the temperature is
then increased to greater than the melting point of the infiltrant
material for a period of time for the introduction of the
infiltrant material to be completed.
[0081] One embodiment of the method includes contacting one surface
of a porous PCD body with a source of silicon, contacting another
surface of the PCD body with a source of cobalt to form an
assembly, subjecting the assembly to a pressure of at least about
5.5 GPa, heating the assembly to a temperature in the range above
the melting point of silicon at the pressure and below the melting
point of cobalt at the pressure, maintaining temperature within
this range for a period of time of at least about 2 minutes or at
least about 3 minutes, and then increasing the temperature to above
the melting point of cobalt at the pressure.
[0082] One embodiment of the method includes contacting one surface
of a porous PCD body with a source of aluminium, contacting another
surface of the PCD body with a source of cobalt to form an
assembly, subjecting the assembly to a pressure of at least about
5.5 GPa, heating the assembly to a temperature in the range above
the melting point of aluminium at the pressure and below the
melting point of cobalt at the pressure, maintaining temperature
within this range for a period of time of at least about 1 minute
or at least about 2 minutes, and then increasing the temperature to
above the melting point of cobalt at the pressure.
[0083] In some embodiments, the period of time is at most about 15
minutes or even at most about 10 minutes.
[0084] The sintered PCD body can be produced in an ultra-high
pressure furnace by sintering together diamond grains in the
presence of a catalyst material for diamond at a pressure of at
least about 5.5 GPa and a temperature of at least about 1,300
degrees centigrade. The catalyst material may comprise a
conventional transition metal type diamond catalyst material, such
as cobalt, iron or nickel, or certain alloys thereof. The sintered
PCD body, as a whole or at least a region thereof, may then be
rendered thermally stable, for example, through the removal of the
majority of binder catalyst material from the PCD body or desired
region using acid leaching or another similar process known in the
art.
[0085] The catalyst material present in the PCD body 311 may be
removed by any of various methods known in the art, such as
electrolytic etching, evaporation techniques, acid leaching (for
example by immersion in a liquor containing hydrofluoric acid,
nitric acid or mixtures thereof) or by means of chlorine gas, as
disclosed in international patent publication number WO2007/042920,
or by another method (e.g. as disclosed in South African patent
number 2006/00378).
[0086] In one embodiment of the method, two porous PCD bodies,
similar to the porous element 312 in FIG. 7A are provided. One of
the porous PCD bodies is infiltrated or permeated with a precursor
for a mask or passivation medium. Preferably, the precursor is a
metal that, when in the molten or gas phase, readily reacts with
carbon to form a carbide. The precursor may be introduced into the
pores of the porous PCD body by contacting a body of the precursor
material with the PCD element and heating in a vacuum or inert
atmosphere to a temperature above the melting point of the
precursor, and allowing the molten precursor to infiltrate into the
porous PCD body. If the precursor is a good carbide former (e.g. Si
or Ti), then it may react with carbon from the diamond to form a
carbide mask or passivation medium. The resulting masked or
passivated PCD body is then placed in contact with the other porous
PCD body, which in turn is placed in contact with a hard-metal
substrate containing a source of catalyst material such as cobalt.
The porous PCD body, thus "sandwiched" between the hard-metal
substrate and the masked or passivated PCD element, is treated at
an ultra-high pressure in excess of about 5 GPa at a temperature
sufficiently high to melt the metal binder of the substrate,
resulting in some of it infiltrating into the porous PCD element.
After this treatment, the resulting insert is removed and processed
to final dimensions and tolerances to produce a finished PCD
insert.
[0087] In one embodiment of the method, a PCD insert similar to PCD
insert 300 in FIG. 7A, is provided. A region proximate the working
surface of the PCD element is depleted substantially of catalyst
material by means of a method known in the art, resulting in the
region being porous. A mask or passivation medium, or precursor for
a mask or passivation medium, is introduced into the pores of the
porous region to form a coating on the internal diamond
surfaces.
[0088] For example, the medium or its precursor may be introduced
in vapour form in order to coat as much as possible of the diamond
surface area, even substantially all of the diamond surface area,
with a thin protective coating of the mask or passivation medium.
The parameters of the method of introduction may be controlled to
retain porosity within the region, the average pore volume having
been reduced by the volume of the deposited mask or passivation
medium coat. A catalyst material is then infiltrated into the
remaining pores of the masked or passivated region. This may be
done by contacting a source of catalyst material with the working
surface of the PCD element, assembling the PCD insert and the
source into a capsule of a kind used for HPHT sintering of PCD, and
subjecting the assembly to an ultra-high pressure and temperature
at which the catalyst material is molten and the diamond is
thermodynamically more stable than graphite. In some embodiment,
the pressure is at least about 5.5 GPa, at least about 6 GPa or at
least about 6.5 GPa. In one embodiment, the pressure is about 6.8
GPa.
[0089] The introduction of a mask or passivation medium or a
precursor thereof may be complete, in that the majority of the open
porosity of the masked or passivated region of the PCD body is
filled or rendered largely non-porous by the introduction of a
further phase or phases, hence blocking infiltration; or it may be
partial, in that only the exposed surfaces of the diamond
microstructure are masked or passivated, with significant
volume-based porosity remaining, but resulting in an intergrown
diamond skeleton or microstructure that is largely isolated from
chemical and physical interaction with the infiltrant or bonding
material front.
[0090] The mask or passivation medium may be removable, for example
by some suitable chemical treatment before use in the final
compact, or if inert or even beneficial can be left within the
product.
[0091] Various methods of introducing mask or passivation media or
their precursors may be used. These include using a gas phase of,
for instance, Ti, Si, W and the like, to coat the PCD material in
the region or regions thereof that are required to be free of
infiltrant material. Alternatively, pores or voids of the structure
can be filled, either wholly or partially, with an inert salt or
ceramic phase. Suitable salts or ceramics may be those which do not
melt at HPHT conditions, or undergo significant phase changes that
could compromise the structural integrity of the PCD skeleton. A
further approach involving treatment of the internal surfaces of
the porosity using a surface chemistry modification such that
chemical wetting by the infiltrant front is prevented or hindered,
is also anticipated.
[0092] Non-limiting examples of technologies for introducing mask
or passivation media into the porosity of the diamond skeleton
include: [0093] Atomic Layer Deposition (ALD) to coat the internal
diamond surfaces of the open porosity; [0094] infiltration with a
liquid pre-ceramic polymer or polymer solution that is subsequently
converted to a ceramic phase through a process of curing and
subsequent ceramitisation; [0095] use of sol gel routes or other
solution-based chemical routes to deposit or form suitable phases
in the porosity of the PCD, which may require subsequent heat
and/or gas treatments to achieve the desired phases.
[0096] Atomic Layer Deposition (ALD) may form extremely homogeneous
coatings on surfaces which, as a result, are very good barrier
layers, even for only a few (for example 25) atomic layers. In
addition, the chemistry can be controlled layer by layer, allowing
multifunctional coatings to be easily applied. ALD may have
advantages over other thin film deposition techniques because ALD
grown films are substantially conformal with the coated body,
pin-hole free and chemically bonded to the coated body. With ALD it
is possible to deposit coatings uniform in thickness inside deep
trenches, porous media and around particles. Such an ALD coating
method is disclosed, for example, in U.S. patent publication number
2008/0073127.
[0097] A further exemple alternative approach to introducing a mask
or passivation medium into a porous region within a PCD element is
to infiltrate a preceramic polymer, or other suitable
organometallic precursor material, into the pores (see, for
example, U.S. Pat. Nos. 5,649,984 and 5,690,706, and the references
cited therein, for background information). Liquid pre-ceramic
polymers exist that can be converted to ceramics through a process
of curing and subsequent cerametisation. In particilar, certain
Si--C--N liquid preceramic polymer systems may be most suitable for
infiltration into porous PCD bodies and subsequent treatment, as is
known in the art, to convert the polymer into a ceramic material,
particularly silicon carbo-nitride, as is also well known in the
art. Infiltration of a preceramic polymer into porous PCD is
advantageously carried out in vacuum and assisted by the
application of an elevated temperature and/or pressure of less than
about 30 MPa.
[0098] Another method for introducing mask or passivation material
into a porous region within a PCD element includes a sol gel method
(see, for example, the approach for depositing metal carbide onto
diamond disclosed in WO2006/032982, and coating methods as
described in WO2006/032984 and WO2007/088461). In a particular
embodiment, an inert salt such as CaCo.sub.3, for example, is
infiltrated into the porous PCD element by means of a sol gel
approach. The inert salt functions to limit the subsequent
infiltration of catalyst material at an ultra-high pressure and
temperature, resulting in a region of the PCD wherein the pores are
substantially filled with the salt and a second region wherein the
pores are substantially filled with a catalyst material. The salt
may readily be removed from the PCD element after the
reinfiltration step by means of dissolution in water, leaving a
porous region within the PCD.
[0099] Other methods may be used to introduce a mask or passivation
medium into a porous PCD body. In an example embodiment of one such
alternative approach, a porous PCD element may be infiltrated or
permeated with a vapour of tungsten hexafluoride, resulting in the
deposition of tungsten within the pores. At least some of the
tungsten may react with carbon from the diamond to form WC, which
is a suitable passivation medium. Since unreacted tungsten is also
a suitable mask or passivation medium, the formation of WC would
not be essential. Methods known in the art of diamond coatings and
metallization may be used (see, for example, U.S. Pat. Nos.
7,022,403; 5,346,719; 5,062,865; and 5,062,865). Vapour deposition
approaches may similarly be used for introducing Si, Cr or Ti into
the interstices of a porous PCD element, resulting in a carbide,
nitride, boride, carbo-nitride or boro-nitride of silicon, chromium
or titanium at least partially coating the diamond surfaces. Such
methods are well known in the art of diamond coating by means of
physical vapour deposition (PVD) and chemical vapour deposition
(CVD). See, for example, WO2005/078041, U.S. Pat. Nos. 5,024,680
and 5,221,969, and European patent number EP 0 467 404, which are
incorporated herein by reference.
[0100] In one example embodiment, the porosity may be filled wholly
or partly with a non-diamond carbon containing material. This may,
in the presence of catalyst material be converted to PCD during a
subsequent step of subjecting the PCD body to an ultra high
pressure, resulting in increased diamond density in the outer
portion of the PCD layer and hence increased thermal stability.
Infiltration with a carbon-containing material may be accomplished
by chemical vapour infiltration of amorphous graphitic carbon
supplied at low pressure using gaseous hydrocarbons including
methane, ethane or ethylene. Infiltration may also be achieved by
liquid phase infiltration at high pressure using liquid
hydrocarbons, including wax, pitch and bitumen or by impregnation
with carbon at high pressure using fullerenes.
[0101] In a further example embodiment, an intermediate layer may
be provided, for example between the substrate and the PCD body.
The function of the intermediate layer may be primarily to reduce
internal stresses within the PCD element and therefore minimise the
risk of fracture. Such intermediate layers are well known in the
art and various intermediate layers for PCD inserts have been
disclosed (e.g. U.S. Pat. No. 5,370,195 and U.S. patent publication
number U.S. 2007-0186483 A1).
[0102] The mask or passivation process may be conducted in such a
manner as to leave or render porous a region adjacent the substrate
or support surface to ensure optimal bonding during the HPHT
bonding step.
[0103] The masked or passivated region may be formed between the
thermally stable region and the porous region adjacent the
substrate or support region, provided it acts as a barrier to any
bonding phase infiltrating from the substrate or support,
preventing it from contacting or interacting in any way with the
thermally stable region.
[0104] A region adjacent a peripheral surface of the PCD element
may be treated to form a thermally stable annular region
substantially free of catalyst material. In an alternative example
embodiment, the passivated or masked region could be located
intermediate the thermally stable region, adjacent the working
surface and/or periphery, and the porous region adjacent the
surface to be attached to the substrate. The various regions are
typically provided in layer form.
[0105] Preferably, the mask or passivation step will not be carried
out under HPHT conditions, and will therefore constitute a separate
treatment of the porous PCD body under moderate temperature and
pressure conditions before it is bonded to the substrate or support
body.
[0106] In one example embodiment of the method of the invention,
the attachment or bonding of a previously sintered or intergrown
thermally stable PCD body having substantial diamond-to-diamond
bonding in its microstructure to a suitable support, such as a
cemented carbide substrate, is provided in such a way as to
maintain or preserve the thermal stability of the PCD, particularly
at the upper working surface of the resultant abrasive element.
Hence the need for any subsequent treatment or modification of the
PCD body in order to improve or attain final thermal stability of
the region adjacent the working surface or periphery may be removed
or significantly reduced. In use, PCD elements may be exposed to
elevated temperatures due to friction events at the working or
outer surface. Hence, it is typically in this region that thermal
stability must be preserved.
[0107] The provision of a degree of porosity in the PCD body may
assist in facilitating the bonding of the PCD body to the
substrate. Porosity in a region of the PCD that will contact the
substrate may allow better bonding between the substrate and the
PCD body because of infiltration of the cementing phase or another
suitable bonding phase from the substrate body or the interface
region into the PCD body. While wishing not to be bound by a
particular hypothesis, the porosity may facilitate a capillary
action which may draw the bonding phase into the PCD microstructure
and maximise the strength of the bond between the two bodies during
the attachment process.
[0108] The person skilled in the art will appreciate that PCD
elements and inserts of a wide range of shapes and sizes can be
made, depending on the type of application. The inserts may be
particularly advantageous when used in applications where the
insert may be subjected to high temperatures, and therefore where
high thermal stability is important. One such use is for rotary
drill bits used for rock drilling and earth boring in the oil and
gas industry.
[0109] With reference to FIG. 8, an embodiment of an earth-boring
rotary drill bit 800 includes, for example, a plurality of PCD
inserts 600 as previously described herein with reference to FIG.
1. The earth-boring rotary drill bit 800 includes a bit body 802
that is secured to a shank 804 having a threaded connection portion
806 (e.g., a threaded connection portion 806 conforming to industry
standards such as those promulgated by the American Petroleum
Institute (API)) for attaching the drill bit 800 to a drill string
(not shown). The bit body 802 may comprise a particle-matrix
composite material or a metal alloy such as steel. The bit body 802
may be secured to the shank 804 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 802 may be secured to the
shank, 804, indirectly by way of a metal blank or extension between
them, as known in the art.
[0110] The bit body 802 may include internal fluid passageways (not
shown) that extend between the face 803 of the bit body 802 and a
longitudinal bore (not shown), which extends through the shank 804,
an extension 808 and partially through the bit body 802. Nozzle
inserts 824 also may be provided at the face 803 of the bit body
802 within the internal fluid passageways. The bit body 802 may
further include a plurality of blades 816 that are separated by
junk slots 818. In some embodiments, the bit body 802 may include
gage wear plugs 822 and wear knots 828. A plurality of PCD inserts,
which are generally indicated by reference numeral 600 in FIG. 8,
may be mounted on the face 803 of the bit body 802 in cutting
element pockets 812 that are located along each of the blades
816.
[0111] The inserts 600 are positioned to cut a subterranean
formation being drilled while the drill bit, 800, is rotated under
weight on bit (WOB) in a bore hole about centreline, L800.
[0112] Embodiments of PDC inserts of the present invention may also
be used as gauge trimmers, and may be used on other types of
earth-boring tools. For example, embodiments of inserts of the
present invention may also be used on cones of roller cone drill
bits, on reamers, mills, bi-centre bits, eccentric bits, coring
bits, and so-called hybrid bits that include both fixed cutters and
rolling cutters.
EXAMPLES
[0113] The invention will now be described, by way of example only,
with reference to the following non-limiting examples.
Example 1
[0114] A PCD insert suitable for use on a rotary bit for oil and
gas drilling and having a diameter of about 16 mm was provided. The
insert was substantially cylindrical in shape and comprised a PCD
layer integrally bonded to a Co-cemented WC substrate. The PCD
layer was about 2.3 mm thick and comprised sintered diamond grains
with an average grain size of less than about 20 microns and with a
grain size distribution which was capable of being resolved into at
least three distinct peaks, or modes. The interstices between the
diamond grains of the PCD were filled with Co, a catalyst material
sourced from the hard-metal substrate during the step of sintering
the PCD. The PCD layer was detached from the substrate by means of
wire EDM (electro-discharge machining), providing a PCD body having
a generally disc-like shape. Substantially all of the Co was then
removed from the PCD body by immersing it in a mixture of
hydrofluoric and nitric acid for several days, resulting in a
porous, detached PCD body. The porous PCD body was heat treated in
vacuum in order to remove (i.e. "outgas") any residual organic
impurities that may have been present.
[0115] The porous PCD body was placed onto a flat surface of
another cylindrical substrate comprising cobalt-cemented tungsten
carbide, and a thin disc of silicon placed on top of the porous PCD
disc, and this assembly was loaded into a capsule for an ultra-high
pressure furnace (or high temperature press). Although a disc of
silicon was used in this example, a layer of silicon powder could
be used. The silicon disc was less than 1 mm thick and had been
ultrasonically cleaned in an acetone bath. The assembly was
subjected to an ultra-high pressure of greater than about 5.5 GPa,
at which diamond is thermodynamically stable. The temperature was
increased to about 1,220 degrees centigrade, which was greater than
the melting point of silicon at the pressure, and maintained
between this temperature and about 1,320 degrees centigrade, which
is approximately the melting point of cobalt at the pressure, for a
period of 3 minutes. This period had been determined by
experimentation to be sufficient for the silicon to melt and
infiltrate into the PCD body to a depth from the substrate of
greater than about 100 microns and less than about 400 microns. The
temperature was then increased to about 1,400 degrees centigrade
and maintained at this level for about 5 minutes. In this way, the
porous PCD body was re-infiltrated to a depth of between 100 and
400 microns with molten cobalt from the substrate and molten
silicon from the opposite surface, and simultaneously bonded to the
substrate.
[0116] After the re-infiltration step, the insert was recovered and
sliced into two parts along an axial plane, producing two
cross-sectional surfaces. One of these surfaces was polished and
analysed by means of SEM (scanning electron microscopy). It was
found that the silicon had infiltrated the PCD to a depth of
several hundred microns and substantially all had reacted with
carbon from the diamond to form SiC. The interstices near the side
of the PCD bonded to the substrate were substantially filled with
Co, which had infiltrated from the substrate, and there was a layer
between the silicon-rich and the cobalt-rich layers in which the
interstices were substantially filled with both Co and Si. Further
analysis revealed that cobalt disilicide was present within the
intermediate layer.
Example 2
[0117] A porous PCD body can be prepared as in Example 1 and
silicon can be introduced into some of the pores prior to the
treatment at ultra-high pressure. This can be done by placing the
porous PCD disc into a graphite vessel and disposing a silicon foil
on top of it, the silicon foil having been ultra-sonically cleaned
in an acetone bath. The vessel can be placed in a furnace and its
contents heated in a vacuum to about 1,550.degree. C., causing the
silicon foil to melt and infiltrate the PCD disc. When the PCD body
is removed from the furnace after re-infiltration, it is
anticipated that the interstices will be filled with silicon
carbide and a minor amount of unreacted silicon to a depth of about
200 microns.
[0118] Such a partially infiltrated PCD body can be placed onto a
cobalt-cemented tungsten carbide substrate, with the
non-infiltrated side (i.e. the side of the PCD on which the
interstices are substantially empty and the PCD body is porous) in
contact with a surface of the substrate. This assembly of PCD disc
and substrate can then be subjected to an ultra-high pressure of
greater than about 5.5 GPa and a temperature of greater than about
1,500.degree. C. to produce a PCD insert.
Example 3
[0119] A porous PCD body can be prepared as in Example 1 and
silicon can be introduced into some of the pores prior to the
treatment at ultra-high pressure. Only a very thin film of silicon
can be deposited onto a flat surface of the PCD disc by means of
sputtering. The mass of the silicon deposited should be calculated
to be just sufficient for 10% of the pores to be filled with
silicon carbide, and consequently to provide just enough silicon to
infiltrate the PCD to a depth of about 10% of its thickness, i.e.
to a depth of about 230 microns from the flat surface, leaving the
remaining pores substantially empty. This mass, when calculated,
will typically be about 12 milligrams, providing a film of about 23
microns thick, the film thickness being as uniform as possible
across the PCD surface.
[0120] The silicon-coated PCD can then be placed into a graphite
vessel, with the coated surface remote from the base of the
graphite vessel (i.e. on the top surface), and the vessel then
placed into a furnace. The vessel and its contents are to be heated
in a vacuum to 1,550.degree. C., this temperature being above the
melting point of silicon, to produce a PCD insert.
Example 4
[0121] A porous PCD body was prepared as described in Example 1.
The porous PCD body was placed onto a flat surface of a cylindrical
substrate comprising cobalt-cemented tungsten carbide, and a layer
of aluminium powder was introduced on top of the porous PCD disc.
The layer of aluminium powder had a mass of about 135 mg and the
mean size of the powder was in the range of about 5 microns to 20
microns. Although aluminium powder was used in this example, an
aluminium disc or foil could also be used. The mass of the
aluminium powder was estimated to correspond to a fully dense
volume of aluminium equivalent to about 10 percent of the volume of
the PCD body. This assembly was loaded into a capsule for an
ultra-high pressure furnace (or high temperature press). The
aluminium layer was less than about 1mm thick. The assembly was
subjected to an ultra-high pressure of greater than about 5.5 GPa,
at which diamond is thermodynamically stable. The temperature was
increased to about 900 degrees centigrade, which was greater than
the melting point of aluminium at the pressure, and maintained
between this temperature and about 1,330 degrees centigrade, which
was the melting point of cobalt at the pressure, for a period of 1
minute. This period had been determined by experimentation to be
sufficient for the aluminium to melt and infiltrate into the PCD
body to a depth from the substrate of greater than about 100
microns and less than about 400 microns. The temperature was then
increased to about 1,500 degrees centigrade and maintained at this
level for about 5 minutes. In this way, the porous PCD body was
re-infiltrated to a depth of between 100 and 400 microns with
molten cobalt from the substrate and molten aluminium from the
opposite surface, and simultaneously bonded to the substrate.
[0122] After the re-infiltration step, the insert was recovered and
sliced into two parts along an axial plane, producing two
cross-sectional surfaces. One of these surfaces was polished and
analysed by means of SEM (scanning electron microscopy), revealing
that the PCD had bonded well with the substrate. Further analysis
by means of energy dispersive spectroscopy (EDS) and other
techniques revealed that and that substantially all of the
interstices within a region of the PCD further than about 150
microns from the interface with the substrate were filled with
aluminium carbide. A minor amount of other aluminium containing
compounds and cobalt was observed throughout this region. The PCD
interstices within about 150 microns from the substrate were filled
principally with cobalt, although some aluminium was evident.
[0123] Further test inserts were made as above and subjected to a
wear test, which involved using the inserts, suitably prepared as
would be appreciated by the skilled person, to mill a granite block
mounted on a vertical turret milling apparatus. The PCD layer
displayed excellent wear resistance and thermal stability. As a
control, a PCD insert was made using a PCD body that had not been
infiltrated with aluminium. The measure of performance in this test
was distance of granite cut before the onset of "rubbing", in which
the depth of the cut into the granite begins to decrease,
indicating decreased cutting effectiveness. This distance was about
750 mm in the case of the control insert and in the range from
about 3,500 mm to about 6,200 mm in the case of the test
insert.
Example 5
[0124] A porous PCD disc can be prepared using the process
described in Example 1 and aluminium can be introduced into the
pores prior to the treatment at ultra-high pressure. This can be
done by placing the porous PCD disc into a graphite vessel, and
disposing an aluminium foil on top of it, the aluminium foil having
been ultra-sonically cleaned in an acetone bath. The vessel can
then be placed in a furnace and its contents heated in a vacuum to
above the melting point of aluminium, i.e. to about 900 degrees
centigrade, causing the aluminium foil to melt and infiltrate the
PCD disc.
Example 6
[0125] A porous PCD disc can be prepared using the process
described in Example 1 and aluminium can be introduced into the
pores prior to the treatment at ultra-high pressure by depositing a
very thin film of aluminium onto a flat surface of the PCD disc by
means of sputtering. The mass of the aluminium deposited can be
calculated to be just sufficient for 10% of the pores to be filled
with aluminium carbide, and consequently to provide just enough
aluminium to infiltrate the PCD to a depth of about 10% of its
thickness, i.e. to a depth of about 230 microns from the flat
surface, leaving the remaining pores substantially empty. This mass
could be about 14 milligrams, providing a film about 23 microns
thick, the film thickness being as uniform as possible across the
PCD surface.
[0126] The aluminium-coated PCD can be placed into a graphite
vessel, with the coated surface remote from the base of the
graphite vessel (i.e. on the top surface), and the vessel placed
into a furnace. The vessel and its contents can then be heated in a
vacuum to 900 degrees centigrade, this temperature being above the
melting point of aluminium and one at which aluminium carbide forms
readily when in contact with a source of carbon. This would result
in the masked PCD body having a stratum of about 230 microns thick
comprising aluminium carbide in the interstices.
[0127] The masked PCD body can then be assembled into a capsule,
the end of the PCD body opposite the stratum being in contact with
a cobalt cemented carbide substrate, or other source of cobalt, and
subjected to a pressure of at least about 5.5 GPa and a temperature
of at least about 1,350 degrees centigrade. Cobalt would infiltrate
from the source into the porous region of the PCD but not into the
stratum containing the aluminium carbide, resulting in a thermally
stable PCD element.
* * * * *