Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02520319 2005-09-21
THERMALLY STABLE DIAMOND POLYCRYSTALLINE DIAMOND CONSTRUCTIONS
FIELD OF THE INVENTION
This invention generally relates to polycrystalline diamond
materials and, more specifically, to polycrystalline diamond
materials that have been specifically engineered to provide an
improved degree of thermal stability when compared to
conventional polycrystalline diamond materials, thereby
providing an improved degree of service life in desired cutting
and/or drilling applications.
BACKGROUND OF THE INVENTION
Polycrystalline diamond (PCD) materials and PCD elements
formed therefrom are well known in the art. Conventional PCD is
formed by combining synthetic diamond grains with a suitable
solvent catalyst material to form a mixture. The mixture is
subjected to processing conditions of extremely high
pressure/high temperature, where the solvent catalyst material
promotes desired intercrystalline diamond-to-diamond bonding
between the grains, thereby forming a PCD structure. The
resulting PCD structure produces enhanced properties of wear
resistance and hardness, making PCD materials extremely useful
in aggressive wear and cutting applications where high levels of
wear resistance and hardness are desired.
Solvent catalyst materials typically used for forming
conventional PCD include metals from Group VIII of the Periodic
table, with cobalt (Co) being the most common. Conventional PCD
can comprise from 85 to 95o by volume diamond and a remaining
amount solvent catalyst material. The material microstructure
of conventional PCD comprises regions of intercrystalline bonded
diamond with solvent catalyst material attached to the diamond
and/or disposed within interstices or interstitial regions that
exist between the intercrystalline bonded diamond regions.
1
CA 02520319 2005-09-21
A problem known to exist with such conventional PCD
materials is that they are vulnerable to thermal degradation,
when exposed to elevated temperature cutting and/or wear
applications, caused by the differential that exists between the
thermal expansion characteristics of the interstitial solvent
metal catalyst material and the thermal expansion
characteristics of the intercrystalline bonded diamond. Such
differential thermal expansion is known to occur at temperatures
of about 400°C, can cause ruptures to occur in the diamond-to-
diamond bonding, and eventually result in the formation of
cracks and chips in the PCD structure, rendering the PCD
structure unsuited for further use.
Another form of thermal degradation known to exist with
conventional PCD materials is one that is also related to the
presence of the solvent metal catalyst in the interstitial
regions and the adherence of the solvent metal catalyst to the
diamond crystals. Specifically, the solvent metal catalyst is
known to cause an undesired catalyzed phase transformation in
diamond (converting it to carbon monoxide, carbon dioxide, or
graphite) with increasing temperature, thereby limiting
practical use of the PCD material to about 750°C.
Attempts at addressing such unwanted forms of thermal
degradation in conventional PCD materials are known in the art.
Generally, these attempts have focused on the formation of a PCD
body having an improved degree of thermal stability when
compared to the conventional PCD materials discussed above. One
known technique of producing a PCD body having improved thermal
stability involves, after forming the PCD body, removing all or
a portion of the solvent catalyst material therefrom.
For example, U.S. Patent No. 6,544,308 discloses a PCD
element having improved wear resistance comprising a diamond
matrix body that is integrally bonded to a metallic substrate.
While the diamond matrix body is formed using a catalyzing
material during high temperature/high pressure processing, the
2
CA 02520319 2005-09-21
diamond matrix body is subsequently treated to render a region
extending from a working surface to a depth of at least about
0.l mm substantially free of the catalyzing material, wherein
0.1 mm is described as being the critical depletion depth.
S Japanese Published Patent Application 59-219500 discloses a
diamond sintered body joined together with a cemented tungsten
carbide base formed by high temperature/high pressure process,
wherein the diamond sintered body comprises diamond and a
ferrous metal binding phase. Subsequent to the formation of the
diamond sintered body, a majority of the ferrous metal binding
'phase is removed from an area of at least 0.2 mm from a surface
layer of the diamond sintered body.
In addition to the above-identified references that
disclose treatment of the PCD body to improve the thermal
stability by removing the catalyzing material from a region of
the diamond body extending a minimum distance from the diamond
body surface, there are other known references that disclose the
practice of removing the catalyzing material from the entire PCD
body. While this approach produces an entire PCD body that is
substantially free of the solvent catalyst material, is it
fairly time consuming. Additionally, a problem known to exist
with this approach is that the lack of solvent metal catalyst
within the PCD body precludes the subsequent attachment of a
metallic substrate to the PCD body by solvent catalyst
infiltration.
Additionally, PCD bodies rendered thermally stable by
removing substantially all of the catalyzing material from the
entire body have a coefficient of thermal expansion that is
sufficiently different from that of conventional substrate
materials (such as WC-Co and the like) that are typically
infiltrated or otherwise attached to the PCD body. The
attachment of such substrates to the PCD body is highly desired
to provide a PCD compact that can be readily adapted for use in
many desirable applications. However, the difference in thermal
3
CA 02520319 2005-09-21
expansion between the thermally stable PCD body and the
substrate, and the poor wetability of the thermally stable PCD
body diamond surface due to the substantial absence of solvent
metal catalyst, makes it very difficult to bond the thermally
stable PCD body to conventionally used substrates. Accordingly,
such PCD bodies must be attached or mounted directly to a device
for use, i.e., without the presence of an adjoining substrate.
Since such PCD bodies, rendered thermally stable by having
the catalyzing material removed from the entire diamond body,
are devoid of a metallic substrate they cannot (e. g., when
configured for use as a drill bit cutter) be attached to a drill
bit by conventional brazing process. The use of such thermally
stable PCD body in this particular application necessitates that
the PCD body itself be mounted to the drill bit by mechanical or
interference fit during manufacturing of the drill bit, which is
labor intensive, time consuming, and does not provide a most
secure method of attachment.
While these above-noted known approaches provide insight
into diamond bonded constructions capable of providing some
improved degree of thermal stability when compared to
conventional PCD constructions, it is believed that further
improvements in thermal stability for PCD materials useful for
desired cutting and wear applications can be obtained according
to different approaches that are both capable of minimizing the
amount of time and effort necessary to achieve the same, and
that permit formation of a thermally stable PCD construction
comprising a desired substrate bonded thereto to facilitate
attachment of the construction with a desired application
device.
It is, therefore, desired that diamond compact
constructions be developed that include a PCD body having an
improved degree of thermal stability when compared to
conventional PCD materials, and that include a substrate
material bonded to the PCD body to facilitate attachment of the
4
CA 02520319 2005-09-21
resulting thermally stable compact construction to an
application device by conventional method such as welding or
brazing and the like. It is further desired that such a compact
construction provide a desired degree of thermal stability in a
manner that can be manufactured at reasonable cost without
requiring excessive manufacturing times and without the use of
exotic materials or techniques.
SUMMARY OF THE INVENTION
Thermally stable diamond constructions, prepared according to
principles of this invention, comprise a diamond body having a
plurality of bonded diamond crystals and a plurality of
interstitial regions disposed among the crystals. A metallic
substrate is attached to the diamond body. The diamond body
includes a first region that is substantially free of a catalyst
material and that extends a partial depth from a surface into
the diamond body. The diamond body further includes a second
region that includes the catalyst material.
In an example embodiment, the diamond body comprises
natural diamond grains. The first region may comprise the
natural diamond grains, or may comprise a mixture of natural and
synthetic diamond grains. The second region may comprise
synthetic diamond grains.
The diamond body is formed by subjecting the selected
diamond grains and a catalyst material to a high pressure/high
temperature condition to cause diamond-to-diamond bonding,
forming PCD. The diamond body may then treated to form the
first region that is substantially free of the catalyst
material, and to allow the catalyst material to remain in the
second region of the diamond body. In the event that a portion
of the diamond body is formed from natural diamond, such
treating may not be necessary to obtain a desired degree of
relative thermal stability.
5
CA 02520319 2005-09-21
In an example embodiment where the first region is treated
to render the first region substantially free of the catalyst
material, before such treating step, the surface portion of the
diamond body to be treated is finished to an approximate final
dimension so that the depth of the treated region remains
substantially the same in the final construction as it was when
treated.
In an example embodiment, during the treating step, an acid
material is used to remove the catalyst material and also
results in the removal of non-catalyst metallic materials from
the region of the diamond body that is treated. The removal of
non-catalyst metallic materials, in addition to catalyst
material, is believed to provide a further enhanced degree of
thermal stability to the first region.
Tn an example embodiment the first region may extend a
depth from a working surface of the diamond body and/or from a
side surface of the diamond body. When extending a depth from a
working surface, such depth may be between about 0.02 mm to 0.09
mm. When extending a depth from the side surface of the diamond
body, such depth may be about 0.02 micrometers to 1 mm, and the
first region may extend a length along such side surface that is
about 25 to 100 percent of the side surface length as measured
from the working surface. The depth along this side surface can
vary as a function of distance moving away from the working
surface.
In an example embodiment, the diamond body comprises
diamond crystals having an average diamond grain size of greater
than about 0.02 mm, and comprises at least 85 percent by volume
diamond based on the total volume of the diamond body.
Additionally, the second region can have an average thickness of
at least about 0.01 mm.
Thermally stable diamond constructions of this invention
may be provided in the form of a compact comprising a
polycrystalline diamond body attached to a substrate. The
6
CA 02520319 2005-09-21
compact is treated so that a desired surface of the diamond body
to be rendered thermally stable remains exposed therefrom, and
so that the remaining portion of the diamond body and the
substrate is protected. Protection of the remaining portion can
be achieved by using a protective material, for example,
provided in the form of a coating or a protective member. In a
preferred embodiment, such protection is provided by the use of
a protective member or fixture that is configured to provide a
leak-tight seal with the compact. The compact and fixture form
an assembly that is subjected to the desired treating agent,
whereby the exposed surface of the diamond body is placed into
contact with the treating agent for a predetermined period of
time to provide a thermally stable region within the diamond
body extending a desired depth beneath the working surface to
provide the desired first region, while allowing the catalyst
material to remain untreated in a second region of the diamond
body. In an example embodiment, before the compact is treated,
the surface portion of the compact to be treated is finished to
an approximate final dimension.
Thermally stable constructions of this invention display an
enhanced degree of thermal stability when compared to
conventional PCD materials, and include a substrate material
bonded to the PCD body that facilitates attachment therewith to
an application device by conventional method such as welding or
brazing and the like.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features and advantages of the present
invention will be appreciated as the same becomes better
understood by reference to the following detailed description
when considered in connection with the accompanying drawings
wherein:
7
CA 02520319 2005-09-21
FIG. 1 is a schematic view of a region of polycrystalline
diamond prepared in accordance with principals of this
invention;
FIGS. 2A to 2E are perspective views of different
polycrystalline diamond compacts of this invention comprising
the region illustrated in FIG. 1;
FIG. 3 is a perspective view of an example embodiment
thermally stable polycrystalline diamond construction of this
invention;
FIG. 4 is a cross-sectional side view of the example
embodiment thermally stable polycrystalline diamond construction
of this invention as illustrated in FIG. 3;
FIG. 5 is a schematic view of a region of the thermally
stable polycrystalline diamond construction of this invention;
IS FIG. 6 is a cross-sectional side view of a region of an
example embodiment thermally stable polycrystalline diamond
construction of this invention;
FIG. 7 is a perspective side view of an insert, for use in
a roller cone or a hammer drill bit, comprising the thermally
stable polycrystalline diamond construction of this invention;
FIG. 8 is a perspective side view of a roller cone drill
bit comprising a number of the inserts of FIG. 7;
FIG. 9 is a perspective side view of a percussion or hammer
bit comprising a number of inserts of FIG. 7;
FIG. 10 is a schematic perspective side view of a diamond
shear cutter comprising the thermally stable polycrystalline
diamond construction of this invention;
FIG. 11 is a perspective side view of a drag bit comprising
a number of the shear cutters of FIG. 10; and
FIG. 12 is a cross-sectional perspective view of a
protective fixture.
8
CA 02520319 2005-09-21
DETAILED DESCRIPTION
Thermally stable polycrystalline diamond (TSPCD)
constructions of this invention are specifically engineered
having a diamond bonded body comprising a region of thermally
stable diamond extending a selected depth from a body working or
cutting surface, thereby providing an improved degree of thermal
stability when compared to conventional PCD materials not having
such a thermally stable diamond region.
As used herein, the term "PCD" is used to refer to
polycrystalline diamond that has been formed, at high
pressure/high temperature (HPHT) conditions, through the use of
a solvent metal catalyst, such as those included in Group VIII
of the Periodic table. "Thermally stable polycrystalline
diamond" as used herein is understood to refer to
intercrystalline bonded diamond that includes a volume or region
that is or that has been rendered substantially free of the
solvent metal catalyst used to form PCD, or the solvent metal
catalyst used to form PCD remains in the region of the diamond
body but is otherwise reacted or otherwise rendered ineffective
in its ability adversely impact the bonded diamond at elevated
temperatures as discussed above.
TSPCD constructions of this invention can further include a
substrate attached to the diamond body that facilitates the
attachment of the TSPCD construction to cutting or wear devices,
e.g., drill bits when the TSPCD construction is configured as a
cutter, by conventional means such as by brazing and the like.
FIG. 1 illustrates a region of PCD l0 formed during a high
pressure/high temperature (HPHT) process stage of forming this
invention. The PCD has a material microstructure comprising a
material phase of intercrystalline diamond made up of a
plurality of bonded together adjacent diamond grains 12 at HPHT
conditions. The PCD material microstructure also includes
interstitial regions 14 disposed between bonded together
adjacent diamond grains. During the HPHT process, the solvent
9
CA 02520319 2005-09-21
metal catalyst used to facilitate the bonding together of the
diamond grains migrates into and resides within these
interstitial regions 14.
FIG. 2A illustrates an example PCD compact 16 formed in
accordance with this invention by HPHT process. The PCD compact
16 generally comprises a PCD body 18, having the material
microstructure described above and illustrated in FIG. 1, that
is bonded to a desired substrate 20. Although the PCD compact
16 is illustrated as being generally cylindrical in shape and
having a disk-shaped flat or planar surface 22, it is understood
that this is but one preferred embodiment and that the PCD body
as used with this invention can be configured other than as
specifically disclosed or illustrated. It is further to be
understood that the compact 16 may be configured having working
or cutting surfaces disposed along the disk-shaped surface
and/or along side surfaces 24 of the PCD body, depending on the
particular cutting or wear application.
Alternatively, the PCD compact may be configured having an
altogether different shape but generally comprising a substrate
and a PCD body bonded to the substrate, wherein the PCD body is
provided with working or cutting surfaces oriented as necessary
to perform working or cutting service when the compact is
mounted to a desired drilling or cutting device, e.g., a drill
bit.
FIGS. 2B to 2D illustrate alternative embodiments of PCD
compacts of this invention having a substrate and/or PCD body
configured differently than that illustrated in FIG. 2A. For
example, FIG. 2B illustrates a PCD compact 1& configured in the
shape of a preflat or gage trimmer including a cut-off portion
19 of the PCD body 18 and the substrate 20. The preflat
includes working or cutting surface positioned along a disk-
shaped surface 22 and a side surface 24 working surface.
Alternative preflat or gage trimmer PCD compact configurations
intended to be within the scope of this invention include those
CA 02520319 2005-09-21
described in U.S. Patent No. 6,604,588, which is incorporated
herein by reference.
FIG. 2C illustrates another embodiment of a PCD compact 16
of this invention configured having the PCD body 18 disposed
onto an angled underlying surface of the substrate 20 and having
a disk-shaped surface 22 that is the working surface and that is
positioned at an angle relative to an axis of the compact. FIG.
2D illustrates another embodiment of a PCD compact 16 of this
invention configured having the substrate 20 and the PCD body 18
disposed onto a surface of the substrate. In this particular
embodiment, the PCD body has a domed or convex surface 22
serving as the working surface 22 (similar to the PCD compact
embodiment described below and illustrated in FIG. 7?.
FIG. 2E illustrates a still other embodiment of a PCD
compact 16 of this invention that is somewhat similar to that
illustrated in FIG. 2A in that it includes a PCD body 18
disposed on the substrate 20 and having a disk-shaped surface 22
as a working surface. Unlike the embodiment of FIG. 2A,
however, this PCD compact includes an interface 21 between the
PCD body and the substrate that is not uniformly planar. In
this particular example, the interface 21 is canted or otherwise
non-axially symmetric. It is to be understood that PCD compacts
of this invention can be configured having PCD body-substrate
interfaces that are uniformly planer or that are not uniformly
planer in a manner that is symmetric or nonsymmetric relative to
an axis running through the compact. Examples of other
configurations of PCD compacts having nonplanar PCD body-
substrate interfaces include those described in U.S. Patent No.
6,550,556, which is incorporated herein by reference.
Diamond grains useful for forming the PCD body of this
invention during the HPHT process include diamond powders having
an average diameter grain size in the range of from
submicrometer in size to 0.1 mm, and more preferably in the
range of from about 0.005 mm to 0.08 mm. The diamond powder can
11
CA 02520319 2005-09-21
contain grains having a mono or multi-modal size distribution.
In a preferred embodiment for a particular application, the
diamond powder has an average particle grain size of
approximately 20 to 25 micrometers. However, it is to be
understood that the use of diamond grains having a grain size
less than this amount, e.g., less than about 15 micrometers, is
useful for certain drilling and/or cutting applications. In the
event that diamond powders are used having differently sized
grains, the diamond grains are mixed together by conventional
process, such as by ball or attrittor milling for as much time
as necessary to ensure good uniform distribution.
The diamond powder used to prepare the PCD body can be
synthetic diamond powder. Synthetic diamond powder is known to
include small amounts of solvent metal catalyst material and
IS other materials entrained within the diamond crystals
themselves. Alternatively, the diamond powder used to prepare
the PCD body can be natural diamond powder. Unlike synthetic
diamond powder or grains, natural diamond grains do not include
solvent metal catalyst material and/or other noncatalyst
materials entrained within the diamond crystals. The inclusion
of catalyst material as well as other noncatalyst material in
the crystals of the synthetic diamond powder can operate to
impair or limit the extent to which the resulting PCD body is or
can be rendered thermally stable. Since natural diamond grains
2S are largely devoid of these other materials which cannot be
removed from the synthetic diamond grains, a higher degree of
thermal stability exists or can thus be obtained.
Accordingly, for applications calling for a high degree of
thermal stability, the use of natural diamond for forming the
PCD body is preferred. Additionally, PCD bodies of this
invention can be formed by selective use of natural diamond
grains to form the entire PCD body or one or more regions of the
body where a desired improved degree of thermal stability is
desired. In such embodiment, the PCD body can be formed using
12
CA 02520319 2005-09-21
natural diamond to form a first region where a desired improved
degree of thermal stability is desired, e.g., a region defining
a working or side surface of the body, and another region of the
body can be formed from synthetic diamond grains. This other
region can, for example, a region that does not form a working
surface but perhaps forms an interface with a substrate, where
such an improved degree of thermal stability is not needed.
Alternatively, PCD bodies of this invention can be formed
using a mixture of natural diamond and synthetic diamond
throughout the entire diamond body, or only at one or more
selected regions of the PCD body. For example, natural diamond
and synthetic diamond grains can be combined at a desired mix
ratio to provide a tailored improvement in the degree of thermal
stability for the particular PCD body region or regions best
IS suited for a particular PCD body application. While PCD bodies
of this invention include a region rendered thermally stable by
treating to render the region substantially free of a catalyst
material, it is to be understood that PCD bodies of this
invention may also include a region wherein the thermally
stability is improved without requiring such treatment by
forming such region to have a higher diamond density using
natural diamond grains.
The diamond grain powder, whether synthetic or natural, is
combined with or already includes a desired amount of catalyst
,material to facilitate desired intercrystalline diamond bonding
during HPHT processing. Suitable catalyst materials useful for
forming the PCD body include those solvent metals selected from
the Group VTII of the Periodic table, with cobalt (Co) being the
most common, and mixtures or alloys of two or more of these
materials. The diamond grain powder and catalyst material
mixture can comprise 85 to 95o by volume diamond grain powder
and the remaining amount catalyst material. Alternatively, the
diamond grain powder can be used without adding a solvent metal
catalyst in applications where the solvent metal catalyst can be
13
CA 02520319 2005-09-21
provided by infiltration during HPHT processing from the
adjacent substrate or adjacent other body to be bonded to the
PCD body.
In certain applications it may be desired to have a PCD
body comprising a single PCD-containing volume or region, while
in other applications it may be desired that a PCD body be
constructed having two or more different PCD-containing volumes
or regions. For example, it may be desired that the PCD body
include a first PCD-containing region extending a distance from
a working surface, and a second PCD-containing region extending
from the first PCD-containing region to the substrate. The PCD-
containing regions can be formed having different diamond
densities and/or be formed from different diamond grain sizes.
It is, therefore, understood that TSPCD constructions of this
invention may include one or multiple PCD regions within the PCD
body as called for by a particular drilling or cutting
application.
The diamond grain powder and catalyst material mixture is
preferably cleaned, and loaded into a desired container for
placement within a suitable HPHT consolidation and sintering
device, and the device is then activated to subject the
container to a desired HPHT condition to consolidate and sinter
the diamond powder mixture to form PCD.
In an example embodiment, the device is controlled so that
the container is subjected to a HPHT process comprising a
pressure in the range of from 5 to 7 GPa and a temperature in
the range of from about 1320 to 1600~C, for a sufficient period
of time. During this HPHT process, the catalyst material in the
mixture melts and infiltrates the diamond grain powder to
facilitate intercrystalline diamond bonding. During the
formation of such intercrystalline diamond bonding, the catalyst
material migrates into the interstitial regions within the
microstructure of the so-formed PCD body that exists between the
diamond bonded grains (see FIG. 1?.
14
CA 02520319 2005-09-21
The PCD body can be formed with or without having a
substrate material bonded thereto. In the event that the
formation of a PCD compact comprising a substrate bonded to the
PCD body is desired, a selected substrate is loaded into the
container adjacent the diamond powder mixture prior to HPHT
processing. An advantage of forming a PCD compact having a
substrate bonded thereto is that it enables attachment of the
to-be-formed TSPCD construction to a desired wear or cutting
device by conventional method, e.g., brazing or welding.
Additionally, in the event that the PCD body is to be bonded to
a substrate, and the substrate includes a metal solvent
catalyst, the metal solvent catalyst needed for catalyzing
intercrystalline bonding of the diamond can be provided by
infiltration. In which case is may not be necessary to mix the
diamond powder with a metal solvent catalyst prior to HPHT
processing.
Suitable materials useful as substrates for forming PCD
compacts of this invention include those conventionally used as
substrates for conventional PCD compacts, such as those formed
from metallic and cermet materials. In a preferred embodiment,
the substrate is provided in a preformed state and includes a
metal solvent catalyst that is capable of infiltrating into the
adjacent diamond powder mixture during processing to facilitate
and provide a bonded attachment therewith. Suitable metal
solvent catalyst materials include those selected from Group
VIII elements of the Periodic table. A particularly preferred
metal solvent catalyst is cobalt (Co). In a preferred
embodiment, the substrate material comprises cemented tungsten
carbide (WC-Co) .
Once formed, the PCD body or compact is treated to render a
selected region thereof thermally stable. This can be done, for
example, by removing substantially all of the catalyst material
from the selected region by suitable process, e.g., by acid
leaching, aqua regia bath, electrolytic process, or combinations
CA 02520319 2005-09-21
thereof. Alternatively, rather than actually removing the
catalyst material from the PCD body or compact, the selected
region of the PCD body or compact can be rendered thermally
stable by treating the catalyst material in a manner that
reduces or eliminates the potential for the catalyst material to
adversely impact the intercrystalline bonded diamond at elevated
temperatures.
For example, the catalyst material can be combined
chemically with another material to cause it to no longer act as
a catalyst material, or can be transformed into another material
that again causes it to no longer act as a catalyst material.
Accordingly, as used herein, the terms "removing substantially
all" or "substantially free" as used in reference to the
catalyst material is intended to cover the different methods in
which the catalyst material can be treated to no longer
adversely impact the intercrystalline diamond in the PCD body or
compact with increasing temperature. Additionally, as noted
above, the PCD body may alternatively be formed from natural
diamond grains and to have a higher diamond density, to thereby
reduce the level of catalyst material in the body. In some
applications, this may be considered to render it sufficiently
thermally stable without the need for further treatment.
It is desired that the selected thermally stable region for
TSPCD constructions of this invention is one that extends a
determined depth from at least a portion of the surface, e.g.,
at least a portion of the working or cutting surface, of the
diamond body independent of the working or cutting surface
orientation. Again, it is to be understood that the working or
cutting surface may include more than one surface portion of the
diamond body.
In an example embodiment, it is desired that the thermally
stable region extend from a working or cutting surface of the
PCD body an average depth of at least about 0.008 mm to an
average depth of less than about 0.1 mm, preferably extend from
16
CA 02520319 2005-09-21
a working or cutting surface an average depth of from about 0.02
mm to an average depth of less than about 0.09 mm, and more
preferably extend from a working or cutting surface an average
depth of from about 0.04 mm to an average depth of about 0.08
mm. The exact depth of the thermally stable region can and will
vary within these ranges for TSPCD constructions of this
invention depending on the particular cutting and wear
application.
Generally, it has been shown that thermally stable regions
within these ranges of depth from the working surface produce a
TSPCD construction having improved properties of wear and
abrasion resistance when compared to conventional PCD compacts,
while also providing desired properties of fracture strength and
toughness. It is believed that thermally stable regions having
depths beneath the working surface greater than the upper limits
noted above, while possibly capable of exhibiting a higher
degree of wear and abrasion resistance, would in fact be brittle
and have reduced strength and toughness, for aggressive drilling
and/or cutting applications, and for this reason would likely
fail in application and exhibit a reduced service life due to
premature spalling or chipping.
It is to be understood that the depth of the thermally
stable region from at least a portion of the working or cutting
surface is represented as being a nominal, average value arrived
at by taking a number of measurements at preselected intervals
along this region and then determining the average value for all
of the points. The region remaining within the PCD body or
compact beyond this thermally stable region is understood to
still contain the catalyst material.
Additionally, when the PCD body to be treated includes a
substrate, i.e., is provided in the form of a PCD compact, it is
desired that the selected depth of the region to be rendered
thermally stable be one that allows a sufficient depth of region
remaining in the PCD compact that is untreated to not adversely
17
CA 02520319 2005-09-21
impact the attachment or bond formed between the diamond body
and the substrate, e.g., by solvent metal infiltration during
the HPHT process. Tn an example PCD compact embodiment, it is
desired that the untreated or remaining region within the
diamond body have a thickness of at least about 0.01 mm as
measured from the substrate. It is, however, understood that
the exact thickness of the PCD region containing the catalyst
material next to the substrate can and will vary depending on
such factors as the size and configuration of the compact, i.e.,
the smaller the compact diameter the smaller the thickness, and
the particular PCD compact application.
In an example embodiment, the selected region of the PCD
body is rendered thermally stable by removing substantially all
of the catalyst material therefrom by exposing the desired
surface or surfaces to acid leaching, as disclosed for example
in U.S. Patent No. 4,224,380, which is incorporated herein by
reference. Generally, after the PCD body or compact is made by
HPHT process, the identified surface or surfaces, e.g., at least
a portion of the working or cutting surfaces, are placed into
contact with the acid leaching agent for a sufficient period of
time to produce the desired leaching or catalyst material
depletion depth.
Suitable leaching agents for treating the selected region
to be rendered thermally stable include materials selected from
the group consisting of inorganic acids, organic acids, mixtures
and derivatives thereof. The particular leaching agent that is
selected can depend on such factors as the type of catalyst
material used, and the type of other non-diamond metallic
materials that may be present in the PCD body, e.g., when the
PCD body is formed using synthetic diamond powder. While
removal of the catalyst material from the selected region
operates to improve the thermal stability of the selected
region, it is known that PCD bodies especially formed from
synthetic diamond powder can include, in addition to the
18
CA 02520319 2005-09-21
catalyst material, noncatalyst materials, such as other metallic
elements that can also contribute to thermal instability.
For example, one of the primary metallic phases known to exist
in the PCD body formed from synthetic diamond powder is
tungsten. It is, therefore, desired that the leaching agent
selected to treat the selected PCD body region be one capable of
removing both the catalyst material and such other known
metallic materials. In an example embodiment, suitable leaching
agents include hydrofluoric acid (HF), hydrochloric acid (HC1),
nitric acid (HN03), and mixtures thereof.
In an example embodiment, where the diamond body to be
treated is in the form of a PCD compact, the compact is prepared
for treatment by protecting the substrate surface and other
portions of the PCD body adjacent the desired treated region
from contact (liquid or vapor) with the leaching agent. Methods
of protecting the substrate surface include covering, coating or
encapsulating the substrate and portion of PCD body with a
suitable barrier member or material such as wax, plastic or the
like.
Referring to FIG. 12, in a preferred embodiment, the
compact substrate surface and portion of the diamond body is
protected by using an acid-resistant fixture 106 that is
specially designed to encapsulate the desired surfaces of the
substrate and diamond body. Specifically, the fixture 106 is
configured having a cylindrical body 108 within an inside
surface diameter 110 that is sized to fit concentrically around
the outside surface 111 of the compact 113. The fixture inside
surface 110 can include a groove 112 extending circumferentially
therearound and that is positioned adjacent to an end 114 of the
fixture. The groove is sized to accommodate placement of a seal
115, e.g., in the form of an elastomeric O-ring or the like,
therein. Alternatively, the fixture can be configured without a
groove and a suitable seal can simply be interposed between the
opposed respective compact and fixture outside and inside
19
CA 02520319 2005-09-21
diameter surfaces. When placed around the outside surface of
the compact, the seal operates to provide a leak-tight seal
between the compact and the fixture to prevent unwanted
migration of the leaching agent therebetween.
In a preferred embodiment, the fixture 106 includes an
opening 117 in its end that is axially opposed to end 114. The
opening operates both to prevent an unwanted build up of
pressure within the fixture when the PCD compact is loaded
therein (which pressure could operate to urge the compact away
from its loaded position within the fixture), and to facilitate
the removal of the compact from the fixture once the treatment
process is completed (e. g., the opening provides an access port
for pushing the compact out of the fixture by mechanical or
pressure means). During the process of treating the compact,
the opening 117 is closed using a suitable seal element 119,
e.g., in the form of a removable plug or the like.
In preparation for treatment, the fixture is positioned
axially over the PCD compact and the compact is loaded into the
fixture with the compact working surface directly outwardly
towards the fixture end 114. The compact is then positioned
within the fixture so that the compact working surface 121
projects a desired distance outwardly from sealed engagement
with the fixture inside wall. Positioned in this manner within
the fixture, the compact working surface 121 is freely exposed
to make contact with the leaching agent via fixture opening 123
positioned at end 114.
The PCD compact 113 and fixture 106 form an assembly that
are then placed into a suitable container that includes a
desired volume of the leaching agent 125. In a preferred
embodiment, the level of the leaching agent within the container
is such that the diamond body working surface 121 exposed within
the fixture is completely immersed into the leaching agent. In
a preferred embodiment, a sheet of perforated material 127,
e.g., in the form of a mesh material that is chemically
CA 02520319 2005-09-21
resistant to the leaching agent, can be placed within the
container and interposed between the assembly and the container
surface to provide a desired distance between the fixture and
the container. The use of a perforated material ensures that,
although it is in contact with the assembly, the leaching agent
will be permitted to flow to the exposed compact working surface
to produce the desired leaching result.
FIGS. 3 and 4 illustrate an embodiment of the TSPCD
construction 26 of this invention after its has been treated to
IO render a selected region of the PCD body thermally stable. The
construction comprises a thermally stable region 28 that extends
a selected depth ~~D~~ from a working or cutting surface 30 of the
diamond body 32. The remaining region 34 of the diamond body 32
extending from the thermally stable region 28 to the substrate
36 comprises PCD having the catalyst material intact. In a
first example embodiment, the thermally stable region extends a
depth of approximately 0.045 mm from the working or cutting
surface. In a second example embodiment, the thermally stable
region extends a depth of approximately 0.075 mm from the
working or cutting surface. Again, it is to be understood that
the exact depth of the thermally stable region can and will vary
within the ranges noted above depending on the particular end
use drilling and or cutting applications.
Additionally, as mentioned briefly above, it is to be
understood that the TSPCD construction described above and
illustrated in FIGS. 3 and 4 are representative of a single
embodiment of this invention for purposes of reference, and that
TSPCD constructions other than that specifically described and
illustrated are within the scope of this invention. For
example, TSPCD constructions comprising a diamond body having a
thermally stable region and then two or more other regions are
possible, wherein a region interposed between the thermally
stable region and the region adjacent the substrate may be a
transition region having a diamond density and/or formed from
21
CA 02520319 2005-09-21
diamond grains sized differently from that of the other diamond-
containing regions.
FIG. 5 illustrates the material microstructure 38 of the
TSPCD construction of this invention and, more specifically, a
section of the thermally stable region of the TSPCD
construction. The thermally stable region comprises the
intercrystalline bonded diamond made up of the plurality of
bonded together diamond grains 40, and a matrix of interstitial
regions 42 between the diamond grains that are now substantially
free of the catalyst material. The thermally stable region
comprising the interstitial regions free of the catalyst
material is shown to extend a distance "D" from a working or
cutting surface 44 of the TSPCD construction. In an example
embodiment, the distance "D" is identified and measured by cross
sectioning a TSPCD construction and using a sufficient level of
magnification to identify the interface between the first and
second regions. As illustrated in FIG. 5, the interface is
generally identified as the location within the diamond body
where a sufficient population of the catalyst material 46 is
shown to reside within the interstitial regions.
The so-formed thermally stable region of TSPCD
constructions of this invention is not subject to the thermal
degradation encountered in the remaining areas of the PCD
diamond body, resulting in improved thermal characteristics.
The remaining region of the diamond body extending from depth
"D" has a material microstructure that comprises PCD, as
described above and illustrated in FIG. 1, that includes
catalyst material 46 disposed within the interstitial regions.
As noted above, the location of the working or cutting
surface for TSPCD constructions of this invention can and will
vary depending on the particular cutting or wear application.
In an example embodiment, the wear, cutting and/or working
surface can extend along and/or include the upper surface of the
construction embodiment illustrated in FIG. 2. For example,
22
CA 02520319 2005-09-21
FIG. 6 illustrates an example embodiment TSPCD construction 48
of this invention comprising a working surface 50 that extends
from and includes a substantially planar upper surface 52 of the
construction and may be considered to also include a beveled
S surface 54 that defines a circumferential edge of the upper
surface. In this embodiment, the thermally stable region 56
extends the selected depth into the diamond body 57 from both
the upper and beveled surfaces 52 and 54.
Accordingly, in this example embodiment, the upper and
beveled surfaces 52 and 54 are understood to be the working
surfaces of the construction. Alternatively, TSPCD
constructions of this invention may include a working surface, a
first beveled or radiused surface, a second beveled or radiused
surface, or other surface feature interposed between the upper
surface and a side surface, as well as the side surface. In
such case, the first beveled surface may be considered part of
the working surface and any subsequent surface, especially if at
an angle greater than 65° with respect to a plane at the top
surface, considered part of the side surface. In general, the
side surface is understood to be any surface substantially
perpendicular to the upper surface of the constriction.
In such embodiment, prior to treating the PCD compact to
render the selected region thermally stable, the PCD compact is
formed to have such working surface, i.e., is formed by machine
process or the like to provide the desired the beveled surface
54 or other surface feature as discussed above. In an example
embodiment, the PCD compact is finished into its approximate
final dimension prior to treating, e.g., is machine finished
prior to leaching. Thus, a feature of TSPCD constructions of
this invention is that they include working or cutting surfaces,
independent of location or orientation, having a thermally
stable region extending a predetermined depth into the diamond
body that is not substantially altered subsequent to treating
and prior to use.
23
CA 02520319 2005-09-21
For certain applications, it has been discovered than an
improved degree of thermal stability can be realized by
extending and/or providing a thermally stable region along the
side surface of the construction. The thermally stable side
S surface may or may not be an extension of the working or cutting
surface. As illustrated in FIG. 6, the thermally stable region
56 extends along a side surface 58 of the construction and
includes the beveled surface 54. As noted above, the side
surface 58 of the construction is oriented substantially
perpendicular to the upper surface 52, and extends from the
bevel surface to the substrate 60.
Extending the thermally stable region to along the side
surface 58 of the construction operates to improve the life of
the construction when placed into operation, e.g., when used as
a cutter in a drill bit placed into a subterranean drilling
application. This is believed to occur because the enhanced
thermal conductivity provided by the thermally stable side
surface portion operates to help conduct heat away from the
working surface of the construction, thereby increasing the
thermal gradient of the TSPCD construction, its thermal
resistance and service life.
In an example embodiment, where the TSPCD construction is
provided in the form of a cutting element for use in a drill bit
and the cutting element includes a working surface comprising an
upper surface and/or a beveled or other intermediate surface
feature extending between the upper surface and the side
surface, the thermally stable region may extend axially from the
working surface along the side surface of the construction for a
distance or length that will vary depending on such factors as
the particular material make up of the TSPCD construction, its
configuration, and its application. Generally, it is desired
that the thermally stable region extend a length that is
sufficient to provide a desired improvement in the construction
thermal stability and service life.
24
CA 02520319 2005-09-21
Tn an example embodiment, the thermally stable region of
the TSPCD construction can extend along the side surface 58 for
a length of about 25 to 100 percent of the total length of the
side surface as measured from the working surface. The total
length of the side surface is that which extends between the
working surface and an opposite end of the PCD body or, between
the working surface and interface of the substrate 60. In an
example embodiment, the thermally stable region can extend along
the side surface of the construction for a length that is at
least about 40 percent of the total length, or preferably that
is at least about 50 percent of the total length.
The thermally stable region extending along the side
surface can be formed in the manner described above by
selectively covering only that portion of the side surface that
is not to be treated along with the substrate. In an example
embodiment, where a fixture as described above is used, the
fixture can be positioned over a portion of the construction to
cover the substrate and any portion of the side surface not to
be treated so that both remain protected from the leaching
agent. In the event that it is desired that the thermally
stable region extend along the entire length of the side
surface, then appropriate steps are taken using the fixture or
other means to protect only the surface of the substrate from
being exposed to the leaching agent. In an example embodiment,
the thermally stable region extending along such side surface is
formed after the construction has been finished to an
approximate final dimension as noted above.
The depth of the thermally stable region extending along
the side surface can vary depending on a number of factors, such
as the material make up, size, configuration and application of
the construction. In an example embodiment, the thermally
stable region extends from the side surface a depth within the
diamond body of between about o.02 micrometers to 1 mm. In some
cases it may be preferably between about 0.1 mm to 0.5 mm, and
CA 02520319 2005-09-21
more preferably between about 0.15 to 0.3 mm. It is generally
desired that the depth of the thermally stable region be
sufficient to provide a desired degree thermal stability,
hardness and/or toughness to provide the desired improvement in
service life. The same treatment techniques discussed above for
providing the thermally stable region depth beneath the working
surface can be used to provide the desired thermally stable
region depth extending from the side surface.
Additionally, in some embodiments, the depth of the
thermally stable region extending along the length of the side
surface may not be constant. For example, the thermally stable
region can be configured to change as a function of distance
from the working or cutting surface. In an example embodiment,
the depth can decrease or increase as a function of distance
from the working surface, thereby providing a tapered depth
profile. This profile can be a gradient or can be stepped. In
an example embodiment, the TSPCD construction has a thermally
stable region extending along the side surface having a tapered
depth profile that decreases as a function of distance from the
working surface.
The change in depth in such embodiments can be achieved by
varying the treatment or process parameters. for example by
varying the leaching time used along the side surface This can
be achieved by immersing the construction over a period of time
into the leaching agent, thereby subjecting the first immersed
portion of the side surface to a longer leaching time than a
later immersed portion. Alternatively, the change in depth can
be achieved by controlling certain features of the construction
itself, e.g., by the selective use of differently sized diamond
grains to form different regions along the side surface or
throughout the diamond body, which grain side different may
influence leaching efficiency. This may also result using PDC
construction having a diamond density that varies along the
length of the side surface.
26
CA 02520319 2005-09-21
While the feature of forming a thermally stable region
extending along a side surface portion of TSPCD construction has
been described above and illustrated in FIG. 6, it is to be
understood according to the practice of this invention that such
extended thermally stable regions can be used in conjunction
with working or cutting surfaces of any configuration,
orientation or placement on the TSPCD construction.
Additionally, while the feature of an extended thermally
stable region extending along a side surface of TSPCD
constructions of this invention has been disclosed in
conjunction with a TSPCD construction having a thermally stable
region extending a depth from a working or cutting surface,
other embodiments in accordance with the invention may include
TSPCD constructions configured to have a thermally stable region
extending along a side surface of the construction without a
thermally stable region extending a depth along the working or
top surface. Such TSPCD constructions, having a thermally
stable region extending into the diamond body along a length of
the side surface and not extending a depth beneath the working
or cutting surface, can be formed by using the same general
techniques described above, except that extra measures are used
to protect the working or cutting surface from being exposed to
during treatment to form the thermally stable region. This can
be done by using the same types of barrier materials disclosed
above, or by using a special fixture designed to be placed over
the working or cutting surface, to protect the working or
cutting surfaces from exposure during treatment. Alternatively,
a technique may be used wherein the working or cutting surface
is protected by simply not being immersed into any such treating
agent, or by a combination of not being immersed and also being
protected.
Selected example TSPCD constructions of this invention will
be better understood with reference to the following examples:
27
CA 02520319 2005-09-21
Example 1 - TSPCD Construction
Synthetic diamond powder having an average grain size of
approximately 20 micrometers was mixed together for a period of
approximately 1 hour by conventional process. The resulting
mixture included approximately six percent by volume cobalt
solvent metal catalyst, and WC-Co based on the total volume of
the mixture, and was cleaned. The mixture was loaded into a
refractory metal container with a cemented tungsten carbide
substrate and the container was surrounded by pressed salt
(NaCl) and this arrangement was placed within a graphite heating
element. This graphite heating element containing the pressed
salt and the diamond powder/substrate encapsulated in the
refractory container was then loaded in a vessel made of a high-
temperature/high-pressure self-sealing powdered ceramic material
formed by cold pressing into a suitable shape. The self-sealing
powdered ceramic vessel was placed in a hydraulic press having
one or more rams that press anvils into a central cavity. The
press was operated to impose a pressure and temperature
condition of approximately 5,500 MPa and approximately 1450°C on
the vessel for a period of approximately 20 minutes.
During this HPHT processing, the cobalt solvent metal
catalyst infiltrated through the diamond powder and catalyzed
intercrystalline diamond-to-diamond bonding to form a PCD body
having a material microstructure as discussed above and
illustrated in FIG. 1. Additionally, the solvent metal catalyst
in the substrate infiltrated into the diamond powder mixture to
form a bonded attachment with the PCD body, thereby resulting in
the formation of a PCD compact. The container was removed from
the device, and the resulting PCD compact was removed from the
container. Prior to leaching, the PCD compact was finished
machined and ground to achieve the desired compact finished
dimensions, size and configuration. The resulting PCD compact
had a diameter of approximately 16 mm, the PCD diamond body had
28
CA 02520319 2005-09-21 '
a thickness of approximately 3 mm, and the substrate had a
thickness of approximately 13 mm. The PCD compact had a beveled
surface defining a circumferential edge of the upper surface.
The PCD compact had a working or cutting surface defined by the
upper surface and the beveled edge and a side surface.
A protective fixture as described above was placed
concentrically around the outside surface of the compact to
cover the substrate and a portion of the diamond body. The
fixture was formed from a plastic material capable of surviving
exposure to the leaching agent, and included an elastomeric O-
ring disposed circumferentially therein around an inside fixture
surface adjacent an end of the fixture. The fixture was
positioned over the compact so that a portion of the diamond
body desired to be rendered thermally stable was exposed
therefrom. The O-ring provided a desired seal between the PCD
compact and fixture. The PCD compact and fixture assembly was
placed with the compact exposed portion immersed into a volume
of leaching agent disposed within a suitable container. The
leaching agent was a mixture of HF and HN03 that was provided at
a temperature of approximately 22~C.
The depth that the PCD compact was immersed into the
leaching agent was a depth sufficient to provide a thermally
stable region along the portion of the diamond body comprising
the working surfaces, including the upper surface and beveled
surface for this particular example. As noted above, if
desired, the depth of immersion can be deeper to extend beyond
the beveled surface to include a portion of the PCD body side
surface extending from the working or cutting surfaces. In this
example, the immersion depth was approximately 4 mm. The PCD
compact was immersed on the leaching agent for a period of
approximately 150 minutes. After the designated treatment time
had passed, the PCD compact and fixture assembly were removed
from the leaching agent and the compact was removed from the
protective fixture.
29
CA 02520319 2005-09-21
It is to be understood that the time period for leaching to
achieve a desired thermally stable region according to the
practice of this invention can and will vary depending on a
number of factors, such as the diamond volume density, the
diamond grain size, the leaching agent, and the temperature of
the leaching agent.
The resulting TSPCD construction formed according to this
example had a thermally stable region that extended from the
working surfaces a distance into the diamond body of
approximately 0.045 mm.
Example 2 - TSPCD Construction
A TSPCD construction of this invention was prepared
according to the process described above for example 1 except
that the treatment for providing a thermally stable region in
the PCD body was conducted for longer period of time.
Specifically, the PCD compact was immersed on the leaching agent
for a period of approximately 300 minutes. After the designated
treatment time had passed, the PCD compact and fixture assembly
was removed from the leaching agent and PCD compact was removed
from the protective fixture. The resulting TSPCD construction
formed according to this example had a thermally stable region
that extended from the working surfaces a distance into the
diamond body of approximately 0.075 mm.
A feature of TSPCD constructions of this invention is that
they include a defined thermally stable region within a PCD body
that provides an improved degree of wear and abrasion
resistance, when compared to conventional PCD, while at the same
time providing a desired degree of strength and toughness unique
to conventional PCD that has been rendered thermally stable by
either removing the catalyst material from a more substantial
portion of the diamond body or by removing the catalyst material
entirely therefrom. A further feature of TSPCD constructions of
CA 02520319 2005-09-21
this invention is that they include a thermally stable region
that extends a determined depth from at least a portion of a
working or cutting surface and/or that extends a depth along a
side surface the construction, thereby operating to provide a
further enhanced degree of thermal stability and resistance
during cutting and/or wear service to thereby provide improved
service life.
A further feature of TSPCD constructions of this invention
is that they can be formed from natural diamond grains that,
unlike synthetic diamond grains, do not include catalyst metal
and metallic impurities entrapped in the diamond crystals
themselves that can limit the extent to which optimal or a
desired degree of thermal stability can be achieved by the
treatment techniques described above. Accordingly, in certain
applications calling for a high degree of thermally stability,
the use of natural diamond can be used to achieve this result.
A still further feature of TSPCD constructions of this
invention is that the thermally stable region is formed in a
manner that does not adversely impact the compact substrate.
Specifically, the treatment process is carefully controlled to
ensure that a sufficient region within the PCD body adjacent the
substrate remains unaffected and includes the catalyst material,
thereby ensuring that the desired bond between the substrate and
PCD body remain intact. Additionally, during the treatment
process, means are used to protect the surface of the substrate
from liquid or vapor contact with the leaching agent, to ensure
that the substrate is in no way adversely impacted by the
treatment.
A still further feature of TSPCD constructions of this
invention is that they are provided in the form of a compact
comprising a PCD body, having a thermally stable region, which
body is bonded to a metallic substrate. This enables TSPCD
constructions of this invention to be attached with different
types of well known cutting and wear devices such as drill bits
31
CA 02520319 2005-09-21
and the like by conventional attachment techniques such as by
brazing or welding.
TSPCD constructions of this invention can be used in a
number of different applications, such as tools for mining,
cutting, machining and construction applications, where the
combined properties of thermal stability, wear and abrasion
resistance, and strength and toughness are highly desired.
TSPCD constructions of this invention are particularly well
suited for forming working, wear and/or cutting components in
machine tools and drill and mining bits such as roller cone rock
bits, percussion or hammer bits, diamond bits, and shear
cutters.
FIG. 7 illustrates an embodiment of a TSPCD construction of
this invention provided in the form of an insert 62 used in a
wear or cutting application in a roller cone drill bit or
percussion or hammer drill bit. For example, such TSPCD inserts
62 are constructed having a substrate portion 64, formed from
one or more of the substrate materials disclosed above, that is
attached to a PCD body 66 having a thermally stable region. In
this particular embodiment, the insert comprises a domed working
surface 68, and the thermally stable region is positioned along
the working surface and extends a selected depth therefrom into
the diamond body. The insert can be pressed or machined into
the desired shape or configuration prior to the treatment for
rendering the selected region thermally stable. It is to be
understood that TSPCD constructions can be used with inserts
having geometries other than that specifically described above
and illustrated in FIG. 7.
FIG. 8 illustrates a rotary or roller cone drill bit in the
form of a rock bit 70 comprising a number of the wear or cutting
TSPCD inserts 72 disclosed above and illustrated in FIG. 7. The
rock bit 70 comprises a body 74 having three legs 76 extending
therefrom, and a roller cutter cone 78 mounted on a lower end of
each leg. The inserts 72 are the same as those described above
32
CA 02520319 2005-09-21
comprising the TSPCD constructions of this invention, and are
provided in the surfaces of each cutter cone 78 for bearing on a
rock formation being drilled.
FTG. 9 illustrates the TSPCD insert described above and
illustrated in FIG. 7 as used with a percussion or hammer bit
80. The hammer bit generally comprises a hollow steel body 82
having a threaded pin 84 on an end of the body for assembling
the bit onto a drill string (not shown) for drilling oil wells
and the like. A plurality of the inserts 86 are provided in the
surface of a head 88 of the body 82 for bearing on the
subterranean formation being drilled.
FIG. 10 illustrates a TSPCD construction of this invention
as embodied in the form of a shear cutter 90 used, for example,
with a drag bit for drilling subterranean formations. The TSPCD
shear cutter comprises a PCD body 92 that is sintered or
otherwise attached to a cutter substrate 94 as described above.
The PCD body includes a working or cutting surface 96 that is
formed from the thermally stable region of the PCD body. As
discussed and illustrated above, the shear cutter working or
cutting surface can include the upper surface and a beveled
surface defining a circumferential edge of the upper. The shear
cutter has a PCD body including a thermally stable region that
can extend a depth from such working surfaces and/or a depth
from the side surface extending axially a length away from the
working surfaces to provide an enhanced degree of thermal
stability and thermal resistance to the cutter. It is to be
understood that TSPCD constructions can be used with shear
cutters having geometries other than that specifically described
above and illustrated in FIG. 10.
FIG. 11 illustrates a drag bit 98 comprising a plurality of
the TSPCD shear cutters 100 described above and illustrated in
FIG. 10. The shear cutters are each attached to blades 102 that
extend from a head 104 of the drag bit for cutting against the
subterranean formation being drilled. Because the TSPCD shear
33
CA 02520319 2005-09-21
cutters of this invention include a metallic substrate, they are
attached to the blades by conventional method, such as by
brazing or welding.
Other modifications and variations of TSPCD constructions
as practiced according to the principles of this invention will
be apparent to those skilled in the art. It is, therefore, to
be understood that within the scope of the appended claims, this
invention may be practiced otherwise than as specifically
described.
34
