U.S. patent application number 08/980471 was filed with the patent office on 2001-06-28 for enhanced non-planar drill insert.
Invention is credited to JENSEN, KENNETH M..
Application Number | 20010004946 08/980471 |
Document ID | / |
Family ID | 25527579 |
Filed Date | 2001-06-28 |
United States Patent
Application |
20010004946 |
Kind Code |
A1 |
JENSEN, KENNETH M. |
June 28, 2001 |
ENHANCED NON-PLANAR DRILL INSERT
Abstract
A cutting element, or insert, is provided for use with drills
used in the drilling and boring of subterranean formations. This
new insert has improved wear characteristics while maximizing the
manufacturability and cost effectiveness of the insert. This
invention accomplishes these objectives by employing a
superabrasive diamond layer of increased depth and by making use of
diamond layer surface shape that is generally convex.
Inventors: |
JENSEN, KENNETH M.; (OREM,
UT) |
Correspondence
Address: |
LLOYD W SADLER
MCCARTHY & SADLER
39 EXCHANGE PLACE
SUITE 100
SALT LAKE CITY
UT
84111
|
Family ID: |
25527579 |
Appl. No.: |
08/980471 |
Filed: |
November 28, 1997 |
Current U.S.
Class: |
175/428 ;
175/420.1 |
Current CPC
Class: |
E21B 10/5673 20130101;
E21B 10/5735 20130101; E21B 10/573 20130101 |
Class at
Publication: |
175/428 ;
175/420.1 |
International
Class: |
E21B 010/36 |
Claims
I claim:
1. A cutting element insert for use on a bit for drilling
subterranean formations, comprising: (A) a substrate having a top
surface; and (B) a layer of superabrasive material, having an
interface surface, bonded to said top surface of said substrate and
an external contact surface, wherein said layer of superabrasive
material completely covers said top surface of said substrate and
wherein said external contact surface is of a generally
hemispherical shape.
2. A cutting element insert as recited in claim 1, wherein said
substrate is a carbide selected from the group consisting of
tungsten carbide, niobium carbide, zirconium carbide, hafnium
carbide, vanadium carbide, tantalum carbide, and titanium
carbide.
3. A cutting element insert as recited in claim 1, wherein said
layer of superabrasive material is composed of polycrystalline
diamond.
4. A cutting element insert as recited in claim 1, wherein said
layer of superabrasive material further comprises: a cutting
surface and a center axis.
5. A cutting element insert as recited in claim 1, wherein said
layer of superabrasive material is between 0.040 inches and 2.0
inches in thickness.
6. A cutting element insert as recited in claim 1, wherein said
substrate is composed of cemented tungsten carbide.
7. A cutting element insert as recited in claim 1, wherein said
layer of superabrasive material is bonded to said substrate by
ultra-high pressure sintering.
8. A cutting element insert as recited in claim 1, wherein said
layer of superabrasive material is bonded to said substrate by
pressing.
9. A cutting element insert as recited in claim 1, wherein said
layer of superabrasive material is bonded to said substrate by
brazing.
10. A cutting element insert as recited in claim 1, wherein said
layer of superabrasive material is composed of cubic boron
nitride.
11. A cutting element insert for use on a bit for drilling
subterranean formations, comprising: (A) a substrate having a top
surface; and (B) a layer of superabrasive material, having an
interface surface, bonded to said top surface of said substrate and
an external contact surface, wherein said layer of superabrasive
material completely covers said top surface of said substrate and
wherein said external contact surface is of a generally conical
shape.
12. A cutting element insert as recited in claim 11, wherein said
substrate is a carbide selected from the group consisting of
tungsten carbide, niobium carbide, zirconium carbide, hafnium
carbide, vanadium carbide, tantalum carbide, and titanium
carbide.
13. A cutting element insert as recited in claim 11, wherein said
layer of superabrasive material is composed of polycrystalline
diamond.
14. A cutting element insert as recited in claim 11, wherein said
layer of superabrsive material further comprises: a cutting surface
and a center axis.
15. A cutting element insert as recited in claim 11, wherein said
layer of superabrasive material is between 0.040 inches and 2.0
inches in thickness.
16. A cutting element insert as recited in claim 11, wherein said
substrate is composed of cemented tungsten carbide.
17. A cutting element insert as recited in claim 11, wherein said
layer of superabrasive material is bonded to said substrate by
sintering.
18. A cutting element insert as recited in claim 11, wherein said
layer of superabrasive material is bonded to said substrate by
pressing.
19. A cutting element insert as recited in claim 11, wherein said
layer of superabrasive material is bonded to said substrate by
brazing.
20. A cutting element insert as recited in claim 11, wherein said
layer of superabrasive material is composed of cubic boron nitride.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to devices for drilling and boring
through subterranean formations. More specifically, this invention
relates to polycrystalline diamond compacts ("PDCs"), also known as
cutting elements or diamond inserts, which are intended to be
installed as the cutting element of a drill bit to be used for
boring through rock in any application, such as oil, gas, mining,
and/or geothermal exploration, requiring drilling through
geological formations. Still more specifically, this invention
relates to polycrystalline diamond inserts which have a surface
topography formed integral to an otherwise spherical, conical, or
other uniform geometric shape, to increase stress at the
insert/rock interface, thereby inducing the rock to fail while
requiring the expenditure of less overall energy and introducing
little, if any, additional internal stresses to the insert.
[0003] 2. Description of Related Art
[0004] Three types of drill bits are most commonly used for
penetrating geologic formations. These are: (1) percussion bits;
(2) rolling cone bits, also referred to as rock bits; and (3) drag
bits, or fixed cutter rotary bits. Each type of bits may employ
polycrystalline diamond inserts as the primary cutting device.
[0005] In addition to the drill bits discussed above,
polycrystalline diamond inserts may also be used with other down
hole tools, including but not limited to: reamers, stabilizers, and
tool joints. Similar devices used in the mining industry may also
use this invention.
[0006] Percussion bits penetrate through subterranean geologic
formations by an extremely rapid series of impacts. The impacts may
be combined with a simultaneous rotations of the bit. An exemplary
percussion bit is shown in FIG. 1b. The reader is directed to the
following list of related art patents for further discussion of
percussion bits.
[0007] Rolling cone bits currently make up the largest number of
bits used in drilling geologic formations. Rolling cone bits have
as their primary advantage the ability to penetrate hard geologic
formations while being generally available at a relatively low
cost. Typically, rolling cone bits operate by rotating three cones,
each oriented substantially transverse to the bits axis and in a
triangular arrangement, with the narrow end of each cone facing a
point in the direct center of the bit. An exemplary rolling cone
bit is shown in FIG. 1a.
[0008] A rolling cone bit cuts through rock by the crushing and
scraping action of the abrasive inserts embedded in the surface of
the rotating cone. These abrasive inserts are generally composed of
cemented tungsten carbide, but may also include polycrystalline
diamond coated cemented tungsten carbide, where increased wear
performance is required.
[0009] The primary application of this PDC invention is currently
believed to be in connection with percussion and rolling cone bits,
although alternative embodiments of this invention may find
application in connection with other drilling tools.
[0010] A third type of bit is the drag bit, also known as the fixed
cutter bit. An example of a drag bit is shown in FIG. 2. The drag
bit is designed to be rotated about its longitudinal axis. Most
drag bits employ PDCs which are brazed into the cutting blade of
the bit. The PDCs then shear the rock as the bit is rotated about
its longitudinal axis.
[0011] While it is expected that this invention will find primary
application in percussion and rolling cone bits, some use in drag
bits may also be feasible.
[0012] A polycrystalline diamond compact ("PDC"), or cutting
element, is typically fabricated by placing a cemented tungsten
carbide substrate into a refactory metal container ("can") with a
layer of diamond crystal powder placed into the can adjacent to one
face of the substrate. The can is then covered. A number of such
can assemblies are loaded into a high pressure cell made from a
soft ductile solid material such as pyrophyllite or talc. The
loaded high pressure cell is then placed in an ultra-high pressure
press. The entire assembly is compressed under ultra-high pressure
and temperature conditions. This causes the metal binder from the
cemented carbide substrate to become liquid and to "sweep" from the
substrate face through the diamond grains and to act as a reactive
liquid phase to promote the sintering of the diamond grains. The
sintering of the diamond grains causes the formation of a
polycrystalline diamond structure. As a result the diamond grains
become mutually bonded to form a diamond mass over the substrate
face. The metal binder may remain in the diamond layer within the
pores of the polycrystalline structure or, alternatively, it may be
removed via acid leeching and optionally replaced by another
material forming so-called thermally stable diamond ("TSD").
Variations of this general process exist and are described in the
related art. This detail is provided so the reader may become
familiar with the concept of sintering a diamond layer onto a
substrate to form a PDC insert. For more information concerning
this process, the reader is directed to U.S. Pat. No. 3,745,623,
issued to Wentorf Jr. et al., on Jul. 7, 1973.
[0013] Existing PDCs often exhibit durability problems in cutting
through tough geologic formations, where the diamond working
surface may experience high but transient stress loads. Under such
conditions, existing PDCs have a general tendency to crack, spall,
and break. Similarly, existing PDCs are relatively weak when placed
under high loads from a variety of angles. These problems of
existing PDCs are further exacerbated by the dynamic nature of both
normal and torsional loading during the drilling process, during
which the bit face moves into and out of contact with the uncut
material forming the bottom of the well bore.
[0014] For optimal performance, the interface between the diamond
layer and the tungsten carbide substrate must be capable of
sustaining the high residual stresses that arise from thermal
expansion and bulk modulus mismatches between the two materials.
These differences create high residual stress at the interface as
the materials are cooled from the high temperature and pressure
process. Residual stress can be deleterious to the life of the PDC
cutting elements, or inserts, during drilling operations, when high
tensile stresses in the substrate or diamond layer may cause
fracture, spalling, or complete delamination of the diamond layer
from the substrate.
[0015] Typical prior PDCs have a relatively thin diamond layer,
generally between 0.020 and 0.040 inches in thickness. The cylinder
of carbide to which the diamond layer is attached is generally at
least three times thicker than the diamond layer.
[0016] Diamond is used as a drilling material primarily because of
its extreme hardness and abrasion resistance. However, diamond also
has a major drawback. Diamond, as a cutting material, has very poor
toughness, that is, it is very brittle. Therefore, anything that
further contributes to reducing the toughness of the diamond,
substantially degrades its durability.
[0017] A number of other approaches and applications of PDCs are
well established in related art. The applicant includes the
following references to related art patents for the reader's
general familiarization with this technology.
[0018] U.S. Pat. No. 4,109,737 describes a rotary drill bit for
rock drilling comprising a plurality of cutting elements mounted by
interference-fit in recesses in the crown of the drill bit.
[0019] U.S. Pat. No. 4,604,106 reveals a composite polycrystalline
diamond compact comprising at least one layer of diamond crystals
and precemented carbide pieces which have been pressed under
sufficient heat and pressure to create a composite polycrystalline
material wherein polycrystalline diamond and the precemented
carbide pieces are interspersed in one another.
[0020] U.S. Pat. No. 4,694,918 describes an insert that has a
tungsten carbide body and at least two layers at the protruding
drilling portion of the insert. The outermost layer contains
polycrystalline diamond and the remaining layers adjacent to the
polycrystalline diamond layer are transition layers containing a
composite of diamond crystals and precemented tungsten carbide, the
composite having a higher diamond crystal content adjacent to the
polycrystalline diamond layer and a higher precemented tungsten
carbide content adjacent to the tungsten carbide layer.
[0021] U.S. Pat. No. 4,858,707 describes a diamond insert for a
rotary drag bit consists of an insert stud body that forms a first
base end and a second cutter end.
[0022] U.S. Pat. No. 4,997,049 describes a tool insert having a
cemented carbide substrate with a recess formed in one end of the
substrate and having abrasive compacts located in the recesses and
bonded to the substrate.
[0023] U.S. Pat. No. 5,154,245 relates to a rock bit insert of
cemented carbide for percussive or rotary crushing rock drilling.
The button insert is provided with one or more bodies of
polycrystalline diamond in the surface produced by high pressure
and high temperature in the diamond stable area. Each diamond body
is completely surrounded by cemented carbide except the top
surface.
[0024] U.S. Pat. No. 5,217,081 relates to a rock bit insert of
cemented carbide provided with one or more bodies or layers of
diamond and/or cubic boron nitride produced at high pressure and
high temperature in the diamond or cubic boron nitride stable area.
The body of cemented carbide has a multi-structure containing
eta-phase surrounded by a surface zone of cemented carbide free of
eta-phase and having a low content of cobalt in the surface and a
higher content of cobalt next to the eta-phase zone.
[0025] U.S. Pat. No. 5,264,283 relates to buttons, inserts and
bodies that comprise cemented carbide provided with bodies and/or
layers of CVD- or PVD-fabricated diamond and then high
pressure/high temperature treated in the diamond stable area.
[0026] U.S. Pat. No. 5,304,342 describes a sintered product useful
for abrasion- and impact-resistant tools and the like, comprising
an iron-group metal binder and refractory metal carbide
particles.
[0027] U.S. Pat. No. 5,335,738 relates to a button of cemented
carbide. The button is provided with a layer of diamond produced at
high pressure and high temperature in the diamond stable area. The
cemented carbide has a multi-phase structure having a core that
contains eta-phase surrounded by a surface zone of cemented carbide
free of eta-phase.
[0028] U.S. Pat. No. 5,370,195 describes a drill bit having a means
for connecting the bit to a drill string and a plurality of inserts
at the other end for crushing the rock to be drilled, where the
inserts have a cemented tungsten carbide body partially embedded in
the drill bit and at least two layers at the protruding drilling
portion of the insert. The outermost layer contains polycrystalline
diamond and particles of carbide or carbonitride.
[0029] U.S. Pat. No. 5,379,854 discloses a cutting element which
has a metal carbide stud with a plurality of ridges formed in a
reduced or full diameter hemispherical outer end portion of said
metal carbide stud. The ridges extend outwardly beyond the outer
end portion of the metal carbide stud. A layer of polycrystalline
material, resistant to corrosive and abrasive materials, is
disposed over the ridges and the outer end portion of the metal
carbide stud to form a hemispherical cap.
[0030] U.S. Pat. No. 5,544,713 discloses a cutting element with a
metal carbide stud that has a conic tip formed with a reduced
diameter hemispherical outer tip end portion of said metal carbide
stud. A corrosive and abrasive resistant polycrystalline material
layer is also disposed over the outer end portion of the metal
carbide stud to form a cap, and an alternate conic form has a flat
tip face. A chisel insert has a transecting edge and opposing flat
faces, which chisel insert is also covered with a polycrystalline
diamond compact layer.
[0031] U.S. Pat. No. 5,624,068 describes buttons, inserts and
bodies for rock drilling, rock cutting, metal cutting and wear part
applications, where the buttons or inserts or bodies comprise
cemented carbide provided with bodies and/or layers of CVD- or
PVD-fabricated diamond and then HP/HT treated in a diamond stable
area.
[0032] Each of the aforementioned patents and elements of related
art is hereby incorporated by referenced in its entirety for the
material disclosed therein.
SUMMARY OF THE INVENTION
[0033] In drill bits which are used to bore through subterranean
geologic formations, it is desirable to provide an insert which has
increased durability. This invention provides this increased
durability by increasing the diamond layer thickness to decrease
the spalling failure of the diamond layer from the non-planar upper
surface of the insert and to reduce the residual stresses within
the insert, thereby permitting the insert to withstand greater
service loads.
[0034] Therefore, it is an object of this invention to improve
cutter durability by increasing the thickness of the diamond
layer.
[0035] It is a further object of this invention to improve cutter
durability by providing a diamond layer which provides full cutter
surface coverage.
[0036] It is a further object of this invention to provide a cutter
with improved ability to resist spalling failure of the diamond
layer.
[0037] It is a further object of this invention to provide a cutter
which is capable of withstanding greater service loads.
[0038] These and other objectives, features and advantages of this
invention, which will be readily apparent to those of ordinary
skill in the art upon review of the following drawings,
specification, and claims, are achieved by the invention as
described in this application.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1a depicts an exemplary related art roller cone earth
boring bit.
[0040] FIG. 1b depicts an exemplary related art percussion bit.
[0041] FIG. 2 depicts an exemplary related art drag or fixed cutter
bit.
[0042] FIG. 3 depicts a preferred embodiment of the invention
showing a full diamond cap.
[0043] FIG. 4 depicts a preferred embodiment of the invention
showing an increased diamond layer thickness.
[0044] FIG. 5 depicts a preferred embodiment of the invention
showing an increased diamond layer thickness in the center of the
insert.
[0045] FIG. 6 depicts a preferred embodiment of the invention
showing an increased diamond layer thickness in the periphery of
the insert.
[0046] FIG. 7 depicts a preferred embodiment of the invention
showing a full diamond cap on a generally conically shaped
insert.
[0047] FIG. 8 depicts a preferred embodiment of the invention
showing an increased diamond layer thickness on a generally
conically shaped insert.
[0048] FIG. 9 depicts a preferred embodiment of the invention
showing an increased diamond layer thickness in the center of a
generally conically shaped insert.
[0049] FIG. 10 depicts a preferred embodiment of the invention
showing an increased diamond layer thickness in the periphery of a
generally conically shaped insert.
DETAILED DESCRIPTION OF THE INVENTION
[0050] This invention is intended for use in cutting tools, most
typically roller cone bits, as shown in FIG. 1a, and percussion
bits, as shown in FIG. 1b. The typical rolling cone bit 101
includes three rotating cones 102, 103, 104. Each rotating cone
102, 103, 104 has a plurality of cutting teeth 107. Each insert
(also known as a drill insert, compact or PDC) is pressed into the
drill bit such that the diamond surface is exposed outside the bit.
FIG. 1b shows a standard percussion bit 109 with cemented carbide
button drill inserts 108, for percussion rock drilling. The diamond
coated inserts of this invention can be substituted for the carbide
button inserts 108 shown in FIG. 1b.
[0051] FIG. 2 depicts the top view of an example of a typical drag
bit 201. A number of inserts, which also could be of the type
described in this invention are shown 201a-t arranged in rows
emanating in a generally radial fashion from the approximate center
205 of the bit. It is expected by the inventor that the inserts of
this invention could be used on rolling cone, percussion and drag
bits of virtually any configuration.
[0052] In each embodiment of this invention the insert is composed
of essentially two materials: polycrystalline diamond, which covers
the cutting surface of the insert; and tungsten carbide. The
tungsten carbide region is the area of the insert that is brazed or
pressed into the bit body, while the polycrystalline diamond region
is the area of the insert that comes in contact with the geologic
formation during the drilling operation. In the present invention,
the quantity of diamond in the polycrystalline diamond layer is
significantly greater than used in prior art inserts. The present
invention also has a non-linear, hemispherical or conical shape and
is designed to cover the entire cutting surface of the insert. In
some embodiments of the invention the polycrystalline diamond layer
interfaces with the tungsten carbide region using a generally flat
interface, a generally convex interface, an extension of diamond
into the tungsten carbide region, and/or an extension of the
tungsten carbide into the diamond region. Each interface has its
own advantages and applications. Although the interfaces between
the diamond region and the substrate regions are shown as generally
smooth, it would also be possible to include in the interface a
variety of mechanical modifications (e.g., ridges, undulations or
dimples, or chemical modifications to enhance both the adhesion
between the regions, as well as the transfer of stress between the
diamond region and the substrate region. The polycrystalline
diamond regions of the present invention are thicker than typically
used because a thicker diamond layer provides a greater insert
life. As the drill is operated the diamond region of the insert
comes into direct physical contact with hard rock. The
polycrystalline diamond regions of the various embodiments of the
present invention are all essentially symmetrical around the center
axis of the insert. This symmetry permits the installation of the
insert without regard to the bit face.
[0053] The inserts, as described in this invention, although
typically constructed with polycrystalline diamond on a tungsten
carbide substrate, can, alternatively, use other materials, such as
cubic boron nitride or some other superabrasive material in place
of the polycrystalline diamond. Similarly, titanium carbide,
tantalum carbide, vandium carbide, niobium carbide, hafnium
carbide, or zirconium carbide can be used in place of the tungsten
carbide for the substrate. Such superabrasive materials and
substrate materials suitable for use in inserts are well known in
the art.
[0054] Typically, the inserts of this invention are formed by
sintering the diamond layer under high temperature and high
pressure conditions to the substrate, using a metal binder or
reactive liquid phase such as cobalt. The substrate may be brazed
or otherwise joined to an attachment member such as a stud or to a
cylindrical backing element to enhance its affixation to the bit
face. The cutting element may be mounted to a drill bit either by
press-fitting or otherwise locking the insert into a receptacle on
a steel-body drag bit, percussion bit or roller cone bit, or by
brazing the insert substrate (with or without cylindrical backing)
directly into a preformed pocket, socket or other receptacle on the
face of a bit body, as on a matrix-type bit.
[0055] An insert, as described in this invention, is preferably
fabricated by placing a preformed cemented carbide substrate into a
container or cartridge with a layer of diamond crystals or grains
loaded into the cartridge adjacent to one face of the substrate. A
number of such cartridges are then loaded into an ultra-high
pressure press simultaneously. Next, the substrates and adjacent
diamond crystal layers are subjected to ultra-high temperature and
ultra-high pressure conditions. Such ultra-high pressure and
ultra-high temperature conditions cause the metal binder from the
substrate body to become liquid and to sweep from the region behind
the substrate face next to the diamond layer, through the diamond
grains and then to act as a reactive liquid phase to promote a
sintering of the diamond grains thereby forming the polycrystalline
diamond structure. As a result, the diamond grains become mutually
bonded together forming a diamond mass over the substrate face.
This diamond mass is also bonded to the substrate face.
Alternatively, the diamond layer may be formed as above, but
separately from the substrate, and may be subsequently bonded to
the substrate material by brazing with a tungsten or titanium-base
braze. Yet another alternative method is to deposit the diamond
layer on the substrate by chemical vapor deposition (CVD)
processing. The metal binder may remain in the diamond layer within
the pores existing between the diamond grains or may be removed and
optionally replaced by another material, as known in the art, to
form a so-called thermally stable diamond. Where the binder is
removed by leaching a diamond table is formed with silicon, or
alternatively another material having a coefficient of thermal
expansion similar to that of diamond. Variations of this general
process exist in the art, but this detail is provided so that the
reader will understand the concept of sintering a diamond layer
onto a substrate on order to form a cutter or insert.
[0056] In a case of the present invention, the desired surface
shape of the diamond layer is achieved by utilizing preformed cans.
Alternatively, the surface shape can be formed by grinding or even
through the use of etching, EOM, EDG, etc.
[0057] Eight examples of the inventive insert design are now
described. Further modifications may be made without departing from
the essential nature of the invention and such modifications should
be considered to fall within the scope of this patent.
[0058] FIG. 3 depicts the top 301 and section 302 view of a single
preferred embodiment of the invention. It can be seen that inserts
of this invention are generally cylindrical in shape, with a
generally hemispherical diamond surface 306, the apex of which is
at the center axis 307 of the insert. This diamond insert is
composed of a layer of polycrystalline diamond 303 bonded to a
tungsten carbide substrate 304. The polycrystalline diamond layer
303 serves as the cutting surface. The interface region 305 is
shown where the polycrystalline diamond layer 303 is joined to the
substrate 304. In this embodiment of the invention the interface
region 305 is essentially flat. Alternatively, the interface region
can have an irregular geometry imposed on it.
[0059] FIG. 4 depicts the top 401 and section 402 view of a second
embodiment of the invention. Again, the insert is generally
cylindrical in shape, with a generally hemispherical diamond
surface 406. Alternatively, the apex of the hemisphere could be
offset from the center of the insert. This diamond insert is
composed of a layer of polycrystalline diamond 403 bonded to a
tungsten carbide substrate 404. The polycrystalline diamond layer
403 serves as the cutting surface. The interface region 405 is
shown where the polycrystalline diamond layer 403 is joined to the
substrate 404. In this embodiment of the invention the interface
region 405 is curved with the apex 407 of the curve at the center
axis 408 of the insert. Alternatively, the interface region 405 may
be positioned such that the diamond layer is relatively thinner or
relatively thicker.
[0060] FIG. 5 depicts the top 501 and the section 502 view of
another embodiment of the invention. Again, the insert is generally
cylindrical in shape, with a generally hemispherical diamond
surface 506. This diamond insert is composed of a layer of
polycrystalline diamond 503 bonded to a tungsten carbide substrate
504. The polycrystalline diamond layer 503 serves as the cutting
surface. The interface region 505 is shown as the region where the
polycrystalline diamond layer 503 is joined to the substrate 504.
In this embodiment of the invention the interface region 505
includes a trough 507 in the substrate 504 in which the diamond
layer 503 extends. This trough 507 intersects and runs
perpendicular to the center axis 508 of the insert. Alternatively,
the trough 507 can be revolved about the center axis 508 of the
insert.
[0061] FIG. 6 depicts the top 601 and the section 602 view of
another embodiment of the invention. Again, the insert is generally
cylindrical in shape, with a generally hemispherical diamond
surface 606. This diamond insert is composed of a layer of
polycrystalline diamond 603 bonded to a tungsten carbide substrate
604. The polycrystalline diamond layer 603 serves as the cutting
surface. The interface region 605 is shown as where the
polycrystalline diamond layer 603 is joined to the substrate 604.
In this embodiment of the invention, the interface region 605
includes a protrusion 607 of the substrate 604 into the
polycrystalline diamond 603 layer. This protrusion 607 intersects
and runs perpendicular to the center axis 608 of the insert.
Alternatively, the protrusion 607 can be revolved about the center
axis 608 of the insert.
[0062] FIG. 7 depicts the section 701 view of an alternative
embodiment of the invention. In this embodiment the insert has a
generally conic shaped polycrystalline diamond region 702 bonded to
a cylinder which is the tungsten carbide substrate 703. The
polycrystalline diamond region 702 serves as the cutting surface.
The interface region 704 is shown where the polycrystalline diamond
region 702 is joined to the substrate 703. In this embodiment of
the invention the interface region 704 is generally flat.
Alternatively, the interface region 704 may have irregularities
imposed upon it. The apex of the cone 705 is formed along the
center axis 706 of the insert.
[0063] FIG. 8 depicts the section 801 view of an alternative
embodiment of the invention. In this embodiment the insert has a
generally conic shaped polycrystalline diamond region 802 bonded to
a generally conic shaped tungsten carbide substrate region 803. The
polycrystalline diamond region 802 serves as the cutting surface.
The interface region 804 is shown where the polycrystalline diamond
region 802 is joined to the substrate 803. In this embodiment of
the invention, the interface region 804 is of a generally conical
shape. The apex of both the diamond region cone 805 and the
interface region cone 806 is formed along the center axis 807 of
the insert.
[0064] FIG. 9 depicts the section 901 view of an alternative
embodiment of the invention. In this embodiment, the insert also
has a generally conic shaped polycrystalline diamond region 902
bonded to a generally cylindrically shaped tungsten carbide
substrate region 903. The polycrystalline diamond region 902 serves
as the cutting surface. The interface region 904 is shown as the
area where the polycrystalline diamond region 902 is joined to the
substrate 903. In this embodiment of the invention, the interface
region 904 includes a trough 905 in the substrate 903 in which the
diamond region 902 extends. This trough 905 intersects and runs
perpendicular to the center axis 906 of the insert. Alternatively,
the trough 905 can be revolved about the center axis 906 of the
insert.
[0065] FIG. 10 depicts the section 1001 view of an alternative
embodiment of the invention. In this embodiment, the insert also
has a generally conic shaped polycrystalline diamond region 1002
bonded to a generally cylindrically shaped tungsten carbide
substrate region 1003. The polycrystalline diamond region 1002
serves as the cutting surface. The interface region 1004 is shown
where the polycrystalline diamond region 1002 is joined to the
substrate 1003. In this embodiment of the invention, the interface
region 1004 includes a protrusion 1005 of the substrate 1003 into
the polycrystalline diamond 1002 layer. This protrusion 1005
intersects and runs perpendicular to the center axis 1006 of the
insert. Alternatively, the protrusion 1005 can be revolved about
the center axis 1006 of the insert.
[0066] Alternative embodiments of the invention employing a
combination of one or more of the features of the foregoing inserts
should be considered within the scope of this invention.
[0067] The described embodiments are to be considered in all
respects only as illustrative of the current best mode of the
invention known to the inventor at the time of filing the patent
application, and not as restrictive. Although several of the
embodiments shown here include a trough or protrusion in the
interface region, interface region geometry is not intended to be
limited to a single trough or protrusion or to a particular
interface region shape. The scope of this invention is, therefore,
indicated by the appended claims rather than by the foregoing
description. All devices which come within the meaning and range of
equivalency of the claims are to be embraced as within the scope of
this patent.
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