U.S. patent application number 09/754435 was filed with the patent office on 2002-07-04 for fracture resistant domed insert.
Invention is credited to Fox, Joe, Hall, David R..
Application Number | 20020084112 09/754435 |
Document ID | / |
Family ID | 25034785 |
Filed Date | 2002-07-04 |
United States Patent
Application |
20020084112 |
Kind Code |
A1 |
Hall, David R. ; et
al. |
July 4, 2002 |
Fracture resistant domed insert
Abstract
A cutting element for earth-boring drill bits comprising a
generally domed cutting surface comprising a superabrasive
material, formed by a high-pressure high-temperature sintering
method known in the art, integrally bonded to a cylindrical
substrate having a truncated conical interfacial surface,
consisting of a top surface and a circumferential shoulder joined
by tapered sidewalls, and the base of the substrate being adapted
for insertion into an earth-boring tool. The top surface of the
substrate may form a circle, a square, or a polygon, and the
sidewalls may be smooth or form one or more polygons.
Inventors: |
Hall, David R.; (Provo,
UT) ; Fox, Joe; (Provo, UT) |
Correspondence
Address: |
David R. Hall
2185 S Larsen Parkway
Provo
UT
84606
US
|
Family ID: |
25034785 |
Appl. No.: |
09/754435 |
Filed: |
January 4, 2001 |
Current U.S.
Class: |
175/426 ;
175/420.1; 175/432 |
Current CPC
Class: |
E21B 10/5735 20130101;
E21B 10/5676 20130101; E21B 10/5673 20130101 |
Class at
Publication: |
175/426 ;
175/420.1; 175/432 |
International
Class: |
E21B 010/46 |
Claims
What is claimed:
1. A cutting element for earth-boring drill bits, comprising: a
generally domed cutting surface comprising a superabrasive
material, formed by a high-pressure high-temperature sintering
method known in the art, integrally bonded to a cylindrical
substrate having a generally truncated conical interfacial surface,
consisting of a top surface and a circumferential shoulder joined
by tapered side walls, and the base of the substrate being adapted
for insertion into an earth-boring tool.
2. The cutting element of claim 1, wherein the surfaces of the
generally domed cutting table comprise polygonal shaped
surfaces.
3. The cutting element of claim 1, wherein the generally domed
cutting table has sufficient thickness to withstand compressive
drilling of subterranean formations.
4. The cutting element of claim 1, wherein the substrate is
composed of a fracture tough material selected from the group
consisting of cemented metal carbide.
5. The cutting element of claim 1, wherein the truncated
interfacial surface comprises a top surface forming a circle, a
square, a polygon, or a combination thereof.
6. The cutting element of claim 1, wherein the tapered walls of the
interfacial are surface smooth.
7. The cutting element of claim 1, wherein the tapered walls of the
interfacial surface form one or more polygons.
8. The cutting element of claim 1, wherein the tapered walls of the
interfacial surface form a truncated pyramid.
9. The cutting element of claim 1, wherein the tapered sidewalls
join the circumferential shoulder at an oblique angle.
10. The cutting element of claim 1, wherein the tapered sidewalls
join the shoulder and top along a filleted surface.
Description
RELATED APPLICATIONS
[0001] None.
BACKGROUND OF THE INVENTION
[0002] This invention relates to cutting inserts for use in
drilling subterranean formations such as oil, gas, and geothermal
wells. More particularly, this invention relates to a cutting
insert that is comprised of a tough, hard metal substrate featuring
a truncated conical interfacial surface. The cutting insert has one
or more layers of a superabrasive material are bonded under
high-pressure and high-temperature to the interfacial surface in
such a manner so as to form a generally domed cutting table.
Inserts of the present invention demonstrate fracture toughness
capable of withstanding the dynamic loads associated with drilling
a variety of subterranean formations.
[0003] Cutting elements coated with superabrasive materials such as
polycrystalline diamond or cubic boron nitride are used widely in
the drilling industry for drilling deep oil, gas, and geothermal
wells. Superabrasive cutting elements have been used on most styles
of drill bits that are used for subterranean drilling. The roller
cone bit is an example of a drill bit that has benefited from the
presence of at least some superabrasive cutting elements primarily
located in the gage and heel rows of the bit. A roller cone bit
usually has two or three cones that are rotationally affixed to the
bit body by means of sealed bearings. As the bit body is rotated
under the load of the drill string, the individual cones rotate
independently of each other. The cutting elements arrayed about the
cone bodies inflict a compressive stress on the formation being
drilled causing it to fail. The crushed rock is flushed away from
the bit and carried to the surface by the circulating drilling
fluid, or mud, and new rock is exposed to the cutting elements of
the bit.
[0004] Because superabrasive materials have high compressive
strengths, they are an ideal material for use in deep well
drilling. However, such materials are susceptible to stress
fractures that result in spalling, fracturing, and delamination of
the superabrasive cutting table. Stress on the cutting table of the
insert comes from both within the insert and from the formation
being drilled. Stresses on the drill bit due to subterranean
conditions are largely controlled by the driller, but because of
the differences in rates of thermal expansion, elastic moduli, and
bulk compressibilities between the superabrasive and the substrate
to which it is bonded, enormous internal residual stresses are
present along the interfacial surfaces of the cutting element.
These stresses may lead to failure of the superabrasive coating
despite the skill of the operator.
[0005] Studies have shown that by modifying the shape of the
surface to which the superabrasive is bonded residual stresses may
be reduced and fracture toughness thereby increased. This patent
discloses a domed cutting insert having a modified interfacial
surface that yields a superabrasive coating having sufficient
fracture toughness to withstand the compressive stresses of
subterranean drilling.
SUMMARY OF THE INVENTION
[0006] The cutting element substrate of the present invention is
comprised of tough cemented metal carbides and has a cylindrical
base adapted for insertion into an earth-boring tool such as a
roller cone bits. The substrate of the cutting element of the
present invention has a truncated conical interfacial surface
opposite its base end. The truncated conical interfacial surface is
integrally bonded to a superabrasive material such as
polycrystalline diamond or cubic boron nitride at high pressure and
high temperature. The actual shape of the truncated conical surface
may be round, oval, or a predetermined polygonal shape. The tapered
sides of the truncated conical surface may also comprise flats
having a predetermined polygonal shape such as trapezoid or
rectangle. Additionally, the tapered sides of the conical surface
may comprise flutes. The truncated conical surface may even have
surface protrusions or posts to further reinforce the superabrasive
material to which it is bonded. Another variation includes a
peripheral lip on the edge of the truncated conical surface, which
also increases bonding strength. A circumferential shoulder is
formed as the truncated conical surface begins tapering from the
base of the cylindrical substrate. The use of a truncated conical
interfacial surface underlying the superabrasive generally domed
cutting table permits the use of a tough metal carbide substrate
and decreases point pressure during drilling. Instead of
high-pressure strains localized over a small area during drilling,
the compressive and shear type stresses induced from drilling is
spread out over the flat truncated conical surface thereby reducing
overall strain on the cutting insert.
[0007] Superabrasive material used as a cutting surface is well
known in prior art. The superabrasive material used in this
invention consists of natural diamond, polycrystalline diamond,
cubic boron nitrides, or any combinations thereof The generally
domed shape of the superabrasive material that forms the cutting
table of the insert behaves much like a continuous truss bridge
with self-supporting arches and an interconnected rigid framework.
The self-supporting truss like strength of the polycrystalline dome
increases the overall fracture strength of the polycrystalline
cutting surface. Working in concert with the generally domed
cutting table, which may comprise polygonal surfaces, the truncated
conical shape of the tough substrate reduces spalling, cracking,
fracture, and delamination of the cutting surface during
compressive drilling through a variety of subterranean formation,
including those having periodic discontinuities such as hard rock
stringers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a perspective view of a substrate depicting a
truncated conical interfacial surface with a supporting
circumferential shoulder.
[0009] FIG. 2 is an aerial view of the substrate in FIG. 1.
[0010] FIG. 3 is cross sectional side view of one half of the
substrate as taken through line 1-1 of FIG. 2.
[0011] FIG. 4 is an external side view of a cutting insert of the
present invention depicting a generally domed cutting table.
[0012] FIG. 5 is a cross sectional side view of one half of the
cutting element in FIG. 4 as taken through line 1-1 of FIG. 2 and
including the integrally bonded superabrasive cutting surface.
[0013] FIG. 6 is a perspective view of a substrate depicting a
truncated conical interfacial surface with a supporting
circumferential shoulder and tapered rectangular flats.
[0014] FIG. 7 is an aerial view of the substrate in FIG. 6.
[0015] FIG. 8 is a cross sectional side view of one half of the
substrate including the integrally bonded superabrasive cutting
surface as taken through line 2-2 of FIG. 7.
[0016] FIG. 9 is an aerial view of a substrate depicting a
truncated conical interfacial surface with a square top surface,
trapezoidal side flats, and a supporting circumferential
shoulder.
[0017] FIG. 10 is an aerial view of a substrate depicting a
truncated conical interfacial surface with an octagonal top
surface, generally rectangular side flats, and a supporting
circumferential shoulder.
[0018] FIG. 11 is frontal cross-section view of a cutting insert of
the present invention depicting polygonal surfaces of the cutting
table.
[0019] FIG. 12 is a side cross-section view of the cutting insert
of FIG. 11 depicting polygonal surfaces of the cutting table.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Cutting elements associated with the present invention used
in earth-boring tools typically consist of two main parts: a
substrate made of fracture tough material and a cutting surface, or
cutting table, composed of a superabrasive material such as
polycrystalline diamond or cubic boron nitride. The present
invention relates to the shape of the cutting element substrate and
the shape of the cutting surface, and how those shapes combine to
permit the use of a tough carbide substrate and to reduce point
stress concentrations during compressive use. A detailed
description and associated drawings are described below.
[0021] A substrate 12 composed of a fracture tough material is
illustrated in FIG. 1, as an embodiment of the present invention.
The substrate 12 may consist of any number of fracture tough
materials such as tungsten carbide, nickel, cobalt, nickel or
cobalt carbides, or any number of cemented carbide materials. The
substrate 12 includes a generally cylindrical base 11 for insertion
into an earth-boring tool, such as a drill bit. A truncated conical
interfacial surface 14 is formed at the opposite end of the
substrate for supporting a superabrasive cutting table. Truncated
conical interfacial surface 14 includes tapered sides 24 and a
truncated top surface 26. The present invention includes variations
in the shape of the truncated top surface 26 and the tapered sides
24 which will be illustrated in later drawings. A supporting
circumferential shoulder 22 is formed between the outer perimeter
of the substrate 12 and the inner base perimeter of the tapered
sides 24 of truncated conical interfacial surface 14. This
circumferential shoulder 22 connects the truncated conical
interfacial surface 14 with the cylindrical base 11. The
circumferential shoulder 22 may join the tapered side 24 at an
obtuse angle, or it may be formed substantially perpendicular to
the tapered sides 24 and generally parallel to the truncated top
surface 26. However, the shoulder formed does not need to be
strictly perpendicular as will be noted in later drawings of the
invention. The circumferential shoulder aids compaction of the
superabrasive matrix during pre-sintering assembly and lends
support to the superabrasive cutting surface during formation of
the cutting element during the high pressure, high temperature
process. The supporting circumferential shoulder 22 gives a sort of
base layer upon which the superabrasive matrix can obtain its
footing and buttress upward formation of the cutting surface. The
truncated top surface 26 and tapered sides 24 are substantially
flat and smooth. The perimeter of truncated top surface 26 may be
defined by predetermined polygonal shapes, as illustrated in the
drawings of this disclosure.
[0022] FIG. 2 is an aerial view of the substrate in FIG. 1. A
circle 36 defines the truncated conical surface perimeter of
truncated top surface 26. The tapered sides 24 slope upward and are
cropped at a desired height forming truncated top surface 26. The
circumferential shoulder 22 is formed from the substrate body 12
and is of sufficient width to support the superabrasive before and
during the sintering process of the domed superabrasive cutting
surface. The shoulder also gives support to the cutting table
during subterranean drilling, increasing the fracture toughness of
the cutting table.
[0023] FIG. 3 illustrates a cross sectional side view of the
substrate taken along the lines 1-1 in FIG. 2. FIG. 3 includes only
one half of the substrate, the other half being a mirror image of
the illustrated half. The cylindrical base 11 of substrate 12 is
adapted for insertion into an earth-boring tool as shown by the
chamfers on the edges. The truncated conical interfacial surface 14
includes truncated top surface 26 and tapered sides 24. The
transition from the tapered sides 24 to the truncated top surface
26 may be gradual or abrupt. FIG. 3 depicts a gradual transition
from the circumferential shoulder 22 to the tapered sides 24 to the
truncated top surface 26 while maintaining a definite slope upward
from the base to the plateau of the truncated conical interfacial
surface 14. A gradual transition is preferred because of its effect
on the stresses along the junction of the shoulder and the tapered
walls. The circumferential shoulder 22 in FIG. 3 is substantially
perpendicular to the tapered sides 24. This illustration shows a
filleted edge between the circumferential shoulder 22 and the
tapered sides 24. Still, the edges between the two surfaces could
be exactly perpendicular if desired and such a configuration is not
outside the scope of the invention. Gentle sloping is however, the
preferred variation.
[0024] FIG. 4 illustrates an embodiment of the invention that
combines the substrate with the generally domed cutting table.
Cutting element 10 comprises a fracture tough substrate 12 and a
superabrasive cutting surface. The superabrasive material employed
in the cutting surface is well known in the prior art and common in
the drilling industry. The superabrasive material is selected from
the group consisting of diamond, polycrystalline diamond, or cubic
boron nitride. These materials are integrally bonded to the
substrate 12 during a high pressure, high temperature sintering
process. The terms PCD, polycrystalline diamond, diamond powder
matrix, or superabrasive material will be used hereafter to refer
to such materials. The superabrasive cutting surface 20 has a
generally domed shape 27 formed over the truncated conical
interfacial surface 14. The domed shape of the cutting surface
combines with the interfacial surface of the substrate to give the
insert fracture toughness suitable for drilling a variety of
subterranean formations, including those where hard rock stringers
are encountered.
[0025] FIG. 5 is a cross sectional side view of FIG. 4 taken
through lines 1-1 of FIG. 2. The cutting element 10, as shown in
FIG. 5, is one half the cutting element in FIG. 4. Cutting element
10 includes a generally cylindrical substrate 12 composed of
fracture tough material with a base 11 adapted for insertion into
an earth-boring tool. Opposite the base end 11 of substrate 12 is a
truncated conical interfacial surface 14 consisting of a truncated
top surface 26 and tapered sides 24. Joining the truncated conical
interfacial surface 14 to the substrate 12 is a circumferential
shoulder 22 used to support the superabrasive cutting surface 20,
especially during its formation. A superabrasive cutting surface 20
is formed on top of the truncated conical interfacial surface 14.
The superabrasive cutting surface 20 is integrally bonded to the
truncated conical interfacial surface 14 of the substrate through
the high-pressure, high-temperature process. The substrate 12 is
placed into a generally domed loading container with diamond
powders and refractory metals creating a diamond matrix that is
placed over the substrate. When subjected to a high pressure, high
temperature process, the diamond powders contacting the truncated
top surface 26 and tapered sides 24 of the substrate 11 are pressed
to form a superabrasive cutting surface 20 that takes on the shape
of the loading container. The generally dome like shape 27 of
superabrasive material bonded to the substrate yields superior
compressive strength. Because of the thickness 25 of the cutting
surface 20, the superabrasive dome 27 permits the use of a fracture
tough carbide insert and acts like a self-supporting bridge or a
continuous truss bridge. The self-supporting truss like strength of
the superabrasive dome 27 increases overall fracture strength of
the cutting surface 20 and thus increases the lifetime of the
cutting element 10.
[0026] FIG. 6 illustrates alternative embodiment of the present
invention. The substrate 12 includes a cylindrical base 11 and
truncated conical interfacial surface 14. Unlike the cutting
element in FIG. 1, the tapered sides 24 of the truncated conical
interfacial surface 14 of FIG. 6 are rectangular flats 34. The use
of flat surfaces on the tapered sides of the substrate increases
the volume of superabrasive material used in the cutting element.
The higher volume of superabrasive material in the cutting table
increases the life of the cutting surface while the generally domed
configuration of the cutting table in combination with the
truncated conical interfacial surface provides a cutting element
having sufficient fracture toughness to withstand the dynamic loads
associated with oil and gas well drilling. A circle 36 defines the
top surface perimeter of the truncated top surface 26. A shoulder
22 is formed substantially perpendicular to the tapered sides 24 of
truncated conical interfacial surface 14. This drawing shows how
the shoulder need not be strictly perpendicular to the tapered
sidewalls of the truncated conical interfacial surface but is
generally parallel to the truncated top surface 26. The shoulder 18
lends support to the superabrasive cutting surface during formation
of the cutting element through a high pressure, high temperature
process. The shoulder 22 gives a sort of base layer upon which the
diamond powder matrix can obtain its feet. This type of shape
behaves much like a continuous truss bridge with self-supporting
arches and an interconnected rigid framework. The self-supporting
truss-like strength of the polycrystalline dome increases the
overall fracture strength of the polycrystalline cutting surface.
The generally domed cutting table, in concert with the truncated
conical interfacial surface of the substrate of the present
invention, enables the cutting element to withstand spalling,
cracking, fracture, and delamination of the cutting surface during
compressive drilling.
[0027] FIG. 7 illustrates a top view of substrate 12 in FIG. 6 with
truncated top 26 in circular shape 36. Forming the tapered sides 24
leading up to the truncated top 26 are rectangular flats 34. A
supporting circumferential shoulder 22 forms the outer top
perimeter of the substrate 12.
[0028] FIG. 8 depicts a cross sectional side view of FIG. 7 as
taken through lines 2-2 of FIG. 7. A cutting element 10 as shown in
FIG. 8 is one half of the element in FIG. 7. Cutting element 10
includes a generally cylindrical substrate 12 with base end 11
adapted for insertion into an earth-boring tool. Opposite the base
end 11 is a truncated conical interfacial surface 14, which
includes truncated top surface 26 and tapered sides 24. Connecting
the truncated conical interfacial surface with the substrate is a
circumferential shoulder 22. In this particular embodiment of the
invention, it is noted how the formation of the truncated top
surface, tapered sides, and circumferential shoulder differ from
the previous embodiment. This embodiment employs a series of
oblique angles to define the junction between the truncated top
surface to the tapered sides and the tapered sides to the
circumferential shoulder. Thus the transitions from the truncated
top to the tapered sides and from the tapered sides to the
circumferential shoulder are not substantially perpendicular. These
oblique transitions serve to relieve points of stress concentration
that might otherwise be present. Additionally, the corners forming
the intersection of the oblique angles are not filleted but abrupt
and clearly defined as opposed to the substrate in FIG. 3. The
truncated conical interfacial surface 14 is specifically fashioned
to bond with the cutting surface 20 during a high pressure, high
temperature sintering process. The cutting surface 20 is formed to
have a generally dome like shape 27 with a substantial thickness 25
on top of the truncated conical interfacial surface 14. This type
of shape behaves much like a continuous truss bridge with
self-supporting arches and an interconnected rigid framework. The
self-supporting truss like strength of the polycrystalline dome
increases the overall fracture strength of the polycrystalline
cutting surface.
[0029] FIGS. 9 and 10 illustrate other variations in the shape of
the truncated conical interfacial surface of the substrate.
However, the cross sectional side view as depicted in FIG. 8 is not
different for both substrates depicted in FIGS. 9 and 10 as well as
the general shape the base portion of the substrate. In fact, FIG.
8 depicts a cross sectional side view taken along lines 3-3 and 4-4
of FIGS. 9 and 10 respectively. Accordingly, only aerial views of
the various truncated conical interfacial surfaces of FIGS. 9 and
10 are illustrated. FIG. 9 depicts a truncated conical interfacial
surface that is roughly the shape of a truncated pyramid. The
truncated pyramid includes a truncated top surface 26 with a square
perimeter 46 and tapered sides 24 forming trapezoids 44. The
tapered sides formed are not strictly limited to definitional
trapezoids as the base side of the trapezoids shown forms an arc
whereas conventional trapezoids have two sides parallel to each
other. Either variety however can be formed depending on
manufacturer interests. Interconnecting the trapezoidal sides 44
and the outer perimeter of the substrate 12 is the circumferential
shoulder 22. As noted earlier, the flat surfaces along the tapered
walls of the interfacial surface serve to increase the volume of
superabrasive material present in the cutting element. The higher
volume of material not only serves to increase fracture toughness
of the cutting element, it also adds to the overall life of the
cutting table.
[0030] FIG. 10 illustrates another variation in the shape of the
truncated top 26 of the truncated conical interfacial surface of
the substrate 12. Truncated top 26 is an octagonal shape 56 formed
by tapered sides 24 in the shape of rectangular flats 54. Again,
interconnecting the trapezoidal sides 54 and the outer perimeter of
the substrate 12 is the circumferential shoulder 22.
Interconnecting the trapezoidal sides 44 and the outer perimeter of
the substrate 12 is the circumferential shoulder 22. Various shapes
in the truncated conical interfacial surface yield different
surface areas, which affect the bonding strength between the
substrate and the superabrasive cutting surface.
[0031] FIG. 11 illustrates a face-on cross-sectional view of yet
another version of the present invention wherein the cutting insert
10 comprises a tough carbide base portion 12 and a cutting table 27
comprising a superabrasive material 20 that is bonded to the
substrate in a high pressure high temperature sintering process.
FIG. 12 is a side view of the insert of FIG. 11. The substrate 12
presents a cylindrical shape while the interfacial surfaces,
consisting of the shoulder 22, the tapered sides 24, and top
surface 26, form a polygonal interfacial surface, such as an oval,
to which the superabrasive is bonded. The broad face of the cutting
table serves to increase the area of penetration of the cutting
insert and the increased surface area of the cutting table reduces
point stress concentration. The increased depth of the
superabrasive permits the use of a tough carbide substrate while
imparting truss-like strength to the cutting table. These elements
combine to produce a cutting insert suitable for penetrating
fracture resistant subterranean formations.
[0032] FIG. 13 illustrates a cross sectional view of another
version of a cutting insert 10 of the present invention wherein the
cutting table 27 is a truncated cone mounted onto a cylindrical
substrate 12. As in the former versions of the present invention,
the top of the substrate 20 may present a plane circle or a
polygon. The relatively sharp truncated conical cutting table 27
may be particularly useful in soft formations where an aggressive
cutting insert is acceptable.
[0033] Other possible variations of the invention not shown in the
drawings, but known in the art, are presented here. One variation
may be to provide tapered sides having reinforcing nodules
extending into the cutting surface. The purpose of such posts is to
further reinforce and strengthen the cutting surface, to promote
adhesion of the cutting table to the substrate, and to prevent
substantial cracking, spalling, and delamination during compressive
drilling.
[0034] Another variation to the truncated conical interfacial
surface is tapered sides having flutes. The flutes increase the
surface area of the truncated conical interfacial surface and
enhance adhesion strength of the cutting surface to the
substrate.
[0035] One advantage of the present invention is its unidirectional
behavior meaning that the cutting insert can rotate in any
direction and still perform productively. Some cutting inserts in
the prior art are directionally based and must be correctly
implanted in the rotating drill head to function properly. If a
mistake is made in the setting of such cutting elements in the
rotating drill head, boring efficiency is reduced and cutting
element failure imminent. With the present invention, no such
problems exist. The insert can be placed into the rotating drill
bit with ease and without undue concern for its orientation.
* * * * *