U.S. patent application number 11/710091 was filed with the patent office on 2008-08-28 for earth-boring tools and cutter assemblies having a cutting element co-sintered with a cone structure, methods of using the same.
Invention is credited to Nicholas J. Lyons, Redd H. Smith, John H. Stevens.
Application Number | 20080202814 11/710091 |
Document ID | / |
Family ID | 39544969 |
Filed Date | 2008-08-28 |
United States Patent
Application |
20080202814 |
Kind Code |
A1 |
Lyons; Nicholas J. ; et
al. |
August 28, 2008 |
Earth-boring tools and cutter assemblies having a cutting element
co-sintered with a cone structure, methods of using the same
Abstract
Methods of forming cutter assemblies for use on earth-boring
tools include sintering a cone structure to fuse one or more
cutting elements thereto. In some embodiments, one or more green,
brown, or fully sintered cutting elements may be positioned on a
green or brown cone structure prior to sintering the cone structure
to a final density. Cutter assemblies may be formed by such
methods, and such cutter assemblies may be used in earth-boring
tools such as, for example, earth-boring rotary drill bits and hole
openers.
Inventors: |
Lyons; Nicholas J.;
(Houston, TX) ; Stevens; John H.; (Spring, TX)
; Smith; Redd H.; (The Woodlands, TX) |
Correspondence
Address: |
TRASK BRITT
P.O. BOX 2550
SALT LAKE CITY
UT
84110
US
|
Family ID: |
39544969 |
Appl. No.: |
11/710091 |
Filed: |
February 23, 2007 |
Current U.S.
Class: |
175/61 ; 175/263;
175/425 |
Current CPC
Class: |
E21B 10/50 20130101 |
Class at
Publication: |
175/61 ; 175/263;
175/425 |
International
Class: |
E21B 10/36 20060101
E21B010/36 |
Claims
1. A method of forming a cutter assembly for use on an earth-boring
tool, the method comprising: providing a less than fully sintered
cone structure comprising hard particles and a matrix material;
positioning at least one cutting element on the less than fully
sintered cone structure; and sintering the cone structure to a
final density to fuse the at least one cutting element to the cone
structure.
2. The method of claim 1, wherein providing a less than fully
sintered cone structure comprises providing a green cone
structure.
3. The method of claim 2, wherein providing a green cone structure
comprises: mixing the hard particles with particles comprising the
matrix material to form a powder mixture; and pressing the powder
mixture to form the green cone structure.
4. The method of claim 3, further comprising: selecting the hard
particles from the group consisting of diamond, boron carbide,
boron nitride, aluminum nitride, and carbides or borides of the
group consisting of W, Ti, Mo, Nb, V, Hf, Ta, Cr, Zr, Al, and Si;
and selecting the matrix material from the group consisting of
cobalt-based alloys, iron-based alloys, nickel-based alloys, cobalt
and nickel-based alloys, iron and nickel-based alloys, iron and
cobalt-based alloys, aluminum-based alloys, copper-based alloys,
magnesium-based alloys, and titanium-based alloys.
5. The method of claim 2, further comprising machining at least one
aperture in the green cone structure, and wherein positioning at
least one cutting element on the less than fully sintered cone
structure comprises inserting the at least one cutting element into
the at least one aperture of the green cone structure.
6. The method of claim 5, further comprising providing an average
clearance of between about 0.001 inch and about 0.025 inch between
exterior surfaces of the at least one cutting element and the
surfaces of the green cone structure within the at least one
aperture.
7. The method of claim 2, further comprising machining at least one
protrusion on the green cone structure, and wherein positioning at
least one cutting element on the less than fully sintered cone
structure comprises placing the at least one cutting element onto
the at least one protrusion of the green cone structure.
8. The method of claim 2, wherein positioning at least one cutting
element on the less than fully sintered cone structure comprises
positioning at least one green cutting element on the green cone
structure, and wherein sintering the cone structure comprises
sintering the green cone structure with the green cutting element
thereon to a final density.
9. The method of claim 2, wherein positioning at least one cutting
element on the less than fully sintered cone structure comprises
positioning at least one brown cutting element on the green cone
structure, and wherein sintering the cone structure comprises
sintering the green cone structure with the brown cutting element
thereon to a final density.
10. The method of claim 1, wherein providing a less than fully
sintered cone structure comprises providing a brown cone
structure.
11. The method of claim 10, wherein providing a brown cone
structure comprises: mixing the hard particles with particles
comprising the matrix material to form a powder mixture; pressing
the powder mixture to form a green cone structure; and partially
sintering the green cone structure to form the brown cone
structure.
12. The method of claim 11, further comprising: selecting the hard
particles from the group consisting of diamond, boron carbide,
boron nitride, aluminum nitride, and carbides or borides of the
group consisting of W, Ti, Mo, Nb, V, Hf, Ta, Cr, Zr, Al, and Si;
and selecting the matrix material from the group consisting of
cobalt-based alloys, iron-based alloys, nickel-based alloys, cobalt
and nickel-based alloys, iron and nickel-based alloys, iron and
cobalt-based alloys, aluminum-based alloys, copper-based alloys,
magnesium-based alloys, and titanium-based alloys.
13. The method of claim 10, further comprising machining at least
one aperture in the brown cone structure, and wherein positioning
at least one cutting element on the less than fully sintered cone
structure comprises inserting the at least one cutting element into
the at least one aperture of the brown cone structure.
14. The method of claim 10, further comprising machining at least
one protrusion on the brown cone structure, and wherein positioning
at least one cutting element on the less than fully sintered cone
structure comprises placing the at least one cutting element onto
the at least one protrusion of the brown cone structure.
15. The method of claim 10, wherein positioning at least one
cutting element on the less than fully sintered cone structure
comprises positioning at least one green cutting element on the
brown cone structure, and wherein sintering the cone structure
comprises sintering the brown cone structure with the green cutting
element thereon to a final density.
16. The method of claim 10, wherein positioning at least one
cutting element on the less than fully sintered cone structure
comprises positioning at least one brown cutting element on the
brown cone structure, and wherein sintering the cone structure
comprises sintering the brown cone structure with the brown cutting
element thereon to a final density.
17. The method of claim 1, wherein positioning at least one cutting
element on the less than fully sintered cone structure comprises
positioning at least one cutting element comprising hard particles
and a matrix material on the less than fully sintered cone
structure.
18. The method of claim 17, further comprising: selecting the hard
particles of the at least one cutting element from the group
consisting of diamond, boron carbide, boron nitride, aluminum
nitride, and carbides or borides of the group consisting of W, Ti,
Mo, Nb, V, Hf, Ta, Cr, Zr, Al, and Si; and selecting the matrix
material of the at least one cutting element from the group
consisting of cobalt-based alloys, iron-based alloys, nickel-based
alloys, cobalt and nickel-based alloys, iron and nickel-based
alloys, iron and cobalt-based alloys, aluminum-based alloys,
copper-based alloys, magnesium-based alloys, and titanium-based
alloys.
19. The method of claim 1, wherein positioning at least one cutting
element on the less than fully sintered cone structure further
comprises causing the at least one cutting element to have a
varying material composition between a first region proximate an
interface between the at least one cutting element and the less
than fully sintered cone and a second region proximate a
formation-engaging surface of the at least one cutting element.
20. The method of claim 19, wherein causing the at least one
cutting element to have a varying material composition comprises:
causing the first region to have a first material composition
selected to enhance bonding between the at least one cutting
element and the less than fully sintered cone; and causing the
second region to have a second material composition selected to
enhance at least one material property of the at least one cutting
element.
21. The method of claim 1, further comprising: positioning at least
one bearing structure on the less than fully sintered cone
structure; and fusing the bearing structure to the less than fully
sintered cone structure while sintering the cone structure to a
final density.
22. The method of claim 1, further comprising mounting the cone
structure on a bearing pin of an earth-boring tool.
23. An earth-boring tool comprising: a bearing pin; and a cutter
assembly rotatably mounted on the bearing pin, the cutter assembly
comprising: a cone comprising a particle-matrix composite material
having a first material composition; and at least one cutting
element co-sintered and integral with the cone, the at least one
cutting element comprising a particle-matrix composite material
having a second material composition differing from the first
material composition.
24. The earth-boring tool of claim 23, wherein the particle-matrix
composite material of the cone comprises a plurality of hard
particles dispersed throughout a matrix material, the hard
particles comprising a material selected from diamond, boron
carbide, boron nitride, aluminum nitride, and carbides or borides
of the group consisting of W, Ti, Mo, Nb, V, Hf, Ta, Cr, Zr, Al,
and Si, the matrix material selected from the group consisting of
cobalt-based alloys, iron-based alloys, nickel-based alloys, cobalt
and nickel-based alloys, iron and nickel-based alloys, iron and
cobalt-based alloys, aluminum-based alloys, copper-based alloys,
magnesium-based alloys, and titanium-based alloys.
25. The earth-boring tool of claim 24, wherein the particle-matrix
composite material of the co-sintered cutting element comprises a
plurality of hard particles dispersed throughout a matrix material,
the hard particles comprising a material selected from diamond,
boron carbide, boron nitride, aluminum nitride, and carbides or
borides of the group consisting of W, Ti, Mo, Nb, V, Hf, Ta, Cr,
Zr, Al, and Si, the matrix material selected from the group
consisting of cobalt-based alloys, iron-based alloys, nickel-based
alloys, cobalt and nickel-based alloys, iron and nickel-based
alloys, iron and cobalt-based alloys, aluminum-based alloys,
copper-based alloys, magnesium-based alloys, and titanium-based
alloys.
26. The earth-boring tool of claim 23, further comprising at least
one bearing structure co-sintered and integral with the cone.
27. The earth-boring tool of claim 23, wherein the at least one
bearing structure comprises a particle-matrix composite
material.
28. The earth-boring tool of claim 23, wherein the at least one
cutting element comprises a cutting insert.
29. The earth-boring tool of claim 23, wherein the at least one
cutting element comprises at least a portion of a cutting tooth
structure.
30. The earth-boring tool of claim 23, wherein the at least one
cutting element has a varying material composition between a first
region proximate an interface between the at least one cutting
element and the cone and a second region proximate a
formation-engaging surface of the at least one cutting element.
31. A cutter assembly for use on an earth-boring tool, the cutter
assembly comprising at least one cutting element co-sintered and
integral with a cone structure, the cone structure comprising a
particle-matrix composite material having a first material
composition, the at least one cutting element comprising a
particle-matrix composite material having a second material
composition differing from the first material composition.
32. The cutter assembly of claim 31, wherein the particle-matrix
composite material of the cone structure comprises a plurality of
hard particles dispersed throughout a matrix material, the hard
particles comprising a material selected from diamond, boron
carbide, boron nitride, aluminum nitride, and carbides or borides
of the group consisting of W,. Ti, Mo, Nb, V, Hf, Ta, Cr, Zr, Al,
and Si, the matrix material selected from the group consisting of
cobalt-based alloys, iron-based alloys, nickel-based alloys, cobalt
and nickel-based alloys, iron and nickel-based alloys, iron and
cobalt-based alloys, aluminum-based alloys, copper-based alloys,
magnesium-based alloys, and titanium-based alloys.
33. The cutter assembly of claim 32, wherein the particle-matrix
composite material of the at least one cutting element comprises a
plurality of hard particles dispersed throughout a matrix material,
the hard particles comprising a material selected from diamond,
boron carbide, boron nitride, aluminum nitride, and carbides or
borides of the group consisting of W, Ti, Mo, Nb, V, Hf, Ta, Cr,
Zr, Al, and Si, the matrix material selected from the group
consisting of cobalt-based alloys, iron-based alloys, nickel-based
alloys, cobalt and nickel-based alloys, iron and nickel-based
alloys, iron and cobalt-based alloys, aluminum-based alloys,
copper-based alloys, magnesium-based alloys, and titanium-based
alloys.
34. The cutter assembly of claim 31, further comprising at least
one bearing structure co-sintered and integral with the cone
structure.
35. The cutter assembly of claim 34, wherein the at least one
bearing structure comprises a particle-matrix composite
material.
36. The cutter assembly of claim 31, wherein the at least one
cutting element comprises a cutting insert.
37. The cutter assembly of claim 31, wherein the at least one
cutting element comprises at least a portion of a cutting tooth
structure.
38. The cutter assembly of claim 31, wherein the second material
composition of the at least one cutting element varies between a
first region proximate an interface between the at least one
cutting element and the cone structure and a second region
proximate a formation-engaging surface of the at least one cutting
element.
Description
FIELD OF THE INVENTION
[0001] The present invention generally relates to earth-boring
tools having one or more rotatable cones. More particularly,
embodiments of the present invention relate to methods of forming
cutter assemblies having a cone comprising a particle-matrix
composite material for use in such earth-boring tools, to cutter
assemblies formed by such methods, and to earth-boring tools that
include such cutter assemblies.
BACKGROUND OF THE INVENTION
[0002] Earth-boring tools, including rotary drill bits, are
commonly used for drilling bore holes or wells in earth formations.
One type of rotary drill bit is the roller cone bit (often referred
to as a "rock" bit), which typically includes a plurality of
conical cutting elements (often referred to as "cones" or
"cutters") secured to legs dependent from the bit body. For
example, the bit body of a roller cone bit may have three depending
legs each having a bearing pin. A rotatable cone may be mounted on
each of the bearing pins. The bit body also may include a threaded
upper end for connecting the drill bit to a drill string.
[0003] In some roller cone bits, the rotatable cones may include
inserts or compacts that are formed from a particle-matrix
composite material and secured within mating holes formed in an
exterior surface of the cone body. The inserts protrude from the
exterior surface of the cone body, such that the inserts engage and
disintegrate an earth formation as the rotatable cone rolls across
the surface of the earth formation in a well bore during a drilling
operation. Such inserts may be formed by compacting a powder
mixture in a die. The powder mixture may include a plurality of
hard particles (e.g., tungsten carbide) and a plurality of
particles comprising a matrix material (e.g., a metal or metal
alloy material). The compacted powder mixture then may be sintered
to form an insert. In some roller cone bits, the body of the
rotatable cones (or at least the outer shells of the rotatable
cones) may be formed of steel. The particle-matrix composite
material from which the inserts are formed may be relatively more
resistant to abrasive wear than the body (or at least the outer
shell) of the rotatable cones. During drilling operations, it is
possible that a body of a rotatable cone may wear to the extent
that one or more inserts may fall out from the hole in which it was
secured due to excessive wear of the region of the cone body
surrounding the hole.
[0004] In additional roller cone bits, the rotatable cones may
include teeth that are milled or machined directly into an exterior
surface of the cone body. After machining the teeth, hardfacing
material may be applied to the teeth, gage, and other
formation-engaging surfaces of the cone body in an effort to reduce
wear of such formation-engaging surfaces. The hardfacing material
typically includes a particle-matrix composite material. For
example, the hardfacing material may include tungsten carbide
granules or pellets embedded within a metal or metal alloy.
[0005] Various techniques known in the art may be used to apply a
particle-matrix composite hardfacing material to a surface of a
work piece, such as an earth-boring tool. For example, a hollow
cylindrical tube may be formed from a matrix material, and the tube
may be filled with hard particles (e.g., tungsten carbide). At
least one end of the tube may be sealed and positioned near the
surface of the work piece. The sealed end of the tube then may be
melted using an arc or a torch. As the tube melts, the tungsten
carbide particles within the hollow, cylindrical tube mix with the
molten matrix material as it is deposited onto the work piece. In
additional methods, a substantially solid rod comprising the
particle-matrix composite hardfacing material may be used in place
of a hollow tube comprising matrix material that is filled with
hard particles.
[0006] Additional arc welding techniques also may be used to apply
a hard-facing material to the exterior surface of the work piece.
For example, a plasma-transferred arc maybe established between an
electrode and a region on the exterior surface of the work piece on
which it is desired to apply a hard-facing material. A powder
mixture including both hard particles and particles comprising
matrix material then may be directed through or proximate the
plasma transferred arc onto the region of the exterior surface of
the work piece. The heat generated by the arc melts at least the
particles of matrix material to form a weld pool on the surface of
the work piece, which subsequently solidifies to form the
particle-matrix composite hardfacing material.
[0007] Hardfacing applications may be relatively labor intensive,
and hardfacing thickness and uniformity of coverage may be
difficult to control in a repeatable manner. Furthermore,
application of hardfacing material to the teeth of a rotatable cone
may reduce the sharpness of the cutting edges of the teeth. Some
grinding of the hardfacing to desired shapes may be performed. U.S.
Pat. No. 6,766,870, the entire disclosure of which is incorporated
herein in its entirety by this reference, discloses a method of
shaping hardfaced teeth through a secondary machining operation.
However, sharpening the hardfaced teeth by grinding adds another
step and substantial labor and machining cost in a process for
manufacturing a roller cone bit.
BRIEF SUMMARY OF THE INVENTION
[0008] In some embodiments, the present invention includes methods
of forming cutter assemblies for use on earth-boring tools. The
methods include sintering a less than fully sintered cone structure
to a desired final density to fuse at least one cutting element,
also termed inserts herein, to the cone structure. The less than
fully sintered cone structure may comprise hard particles and a
matrix material.
[0009] In additional embodiments, the present invention includes
cutter assemblies for use on an earth-boring tool having one or
more cutting elements co-sintered and integral with a cone
structure. The cone structure and the cutting elements each may
comprise a particle-matrix composite material. The material
composition of cone structure may differ from the material
composition of at least one of the cutting elements.
[0010] In yet further embodiments, the present invention includes
earth-boring tools having at least one such cutter assembly
rotatably mounted on a bearing pin.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0011] While the specification concludes with claims particularly
pointing out and distinctly claiming that which is regarded as the
present invention, the advantages of this invention may be more
readily ascertained from the following description of the invention
when read in conjuction with the accompanying drawings in
which:
[0012] FIG. 1 is a side elevational view of an earth-boring drill
bit according to an embodiment of the present invention;
[0013] FIG. 2 is a partial sectional view of one embodiment of a
rotatable cutter assembly, including a cone, of the present
invention and that may be used with the earth-boring drill bit
shown in FIG. 1;
[0014] FIG. 3 is a schematic view illustrating one method that may
be used to form a cone of a rotatable cutter assembly according to
an embodiment of the present invention;
[0015] FIG. 4 is a schematic view illustrating another method that
may be used to form a cone of a rotatable cutter assembly according
to another embodiment of the present invention;
[0016] FIG. 5A-5C illustrate one embodiment of a method that may be
used to form a rotatable cutter assembly of the present invention,
such as the rotatable cutter assembly shown in FIG. 2;
[0017] FIGS. 6A-6C illustrate another embodiment of a method that
may be used to form a rotatable cutter assembly that embodies
teachings of the present invention, such as the rotatable cutter
assembly shown in FIG. 2;
[0018] FIG. 7 is a side elevational view of another embodiment of
an earth-boring drill bit of the present invention;
[0019] FIG. 8 is a partial sectional view illustrating another
embodiment of a rotatable cutter assembly, including a cone, of the
present invention and that may be used with an earth-boring drill
bit, such as the earth-boring drill bit shown in FIG. 7;
[0020] FIG. 9 is a partial cross-sectional view of one embodiment
of a tooth structure that may be used to provide a rotatable cutter
assembly of the present invention, such as the cutter assembly
shown in FIG. 8; and
[0021] FIG. 10 is a partial cross-sectional view of another
embodiment of a tooth structure that may be used to provide a
rotatable cutter assembly of the present invention, such as the
cutter assembly shown in FIG. 8.
DETAILED DESCRIPTION OF THE INVENTION
[0022] The illustrations presented herein are not meant to be
actual views of any particular material, apparatus, system, or
method, but are merely idealized representations which are employed
to describe the present invention. Additionally, elements common
between figures may retain the same numerical designation.
[0023] The term "green" as used herein means unsintered.
[0024] The term "green structure" as used herein means an
unsintered structure comprising a plurality of discrete particles
held together by a binder material.
[0025] The term "brown" as used herein means partially
sintered.
[0026] The term "brown structure" as used herein means a partially
sintered structure comprising a plurality of particles, at least
some of which have partially grown together to provide at least
partial bonding between adjacent particles. Brown structures may be
formed by partially sintering a green structure.
[0027] The term "sintering" as used herein means densification of a
particulate component involving removal of at least a portion of
the pores between the starting particles (accompanied by shrinkage)
combined with coalescence and bonding between adjacent
particles.
[0028] As used herein, the term "[metal]-based alloy" (where
[metal] is any metal) means commercially pure [metal] in addition
to metal alloys wherein the weight percentage of [metal] in the
alloy is greater than the weight percentage of any other component
of the alloy.
[0029] As used herein, the term "material composition" means the
chemical composition and microstructure of a material. In other
words, materials having the same chemical composition but a
different microstructure are considered to have different material
compositions.
[0030] As used herein, the term "tungsten carbide" means any
material composition that contains chemical compounds of tungsten
and carbon, such as, for example, WC, W.sub.2C, and combinations of
WC and W.sub.2C. Tungsten carbide includes, for example, cast
tungsten carbide, sintered tungsten carbide, and macrocrystalline
tungsten carbide.
[0031] The depth of well bores being drilled continues to increase
as the number of shallow depth hydrocarbon-bearing earth formations
continues to decrease. These increasing well bore depths are
pressing conventional drill bits to their limits in terms of
performance and durability. Several drill bits are often required
to drill a single well bore, and changing a drill bit on a drill
string can be expensive.
[0032] New particle-matrix composite materials are currently being
investigated in an effort to improve the performance and durability
of earth-boring rotary drill bits. By way of example and not
limitation, bit bodies for fixed-cutter type earth-boring rotary
drill bits that include such particle-matrix composite materials,
and methods for forming such bit bodies, are disclosed in pending
U.S. patent application Ser. No. 11/271,153, filed Nov. 10, 2005
and pending U.S. patent application Ser. No. 11/272,439, also filed
Nov. 10, 2005, the disclosure of each of which application is
incorporated herein in its entirety by this reference. In addition,
earth-boring rotary drill bits having rotatable cutter assemblies
that comprise a cone formed from such particle-matrix composite
materials, as well as methods for forming such cones, are disclosed
in pending U.S. patent application Ser. No. 11/487,890, filed Jul.
17, 2006, the disclosure of which is incorporated herein in its
entirety by this reference.
[0033] An earth-boring drill bit 10 according to an embodiment of
the present invention is shown in FIG. 1. The earth-boring drill
bit 10 includes a bit body 12 and a plurality of rotatable cutter
assemblies 14. The bit body 12 may include a plurality of
integrally formed bit legs 16, and threads 18 may be formed on the
upper end of the bit body 12 for connection to a drill string. The
bit body 12 may have nozzles 20 for discharging drilling fluid into
a borehole, which may be returned along with cuttings up to the
surface during a drilling operation. Each of the rotatable cutter
assemblies 14 include a cone 22 comprising a particle-matrix
composite material and a plurality of cutting elements, such as the
cutting inserts 24 shown. Each cone 22 may include a conical gage
surface 26. Additionally, each cone 22 may have a unique
configuration of cutting inserts 24 or cutting elements, such that
the cones 22 may rotate in close proximity to one another without
mechanical interference.
[0034] FIG. 2 is a cross-sectional view illustrating one of the
rotatable cutter assemblies 14 of the earth-boring drill bit 10
shown in FIG. 1. As shown, each bit leg 16 may include a bearing
pin 28. The cone 22 may be supported by the bearing pin 28, and the
cone 22 may be rotatable about the bearing pin 28. Each cone 22 may
have a central cavity 30 that may be cylindrical and may form a
journal bearing surface adjacent the bearing pin 28. The cavity 30
may have a flat thrust shoulder 32 for absorbing thrust imposed by
the drill string on the cone 22. As illustrated in this example,
the cone 22 may be retained on the bearing pin 28 by a plurality of
locking balls 34 located in mating grooves formed in the surfaces
of the cone cavity 30 and the bearing pin 28. Additionally, a seal
assembly 36 may seal the bearing spaces between the cone cavity 30
and the bearing pin 28. The seal assembly 36 may be a metal face
seal assembly, as shown, or may be a different type of seal
assembly, such as an elastomer seal assembly.
[0035] Lubricant may be supplied to the bearing spaces between the
cavity 30 and the bearing pin 28 by lubricant passages 38. The
lubricant passages 38 may lead to a reservoir that includes a
pressure compensator 40 (FIG. 1).
[0036] As previously mentioned, the cone 22 may comprise a sintered
particle-matrix composite material that comprises a plurality of
hard particles dispersed through a matrix material. In some
embodiments, the cone 22 may be predominantly comprised of the
particle matrix composite material. The hard particles may comprise
diamond or ceramic materials such as carbides, nitrides, oxides,
and borides (including boron carbide (B.sub.4C)). More
specifically, the hard particles may comprise carbides and borides
made from elements such as W, Ti, Mo, Nb, V, Hf, Ta, Cr, Zr, Al and
Si. By way of example and not limitation, materials that may be
used to form hard particles include tungsten carbide (WC,
W.sub.2C), titanium carbide (TiC), tantalum carbide (TaC), titanium
diboride (TiB.sub.2), chromium carbides, titanium nitride (TiN),
vanadium carbide (VC), aluminum oxide (Al.sub.2O.sub.3), aluminum
nitride (AlN), boron nitride (BN), and silicon carbide (SiC).
Furthermore, combinations of different hard particles may be used
to tailor the physical properties and characteristics of the
particle-matrix composite material. The hard particles may be
formed using techniques known to those of ordinary skill in the
art. Most suitable materials for hard particles are commercially
available and the formation of the remainder is within the ability
of one of ordinary skill in the art.
[0037] The matrix material may include, for example, cobalt-based,
iron-based, nickel-based, iron and nickel-based, cobalt and
nickel-based, iron and cobalt-based, aluminum-based, copper-based,
magnesium-based, and titanium-based alloys. The matrix material may
also be selected from commercially pure elements such as cobalt,
aluminum, copper, magnesium, titanium, iron, and nickel. By way of
example and not limitation, the matrix material may include carbon
steel, alloy steel, stainless steel, tool steel, nickel or cobalt
superalloy material, and low thermal expansion iron or nickel based
alloys such as INVAR.RTM.. As used herein, the term "superalloy"
refers to an iron, nickel, and cobalt based-alloys having at least
12% chromium by weight. Additional exemplary alloys that may be
used as matrix material include austenitic steels, nickel based
superalloys such as INCONEL.RTM. 625M or Rene 95, and INVAR.RTM.
type alloys having a coefficient of thermal expansion that more
closely matches that of the hard particles used in the particular
material. More closely matching the coefficient of thermal
expansion of matrix material with that of the hard particles offers
advantages such as reducing problems associated with residual
stresses and thermal fatigue. Another exemplary matrix material is
a Hadfield austenitic manganese steel (Fe with approximately 12% Mn
by weight and 1.1% C by weight).
[0038] In one embodiment of the present invention, the sintered
particle-matrix composite material may include a plurality of -400
ASTM (American Society for Testing and Materials) mesh tungsten
carbide particles. For example, the tungsten carbide particles may
be substantially composed of WC. As used herein, the phrase "-400
ASTM mesh particles" means particles that pass through an ASTM No.
400 mesh screen as defined in ASTM specification E11-04 entitled
Standard Specification for Wire Cloth and Sieves for Testing
Purposes. Such tungsten carbide particles may have a diameter of
less than about 38 microns. The matrix material may include a metal
alloy comprising about 50% cobalt by weight and about 50% nickel by
weight. The tungsten carbide particles may comprise between about
60% and about 95% by weight of the composite material, and the
matrix material may comprise between about 5% and about 40% by
weight of the composite material. More particularly, the tungsten
carbide particles may comprise between about 70% and about 80% by
weight of the composite material, and the matrix material may
comprise between about 20% and about 30% by weight of the composite
material.
[0039] In another embodiment of the present invention, the sintered
particle-matrix composite material may include a plurality of -635
ASTM mesh tungsten carbide particles. As used herein, the phrase
"-635 ASTM mesh particles" means particles that pass through an
ASTM No. 635 mesh screen as defined in ASTM specification E11-04
entitled Standard Specification for Wire Cloth and Sieves for
Testing Purposes. Such tungsten carbide particles may have a
diameter of less than about 20 microns. The matrix material may
include a cobalt-based metal alloy comprising substantially
commercially pure cobalt. For example, the matrix material may
include greater than about 98% cobalt by weight. The tungsten
carbide particles may comprise between about 60% and about 95% by
weight of the composite material, and the matrix material may
comprise between about 5% and about 40% by weight of the composite
material. After forming, the cone 22 may exhibit a hardness in a
range extending from about 75 to about 92 on the Rockwell A
hardness scale.
[0040] FIGS. 3, 4, and 5A-5C illustrate embodiments of a method
that may be used to form the cone 22 and the cutter assembly 14
shown in FIG. 2. In general, this method includes providing a
powder mixture, pressing the powder mixture to form a billet,
forming a green or brown cone structure from the billet, and
sintering the green or brown cone structure to a desired final
density.
[0041] FIG. 3 illustrates a method of pressing a powder mixture 42
to form a green billet that may be used to form the cone 22. As
illustrated in FIG. 3, the powder mixture 42 may be pressed with
substantially isostatic pressure within a mold or container 44. The
powder mixture 42 may include a plurality of the previously
described hard particles and a plurality of particles comprising a
matrix material, as also previously described herein. Optionally,
the powder mixture 42 may further include one or more additives
such as, for example, binders (e.g., organic materials such as, for
example, waxes) for providing structural strength to the pressed
powder component, plasticizers for making the binder more pliable,
and lubricants or compaction aids for reducing inter-particle
friction and otherwise providing lubrication during pressing.
[0042] The container 44 may include a fluid-tight deformable member
46. For example, the deformable member 46 may be a substantially
cylindrical bag comprising a deformable and impermeable polymeric
material, which may be an elastomer such as rubber, neoprene,
silicone, or polyurethane. The container 44 may further include a
sealing plate 48, which may be substantially rigid. The deformable
member 46 may be filled with a powder mixture 42 and optionally
vibrated to provide a uniform distribution of the powder mixture 42
within the deformable member 46. The sealing plate 48 may be
attached or bonded to the deform able member 46, which may provide
a fluid-tight seal therebetween.
[0043] The container 44, with the powder mixture 42 therein, may be
placed within a pressure chamber 50. A removable cover 52 may be
used to provide access to the interior of the pressure chamber 50.
A gas (such as, for example, air or nitrogen) or a fluid (such as,
for example, water or oil), which may be substantially
incompressible, is pumped into the pressure chamber 50 through a
port 54 at high pressures using a pump (not shown). The high
pressure of the fluid may cause the member 46 to deform, and the
fluid pressure may be transmitted substantially uniformly to the
powder mixture 42. The pressure within the pressure chamber 50
during isostatic pressing may be greater than about 35 megapascals
(about 5,000 pounds per square inch). More particularly, the
pressure within the pressure chamber 50 during isostatic pressing
may be greater than about 138 megapascals (20,000 pounds per square
inch).
[0044] In additional methods, a vacuum may be provided within the
flexible container 44 and a pressure greater than about 0.1
megapascals (about 15 pounds per square inch) may be applied to the
deformable member 46 of the container 44 (by, for example, the
atmosphere) and may compact the powder mixture 42. Isostatic
pressing of the powder mixture 42 may form a green billet, which
may be removed from the pressure chamber 50 and the container 44
after pressing for machining. In some embodiments, the resulting
billet may have a generally cylindrical configuration.
[0045] FIG. 4 illustrates an additional method of pressing a powder
mixture 56 to form a green billet that may be used to form the cone
22 shown in FIG. 2. The method illustrated in FIG. 4 comprises
forming a billet using a rigid die 58 having a cavity for receiving
the powder mixture 56. The powder mixture 56 may be the same as the
powder mixture 42 used in the method illustrated in FIG. 3. The
cavity of the die 58 may be generally conically-shaped, and may
form an overall conical billet. Alternatively, the cavity may be
cylindrical, and may form a cylindrical billet. A piston or ram 60
may sealingly engage the walls of the die 58. A force may act on
the piston 60 and may press the powder mixture 56 into a green
billet with a coherent shape suitable for machining.
[0046] The green billet, whether formed by the method illustrated
in FIG. 3 or FIG. 4, may be machined in the green state to form a
green cone structure 22A shown in FIG. 5A. In additional methods,
however, the green billet may be partially sintered to form a brown
billet, and the brown billet then may be machined to form a brown
cone structure (not shown). The brown billet may be less than fully
dense to facilitate machining thereof. Green or brown structures,
such as the green cone structure 22A, a brown cone structure, or a
green or brown billet, may be machined in substantially the same
manner as for steel cones known in the art. However, because
shrinkage may occur during subsequent sintering processes, the
dimensions of the green or brown structures may be over-sized to
accommodate for shrinkage.
[0047] FIG. 5A illustrates a green cone structure 22A that may be
used to form the cutter assembly 14 (FIGS. 1-2). As illustrated in
FIG. 5A, in some embodiments, the green cone structure 22A may have
an overall shape corresponding to the desired final shape of the
cone 22, and may include various features such as a central cavity
30 for providing a journal bearing surface adjacent a bearing pin
28 (FIG. 2) and apertures 62 for receiving cutting inserts 24
therein (FIG. 2).
[0048] Optionally, displacement members 64 may be inserted into the
apertures 62 for preserving a desired size, shape and orientation
of each of the apertures 62 during a subsequent sintering process.
The displacement members 64 may comprise dowels that are
dimensioned to the desired final dimensions of the aperture 62 in
the cone 22 to be formed for each insert 24. The displacement
members 64 may be formed of a material, such as a ceramic, that
will remain solid and stable at the sintering temperature.
Additionally, the displacement members 64 may be formed of a porous
and/or hollow material to facilitate their removal from the
resulting fully sintered cone 22 after the sintering process. The
apertures 62 may be larger in diameter than the displacement
members 64 before sintering, and may shrink during sintering to the
diameters of the displacement members 64.
[0049] In some embodiments, the green cone structure 22A shown in
FIG. 5A may be heated and sintered in a furnace to a desired final
density to form a fully sintered cone 22 shown in FIG. 5B. The
fully sintered cone 22 is shown in FIG. 5B after the displacement
members 64 (FIG. 5A) have been removed from the fully sintered cone
22.
[0050] In some embodiments, the furnace may comprise a vacuum
furnace for providing a vacuum therein during the sintering
process. In additional embodiments, the furnace may comprise a
pressure chamber for pressurizing the cone therein as it is
sintered. Furthermore, the furnace may be configured to provide a
controlled atmosphere. For example, the furnace may be configured
to provide an atmosphere that is substantially free of oxygen in
which the cone may be sintered.
[0051] As a non-limiting example, it may be desirable to provide a
cone 22 comprising a sintered tungsten carbide material. To form
such a cone, a green cone structure 22A may be formed that includes
a plurality of particles comprising tungsten carbide and a
plurality of particles comprising a cobalt-based matrix material,
the particles being bound together by an organic binder material.
In such methods, the green cone structure 22A may be sintered at a
temperature of between about five hundred degrees Celsius
(500.degree. C.) and about fifteen hundred degrees Celsius
(1500.degree. C.). The sintering temperature may differ between
particular particle-matrix composite material compositions.
[0052] During the sintering process, the green cone structure 22A
may undergo shrinkage and densification as it is sintered to a
final density to form the cone 22. After sintering, the cone 22 may
have the desired exterior configuration, which may include the
apertures.62, and the central cavity 30. Limited or no further
machining may be necessary for these surfaces. The cavity 30, or
other surfaces, may be machined after sintering. For example, the
bore surfaces of the cavity 30 may be ground and polished to
achieve a desired surface finish.
[0053] As shown in FIG. 5C, after the cone 22 has been formed and
the optional displacement members 64 removed, cutting inserts 24
may be secured within the apertures 62. The cutting inserts 24 may
have a size and shape selected to provide a tight and secure
press-fit between the cutting inserts 24 and the apertures 62. In
additional embodiments, the cutting inserts 24 may be bonded within
the apertures 62 using an adhesive. In yet other embodiments, the
cutting inserts 24 may be secured within the apertures 62 using a
soldering or brazing technique.
[0054] The central cavity 30 may be finish machined and the cone 22
may be mounted to the bearing pin 28 in a conventional manner (FIG.
2). The cutting inserts 24 may be formed separately from the cone
22 in a manner similar to that in which the cone 22 is formed.
Although the cutting inserts 24 may also be formed of a sintered
particle-matrix composite material, the composition of the
particle-matrix composite material of the cutting inserts 24 may
differ from the composition of the particle-matrix composite
material of the cone 22.
[0055] In additional methods, rather than forming a green or brown
billet comprising a sintered particle-matrix composite material and
machining the green or brown billet to form a green or brown cone
structure, a green billet may be sintered to a desired final
density to provide a fully sintered billet. Such a fully sintered
billet then may be machined to form the fully sintered cone 22
shown in FIG. 5B using traditional machining methods or ultrasonic
machining methods. As such a fully sintered billet may be
relatively difficult to machine, use of ultrasonic machining
methods may facilitate the machining process. For example,
ultrasonic machining methods may include applying a high frequency
vibratory motion to the machining tool, which may enhance removal
of material from the filly sintered billet.
[0056] FIGS. 6A-6C illustrate an additional embodiment of a method
that may be used to form a cutter assembly (such as the cutter
assembly 14 shown in FIG. 3) of the present invention. As discussed
in further detail below, the method generally includes providing a
less than fully sintered green or brown cone comprising a plurality
of apertures, inserting inserts into the apertures in the green or
brown cone, and sintering the resulting structure to a desired
final density to secure the inserts to the cone. In this manner,
the inserts may be co-sintered and integral with the cone. In some
embodiments, the inserts may comprise less than fully sintered
green or brown inserts, and the green or brown inserts may be
sintered to a desired final density simultaneously with the cone.
In other embodiments, the inserts may be fully sintered when they
are inserted into the corresponding apertures of the green or brown
cone.
[0057] Furthermore, the inserts may have a composition gradient
that varies from a region or regions proximate the interface
between the inserts and the cone and a region or regions proximate
the formation engaging surface or surfaces of the inserts. For
example, the regions of the inserts proximate the interface between
the inserts and the cone may have a material composition configured
to facilitate or enhance bonding between the inserts and the cone,
while the regions proximate the formation engaging surface or
surfaces of the inserts may have a material composition configured
to enhance one or more material properties or characteristics such
as, for example, hardness, toughness, durability, and wear
resistance. As one non-limiting example, the regions of the inserts
proximate the interface between the inserts and the cone may have a
first matrix material substantially similar to the matrix material
of the cone, while the regions proximate the formation engaging
surface or surfaces of the inserts may have a second matrix
material selected to enhance one or more of the hardness,
toughness, durability, and wear resistance of the inserts. In such
embodiments, the concentrations of the first matrix material and
the second matrix material in the inserts may vary either
continuously or in a stepwise manner between the regions proximate
the interface and the regions proximate the formation engaging
surface.
[0058] Referring to FIG. 6A, a green cone structure 22A may be
formed or otherwise provided as previously described in relation to
FIG. 5A. A plurality of green cutting inserts 24A may be provided.
Each of the green cutting inserts 24A may comprise a plurality of
hard particles and a plurality of particles comprising a matrix
material, and the particles may be held together by an organic
binder material. As previously discussed, the composition of the
green cutting inserts 24A may differ from the composition of the
green cone structure 22A. Furthermore, the green cutting inserts
24A may have a composition gradient that varies from a region or
regions proximate the interface between the inserts and the cone
and a region or regions proximate the formation engaging surface or
surfaces of the inserts, as previously mentioned.
[0059] In some methods, additional green elements or components
other than the green cutting inserts 24A also may be secured to the
green cone structure 22A prior to sintering. By way of example and
not limitation, one or more green bearing structures 68A that are
to define bearing surfaces of the cone may secured within the
central cavity 30 of the green cone structure 22A. Similar to the
green cutting inserts 24A, each of the green bearing structures 68A
may comprise a plurality of hard particles and a plurality of
particles comprising a matrix material, and the composition of the
green bearing structures 68A may differ from the composition of the
green cone structure 22A.
[0060] As illustrated in FIG. 6B, the green cutting inserts 24A may
be provided within the apertures 62 of the green cone structure
22A, and the green bearing structures 68A may be secured at a
selected location within the central cavity 30 of the green cone
structure 22A.
[0061] By way of example and not limitation, the green cutting
inserts 24A and the apertures 62 within the green cone structure
22A may be sized and shaped so as to provide an average clearance
therebetween of between about one-thousandth of an inch (0.001 in.)
and about twenty-five thousandths of an inch (0.025 in.). Such
clearances also may be provided between the green bearing
structures 68 and the green cone structure 22A.
[0062] After assembling the various green components to form a
structure similar to that shown in FIG. 6B, the structure may be
sintered to a desired final density to form the fully sintered
structure shown in FIG. 6C. During the sintering process the cone
22, including the apertures 62 or other features, the cutting
inserts 24 or other cutting elements, and the bearing structures 68
may undergo shrinkage and densification. Furthermore, the cutting
inserts 24 and the bearing structures 68 may become fused and
secured to the cone 22. In other words, after the sintering
process, cutting inserts 24 and bearing structures 68 may be
co-sintered and integral with the cone 22 to provide a
substantially unitary cutter assembly 14'.
[0063] After the cutter assembly 14' has been sintered to a desired
final density, various features of the cutter assembly 14' may be
machined and polished, as necessary or desired. For example,
bearing surfaces on the bearing structures 68 may be polished.
Polishing the bearing surfaces of the bearing structures 68 may
provide a relatively smoother surface finish and may reduce
friction at the interface between the bearing structures 68 and the
bearing pin 28 (FIG. 2). Furthermore, the sealing edge 72 of the
bearing structures 68 also may be machined and/or polished to
provide a shape and surface finish suitable for sealing against a
metal or elastomer seal, or for sealing against a sealing surface
located on the bit body 12 (FIG. 2).
[0064] The green cutting inserts 24A and the green bearing
structures 68A may be formed from particle-matrix composite
materials in much the same way as the green cone structure 22A. The
material composition of each of the green cutting inserts 24A,
green bearing structures 68A, and green cone structure 22A may be
separately and individually selected to exhibit physical and/or
chemical properties tailored to the operating conditions to be
experienced by each of the respective components. By way of example
and not limitation, the composition of the green cutting inserts
24A may be selected so as to form cutting inserts 24 comprising a
particle-matrix composite material that exhibits a different
hardness, wear resistance, and/or toughness different from that
exhibited by the particle-matrix composite material of the cone
22.
[0065] The cutting inserts 24 may be formed from a variety of
particle-matrix composite material compositions. The particular
composition of any particular insert 24 may be selected to exhibit
one or more physical and/or chemical properties tailored for a
particular earth formation to be drilled using the drill bit 10
(FIG. 1). Additionally, cutting inserts 24 having different
material compositions may be used on a single cone 22.
[0066] By way of example and not limitation, in some embodiments of
the present invention, the cutting inserts 24 may comprise a
particle-matrix composite material that includes a plurality of
hard particles that are harder than a plurality of hard particles
of the particle-matrix composite material of the cone 22. As
another non-limiting example, the concentration of the hard
particles in the particle-matrix composite material of the cutting
inserts 24 may be greater than a concentration of hard particles in
a particle-matrix composite material of the cone 22.
[0067] Although the cutter assembly 14' shown in FIG. 6C is
illustrated as comprising the cone 22, the cutting inserts 24, and
the bearing structures 68, it is contemplated that in additional
embodiments, the cutter assembly 14' may not be formed with
separate green bearing structures 68A, as described herein.
Furthermore, as described above, the cutter assembly 14' may be
formed by combining a green cone structure 22A, green cutting
inserts 24A, and green bearing structures 68A to form a green
cutter assembly structure, and subsequently sintering the green
cutter assembly to a desired final density. The present invention
is not so limited, however, and methods according to further
embodiments of the present invention may include assembling green
structures, brown structures fully sintered structures, or any
combination thereof, and then sintering or reheating sintered
components to the sintering temperature and causing the various
components to fuse together to form a unitary, integral cutter
assembly structure.
[0068] While the cutter assembly 14' previously described herein
has a cone 22 that includes insert-type cutting structures, cutter
assemblies having cones that include tooth-type cutting structures
also may embody teachings of the present invention, and embodiments
of methods of the present invention may be used to form cutter
assemblies having cones that include such tooth-type cutting
structures. For example, FIG. 7 illustrates another earth-boring
drill bit 74 according to an embodiment of the present invention
which comprises a plurality of cutter assemblies 80 each having a
cone 88 that includes cutting teeth 104.
[0069] As shown in FIG. 7, the earth-boring drill bit 74 has a body
76 that may have threads 78 formed on its upper end for connection
to a drill string. The bit body 76 may have three integrally formed
bit legs 82, each supporting a bearing pin 84 (Not shown). In some
embodiments, the bit body 76 and the bearing pins 84 may be formed
of a steel alloy in a conventional manner. Additionally, the bit
body 76 may have nozzles 86 for discharging drilling fluid into the
borehole, which may be returned along with cuttings up to the
surface during a drilling operation.
[0070] As shown in FIG. 7, each cone 88 may have a plurality of
rows of cutting teeth 104. The teeth 104 may vary in number, have a
variety of shapes, and the number of rows may vary. A conical gage
surface 106 may surround the back face 102 of each cone 88 and
define the outer diameter of the bit 74. As discussed in further
detail below, one portion of each tooth 104 may be integrally
formed with the body of each cone 88, and another portion of each
tooth 104 may be formed using a separate green or brown structure
that is fused to the cone 88 during a sintering process.
[0071] FIG. 8 is an enlarged partial cross-sectional view
illustrating a portion of one of the cutter assemblies 80 mounted
on a bearing pin 84, and shows each of the teeth 104 rotated about
the cone 88 into the plane of the figure so as to illustrate the
so-called "cutting profile" defined by the cutting surfaces of all
the teeth 104 on the cone 88. As shown in FIG. 8, each bearing pin
84 of the drill bit 74 may support one of the cutter assemblies 80.
Each cone 88 of the cutter assemblies 80 may have a central cavity
90 that provides a journal bearing surface adjacent the bearing pin
84. The cone 88 may have a flat thrust shoulder 92 and may have a
lock groove 94 formed within the central cavity 90. In such a
configuration, a snap ring 96 may be located in the lock groove 94
and a mating groove may be formed on the bearing pin 84 for locking
the cone 88 in position on the bearing pin 84. The cone 88 also may
have a seal groove 98 for receiving a seal 100. The seal groove 98
may be located adjacent a back face 102 of the cone 88. By way of
example and not limitation, the seal 100 may be an elastomeric
ring. In some embodiments, the back face 102 of the cone 88 may
comprise a substantially flat annular surface surrounding the
entrance to the central cavity 90.
[0072] Lubricant may be supplied to the spaces between the central
cavity 90 of the cone 88 and the bearing pin 84 by lubricant
passages 108. The lubricant passages 108 may lead to a reservoir
that includes a pressure compensator 110 (FIG. 7).
[0073] The cone 88 may comprise a particle-matrix composite
material as previously described in relation to the cone 22 shown
in FIG. 2. Similarly, the cone 88 may be formed using methods
substantially similar to those previously described in relation to
the cone 22 with reference to FIGS. 3 and 4. In general, the cone
88 may be formed by green or brown billet, machining the green or
brown billet to form a green or brown cone structure, and sintering
the green or brown cone structure to a desired final density.
[0074] FIG. 9 illustrates one embodiment of a method of the present
invention and that may be used to form the cutter assembly 80 shown
in FIGS. 7 and 8. As shown therein, in some methods that embody
teachings of the present invention, a green cone structure 88A may
be provided by machining a greet billet. The green cone structure
88A may include a plurality of tooth base structures 105A. A
protruding feature 116 may be provided on each of the tooth base
structures I 05A, and a green cap structure 112 may be provided on
each of the protruding features 116. The green cap structures 112
may be formed from the same materials and in substantially the same
manners previously described in relation to the green cutting
inserts 24A (FIGS. 6A-6B). In some embodiments, the green cap
structures 112 may be secured to the protruding features 116 using
an adhesive. The tooth base structures 105A together with the green
cap structures 112 thereon define a plurality of green teeth
structures 104A.
[0075] After assembling green caps structures 112 on the tooth base
structures 105A to form the green teeth structures 104A, the
resulting structure may be sintered to a desired final density to
form the fully sintered cutter assembly 80 as shown in FIGS. 7 and
8.
[0076] The material composition of the green cap structures 112 and
the green cone structure 88A may be separately and individually
selected to exhibit physical and/or chemical properties tailored to
the operating conditions to be experienced by each of the
respective components. By way of example and not limitation, the
composition of the green cap structures 112 may be selected so as
to form, upon sintering the green cap structures 112, a
particle-matrix composite material that exhibits a different
hardness, wear resistance, and/or toughness different from that
exhibited by the particle-matrix composite material of the cone 88
(FIGS. 7 and 8).
[0077] FIG. 10 illustrates another embodiment of a method of the
present invention and that may be used to form the cutter assembly
80 shown in FIGS. 7 and 8. The method is substantially similar to
that previously described in relation to FIG. 9. A green cone
structure 88B may be provided that is substantially similar to the
green cone structure 88A shown in FIG. 9. The green cone structure
88B, however, may include a plurality of tooth base structures
105B, each of which has an aperture 118 therein. In this
configuration, a green plug structure 114 may be provided within
each of the apertures 118. The green plug structures 114 may be
formed from the same materials and in substantially the same
manners previously described in relation to the green cutting
inserts 24A (FIGS. 6A-6B) and the green cap structures 112 (FIG.
9). In some embodiments, the green plug structures 114 may be
secured within the apertures 118 using an adhesive. The tooth base
structures 105B together with the green plug structures 114 may
define a plurality of green teeth structures 104B.
[0078] After assembling green plug structures 114 on the tooth base
structures 105B to form the green teeth structures 104B, the
resulting structure may be sintered to a desired final density to
form the fully sintered cutter assembly 80 as shown in FIGS. 7 and
8.
[0079] As described above, the cutter assembly 80 shown in FIGS. 7
and 8 may be formed by combining a green cone structure 88A, 88B
with green cap structures 112 and/or green plug structures 114 to
form a green cutter assembly, and subsequently sintering the green
cutter assembly to a desired final density. The present invention
is not so limited, however, and other embodiments of methods of the
present invention may include assembling green structures, brown
structures, fully sintered structures, or any combination thereof,
and then sintering or reheating sintered components to the
sintering temperature and causing the various components to fuse
together to form a unitary, integral cutter assembly structure. By
way of example and not limitation, the green cone structure 88A
shown in FIG. 9 may be partially sintered to form a brown cone
structure (not shown), and the green cap structures 112 may be
assembled with the brown cone structure. The resulting structure
then may be sintered to a final density to fuse the cap structures
to the cone structure and form the teeth 104 (FIG. 7). As another
non-limiting example, the green plug structures 114 shown in FIG.
10 may be partially sintered to form brown plug structures (not
shown), and the brown plug structures may be assembled with the
green cone structure 88B. The resulting structure then may be
sintered to a final density to fuse the plug structures to the cone
structure and form the teeth 104 (FIG. 7).
[0080] While teachings of the present invention are described
herein in relation to embodiments of tri-cone rotary drill bits,
other types of earth-boring drilling tools such as, for example
hole openers, rotary drill bits, raise bores, fixed/rotary cutter
hybrid drill bits, cylindrical cutters, mining cutters, and other
such structures known in the art may embody the present invention
and may be formed by methods that embody the present invention.
Furthermore, while the present invention has been described herein
with respect to certain preferred embodiments, those of ordinary
skill in the art will recognize and appreciate that it is not so
limited. Rather, many additions, deletions and modifications to the
described and illustrated embodiments may be made without departing
from the scope of the invention as hereinafter claimed. In
addition, features from one embodiment may be combined with
features of another embodiment while still being encompassed within
the scope of the invention as contemplated by the inventors.
* * * * *