U.S. patent application number 12/871670 was filed with the patent office on 2011-04-28 for methods of forming earth boring rotary drill bits including bit bodies comprising reinforced titanium or titanium based alloy matrix materials.
This patent application is currently assigned to BAKER HUGHES INCORPORATED. Invention is credited to Heeman Choe, Jimmy W. Eason, James L. Overstreet, John H. Stevens, James C. Westhoff.
Application Number | 20110094341 12/871670 |
Document ID | / |
Family ID | 39204907 |
Filed Date | 2011-04-28 |
United States Patent
Application |
20110094341 |
Kind Code |
A1 |
Choe; Heeman ; et
al. |
April 28, 2011 |
METHODS OF FORMING EARTH BORING ROTARY DRILL BITS INCLUDING BIT
BODIES COMPRISING REINFORCED TITANIUM OR TITANIUM BASED ALLOY
MATRIX MATERIALS
Abstract
Earth-boring rotary drill bits include bit bodies comprising a
composite material including a plurality of hard phase regions or
particles dispersed throughout a titanium or titanium-based alloy
matrix material. The bits further include a cutting structure
disposed on a face of the bit body. In some embodiments, the bit
bodies may include a plurality of regions having differing material
compositions. For example, the bit bodies may include a first
region comprising a plurality of hard phase regions or particles
dispersed throughout a titanium or titanium-based alloy matrix
material, and a second region comprising a titanium or a
titanium-based alloy material. Methods for forming such drill bits
include at least partially sintering a plurality of hard particles
and a plurality of particles comprising titanium or a
titanium-based alloy material to form a bit body comprising a
particle-matrix composite material. A shank may be attached
directly to the bit body.
Inventors: |
Choe; Heeman; (Seoul,
KR) ; Stevens; John H.; (Spring, TX) ;
Overstreet; James L.; (Tomball, TX) ; Westhoff; James
C.; (The Woodlands, TX) ; Eason; Jimmy W.;
(The Woodlands, TX) |
Assignee: |
BAKER HUGHES INCORPORATED
Houston
TX
|
Family ID: |
39204907 |
Appl. No.: |
12/871670 |
Filed: |
August 30, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11593437 |
Nov 6, 2006 |
7784567 |
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12871670 |
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11271153 |
Nov 10, 2005 |
7802495 |
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11593437 |
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11272439 |
Nov 10, 2005 |
7776256 |
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11271153 |
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Current U.S.
Class: |
76/108.2 |
Current CPC
Class: |
C22C 14/00 20130101;
C22C 29/005 20130101; B22F 7/08 20130101; E21B 10/00 20130101; B22F
7/062 20130101; B22F 2998/10 20130101; C22C 32/0047 20130101; E21B
10/567 20130101; B22F 2998/10 20130101; B22F 7/062 20130101; C22C
1/051 20130101; B22F 3/04 20130101; B22F 3/162 20130101; B22F
2005/002 20130101 |
Class at
Publication: |
76/108.2 |
International
Class: |
B21K 5/04 20060101
B21K005/04 |
Claims
1. A method of forming an earth-boring rotary drill bit, the method
comprising: providing a bit body comprising a particle-matrix
composite material, providing a bit body comprising: providing a
green powder component comprising: a plurality of particles each
comprising a hard material; and a plurality of particles each
comprising titanium or a titanium-based alloy material; and at
least partially sintering the green powder component; providing a
shank configured for attachment to a drill string; and attaching
the shank directly to the bit body.
2. The method of claim 1, wherein providing a green powder
component comprises: pressing a first powder mixture to form a
first green structure, the first powder mixture comprising at least
a portion of the plurality of particles each comprising a hard
material and a portion of the plurality of particles each
comprising titanium or a titanium-based alloy material; pressing a
second powder mixture to fowl a second green structure, the second
powder mixture comprising a portion of the plurality of particles
each comprising titanium or a titanium-based alloy material; and
assembling the first green structure with the second green
structure to form the green powder component.
3. The method of claim 2, wherein pressing the first powder mixture
comprises heating the first powder mixture and subjecting the first
powder mixture to substantially isostatic pressure, and wherein
pressing the second powder mixture comprises heating the second
powder mixture and subjecting the second powder mixture to
substantially isostatic pressure.
4. The method of claim 1, wherein providing a green powder
component comprises: providing a first powder mixture in a first
region of a deformable container, the first powder mixture
comprising at least a portion of the plurality of particles each
comprising a hard material and a portion of the plurality of
particles each comprising titanium or a titanium-based alloy
material; providing a second powder mixture in a second region of
the deformable container adjacent the first powder mixture, the
second powder mixture comprising a portion of the plurality of
particles each comprising titanium or a titanium-based alloy
material; sealing the first powder mixture and the second powder
mixture within the deformable container; and subjecting the
deformable container to substantially isostatic pressure.
5. The method of claim 1, further comprising machining at least one
feature in the green powder component prior to at least partially
sintering the green powder component.
6. The method of claim 1, wherein at least partially sintering the
green powder component comprises: partially sintering the green
powder component to form a brown structure; machining at least one
feature in the brown structure; and sintering the brown structure
to a desired final density.
7. The method of claim 1, wherein attaching the shank directly to
the bit body comprises: providing a retaining member; aligning at
least one aperture extending through an outer wall of the shank
with at least one groove in a surface of the bit body; and
inserting the retaining member through at least a portion of the at
least one aperture extending through the outer wall of the shank
and at least a portion of the at least one groove in the surface of
the bit body.
8. The method of claim 7, wherein inserting the retaining member
comprises providing a substantially uniform gap between at least
one surface of the shank and at least one surface of the bit
body.
9. The method of claim 8, wherein the substantially uniform gap is
between about 50 microns (0.002 inch) and about 150 microns (0.006
inch).
10. The method of claim 8, further comprising providing a brazing
alloy in the substantially uniform gap between the at least one
surface of the shank and the at least one surface of the bit
body.
11. The method of claim 8, further comprising welding an interface
between the shank and the bit body.
12. The method of claim 1, further comprising subjecting at least a
portion of the bit body to a thermal processing treatment
comprising at least one of annealing, solution-treating, and
aging.
13. The method of claim 1, further comprising providing a layer of
titanium nitride on at least a portion of a surface of the bit body
configured to engage a subterranean formation during drilling.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/593,437, filed Nov. 6, 2006, which will issue as U.S.
Pat. No. 7,784,567 on Aug. 31, 2010, which application is a
continuation-in-part of application Ser. No. 11/271,153, filed Nov.
10, 2005, pending, the disclosure of which is incorporated herein
in its entirety by this reference. This application is also a
continuation-in-part of application Ser. No. 11/272,439, filed Nov.
10, 2005, now U.S. Pat. No. 7,776,256, issued Aug. 17, 2010, the
disclosure of which is also incorporated herein in its entirety by
this reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to earth-boring
rotary drill bits, and to methods of manufacturing such
earth-boring rotary drill bits. More particularly, the present
invention generally relates to earth-boring rotary drill bits that
include a bit body having at least a portion thereof substantially
formed of a particle-matrix composite material, and to methods of
manufacturing such earth-boring rotary drill bits.
[0004] 2. State of the Art
[0005] Rotary drill bits are commonly used for drilling bore holes,
or well bores, in earth formations. Rotary drill bits include two
primary configurations. One configuration is the roller cone bit,
which conventionally includes three roller cones mounted on support
legs that extend from a bit body. Each roller cone is configured to
spin or rotate on a support leg. Teeth are provided on the outer
surfaces of each roller cone for cutting rock and other earth
formations. The teeth often are coated with an abrasive, hard
("hardfacing") material. Such materials often include tungsten
carbide particles dispersed throughout a metal alloy matrix
material. Alternatively, receptacles are provided on the outer
surfaces of each roller cone into which hard metal inserts are
secured to form the cutting elements. In some instances, these
inserts comprise a superabrasive material formed on and bonded to a
metallic substrate. The roller cone drill bit may be placed in a
bore hole such that the roller cones abut against the earth
formation to be drilled. As the drill bit is rotated under applied
weight on bit, the roller cones roll across the surface of the
formation, and the teeth crush the underlying formation.
[0006] A second primary configuration of a rotary drill bit is the
fixed-cutter bit (often referred to as a "drag" bit), which
conventionally includes a plurality of cutting elements secured to
a face region of a bit body. Generally, the cutting elements of a
fixed-cutter type drill bit have either a disk shape or a
substantially cylindrical shape. A hard, superabrasive material,
such as mutually bonded particles of polycrystalline diamond, may
be provided on a substantially circular end surface of each cutting
element to provide a cutting surface. Such cutting elements are
often referred to as "polycrystalline diamond compact" (PDC)
cutters. The cutting elements may be fabricated separately from the
bit body and are secured within pockets formed in the outer surface
of the bit body. A bonding material such as an adhesive or a braze
alloy may be used to secure the cutting elements to the bit body.
The fixed-cutter drill bit may be placed in a bore hole such that
the cutting elements abut against the earth formation to be
drilled. As the drill bit is rotated, the cutting elements scrape
across and shear away the surface of the underlying formation.
[0007] The bit body of a rotary drill bit of either primary
configuration may be secured, as is conventional, to a hardened
steel shank having an American Petroleum Institute (API) threaded
pin for attaching the drill bit to a drill string. The drill string
includes tubular pipe and equipment segments coupled end to end
between the drill bit and other drilling equipment at the surface.
Equipment such as a rotary table or top drive may be used for
rotating the drill string and the drill bit within the bore hole.
Alternatively, the shank of the drill bit may be coupled directly
to the drive shaft of a down-hole motor, which then may be used to
rotate the drill bit.
[0008] The bit body of a rotary drill bit may be formed from steel.
Alternatively, the bit body may be formed from a particle-matrix
composite material. Such particle-matrix composite materials
conventionally include hard tungsten carbide particles randomly
dispersed throughout a copper or copper-based alloy matrix material
(often referred to as a "binder" material). Such bit bodies
conventionally are formed by embedding a steel blank in tungsten
carbide particulate material within a mold, and infiltrating the
particulate tungsten carbide material with molten copper or
copper-based alloy material. Drill bits that have bit bodies formed
from such particle-matrix composite materials may exhibit increased
erosion and wear resistance, but lower strength and toughness,
relative to drill bits having steel bit bodies.
[0009] As subterranean drilling conditions and requirements become
ever more rigorous, there arises a need in the art for novel
particle-matrix composite materials for use in bit bodies of rotary
drill bits that exhibit enhanced physical properties and that may
be used to improve the performance of earth-boring rotary drill
bits.
BRIEF SUMMARY OF THE INVENTION
[0010] In one embodiment, the present invention includes an
earth-boring rotary drill bit for drilling a subterranean
formation. The drill bit includes a bit body comprising a
particle-matrix composite material having a plurality of hard
particles or regions dispersed throughout a titanium or
titanium-based alloy matrix material. The drill bit further
includes at least one cutting structure on a face of the bit
body.
[0011] In another embodiment, the present invention includes an
earth-boring rotary drill bit comprising a bit body having a
plurality of regions having differing material compositions. For
example, the bit body of the drill bit may include a first region
having a first material composition and a second region having a
second material composition that differs from the first material
composition. The first material composition may include a plurality
of hard particles or regions dispersed throughout a titanium or
titanium-based alloy matrix material, and the second material
composition may comprise a titanium or a titanium-based alloy
material. Furthermore, a plurality of cutting structures may be
disposed on a surface of the bit body.
[0012] In yet another embodiment, the present invention includes a
method of forming an earth-boring rotary drill bit. The method
includes providing a green powder component comprising a plurality
of hard particles and a plurality of particles comprising titanium
or a titanium-based alloy material, and at least partially
sintering the green powder component to form a bit body comprising
a particle-matrix composite material. A shank configured for
attachment to a drill string may be attached directly to the bit
body.
[0013] The features, advantages, and additional aspects of the
present invention will be apparent to those skilled in the art from
a consideration of the following detailed description considered in
combination with the accompanying drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0014] 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 conjunction with the accompanying drawings in
which:
[0015] FIG. 1 is a partial cross-sectional side view of an
earth-boring rotary drill bit that embodies teachings of the
present invention and includes a bit body comprising a
particle-matrix composite material;
[0016] FIG. 2 is a partial cross-sectional side view of another
earth-boring rotary drill bit that embodies teachings of the
present invention and includes a bit body comprising a
particle-matrix composite material;
[0017] FIGS. 3A-3J illustrate one example of a method that may be
used to form the bit body of the earth-boring rotary drill bit
shown in FIG. 2;
[0018] FIGS. 4A-4C illustrate another example of a method that may
be used to form the bit body of the earth-boring rotary drill bit
shown in FIG. 2;
[0019] FIG. 5 is a side view of a shank shown in FIG. 2;
[0020] FIG. 6 is a cross-sectional view of the shank shown in FIG.
5 taken along section line 6-6 shown therein;
[0021] FIG. 7 is a cross-sectional side view of yet another bit
body that includes a particle-matrix composite material and that
embodies teachings of the present invention;
[0022] FIG. 8 is a cross-sectional view of the bit body shown in
FIG. 7 taken along section line 8-8 shown therein; and
[0023] FIG. 9 is a cross-sectional side view of still another bit
body that includes a particle-matrix composite material and that
embodies teachings of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The illustrations presented herein are not meant to be
actual views of any particular material, apparatus, 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.
[0025] The term "green" as used herein means unsintered.
[0026] The term "green bit body" as used herein means an unsintered
structure comprising a plurality of discrete particles held
together by a binder material, the structure having a size and
shape allowing the formation of a bit body suitable for use in an
earth-boring drill bit from the structure by subsequent
manufacturing processes including, but not limited to, machining
and densification.
[0027] The term "brown" as used herein means partially
sintered.
[0028] The term "brown bit body" 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, the structure having a
size and shape allowing the formation of a bit body suitable for
use in an earth-boring drill bit from the structure by subsequent
manufacturing processes including, but not limited to, machining
and further densification. Brown bit bodies may be formed by, for
example, partially sintering a green bit body.
[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] 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.
[0031] An earth-boring rotary drill bit 10 that embodies teachings
of the present invention is shown in FIG. 1. The drill bit 10
includes a bit body 12 comprising a particle-matrix composite
material 15 that includes a plurality of hard phase particles or
regions dispersed throughout a titanium or a titanium-based alloy
matrix material. The hard phase particles or regions are "hard" in
the sense that they are relatively harder than the surrounding
titanium or a titanium-based alloy matrix material. In some
embodiments, the bit body 12 may be predominantly comprised of the
particle-matrix composite material 15, which is described in
further detail below. The bit body 12 may be fastened to a metal
shank 20, which may be formed from steel and may include an
American Petroleum Institute (API) threaded pin 28 for attaching
the drill bit 10 to a drill string (not shown). The bit body 12 may
be secured directly to the shank 20 by, for example, using one or
more retaining members 46 in conjunction with brazing and/or
welding, as discussed in further detail below.
[0032] As shown in FIG. 1, the bit body 12 may include wings or
blades 30 that are separated from one another by junk slots 32.
Internal fluid passageways 42 may extend between the face 18 of the
bit body 12 and a longitudinal bore 40, which extends through the
steel shank 20 and at least partially through the bit body 12. In
some embodiments, nozzle inserts (not shown) may be provided at the
face 18 of the bit body 12 within the internal fluid passageways
42.
[0033] The drill bit 10 may include a plurality of cutting
structures on the face 18 thereof. By way of example and not
limitation, a plurality of polycrystalline diamond compact (PDC)
cutters 34 may be provided on each of the blades 30, as shown in
FIG. 1. The PDC cutters 34 may be provided along the blades 30
within pockets 36 formed in the face 18 of the bit body 12, and may
be supported from behind by buttresses 38, which may be integrally
formed with the bit body 12.
[0034] The particle-matrix composite material 15 of the bit body 12
may include a plurality of hard phase regions or particles
dispersed throughout a titanium or a titanium-based alloy matrix
material. By way of example and not limitation, the hard phase
regions may be formed from a plurality of hard particles, and may
comprise between about 20% and about 60% by volume of the
particle-matrix composite material 15, and the matrix material may
comprise between about 80% and about 40% by volume of the
particle-matrix composite material 15.
[0035] In some embodiments, the particle-matrix composite material
15 of the bit body 12 may comprise a ceramic-metal composite
material (i.e., a "cermet" material). In other words, the hard
phase regions or particles may comprise a ceramic material.
[0036] Titanium has two allotropic phases: a hexagonal close-packed
.alpha. phase and a body-centered cubic .beta. phase. In
commercially pure titanium, the .alpha. phase is stable at
temperatures below about 882.degree. C., while the .beta. phase is
stable at temperatures between about 882.degree. C. and the melting
point of about 1668.degree. C. of commercially pure titanium.
Various elements have been identified that may be dissolved in
titanium to form a solid solution and that can affect the stability
of either the .alpha. phase or the .beta. phase. Elements that
stabilize the .alpha. phase are referred to in the art as .alpha.
stabilizers, while elements that stabilize the .beta. phase are
referred to in the art as .beta. stabilizers. For example,
aluminum, gallium, oxygen, nitrogen, and carbon have been
identified as .alpha. stabilizers, and vanadium, molybdenum,
niobium, iron, chromium, and nickel have been identified as .beta.
stabilizers. Some elements, including tin and zinc for example,
enter into solid solution with titanium do not significantly
stabilize either the .alpha. phase or the .beta. phase. These
elements may be referred to as neutral alloying elements.
[0037] Various titanium-based alloys may be prepared that include
one or more .alpha. stabilizers, one or more .beta. stabilizers,
and/or one or more neutral alloying elements. These titanium-based
alloys are conventionally categorized as either alpha (.alpha.)
alloys, near alpha (.alpha.) alloys, metastable beta (.beta.)
alloys, beta (.beta.) alloys, .alpha.+.beta. alloys, or titanium
aluminides. Alpha alloys are single-phase alloys that are solid
solution strengthened by the addition of .alpha. stabilizers and/or
neutral alloying elements. Near alpha alloys include small amounts
(conventionally between about 1 and about 2 atomic percent (At. %))
of .beta. stabilizers. Near alpha alloys may include primarily
.alpha. phase (alpha alloy) with some retained .beta. phase (beta
alloy or metastable beta alloy) in the final microstructure.
Metastable beta alloys conventionally include between about 10 and
about 15 atomic percent .beta. stabilizers and predominantly
comprise metastable (non-equilibrium) .beta. phase at room
temperature. Beta alloys include sufficient amounts of .beta.
stabilizers (e.g., about 30 atomic percent) so as to render the
.beta. phase stable at room temperature. .alpha.+.beta. alloys
include significant amounts of both the .alpha. phase and the
.beta. phase (e.g., the .alpha. phase and the .beta. phase comprise
at least about 10% by volume of the alloy). Titanium aluminides are
based on the intermetallic compounds Ti.sub.3Al (often referred to
as the .alpha..sub.2 phase) and TiAl (often referred to as the
.gamma. phase).
[0038] In some embodiments of the present invention, the titanium
or titanium-based matrix material may include an .alpha.+.beta.
titanium alloy. For example, the titanium or titanium-based matrix
material may include at least about 87.5 weight percent titanium,
approximately 6.0 weight percent aluminum, and approximately 4.0
weight percent vanadium (such alloys are often referred to in the
art as Ti-6Al-4V or Ti-64 alloys). Such titanium-based alloys may
further include at least trace amounts of at least one of tin,
copper, iron, and carbon. In some embodiments, the titanium or
titanium-based matrix material may include about 89.0 weight
percent titanium (e.g., between about 88.0 weight percent and about
90.0 weight percent), about 6.0 weight percent aluminum, and about
4.0 weight percent vanadium.
[0039] Table 1 below sets forth various examples of compositions of
.alpha.+.beta. titanium alloys that may be used as the matrix
material in the particle-matrix composite material 15 of the bit
body 12 shown in FIG. 1.
TABLE-US-00001 TABLE 1 .alpha. + .beta. Alloys Example Approximate
Elemental Atomic Percent No. Al V Mo Zr Sn Si Fe Ti 1 6.0 4.0 -- --
-- -- -- Balance 2 6.0 6.0 -- -- 2.0 -- 0.7 Balance 3 4.0 -- 4.0 --
2.0 0.5 -- Balance 4 2.25 -- 4.0 -- 11.0 0.2 -- Balance 5 6.0 --
6.0 4.0 2.0 -- -- Balance
[0040] In additional embodiments of the present invention, the
titanium or titanium-based matrix material may include a beta
(.beta.) titanium alloy or a metastable beta (.beta.) titanium
alloy. Table 2 below sets forth various examples of compositions of
beta (.beta.) titanium alloys that may be used as the matrix
material in the particle-matrix composite material 15 of the bit
body 12 shown in FIG. 1, and Table 3 below sets forth various
compositions of metastable beta (.beta.) titanium alloys that may
be used as the matrix material in the particle-matrix composite
material 15 of the bit body 12 shown in FIG. 1.
TABLE-US-00002 TABLE 2 Beta (.beta.) Alloys Example Approximate
Elemental Atomic Percent No. Al Nb V Mo Zr Sn Si Cr Fe Ti 6 1.5 --
-- 6.8 -- -- -- -- 4.5 Balance 7 3.0 -- 10.0 -- -- -- -- -- 2.0
Balance 8 -- -- -- 11.5 6.0 4.5 -- -- -- Balance 9 3.0 2.6 -- 15.0
-- -- 0.2 -- -- Balance
TABLE-US-00003 TABLE 3 Metastable Beta (.beta.) Alloys Exam- ple
Approximate Elemental Atomic Percent No. Al Nb V Mo Zr Sn Si Cr Fe
W Ti 10 -- -- 35.0 -- -- -- -- 15.0 -- -- Balance 11 -- -- -- 40.0
-- -- -- -- -- -- Balance 12 -- -- -- 30.0 -- -- -- -- -- --
Balance 13 -- -- -- -- -- -- -- -- -- 30 Balance
[0041] In yet additional embodiments of the present invention, at
least a portion of the bit body 12 may comprise a titanium or
titanium-based matrix material that includes an alpha (.alpha.)
titanium alloy. Table 4 below sets forth various examples of
compositions of alpha (.alpha.) titanium alloys (including near
alpha (.alpha.) titanium alloys) that may be used as the matrix
material in the particle-matrix composite material 15 of at least a
portion of the bit body 12 shown in FIG. 1.
TABLE-US-00004 TABLE 4 Alpha (.alpha.) Alloys Example Approximate
Elemental Atomic Percent No. Al Nb V Mo Zr Sn Si Pd C Ti 14 -- --
-- -- -- -- -- 0.2 -- Balance 15 5.0 -- -- -- -- 2.5 -- -- --
Balance 16 8.0 -- 1.0 1.0 -- -- -- -- -- Balance 17 6.0 -- -- 2.0
4.0 2.0 -- -- -- Balance 18 2.25 -- -- 1.0 5.0 11.0 -- -- --
Balance 19 6.0 -- -- 0.5 5.0 -- 0.25 -- -- Balance 20 6.0 0.7 --
0.5 3.5 4.0 0.35 -- 0.06 Balance
[0042] Titanium-based alloys, similar to the examples set forth in
Tables 1-4, are capable of exhibiting ultimate tensile strengths in
excess of 1,000 megapascals (MPa), fracture toughnesses of greater
than about 100 megapascals-square root meter (MPa-m.sup.1/2), and
hardnesses of greater than about 350 on the Vickers Hardness
Scale.
[0043] Any titanium-based alloy (in addition to those alloys set
forth as examples in Tables 1-4) may be used as matrix material in
the particle-matrix composite material 15 of bit bodies that embody
teachings of the present invention (such as, for example, the bit
body 12 of the drill bit 10 shown in FIG. 1).
[0044] In some embodiments, at least a portion of the matrix
material of the particle-matrix composite material 15 may be
thermally processed (i.e., heat treated) to refine or tailor the
microstructure of the matrix material and impart one or more
desired physical properties (i.e., increased strength, hardness,
fracture toughness, etc.) to the matrix material (and, hence, the
particle-matrix composite material 15), as necessary or desired. By
way of example and not limitation, at least a portion of the
titanium or titanium-based alloy matrix material may be in an
annealed condition. By annealing the titanium or titanium-based
alloy matrix material, the fracture toughness of the
particle-matrix composite material 15 may be increased or otherwise
selectively tailored. As another example, at least a portion of the
titanium or titanium-based alloy matrix material may be in a
solution-treated (ST) condition or a solution-treated and aged
(STA) condition. By solution treating and aging the titanium or
titanium-based alloy matrix material, the strength of the
particle-matrix composite material 15 may be increased or otherwise
selectively tailored. Due to the relative stability of the hard
phase (e.g., a ceramic phase), these thermal processing techniques
generally may be carried out on the titanium or titanium-based
alloy matrix material of the particle-matrix composite material 15
without adversely affecting the hard phase of the particle-matrix
composite material 15 and/or the surrounding interfacial region
between the hard phase and the metal phase of the particle-matrix
composite material 15.
[0045] The hard phase regions of the particle-matrix composite
material 15 may include a plurality of at least one of titanium
carbide (TiC) particles, titanium diboride (TiB.sub.2) particles,
and tungsten (W) particles. By way of example and not limitation,
the hard phase regions may comprise between about 20% by volume and
about 60% by volume of the particle-matrix composite material 15.
In additional embodiments, the hard phase regions may comprise
particles of titanium silicide (e.g., Ti.sub.5Si.sub.3 and/or
Ti.sub.3Si), which may be formed by, for example, the decomposition
of silicon nitride (Si.sub.3N.sub.4) particles during sintering
and/or annealing of the particle-matrix composite material 15. In
addition to those specifically recited herein, any hard phase
regions that increase the wear resistance of the particle-matrix
composite material 15 and are chemically compatible with the matrix
material may be used in embodiments of the present invention.
[0046] In some embodiments, the hard phase regions may have
different sizes. Furthermore, in some embodiments, the plurality of
hard phase regions may include or exhibit a multi-modal particle
size distribution (e.g., bi-modal, tri-modal, tetra-modal,
penta-modal, etc.), while in other embodiments, the hard phase
regions may have a substantially uniform particle size. By way of
example and not limitation, the plurality of hard phase regions may
include a plurality of -20 ASTM (American Society for Testing and
Materials) Mesh hard phase regions. As used herein, the phrase "-20
ASTM mesh particles" means particles that pass through an ASTM No.
20 U.S.A. standard testing sieve as defined in ASTM Specification
E11-04, which is entitled Standard Specification for Wire Cloth and
Sieves for Testing Purposes.
[0047] Each of the hard phase regions may have a three-dimensional
shape that is generally spherical, rectangular, cubic, pentagonal,
hexagonal, etc. Furthermore, in some embodiments, each hard phase
region may comprise a single crystal.
[0048] With continued reference to FIG. 1, at least a portion of
the exterior surface of the bit body 12 may be coated with a
wear-resistant coating (not shown). By way of example and not
limitation, the wear-resistant coating may comprise a layer of
titanium nitride formed on or in exposed surfaces of at least the
titanium or titanium-based alloy matrix material of the
particle-matrix composite material 15. The layer of titanium
nitride may be formed on or in exposed surfaces of the
particle-matrix composite material 15 that are configured to engage
a formation being drilled by the drill bit 10. In additional
embodiments, the wear-resistant coating may comprise titanium
diboride, or any other material configured to enhance the
wear-resistance of the particle-matrix composite material 15.
Furthermore, the wear-resistant coating may be strategically placed
on various regions of exposed surfaces of the bit body so as to
protect regions of the particle-matrix composite material 15 that
may be subjected to relatively greater wear during drilling. For
example, the face 18 of the bit body 12 (e.g., the
formation-engaging surfaces of the blades 30) may be at least
partially covered or otherwise provided with a coating or layer of
titanium nitride or other wear-resistant material. In particular,
surfaces of the blades 30 between adjacent cutters 34 and surfaces
of the blades 30 rotationally behind the cutters 34 may be at least
partially covered or otherwise provided with a coating or layer of
titanium nitride or other wear-resistant material.
[0049] During drilling operations, the drill bit 10 may be
positioned at the bottom of a well bore and rotated while drilling
fluid is pumped to the face 18 of the bit body 12 through the
longitudinal bore 40 and the internal fluid passageways 42. As the
PDC cutters 34 shear or scrape away the underlying earth formation,
the formation cuttings and detritus are mixed with and suspended
within the drilling fluid, which passes through the junk slots 32
and the annular space between the well bore hole and the drill
string to the surface of the earth formation.
[0050] Another earth-boring rotary drill bit 70 that embodies
teachings of the present invention is shown in FIG. 2. The rotary
drill bit 70 is generally similar to the previously described
rotary drill bit 10 and has a bit body 72 that includes a
particle-matrix composite material comprising a plurality of hard
phase regions or particles dispersed throughout a titanium or a
titanium-based alloy matrix material. The drill bit 70 may also
include a shank 20 attached directly to the bit body 72. The shank
20 includes a generally cylindrical outer wall having an outer
surface and an inner surface. The outer wall of the shank 20
encloses at least a portion of a longitudinal bore 40 that extends
through the drill bit 70. At least one surface of the outer wall of
the shank 20 may be configured for attachment of the shank 20 to
the bit body 72. The shank 20 also may include a male or female API
threaded connection portion 28 for attaching the drill bit 70 to a
drill string (not shown). One or more apertures 21 may extend
through the outer wall of the shank 20. These apertures are
described in greater detail below.
[0051] The bit body 72 of the drill bit 70 includes a plurality of
regions having different material compositions. By way of example
and not limitation, the bit body 72 may include a first region 74
having a first material composition and a second region 76 having a
second, different material composition. The first region 74 may
include the longitudinally lower and laterally outward regions of
the bit body 72 (e.g., the crown region of the bit body 72). The
first region 74 may include the face 18 of the bit body 72, which
may be configured to carry a plurality of cutting elements, such as
PDC cutters 34. For example, a plurality of pockets 36 and
buttresses 38 may be provided in or on the face 18 of the bit body
72 for carrying and supporting the PDC cutters 34. Furthermore, a
plurality of blades 30 and junk slots 32 may be provided in the
first region 74 of the bit body 72. The second region 76 may
include the longitudinally upper and laterally inward regions of
the bit body 72. The longitudinal bore 40 may extend at least
partially through the second region 76 of the bit body 72.
[0052] The second region 76 may include at least one surface 14
that is configured for attachment of the bit body 72 to the shank
20. By way of example and not limitation, at least one groove 16
may be formed in at least one surface 14 of the second region 76
that is configured for attachment of the bit body 72 to the shank
20. Each groove 16 may correspond to and be aligned with an
aperture 21 extending through the outer wall of the shank 20. A
retaining member 46 may be provided within each aperture 21 in the
shank 20 and each groove 16. Mechanical interference between the
shank 20, the retaining member 46, and the bit body 72 may prevent
longitudinal separation of the bit body 72 from the shank 20, and
may prevent rotation of the bit body 72 about a longitudinal axis
L.sub.70 of the rotary drill bit 70 relative to the shank 20.
[0053] In some embodiments, the bit body 72 of the rotary drill bit
70 may be predominantly comprised of a particle-matrix composite
material. Furthermore, the composition of the particle-matrix
composite material may be selectively varied within the bit body 72
to provide various regions within the bit body 72 that have
different, custom tailored physical properties or
characteristics.
[0054] In the embodiment shown in FIG. 2, the rotary drill bit 70
includes two retaining members 46. By way of example and not
limitation, each retaining member 46 may include an elongated,
cylindrical rod that extends through an aperture 21 in the shank 20
and a groove 16 formed in a surface 14 of the bit body 72.
[0055] The mechanical interference between the shank 20, the
retaining member 46, and the bit body 72 may also provide a
substantially uniform clearance or gap between a surface of the
shank 20 and the surfaces 14 in the second region 76 of the bit
body 72. By way of example and not limitation, a substantially
uniform gap of between about 50 microns (0.002 inch) and about 150
microns (0.006 inch) may be provided between the shank 20 and the
bit body 72 when the retaining members 46 are disposed within the
apertures 21 in the shank 20 and the grooves 16 in the bit body
72.
[0056] A brazing material 26 such as, for example, a silver-based
or a nickel-based metal alloy may be provided in the substantially
uniform gap between the shank 20 and the surfaces 14 of the second
region 76 of the bit body 72. As an alternative to brazing, or in
addition to brazing, a weld 24 may be provided around the rotary
drill bit 70 on an exterior surface thereof along an interface
between the bit body 72 and the steel shank 20. The weld 24 and the
brazing material 26 may be used to further secure the shank 20 to
the bit body 72. In this configuration, if the brazing material 26
in the substantially uniform gap between the shank 20 and the
surfaces 14 in the second region 76 of the bit body 72 and the weld
24 should fail while the drill bit 70 is located at the bottom of a
wellbore during a drilling operation, the retaining members 46 may
prevent longitudinal separation of the bit body 72 from the shank
20, thereby preventing loss of the bit body 72 in the wellbore.
[0057] As previously stated, the first region 74 of the bit body 72
may have a first material composition and the second region 76 of
the bit body 72 may have a second, different material composition.
The first region 74 may include a particle-matrix composite
material comprising a plurality of hard phase regions or particles
dispersed throughout a titanium or titanium-based alloy matrix
material. The second region 76 of the bit body 72 may include a
metal, a metal alloy, or a particle-matrix composite material. For
example, the second region 76 of the bit body 72 may be
predominantly comprised of a titanium or a titanium-based alloy
material substantially identical to the matrix material of the
particle-matrix composite material in the first region 74. In
additional embodiments of the present invention, both the first
region 74 and the second region 76 of the bit body 72 may be
substantially formed from and at least predominantly composed of a
particle-matrix composite material.
[0058] By way of example and not limitation, the first region 74 of
the bit body 72 may include a plurality of titanium carbide and/or
titanium diboride regions or particles dispersed throughout a
matrix material comprising any one of the .alpha.+.beta. alloys set
forth in Table 1, the beta (.beta.) alloys set forth in Table 2, or
the metastable beta (.beta.) alloys set forth in Table 3, and the
second region 74 of the bit body 72 may comprise any one of the
alpha (.alpha.) alloys set forth in Table 4. In additional
embodiments, the second region 74 of the bit body 72 may comprise
any one of the .alpha.+.beta. alloys set forth in Table 1, the beta
(.beta.) alloys set forth in Table 2, or the metastable beta
(.beta.) alloys set forth in Table 3. In this configuration, the
material composition of the first region 74 may be selected to
exhibit higher erosion and wear-resistance than the material
composition of the second region 76. Furthermore, the material
composition of the second region 76 may be selected to enhance
machinability of the second region 76 and facilitate attachment of
the bit body 72 to the shank 20.
[0059] The manner in which the physical properties may be tailored
to facilitate machining of the second region 76 may be at least
partially dependent of the method of machining that is to be used.
For example, if it is desired to machine the second region 76 using
conventional turning, milling, and drilling techniques, the
material composition of the second region 76 may be selected to
exhibit lower hardness and higher ductility. If it is desired to
machine the second region 76 using ultrasonic machining techniques,
which may include the use of ultrasonically induced vibrations
delivered to a tool, the composition of the second region 76 may be
selected to exhibit a higher hardness and a lower ductility.
[0060] In some embodiments, the material composition of the second
region 76 may be selected to exhibit higher fracture toughness than
the material composition of the first region 74. In yet other
embodiments, the material composition of the second region 76 may
be selected to exhibit physical properties that are tailored to
facilitate welding of the second region 76. By way of example and
not limitation, the material composition of the second region 76
may be selected to facilitate welding of the second region 76 to
the shank 20. It is understood that the various regions of the bit
body 72 may have material compositions that are selected or
tailored to exhibit any desired particular physical property or
characteristic, and the present invention is not limited to
selecting or tailing the material compositions of the regions to
exhibit the particular physical properties or characteristics
described herein.
[0061] Certain physical properties and characteristics of a
composite material (such as hardness) may be defined using an
appropriate rule of mixtures, as is known in the art. Other
physical properties and characteristics of a composite material may
be determined without resort to the rule of mixtures. Such physical
properties may include, for example, erosion and wear
resistance.
[0062] FIGS. 3A-3J illustrate one example of a method that may be
used to form the bit body 72 shown in FIG. 2. Generally, the bit
body 72 of the rotary drill bit 70 may be formed by separately
forming the first region 74 and the second region 76 as brown
structures, assembling the brown structures together to provide a
unitary brown bit body, and sintering the unitary brown bit body to
a desired final density.
[0063] Referring to FIG. 3A, a first powder mixture 109 may be
pressed in a mold or die 106 using a movable piston or plunger 108.
The first powder mixture 109 may include a plurality of hard
particles and a plurality of particles comprising a titanium or a
titanium-based alloy matrix material. By way of example and not
limitation, the first powder mixture 109 may include a plurality of
titanium carbide and/or titanium diboride particles, as well as a
plurality of particles each comprising any of the .alpha.+.beta.
alloys set forth in Table 1, the beta (.beta.) alloys set forth in
Table 2, or the metastable beta (.beta.) alloys set forth in Table
3. Optionally, the powder mixture 109 may further include additives
commonly used when pressing powder mixtures such as, for example,
binders for providing lubrication during pressing and 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.
[0064] The die 106 may include an inner cavity having surfaces
shaped and configured to form at least some surfaces of the first
region 74 of the bit body 72. The plunger 108 may also have
surfaces configured to form or shape at least some of the surfaces
of the first region 74 of the bit body 72. Inserts or displacements
107 may be positioned within the die 106 and used to define the
internal fluid passageways 42. Additional displacements 107 (not
shown) may be used to define cutting element pockets 36, junk slots
32, and other topographic features of the first region 74 of the
bit body 72.
[0065] The plunger 108 may be advanced into the die 106 at high
force using mechanical or hydraulic equipment or machines to
compact the first powder mixture 109 within the die 106 to form a
first green powder component 110, shown in FIG. 3B. The die 106,
plunger 108, and the first powder mixture 109 optionally may be
heated during the compaction process.
[0066] In additional methods of pressing the powder mixture 109,
the powder mixture 109 may be pressed with substantially isostatic
pressures inside a pliable, hermetically sealed container that is
provided within a pressure chamber.
[0067] The first green powder component 110 shown in FIG. 3B may
include a plurality of particles (hard particles of hard material
and particles of matrix material) held together by a binder
material provided in the powder mixture 109 (FIG. 3A), as
previously described. Certain structural features may be machined
in the green powder component 110 using conventional machining
techniques including, for example, turning techniques, milling
techniques, and drilling techniques. Hand held tools also may be
used to manually form or shape features in or on the green powder
component 110. By way of example and not limitation, junk slots 32
(FIG. 2) may be machined or otherwise formed in the green powder
component 110.
[0068] The first green powder component 110 shown in FIG. 3B may be
at least partially sintered. For example, the green powder
component 110 may be partially sintered to provide a first brown
structure 111 shown in FIG. 3C, which has less than a desired final
density. Prior to sintering, the green powder component 110 may be
subjected to moderately elevated temperatures to aid in the removal
of any fugitive additives that were included in the powder mixture
109 (FIG. 3A), as previously described. Furthermore, the green
powder component 110 may be subjected to a suitable atmosphere
tailored to aid in the removal of such additives. Such atmospheres
may include, for example, hydrogen gas at a temperature of about
500.degree. C.
[0069] Certain structural features may be machined in the first
brown structure 111 using conventional machining techniques
including, for example, turning techniques, milling techniques, and
drilling techniques. Hand held tools may also be used to manually
form or shape features in or on the brown structure 111. By way of
example and not limitation, cutter pockets 36 may be machined or
otherwise formed in the brown structure 111 to form a shaped brown
structure 112 shown in FIG. 3D.
[0070] Referring to FIG. 3E, a second powder mixture 119 may be
pressed in a mold or die 116 using a movable piston or plunger 118.
The second powder mixture 119 may include a plurality of particles
comprising a titanium or titanium-based alloy matrix material, and
optionally may include a plurality of hard particles comprising a
hard material. By way of example and not limitation, the second
powder mixture 119 may include a plurality of particles each
comprising any of the alpha (.alpha.) alloys set forth in Table 4.
As additional examples, the second powder mixture 119 may include a
plurality of particles each comprising any of the .alpha.+.beta.
alloys set forth in Table 1, any of the beta (.beta.) alloys set
forth in Table 2, or any of the metastable beta (.beta.) alloys set
forth in Table 3. In some embodiments, the second powder mixture
119 may be substantially similar to the first powder mixture 109
previously described with reference to FIG. 3A, with the exception
of the absence of a plurality of hard particles (e.g., titanium
carbide and/or titanium diboride) in the second powder mixture 119.
Optionally, the powder mixture 119 may further include additives
commonly used when pressing powder mixtures such as, for example,
binders for providing lubrication during pressing and 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.
[0071] The die 116 may include an inner cavity having surfaces
shaped and configured to form at least some surfaces of the second
region 76 of the bit body 72. The plunger 118 may also have
surfaces configured to form or shape at least some of the surfaces
of the second region 76 of the bit body 72. One or more inserts or
displacements 117 may be positioned within the die 116 and used to
define the internal fluid passageways 42. Additional displacements
117 (not shown) may be used to define other topographic features of
the second region 76 of the bit body 72 as necessary.
[0072] The plunger 118 may be advanced into the die 116 at high
force using mechanical or hydraulic equipment or machines to
compact the second powder mixture 119 within the die 116 to form a
second green powder component 120, shown in FIG. 3F. The die 116,
plunger 118, and the second powder mixture 119 optionally may be
heated during the compaction process.
[0073] The second green powder component 120 shown in FIG. 3F may
include a plurality of particles (particles of titanium or
titanium-based alloy matrix material, and optionally, hard
particles comprising a hard material) held together by a binder
material provided in the powder mixture 119 (FIG. 3E), as
previously described. Certain structural features may be machined
in the green powder component 120 as necessary using conventional
machining techniques including, for example, turning techniques,
milling techniques, and drilling techniques. Hand held tools also
may be used to manually form or shape features in or on the green
powder component 120.
[0074] The second green powder component 120 shown in FIG. 3F may
be at least partially sintered. For example, the green powder
component 120 may be partially sintered to provide a second brown
structure 121 shown in FIG. 3G, which has less than a desired final
density. Prior to sintering, the green powder component 120 may be
subjected to moderately elevated temperatures to burn off or remove
any fugitive additives that were included in the powder mixture 119
(FIG. 3E), as previously described.
[0075] Certain structural features may be machined in the second
brown structure 121 as necessary using conventional machining
techniques including, for example, turning techniques, milling
techniques, and drilling techniques. Hand held tools may also be
used to manually form or shape features in or on the brown
structure 121.
[0076] The brown structure 121 shown in FIG. 3G then may be
inserted into the previously formed shaped brown structure 112
shown in FIG. 3D to provide a unitary brown bit body 126 shown in
FIG. 3H. The unitary brown bit body 126 then may be fully sintered
to a desired final density to provide the previously described bit
body 72 shown in FIG. 2. As sintering involves densification and
removal of porosity within a structure, the structure being
sintered will shrink during the sintering process. A structure may
experience linear shrinkage of, for example, between 10% and 20%
during sintering. As a result, dimensional shrinkage must be
considered and accounted for when designing tooling (molds, dies,
etc.) or machining features in structures that are less than fully
sintered.
[0077] In another method, the green powder component 120 shown in
FIG. 3F may be inserted into or assembled with the green powder
component 110 shown in FIG. 3B to form a green bit body. The green
bit body then may be machined as necessary and sintered to a
desired final density. The interfacial surfaces of the green powder
component 110 and the green powder component 120 may be fused or
bonded together during sintering processes. In other methods, the
green bit body may be partially sintered to a brown bit body.
Shaping and machining processes may be performed on the brown bit
body as necessary, and the resulting brown bit body then may be
sintered to a desired final density.
[0078] The material composition of the first region 74 (and
therefore, the composition of the first powder mixture 109 shown in
FIG. 3A) and the material composition of the second region 76 (and
therefore, the composition of the second powder mixture 119 shown
in FIG. 3E) may be selected to exhibit substantially similar
shrinkage during the sintering processes.
[0079] The sintering processes described herein may include
conventional sintering in a vacuum furnace, sintering in a vacuum
furnace followed by a conventional hot isostatic pressing process,
and sintering immediately followed by isostatic pressing at
temperatures near the sintering temperature (often referred to as
sinter-HIP). Furthermore, the sintering processes described herein
may include subliquidus phase sintering. In other words, the
sintering processes may be conducted at temperatures proximate to
but below the liquidus line of the phase diagram for the matrix
material. For example, the sintering processes described herein may
be conducted using a number of different methods known to one of
ordinary skill in the art such as the Rapid Omnidirectional
Compaction (ROC) process, the CERACON.RTM. process, hot isostatic
pressing (HIP), or adaptations of such processes.
[0080] Broadly, and by way of example only, sintering a green
powder compact using the ROC process involves presintering the
green powder compact at a relatively low temperature to only a
sufficient degree to develop sufficient strength to permit handling
of the powder compact. The resulting brown structure is wrapped in
a material such as graphite foil to seal the brown structure. The
wrapped brown structure is placed in a container, which is filled
with particles of a hard, polymer, or glass material having a
substantially lower melting point than that of the matrix material
in the brown structure. The container is heated to the desired
sintering temperature, which is above the melting temperature of
the particles of a ceramic, polymer, or glass material, but below
the liquidus temperature of the matrix material in the brown
structure. The heated container with the molten ceramic, polymer,
or glass material (and the brown structure immersed therein) is
placed in a mechanical or hydraulic press, such as a forging press,
that is used to apply pressure to the molten ceramic or polymer
material. Isostatic pressures within the molten ceramic, polymer,
or glass material facilitate consolidation and sintering of the
brown structure at the elevated temperatures within the container.
The molten ceramic, polymer, or glass material acts to transmit the
pressure and heat to the brown structure. In this manner, the
molten ceramic, polymer, or glass acts as a pressure transmission
medium through which pressure is applied to the structure during
sintering. Subsequent to the release of pressure and cooling, the
sintered structure is then removed from the ceramic, polymer, or
glass material. A more detailed explanation of the ROC process and
suitable equipment for the practice thereof is provided by U.S.
Pat. Nos. 4,094,709, 4,233,720, 4,341,557, 4,526,748, 4,547,337,
4,562,990, 4,596,694, 4,597,730, 4,656,002 4,744,943 and 5,232,522,
the disclosure of each of which patents is incorporated herein by
reference.
[0081] The CERACON.RTM. process, which is similar to the
aforementioned ROC process, may also be adapted for use in the
present invention to fully sinter brown structures to a final
density. In the CERACON.RTM. process, the brown structure is coated
with a ceramic coating such as alumina, zirconium oxide, or chrome
oxide. Other similar, hard, generally inert, protective, removable
coatings may also be used. The coated brown structure is fully
consolidated by transmitting at least substantially isostatic
pressure to the coated brown structure using ceramic particles
instead of a fluid media as in the ROC process. A more detailed
explanation of the CERACON.RTM. process is provided by U.S. Pat.
No. 4,499,048, the disclosure of which patent is incorporated
herein by reference.
[0082] As previously described, the material composition of the
second region 76 of the bit body 72 may be selected to facilitate
the machining operations performing on the second region 76, even
in the fully sintered state. After sintering the unitary brown bit
body 126 shown in FIG. 3H to the desired final density, certain
features may be machined in the fully sintered structure to provide
the bit body 72, which is shown separate from the shank 20 (FIG. 2)
in FIG. 3I. For example, the surfaces 14 of the second region 76 of
the bit body 72 may be machined to provide elements or features for
attaching the shank 20 (FIG. 2) to the bit body 72. By way of
example and not limitation, two grooves 16 may be machined in a
surface 78 of the second region 76 of the bit body 72, as shown in
FIG. 3I. Each groove 16 may have, for example, a semi-circular
cross section. Furthermore, each groove 16 may extend radially
around a portion of the second region 76 of the bit body 72, as
illustrated in FIG. 3J. In this configuration, the surface of the
second region 76 of the bit body 72 within each groove 16 may have
a shape comprising an angular section of a partial toroid. As used
herein, the term "toroid" means a surface generated by a closed
curve (such as a circle) rotating about, but not intersecting or
containing, an axis disposed in a plane that includes the closed
curve. In other embodiments, the surface of the second region 76 of
the bit body 72 within each groove 16 may have a shape that
substantially fat ins a partial cylinder. The two grooves 16 may be
located on substantially opposite sides of the second region 76 of
the bit body 72, as shown in FIG. 3J.
[0083] As described herein, the first region 74 and the second
region 76 of the bit body 72 may be separately formed in the brown
state and assembled together to form a unitary brown structure,
which can then be sintered to a desired final density. In
additional methods of forming the bit body 72, the first region 74
may be formed by pressing a first powder mixture in a die to form a
first green powder component, adding a second powder mixture to the
same die and pressing the second powder mixture within the die
together with the first powder component of the first region 74 to
form a monolithic green bit body. Furthermore, a first powder
mixture and a second powder mixture may be provided in a single die
and simultaneously pressed to form a monolithic green bit body. The
monolithic green bit body then may be machined as necessary and
sintered to a desired final density. In yet other methods, the
monolithic green bit body may be partially sintered to a brown bit
body. Shaping and machining processes may be performed on the brown
bit body as necessary, and the resulting brown bit body then may be
sintered to a desired final density. The monolithic green bit body
may be formed in a single die using two different plungers, such as
the plunger 108 shown in FIG. 3A and the plunger 118 shown in FIG.
3E. Furthermore, additional powder mixtures may be provided as
necessary to provide any desired number of regions within the bit
body 72 having a material composition.
[0084] FIGS. 4A-4C illustrate another method of forming the bit
body 72. Generally, the bit body 72 of the rotary drill bit 70 may
be formed by pressing the previously described first powder mixture
109 (FIG. 3A) and the previously described second powder mixture
119 (FIG. 3E) to form a generally cylindrical monolithic green bit
body 130 or billet, as shown in FIG. 4A. By way of example and not
limitation, the generally cylindrical monolithic green bit body 130
may be formed by substantially simultaneously isostatically
pressing the first powder mixture 109 and the second powder mixture
119 together in a pressure chamber.
[0085] By way of example and not limitation, the first powder
mixture 109 and the second powder mixture 119 may be provided
within a container. The container may include a fluid-tight
deformable member, such as, for example, a substantially
cylindrical bag comprising a deformable polymer material. The
container (with the first powder mixture 109 and the second powder
mixture 119 contained therein) may be provided within a pressure
chamber. A fluid, such as, for example, water, oil, or gas (such
as, for example, air or nitrogen) may be pumped into the pressure
chamber using a pump. The high pressure of the fluid causes the
walls of the deformable member to deform. The pressure may be
transmitted substantially uniformly to the first powder mixture 109
and the second powder mixture 119. The pressure within the pressure
chamber 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 during
isostatic pressing may be greater than about 138 megapascals
(20,000 pounds per square inch). In additional methods, a vacuum
may be provided within the container and a pressure greater than
about 0.1 megapascal (about 15 pounds per square inch), may be
applied to the exterior surfaces of the container (by, for example,
the atmosphere) to compact the first powder mixture 109 and the
second powder mixture 119. Isostatic pressing of the first powder
mixture 109 and the second powder mixture 119 may form the
generally cylindrical monolithic green bit body 130 shown in FIG.
4A, which can be removed from the pressure chamber after
pressing.
[0086] The generally cylindrical monolithic green bit body 130
shown in FIG. 4A may be machined or shaped as necessary. By way of
example and not limitation, the outer diameter of an end of the
generally cylindrical monolithic green bit body 130 may be reduced
to form the shaped monolithic green bit body 132 shown in FIG. 4B.
For example, the generally cylindrical monolithic green bit body
130 may be turned on a lathe to form the shaped monolithic green
bit body 132. Additional machining or shaping of the generally
cylindrical monolithic green bit body 130 may be performed as
necessary or desired. In other methods, the generally cylindrical
monolithic green bit body 130 may be turned on a lathe to ensure
that the monolithic green bit body 130 is substantially cylindrical
without reducing the outer diameter of an end thereof or otherwise
changing the shape of the monolithic green bit body 130.
[0087] The shaped monolithic green bit body 132 shown in FIG. 4B
then may be partially sintered to provide a brown bit body 134
shown in FIG. 4C. The brown bit body 134 then may be machined as
necessary to faun a structure substantially identical to the
previously described shaped unitary brown bit body 126 shown in
FIG. 3H. By way of example and not limitation, the longitudinal
bore 40 and internal fluid passageways 42 (FIG. 3H) may be formed
in the brown bit body 134 (FIG. 4C) by, for example, using a
machining process. A plurality of pockets 36 for PDC cutters 34
also may be machined in the brown bit body 134 (FIG. 4C).
Furthermore, at least one surface 78 (FIG. 3H) that is configured
for attachment of the bit body 72 to the shank 20 may be machined
in the brown bit body 134 (FIG. 4C).
[0088] After the brown bit body 134 shown in FIG. 4C has been
machined to form a structure substantially identical to the shaped
unitary brown bit body 126 shown in FIG. 3H, the structure may be
further sintered to a desired final density and certain additional
features may be machined in the fully sintered structure as
necessary to provide the bit body 72 shown in FIG. 3I, as
previously described.
[0089] In additional embodiments, the bit body 72 may be formed
using a conventional infiltration process. For example, a plurality
of particles each comprising a hard material (e.g., titanium
carbide, titanium diboride, etc.) may be provided in a region of a
cavity of a graphite mold (or a mold formed from any other
refractory material) that is configured to form the first region 74
of the bit body 72. Preform elements or displacements (which may
comprise ceramic components, graphite components, or resin-coated
sand compact components) may be positioned within the mold and used
to define the internal passages 42, cutting element pockets 36,
junk slots 32, and other external or internal topographic features
of the bit body 12. Furthermore, a preform element or displacement
may be positioned in a region of the cavity of the graphite mold
that is configured to form the second region 76 of the bit body
72.
[0090] A titanium or titanium-based alloy matrix material may be
melted, poured into the mold cavity, and caused to infiltrate the
particles comprising hard material to form the first region 74 of
the bit body 72. The mold and partially formed bit body may be
allowed to cool to solidify the molten matrix material. The preform
element or displacement previously positioned in the region of the
cavity of the graphite mold configured to form the second region 76
of the bit body 72 may be removed from the mold cavity, and another
preform element or displacement may be positioned in a region of
the cavity of the graphite mold corresponding to the internal
longitudinal bore 40. The second region 76 of the bit body then may
be formed in a manner substantially similar to that previously
described in relation to the first region 74. If the second region
76 of the bit body 72 is to comprise a titanium or titanium-based
alloy material without any hard phase regions or particles, the
titanium or titanium-based alloy material may simply be melted and
poured into the mold cavity without pre-packing or filling the mold
cavity with hard particles.
[0091] Once the bit body 72 has cooled, the bit body 72 may be
removed from the mold and any displacements may be removed from the
bit body 72. Destruction of the graphite mold may be required to
remove the bit body 72.
[0092] At least a portion of the bit body 72 shown in FIG. 3I may
be subjected to one or more thermal treatment processes (i.e., heat
treated) to refine or tailor the microstructure of a material of
the bit body 72 and impart one or more desired physical properties
(i.e., increased strength, hardness, fracture toughness, etc.) to
the material of the bit body 72, as necessary or desired. By way of
example and not limitation, at least a portion of the bit body 72
may be annealed to increase or otherwise selectively tailor the
fracture toughness of the bit body 72. In general, titanium alloys
may be annealed to increase fracture toughness, ductility at room
temperature, dimensional and thermal stability, and creep
resistance. The time and temperature for any annealing process is
dependent upon the particular titanium alloy being annealed and the
microstructure and physical properties desired to be imparted to
the material, and the general procedures for determining a suitable
annealing time and temperature for imparting such microstructure
and physical properties to the material are within the general
knowledge of those of ordinary skill in the art.
[0093] As another example, at least a portion of the bit body 72
comprising an .alpha.+.beta. alloy, a beta (.beta.) alloy, or a
metastable beta (.beta.) alloy may be solution-treated (ST) or
solution-treated and aged (STA) to refine or tailor the
microstructure of a material of the bit body 72 and impart one or
more desired physical properties (e.g., increased strength) to the
material of the bit body 72, as necessary or desired. In general,
titanium-based alloys may be solution-treated by heating the
titanium-based alloy to a solution temperature proximate (slightly
above or slightly below) the beta transus temperature (e.g.,
between about 690.degree. C. and about 1060.degree. C.) for between
about one-quarter of an hour to about two hours to allow the phases
to equilibrate at the solution temperature. The material is then
quenched (i.e., rapidly cooled) from the solution temperature to
room temperature using air and/or water. Upon quenching, at least
some regions comprising high-temperature beta (.beta.) phase may be
trapped or preserved within the microstructure of the
titanium-based alloy material in a metastable, non-equilibrium
state. Upon aging, at least a portion of these metastable,
non-equilibrium phases may decompose to a stable, equilibrium
phase. Solution-treated titanium-based alloys are aged at
temperatures below the solution temperature, generally between
about 390.degree. C. and about 760.degree. C., for times ranging
from about two hours up to several hundred hours. Again, the time
and temperature for any solution-treating and/or aging process is
dependent upon the particular titanium alloy being treated and the
microstructure and physical properties desired to be imparted to
the material, and the general procedures for determining a suitable
treating time and temperature for imparting such microstructure and
physical properties to the material are within the general
knowledge of those of ordinary skill in the art.
[0094] As titanium alloys are generally susceptible to oxidation,
any thermal treatment process may be carried out in a controlled
inert environment.
[0095] Optionally, at least a portion of an exterior surface of the
bit body 72 may be nitrided before or after the bit body 72 has
been thermally treated as necessary or desired, which may increase
the hardness and/or the wear-resistance of the particle-matrix
composite material 15 at the exposed, formation-engaging surfaces
of the bit body 72. By way of example and not limitation, the bit
body 72 may be nitrided using a plasma nitriding process in a
plasma chamber. The process temperature for conducting plasma
nitriding of titanium and its alloys varies from about 425.degree.
C. to about 725.degree. C., the optimum temperature depending on
the particular material composition and other parameters. Any
titanium oxide at or on the exterior surface of the bit body 72 may
be removed prior to nitriding. By way of example and not
limitation, an exterior surface of the bit body 72 may be nitrided
in an atmosphere comprising a mixture of nitrogen gas and hydrogen
gas (e.g., between about 20% and about 60% by volume nitrogen gas)
at pressures ranging from, for example, a few milipascals to
several kilopascals or more and for a time ranging from, for
example, several minutes to several hours or more.
[0096] In additional methods, selected areas or regions of the
exposed, formation-engaging surfaces of the bit body 72 may be
nitrided using a laser nitriding process. By way of example and not
limitation, an exterior surface of the bit body 72 may be nitrided
by irradiating the surface of the bit body 72 with intense pulsed
ion beam (IPIB) radiation at room temperature, which may allow the
physical properties of the bulk material to remain substantially
unaffected. Such irradiation may be carried out, for example, in an
atmosphere comprising nitrogen gas under vacuum conditions (e.g.,
at pressures of less than about 0.02 pascal).
[0097] Referring again to FIG. 2, the shank 20 may be attached to
the bit body 72 by providing a brazing material 26 such as, for
example, a silver-based or nickel-based metal alloy in the gap
between the shank 20 and the surfaces 14 in the second region 76 of
the bit body 72. As an alternative to brazing, or in addition to
brazing, a weld 24 may be provided around the rotary drill bit 70
on an exterior surface thereof along an interface between the bit
body 72 and the steel shank 20. The brazing material 26 and the
weld 24 may be used to secure the shank 20 to the bit body 72.
[0098] In additional methods, structures or features that provide
mechanical interference may be used in addition to, or instead of,
the brazing material 26 and weld 24 to secure the shank 20 to the
bit body 72. An example of such a method of attaching a shank 20 to
the bit body 72 is described below with reference to FIG. 2 and
FIGS. 5-7. Referring to FIG. 5, two apertures 21 may be provided
through the shank 20, as previously described in relation to FIG.
2. Each aperture 21 may have a size and shape configured to receive
a retaining member 46 (FIG. 2) therein. By way of example and not
limitation, each aperture 21 may have a substantially cylindrical
cross section and may extend through the shank 20 along an axis
L.sub.21, as shown in FIG. 6. The location and orientation of each
aperture 21 in the shank 20 may be such that each axis L.sub.21
lies in a plane that is substantially perpendicular to the
longitudinal axis L.sub.70 of the drill bit 70, but does not
intersect the longitudinal axis L.sub.70 of the drill bit 70.
[0099] When a retaining member 46 is inserted through an aperture
21 of the shank 20 and a groove 16, the retaining member 46 may
abut against a surface of the second region 76 of the bit body 72
within the groove 16 along a line of contact if the groove 16 has a
shape comprising an angular section of a partial toroid, as shown
in FIGS. 3I and 3J. If the groove 16 has a shape that substantially
forms a partial cylinder, however, the retaining member 46 may abut
against an area on the surface of the second region 76 of the bit
body 72 within the groove 16.
[0100] In some embodiments, each retaining member 46 may be secured
to the shank 20. By way of example and not limitation, if each
retaining member 46 includes an elongated, cylindrical rod as shown
in FIG. 2, the ends of each retaining member 46 may be welded to
the shank 20 along the interface between the end of each retaining
member 46 and the shank 20. In additional embodiments, a brazing or
soldering material (not shown) may be provided between the ends of
each retaining member 46 and the shank 20. In still other
embodiments, threads may be provided on an exterior surface of each
end of each retaining member 46 and cooperating threads may be
provided on surfaces of the shank 20 within the apertures 21.
[0101] Referring again to FIG. 2, the brazing material 26 such as,
for example, a silver-based or nickel-based metal alloy may be
provided in the substantially uniform gap between the shank 20 and
the surfaces 14 in the second region 76 of the bit body 72. The
weld 24 may be provided around the rotary drill bit 70 on an
exterior surface thereof along an interface between the bit body 72
and the steel shank 20. The weld 24 and the brazing material 26 may
be used to further secure the shank 20 to the bit body 72. In this
configuration, if the brazing material 26 in the substantially
uniform gap between the shank 20 and the surfaces 14 in the second
region 76 of the bit body 72 and the weld 24 should fail while the
drill bit 70 is located at the bottom of a wellbore during a
drilling operation, the retaining members 46 may prevent
longitudinal separation of the bit body 72 from the shank 20,
thereby preventing loss of the bit body 72 in the wellbore.
[0102] In additional methods of attaching the shank 20 to the bit
body 72, only one retaining member 46 or more than two retaining
members 46 may be used to attach the shank 20 to the bit body 72.
In yet other embodiments, a threaded connection may be provided
between the second region 76 of the bit body 72 and the shank 20.
As the material composition of the second region 76 of the bit body
72 may be selected to facilitate machining thereof even in the
fully sintered state, threads having precise dimensions may be
machined on the second region 76 of the bit body 72. In additional
embodiments, the interface between the shank 20 and the bit body 72
may be substantially tapered. Furthermore, a shrink fit or a press
fit may be provided between the shank 20 and the bit body 72.
[0103] Particle-matrix composite materials used in bit bodies or
earth-boring rotary drill bits conventionally include particles or
regions of tungsten carbide dispersed throughout a copper-based
alloy matrix material. Copper alloys generally exhibit a linear
coefficient of thermal expansion (CTE) of between about 16.0
.mu.m/m.degree. C. and 22.0 .mu.m/m.degree. C. (at room
temperature), tungsten carbide generally exhibits a linear
coefficient of thermal expansion of between about 4.0
.mu.m/m.degree. C. and 7.5 .mu.m/m.degree. C., and conventional
particle-matrix composite materials comprising particles or regions
of tungsten carbide dispersed throughout a copper-based alloy
matrix material generally exhibit a linear coefficient of thermal
expansion of about 12.0 .mu.m/m.degree. C. (as estimated using
Turner's Equation). The graphite molds and preform elements (or
displacements) used in conventional infiltration methods, however,
generally exhibit a linear coefficient of thermal expansion of
between about 1.2 .mu.m/m.degree. C. and 8.2 .mu.m/m.degree. C. As
a result of the disparity in the coefficient of thermal expansion
between the graphite molds and conventional particle-matrix
composite materials, conventional particle-matrix composite bit
bodies formed using infiltration processes may have significant
residual stresses in the particle-matrix composite material after
formation of the bit bodies. These stresses may be rather severe on
areas of the bit body adjacent the graphite mold and/or preform
elements (or displacements), and may lead to premature cracking in
such areas (e.g., areas on or adjacent blades 30 and/or junk slots
32 (FIG. 2), areas adjacent cutter pockets 36 (FIG. 2), areas
adjacent internal fluid passageways 42, etc.). Such cracks may lead
to premature failure of the rotary drill bit.
[0104] Titanium and titanium-based alloy materials generally
exhibit a linear coefficient of thermal expansion of between about
7.6 .mu.m/m.degree. C. and 9.8 .mu.m/m.degree. C., while titanium
carbide exhibits a linear coefficient of thermal expansion of about
7.4 .mu.m/m.degree. C. and titanium diboride exhibits a linear
coefficient of thermal expansion of about 8.2 .mu.m/m.degree. C.
Therefore, particle-matrix composite materials that include a
plurality of titanium carbide and/or titanium diboride particles
dispersed throughout a titanium or titanium-based alloy matrix
material may exhibit a linear coefficient of thermal expansion of
between about 7.5 .mu.m/m.degree. C. and 9.5 .mu.m/m.degree. C. As
a result, the particle-matrix composite materials described herein
may exhibit a linear coefficient of thermal expansion that is
substantially equal to, or less than about double, the linear
coefficient of thermal expansion of a graphite mold (or a mold
comprising any other refractory material) in which a bit body may
be cast using such particle-matrix composite materials. Therefore,
by using the particle-matrix composite materials described herein
to form bit bodies of earth-boring rotary drill bits, the residual
stresses developed in such bit bodies due to mismatch in the
coefficient of thermal expansion between the materials and the
molds may be reduced or eliminated, and the performance of rotary
drill bits comprising such bit bodies may be enhanced relative to
heretofore known drill bits.
[0105] In addition, titanium and titanium-based alloys may exhibit
enhanced corrosion resistance relative to conventional copper and
copper-based alloys that are used in particle-matrix composite
materials for bit bodies of conventional earth-boring rotary drill
bits, which may further enhance the performance of rotary drill
bits comprising a bit body formed from the materials described
herein relative to conventional earth-boring rotary drill bits.
[0106] The bit body 12 previously described herein and shown in
FIG. 1 may be formed using methods substantially similar to any of
those described herein in relation to the bit body 72 shown in FIG.
2 (including infiltration methods as well as powder pressing and
sintering methods).
[0107] In the embodiment shown in FIG. 2, the bit body 72 includes
two distinct regions having material compositions with an
identifiable boundary or interface therebetween. In additional
embodiments, the material composition of the bit body 72 may be
continuously varied between regions within the bit body 72 such
that no boundaries or interfaces between regions are readily
identifiable. In additional embodiments, the bit body 72 may
include more than two regions having material compositions, and the
spatial location of the various regions having material
compositions within the bit body 72 may be varied.
[0108] FIG. 7 illustrates an additional bit body 150 that embodies
teachings of the present invention. The bit body 150 includes a
first region 152 and a second region 154. As best seen in the
cross-sectional view of the bit body 150 shown in FIG. 8, the
interface between the first region 152 and the second region 154
may generally follow the topography of the exterior surface of the
first region 152. For example, the interface may include a
plurality of longitudinally extending ridges 156 and depressions
158 corresponding to the blades 30 and junk slots 32 that may be
provided on and in the exterior surface of the bit body 150. In
such a configuration, blades 30 on the bit body 150 may be less
susceptible to fracture when a torque is applied to a drill bit
comprising the bit body 150 during a drilling operation.
[0109] FIG. 9 illustrates yet another bit body 160 that embodies
teachings of the present invention. The bit body 160 also includes
a first region 162 and a second region 164. The first region 162
may include a longitudinally lower region of the bit body 160, and
the second region 164 may include a longitudinally upper region of
the bit body 160. Furthermore, the interface between the first
region 162 and the second region 164 may include a plurality of
radially extending ridges and depressions (not shown), which may
make the bit body 160 less susceptible to fracture along the
interface when a torque is applied to a drill bit comprising the
bit body 160 during a drilling operation.
[0110] While teachings of the present invention are described
herein in relation to embodiments of concentric earth-boring rotary
drill bits that include fixed cutters, other types of earth-boring
drilling tools such as, for example, core bits, eccentric bits,
bicenter bits, reamers, mills, drag bits, roller cone bits, and
other such structures known in the art may embody teachings of the
present invention and may be formed by methods that embody
teachings of the present invention. Thus, as employed herein, the
term "bits" includes and encompasses all of the foregoing
structures.
[0111] 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
preferred 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. Further, the invention has utility
in drill bits and core bits having different and various bit
profiles as well as cutter types.
* * * * *