U.S. patent application number 12/136456 was filed with the patent office on 2009-12-10 for composite metal, cemented carbide bit construction.
Invention is credited to James L. Christie, John H. Stevens.
Application Number | 20090301788 12/136456 |
Document ID | / |
Family ID | 41399264 |
Filed Date | 2009-12-10 |
United States Patent
Application |
20090301788 |
Kind Code |
A1 |
Stevens; John H. ; et
al. |
December 10, 2009 |
COMPOSITE METAL, CEMENTED CARBIDE BIT CONSTRUCTION
Abstract
A manufacturing method and drill bit having either a preformed
steel powder blank or machined steel core and abrasion and erosion
resistant material components attached thereon.
Inventors: |
Stevens; John H.; (Spring,
TX) ; Christie; James L.; (Lafayette, LA) |
Correspondence
Address: |
TRASKBRITT, P.C.
P.O. BOX 2550
SALT LAKE CITY
UT
84110
US
|
Family ID: |
41399264 |
Appl. No.: |
12/136456 |
Filed: |
June 10, 2008 |
Current U.S.
Class: |
175/374 ;
76/108.2 |
Current CPC
Class: |
C22C 29/06 20130101;
B22F 7/062 20130101; C22C 26/00 20130101; B22F 3/15 20130101; C22C
29/10 20130101; B22F 3/172 20130101; C22C 29/16 20130101; B22F
2005/002 20130101; C22C 1/051 20130101; E21B 10/55 20130101; C22C
29/14 20130101; C22C 2204/00 20130101; B22F 7/08 20130101 |
Class at
Publication: |
175/374 ;
76/108.2 |
International
Class: |
E21B 10/08 20060101
E21B010/08 |
Claims
1. A method of forming a bit body for an earth-boring rotary drill
bit, the method comprising: providing a rotary drill bit body;
providing a green powder component being configured to form a
region of a bit body for attachment to the drill bit body; at least
partially sintering the green unitary structure; and attaching the
finally sintered structure to a portion of the rotary drill bit
body.
2. The method of claim 1, wherein the component comprises a shell
for the rotary drill bit.
3. The method of claim 1, wherein the component comprises a segment
for attachment to a blade of the rotary drill bit.
4. The method of claim 1, wherein the drill bit body comprises a
first material.
5. The method of claim 4, wherein the first material comprises one
of steel or an alloy thereof.
6. The method of claim 4, wherein the green powder component
comprises a second material.
7. The method of claim 6, wherein the first green powder component
is configured to form a crown region of the bit body comprising: a
plurality of particles comprising a matrix material, 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; and a plurality of hard particles
selected 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, Zr, and Cr.
8. The method of claim 1, wherein providing a plurality of green
powder components comprises: providing a powder mixture; and
isostatically pressing the powder mixture.
9. The method of claim 1, wherein at least partially sintering the
green unitary structure comprises: partially sintering the green
unitary structure to form a brown unitary structure; machining at
least one feature in the brown unitary structure; and sintering the
brown unitary structure to a desired final density.
10. A method of forming a bit body for an earth-boring rotary drill
bit, the method comprising: providing a rotary drill bit body;
providing a green powder component configured to form one of a
crown region of a rotary drill bit body or a segment for attachment
to the rotary drill bit body; at least partially sintering the
green powder component to form a brown component; assembling the
brown component to form a brown unitary structure; and sintering
the brown unitary structure to a final density.
11. The method of claim 10, wherein providing a green powder
component comprises: providing a first green powder component
having a first composition.
12. The method of claim 10, wherein sintering the brown unitary
structure to a final density comprises subliquidus phase
sintering.
13. The method of claim 10, wherein sintering the brown unitary
structure to a final density comprises subjecting the brown unitary
structure to elevated temperatures in a vacuum furnace.
14. A method of forming an earth-boring rotary drill bit, the
method comprising: providing a bit body substantially formed of a
steel composite material having a shank configured for attachment
to a drill string; providing another portion for attachment to the
bit body comprising: providing a powder mixture comprising: a
plurality of hard particles selected 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, Zr, and Cr; and a plurality of particles comprising a matrix
material, 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; pressing the
powder mixture to form a green another portion for attachment to
the bit body; and at least partially sintering the green another
portion for attachment to the bit body; and attaching the another
portion to the bit body.
15. The method of claim 14, wherein the matrix material is selected
from the group consisting of cobalt-based alloys and cobalt and
nickel-based alloys.
16. The method of claim 14, wherein providing another portion for
attachment to the bit body further comprises: machining at least
one feature of the another portion.
17. The method of claim 16, wherein machining at least one feature
in the another portion comprises machining at least one of a fluid
passageway, a junk slot, and a cutter pocket in the another
portion.
18. The method of claim 14, wherein at least partially sintering
the green another portion for attachment to the bit body comprises:
partially sintering the green another portion to form a brown
another portion; machining at least one feature in the brown
another portion; and sintering the brown another portion to a final
density.
19. The method of claim 18, wherein machining at least one feature
in the brown another portion comprises machining at least one of a
fluid passageway, a junk slot, and a cutter pocket in the brown
another portion.
20. The method of claim 18, wherein sintering the brown another
portion to a final density comprises subliquidus phase
sintering.
21. The method of claim 18, wherein sintering the brown another
portion to a final density comprises subjecting the brown another
portion to elevated temperatures in a vacuum furnace.
22. The method of claim 21, wherein sintering the brown another
portion to a final density further comprises subjecting the brown
another portion to substantially isostatic pressure after
subjecting the brown bit body to elevated temperatures in a vacuum
furnace.
23. The method of claim 14, wherein pressing the powder mixture
comprises pressing the powder mixture with substantially isostatic
pressure.
24. The method of claim 23, wherein pressing the powder mixture
with substantially isostatic pressure comprises pressing the powder
mixture with a liquid.
25. The method of claim 23, wherein pressing the powder mixture
with substantially isostatic pressure comprises pressing the powder
mixture with substantially isostatic pressure greater than about 35
megapascals (about 5,000 pounds per square inch).
26. The method of claim 23, wherein pressing the powder mixture
comprises: providing the powder mixture in a bag comprising a
polymer material; and applying substantially isostatic pressure to
exterior surfaces of the bag.
27. The method of claim 14, wherein providing a powder mixture
comprises providing a plurality of -400 ASTM mesh tungsten carbide
particles, the plurality of tungsten carbide particles comprising
between about 60% and about 95% by weight of the powder
mixture.
28. The method of claim 14, providing a powder mixture comprises
providing a plurality of tungsten carbide particles having an
average diameter in a range extending from about 0.5 microns to
about 20 microns, the plurality of tungsten carbide particles
comprising between about 75% and about 85% by weight of the powder
mixture; and providing a plurality of particles comprising the
matrix material.
29. The method of claim 28, wherein providing a mixture comprises:
providing a plurality of tungsten carbide particles having an
average diameter in a range extending from about 0.5 microns to
about 20 microns, the plurality of tungsten carbide particles
comprising between about 65% and about 70% by weight of the powder
mixture; and providing a plurality of particles comprising the
matrix material.
30. The method of claim 14, further comprising applying a
hardfacing material to a surface of one of the bit body and the
another portion.
31. The method of claim 30, wherein applying a hardfacing material
comprises one of flame spraying the hardfacing material, cold
spraying the hardfacing material, oxy-acetylene welding (OA)
material, atomic hydrogen welding (AHW) material, and plasma
transfer arc welding (PTAW) material onto the surface of one of the
bit body and the another portion.
32. The method of claim 31, wherein applying a hardfacing material
comprises: applying a fabric comprising tungsten carbide to the
surface of one of the bit body and the another portion; and
infusing molten matrix material into the fabric comprising tungsten
carbide.
33. The method of claim 14, wherein the another portion comprises
one of a shell for the bit body and a segment portion for the bit
body.
34. A drill bit comprising: a body having at least one blade
comprising a first material; and a shell formed of a second
material different than the first material attached to the
body.
35. The drill bit of claim 34, wherein the shell comprises: a
powder mixture comprising: a plurality of hard particles selected
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, Zr, and Cr; and a plurality of particles
comprising a matrix material, 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.
36. The drill bit of claim 35, wherein the matrix material is
selected from the group consisting of cobalt-based alloys and
cobalt and nickel-based alloys.
37. The drill bit of claim 36, wherein providing a powder mixture
comprises providing a plurality of -400 ASTM mesh tungsten carbide
particles, the plurality of tungsten carbide particles comprising
between about 60% and about 95% by weight of the powder
mixture.
38. The method of claim 36, wherein the powder mixture comprises: a
plurality of tungsten carbide particles having an average diameter
in a range extending from about 0.5 microns to about 20 microns,
the plurality of tungsten carbide particles comprising between
about 75% and about 85% by weight of the powder mixture.
39. A drill bit comprising: a body having at least one blade having
a front face, an edge, and a rear face comprising a first material
having at least one aperture formed in a portion thereof; and a
segment formed of a second material different than the first
material attached to a portion of the blade of the body.
40. The drill bit of claim 39, wherein the segment includes a
protrusion located in a portion of the at least one aperture of the
blade.
41. The drill bit of claim 39, wherein the segment extends around a
portion of the front face, a portion of the edge, and a portion of
the rear face of the blade.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates generally to a method of
manufacturing drill bits and other drilling-related structures
generally used for drilling subterranean formations, and more
specifically to a method of manufacturing a drill bit or
drilling-related structure having a porous sintered steel powder
core and a powdered tungsten carbide (WC) shell commonly
infiltrated with other metals binder having cutter segments thereon
or a sintered powder tungsten carbide (WC) core with other metals
having cutter segments thereon. In a preferred embodiment, a
sintered, preformed blank is formed and placed in a mold configured
as a bit or other drilling-related structure, the preformed blank
being sized to provide space between the blank and the mold wall to
accommodate a layer of WC powder therebetween. Separately, cutter
segments are formed having cutters thereon which are attached to
the tungsten carbide shell or to the tungsten carbide bit body.
[0003] 2. State of the Art
[0004] A typical rotary drill bit includes a bit body secured to a
steel shank having a threaded pin connection for attaching the bit
body to a drill string, and a crown comprising that part of the bit
fitted with cutting structures for cutting into an earth formation.
Generally, if the bit is a fixed-cutter or so-called "drag" bit,
the cutting structures include a series of cutting elements formed
at least in part of a super-abrasive material, such as
polycrystalline diamond. The bit body is generally formed of steel,
or a matrix of hard particulate material such as tungsten carbide
(WC) infiltrated with a binder, generally of copper alloy.
[0005] In the case of steel body bits, the bit body is typically
machined from round stock to the desired shape. Internal
watercourses for delivery of drilling fluid to the bit face and
topographical features defined at precise locations on the bit face
may be machined into the bit body using a computer-controlled
five-axis machine tool. Hardfacing for resisting abrasion during
drilling is usually applied to the bit face and to other critical
areas of the bit exterior, and cutting elements are secured to the
bit face, generally by inserting the proximal ends of studs, on
which the cutting elements are mounted, into apertures bored in the
bit face. The end of the bit body opposite the face is then
threaded, made up and welded to the bit shank.
[0006] In the case of a matrix-type bit body, it is conventional to
employ a preformed, so-called bit "blank" of steel or other
suitable material for later attachment to the shank, or threaded
end of the bit body matrix. The blank may be merely cylindrically
tubular, or may be fairly complex in configuration and include
protrusions corresponding to blades, wings or other features on and
extending from the bit face. Other preformed elements or
displacements comprised of cast resin-coated sand, or in some
instances graphite may be employed to define watercourses and
passages for delivery of drilling fluid to and away from the bit
face, well as cutting element sockets, ridges, lands, nozzle
displacements, junk slots and other external topographic features
of the bit. The blank and other displacements are placed at
appropriate locations and orientations in the mold used to cast the
bit body. The blank is bonded to the matrix upon cooling of the bit
body after infiltration of the tungsten carbide with the matrix
alloy in a furnace. The other displacements are removed once the
matrix has cooled. The upper end of the blank is then threaded,
made up with a matingly threaded shank, and the two are welded
together. The cutting elements (typically diamond, and most often a
synthetic polycrystalline diamond compact or PDC) may be bonded to
the bit face during furnacing of the bit body if thermally stable
PDC's, commonly termed TSP's (Thermally Stable Products) are
employed, or may be subsequently bonded thereto, usually by brazing
or mechanical affixation.
[0007] As may be readily appreciated from the foregoing
description, the process of fabricating a matrix-type drill bit is
a somewhat costly, complex multi-step process requiring separate
fabrication of an intermediate product (the mold) before the end
product (the bit) can be cast. Moreover, the blanks and preforms
employed must be individually designed and fabricated.
[0008] The mold used to cast a matrix body is typically machined
from a cylindrical graphite element. For many years, bit molds were
machined to a general bit profile, and the individual bit face
topography defined in reverse in the mold by skilled technicians
employing the aforementioned preforms and wielding dental-type
drills and other fine sculpting tools. In more recent years, many
details may be machined in a mold using a computer controlled
five-axis machine tool.
[0009] Both batch and conveyor-type continuous furnaces, induction
heating coils, and other heating methods known in the art may be
used to supply the heat necessary for sintering and or infiltrating
to occur. It is well recognized in the art to use sintering
techniques to sinter and forge mixtures of cobalt powder and
tungsten carbide to form inserts for rock-cutting bits, such as the
method disclosed in U.S. Pat. No. 4,484,644 to Cook et al. It has
also been recognized in the art to replace at least a portion of
the hard metal material (WC) of a typical bit with a tougher, more
ductile displacement material, such as iron, steel, or alloys
thereof. As described in U.S. Pat. No. 5,090,491 to Tibbitts et
al., it is desirable to substitute a less expensive displacement
material (such as steel at about 50 cents per pound) for the more
expensive hard metals like tungsten carbide (at about ten dollars
per pound) to provide a finished bit with improved toughness and
ductility as well as impact strength. However, this reference
provides that the displacement material should preferably be a mesh
size of at least 400 mesh (approximately 0.001 inches) and also
states that very fine powdered materials (i.e., less than 0.001
inches in diameter) such as iron may sinter and shrink during
fabrication; it being undesirable for the powder to shrink
substantially during the heating process. Likewise, in GB 1,572,543
to Holden, the use of relatively inexpensive materials to provide
the metal matrix of a bit, such as iron powder bonded with a
copper-based alloy, is disclosed. Nowhere, however, do any of these
references suggest that a powdered steel blank be sintered or
otherwise preformed, then subsequently infiltrated along with a
layer of tungsten carbide powder to form a bit or drilling-related
structure.
[0010] It is known in the art that although hard, the ductility of
cemented hard-carbide articles are almost always inferior to those
obtained by casting or forging steel. Thus, it would be
advantageous to provide a method of manufacturing a bit or other
drilling-related structure that is a relatively simple process and
that reduces the cost of producing the structure by replacing a
significant amount of the bit matrix material of a typical drilling
structure with a sintered steel powder blank without sacrificing
the bit's resistance to erosion and abrasion. Moreover, it would be
advantageous to provide such a drilling structure that has improved
toughness and impact strength over similar structures manufactured
by prior art methods.
SUMMARY OF THE INVENTION
[0011] A manufacturing method and drill bit having either a
preformed steel powder blank or machined steel core and abrasion
and erosion resistant material components attached thereon.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The features and advantages of the present invention can be
more readily understood with reference to the following detailed
description of the preferred embodiments, taken in conjunction with
the accompanying drawings wherein:
[0013] FIG. 1A is a partially cross-sectioned schematic view of a
first embodiment of a drill bit manufactured in accordance with the
present invention;
[0014] FIG. 1B is a partially cross-sectioned schematic view of a
second embodiment of a drill bit manufactured in accordance with
the present invention;
[0015] FIGS. 2A-2E illustrate a method of forming a shell for the
bit body of the earth-boring rotary drill bit shown in FIG. 1A or
1B;
[0016] FIG. 3A is a partially cross-sectioned schematic view of
another embodiment of a drill bit manufactured in accordance with
the present invention having segments on the blades;
[0017] FIG. 3B is a partially cross-sectioned schematic view of
another embodiment of a drill bit manufactured in accordance with
the present invention having segments on the blades;
[0018] FIG. 4 is a portion of a segment on a blade of the drill
bit;
[0019] FIG. 5 is a portion of a segment on a blade of the drill
bit; and
[0020] FIG. 6 is a partially cross-sections schematic view of
another embodiment of a drill bit manufactured in accordance with
the present invention having segments and or a shell on the
blades.
DETAILED DESCRIPTION OF THE INVENTION
[0021] A drill bit 10 manufactured in accordance with the present
invention is illustrated in FIG. 1A. The drill bit 10 has a typical
rotary drag bit configuration and is generally comprised of a bit
body 12 including a plurality of longitudinally extending blades 14
defining junk slots 16 between the blades 14. Each blade 14 defines
a leading or cutting face 18 that extends from proximate the center
of the bit face around the distal end 15 of the drill bit 10, and
includes a plurality of cutting elements 20 oriented to cut into a
subterranean formation upon rotation of the drill bit 10. The
cutting elements 20 are secured to and supported by the blades 14.
Between the uppermost of the cutting elements 20 and the top edge
21 of the blade 14, each blade 14 defines a longitudinally and
radially extending gage portion 22 that corresponds to
approximately the largest-diameter-portion of the drill bit 10 and,
thus is typically only slightly smaller than the diameter of the
hole to be drilled by cutting elements 20 of the bit 10. The
proximal end 23 of the bit 10 includes a threaded portion or pin 25
to threadedly attach the drill bit 10 to a drill collar or downhole
motor, as is known in the art. Preferably, the threaded pin portion
25 may be machined directly into the proximal end 23 of the
combination shank and blank 34 that is attached and formed into the
body 12 of the drill bit 10.
[0022] As further illustrated by the cut-away portion of FIG. 1A,
the bit 10 is further comprised of either a machine steel core or a
porous sintered blank or core 26 comprised of steel or other metal
interlocked with the blank 34, formed of any suitable material,
such as steel, titanium, tungsten carbide (WC), etc., and a shell
of abrasion-resistant material 28, such as tungsten carbide (WC),
infiltrated with a common metal to form a matrix of tungsten
carbide and the metal. In addition, the plenum 29 longitudinally
extend from the proximal end 23 to the distal end 15 or crown end
15, substantially through the blank 34 and core 26, terminating at
shell 28. As illustrated in FIG. 1B, the core 26' may have a
topographical exterior surface configuration 30 substantially
similar to the topography 32 of a completed bit 10', but smaller in
size, or be different such that the shell 28 occupies a larger
volume of the bit 10 (see FIG. 1A). Thus, except for the detailed
topography of and surrounding the cutting elements 20, the core 26'
generally may follow the contour of the drill bit 10' defined by
its surface topography 32. This similarity in shape between the
core 26' and the topography 32 is a result of a preferred bit
manufacturing method of the present invention. Moreover, the plenum
29' may only extend partially through the core 26' such that any
waterways connecting the plenum 29' to the nozzle ports 62 and 64
must extend through material of both the core 26' and shell
28'.
[0023] The cutters 20 may be bonded to the blades 14 by brazing,
mechanical affixation, or adhesive affixation. Alternatively, the
cutters 20 may be provided within the mold and bonded to the blades
14 of the shell 28 during infiltration or furnacing of the shell 28
if thermally stable synthetic diamonds, or natural diamonds, are
employed.
[0024] 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.
[0025] The term "green" as used herein means unsintered.
[0026] The term "green bit shell" or "green segment" 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 shell 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 shell body" or "brown segment" 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 shell bodies
may be formed by, for example, partially sintering a green shell
body.
[0029] 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.
[0030] 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.
[0031] 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 having different
material compositions.
[0032] 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.
[0033] The particle-matrix composite material of the shell 28 may
include a plurality of hard particles randomly dispersed throughout
a matrix 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, titanium carbide (TiC),
tantalum carbide (TaC), titanium diboride (TiB.sub.2), chromium
carbides, titanium nitride (TiN), aluminium oxide
(Al.sub.2O.sub.3), aluminium nitride (AlN), 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.
[0034] The matrix material of the particle-matrix composite
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, Hadfield manganese 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 closely matches that of the hard particles
used in the particular particle-matrix composite 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).
[0035] In the present invention, the particle-matrix composite
material may include a plurality of -400 ASTM (American Society for
Testing and Materials) mesh tungsten carbide particles as the hard
particle component of the particle-matrix composite material. 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 forming another component of the
particle-matrix composite 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 particle-matrix composite
material, and the matrix material may comprise between about 5% and
about 40% by weight of the particle-matrix composite material. More
particularly, the tungsten carbide particles may comprise between
about 70% and about 80% by weight of the particle-matrix composite
material, and the matrix material may comprise between about 20%
and about 30% by weight of the particle-matrix composite
material.
[0036] In another embodiment of the present invention, the
particle-matrix composite material may include a plurality of -635
ASTM mesh tungsten carbide particles as the hard particle component
of the particle-matrix composite material. 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 forming
another component of the particle-matrix composite 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 particle-matrix composite material, and the matrix
material may comprise between about 5% and about 40% by weight of
the particle-matrix composite material.
[0037] FIGS. 2A-2E illustrate a method of fonning the shell 28,
which is substantially formed from and composed of a
particle-matrix composite material. The method generally includes
providing a powder mixture, pressing the powder mixture to form a
green body, and at least partially sintering the powder
mixture.
[0038] Referring to FIG. 2A, a powder mixture 78, which forms the
particle-matrix composite material that includes a hard particle
component and a matrix material component, may be pressed with
substantially isostatic pressure within a mold or container 80. The
powder mixture 78 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 78 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.
[0039] The container 80 may include a fluid-tight deformable member
82. For example, the fluid-tight deformable member 82 may be a
substantially cylindrical bag comprising a deformable polymer
material. The container 80 may further include a sealing plate 84,
which may be substantially rigid. The deformable member 82 may be
formed from, for example, an elastomer such as rubber, neoprene,
silicone, or polyurethane. The deformable member 82 may be filled
with the powder mixture 78 and vibrated to provide a uniform
distribution of the powder mixture 78 within the deformable member
82. At least one displacement or insert 86 may be provided within
the deformable member 82 for defining features of the bit body 52
such as, for example, the longitudinal bore 40 (FIG. 2).
Alternatively, the insert 86 may not be used and the longitudinal
bore 40 may be formed using a conventional machining process during
subsequent processes. The sealing plate 84 then may be attached or
bonded to the deformable member 82 providing a fluid-tight seal
therebetween.
[0040] The container 80 (with the powder mixture 78 and any desired
inserts 86 contained therein) may be provided within a pressure
chamber 90. A removable cover 91 may be used to provide access to
the interior of the pressure chamber 90. A fluid (which may be
substantially incompressible) such as, for example, water, oil, or
gas (such as, for example, air or nitrogen) is pumped into the
pressure chamber 90 through an opening 92 at high pressures using a
pump (not shown). The high pressure of the fluid causes the walls
of the deformable member 82 to deform. The fluid pressure may be
transmitted substantially uniformly to the powder mixture 78. The
pressure within the pressure chamber 90 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 90 during isostatic pressing may be greater than about 138
megapascals (20,000 pounds per square inch). In alternative
methods, a vacuum may be provided within the container 80 and a
pressure greater than about 0.1 megapascals (about 15 pounds per
square inch) may be applied to the exterior surfaces of the
container (by, for example, the atmosphere) to compact the powder
mixture 78. Isostatic pressing of the powder mixture 78 may form a
green powder component or green shell body 94 shown in FIG. 3B,
which can be removed from the pressure chamber 90 and container 80
after pressing.
[0041] In an alternative method of pressing the powder mixture 78
to form the green shell body 94 shown in FIG. 2B, the powder
mixture 78 may be uniaxially pressed in a mold or die (not shown)
using a mechanically or hydraulically actuated plunger by methods
that are known to those of ordinary skill in the art of powder
processing.
[0042] The green shell body 94 shown in FIG. 2B may include a
plurality of particles (hard particles and particles of matrix
material forming the particle-matrix composite material) held
together by a binder material provided in the powder mixture 78
(FIG. 2A), as previously described. Certain structural features may
be machined in the green bit body 94 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 shell
body 94. By way of example and not limitation, blades 14, junk
slots 16 (FIGS. 1A, 1B), and any surfaces may be machined or
otherwise formed in the green shell body 94 to form a shaped green
shell body 98 shown in FIG. 2C.
[0043] The shaped green shell body 98 shown in FIG. 2C may be at
least partially sintered to provide a brown bit body 102 shown in
FIG. 2D, which has less than a desired final density. Prior to
partially sintering the shaped green bit body 98, the shaped green
bit body 98 may be subjected to moderately elevated temperatures
and pressures to burn off or remove any fugitive additives of any
binder used that were included in the powder mixture 78 (FIG. 2A),
as previously described. Furthermore, the shaped green bit body 98
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 temperatures of about 500.degree. C.
[0044] The brown shell body 102 may be substantially machinable due
to the remaining porosity therein. Certain structural features may
be machined in the brown shell body 102 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 brown
shell body 102. Tools that include superhard coatings or inserts
may be used to facilitate machining of the brown shell body 102.
Additionally, material coatings may be applied to surfaces of the
brown shell body 102 that are to be machined to reduce chipping of
the brown bit body 102. Such coatings may include a suitable
fixative material or other suitable polymer materials or their
like.
[0045] By way of example and not limitation, internal fluid
passageways 29, cutter pockets 36 and blades 14 (FIGS. 1A, 1B) may
be machined or otherwise formed in the brown bit body 102 to form a
shaped brown shell body 106 shown in FIG. 2E. Furthermore, if the
drill bit 10 is to include a plurality of cutters integrally formed
with the shell 28, the cutters may be positioned within the cutter
pockets 36 formed in the brown shell body 102. Upon subsequent
sintering of the brown bit body 102, the cutters may become bonded
to and integrally formed with the shell body 52.
[0046] The shaped brown bit body 106 shown in FIG. 2E then may be
fully sintered to a desired final density to provide the previously
described shell 28 shown in FIG. 1A or FIG. 1B. As any sintering
involves densification and removal of porosity within a structure,
the structure being sintered will shrink during the sintering
process. In an un-infiltrated structure, a structure may experience
linear shrinkage of between 10% and 20% during sintering from a
green state to a desired final density. 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.
[0047] During all sintering and partial sintering processes,
refractory structures or displacements (not shown) may be used to
support at least portions of the bit body during the sintering
process to maintain desired shapes and dimensions during the
densification process. Such displacements may be used, for example,
to maintain consistency in the size and geometry of the cutter
pockets 36 and the internal fluid passageways 42 during the
sintering process. Such refractory structures may be formed from,
for example, graphite, silica, or alumina. The use of alumina
displacements instead of graphite displacements may be desirable as
alumina may be relatively less reactive than graphite, thereby
minimizing atomic diffusion during sintering. Additionally,
coatings such as alumina, boron nitride, aluminum nitride, or other
commercially available materials may be applied to the refractory
structures to prevent carbon or other atoms in the refractory
structures from diffusing into the bit body during
densification.
[0048] In alternative methods, the green shell body 94 shown in
FIG. 2B may be partially sintered to form a brown bit body without
prior machining, and all necessary machining may be performed on
the brown shell body prior to infiltrating the brown shell body and
fully sintering the brown bit body to a desired final density.
Alternatively, all necessary machining may be performed on the
green bit body 94 shown in FIG. 2B, which then may be infiltrated
and fully sintered to a desired final density.
[0049] 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 forming a portion of the particle-matrix composite
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.TM. process, hot isostatic
pressing (HIP), or adaptations of such processes.
[0050] 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 ceramic, 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.
[0051] The Ceracon.TM. 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.TM. 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.TM. process is provided by U.S. Pat. No.
4,499,048, the disclosure of which patent is incorporated herein by
reference.
[0052] Furthermore, in embodiments of the invention in which
tungsten carbide is used in a particle-matrix composite bit body,
the sintering processes described herein also may include a carbon
control cycle tailored to improve the stoichiometry of the tungsten
carbide material. By way of example and not limitation, if the
tungsten carbide material includes WC, the sintering processes
described herein may include subjecting the tungsten carbide
material to a gaseous mixture including hydrogen and methane at
elevated temperatures. For example, the tungsten carbide material
may be subjected to a flow of gases including hydrogen and methane
at a temperature of about 1,000.degree. C.
[0053] After final sintering of the shell 28, the shell 28 is
attached to the core 26 using any suitable bonding process, such as
brazing, individual fasteners, etc.
[0054] As illustrated in FIGS. 3A and 3B, the drill bit 10 includes
the cutters 20 mounted on segments 14' which are attached to the
blades 14. The segments 14' are formed in the same manner as the
shell 28 described hereinbefore. The segments 14' may be formed of
any desired length for attachment to a blade 14, such as from the
gage of the drill bit through any length of a blade 14. The
segments 14' are formed of particle-matrix composite material which
may include a plurality of hard particles randomly dispersed
throughout a matrix 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, titanium
carbide (TiC), tantalum carbide (TaC), titanium diboride
(TiB.sub.2), chromium carbides, titanium nitride (TiN), aluminium
oxide (Al.sub.2O.sub.3), aluminium nitride (AIN), and silicon
carbide (SiC). Furthermore, combinations of different bard
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.
[0055] The matrix material of the particle-matrix composite
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, Hadfield manganese 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 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 closely matches that of the hard particles used in the
particular particle-matrix composite 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).
[0056] In the present invention, the particle-matrix composite
material may include a plurality of -400 ASTM (American Society for
Testing and Materials) mesh tungsten carbide particles as the hard
particle component of the particle-matrix composite material. 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 forming another component of the
particle-matrix composite 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 particle-matrix composite
material, and the matrix material may comprise between about 5% and
about 40% by weight of the particle-matrix composite material. More
particularly, the tungsten carbide particles may comprise between
about 70% and about 80% by weight of the particle-matrix composite
material, and the matrix material may comprise between about 20%
and about 30% by weight of the particle-matrix composite
material.
[0057] Alternately, the particle-matrix composite material may
include a plurality of -635 ASTM mesh tungsten carbide particles as
the hard particle component of the particle-matrix composite
material. 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 forming another component of the
particle-matrix composite 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 particle-matrix
composite material, and the matrix material may comprise between
about 5% and about 40% by weight of the particle-matrix composite
material.
[0058] The segments 14' are formed in the same manner as the
process for forming the shell hereinbefore and illustrated in FIGS.
2A-2E. Similarly, the cutters 20 are attached to the segments 14'
as described hereinbefore with respect to the shell 28.
[0059] In FIG. 4, the segments 14' include one or more protrusions
14'' extending therefrom to mate with recesses formed in the blades
14 to provide an accurate location of the segment on the blade 14.
The protrusions 14'' may extend from a side and the back of a
segment to provide any desired number of locations for the segment
14'' on a blade 14. The segment 14' is attached to a blade 14 in
any suitable manner, such as brazing, fasteners, etc. In addition
to providing a structure to locate the segment 14' on a blade 14,
the protrusions 14'' provide additional surface area to secure the
segment 14' to a blade 14 when the segment 14' is attached to the
blade 14 by brazing a similar attachment process. The protrusions
14'' may be of any desired suitable geometric shape and
dimension.
[0060] As illustrated in FIG. 5, the segment 14' may extend around
the front face, outer edge, and back face of a portion of a blade
14 of the drill bit 10. In this manner, the blade 14 of the drill
bit 10 is protected on all three sides thereof by the segment 14'
which is constructed of material having a higher abrasion
resistance than that of the blade 14. The segment 14' may be
attached to the blade 14 by any suitable attachment process, such
as brazing, fasteners, etc.
[0061] Illustrated in drawing FIG. 6, the segments 14', although
the segments 14' can be formed as a shell such as shell 106
described herein, and blank 34 are illustrated in a in a pressure
chamber 90 such as described hereinbefore. The blank 34 and
segments 14' are supported on suitable inserts 86 with a
particle-matrix material powder mixture 78, such as described
herein, filling the space in the mold or container 80, such as
described herein, between the mold 80 and segments 14' and blank
34. A fluid (which may be substantially incompressible) such as,
for example, water, oil, or gas (such as, for example, air or
nitrogen) is pumped into the pressure chamber 90 through an opening
92 at high pressures using a pump (not shown). The high pressure of
the fluid causes the walls of the deformable member 82 to deform.
The fluid pressure may be transmitted substantially uniformly to
the powder mixture 78. The pressure within the pressure chamber 90
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 90 during isostatic pressing
may be greater than about 138 megapascals (20,000 pounds per square
inch). In alternative methods, a vacuum may be provided within the
container 80 and a pressure greater than about 0.1 megapascals
(about 15 pounds per square inch) may be applied to the exterior
surfaces of the container (by, for example, the atmosphere) to
compact the powder mixture 78. Isostatic pressing of the powder
mixture 78 may form a green powder component or green shell body,
such as green shell body 94 described herein, shown in FIG. 3B,
which can be removed from the pressure chamber 90 and container 80
after pressing.
[0062] The green bit body formed into a green bit blank 34, such as
generally like green shell body 94 shown in FIG. 2B and FIG. 1B,
may include a plurality of particles (hard particles and particles
of matrix material forming the particle-matrix composite material)
held together by a binder material provided in the powder mixture
78 (FIG. 2A), as previously described. Certain structural features
may be machined in the green bit body 94 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
shell body. By way of example and not limitation, blades 14, junk
slots 16 (FIGS. 1A, 1B), and any surfaces may be machined or
otherwise formed in the green shell body to form a shaped green
shell body, generally such as green shell body 98 shown in FIG.
2C.
[0063] The shaped green bit body, generally such as green shell
body 98 shown in FIG. 2C may be at least partially sintered to
provide a brown bit body, generally such as brown bit body 102
shown in FIG. 2D, which has less than a desired final density.
Prior to partially sintering the shaped green bit body, the shaped
green bit body may be subjected to moderately elevated temperatures
and pressures to burn off or remove any fugitive additives of any
binder used that were included in the powder mixture 78 (FIG. 2A),
as previously described. Furthermore, the shaped green bit body 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 temperatures of about 500.degree. C.
[0064] The brown shell body, such as brown body 102 described
herein, may be substantially machinable due to the remaining
porosity therein. Certain structural features may be machined in
the brown shell body 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 brown shell body. Tools that
include superhard coatings or inserts may be used to facilitate
machining of the brown shell body. Additionally, material coatings
may be applied to surfaces of the brown shell body that are to be
machined to reduce chipping of the brown bit body. Such coatings
may include a suitable fixative material or other suitable polymer
materials or their like.
[0065] By way of example and not limitation, internal fluid
passageways 29 and cutter pockets 36 (FIGS. 1A, 1B) may be machined
or otherwise formed in the brown bit body to form a shaped brown
bit body. If the drill bit 10 is to include additional cutters or
wear knots, the cutters and wear knots may be positioned within the
cutter pockets formed in the brown bit body. Upon subsequent
sintering of the brown bit body, the cutters may become bonded to
and integrally formed with the bit body.
[0066] The shaped brown bit body then may be fully sintered to a
desired final density. As any sintering involves densification and
removal of porosity within a structure, the structure being
sintered will shrink during the sintering process. In an
un-infiltrated structure, a structure may experience linear
shrinkage of between 10% and 20% during sintering from a green
state to a desired final density. 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.
[0067] During all sintering and partial sintering processes,
refractory structures or displacements (not shown) may be used to
support at least portions of the bit body during the sintering
process to maintain desired shapes and dimensions during the
densification process. Such displacements may be used, for example,
to maintain consistency in the size and geometry of the cutter
pockets 36 and the internal fluid passageways 42 during the
sintering process. Such refractory structures may be formed from,
for example, graphite, silica, or alumina. The use of alumina
displacements instead of graphite displacements may be desirable as
alumina may be relatively less reactive than graphite, thereby
minimizing atomic diffusion during sintering. Additionally,
coatings such as alumina, boron nitride, aluminum nitride, or other
commercially available materials may be applied to the refractory
structures to prevent carbon or other atoms in the refractory
structures from diffusing into the bit body during
densification.
[0068] In alternative methods, the green bit body may be partially
sintered to form a brown bit body without prior machining, and all
necessary machining may be performed on the brown shell body prior
to infiltrating the brown bit body and fully sintering the brown
bit body to a desired final density. Alternatively, all necessary
machining may be performed on the green bit body 94 shown in FIG.
2B, which then may be infiltrated and fully sintered to a desired
final density.
[0069] 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 forming a portion of the particle-matrix composite
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.TM. process, hot isostatic
pressing (HIP), or adaptations of such processes.
[0070] While teachings of the present invention are described
herein in relation to embodiments of 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.
[0071] 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.
* * * * *