U.S. patent application number 12/687718 was filed with the patent office on 2010-08-05 for matrix drill bit with dual surface compositions and methods of manufacture.
This patent application is currently assigned to HALLIBURTON ENERGY SERVICES, INC.. Invention is credited to Jay S. Bird, William H. Lind.
Application Number | 20100193254 12/687718 |
Document ID | / |
Family ID | 42084243 |
Filed Date | 2010-08-05 |
United States Patent
Application |
20100193254 |
Kind Code |
A1 |
Lind; William H. ; et
al. |
August 5, 2010 |
Matrix Drill Bit with Dual Surface Compositions and Methods of
Manufacture
Abstract
Matrix drill bits and other downhole tools may be formed with
one or more layers of hard materials disposed on exterior portions
thereof. Exterior portions of used rotary drill bits or other
downhole tools may be measured using three dimensional (3D)
scanning techniques or other techniques to determine specific
locations of undesired abrasion, erosion and/or wear. During the
design of a new rotary drill bit or other downhole tool,
computational flow analysis techniques may be used to determine
potential locations for excessive erosions, abrasion, wear, impact
and/or fatigue on exterior portions of the rotary drill bit or
other downhole tools. One or more layers of hard material may be
disposed at such locations on exterior portions of matrix bit
bodies and other matrix bodies based on analyzing exterior portions
of used downhole tools and/or computational flow analysis.
Inventors: |
Lind; William H.; (The
Woodlands, TX) ; Bird; Jay S.; (The Woodlands,
TX) |
Correspondence
Address: |
BAKER BOTTS L.L.P.;PATENT DEPARTMENT
98 SAN JACINTO BLVD., SUITE 1500
AUSTIN
TX
78701-4039
US
|
Assignee: |
HALLIBURTON ENERGY SERVICES,
INC.
Houston
TX
|
Family ID: |
42084243 |
Appl. No.: |
12/687718 |
Filed: |
January 14, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61148665 |
Jan 30, 2009 |
|
|
|
Current U.S.
Class: |
175/393 ;
175/426; 51/297; 51/307 |
Current CPC
Class: |
B24D 18/0009 20130101;
E21B 10/55 20130101; E21B 10/602 20130101; B22F 3/26 20130101; B22F
2005/001 20130101; C22C 29/08 20130101; B22F 7/08 20130101 |
Class at
Publication: |
175/393 ;
175/426; 51/297; 51/307 |
International
Class: |
E21B 10/55 20060101
E21B010/55; E21B 10/42 20060101 E21B010/42; E21B 10/60 20060101
E21B010/60; B24D 3/00 20060101 B24D003/00 |
Claims
1. A drill bit having a matrix bit body comprising: a plurality of
cutting elements disposed at selected locations on exterior
portions of the matrix bit body; at least a first, matrix material
having a first hardness satisfactory to form the matrix bit body;
the first, matrix material forming exterior portions of the matrix
bit body associated with engaging and removing formation materials
from a wellbore; at least one layer of a second material disposed
at one or more selected locations on exterior portions of the
matrix bit body; and the second material having a hardness greater
than the first hardness of the first, matrix material to improve
resistance of the matrix bit body at the selected location to
erosion, abrasion, wear, impact and/or fatigue forces proximate the
one or more selected locations.
2. The drill bit of claim 1 further comprising the second material
selected from the group consisting of cemented carbides, composite
carbides, spherical carbides, macrocrystalline tungsten carbides,
cast carbides, low alloy sintered material and formulates
thereof.
3. The drill bit of claim 1 wherein the at least one layer of
second material further comprises: a composite layer formed from
two or more sublayers of the second material; each sublayer
including an adhesive material with pellets of the second material
disposed therein; particles of the first matrix material disposed
within each adhesive layer; and the pellets of the second material
substantially larger than the particles of the first matrix
material.
4. The drill bit of claim 1 wherein the second material further
comprises tungsten carbide pellets.
5. The drill bit of claim 1 wherein the second material further
comprises crushed sintered tungsten carbide.
6. The drill bit of claim 1 wherein the second material further
comprises at least fifty percent (50%) tungsten carbide pellets by
weight.
7. The drill bit of claim 1 wherein the second material further
comprises at least seventy percent (70%) tungsten carbide pellets
by weight.
8. The drill bit of claim 1 wherein the second material further
comprises tungsten carbide pellets formed with binding material in
a range of approximately three percent (3%) or greater and less
than five percent (5%) of the weight of such tungsten carbide
pellets.
9. The drill bit of claim 1 further comprising multiple layers of
the second material disposed at each selected location on exterior
portions of the matrix bit body.
10. The drill bit of claim 1 wherein the matrix bit body further
comprises: multiple layers of the second material disposed at a
plurality of selected locations of exterior portions of the matrix
bit body improve resistance to abrasion, erosion, wear, impact
and/or fatigue forces at the selected locations; and small amounts
of the first, matrix material disposed within the layers of the
second material wherein the first, matrix material comprises less
than twenty percent (20%) by weight of each layer of the second
material.
11. A matrix drill bit having a matrix bit body with composite
exterior portions comprising: a plurality of blades disposed on and
extending from exterior portions of the matrix bit body; respective
fluid paths disposed between adjacent blades whereby fluid
associated with drilling a wellbore in a downhole formation may
flow between adjacent blades through the respective fluid path; a
plurality of cutting elements disposed at selected locations on
exterior portions of each blade; the matrix bit body formed in part
from at least a first, matrix material having a first hardness; the
first, matrix material forming exterior portions of the matrix bit
body associated with engaging and removing formation materials from
downhole locations in a wellbore; respective layers of a second
material disposed at selected locations on exterior portions of the
matrix bit body which are generally associated with potential
erosion, abrasion, wear, impact and/or fatigue forces of the matrix
bit body; and the second material having a second hardness greater
than the first hardness of the first material whereby the layers of
the second material cooperate with the first material to form a
dual surface composition to improve resistance to erosion,
abrasion, wear, impact and/or fatigue forces proximate the
respective selected locations on the matrix bit body.
12. The drill bit of claim 11 further comprising the first material
selected from the group consisting of cemented carbides, composite
carbides, spherical carbides, macrocrystalline tungsten carbide
powders, cast carbide powders and formulates thereof.
13. The drill bit of claim 11 further comprising the respective
layers of the second material having a combined thickness between
approximately 0.25 inches and 0.50 inches at one or more of the
selected locations.
14. The drill bit of claim 11 further comprising a single layer of
the second material having a combined thickness between
approximately 0.25 inches and 0.50 inches at one or more of the
selected locations.
15. The drill bit of claim 11 wherein the second material further
comprises tungsten carbide pellets.
16. The drill bit of claim 11 wherein the second material further
comprises tungsten carbide pellets formed with respective binding
material in a range of approximately three percent (3%) or greater
and less than five percent (5%) of the weight of such tungsten
carbide pellets.
17. The drill bit of claim 16 wherein the second material further
comprises the tungsten carbide pellets formed with a cobalt binder
providing approximately four percent (4%) of the weight of such
tungsten carbide pellets.
18. The drill bit of claim 11 wherein at least one layer the second
material further comprises a mixture of encrusted diamond pellets
and tungsten carbide pellets.
19. The drill bits of claim 11 wherein the matrix bit body further
comprises: at least one nozzle opening extending through the matrix
bit body to allow communication of drilling fluids from interior
portions of the matrix bit body to exterior portions of the matrix
bit body; and a plurality of layers of the second material disposed
proximate to the nozzle opening to minimize erosion of the matrix
bit body from associated drilling fluids exiting from the nozzle
opening.
20. The drill bit of claim 11 wherein the matrix bit body further
comprises: each blade having a leading surface and a trailing
surface; and multiple layers of the second material disposed
adjacent to the leading surface of each blade whereby the layers of
the second material minimize erosion, abrasion and wear along the
leading surface of each respective blade.
21. The drill bit of claim 11 wherein the matrix bit body further
comprises: each blade having a plurality of pockets sized to
receive a respective cutting element therein; at least one layer of
the second material disposed within each pocket; and a respective
cutting element securely disposed within each pocket whereby the
respective layer of the second material minimize erosion, abrasion
and/or wear of the pocket when the respective cutting element
engages downhole formation materials to form a wellbore.
22. The rotary drill bit of claim 11 further comprising at least
one layer of hard material disposed on exterior portions of the
matrix bit body in at least one flow path disposed between
associated blades.
23. A method of making a matrix drill bit comprising: placing a
respective layer of hard material at selected locations on interior
portions of a matrix bit body mold; placing a hollow bit blank in
the matrix bit body mold; placing at least one matrix material
selected from the group consisting of cemented carbides, composite
carbides, spherical carbides, macrocrystalline tungsten carbide and
cast carbide and formulates thereof in the mold; placing a binder
material in the mold with the binder material disposed proximate
the matrix material and the hollow bit blank; heating the mold and
the materials disposed therein to a selected temperature to allow
the binder material to melt and infiltrate the matrix material and
the layers of hard material and associated tungsten carbide pellets
with hot, liquid binder material; and cooling the mold and
materials disposed therein to form a matrix bit body with multiple
layers of hard disposed proximate selected locations on exterior
portions of the matrix bit body.
24. The method of claim 23 further comprising forming interior
portions of the matrix bit body with more than one matrix
material.
25. The method of claim 23 further comprising forming multiple
layers of tungsten carbide pellets at selected locations on
exterior portions of the matrix bit body associated with engaging
and removing downhole formation materials during formation of a
wellbore.
26. The method of claim 23 further comprising forming multiple
layers of crushed sintered tungsten carbide at selected locations
on exterior portions of the matrix bit body associated with
engaging and removing downhole formation materials during formation
of a wellbore.
27. The method of claim 23 further comprising: determining
potential locations for excessive erosion, abrasion and/or wear of
exterior portions of the matrix bit body; and placing the layers of
hard material on interior portions of the matrix bit body mold
corresponding with the potential locations for excessive erosion,
abrasion and/or wear of exterior portions of the associated matrix
bit body prior to placing the matrix material in the mold.
28. The method of claim 23 further comprising forming the layers of
the hard material with respective dimensions including thickness
selected to minimize erosion, abrasion and/or wear proximate the
corresponding selected location on exterior portions of the matrix
bit body.
29. A method of making a matrix drill bit comprising: placing a
respective first layer of adhesive material at selected locations
on interior portions of a matrix bit body mold; placing tungsten
carbide pellets in each first layer of adhesive material; placing a
respective second layer of adhesive material on each first layer of
adhesive material and associated tungsten carbide pellets; placing
additional tungsten carbide pellets in each second layer of
adhesive material; placing a hollow bit blank in the matrix bit
body mold; placing at least one matrix material selected from the
group consisting of cemented carbides, composite carbides,
spherical carbides, macrocrystalline tungsten carbide and cast
carbide and formulates thereof in the mold; placing a binder
material in the mold with the binder material disposed proximate
the matrix material and the hollow bit blank; heating the mold and
the materials disposed therein to a selected temperature to allow
the binder material to melt and infiltrate the matrix material and
the layers of adhesive material and associated tungsten carbide
pellets with hot, liquid binder material; and cooling the mold and
materials disposed therein to form a matrix bit body with multiple
layers of tungsten carbide pellets disposed proximate selected
locations on exterior portions of the matrix bit body.
30. The method of claim 29 further comprising forming interior
portions of the matrix bit body with more than one matrix
material.
31. The method of claim 29 further comprising forming multiple
layers of tungsten carbide pellets at selected locations on
exterior portions of the matrix bit body associated with engaging
and removing downhole formation materials during formation of a
wellbore.
32. The method of claim 29 further comprising: determining
potential locations for excessive erosion, abrasion and/or wear of
exterior portions of the matrix bit body; and placing a first layer
of adhesive material with tungsten carbide pellets dispersed
therein on interior of the portions of the matrix bit body mold
corresponding with the potential locations for excessive erosion,
abrasion and/or wear of exterior portions of the associated matrix
bit body prior to placing the matrix material in the mold.
33. The method of claim 29 further comprising selecting the
adhesive material from the group consisting of one component
adhesives and two component adhesives.
34. The method of claim 29 further comprising forming the layers of
second material with respective dimensions including thickness
selected to minimize erosion, abrasion and/or wear proximate the
corresponding selected location on exterior portions of the matrix
bit body.
35. The method of claim 29 further comprising: forming the mold
cavity with a plurality of displacements disposed therein and each
displacement having a complex, arcuate configuration corresponding
with a desired configuration for a respective fluid flow path
disposed on exterior portions of the a head; and forming the mold
cavity with a plurality of negative blade profiles with each
negative blade profile disposed between associated displacements
and each negative blade profile having a complex, arcuate
configuration corresponding with a desired configuration for a
respective blade disposed on exterior portions of the bit head.
36. The method of claim 29 further comprising selecting an
infiltration material from the group consisting of tungsten
carbide, monotungsten carbide, ditungsten carbide, macro
crystalline tungsten carbide, other metal carbides, metal borides,
metal oxides, metal nitrides, polycrystalline diamond (PCD) or
mixtures of such infiltration materials.
37. A used drill bit having a matrix bit body comprising: a
plurality of cutting elements disposed at selected locations on
exterior portions of the matrix bit body; at least a first, matrix
material having a first hardness satisfactory to form the matrix
bit body; the first, matrix material forming exterior portions of
the matrix bit body associated with engaging and removing formation
materials from a wellbore; at least one layer of a second material
disposed at one or more selected locations on exterior portions of
the matrix bit body after the used drill bit has been used to form
at least one portion of a wellbore; and the second material having
a hardness greater than the first hardness of the first, matrix
material to improve resistance of the matrix bit body at the
selected location to erosion, abrasion, wear, impact and/or fatigue
forces proximate the one or more selected locations.
38. The used drill bit of claim 37 further comprising the second
material selected from the group consisting of cemented carbides,
composite carbides, spherical carbides, macrocrystalline tungsten
carbides, cast carbides, low alloy sintered material and formulates
thereof.
39. The used drill bit of claim 37 wherein the at least one layer
of second material further comprises: a composite layer formed from
two or more sublayers of the second material; each sublayer
including an adhesive material with pellets of the second material
disposed therein; particles of the first matrix material disposed
within each adhesive layer; and the pellets of the second material
substantially larger than the particles of the first matrix
material.
40. The used drill bit of claim 37 wherein the second material
further comprises tungsten carbide pellets.
41. The used drill bit of claim 37 wherein the second material
further comprises crushed sintered tungsten carbide.
42. The used drill bit of claim 37 wherein the second material
further comprises at least fifty percent (50%) tungsten carbide
pellets by weight.
43. The used drill bit of claim 37 wherein the second material
further comprises at least seventy percent (70%) tungsten carbide
pellets by weight.
44. The used drill bit of claim 37 wherein the second material
further comprises tungsten carbide pellets formed with binding
material in a range of approximately three percent (3%) or greater
and less than five percent (5%) of the weight of such tungsten
carbide pellets.
45. The used drill bits of claim 37 wherein the matrix bit body
further comprises: multiple layers of the second material disposed
at a plurality of selected locations of exterior portions of the
matrix bit body improve resistance to abrasion, erosion, wear,
impact and/or fatigue forces at the selected locations; and small
amounts of the first, matrix material disposed within the layers of
the second material wherein the first, matrix material comprises
less than twenty percent (20%) by weight of each layer of the
second material.
46. A matrix drill bit having a matrix bit body with composite
exterior portions comprising: a plurality of blades disposed on and
extending from exterior portions of the matrix bit body; respective
fluid paths disposed between adjacent blades whereby fluid
associated with drilling a wellbore in a downhole formation may
flow between adjacent blades through the respective fluid path; a
plurality of cutting elements disposed at selected locations on
exterior portions of each blade; the matrix bit body formed in part
from at least a first, matrix material having a first hardness; the
first, matrix material forming exterior portions of the matrix bit
body associated with engaging and removing formation materials from
downhole locations in a wellbore; at least one recess formed in
exterior portions of the matrix bit body at a selected location
generally associated with potential erosion, abrasion, wear, impact
and/or fatigue forces on the matrix bit body; at least one layer of
a second material disposed in each recess at the respective
selected location on exterior portions of the matrix bit body; and
the second material having a second hardness greater than the first
hardness of the first material whereby the layers of the second
material cooperate with the first material to form a dual surface
composition to improve resistance to erosion, abrasion, wear,
impact and/or fatigue forces proximate the respective selected
location of the recess on the matrix bit body.
47. The drill bit of claim 46 further comprising the first material
selected from the group consisting of cemented carbides, composite
carbides, spherical carbides, macrocrystalline tungsten carbide
powders, cast carbide powders and formulates thereof.
48. The drill bit of claim 46 wherein the second material further
comprises tungsten carbide pellets.
49. The drill bit of claim 46 wherein the second material further
comprises tungsten carbide pellets formed with respective binding
material in a range of approximately three percent (3%) or greater
and less than five percent (5%) of the weight of such tungsten
carbide pellets.
50. The drill bit of claim 46 wherein the second material further
comprises the tungsten carbide pellets formed with a cobalt binder
providing approximately four percent (4%) of the weight of such
tungsten carbide pellets.
51. The drill bit of claim 46 wherein at least one layer the second
material further comprises a mixture of encrusted diamond pellets
and tungsten carbide pellets.
52. The drill bits of claim 46 wherein the matrix bit body further
comprises: at least one nozzle opening extending through the matrix
bit body to allow communication of drilling fluids from interior
portions of the matrix bit body to exterior portions of the matrix
bit body; the recess disposed proximate the at least one nozzle
opening; and a plurality of layers of the second material disposed
in the recess proximate to the nozzle opening to minimize erosion
of the matrix bit body from associated drilling fluids exiting from
the nozzle opening.
53. The drill bit of claim 46 wherein the matrix bit body further
comprises: each blade having a leading surface and a trailing
surface; all respective recesses formed in the leading surface of
each blade; and multiple layers of the second material disposed in
each respective recess adjacent to the leading surface of each
blade whereby the layers of the second material minimize erosion,
abrasion and wear along the respective leading surface of each
respective blade.
54. The drill bit of claim 46 wherein the matrix bit body further
comprises: each blade having a plurality of pockets sized to
receive a respective cutting element therein; at least one recess
formed on exterior portions of each blade proximate at least one
pocket; and at least one layer of a second hard material disposed
in each recess; whereby the respective layers of the second
material minimize erosion, abrasion and/or wear of the associated
pockets when the respective cutting element engages downhole
formation materials to form a wellbore.
55. The rotary drill bit of claim 46 further comprising at least
one layer of hard material disposed in a recess at a selected
location in at least one flow path disposed between associated
blades.
Description
RELATED APPLICATION
[0001] This application claims the benefit of U.S. provisional
application Ser. No. 61/148,665 entitled "Matrix Drill Bit With
Dual Surface Compositions And Methods of Manufacture" filed Jan.
30, 2009, the contents of which is hereby incorporated by reference
in its entirety.
TECHNICAL FIELD
[0002] The present disclosure relates in general to matrix drill
bits and other well tools with matrix bodies having one or more
layers of hard material disposed at selected locations on exterior
portions thereof and, more particularly, to forming one or more
layers of hard material at selected locations during manufacture of
a matrix body or applying one or more layers of hard material at
selected locations on exterior portions of a used matrix body.
BACKGROUND OF THE DISCLOSURE
[0003] Rotary drill bits are frequently used to drill oil and gas
wells, geothermal wells and water wells. Rotary drill bits may be
generally classified as rotary cone or roller cone drill bits and
fixed cutter drill bits or drag bits. Fixed cutter drill bits or
drag bits may be formed with a matrix bit body having cutting
elements or inserts disposed at select locations of exterior
portions of the matrix bit body. Fluid flow passageways are
typically formed in the matrix bit body to allow communication of
drilling fluids from associated surface drilling equipment through
a drill string or drill pipe attached to the matrix bit body. Such
fixed cutter drill bits or drag bits may sometimes be referred to
as "matrix drill bits."
[0004] Matrix drill bits are typically formed by placing loose
matrix material (sometimes referred to as "matrix powder") into a
mold and infiltrating the matrix material with a hot, liquid binder
such as a copper alloy. The mold may be formed by various
techniques including, but not limited to, milling a block of
material such as graphite to define a mold cavity with features
that correspond generally with desired features of the resulting
matrix drill bit. Various features of the resulting matrix drill
bit such as blades, cutter pockets, and/or fluid flow passageways
may be provided by shaping the mold cavity, positioning one or more
mold inserts within the mold cavity and/or by positioning temporary
displacement materials within the mold cavity.
[0005] Since machining hard, abrasion, erosion and/or wear
resistant materials is generally both difficult and expensive, it
is common practice to form some metal parts with a desired
configuration and subsequently treat one or more portions of the
metal part to provide desired abrasion, erosion and/or wear
resistance. Examples may include directly hardening such surfaces
(carburizing and/or nitriding) one or more surfaces of a metal part
or applying a layer of hard, abrasion, erosion and/or wear
resistant material (hardfacing) to one or more surfaces of a metal
part depending upon desired amounts of abrasion, erosion and/or
wear resistance for such surfaces. For applications when resistance
to extreme abrasion, erosion and/or wear of a working surface
and/or associated substrate is desired, a layer of hard, abrasion,
erosion and/or wear resistant material (hardfacing) be applied to
the working surface to protect the associated substrate. Apply hard
facing to matrix materials such as a matrix bit body is often more
difficult and technically challenging as compared with applying the
same hardfacing to a generally uniform, non-matrix metal
surface.
[0006] Hardfacing may be generally defined as a layer of hard,
abrasion resistant material applied to a less resistant surface or
substrate by plating, welding, spraying or other well known
deposition techniques. Hardfacing is frequently used to extend the
service life of drill bits and other downhole tools used in the oil
and gas industry. Tungsten carbide and various alloys of tungsten
carbide are examples of hardfacing materials widely used to protect
drill bits and other downhole tools associated with drilling and
producing oil and gas wells.
[0007] A wide variety of hard materials have been applied to
exterior portions of rotary drill bits and other downhole tools.
Frequently used hard materials include, but are not limited to,
sintered tungsten carbide particles in a steel alloy matrix
deposit. Tungsten carbide particles may include grains of
monotungsten carbide, ditungsten carbide and/or macrocrystalline
tungsten carbide. Spherical cast tungsten carbide may typically be
formed with no binding material. Examples of binding materials used
to form tungsten carbide particles may include, but are not limited
to, cobalt, nickel, boron, molybdenum, niobium, chromium, iron and
alloys of these elements.
SUMMARY
[0008] The present disclosure provides matrix bit bodies for rotary
drill bits or matrix bodies for other downhole tools with one or
more layers of hard material disposed at selected locations to
provide substantially enhanced resistance to erosion, abrasion,
wear, impact and/or fatigue forces as compared with prior matrix
bodies without such layers of hard material. In accordance with
teachings of the present disclosure, such layers of hard material
may include tungsten carbide particles, formed with an optimum
amount of binding material, particles of other superabrasive and/or
superhard materials. Examples of such hard materials satisfactory
for use with the present disclosure may include, but are not
limited to, encrusted diamond particles, coated diamond particles,
silicon nitride (Si.sub.3N.sub.4), silicon carbide (SiC), boron
carbide (B.sub.4C) and cubic boron nitride (CBN). Such hard
materials may also be used to rebuild exterior portions of used
drill bits (sometimes referred to as "dull bits") in accordance
with teachings of the present disclosure.
[0009] One or more layers of hard material may be disposed at
selected locations on exterior portions of a matrix bit body
associated with a matrix drill bit or at selected locations on
other downhole tools in accordance with teachings of the present
disclosure during molding of an associated matrix body and/or after
molding of the associated matrix body. The resulting matrix body
may be described as having a dual phase exterior or dual surface
composition.
[0010] One aspect of the present disclosure may include placing one
or more layers of one or more hard materials at selected locations
in a mold corresponding generally with respective selected
locations on exterior portion of blades, cutter pockets, junk slots
and/or other components of an associated matrix bit body. A
preformed hollow bit blank or casting mandrel may be disposed in
the mold. One or more matrix materials may be added to the mold.
The matrix materials may be selected to form a hard, matrix bit
body. A binder material may also be added to the mold. During
heating of the mold, liquid binder material may flow through the
matrix materials and the one or more layers of the hard material.
The layer or layers of hard material may provide desired
enhancement to resist erosion, abrasion, wear, impact and/or
fatigue forces at respective selected locations on exterior
portions of the matrix bit body.
[0011] For some applications, a composite layer of hard material
may be disposed at selected locations on exterior portions of a
matrix bit body in accordance with teachings of the present
disclosure. Each composite layer of hard material may include two,
three or more smaller (thinner) layers or sublayers of hard
material. Each sublayer of hard material may include a plurality of
large hard particles including, but not limited to, low alloy
sintered materials in the form of pellets and/or low alloy sintered
material in the form of crushed powder. Other forms of low alloy
sintered material may also be used to enhance downhole drilling
performance and/or associated matrix drill bit life.
[0012] For some applications, a low percentage of binder material
(4% plus or minus 1% Co, Ni, B, Mo, Cr or Se binder or any
combination thereof) may be used to bind fine tungsten carbide
grains to form generally spherical tungsten carbide particles or
pellets. The use of such particles or pellets may provide
substantially increased carbide content at one or more selected
locations on exterior portions of an associated matrix body as
compared to hard materials with twenty to thirty percent (20% to
30%) binder. For some applications, the size of the resulting
tungsten carbide particles or pellets may be substantially enlarged
such that only one layer of the second hard material is required to
provide satisfactory resistance to erosion, abrasion, impact and/or
fatigue forces at a selected location. Used matrix drill bits may
be repaired by forming one or more layers of hard material at
selected locations on exterior portions of an associated matrix bit
body.
[0013] For some applications, one or more layers of the low alloy
sintered material may also include matrix materials used to form an
associated matrix bit body. Various binding processes including,
but not limited to, sintering and/or sinter-hipping may be used to
form spherical tungsten carbide particles or pellets in a sintering
furnace. For some applications a sintered tungsten carbide pellet
may be used in combination with conventional matrix materials to
form a matrix drill bit. Such materials may be used to rebuild a
matrix bit body in accordance with teachings of the present
disclosure.
[0014] Various techniques may be satisfactorily used to determine
the location or locations for forming one or more layers of hard
material on exterior portions of an associated matrix body. For
example, simulation of fluid flow over exterior portions of a
matrix drill bit or other downhole tools having a matrix body in
combination with analysis of wear patterns on exterior portions of
an associated matrix drill bit and/or other downhole tools may help
to identify one or more locations for forming such layers of hard
material. Three dimensional (3D) scanning of used drill bits,
visual inspection or other techniques may also be used to select
locations for forming one or more layers of hard material with
enhanced erosion, war, abrasion, impact and/or fatigue resistance
on exterior portions of a matrix bit body during manufacture of an
associated matrix drill bit.
[0015] Matrix materials including, but are not limited to, cemented
carbides of tungsten, macrocrystalline tungsten carbide, tungsten
cast carbide, titanium, tantalum, niobium, chromium, vanadium,
molybdenum, hafnium independently or in combination and/or
spherical carbides may be used to form one or more layers of hard
material at selected locations matrix bodies in accordance with
teachings of the present disclosure. However, the present
disclosure is not limited to cemented tungsten carbides, spherical
carbides, macrocrystalline tungsten carbide and/or cast tungsten
carbides or mixtures thereof.
[0016] Some embodiments one or more layers of hard material may be
disposed on exterior portions of a matrix body with at least one
layer having both large particles or pellets and small particles or
pellets. The ratio of larger pellets to small pellets may vary from
approximately one to one or fifty percent large pellets and fifty
percent small pellets to approximately three (3) large pellets for
every small pellet (3 to 1) or seventy five percent (75%) large
pellets and twenty five percent (25%) small pellets. The size of a
typical small pellet of hard material may be approximately 20 mesh
(850.mu.) to 30 mesh (600.mu.). The size of a typical large pellet
of hard material may be approximately 16 mesh (1180.mu.) to 20 mesh
(850.mu.).
[0017] Additional features, steps, technical advantages and/or
benefits of the present disclosure may be discussed in the Detailed
Description and/or Claims. The above Summary is not intended to be
a comprehensive listing of all features, steps, technical
advantages and/or benefits of the present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] For a more complete understanding of the present disclosure
and its advantages thereof, reference is now made to the following
brief descriptions, taken in conjunction with the accompanying
drawings and detailed description, wherein like reference numerals
represent like parts, in which:
[0019] FIG. 1 is a schematic drawing showing an isometric view of
one example of a matrix drill bit having a matrix bit body with one
or more layers of hard material disposed at selected locations on
exterior portions of the matrix bit body;
[0020] FIG. 2A is a schematic drawing in section with portions
broken away showing a mold assembly satisfactory to form a matrix
body in accordance with teachings of the present disclosure;
[0021] FIG. 2B is a schematic drawing showing multiple layers of
hard material or a composite layer of hard material which may be
disposed at one or more locations on interior portions of the mold
shown in FIG. 2A;
[0022] FIG. 2C is a schematic drawing in section with portions
broken away showing a single layer of hard material which may be
disposed at one or more locations on interior portions of the mold
shown in FIG. 2A;
[0023] FIG. 3A is a schematic drawing in elevation with portions
broken away showing a welding rod with hard materials disposed
therein in accordance with teachings of the present disclosure;
[0024] FIG. 3B is an enlarged schematic drawing in section with
portions broken away showing tungsten carbide pellets and other
hard materials disposed within the welding rod of FIG. 3A;
[0025] FIG. 3C is an enlarged schematic drawing in section with
portions broken away showing tungsten carbide pellets formed with
an optimum weight percentage of binding material and bonded to a
matrix deposit disposed on and bonded to a substrate or matrix body
in accordance with teachings of the present disclosure;
[0026] FIG. 4A is a schematic drawing in elevation with portions
broken away showing a welding rod with hard materials disposed
therein in accordance with teachings of the present disclosure;
[0027] FIG. 4B is an enlarged schematic drawing in elevation and in
section with portions broken away showing tungsten carbide pellets,
encrusted diamond particles and other hard materials disposed
within the welding rod of FIG. 4A;
[0028] FIG. 4C is an enlarged schematic drawing in section with
portions broken away showing tungsten carbide pellets formed with
an optimum weight percentage of binding material along with
encrusted diamond particles and bonded to a matrix deposit disposed
on and bonded to a substrate or matrix body in accordance with
teachings of the present disclosure;
[0029] FIG. 5 is a schematic drawing in section with portions
broken away showing a mold assembly with mold inserts, matrix
materials and other materials disposed therein satisfactory to form
a matrix bit body in accordance with teachings of the present
disclosure; and
[0030] FIG. 6 is a schematic drawing in section with portions
broken away showing a matrix bit body with recesses formed in
exterior portions thereof in accordance with teachings of the
present disclosure.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0031] Preferred embodiments and various advantages may be
understood by referring in more detail to FIGS. 1-6 of the
drawings, in which like numerals refer to like parts.
[0032] The terms "matrix bit", "matrix drill bit" and "matrix
rotary drill bit" may be used in this application to refer to
"rotary drag bits", "drag bits", "fixed cutter drill bits" or any
other drill bit incorporating teaching of the present disclosure.
Such drill bits may be used to form well bores or boreholes in
subterranean formations.
[0033] Matrix drill bits incorporating teachings of the present
disclosure may include a matrix bit body formed by one or more
matrix materials. For other embodiments (not expressly shown) a
matrix bit body may be formed with at least a first matrix material
and a second matrix material. For some applications the first
matrix material may have increased toughness or high resistance to
fracture and also provide erosion, abrasion and wear resistance.
The second matrix material (not expressly shown) with only a
limited amount of alloy materials or other contaminates may also be
used to form the matrix bit body. The first matrix material may
include, but is not limited to, cemented carbides or spherical
carbides. The second matrix material may include, but is not
limited to, macrocrystalline tungsten carbides and/or cast
carbides. One or more layers of hard material may be disposed at
selected locations on matrix bodies formed from matrix materials in
accordance with teachings of the present disclosure.
[0034] Various types of binder materials may be used to infiltrate
matrix materials disposed in a mold to form a matrix bit body.
Binder materials may include, but are not limited to, copper (Cu),
nickel (Ni), cobalt (Co), iron (Fe), molybdenum (Mo) individually
or alloys based on these metals. The alloying elements may include,
but are not limited to, one or more of the following
elements--manganese (Mn), nickel (Ni), tin (Sn), zinc (Zn), silicon
(Si), molybdenum (Mo), tungsten (W), boron (B) and phosphorous (P).
The matrix bit body may be attached to a hollow bit blank or
casting mandrel. A generally hollow shank or hollow tool joint with
a threaded connection may be attached to the hollow bit blank or
casting mandrel for use in releasably engaging the associated
matrix drill bit with a drill string, drill pipe, bottom hole
assembly or downhole drilling motor (not expressly shown).
[0035] The terms "cemented carbide" and "cemented carbides" may be
used within this application to include WC, MoC, TiC, TaC, NbC,
Cr.sub.3C.sub.2, VC and solid solutions of mixed carbides such as
WC--TiC, WC--TiC--TaC, WC--TiC--(Ta,Nb)C in a metallic binder
(matrix) phase. Typically, Co, Ni, Fe, Mo and/or their alloys may
be used to form the metallic binder. Cemented carbides may
sometimes be referred to as "composite" carbides or sintered
carbides. Some cemented carbides may also be referred to as
spherical carbides. However, cemented carbides may have many
configurations and shapes other than spherical.
[0036] Cemented carbides may be generally described as powdered
refractory carbides which have been united by compression and heat
with binder materials such as powdered cobalt, iron, nickel,
molybdenum and/or their alloys. Cemented carbides may also be
sintered, crushed, screened and/or further processed as
appropriate. Cemented carbide pellets may be used to form a matrix
bit body. The binder material may provide ductility and toughness
which often results in greater resistance to fracture (toughness)
of cemented carbide pellets, spheres or other configurations as
compared to cast carbides, macrocrystalline tungsten carbide and/or
formulates thereof.
[0037] Binder materials used to form cemented carbides may
sometimes be referred to as "bonding materials" in this Application
to help distinguish between binder materials used to form cemented
carbides and binder materials used to form a matrix drill bit.
[0038] The terms "computational fluid dynamics" and/or "CFD" may be
used in this application to include various commercially available
computer programs and algorithms used to simulate and evaluate
complex fluid interactions. Such simulations may include
calculating mass transfer, turbulence, velocity changes and other
characteristics associated with multiphase, complex fluid flow
associated with a matrix drill bit forming a wellbore. Such fluids
may often be a mixture of liquids, solids and/or gases with varying
concentrations depending on associated downhole drilling
conditions. Simulations using CFD programs may be used to determine
optimum locations for forming one or more layers of hard material
on exterior portions of a matrix body based on anticipated fluid
flow for the type/size of pump used on an associated drilling rig
(not expressly shown), size of associated drill string (not
expressly shown), size and configuration of an associated matrix
drill bit or other downhole tool and/or anticipated downhole
drilling conditions.
[0039] The term "digital scanning" may be used to describe a wide
variety of equipment and techniques satisfactory for measuring
exterior dimensions of a matrix drill bit and other downhole tools
with a very high degree of accuracy and to create a three
dimensional image of exterior portions of such well tools. The
results of digital scanning may be used with other computer
programs such as "computational fluid dynamics" or CFD programs to
evaluate fluid flow characteristics over exterior portions of
matrix drill bits and other downhole tools.
[0040] Some examples of digital scanning equipment and techniques
are discussed in copending U.S. Patent Application Ser. No.
60/992,392; Filing Date: Dec. 5, 2007, entitled "Method and
Apparatus to Improve Design, Manufacture, Performance and/or Use of
Well Tools" now U.S. patent Ser. No. ______. CFD programs are
available from various vendors. One example of a CFD program
satisfactory for use with the present invention is FLUENT,
available from ANSYS, Inc. located in Canonsburg, Pa.
[0041] Various computer programs and computer models may be used to
design blades, cutting elements, fluid flow paths and/or associated
rotary drill bits. Examples of such methods and systems which may
be used to design and evaluate performance of cutting elements and
rotary drill bits are shown in copending U.S. patent applications
entitled "Methods and Systems for Designing and/or Selecting
Drilling Equipment Using Predictions of Rotary Drill Bit Walk,"
application Ser. No. 11/462,898, filing date Aug. 7, 2006, (now
U.S. patent Ser. No. ______); copending U.S. patent application
entitled "Methods and Systems of Rotary Drill Bit Steerability
Prediction, Rotary Drill Bit Design and Operation," application
Ser. No. 11/462,918, filed Aug. 7, 2006, (now U.S. patent Ser. No.
______) and copending U.S. patent application entitled "Methods and
Systems for Design and/or Selection of Drilling Equipment Based on
Wellbore Simulations," application Ser. No. 11/462,929, filing date
Aug. 7, 2006, (now U.S. patent Ser. No. ______).
[0042] The terms "dual surface compositions", "dual exterior
composition", dual phase surface" and/or "dual phase exterior" may
be used to describe a matrix body having one or more layers of hard
material disposed at selected locations on exterior portions of the
matrix body. The matrix body may be formed from one or more matrix
materials. Hard materials forming the layer or layers at the
selected locations on exterior portions of the matrix body may
generally have a hardness greater than the hardness of matrix
materials used to form the associated matrix body.
[0043] The term "gage pad" as used in this application may include
a gage, gage segment or gage portion disposed on exterior portion
of a blade. Gage pads may often contact adjacent portions of a
wellbore formed by an associated rotary drill bit. Exterior
portions of blades and/or associated gage pads may be disposed at
various angles, either positive or negative and/or parallel,
relative to adjacent portions of a straight wellbore. A gage pad
may include one or more layers of material formed in accordance
with teachings of the present disclosure. One or more gage pads may
be disposed on a blade.
[0044] The terms "matrix deposit" and/or "metallic matrix deposit"
may refer to a layer or layers of hard material disposed at
selected exterior portions of a matrix body and/or substrate to
protect the matrix body and/or the substrate at the selected
locations from abrasion, erosion, wear, impact and/or fatigue
forces. A matrix deposit may also sometimes be referred to as
"metallic alloy material" or as a "deposit matrix." Various binders
and/or binding materials such as cobalt, nickel, copper, iron and
alloys thereof may be used to form a matrix deposit with hard,
abrasion resistant materials and/or particles dispersed therein and
bonded thereto. Nickel based alloys with increased ductility may be
used at locations subject to erosion and/or abrasion.
[0045] Various types of tungsten carbide particles and/or pellets
having an optimum size and/or optimum weight percentage of binder
or binding material may be included as part of a matrix deposit or
layer of hard material incorporating teachings of the present
disclosure. One or more layers of hard material may be formed on a
matrix body from a wide range of hard metal alloys and other hard
materials.
[0046] The term "tungsten carbide" may include monotungsten carbide
(WC), ditungsten carbide (W.sub.2C), macrocrystalline tungsten
carbide.
[0047] The terms "tungsten carbide pellet," "WC pellet," "tungsten
carbide pellets" and "WC pellets" may refer to nuggets, spheres
and/or particles of tungsten carbide formed with an optimum size
and/or weight percentage of binding material in accordance with the
teachings of the present disclosure. The terms "binder", "binding
material" and/or "binder materials" may be used interchangeably in
this Application.
[0048] FIG. 1 is a schematic drawing showing one example of a fixed
cutter drill bit or matrix drill bit having one or more layers of
hard material disposed on exterior portion thereof in accordance
with teachings of the present disclosure. Matrix drill bit 20 as
shown in FIG. 1 may sometimes be referred to as a "rotary drill
bit," "fixed cutter drill bit" or "drag bit". Matrix drill bit 20
may include matrix bit body 50 having a plurality of blades 54
extending radially therefrom. Respective fluid flow paths
(sometimes referred to as "junk slots") 56 may be disposed between
adjacent blades 54. Each blade 54 may include respective leading
surface 51 and trailing surface 52. Arrow 24 indicates the general
direction of rotation of rotary drill bit 20 relative to an
associated bit rotational axis (not expressly shown) during
formation of a wellbore (not expressly shown).
[0049] First end or downhole end 21 of matrix drill bit 20 may
include a plurality of cutting elements 60 operable to engage
downhole formation materials and remove such materials to form a
wellbore. Each cutting element 60 may be disposed in respective
pocket 62 formed on exterior portion 58 of respective blade 54.
Each cutting element 60 may include respective cutting surface 64
formed from hard materials satisfactory for engaging and removing
adjacent downhole formation materials (not expressly shown).
[0050] Cutting elements 60 may scrape and gouge formation materials
from the bottom and sides of a wellbore (not expressly shown)
during rotation of matrix drill bit 20. For some applications,
various types of polycrystalline diamond compact (PDC) cutters may
be satisfactorily used as cutting elements 60. A matrix drill bit
having PDC cutters may sometimes be referred to as a "PDC bit".
[0051] Second end 22 of matrix drill bit 20 may include shank or
tool joint 30 operable to releasably engage matrix drill bit 20
with a drill string (not expressly shown), bottom hole assembly
(not expressly shown) and/or a downhole drilling motor (not
expressly shown) to rotate matrix drill bit 20 during formation of
a wellbore. Shank 30 and associated bit blank 36 may be described
as having respective generally hollow cylindrical configurations
defined in part by a fluid flow passageway extending therethrough.
See, for example fluid flow passageway 32 in FIG. 6. Various types
of threaded connections such as American Petroleum Institute (API)
drill pipe connection or threaded pin 34 may be formed on shank 30
proximate second end 22 of matrix drill bit 20. Shank 30 may also
include bit breaker slots 35.
[0052] Various techniques may be used to securely engage generally
hollow shank 30 with portions of bit blank 36 extending from matrix
bit body 50. See for example FIGS. 1 and 6. For example, weld 39
may be formed in groove 38 disposed between and extending around
the perimeter of shank 30 and bit blank 36.
[0053] For some applications each blade 54 may include respective
recess 70 formed in exterior portion 58 of each blade 54. The
location and dimensions of each recess 70 may be selected to
correspond generally with a selected location for forming a gage
pad on associated blade 54. FIGS. 5 and 6 show one example of
techniques which may be satisfactorily used to form respective
recess 70 at selected locations on exterior portion 58 of each
blade 54. One or more layers of hard material may be disposed
within each recess 70 in accordance with teachings of the present
disclosure.
[0054] FIGS. 3A and 3B and FIGS. 4A and 4B show examples of welding
rods 71 and 71a which may be used to form one or more layers of
hard material in recess 70 in accordance with teachings of the
present disclosure. Welding rods 71 and 71a may also be used to
repair or rebuild a used matrix drill bit or matrix body in
accordance with teachings of the present disclosure.
[0055] One or more nozzle openings 66 may be formed in exterior
portions of matrix bit body 50. Respective nozzle 68 may be
disposed in each nozzle opening 66. Various types of drilling fluid
may be pumped from surface drilling equipment (not expressly shown)
through an associated drill string (not expressly shown) attached
to threaded connection 34 of shank or tool joint 30 to fluid flow
passageway 32 disposed within matrix bit body 50. One or more fluid
flow paths may be formed in matrix bit body 50 to communicate
drilling fluid and/or other fluids to associated nozzle 68. See for
example fluid passageways 72 and 74 in FIG. 6. For some
embodiments, one or more layers 101 of hard material may be
disposed on exterior portions of matrix bit body 50 adjacent to
nozzle opening 66. See for example FIG. 1.
[0056] One or more layers of hard material 102 may be disposed on
exterior portions of one or more blades 54 proximate a transition
or junction between adjacent junk slot 56 and associated leading
surface 51. One or more layers 103 of hard material may be disposed
on trailing surface 52 of one or more blades 54. In a similar
manner, one or more layers 104 of hard material may be disposed on
exterior portion 58 of each blade 54 proximate associated pockets
62 and/or cutting elements 60. One or more layers 105 of hard
material may be disposed exterior portions of selected pockets 62.
Respective locations, dimensions and configurations for layers 101,
102, 103, 104 and 105 and associated hard materials on new matrix
drill bits and/or used matrix drill bits may be selected using CFD
analysis, digital scanning, visual scanning and drill bit design
techniques in accordance with teachings of the present
disclosure.
[0057] U.S. Pat. No. 6,296,069 entitled Bladed Drill Bit with
Centrally Distributed Diamond Cutters and U.S. Pat. No. 6,302,224
entitled Drag-Bit Drilling with Multiaxial Tooth Inserts show
various examples of blades and/or cutting elements which may be
used with a matrix bit body incorporating teachings of the present
disclosure. It will be apparent to persons having ordinary skill in
the art that a wide variety of fixed cutter drill bits, drag bits
and other drill bits may be satisfactorily formed with a matrix bit
body incorporating teachings of the present disclosure. The present
disclosure is not limited to matrix drill bit 20 or any specific
features as shown in FIGS. 1-6.
[0058] A wide variety of molds may be satisfactorily used to form a
matrix bit body and associated matrix drill bit in accordance with
teachings of the present disclosure. Mold assembly 200 shown in
FIG. 2A and mold assembly 200a shown in FIG. 5 represents only two
examples of mold assemblies satisfactory for use in forming a
matrix bit body incorporating teachings of the present disclosure.
U.S. Pat. No. 5,373,907 entitled Method And Apparatus For
Manufacturing And Inspecting The Quality Of A Matrix Body Drill Bit
shows additional details concerning mold assemblies and
conventional matrix bit bodies.
[0059] Layers 101, 102, 103, 104 and 105 of various hard materials
may be placed in mold assembly 200 at locations 101a, 102a, 103a,
104a and 105a corresponding generally with selected locations for
forming corresponding layers of hard material on exterior portions
of matrix drill bit 20. One or more layers 101-105 of hard material
may be disposed at each location in accordance with teachings of
the present disclosure. For some applications a composite layer or
multiple layers of hard material may be disposed at each location
in mold assembly 200. See for example FIG. 2B. For other
applications a single layer of hard material may be disposed at
each location in mold assembly 200. See for example FIG. 2C.
[0060] Mold assemblies 200 and 200a as shown in FIGS. 2A, 5 and 6
represent only two examples of molds and/or mold assemblies which
may be satisfactorily used to form a matrix body incorporating
teachings of the present disclosure. Mold assemblies 200 and 200a
may be generally described as having cylindrical configurations
defined in part by respective first, opened end 201 and second,
closed end 202 with respective mold cavity 252 and 252a disposed
there between. Mold cavities 252 and 252a may be generally
described as negative images or inverse images of a matrix bit body
formed by the respective mold assemblies 200 and 200a.
[0061] For some embodiments, interior portions of mold cavities 252
and/or 252a may be coated with a mold wash to prevent gasses,
produced by heating and/or cooling of associated mold assemblies
200 and 200a, from entering into matrix materials disposed within
respective mold cavities 252 and 252a. Various commercially
available mold washes may be satisfactorily used. Mold assemblies
200 and/or 200a may also be placed within a container (not
expressly shown). Interior portions of such containers may be
designed to receive exterior portions of mold assemblies 200 and/or
200a. Such containers may sometimes be referred to as a "housing",
"crucible" and/or "bucket".
[0062] Mold assembly 200 as shown in FIG. 2A may include a
plurality of displacements 208 disposed on interior portions of
mold cavity 252. The configuration and dimensions associated with
each displacement 208 may be selected to generally correspond with
blades 54 and fluid flow paths 56 formed on exterior portions of
matrix bit body 50.
[0063] Depending on the type of materials used to form mold
assembly 200 and/or heating and cooling cycles associated with
forming matrix bit body 50, out gassing may occur. For such
applications, a plurality of internal flow paths (not expressly
shown) may be formed within mold assembly 200. Such fluid flow
paths may communicate gasses associated with heating and cooling of
mold assembly 200 through fluid flow channels 206 and/or exterior
portions of mold assembly 200.
[0064] Mold cavity 252 as shown in FIG. 2A may be formed with a
plurality of negative blade profiles 210 disposed between
respective displacements 208. For some applications, mold assembly
200 and associated components may be formed using a 3D printer in
combination with 3D design data. A plurality of negative pocket
recesses or pocket profiles 262 may be formed within each negative
blade profile 210. Negative pocket recesses 262 may have complex
configurations and/or orientations as desired for respective pocket
62 and associated cutting element 60.
[0065] Locations 101a-105a within mold assembly 200 may be selected
to correspond generally with locations on exterior portions of
associated matrix drill bit 20 where high erosion, abrasion, wear,
impact and/or fatigued forces may be applied. For example, one or
more layers of hard material may be disposed at location 101a to
minimize erosion from fluid flowing from associated nozzle 68. One
or more layers of hard material may be disposed at locations 102a
and 103a to minimize abrasion and/or wear associated with fluid
flowing through associated flow path or junk slot 56. One or more
layers of a second hard material may be disposed at locations 104a
to minimize erosion, abrasion, wear, impact and/or fatigue forces
applied to exterior portions 58 of associated blade 54 during
engagement of associated cutting elements 60 with adjacent downhole
formation materials. One or more layers of hard material may be
disposed at location 105a on exterior portions of associated pocket
62 to minimize erosion, abrasion, wear, impact and/or fatigue
forces resulting from respective cutting element 60 engaging and
removing downhole formation materials.
[0066] FIGS. 2B and 2C show examples of layers of hard materials
which may be disposed at one or more locations 101a-105a in
accordance with teachings of the present disclosure. FIG. 2B shows
first layer or sublayer 111, second layer or sublayer 112 and third
layer or sublayer 113 disposed at location 101a in mold assembly
200. The resulting configuration of layers or sublayers 111, 112
and 113 may sometimes be referred to as "composite layer" 101. Each
sublayer 111, 112 and 113 may have approximately the same general
configuration and dimensions including thickness. Each layer 111,
112 and 113 may include a plurality of large pellets 130 and/or
140. Also, a plurality of smaller pellets and matrix material 131
used to form associated matrix drill bit 20 may also be disposed
within layers 111, 112 and/or 113.
[0067] For embodiments such as shown in FIG. 2B, first layer 111
may start with a layer of glue disposed at location 101a. Various
types of glue and/or adhesive materials including, but not limited
to, aerosol adhesives such as Super 77 Multipurpose Adhesive
available from 3M Company located in St. Paul, Minn. may be
satisfactorily used. Hard particles or hard pellets 130 as shown in
FIGS. 2B and 3C and/or hard pellets 140 as shown in FIGS. 4B and 4C
may then be disbursed within the glue of first layer 111. Matrix
material 131 may also be disbursed within first layer 111. The
ratio of hard pellets or hard particles with respect to matrix
material may be selected to provide desired uniformity of the
resulting first layer 111 and desired hardness.
[0068] A second layer of glue may be disposed on first layer 110 at
location 101a. Additional hard pellets 130 and/or 140 may then be
distributed within the glue at second layer 112. Matrix material
131 may be disbursed within the glue at second layer 112. Similar
procedures may be used to form third layer 113 and additional
layers of glue, hard pellets and/or matrix material as desired for
each selected location on exterior portions of matrix drill bit
20.
[0069] The dimensions and configuration of each layer of glue may
be selected to correspond with desired dimensions and configuration
of corresponding layers 101-105 of hard material disposed at
selected locations on exterior portions of matrix drill bit 20. For
some applications, the total thickness of the hard material
disposed at respective locations 101a-105a may be between
approximately 0.25 inches and 0.5 inches.
[0070] FIG. 2C is a schematic drawing showing single layer 114 and
hard materials which may also be disposed at location 101a or any
other desired location in mold assembly 200. The overall
configuration and dimensions of layer 114 in FIG. 2C may be
approximately the same as composite layer 101 in FIG. 2B. For some
applications, pellets 130 and/or 140 as shown in FIG. 2C may be
larger than corresponding pellets 130 and/or 140 as shown in FIG.
2B. For some applications increasing the size of the pellets may
accommodate forming layer 114 in FIG. 2C in a "single pass" of
adhesive material and a "single pass" to disperse hard materials
therein as compared with composite layer 101 formed by using three
separate layers or sublayers 111, 112 and 113 of glue and
respective distribution of hard materials within each layer or
sublayer.
[0071] The types of hard materials used to form layers 111, 112,
113 and 114 may be selected to be compatible with infiltration of
binder material therethrough during infiltration of matrix
materials 131 and 132 to form matrix bit body 50. Some examples of
hard materials which may be satisfactory used to form one or more
layers of hard material disposed on exterior portions of a matrix
drill bit in accordance with teachings of the present disclosure
are shown in FIGS. 3B, 3C, 4B and 4D.
[0072] FIGS. 3C and 4C are schematic representations of respective
layers of hard material disposed on matrix material 131 in
accordance with teachings of the present disclosure. For purposes
of explanation, surface 122 as shown in FIGS. 3C and 4C may be
representative of respective exterior surfaces 122 associated with
layers 101-105 of hard material disposed at selected locations on
exterior portions of matrix drill bit 50. See FIG. 1. Respective
surfaces 122 of layers 101-105 may conform with and be tightly
bonded to adjacent matrix materials used to form matrix bit body
50. The cross sections of a layer of hard material disposed on
matrix material as shown in FIGS. 3C and 4C may also be
representative of one or more layers of hard material disposed in
recesses 70 to form a gage pad (not expressly shown) on respective
blades 54.
[0073] Layer 103 as shown in FIG. 3C may include tungsten carbide
particles or pellets 130 disposed in matrix 146 in accordance with
teachings of the present disclosure. Other hard materials and/or
hard particles selected from a wide variety of metals, metal
alloys, ceramic alloys and/or cermets may also be used to form one
or more layers 103 of hard material. As a result of using tungsten
carbide particles 130 having an optimum weight percentage of binder
material, layer 103 may enhance erosion, abrasion, wear, impact
and/or fatigue resistance as compared with exterior portions of
matrix bit body 50 which do not include such layers of hard
material.
[0074] Layer 104 as shown in FIG. 4C may include tungsten carbide
particles or pellets 130 and encapsulated diamond particles 140. In
accordance with teachings of the present disclosure. Other hard
materials and/or hard particles selected from a wide variety of
metals, metal alloys, ceramic alloys and/or cermets may also be
used to form one or more layers 104 of hard material. By including
both a combination of tungsten carbide pellets 130 and diamond
encrusted particles or pellets 140, layer 104 may have enhanced
erosion, abrasion, wear, impact and/or fatigues resistance as
compared with exterior portions of matrix bit body 50 which do not
include such layers of hard material.
[0075] FIGS. 3A and 4A shows examples of welding rods which may be
satisfactory used to form one or more layers of hard material on
exterior portions of matrix bit body 50 such as respective recesses
70 formed on blades 54 following removal of matrix bit body 50 from
as associated mold assembly. The welding rods 71 and 71a may also
be used to form one or more layers of hard material to repair a
used matrix drill bit in accordance with teachings of the present
disclosure.
[0076] For some applications both new matrix bit bodies and used
matrix drill bits may be heated to a desired temperature such as
approximately seven hundred degrees Fahrenheit (700.degree. F.) and
allowed to "soak" prior to forming one or more layers of hard
material on exterior portions thereof using welding rods 71 or 71a.
The desired temperature may vary depending on materials used to
form an associated matrix bit body and hard particles used to form
the layers of hard material.
[0077] Heating a matrix bit body to an appropriate, relatively
uniform temperature may minimize potential cracking or damage to
the matrix bit body during welding. After one or more layers of
hard material have been disposed at selected locations on the
associated matrix bit body, the matrix bit body may be slowly
cooled at a desired rate to ambient temperature. The cooling rate
may be selected to prevent cracking or damage to the matrix bit
body and/or layers of hard material.
[0078] Welding rod 71 as shown in FIGS. 3A and 3B may be used to
form a layer of hard material with characteristics similar to layer
103 as shown in FIG. 3C. Welding rod 71a as shown in FIGS. 4A and
4B may be used to form a layer of hard material with
characteristics similar to layer 104a shown in FIG. 4C. Welding
rods 71 and 71a may include respective hollow steel tube 76 which
may be closed at both ends with filler 78 and hard particles 130
and/or 140 or other hard materials disposed therein.
[0079] For some applications tungsten carbide pellets may have
generally spherical configurations (see FIGS. 3C and 4C) with a
weight percentage of binder between approximately four percent (4%)
plus or minus one percent (1%) of the total weight of each tungsten
carbide pellet in accordance with teachings of the present
disclosure. Tungsten carbide pellets may also be formed with an
optimum weight percentage of binder and various non-spherical or
partially spherical configurations (not expressly shown). For some
applications crushed tungsten carbide pellets may also be used.
[0080] Spherical tungsten carbide pellets formed with no binding
material or substantially 0% binder may tend to crack and/or
fracture during formation of a matrix deposit or hardfacing layer
containing such pellets. Tungsten carbide pellets formed with no
binding material or substantially 0% binder may also fracture or
crack when exposed to thermal stress and/or impact stress.
Spherical tungsten carbide pellets formed with relatively high
percentages (5% or greater) by weight of binding material or binder
may tend to break down or dissolve into solution during formation
of an associated matrix deposit or hardfacing layer. As a result,
such spherical tungsten carbide pellets and associated matrix
deposit or hardfacing layer may have less abrasion, erosion, wear,
impact, and/or fatigue resistance than desired. Spherical tungsten
carbide pellets with more than 5% binder may crack when exposed to
thermal stress and/or impact stress.
[0081] Tungsten carbide pellets formed with an optimum percentage
of binding material or binder may neither crack nor dissolve into
solution in associated matrix material during formation of one or
more layers of hard material. Spherical tungsten carbide pellets
formed with an optimum percentage of binding material and/or binder
may also neither crack nor fracture when exposed to thermal stress
and/or impact stress. Forming tungsten carbide pellets with an
optimum weight percentage of binding material in accordance with
teachings of the present disclosure may improve weldability of the
tungsten carbide pellets and may substantially improve temperature
stress resistance and/or impact stress resistance of the tungsten
carbide pellets to fracturing and/or cracking.
[0082] For some applications layers of hard material formed with
spherical tungsten carbide particles having an optimum weight
percentage of binder have shown improved wear properties during
testing of associated layers and/or matrix deposits. For some
applications improvement in wear properties may increase
approximately forty-five percent (45%) during wear testing in
accordance with ASTM B611 as compared with a matrix deposits or
layers of hard material having spherical tungsten carbide particles
with binding material representing five percent (5%) or greater the
total weight of each tungsten carbide particle.
[0083] Layers of hard material may be formed with tungsten carbide
pellets having an optimum weight percentage of binding material in
a wide range of mesh sizes. For some applications the size of such
tungsten carbide pellets may vary between approximately 12 U.S.
mesh and 100 U.S. mesh. The ability to use a wide range of mesh
sizes may substantially reduce costs of manufacturing such tungsten
carbide pellets and costs associated with forming a deposit matrix
or hardfacing with such tungsten carbide pellets. For example,
tungsten carbide pellets 130 as shown in FIG. 3C or 4C may have a
size range from approximately 12 to 100 U.S. Mesh.
[0084] Depending upon selected locations for depositing one or more
layers of hard material on a matrix bit body, tungsten carbide
pellets 130 may be selected within a more limited size range such
as 40 U.S. Mesh to 80 U.S. Mesh. For other applications, tungsten
carbide pellets 130 may be selected from two or more different size
ranges such as 30 to 60 mesh and 80 to 100 mesh. Tungsten carbide
pellets 130 may have approximately the same general spherical
configuration. However, by including tungsten carbide pellets 130
or other hard particles with different configurations and/or mesh
ranges, wear, erosion, abrasion, impact, and/or fatigue resistance
of resulting layers of hard material may be modified to accommodate
specific downhole operating environments for an associated matrix
drill bit. By increasing the size of tungsten carbide pellets 130,
a single layer of hard material having optimum thickness may be
deposited within mold assembly 200 with a single pass. For some
applications the optimum size for tungsten carbide pellets may be
approximately sixteen (16) mesh to thirty (30) mesh.
[0085] Tungsten carbide pellets may be formed by cementing,
sintering, and/or HIP-sintering (sometimes referred to as
"sinter-hipping") fine grains of tungsten carbide with an optimum
weight percentage of binding material. Sintered tungsten carbide
pellets may be made from a mixture of tungsten carbide and binding
material such as cobalt powder. Other examples of binding materials
include, but are not limited to cobalt, nickel, boron, molybdenum,
niobium, chromium, iron, and alloys of these elements. Various
alloys of such binding materials may also be used to form tungsten
carbide pellets in accordance with teachings of the present
disclosure. The weight percentage of the binding material may be
approximately four percent (4%) plus or minus one percent (1%) of
the total weight of each tungsten carbide pellet.
[0086] A mixture of tungsten carbide and binding material may be
used to form green pellets. The green pellets may then be sintered
or HIP-sintered at temperatures near the melting point of cobalt to
form either sintered or HIP-sintered tungsten carbide pellets with
an optimum weight percentage of binding material. HIP-sintering may
sometimes be referred to as "over pressure sintering" or as
"sinter-hipping."
[0087] Sintering a green pellet generally includes heating the
green pellet to a desired temperature at approximately atmospheric
pressure in a furnace with no force or pressure applied to the
green pellet. HIP-sintering a green pellet generally includes
heating the green pellet to a desired temperature in a vacuum
furnace with pressure or force applied to the green pellet.
[0088] A hot isostatic press (HIP) sintering vacuum furnace
generally uses higher pressures and lower temperatures as compared
to a conventional sintering vacuum furnace. For example, a
sinter-HIP vacuum furnace may operate at approximately 1400.degree.
C. with a pressure or force of approximately 800 psi applied to one
or more hot tungsten carbide pellets. Construction and operation of
sinter-HIP vacuum furnaces are well known. The melting point of
binding material used to form tungsten carbide pellets may
generally decrease with increased pressure. Furnaces associated
with sintering and HIP-sintering are typically able to finely
control temperature during formation of tungsten carbide
pellets.
[0089] Layers of hard material disposed at selected locations on
exterior portions of a matrix body may include tungsten carbide
particles or pellets 130 having an optimum weight percentage of
binding material in accordance with teachings of the present
disclosure. Other hard materials and/or hard particles selected
from a wide variety of metals, metal alloys, ceramic alloys, and
cermets may be used to form layers 101-105 of hard material. As a
result of using tungsten carbide particles 130 having an optimum
weight percentage of binding material, layers 101-105 of hard
material may have significantly enhanced abrasion, erosion, wear,
impact, and/or fatigue resistance.
[0090] A plurality of tungsten carbide pellets 130 having an
optimum weight percentage of binding material in accordance with
teachings of the present disclosure may be dispersed within filler
78. A plurality of coated diamond particles 140 may also be
dispersed within filler 78 of welding rod 71a. Conventional
tungsten carbide particles or pellets (not expressly shown) which
do not have an optimum weight percentage of binder material may
sometimes be included as part of filler 78. For some applications,
filler 78 may include a deoxidizer and a temporary resin binder.
Examples of deoxidizers satisfactory for use with the present
disclosure may include various alloys of iron, manganese, and
silicon.
[0091] For some applications, the weight of welding rods 71 and/or
71a may be approximately fifty-five percent to eighty percent
filler 78 and twenty to thirty percent or more steel tube 76.
Layers of hard material formed by welding rods with less than
approximately fifty-five percent by weight of filler 78 may not
provide sufficient wear resistance. Welding rods with more than
approximately eighty percent by weight of filler 78 may be
difficult to use to form layers of hard material with desired
dimensions including thickness and/or desired configurations.
[0092] Loose material such as powders of hard material selected
from the group consisting of tungsten, niobium, vanadium,
molybdenum, silicon, titanium, tantalum, zirconium, chromium,
yttrium, boron, carbon and carbides, nitrides, oxides, or silicides
of these materials may be included as part of filler 78. The loose
material may also include a powdered mixture selected from the
group consisting of copper, nickel, iron, cobalt, and alloys of
these elements to form matrix bit body 50. Powders of materials
selected from the group consisting of metal borides, metal
carbides, metal oxides, metal nitrides, and other superhard or
superabrasive alloys may be included within filler 78. The specific
compounds and elements selected for filler 78 will generally depend
upon intended applications for the resulting matrix drill bit and
selected welding technique.
[0093] When tungsten carbide pellets 130 are mixed with other hard
particles, such as coated diamond particles 140, both types of hard
particles may have approximately the same density. One of the
technical benefits of the present disclosure may include varying
the percentage of binding materials associated with tungsten
carbide pellets 130 and thus the density of tungsten carbide
pellets 130 to ensure compatibility with coated diamond particles
140 and/or matrix portion 146 of layers 101-105 of hard
material.
[0094] Tungsten carbide pellets 130 with or without coated diamond
particles 140 and selected loose materials may be included as part
of a continuous welding rod (not expressly shown), composite
welding rod (not expressly shown), core wire (not expressly shown)
and/or welding rope (not expressly shown). For some applications
flexible, hard facing ropes may be satisfactorily used to form one
or more layers of hard material at selected locations on exterior
portions of a new matrix drill bit or a used (dull) matrix drill
bit. Flexible welding rope or hard facing rope may be available
from several vendors including, but not limited to, Technogenia,
Inc. having offices in Conroe, Tex. and Atlanta, Ga. Some welding
ropes may include a central small diameter nickel wire coated with
a thick layer of hard particles and matrix material such shown in
FIGS. 3B and 4B.
[0095] Oxyacetylene welding, atomic hydrogen welding techniques,
tungsten inert gas (TIG-GTA), stick welding, SMAW and/or GMAW
welding techniques may be satisfactorily used to form layers of
hard material at selected locations on used matrix drill bit or new
matrix bit bodies using welding rods, welding rope, etc.
[0096] For some applications, a mixture of tungsten carbide pellets
130 and coated diamond particles 140 may be blended and thermally
sprayed onto select portions of a matrix body of a matrix body
using techniques well known in the art. A laser may then be used to
densify and fuse the resulting powdered mixture at selected
locations on exterior portions of the matrix body. U.S. Pat. No.
4,781,770 entitled "A process For Laser Hardfacing Drill Bit Cones
Having Hard Cutter Inserts" shows one process satisfactory for use
with the present disclosure.
[0097] Layers of hard material 103 and 104 as shown in FIG. 3C and
FIG. 4C may include a plurality of tungsten carbide particles 130
embedded or encapsulated in matrix portions 146 and 146a. Various
materials including cobalt, copper, nickel, iron, and alloys of
these elements may be used to form matrix portions 146 and 146a.
For some applications matrix portions 146 and 146a may be similar
to and operable to bond with adjacent portion of matrix 131.
[0098] Coated diamond particles or encrusted diamond particles 140
may be formed using various techniques such as those described in
U.S. Pat. No. 4,770,907 entitled "Method for Forming Metal-Coated
Abrasive Grain Granules" and U.S. Pat. No. 5,405,573 entitled
"Diamond Pellets and Saw Blade Segments Made Therewith."
[0099] Coated diamond particles 140 may include diamond 144 with
coating 142 disposed thereon. Materials used to form coating 142
may be metallurgically and chemically compatible with materials
used to form both matrix portion 146a and binder for tungsten
carbide pellets 130. For many applications, the same material or
materials used to form coating 142 will also be used to form matrix
portion 146a and associated matrix bit body.
[0100] Metallurgical bonds may be formed between coating 142 of
each coated diamond particle 140 and matrix portion 146a. As a
result of such metallurgical or chemical bonds coated diamond
particles 140 may remain fixed within layers of hard material
101-105 until the adjacent tungsten carbide pellets 130 and/or
other hard materials in matrix portion 146a have been worn away.
Coated diamond particles 140 may provide high levels of abrasion,
erosion and wear resistance to protect an associated matrix body as
compared with hardfacing formed from only matrix portion 146a and
tungsten carbide pellets 130. High abrasion, erosion, wear, impact,
and/or fatigue resistance of the newly exposed tungsten carbide
pellets 130 and/or coated diamond particles 140 may increase
overall abrasion, erosion, wear, impact, and/or fatigue resistance
of layers of hard material 101-105. As surrounding matrix portion
146a continues to be worn away, additional tungsten carbide pellets
130 and/or coated diamond particles 140 may be exposed to provide
continued protection and increased useful life of an associated
matrix drill bit.
[0101] Additional information about coated or encrusted diamond
particles and other hard particles may be found in U.S. Pat. No.
6,469,278 entitled "Hardfacing Having Coated Ceramic Particles Or
Coated Particles Of Other Hard Materials;" U.S. Pat. No. 6,170,583
entitled "Inserts And Compacts Having Coated Or Encrusted Cubic
Boron Nitride Particles;" U.S. Pat. No. 6,138,779 entitled
"Hardfacing Having Coated Ceramic Particles Or Coated Particles Of
Other Hard Materials Placed On A Rotary Cone Cutter" and U.S. Pat.
No. 6,102,140 entitled "Inserts And Compacts Having Coated Or
Encrusted Diamond Particles."
[0102] The ratio of coated diamond particles 140 or other hard
particles with respect to tungsten carbide pellets 130 disposed
within layers of hard material 101-105 may be varied to provide
desired erosion, abrasion, wear, impact, and fatigue resistance for
an associated matrix bit body depending upon anticipated downhole
operating environment. For some extremely harsh environments, the
ratio of coated diamond particles 140 to tungsten carbide particles
130 may be 10:1. For other downhole drilling environments, the
ratio may be substantially reversed.
[0103] Tube rod welding with an oxyacetylene torch (not shown) may
be satisfactorily used to form metallurgical bonds between layers
of hard material and adjacent portions of matrix bit body 50 and
metallurgical and/or mechanical bonds between matrix portion 146
and tungsten carbide pellets 130. For other applications, laser
welding techniques may be used to form layers of hard material on
exterior portions of a matrix body.
[0104] Mold assembly 200a as shown in FIG. 5 may include several
components such as mold 203a, gauge ring or connector ring 204a,
and funnel 220a. Mold 203a, gauge ring 204a, and funnel 220a may be
formed from graphite or other suitable materials. Various
techniques may be used including, but not limited to, machining a
graphite blank to form mold cavity 252a having a negative profile
or a reverse profile of desired exterior features for a resulting
fixed cutter drill bit. For example mold cavity 204a may have a
negative profile which corresponds with the exterior profile or
configuration of blades 54 and junk slots 56 as shown in FIG.
1.
[0105] Various types of temporary displacement materials and mold
insert may be satisfactorily installed within mold cavity 252a
depending on the desired configuration of a resulting matrix drill
bit. For example mold inserts 70a may be formed from various
materials such as consolidated sand and/or graphite may be disposed
within mold cavity 104. Various resins may be satisfactorily used
to form consolidated sand. Mold inserts 70a may have configurations
and dimensions corresponding with desired features of matrix bit
body 50 such as recess 70 formed in exterior portion 58 of blades
54. The dimensions and configuration of mold inserts 70a and
associated recesses 70 may be selected to correspond with desired
dimensions and configuration for resulting gage pads (not expressly
shown) on respective blades 54.
[0106] Matrix bit body 50 may include relatively large fluid cavity
or chamber 32 with multiple fluid flow passageways 72 and 74
extending therefrom. See FIG. 6. As shown in FIG. 5, displacement
materials such as consolidated sand may be installed within mold
assembly 200a at desired locations to form portions of cavity 32
and fluid flow passages 72 and 74 extending therefrom. The
orientation and configuration of consolidated sand legs 172 and 174
may be selected to correspond with desired locations and
configurations of associated fluid flow passageways 72 and 74
communicating from cavity 32 to respective nozzles 68.
[0107] A relatively large, generally cylindrically shaped
consolidated sand core 150 may be placed on the legs 172 and 174.
The number of legs extending from sand core 150 will depend upon
the desired number of nozzle openings in a resulting matrix bit
body.
[0108] After desired displacement materials, including core 150 and
legs 172 and 174, have been installed within mold assembly 200a,
matrix material 131 having desired characteristics for matrix bit
body 50 may be placed within mold assembly 200a. The present
disclosure allows the use of matrix materials having
characteristics of toughness and wear resistance for forming a fix
cutter drill bit or drag bit.
[0109] A generally hollow, cylindrical bit blank 36 may then be
placed within mold assembly 200a. Bit blank 36 preferably includes
inside diameter 37 which is larger than the outside diameter of
sand core 150. Various fixtures (not expressly shown) may be used
to position bit blank 36 within mold assembly 200a at a desired
location spaced from first matrix material 131.
[0110] For some applications second matrix material 132 such as
tungsten powder may then be placed in mold assembly 200a between
exterior portions of bit blank 36 and adjacent interior portions of
funnel 220a. Second matrix material 132 may be a relatively soft
powder which forms a matrix that may subsequently be machined to
provide a desired exterior configuration and transition between
matrix bit body 50 and bit blank 36. See FIG. 6. Second matrix
material 132 may sometimes be described as an "infiltrated
machinable powder."
[0111] Matrix material 131 may be cemented carbides and/or
spherical carbides as previously discussed. Alloys of cobalt, iron,
and/or nickel may be used to form cemented carbides and/or
spherical carbides. For some matrix drill bit designs an alloy
concentration of approximately six percent in the first matrix
material may provide optimum results. Alloy concentrations between
three percent and six percent and between approximately six percent
and fifteen percent may also be satisfactory for some matrix drill
bit designs. However, alloy concentrations greater than
approximately fifteen percent and alloy concentrations less than
approximately three percent may result in less than optimum
characteristics of a resulting matrix bit body.
[0112] A typical infiltration process for forming matrix bit body
50 may begin by forming mold assembly 200a. Gage ring 204a may be
threaded onto the top of mold 203a. Funnel 220a may be threaded
onto the top of gage ring 204a to extend mold assembly 200a to a
desired height to hold previously described matrix materials and
binder material. Displacement materials such as, but not limited
to, mold inserts 70a, legs 172 and 174, and sand core 150 may then
be loaded into mold assembly 200a if not previously placed in mold
cavity 252a. Matrix materials 131 and 132 and bit blank 36 may be
loaded into mold assembly 200a as previously described.
[0113] As mold assemblies 200 or 200a are being filled with matrix
materials, a series of vibration cycles may be induced in each mold
assembly 200 or 200a to assist desired distribution of each layer
or zone of matrix materials 131 and 132. Vibrations help to ensure
consistent density of each layer of matrix materials 131 and 132
within respective ranges required to achieve desired
characteristics for matrix bit body 50.
[0114] Binder material 160 may be placed on top of layer 132, bit
blank 36 and core 150. Binder material 160 may be covered with a
flux layer (not expressly shown). A cover or lid (not expressly
shown) may be placed over mold assembly 200a. Mold assembly 200a
and materials disposed therein may be preheated and then placed in
a furnace (not expressly shown). When the furnace temperature
reaches the melting point of binder material 160, liquid binder
material 160 may infiltrate matrix materials 131 and 132 and layer
101-105 of hard material. See FIG. 2A.
[0115] Mold assembly 200a may then be removed from the furnace and
cooled at a controlled rate. Once cooled, mold assembly 200a may be
broken away to expose matrix bit body 50. See for example FIG.
6.
[0116] Although the present disclosure has been described with
several embodiments, various changes and modifications may be
suggested to one skilled in the art. It is intended that the
present disclosure encompass such changes and modifications as fall
within the scope of the present appended claims.
* * * * *