U.S. patent application number 10/455281 was filed with the patent office on 2004-12-09 for drill bit body with multiple binders.
Invention is credited to Kembaiyan, Kumar T., Oldham, Thomas W..
Application Number | 20040244540 10/455281 |
Document ID | / |
Family ID | 33489920 |
Filed Date | 2004-12-09 |
United States Patent
Application |
20040244540 |
Kind Code |
A1 |
Oldham, Thomas W. ; et
al. |
December 9, 2004 |
Drill bit body with multiple binders
Abstract
A structural matrix drill bit body having different binder
materials in different spatial locations as well as a method for
forming the same, is provided. The different binder materials
provide different functional properties to the different spatial
locations of the drill bit body. The method for forming such a
structural matrix body includes providing a matrix material within
a mold, then infiltrating the matrix material with at least two
binder materials which provide different functional properties in
combination with the material. The arrangement is then heated and
the heating process causes the different binder materials to
infiltrate different spatial locations of the drill bit body.
Inventors: |
Oldham, Thomas W.; (The
Woodlands, TX) ; Kembaiyan, Kumar T.; (The Woodlands,
TX) |
Correspondence
Address: |
CHRISTIE, PARKER & HALE, LLP
P.O. Box 7068
Pasadena
CA
91109-7068
US
|
Family ID: |
33489920 |
Appl. No.: |
10/455281 |
Filed: |
June 5, 2003 |
Current U.S.
Class: |
76/108.2 ;
76/108.1 |
Current CPC
Class: |
C22C 1/1036 20130101;
C22C 2204/00 20130101; B22F 2005/001 20130101; B22F 2999/00
20130101; B22F 2998/10 20130101; B22F 7/06 20130101; B22F 2998/10
20130101; B22F 7/06 20130101; C22C 1/1036 20130101; C22C 1/1036
20130101; B22F 2999/00 20130101; B22F 1/052 20220101; C22C 29/08
20130101; B22F 2999/00 20130101; B22F 1/052 20220101; C22C 29/08
20130101 |
Class at
Publication: |
076/108.2 ;
076/108.1 |
International
Class: |
B21K 005/04 |
Claims
What is claimed is:
1. A method for forming a bit body comprising: providing a mold;
disposing matrix material within said mold; introducing a first
binder material and a second binder material to said mold; and
heating to form a bit body.
2. The method as in claim 1, wherein said heating causes said first
binder material to infiltrate a first portion of said matrix
material and said second binder material to infiltrate a second
portion of said matrix material.
3. The method as in claim 2, wherein said first portion and said
second portion are different.
4. The method as in claim 2, wherein said second binder material
has a higher melting point than said first binder material and said
second portion is superjacent said first portion.
5. The method as in claim 1, wherein said heating causes said first
binder material to infiltrate a first portion and a second portion
of said matrix material and said heating causes said second binder
material to infiltrate substantially only the second portion of
said matrix material.
6. The method as in claim 1, wherein said heating causes said first
binder material to infiltrate a first portion of said matrix
material and provide at least a first functional property and said
second binder material to infiltrate a second portion of said
matrix material and provide at least a second functional property
being different from the first property, each of said first
functional property and said second functional selected from the
group consisting of a desirable degree of braze strength, a
desirable degree of erosion resistance, a desirable degree of
abrasion resistance, a desirable degree of steel bond strength, a
desirable degree of toughness, a desirable degree of hardness, and
a desirable degree of transverse rupture strength.
7. The method as in claim 1, further comprising introducing a third
binder material to said mold prior to said heating.
8. The method as in claim 1, further comprising disposing diamond
pieces within said mold prior to said disposing matrix
material.
9. The method as in claim 1, wherein said disposing and said
introducing comprise intermixing said first binder material and
said second binder material within said matrix material.
10. The method as in claim 1, further comprising providing a
mixture of polycrystalline diamond and one of said matrix material
and a further matrix material, in locations within said mold.
11. The method as in claim 1, in which said introducing a first
binder material and a second binder material comprises providing a
mixture of said first binder material and said second binder
material over said matrix material.
12. The method as in claim 1, in which said first binder material
has a first melting point and said second binder material has a
second melting point, said second melting point being greater than
said first melting point by at least 100.degree. F.
13. The method as in claim 12, further comprising introducing a
third binder material to said mold, said third binder material
having a third melting point being greater than said second melting
point by at least 100.degree. F.
14. The method as in claim 1, wherein said heating comprises
initially heating to a first temperature sufficient to cause said
first binder material to infiltrate said matrix material, then
heating to a second temperature sufficient to cause said second
binder material to infiltrate said matrix material.
15. The method as in claim 1, wherein said first binder material
has a melting point of about 1650.degree. F. and said second binder
material has a melting point of about 1800.degree. F.
16. The method as in claim 1, wherein said first binder material
comprises a first alloy comprising manganese in a range of about 0
to 25% by weight, nickel in a range of about 0 to 15% by weight,
zinc in a range of about 3 to 20% by weight, tin in a range of
about 6 to 7% by weight, and copper in a range of about 24 to 96%
by weight of said first alloy composition, and said second binder
material comprises a second alloy comprising manganese in a range
of about 0 to 24% by weight, nickel in a range of about 0 to 15% by
weight, zinc in a range of about 3 to 20% by weight, and copper in
a range of about 30 to 98% by weight of said second alloy
composition.
17. The method as in claim 1, in which said first binder material
and said second binder material provide different properties to
said bit body in combination with said matrix material.
18. The method as in claim 1, wherein said disposing a matrix
material comprises disposing multiple grades of a tungsten carbide
matrix material within said mold.
19. The method as in claim 1, wherein said mold includes
displacements that form cavities that extend into said bit
body.
20. The method as in claim 19, wherein said heating causes said
first binder material to infiltrate a first portion of said matrix
material that includes said displacements and further causes said
second binder material to infiltrate a second portion of said
matrix material, said first portion being different from said
second portion.
21. The method as in claim 1, wherein said introducing a first
binder material and a second binder material to said mold comprises
providing said first binder material over said matrix material and
providing said second binder material over said matrix
material.
22. The method as in claim 21, further comprising further heating
after said providing a first binder material and prior to said
providing a second binder material.
23. The method as in claim 21, wherein said providing a first
binder material comprises forming a first layer of said first
binder material over said matrix material and said providing a
second binder material comprises forming a second layer of said
second binder material over said first layer.
24. The method as in claim 23, in which said first binder material
has a first melting point and said second binder material has a
second melting point that is higher than said first melting
point.
25. A method for tailoring portions of a bit body comprising:
providing matrix material within a mold; infiltrating a first
portion of said matrix material with a first binder material; and
infiltrating a second portion of said matrix material with a second
binder material.
26. The method as in claim 25, wherein said infiltrating a first
portion of said matrix material provides a first property selected
from the group consisting of abrasion resistance, toughness,
hardness, erosion resistance, braze strength, and bond strength to
said bit body, and said infiltrating a second portion of said
matrix material provides a second property selected from the group
consisting of abrasion resistance, toughness, hardness, erosion
resistance, braze strength, and bond strength, to said bit body,
said first property being different than said second property.
27. The method as in claim 25, wherein said infiltrating a first
portion and said infiltrating a second portion comprise heating
said mold, said matrix material and said first and second binder
materials.
28. The method as in claim 27, wherein said heating operation
includes initially heating to a first temperature sufficient to
cause said infiltrating a first portion of said matrix material,
then heating to a second temperature sufficient to cause said
infiltrating a second portion of said matrix material.
29. A drill bit having a bit body comprising a matrix material and
having a first region including a first binder material therein and
a second region including a second binder material therein.
30. The drill bit as in claim 29, wherein said first region
includes a surface of said bit body and said second region includes
a core of said bit body.
31. The drill bit as in claim 30, wherein said first region
includes pockets extending into said bit body and adapted for
receiving corresponding cutting elements.
32. The drill bit as in claim 29, wherein said first region
provides different brazing properties than said second region.
33. The drill bit as in claim 29, wherein at least part of said bit
body is formed of said matrix material in combination with
polycrystalline diamond.
34. The drill bit as in claim 29, wherein said first region has a
first functional property and said second region has a second
functional property, said second functional property being
different from said first property, each of said first functional
property and said second functional selected from the group
consisting of a desirable degree of braze strength, a desirable
degree of erosion resistance, a desirable degree of abrasion
resistance, a desirable degree of steel bond strength, a desirable
degree of toughness, a desirable degree of hardness, and a
desirable degree of transverse rupture strength.
35. The drill bit in claim 29, in which said matrix material
comprises multiple types or grades of tungsten carbide.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to co-pending U.S. patent
application Ser. No. ______, entitled "Improved Bonding of Cutters
in Diamond Drill Bits", filed ______, and Ser. No. ______, entitled
"Bit Body Formed of Multiple Matrix Materials and Method for Making
the Same", filed ______, the contents of each of which are hereby
incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates, most generally, to a
composition for a matrix body of a drill bit and other cutting or
drilling tools, and a method for forming the same.
BACKGROUND OF THE INVENTION
[0003] Various types of earth boring bits are used in various
applications in today's earth drilling industry. The earth boring
bits may be formed to include various shapes. Depending on the
application, the drill bits may contain natural or synthetic
diamonds, polycrystalline diamond (PCD) or grit hot-pressed (GHI)
inserts, diamond-impregnated regions or combinations thereof, for
drilling through earthen formations. The inserts, also known as
cutting elements, are bonded to the bit body, often by brazing. The
bit body is typically formed of a matrix material such as tungsten
carbide, which is bonded into solid form by fusing a metallic
binder material and the matrix material. This is commonly referred
to as "infiltrating" the matrix material. To form the bit body, the
tungsten carbide or other matrix material is disposed within a mold
which is commonly formed of graphite and may be machined into any
of various suitable shapes. The mold may be shaped to form a drill
bit body that includes blades, teeth or other structural
features.
[0004] Various forms of powdered tungsten carbide, for example, may
be used as the matrix material and placed in the mold. The metal
binder material, which may be composed of a single metal or
metallic alloy, is typically placed over the tungsten carbide, then
heated in a furnace to the flow or infiltration temperature of the
binder material, at which the melted binder material infiltrates
the tungsten carbide or other matrix material. By infiltration, it
is meant that the molten binder material flows through the spaces
between the matrix material grains by means of capillary action.
More particularly, the infiltration process bonds the grains of the
matrix material to each other and also bonds the matrix material to
other structures that it contacts.
[0005] Natural or synthetic diamonds may be inserted into the mold
prior to heating the matrix/binder mixture. Such diamonds become
cemented to the bit body during infiltration and subsequent
cooling. In such case, the drill bit is formed to include natural
or synthetic diamonds. Alternatively, a bit may be formed by
placing a mixture of tungsten carbide and diamond powder in desired
locations within the mold prior to heating. In such case, a drill
bit is formed having regions impregnated with diamond crystals.
Inserts may then be joined to the bit body after the bit body is
formed. PCD inserts may be joined to pockets or other receiving
shapes that extend into the bit body, by brazing or other suitable
means. Similarly, the grit hot-pressed inserts (GHIs) may be joined
to holes that extend into the bit body, by brazing or other
suitable means.
[0006] A steel or other metallic blank may be suspended within the
mold. The blanks may be of various shapes. During the heating
process, during which infiltration occurs, the molten binder
materials also cause the matrix material to bond to the steel or
other metallic blank. After formation of the bit body, a protruding
section of the steel or other metallic blank may be welded to a
second component called an upper section. The upper section
typically has a tapered portion that is threaded onto a drilling
string.
[0007] The chemical composition of the matrix material and the
binder material are selected to provide a finished bit body having
desired mechanical properties. Once a particular matrix material is
chosen, the binder material then determines the mechanical
properties of the finished bit body. These mechanical properties
include transverse rupture strength (TRS), toughness (resistance to
impact-type fracture), wear resistance (including resistance to
erosion from rapidly flowing drilling fluid and abrasion from rock
formations), steel bond strength between the matrix and steel
reinforcing elements such as a steel blank, and strength of the
bond (braze strength) between the finished body material and the
PDC or GHI inserts.
[0008] The metallic binder material may be a single metal or a
metallic alloy. According to conventional drill bit manufacturing,
a single binder material is added to the matrix material to provide
a property or one set of properties throughout the bit body. It
would, however, be desirable to optimize the overall structure of
the drill bit by providing different mechanical properties to the
different portions of the drill bit body, in essence tailoring the
bit body. For example, superior wear resistance is especially
desirable at regions around the cutting elements, high strength and
toughness are especially desirable at the bit blades and throughout
the bulk of the bit body, and superior braze strength is desirable
in the pockets or holes to which cutting inserts are brazed. These
properties may be mutually exclusive if they are provided by
different binder materials, for a given matrix material system. The
choice of the single binder material therefore represents a
compromise as the single binder material must be chosen to produce
one or more of the properties, generally at the expense of another
desirable property or properties.
[0009] It is therefore a shortcoming of the conventional art, that
a drill bit cannot be formed to include different desirable
mechanical properties in different regions of the drill bit. The
present invention addresses these shortcomings.
SUMMARY OF THE INVENTION
[0010] The present invention is directed to a structural body such
as a drill bit that includes different binder materials and
therefore different properties, in different spatial locations of
the structural body. The present invention also provides methods
for forming such a structural body.
[0011] In an exemplary embodiment, the present invention provides a
drill bit comprising a matrix material and having a first region
including a first binder material therein, and a second region
including a second binder material therein. The first binder
material and second binder material provide different functional
properties to the structural body in combination with the matrix
material.
[0012] In one exemplary embodiment, a method for forming such a
drill bit body is provided. The method comprises providing a mold
and disposing matrix material within the mold. First and second
binder materials are then introduced to the mold and the
arrangement is then heated to form a bit body. The first and second
binder materials are chosen to have different melting points, and
the heating causes the first and second binder materials to migrate
to different spatial locations within the matrix material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The invention is best understood from the following detailed
description when read in conjunction with the accompanying
drawings. It is emphasized that, according to common practice, the
various features of the drawing are not to scale. On the contrary,
the dimensions of the various features may be arbitrarily expanded
or reduced for clarity. Like numerals denote like features
throughout the specification and drawings. Included are the
following figures:
[0014] FIG. 1 is a perspective view of an exemplary drill bit of
the present invention, in partial cross-section;
[0015] FIG. 2 is a cross-sectional schematic view of a mold and
materials for forming a drill bit according to one exemplary
embodiment of the present invention;
[0016] FIG. 3 is a cross-sectional schematic view showing the
arrangement of FIG. 2 after heating; and
[0017] FIG. 4 is another cross-sectional schematic view of a mold
and materials for forming a drill bit according to another
exemplary embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The present invention provides a structural body of matrix
material, such as a drill bit body, in which different portions of
the bit body are formed of different infiltration/binder materials
in combination with a matrix material. In combination with the
matrix material, the different infiltration/binder materials
provide different desirable mechanical properties to the structural
body. For brevity, the infiltration/binder materials are
hereinafter referred to simply as binder materials. The mechanical
properties are provided to the different spatial locations where
they are most advantageous. The present invention also provides a
method for forming the structural body using multiple binder
materials. The method includes heating to cause the multiple binder
materials to migrate to the different spatial locations of the
structural body where the properties they provide are most needed.
Although the present invention may be used to form various
structural bodies of matrix material, the following discussion is
directed to the exemplary embodiment in which the structural body
is a drill bit body. The drill bit body embodiment is provided to
be illustrative, and not restrictive of the present invention.
[0019] FIG. 1 shows an exemplary drill bit in partial
cross-section. More specifically, FIG. 1 shows drill bit 2 having
bit body 4 and including core 6. Internal to bit body 4 is opening
8 to which is attached a steel or other metal blank. For clarity,
the steel or other metal blank is not illustrated in FIG. 1, but it
should be understood that a metal blank will occupy opening 8 upon
formation of the bit body 4. The bit body is formed bonded to the
metal blank, as will be shown in subsequent figures. The
configuration of drill bit 2 shown in FIG. 1 is intended to be
exemplary only.
[0020] Drill bit 2 includes exemplary blades 10 and a plurality of
pockets 12 to receive cutting elements 14. Cutting elements 14 each
include cutting face 13 which may be formed of polycrystalline
diamond (PCD) or polycrystalline cubic boron nitride (PCBN), or a
mixture thereof, in exemplary embodiments.
[0021] Different "regions" of drill bit 2 are apparent from FIG. 1.
The regions include the bulk of the bit body including core 6,
blades 10, blade surface 20, other surfaces 21 (namely the bit
gage), pockets 12, surface regions 16 adjacent pockets 12, and the
interface region 18 which interfaces with the metallic blank
(opening 8 in the illustration of FIG. 1). Such "regions" are
arbitrarily designated for illustrative purposes. These and other
differently designated regions of a bit body may be formed to
include different functional properties or sets of functional
properties to the portion of the solid drill bit body that it
forms. These functional properties include, but are not limited to
a desirable degree of transverse rupture strength (TRS), a
desirable degree of toughness (resistance to impact-type fracture),
a desirable degree of wear resistance (including resistance to
erosion from rapidly flowing drilling fluid and abrasion from rock
formations), a desirable degree of hardness, a desirable degree of
abrasion resistance, a desirable degree of steel bond strength
between the matrix material and steel reinforcing elements such as
a metallic blank, and a desirable degree of braze strength between
the finished body material and a PCD insert, GHI insert, or other
cutting element brazed to the bit body. By "functional property",
it is meant that the mechanical property of interest, is exhibited
to a degree such that the portion of the solid drill bit body is
considered to demonstrate a degree of the mechanical property that
is advantageous and desirable for its application.
[0022] Referring to drill bit 2 of FIG. 1, it is desirable to form
outer surfaces 20 and 21 to posses good erosion resistance,
hardness and strength because they are exposed to various drilling
fluids. Moreover, it is desirable to form core 6 to posses superior
toughness as it forms the bulk of the bit body. Pockets 12, which
receive cutting elements 14, should be formed to provide for
superior braze strength since cutting elements 14 will be brazed to
such pockets. Interface region 18 should be formed to provide
superior metal bond strength because a steel or other metallic
blank will be bonded to this region. It is also desirable to form
surface regions 16 that are near pockets 12 on blades 10, to have
superior wear resistance since they are exposed to the earth
formations during drilling and may therefore endure severe
abrasion. The regions of the drill bit and the desirable properties
associated therewith, are intended to be exemplary only. Different
"regions" may be designated to advantageously include different
properties, in other exemplary embodiments.
[0023] In an exemplary embodiment, the multiple binder materials
are used to advantageously provide different desired mechanical or
functional properties (as described above) to different exemplary
regions of a structural body such as drill bit 2. It should be
emphasized that drill bit 2 illustrated in FIG. 1 is intended to be
exemplary only and various other drill bits having various other
shapes including different blade configurations and cutting element
locations, and therefore other "regions", may be used in other
exemplary embodiments. The drill bits may be PDC or other drag
bits, or other earth boring devices.
[0024] The mechanical/functional properties provided to the drill
bit body are a function of the combination of the matrix material
and the binder material. For a given matrix material, the binder
material determines the different properties. The effect of the
various binder materials may differ when different matrix materials
are used. The present invention is applicable to matrix materials
systems formed of various matrix materials or combinations of
matrix materials. For descriptive purposes, the following
discussion is directed to an exemplary system in which the matrix
material is tungsten carbide. The tungsten carbide matrix material
may represent a single type of tungsten carbide or a mixture of
various types of tungsten carbide.
[0025] FIG. 2 is a schematic cross-sectional view showing matrix
material 36 disposed within mold 30. Mold 30 defines the shape of
the bit body and will generally be shaped to produce blades, teeth
and other cutting surfaces in the formed bit body. Mold 30 is
typically formed of graphite and may also include displacements 35
which produce pockets or other indentations that extend into the
formed bit body, for accommodating PCD inserts or other cutting
elements which are joined to the pockets by brazing. In an
exemplary embodiment, diamond pieces 34 may be added along surface
32 of mold 30 prior to the addition of matrix material 36. Diamond
pieces 34 may be natural or synthetic diamonds. If such diamonds
are added, the bit body will be formed to include these diamond
pieces on its surface upon solidification. Steel blank 40 is
suspended within mold 30. Steel blank 40 is exemplary only and
other metal blanks may be used in other exemplary embodiments.
[0026] Matrix material 36 is tungsten carbide and may represent a
single form of tungsten carbide or a mixture of various types of
tungsten carbide powders, in various exemplary embodiments. Drill
bits formed of tungsten carbide, WC, or other similarly hard metal
matrix materials, have the advantage of higher wear and erosion
resistance. After optional diamonds 34 are positioned within mold
30, the mold is packed with matrix material powder.
[0027] The various types of tungsten carbide may include
macro-crystalline tungsten carbide, cast tungsten carbide,
carburized tungsten carbide and sintered tungsten carbide.
Macro-crystalline tungsten carbide is essentially a stoichiometric
tungsten carbide (i.e., WC) that is, for the most part, in the form
of single crystals. Some large crystals of macro-crystalline
tungsten carbide are bi-crystals. Cast tungsten carbide is a
eutectic two-phase carbide composed of WC and W.sub.2C. Carburized
tungsten carbide is a type of tungsten carbide that is different
from macro-crystalline tungsten carbide, cast tungsten carbide, and
cemented or sintered tungsten carbide. Carburized tungsten carbide
is a product of the solid-state diffusion of carbon into tungsten
metal at high temperatures in a protective atmosphere. Carburized
tungsten carbide grains are generally multi-crystalline, i.e., they
are composed of tungsten carbide agglomerates. The agglomerates
form grains that are larger than the individual tungsten carbide
crystals. Sintered tungsten carbide signifies tungsten carbide
particles that have been pre-sintered to include cementing or
binder agents such as cobalt. In one embodiment, matrix material 36
may be one of the above-listed types of tungsten carbide matrix
material, while in other exemplary embodiments, multiple grades or
more than one of the aforementioned types of tungsten carbide may
be provided as a mixture to form a relatively homogenous matrix
material 36 within mold 30. In another exemplary embodiment, the
different grades or types of tungsten carbide matrix material may
be disposed at different locations within mold 30. In yet another
exemplary embodiment, different mixtures of matrix materials may be
disposed in different locations within mold 30.
[0028] After the tungsten carbide matrix material 36 is disposed
within mold 30, first binder material 46 is provided over upper
surface 38 of matrix material 36 according to the exemplary
embodiment illustrated in FIG. 2. Second binder material 48 is also
added over upper surface 38 and in the illustrated exemplary
embodiment, second binder material 48 is a layer disposed over a
layer of first binder material 46. Each of the binder materials may
be provided in the form of small slugs placed over matrix material
36 and around steel blank 40. In other embodiments, the binder
materials may be provided in other forms such as a powder. In the
illustrated embodiment, the binder materials are introduced into
mold 30.
[0029] The two binder materials 46 and 48 are chosen to have
different melting points and to provide different
mechanical/functional properties to the drill bit as formed. In one
exemplary embodiment, the two binder materials may include melting
points that differ by at least 100.degree. F., but other melting
point variations may be used in other embodiments. In one exemplary
embodiment, the binder material with the higher melting point may
be formed as second binder material 48, in a layer over first
binder material 46. According to another exemplary embodiment, the
higher melting point binder material may be first binder material
46 adjacent matrix material 36. According to still another
exemplary embodiment (as will be shown in FIG. 4) the two matrix
materials may be intermixed to form a single layer.
[0030] The binder material may be a metal such as cobalt, iron,
copper, nickel, manganese, zinc, tin and/or mixtures or alloys
thereof. Binder material alloys are commonly formed to include at
least copper and nickel. Exemplary binder alloys are disclosed in
U.S. Pat. No. 6,461,401, issued on Oct. 8, 2002, the contents of
which are herein incorporated by reference. One exemplary binder
alloy includes a melting point of about 1635.degree. F. and
includes nickel in the range of about 0-15% by weight, manganese in
the range of about 0-25% by weight, zinc in the range of about
3-20% by weight, tin in the range of more than 1% to about 10% by
weight, and copper in the range of about 24-96% by weight. Another
exemplary binder alloy includes manganese in a range of about 0-24%
by weight, nickel in a range of about 0-15% by weight, zinc in a
range of about 3-20% by weight, and copper in a range of about
30-98% by weight and includes a melting point of about 1800.degree.
F. Many other different binder material alloys are known in the
art. Mixtures most commonly used for commercial purposes, including
diamond drill bit making, are described in a publication entitled
Matrix Powders for Diamond Tools, Kennametal Inc., Latrobe, Pa.
(1989).
[0031] One commonly used binder alloy has a composition by weight
of about 52% copper, 15% nickel, 23% manganese, and 9% zinc. This
exemplary alloy has a melting temperature of about 1800.degree. F.
(968.degree. C.) and an infiltration temperature of about
2050.degree. F. (1162.degree. C.). Other known alloys use
combinations of copper, nickel and zinc, or copper, nickel and up
to about 1% tin by weight. The aforementioned binder materials are
intended to be exemplary, as various other binder materials and
binder alloys formed of different materials and having different
melting points, may be used in other exemplary embodiments.
[0032] Each binder material is known to provide a distinct property
or properties to the particular matrix material which it
infiltrates. The binder materials are selected to have different
melting points so that the lower melting point binder material
melts and infiltrates the matrix material first, and the higher
melting point binder material melts and infiltrates the matrix
material second. In the illustrated embodiment, the different
melting points, in combination with the effects of gravity, enable
the lower melting point binder material to migrate to a lower
position within the mold than the binder material with the higher
melting point.
[0033] According to one exemplary method of the present invention,
the high and low melting point binder materials are added over top
surface 38 of matrix material 36, either as a mixture or a
plurality of layers, and the mold and its contents are heated. Such
heating may alternatively be referred to as sintering. The low and
high melting point binder materials have correspondingly relative
flow/infiltration temperatures. The exemplary method also includes
heating past the melting and flow/infiltration temperatures of the
binder materials. The lower melting point binder material melts and
begins to infiltrate matrix material 36 first (after the
flow/infiltration temperature has been reached). The heating
continues as the high melting point binder material eventually
melts and also infiltrates matrix material 36 when its
flow/infiltration temperature has been reached. Since the lower
melting point binder material melts and infiltrates first, gravity
causes the lower melting point binder material to begin descending
through the matrix material sooner. After the heating process, the
mold and materials therein are cooled.
[0034] FIG. 3 shows the arrangement shown in FIG. 2 after heating
has caused the binder materials to infiltrate the matrix material.
The heating time, gradient, and temperatures, as well as the
cooling gradient, are chosen such that the low melting point binder
material (which may be first binder material 46 or second binder
material 48) reaches lower region 47 of matrix material 36 within
mold 30, while the high melting point binder material does not
reach lower region 47, but, rather, remains in upper region 49. In
this manner, the lower melting point binder material and higher
melting point binder material infiltrate different spatial
locations, for example, lower region 47 and upper region 49,
respectively. The heating time, gradient and temperature may
alternatively be chosen such that some of the low melting point
binder material reaches lower region 47 while some of the low
melting point binder material remains in upper region 49 along with
the high melting point binder material.
[0035] According to one exemplary embodiment, a continuous heating
process is carried out after both of first binder material 46 and
second binder material 48 have been provided over matrix material
36. In another exemplary embodiment, after first binder material 46
is added, the arrangement is heated and second binder material 48
added during the heating process. In yet another exemplary
embodiment, second binder material 48 is not added until after
first binder material 46 has been heated to infiltrate the matrix
material and the arrangement has been cooled.
[0036] According to the various heating/cooling embodiments, a
drill bit body is formed from matrix material 36 that is
infiltrated with binder materials that bond or cement the matrix
material into solid form. The binder material also bonds the matrix
material to steel blank 40. Once the matrix material 36 is
solidified and separated from mold 30 in FIG. 3, it constitutes the
bit body.
[0037] Upper region 49 of the bit body includes core region 6 and
lower region 47 of the bit body includes surface regions such as
the surfaces of blades 51. In one exemplary embodiment, the lower
melting point binder material which migrates to lower region 47,
may be chosen to provide superior braze strength to the region
where the cutters will be joined and wear resistance to regions
near such cutters, whereas the higher melting point binder material
may be chosen to provide strength and toughness to the bit blades
and bit body including the core. In the illustrated embodiment, the
binder materials cement the matrix material and also cause optional
diamond pieces 34 to become bonded to the drill bit body at the
surface of the formed drill bit body, when the arrangement is
heated and cooled.
[0038] The mold 30 illustrated in FIG. 3, as well as lower and
upper regions 47 and 49, respectively, are intended to be exemplary
only. Furthermore the position and shape of dashed line 50, which
divides lower region 47 from upper region 49, is exemplary only. In
other exemplary embodiments, the drill bit configuration may allow
the binder materials and the heating conditions to be chosen such
that lower region 47 includes the entirety of the blades and
pockets of the exemplary drill bit. This is also determined by the
configuration of the drill bit to be formed, including the
configuration and location of the blades and locations of the
pockets.
[0039] FIG. 4 depicts another exemplary arrangement for forming a
drill bit according to another exemplary embodiment of the present
invention. Prior to the addition of matrix material 36 into mold
30, powder mixture 54 is disposed at multiple locations within mold
30 and includes a mixture of tungsten carbide and diamond crystals.
In one exemplary embodiment, powder mixture 54 may be in paste
form. In this embodiment, when the drill bit body is formed by the
heating and cooling process, the bit body is formed to include
polycrystalline diamond in regions that include powder mixture
54.
[0040] FIG. 4 also illustrates another exemplary embodiment of the
present invention. Binder material 52 is formed over top surface 38
of matrix material 36 and is a mixture of two binder materials--a
relatively high melting point binder material and a relatively low
melting point binder material. Each of the relatively low melting
point binder material and the relatively high melting point binder
material may be one of the various materials, including alloys,
discussed above. After mold 30 is provided and matrix material 36
is disposed within mold 30, the lower melting point binder material
and the higher melting point binder material are provided as a
mixture in binder layer 52, and the arrangement is then heated. The
lower melting point binder material melts first and infiltrates
first when its infiltration/flow temperature is reached, and the
higher melting point binder material melts and infiltrates later,
when its higher infiltration/flow temperature is reached. In an
exemplary embodiment, the lower melting point binder material
migrates to a lower position within the mold and therefore a
spatially different location in the formed drill bit body, than the
higher melting point binder material, which remains superjacent the
lower melting point binder material. For example, the higher
melting point binder material may infiltrate an upper region such
as upper region 49 shown in FIG. 3, while the lower melting point
binder material may infiltrate lower region 47 as shown in FIG.
3.
[0041] According to another exemplary embodiment, more than two
distinct binder materials can be used. The multiple binder
materials are chosen to have distinct melting points and therefore,
correspondingly different infiltration temperatures. The multiple
binder materials may be mixed, added in layers or blended with
matrix materials as previously described. In an exemplary
embodiment, the multiple binder materials will each include a
melting point that differs from the others by at least 100.degree.
F. The infiltration of the matrix material takes place in stages
with the lower melting point binder material reaching a lower
portion within the mold and the highest melting point binder
material remaining in an upper portion of the mold, while an
intermediate melting point binder material is interposed between
the lower and upper portions of the mold.
[0042] According to the various exemplary embodiments, after the
heating process is ceased, the arrangement is cooled using an
appropriate cooling gradient. The cooled and solidified matrix
material 36 forms a drill bit body and is removed from mold 30. The
tungsten carbide drill bit body is bonded to steel blank 40 as
formed. As formed, the drill bit body includes different
properties, discussed above, in different spatial locations. The
drill bit body may then have cutting elements joined to pockets,
holes or other cavities that extend into the bit body, by
brazing.
[0043] The preceding merely illustrates the principles of the
invention. It will thus be appreciated that those skilled in the
art will be able to devise various arrangements which, although not
explicitly described or shown herein, embody the principles of the
invention and are included within the scope and spirit.
Furthermore, all examples and conditional language recited herein
are principally intended expressly to be only for pedagogical
purposes and to aid in understanding the principles of the
invention and the concepts contributed by the inventors to
furthering the art, and are to be construed as being without
limitation to such specifically recited examples and conditions.
Moreover, all statements herein reciting principles, aspects, and
embodiments of the invention, as well as specific examples thereof,
are intended to encompass both structural and the functional
equivalents thereof. Additionally, it is intended that such
equivalents include both currently known equivalents and
equivalents developed in the future, i.e., any elements developed
that perform the same function, regardless of structure. The scope
of the present invention, therefore, is not intended to be limited
to the exemplary embodiments shown and described herein. Rather,
the scope and spirit of the present invention is embodied by the
appended claims.
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