U.S. patent application number 09/754434 was filed with the patent office on 2002-07-04 for wear resistant drill bit.
Invention is credited to Evans, Stephen M..
Application Number | 20020084111 09/754434 |
Document ID | / |
Family ID | 25034779 |
Filed Date | 2002-07-04 |
United States Patent
Application |
20020084111 |
Kind Code |
A1 |
Evans, Stephen M. |
July 4, 2002 |
Wear resistant drill bit
Abstract
A wear resistant drill bit of the matrix bodied type has a bit
body comprising a tungsten carbide material bound with a binder
material, wherein the tungsten carbide material includes at least
some tungsten carbide particles of generally spherical shape. The
tungsten carbide material includes particles having a relatively
hard central core and a softer skin. The skin includes a large
proportion of a high temperature phase of tungsten carbide.
Inventors: |
Evans, Stephen M.;
(Standish, GB) |
Correspondence
Address: |
SCHLUMBERGER OILFIELD SERVICES
JEFFREY E. DALY
7211 N. GESSNER
HOUSTON
TX
77040
US
|
Family ID: |
25034779 |
Appl. No.: |
09/754434 |
Filed: |
January 4, 2001 |
Current U.S.
Class: |
175/374 ;
76/108.2 |
Current CPC
Class: |
E21B 10/46 20130101;
B22F 2999/00 20130101; B22F 2005/001 20130101; C22C 29/08 20130101;
B22F 2998/00 20130101; B22F 2998/00 20130101; B22F 2207/07
20130101; B22F 2999/00 20130101; C22C 29/08 20130101; B22F 1/065
20220101; B22F 2999/00 20130101; B22F 1/065 20220101; C22C 29/08
20130101 |
Class at
Publication: |
175/374 ;
76/108.2 |
International
Class: |
E21B 010/36 |
Claims
What is claimed is:
1. A matrix bodied drill bit having a bit body comprising a
tungsten carbide material bound with a binder material, wherein the
tungsten carbide material includes at least some tungsten carbide
particles of generally spherical shape which have a relatively hard
central core and an outer skin of relatively low hardness.
2. The matrix bodied drill bit of claim 1, wherein the tungsten
carbide particles of generally spherical shape have a rough outside
surface with a surface area greater than that of a smooth
sphere.
3. The matrix bodied drill bit of claim 1, wherein the outer skin
includes a high temperature form of tungsten carbide which is
relatively ductile and is amenable to wetting by the binder
material.
4. A matrix bodied drill bit having a bit body comprising a
tungsten carbide material bound by a binder material, wherein the
tungsten carbide material comprises at least some particles having
a relatively hard central core and a softer, relatively ductile
outer skin.
5. The matrix bodied drill bit of claim 4, wherein the central core
has a hardness of at least 2000HV100.
6. The matrix bodied drill bit of claim 5, wherein the hardness of
the central core is approximately 2100HV100.
7. The matrix bodied drill bit of claim 4, wherein the outer skin
has a hardness falling within the range 1250-1750HV100.
8. The matrix bodied drill bit of claim 7, wherein the outer skin
has a hardness of approximately 1500HV100.
9. A matrix bodied drill bit having a bit body comprising a
tungsten carbide material bound by a binder material, wherein the
tungsten carbide material includes at least some particles which
include a high temperature phase of tungsten carbide.
10. The matrix bodied drill bit of claim 9 wherein the particles
have a generally spherical shape and a relatively hard central core
and an outer skin of relatively low hardness.
11. The matrix bodied drill bit of claim 10, wherein the particles
have a rough outside surface with a surface area greater than that
of a smooth sphere.
12. A drill bit body comprising an infiltrated matrix of a binder
material and a tungsten carbide material, wherein the tungsten
carbide material includes at least some particles which include a
high temperature phase of tungsten carbide.
13. The drill bit body of claim 12 wherein the particles have a
generally spherical shape and a relatively hard central core and an
outer skin of relatively low hardness.
14. The drill bit body of claim 13, wherein the particles have a
rough outside surface with a surface area greater than that of a
smooth sphere.
Description
BACKGROUND OF TEE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a wear resistant drill bit for use
in the formation of subterranean well bores.
[0003] 2. Description of the Related Art
[0004] In order to maximize drilling efficiency it is important to
minimize the down-time of a drilling rig which occurs when a bit
requires replacement, and the frequency with which bits require
replacement. Clearly, improving the ability of a drill bit to
withstand the wear which occurs in use will reduce the frequency of
bit replacement and so is advantageous. A number of techniques for
improving the wear resistance of a drill bit are known. For example
it is known to mount wear resistant components on the exterior of a
steel bodied drill bit, as described in U.S. Pat. No. 6,092,613, or
to apply a coating of a suitably wear resistant material to the
drill bit. These techniques are used, primarily, with drill bits
having bodies formed from cast or machined steel.
[0005] In another type of drill bit, the bit body is formed from
one or more powders secured in a matrix by a binder material.
Typically, with drill bit bodies of the matrix type, either a
macrocrystalline tungsten carbide material is used in the matrix,
or a crushed, cast tungsten carbide material is used. Both of these
materials are thought to have advantages and disadvantages.
[0006] The use of the crushed, cast material results in the
formation of matrix bit bodies of good erosion resistance but
relatively low fatigue strength. Matrix bit bodies formed using the
macrocrystalline material have a lower erosion resistance but
improved fatigue strength. By way of example, the erosion
resistance of a matrix bit body formed using the cast and crushed
material is typically approximately five times that of a body
formed using the macrocrystalline material, but has a fatigue
strength of only about 40% of that of a body formed using the
macrocrystalline material.
[0007] The reasons for these properties are thought to be that the
crushed cast tungsten carbide takes the form of a mixture of WC and
W2C whereas the macrocrystalline material consists only of WC. W2C
is harder than WC and so the crushed cast material is more capable
of withstanding abrasion or erosion than the macrocrystalline
material. Further, the cast, crushed material is made up of
particles of uneven shape with irregular and angular surfaces
giving rise to a larger surface area than the macrocrystalline
material, which is made up of crystals of a more regular, blocky
form which have smooth surfaces. As a result, the chemical or
metallurgical bond between the crushed, cast material and a binder
material is somewhat stronger than that between the
macrocrystalline material and the binder material. Mechanical
locking of the crushed cast material to the binder is also good.
These effects assist in improving the erosion resistance of a drill
bit. The fatigue strength of the crushed cast material is thought
to be lower than that of the macrocrystalline material as the
crushing process induces small cracks in the material. In use of a
drill bit, small cracks propagating through the binder to the
tungsten carbide material may be able to propagate along and extend
the cracks already present in the crushed cast tungsten carbide
material. In drill bits manufactured using the macrocrystalline
material, such cracks are not present in the tungsten carbide
material and cracks forming within the binder must pass around
rather than through the tungsten carbide material.
BRIEF SUMMARY OF THE INVENTION
[0008] It is an object of the invention to provide a drill bit
having an improved wear resistance compared to drill bits
manufactured using the materials mentioned above.
[0009] According to a first aspect of the invention there is
provided a drill bit of the matrix type having a bit body
comprising a tungsten carbide material bound with a binder
material, wherein the tungsten carbide material includes at least
some tungsten carbide particles of generally spherical shape.
[0010] The generally spherical tungsten carbide particles are
preferably of a type having a relatively hard central core and an
outer skin of relatively low hardness. The outer skin conveniently
includes a high temperature form of tungsten carbide which is
relatively ductile and is amenable to wetting by the binder
material. The outer surface of the sphere is generally quite rough,
providing a much greater surface area for bonding by the binder
than the generally smooth surfaces of crushed and macrocrystalline
tungsten carbide.
[0011] The use of particles of generally spherical form permits an
increase in the density with which the particles can be packed in a
mold during the manufacturing process. The use of particles of the
type having a relatively hard central core and a relatively soft,
ductile outer skin results in the drill bit being of good abrasion
resistance (as the core is hard) and good fatigue strength.
[0012] According to another aspect of the invention there is
provided a drill bit of the matrix type having a bit body
comprising a tungsten carbide material bound by a binder material,
wherein the tungsten carbide material comprises at least some
particles having a relatively hard central core and a softer,
relatively ductile outer skin.
[0013] The central core conveniently has a hardness of at least
2000HV100, the hardness preferably being approximately 2100HV100.
The outer skin preferably has a hardness falling within the range
1250-1750HV100, and is conveniently approximately 1500HV100.
[0014] According to another aspect of the invention there is
provided a drill bit of the matrix type having a bit body
comprising a tungsten carbide material bound by a binder material,
wherein the tungsten carbide material includes at least some
particles which include a high temperature phase of tungsten
carbide.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The invention will further be described, by way of example,
with reference to the accompanying drawings, in which:
[0016] FIG. 1 is a perspective view of a drill bit; and
[0017] FIG. 2 is a photomicrograph of the matrix of the bit body of
the drill bit illustrated in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED
EMBODIMENT
[0018] Referring to FIG. 1, the matrix bodied drill bit 8 comprises
a bit body 10 having a leading face formed with six blades
extending outwardly away from the axis of the body towards the
gauge region. The blades comprise three longer primary blades 12
alternately spaced with three shorter secondary blades 14. Between
adjacent blades there are defined fluid channels 16.
[0019] Extending side by side along each of the primary blades 12
is a plurality of primary cutters 18 and extending along each of
the secondary blades 14 is a plurality of secondary cutters 20. The
precise nature of the cutters does not form a part of the present
invention and they may be of any appropriate type. For example, as
shown, they may comprise circular preformed cutting elements brazed
to cylindrical carriers which are embedded or otherwise mounted in
the blades, the cutting elements each comprising a preformed
compact having a polycrystalline diamond front cutting table bonded
to a tungsten carbide substrate, the compact being brazed to a
cylindrical tungsten carbide carrier. Alternatively, substrate of
the preformed compact may itself be of sufficient length to be
mounted directly in the blade, the additional carrier then being
omitted.
[0020] The secondary cutters 20 may be of the same type as the
primary cutters 18 or the primary and secondary cutters may be of
different types.
[0021] Inner nozzles 22 are mounted in the surface of the bit body
and are located in a central region of the bit body 10, fairly
close to the axis of rotation of the drill bit. Each inner nozzle
22 is so located that it can deliver drilling fluid to two or more
of the channels 16, but is so orientated that it primarily delivers
drilling fluid outwardly along a channel 16 on the leading side of
one of the three primary blades 12.
[0022] In addition, outer nozzles 24 are located at the outer
extremity of each channel on the leading side of each secondary
blade 14. The outer nozzles are orientated to direct drilling fluid
inwardly along their respective channels towards the center of the
drill bit, such inwardly flowing drilling fluid becoming entrained
with the drilling fluid from the associated inner nozzle 22 so as
to flow outwardly to the gauge region again along the adjacent
channel. All the nozzles communicate with a central axial passage
(not shown) in the shank of the bit to which drilling fluid is
supplied under pressure downwardly through the drill string in
known manner.
[0023] The outer extremities of the blades 12, 14 are formed with
kickers 26 which provide part-cylindrical bearing surfaces which,
in use, bear against the surrounding wall of the bore hole and
stabilize the bit in the bore hole. Abrasion-resistant bearing
elements (not shown), of any suitable known form, are embedded in
the bearing surfaces.
[0024] Each of the channels 16 between the blades leads to a
respective junk slot 18. The junk slots extend upwardly between the
kickers 26, so that drilling fluid flowing outwardly along each
channel passes into the associated junk slot and flows upwardly,
between the bit body 10 and the surrounding formation, into the
annulus between the drill string and the wall of the bore hole.
[0025] In operation, the bit body 10 is rotated from the surface
while weight is applied to the bit body 10, causing the cutters 18,
20 on the blades 12, 14 to engage the earth, effecting a cutting or
drilling action, as is well known in the earth boring drill bit
industry. Although a particular design of a drill bit 8 is
illustrated, it would be appreciated that many different forms of
drill bits 8 may be made. These may be, but are not limited to,
matrix bodied drill bits 8 without blades, bi-center type drill
bits, or drill bits 8 with natural or synthetic diamonds or other
superhard material embedded in and/or beneath the surface of the
bit body 10 in place of the cutters 18, 20.
[0026] The bit body 10 is of the matrix type and is manufactured by
placing particles 30 of tungsten carbide and optionally other
materials such as tungsten powder, diamond or other superhard
particles, and a suitable infiltrant, within a mold, and heating
the mold and its contents to cause the infiltrant to infiltrate the
matrix material and to cause the particles of tungsten carbide and
other powders to bond together to form a solid body matrix. The
details of matrix bit molding and manufacture are well known in the
industry, and are described in U.S. Pat. No. 6,116,360 herein
incorporated by reference for all it discloses.
[0027] FIG. 2 is a photomicrograph of the matrix of the bit body
10. As shown in FIG. 2, the matrix contains particles 30 of
tungsten carbide bound together by a suitable binder material 36.
The particles 30 are of generally spherical form and are
manufactured by a process whereby small droplets of molten tungsten
carbide are cooled very rapidly. The rapid cooling results in the
particles 30 being of an unusual form, the particles 30 each
including a relatively hard central core 32 surrounded by an outer
skin 34 which is less hard and more ductile than the central core
32.
[0028] The particles 30 have a relatively large surface area and
are rough, thus metallurgical bonding and mechanical gripping
between the particles and the binder material 36 are good. The
rough outer surface 40 of the particles 30 provides a much greater
surface area, and therefore greater bond strength than the
relatively smooth surfaces of crushed or macrocrystalline tungsten
carbide.
[0029] The central core 32 is typically of hardness approximately
2100HV100 giving rise to good erosion or abrasion resistance. The
outer skin 34 contains a relatively large proportion of a high
temperature phase of tungsten carbide which is relatively ductile
and also has a crystallographic structure which is amenable to
wetting by the infiltrant material, thus assisting in the formation
of good bonds between the particles 30 and the binder material 36.
The outer skin 34 is typically of hardness approximately
1500HV100.
[0030] The tungsten carbide material used results in the bit body
having an erosion resistance approximately ten times that of a body
formed using the macrocrystalline material, and a fatigue strength
of approximately twice that of such a body.
[0031] In addition to the advantages associated with the
crystallographic structure of the particles 30, the spherical shape
of the particles 30 results in an increase in the density with
which the particles 30 can be packed into the mold during
manufacture. Further, in use, the spherical shape tends to deflect
abrasive materials away from the particles. The particles 30 are
also of good thermal stability and maintain their hardness to very
high temperatures.
[0032] It will be appreciated that, although described with
reference to a particular type of drill bit body, the invention is
also applicable to drill bit bodies of a range of other
designs.
[0033] Whereas the present invention has been described in
particular relation to the drawings attached hereto, it should be
understood that other and further modifications apart from those
shown or suggested herein, may be made within the scope and spirit
of the present invention.
* * * * *