Note: Descriptions are shown in the official language in which they were submitted.
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HARDFACING MATERIALS WITH HIGHLY CONFORMING PROPERTIES
BACKGROUND OF THE INVENTION
Related Application: This nonprovisional patent application claims the benefit
of co-pending, provisional patent application United States Serial No.
60/737,003, filed
on November 15, 2005, which is hereby incorporated by reference in its
entirety.
TECHNICAL FIELD
Field of the Invention: This invention relates in general to drill bits for
well
drilling, and in particular to a metallic hardfacing matrix and. method of
applying the
metallic hardfacing matrix to drill bits.
State of the Art: Rotary well drilling for oil and gas is primarily
accomplished
through one of two types of bits. In a rotary cutter bit, the bit body has
typically three
rotatable cones or cutters. The cones rotate on bearing pins and have teeth or
tungsten
carbide inserts for disintegrating the earth formation. In the fixed cutter or
drag bit
type, the bit body has a face which contains cutting elements mounted on fixed
blades.
The cutting elements are typically polycrystalline diamond. The bit body has
drilling
fluid passages with nozzles for discharging drilling fluid through junk slots
that are
located between the blades.
Drag bits are extensively used in directionally drilling, particularly in the
technique referred to as steerable drilling. In this method, the drill bit is
steered in
desired directions for cutting borehole segments as it progresses. A mud motor
or
turbine is employed with the bit assembly for rotating the drag bit while the
drill string
remains stationary.
Hardfacing or wear-resistant materials are typically connected to the outer
surfaces of drill bits to help reduce wear and maintain the efficiency of the
drill bit.
Commonly used hardfacing includes tungsten carbide particles that are welded
in place
on the outer surface of the drill bit. U.S. Reissue Patent Number RE 37,127
provides
an in depth discussion of hardfacings, and is incorporated herein by reference
in its
entirety. Even witli skilled welders, imperfections can be present due to
varying
thicknesses of the weld, shape of the drill bit the hardfacing is being welded
upon, and
the beads associated with welding processes. Machining can be time-consuming
and
expensive. Moreover, hardfacing was not welded to inner parts due to narrow
clearances and expense.
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DISCLOSURE OF THE INVENTION
A method of increasing the durability of a drill bit, which includes the step
providing a pliable sheet of a hardfacing matrix material. The pliable sheet
of
hardfacing material has a nickel and chromium matrix combined with a first
element.
The first element is selected from a group consisting of spherical sintered
tungsten
carbide, spherical cast tungsten carbide, and metallic glass. The hardfacing
matrix
material sheet is placed on a preselected surface of the drill bit. The
hardfacing matrix
material sheet is then fusion bonded to the drill bit.
The fusion bonding can be performed by heating the drill bit and hardfacing
matrix material sheet in a furnace at about 2100 degrees Fahrenheit. The
fusion
bonding can also be in a furnace at about 2100 degrees Fahrenheit for a
duration of
between about five minutes and about ten minutes.
In step in which the hardfacing matrix material sheet is placed on the
preselected surfaced, an adhesive located on a surface of the hardfacing
matrix material
sheet can secure the hardfacing matrix material sheet in place relative to the
preselected
surface of the drill bit prior to the fusion bonding step. The preselected
surface can
comprise an outer gage surface, and a slot surface between a pair of bit
blades. The
drill bit can be a drag bit or a tri-cone bit.
The hardfacing matrix material can also comprise a second element, which was
not previously selected as the first element. The second element is selected
from a
group consisting of spherical sintered tungsten carbide, spherical cast
tungsten carbide,
metallic glass, microcrystalline tungsten carbide and macrocrystalline
tungsten carbide.
The hardfacing matrix material can further comprise a third element, which was
not
previously selected as either the first or second elements. The third element
is selected
from a group consisting of spherical sintered tungsten carbide, spherical cast
tungsten
carbide, metallic glass, microcrystalline tungsten carbide and
macrocrystalline tungsten
carbide.
A method of increasing the durability of a drag bit type of drill bit, when
the
drag bit has a plurality of blades and a slot formed between each pair of
adjacent
blades. Each of the blades has a cutting region with cutting elements and a
gage
surface free of cutting elements. The method includes the step of providing a
sheet of a
hardfacing matrix material comprising a nickel and chromium matrix combined
with a
first element selected from a group consisting of spherical sintered tungsten
carbide,
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spherical cast tungsten carbide, and metallic glass. The sheet of a hardfacing
matrix
material is cut into a pattern corresponding to a preselected surface of the
drag bit. The
pattern is adhered to the preselected surface of the drag bit. The drill bit,
with the
pattern adhered thereto is heated in order to bond the pattern to the drag
bit.
The preselected surface can be the gage surface. The preselected surface can
be
the gage surface and the slot.
The hardfacing matrix material can also include a second element, which was
not previously selected as the first element. The second eleinent is selected
from a
group consisting of spherical sintered tungsten carbide, spherical cast
tungsten carbide,
metallic glass, microcrystalline tungsten carbide and macrocrystalline
tungsten carbide.
The hardfacing matrix material can further include a third element, which was
not
previously selected as either the first or second elements. The third element
is selected
from a group consisting of spherical sintered tungsten carbide, spherical cast
tungsten
carbide, metallic glass, microcrystalline tungsten carbide and
macrocrystalline tungsten
carbide.
An earth-boring bit includes a bit body with a bit face at its lower end and a
nozzle opening to the bit face for discharging drilling fluid from an interior
of the bit
body. A plurality of blades are formed on and protrude from the bit face. The
plurality
of blades extend radially outward from a central portion of the bit face to a
gage area at
the periphery of the bit body. Each blade carries a plurality of cutters
thereon. Each
pair of blades define a slot extending therebetween for the passage of
drilling fluid and
cuttings. A layer of hardfacing material is bonded to a surface of the bit
body. The
hardfacing material is substantially uniform in thickness and free of
weldbeads. The
hardfacing material includes a nickel and chromium matrix combined with a
first
element selected from a group consisting of spherical sintered tungsten
carbide,
spherical cast tungsten carbide, and metallic glass. A bond region is located
between
the layer of hardfacing material and the surface of the bit body to which the
layer of
hardfacing material is bonded.
The bond region can include nickel and chromium from the layer of hardfacing
and iron from the bit body, and the bond region can be formed when the layer
of
hardfacing is bonded to the surface of the bit body with heat. The surface of
the bit
body to which the layer of hardfacing is bonded can be the gage surface. The
surface
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of the bit body to which the layer of hardfacing is bonded can be the slot.
The surface
of the bit body to which the layer of hardfacing can be within the nozzle.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view showing a drag bit asseinbly without
hardfacing.
Figure 2 is a vertical sectional view of the drag bit assembly of Figure 1.
Figure 3 is perspective view of a hardfacing material matrix sheet constructed
in
accordance with this invention.
Figure 4 is top plan view of the hardfacing material matrix sheet of Figure 3,
showing a pattern to be cut therefrom.
Figure 5 is a perspective view showing the drag bit assembly of Figure 1, with
cutouts from the hardfacing material matrix sheet of Figure 3 being attached
thereto.
Figure 6 is an enlarged sectional view of the interface between the outer
surface
of the drag bit assembly of Figure 1 and the hardfacing material matrix sheet
of Figure
3 after fusion bonding.
Figure 7 are schematic perspective views of various forms of spherical cast
tungsten carbide in accordance with this invention.
BEST MODE(S) FOR CARRYING OUT THE INVENTION
Referring to Figure 1, bit assembly 11 has a body 13 on a lower end. Body 13
has a face 15 on its lower end. A plurality of blades 17 are fomled on and
protrude
from face 15, with six blades 17 being shown in the drawings. Blades 17 lead
outward
from a central portion of face 15 to a gage area at the periphery of body 13.
Blades 17
are separated from each other, defining junk slots 19 between them for the
passage of
drilling fluid and cuttings. Each blade 17 contains a row of conventional
cutters
typically polycrystalline diamond (PCD). Nozzles 23 discharge drilling fluid,
which
flows through junk slots 19 and back up the borehole along with the cuttings.
While bit
assembly 11 is illustrated as a "drag bit" or steel-bodied bit, it should be
readily
apparent to those skilled in the art that the teachings herein are also
applicable to tri-
cone bits, or cast bits, such as those illustrated in Figure 1 of U.S. Reissue
Patent
Number RE 37,127.
A set of primary gage pads 25 is integrally formed on the sides of bit body
13.
Each primary gage pad 25 is contiguous with and, in the embodiment shown,
extends
longitudinally from one of the blades 17. Alternately, primary gage pads 25
could be
inclined relative to the axis or curved in a spiral. Each primary gage pad 25
protrudes
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from body 13, extending the junk slots 19. Primary gage pads 25 are
dimensioned to
have-an outer surface 26 at the gage or diaineter of the borehole being cut.
Outer
surface 26 contains wear resistant surfaces, but is smooth and free of any
cutting
structure. Bit body 13, along with blades 17 and gage pads 25, may be formed
of a
metal matrix composite or steel using a casting or machining process.
Referring to Figure 2, a steel threaded coupling or blank 27 is joined to an
upper
end of body 13. Blank 27 is bonded to body 13 during the casting process.
Blank 27
protrudes from the upper end of body 13 and has threads 29 on its exterior. An
axial
passage 31 extends through blank 27 and joins nozzles 23 for delivering
drilling fluid.
A shank 33 is secured to blank 27. Shank 33 is also formed of steel, rather
than
of a carbide matrix. Shank 33 is a cylindrical member that may have a length
longer
than the axial dimension of body 13. Shank 33 has a threaded receptacle 35
which
engages threads 29 of blank 27. A chamfer or bevel 37 is formed on the lower
end of
shank 33. Similarly, a bevel 39 is formed on the upper end of body 13. The
opposed
bevels 37, 39 create a V-shaped annular cavity. This cavity is filled with a
weld
material 41, the welding permanently joining shank 33 to bit body 13. Shank 33
has an
axial passage 43 which registers with passage 31 for delivering drilling
fluid. Shank 33
has a threaded pin 45 on its upper end. Pin 45 is dimensioned for securing to
a lower
end of a drill string.
Bit assembly 11 operates in a manner that is conventional with other steerable
drag bit assemblies. It is normally secured to a turbine or mud motor which is
at the
lower end of drill string. Drilling fluid pumped down the drill string drives
the mud
motor, which in turn causes rotation of bit 11. The spaced apart gage pads 25
stabilize
bit 11 to condition the borehole wall, preventing ledging and other
irregularities.
The hardfacing on outer surfaces and leading and trailing edges typically
comprises a tungsten carbide material that is welded into place. Depending on
the skill
of the welder, welding such hardfacing can create imperfections and high
stress zones
along the weld bead lines or in the hardfacing deposit that can lead to the
hardfacing
chipping off or disengaging from the surface it is meant to protect with its
wear-
resistant properties. Even for skilled welders, the process of welding
hardfacing can be
time consuming, difficult, and tedious due to the geometry of the surfaces to
which the
hardfacing material is being applied. Some surfaces, like internal surfaces
that engage
each other, are simply not available for welded hardfacing.
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A hardfacing metal matrix has been used on the internal surfaces of bearings.
The hardfacing metal matrix typically comes in the form of a pliable sheet. A
desired
shape of the hardfacing surface is cut out of the pliable sheet and then
fusion bonded
onto the target surface, or the surface to be hardfaced. Previous pliable
hardfacing
sheets comprised a metal inatrix that typically included inostly either
microcrystalline
tungsten carbide or macrocrystalline tungsten carbide with lesser ainounts of
nickel and
chromium.
Referring to Figure 3, a hardfacing matrix sheet 101 is shown in its pliable
state.
Hardfacing matrix sheet 101 comprises a hardfacing material matrix 103 and an
adhesive surface 105 along one surface. Adhesive surface 105 helps to hold
hardfacing
matrix sheet 101 against the target surface prior to fusion bonding.
Hardfacing material matrix 103 preferably comprises spherical sintered
tungsten
carbide, spherical cast tungsten carbide, or a nanosteel composite also known
as
"metallic glass." U.S. Patents 6,689,234 and 6,767,419 provide a discussion of
metallic
glass and disclose various methods of applying metallic glass to a substrate.
U.S.
Patents 6,689,234 and 6,767,419 are incorporated herein by reference in their
entireties.
Matrix 103 can also comprise a combination of at least two of spherical
sintered
tungsten carbide, spherical cast tungsten carbide, and metallic glass.
Microcrystalline
and macrocrystalline tungsten carbide can also be added to matrix 103 having
spherical
sintered tungsten carbide, spherical cast tungsten carbide, or metallic glass,
alone or in
combination. Crushed cast tungsten carbide and crushed sintered tungsten
carbide may
also be added to matrix 103 having spherical sintered tungsten carbide,
spherical cast
tungsten carbide, or metallic glass, alone or in combination.
Referring to Figure 7, spherical cast tungsten carbide 117 can comprise
numerous shapes. Preferably, spherical cast tungsten carbide 117 for use in
matrix 103
will be substantially sliaped like a sphere or spherical-shaped 117a. However,
spherical
cast tungsten carbide 117, but it can also be shaped like a sphere that has
been stretched
from its upper and lower surfaces, or prolate-shaped 117b. Alternatively,
spherical cast
tungsten carbide 117 can be shaped like a sphere that has been compressed from
its
upper and lower surfaces, or oblate-shaped 117c. Spherical-, prolate-, and
oblate-
shaped 117a,117b,117c shapes of spherical cast tungsten carbide 117 are due to
the
manufacturing methods of splierical cast tungsten carbide 117 and are useful
to
illustrate that the name spherical cast tungsten carbide should not limit
matrix 103 to
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only spherical-shaped 117a rather than including prolate- and oblate-shaped
117b,117c
matrixes of cast tungsten carbide.
Referring to Figure 4, hardfacing matrix sheet 101 is cut along pattern 107 to
form a desired shape. As shown in Figure 5, pattern 107 preferably corresponds
to a
surface on bit assembly 11. Pattern 107 shown in Figure 4, corresponds to
outer
surface 57. However, as shown in Figure 5, various patterns 107a, 107b can be
cut
from hardfacing matrix sheet 101 to correspond with desired surfaces on bit
assembly.
For example, pattern 107a corresponds with outer surface 26, and pattern 107b
corresponds with body 13 between blades 17. Moreover, hardfacing matrix sheet
101
can also be cut with patterns to correspond to interior surfaces of bit
assembly 11.
Patterns 107a, 107b are placed on the desired surfaces of bit assembly 11.
Figure 5, illustrates bit assembly 11 with patterns 107a, 107b being placed
onto various
desired surfaces. Adhesive 105 initially secures patterns 107a, 107b to the
desired
surfaces of bit assembly 11. Bit assembly 11 with the secured patterns 107a,
107b
attached thereto is placed into a furnace. In the preferred embodiment, bit
assembly 11
with patterns 107a, 107b is placed in the furnace for about five to ten
minutes at about
2100 degrees Fahrenheit to fusion bond the hardfacing matrix on patterns 107a,
107b
onto the desired outer surfaces of bit assembly 11. As will be readily
appreciated by
those skilled in the art, the exact length of time and exact temperature can
vary
depending upon the composition of hardfacing material matrix 103 in accordance
with
the variations described above herein. After fusion bonding patterns 107a,
107b into
place, hardfacing material matrix 103 can be machined from a rough surface to
a
smoother surface as desired.
Referring to Figure 6, a microscopic representation of the interface between
hardfacing material matrix 103 on patterns 107a, 107b and the desired outer
surfaces bit
assembly 11 following fusion bonding is shown. Cladding region 109 comprises
hardfacing material matrix 103 with the hardfacing material being densely
packed
substantially uniformly throughout. As discussed above herein, the particular
hardfacing material can be in a nickel and chromium matrix including spherical
sintered tungsten carbide, spherical cast tungsten carbide, or metallic glass
individually,
in combination with each other, or in combination with microcrystalline or
macrocrystalline tungsten carbide. Bond region 111 is a true metallurgical
bond region
located between hardfacing material matrix 103 and the desired outer surfaces
of bit
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assembly 11 due to the fusion bonding process. Bond region 111 has high
interparticle
bond strength and helps to reduce chipping, flalcing and cracking. Diffusion
zone region
113 results from the fusion bonding process. Bond region 111 comprises nickel
and
chromium from patterns 107a, 107b and iron from the substrate or bit assembly
11.
Typically, the substrate or bit asseinbly 11 uniformly retains most of its
mechanical
properties. Heat treatable region 115 includes the remainder of the substrate
of bit
assembly 11. Region 115 can be heat treated, if necessary, to restore any
mechanical
properties of bit assembly 11 that may have deteriorated to the fusion bonding
process.
While the invention has been shown in only some of its forins, it should be
apparent to those skilled in the art that it is not so limited, but is
susceptible to various
changes without departing from the scope of the invention. For example, bit
assembly
can also be a tri-cone bit, or cast bit.
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