U.S. patent application number 09/966181 was filed with the patent office on 2002-02-07 for cutting element with improved polycrystalline material toughness and method for making same.
Invention is credited to Eyre, Ronald K..
Application Number | 20020014355 09/966181 |
Document ID | / |
Family ID | 21889384 |
Filed Date | 2002-02-07 |
United States Patent
Application |
20020014355 |
Kind Code |
A1 |
Eyre, Ronald K. |
February 7, 2002 |
Cutting element with improved polycrystalline material toughness
and method for making same
Abstract
A cutting element having a cutting table made from sheet
segments of commingled ultra hard material and binder. Each segment
may be made from a finer or a coarser grade of ultra hard material
or from different types of ultra hard material. The segments are
aligned side by side over a cutting face of the cutting element to
form the cutting table. The material grade and/or the material type
of each segment may alternate across the cutting face.
Inventors: |
Eyre, Ronald K.; (Orem,
UT) |
Correspondence
Address: |
CHRISTIE, PARKER & HALE, LLP
P.O. BOX 7068
PASADENA
CA
91109-7068
US
|
Family ID: |
21889384 |
Appl. No.: |
09/966181 |
Filed: |
September 28, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09966181 |
Sep 28, 2001 |
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09573142 |
May 17, 2000 |
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09573142 |
May 17, 2000 |
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09036577 |
Mar 6, 1998 |
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Current U.S.
Class: |
175/425 ;
175/434 |
Current CPC
Class: |
E21B 10/5676
20130101 |
Class at
Publication: |
175/425 ;
175/434 |
International
Class: |
E21B 010/36 |
Claims
1. A cutting element comprising: a body having a cutting face; and
a plurality of abutting side by side sheet segments of ultra hard
material on the cutting face forming a cutting layer.
2. A cutting element as recited in claim 1 wherein the material
grade of a first segment is different than the grade of a second
segment.
3. A cutting element as recited in claim 1 wherein the segments
alternate in a radial direction from the center of the cutting face
between a finer and coarser material grade.
4. A cutting element as recited in claim 1 wherein a first segment
comprises a first type of ultra hard material and a second segment
comprises a second type of ultra hard material that is different
than the first type.
5. A cutting element as recited in claim 1 wherein the segments
alternate in a radial direction from the center of the cutting face
between a first and a second type of ultra hard material.
6. A cutting element as recited in claim 1 wherein the segments are
cut from a high shear compaction sheet of commingled ultra hard
material and binder.
7. A cutting element as recited in claim 1 wherein the segments are
concentric ring shaped strips.
8. A cutting element as recited in claim 7 wherein the ultra hard
material forming each strip increases in coarseness for each
radially inward strip.
9. A cutting element as recited in claim 7 wherein each strip
causes compressive hoop stresses to be formed on a subsequent strip
inward when the cutting layer is formed.
10. A cutting element as recited in claim 1 wherein the segments
are linear chordwise strips.
11. A cutting element as recited in claim 1 wherein the segments
are divided in two sets, a first set comprising parallel segments
and a second set comprising parallel segments wherein the two sets
are at an angle to each other.
12. A cutting element comprising: a body having a cutting face; a
first set of sheet segments of ultra hard material formed on the
cutting face; and a second set of sheet segments of ultra hard
material formed on the cutting face wherein the segments alternate
along a radial direction from the center of the cutting face
between the first and second sets.
13. A cutting element as recited in claim 12 wherein each segment
of the first set comprises an upper surface and a lower surface
wherein the upper surface is narrower than the lower surface.
14. A cutting element as recited in claim 12 wherein each segment
of the second set comprises an upper surface and a lower surface
wherein the upper surface is wider than the lower surface.
15. A cutting element as recite in claim 14 wherein the segments of
the first set are complementary to the segments of the second
set.
16. A cutting element as recited in claim 12 wherein the first set
segments are made from an ultra hard material grade that is
different from the grade of ultra hard material making up the
second set segments.
17. A cutting element as recited in claim 12 wherein one set of
segments comprises diamond and the other set comprises cubic boron
nitride.
18. A cutting element as recited in claim 12 wherein the segments
for each set are cut from high shear compaction sheets of
commingled ultra hard material and binder.
19. A cutting element comprising: a body having a cutting face; and
a spiraling ultra hard material strip formed on the cutting face
forming a cutting table.
20. A cutting element as recited in claim 19 further comprising a
second spiraling ultra hard material strip formed on the cutting
face and spiraled within the first spiraling ultra hard material
strip.
21. A cutting element as recited in claim 20 wherein the first
ultra hard material strip is made from a grade of ultra hard
material that is different than the grade of the second strip.
22. A cutting element as recited in claim 20 wherein the first
ultra hard material strip comprises a first type of ultra hard
material and the second ultra hard material strip comprises a
second type of ultra hard material different than the first
type.
23. A cutting element as recited in claim 20 wherein each strip is
cut from a high shear compaction sheet of commingled ultra hard
material and binder.
24. A method for forming a cutting element comprising the steps of:
forming a cutting element body having a cutting face; placing a
plurality of side by side sheet segments of commingled ultra hard
material and binder on the cutting face; and processing the body
and segments at a temperature and pressure for forming a
polycrystalline ultra hard material layer from the segments.
25. A method as recited in claim 24 further comprising the steps
of: determining a desired residual stress distribution on the ultra
hard material layer; and placing segments having different material
properties on the cutting face in a pattern for forming a
polycrystalline ultra hard material layer having the desired
residual stress distribution.
26. A method as recited in claim 24 further comprising the step of
placing segments from different sheets of commingled ultra hard
material and binder across the cutting face, wherein a segment from
a first sheet is adjacent to a segment from a second sheet.
27. A method as recited in claim 24 wherein the step of placing
further comprises the steps of: slitting a sheet of commingled
ultra hard material and binder into strip segments; and positioning
the strip segments in parallel on the cutting face.
28. A method as recited in claim 24 wherein the step of placing
further comprises the steps of: slitting a sheet of commingled
ultra hard material and binder in strip segments; and positioning
at least some of the strip segments at an angle to each other on
the cutting face.
29. A method as recited in claim 24 wherein the step of placing
further comprises the steps of: cutting concentric ring shaped
strip segments from a sheet of commingled ultra hard material and
binders; and positioning the strip segments over the cutting
face.
30. A method for forming a cutting element comprising the steps of:
forming a cutting element body having a cutting face; forming a
spiral strip from a sheet of commingled ultra hard material and
binder; placing the strip on the cutting face; and processing the
body and strip at sufficient pressure and temperature for forming a
polycrystalline ultra hard material layer from the strip on the
body.
31. A method as recited in claim 30 wherein the forming step
further comprises the steps of: rolling a sheet of commingled ultra
hard material and binder into a roll; and cutting a slice from the
roll whereby the slice is in the form of a spiral strip.
32. A method as recited in claim 30 further comprising the steps
of: forming a second spiral strip from a sheet of commingled ultra
hard material and binder; and bonding the second spiral strip on
the cutting face within the first spiral strip.
33. A method as recited in claim 32 wherein the first spiral strip
is formed from a sheet comprising a grade of ultra hard material
that is different than the grade of the ultra hard material forming
the second spiral strip.
34. A method as recited in claim 32 wherein the first spiral strip
comprises a first type of ultra hard material and the second spiral
strip comprises a second type of ultra hard material, wherein the
first type of ultra hard material is different than the second type
of ultra hard material.
35. A method for forming a cutting element comprising the steps:
forming a cutting element body having a cutting face; placing a
first sheet of commingled ultra hard material and binder over a
second sheet of commingled ultra hard material and binder; rolling
the two sheets into a roll; cutting a slice from the roll; placing
the slice to the cutting face; and processing the body and slice at
a sufficient temperature and pressure for forming a polycrystalline
ultra hard material layer from the slice on the body.
36. A method as recited in claim 35 wherein each sheet comprises a
different grade of ultra hard material.
37. A method as recited in claim 35 wherein each sheet comprises a
different type of ultra hard material.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to cutting elements for use in a rock
bit and more specifically to cutting elements which have a cutting
table made up of segments of an ultra hard material.
[0002] A cutting element, such as a shear cutter shown in FIG. 1,
typically has a cylindrical tungsten carbide substrate body 10
which has a cutting face 12. An ultra hard material cutting table
14 (i.e., layer) is bonded onto the substrate by a sintering
process. The ultra hard material layer is typically a
polycrystalline diamond or polycrystalline cubic boron nitride
layer. During drilling, cracks form on the polycrystalline ultra
hard material layer. These cracks are typically perpendicular to
the earth formation being drilled. These cracks grow across the
entire ultra hard material layer causing the failure of the layer
and thus of the cutter. Growth of these cracks result in chipping,
laminar type spalling and exfoliation. As such, there is a need for
a cutting element having a cutting table that is capable of
resisting crack growth.
SUMMARY OF THE INVENTION
[0003] The present invention is directed to a cutting element
having a cutting table which is formed from segments of an ultra
hard material. Preferably, some of the segments are made from finer
grade of ultra hard material while the remaining segments are made
from a coarser grade of ultra hard material. The segments alternate
from a finer grade to a coarser grade across the cutting face of
the cutting element. It is preferred that the finer grade material
makes contact with the earth formation. As such, preferably, a
finer grade segment makes up the edge of the cutting table making
contact with the earth formation.
[0004] In an alternate embodiment, some of the segments are made
from a first type of ultra hard material such a diamond, while the
remainder of the segments are made from a second type of ultra hard
material such as cubic boron nitride. With this embodiment, the
segments form the cutting table and alternate from the first type
of ultra hard material to the second type across the cutting
table.
[0005] It is preferred that the segments are high shear compaction
sheet segments which are formed by slitting a high shear compaction
sheet. The segments forming the cutting table can be linear and
parallel to each other, they may be concentric ring-shaped strips
or spiraling strips. Moreover, two sets of strips may be employed
to form the cutting table wherein the strips within each set are
parallel to each other and wherein the first set is angled relative
to the second set of strips.
DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a perspective view of a typical shear cutter.
[0007] FIG. 2 is a top view of a cutting element prior to sintering
having a cutting table made of concentric ring-shaped ultra hard
material strips.
[0008] FIG. 3 is a top view of a cutting element prior to sintering
having a cutting table made from linear parallel chordwise ultra
hard material strips.
[0009] FIG. 4 is a top view of a cutting element prior to sintering
having a cutting table made of two sets of parallel ultra hard
material strips, wherein the first set is angled relative to the
second set.
[0010] FIG. 5 is cross-sectional view of a cutting element prior to
sintering having a cutting table made of two sets of mated strips
wherein the strips are tapered in cross-section such that the
strips of the first set are wider at the bottom and narrower at the
top and the strips of the mated second set are wider at the top and
narrower at the bottom.
[0011] FIG. 6 is a top view of a cutting element prior to sintering
having a cutting table formed from a spiraling ultra hard material
strip.
[0012] FIG. 7 is a top view of a cutting element prior to sintering
having a cutting table formed from two spiraling strips of ultra
hard material.
DETAILED DESCRIPTION OF THE INVENTION
[0013] This invention relates to cutting elements having cutting
tables with enhanced toughness and to a method of making such
cutting elements. Cutting elements employed in rock bits that have
a variety of conventional shapes. For descriptive purposes, the
present invention is described in relation to a cylindrical cutting
element. A cylindrical cutting element such as a shear cutter as
shown in FIG. 1 has a cylindrical cemented tungsten carbide body 10
which has a cutting face 12. An ultra hard material layer 14 is
bonded onto the cutting face and forms the cutting table. The ultra
hard material layer is typically either a polycrystalline diamond
(PCD) layer or a polycrystalline cubic boron nitride (PCBN)
layer.
[0014] To enhance the toughness of the cutting table two or more
dissimilar grades of the ultra hard material are alternated along
the cutting face of the cutter. A finer grade ultra hard material
has higher abrasion resistance. A courser grade ultra hard material
is known to be tougher.
[0015] Due to the nature of drilling, cracks form on the
polycrystalline ultra hard material which are typically almost
perpendicular to the earth formation being drilled. These cracks
generally result in chipping, laminar type spalling and
exfoliation. The present invention provides a way of arresting
crack growth before it propagates across the entire cutting table
thereby prolonging the life of the cutting element.
[0016] The polycrystalline ultra hard material cutting table of the
present invention is formed on the cutting face of the cutting
element such that grade alternates from a finer grade to a coarser
grade in a direction perpendicular to the formation. Preferably a
finer grade would be used to do the cutting (i.e.. will be in
contact with the earth formation) while the coarser grade would be
used to arrest any crack grown. As such, a finer grade would
preferably be located at the edge of the cutting table which would
contact the earth formation. Typically, what would happen is that a
crack will form proximate the edge and would start traveling
perpendicular to the formation. Once the crack reaches the coarser
material, crack growth would be arrested. As a result, the
toughness of the polycrystalline cutting table is increased.
[0017] In a first embodiment shown in FIG. 2, the ultra hard
material cutting table 14 is formed by placing ring-shaped
concentric spaced apart segments 16 of a single ultra hard material
grade over the cutting face of a presintered tungsten carbide
substrate body. The spaces between the concentric rings are then
fitted with a second set of concentric ring-shaped segments 18 made
from a different grade of material. Once the segments are sintered,
they from a polycrystalline ultra hard material table which
alternates in grade cross the cutting face. Preferably, the set of
concentric segments which include the concentric segment forming
the edge of the cutting table 14 are the finer grade segments. As
it would become apparent to one skilled in the art, the centermost
segment 20 will be circular and not ring-shaped.
[0018] In a further embodiment as shown in FIG. 3, chordwise
segments (i.e., strips) 22 of the ultra hard material are placed on
top of the substrate cutting face and form the cutting element
cutting table. These strips may be of a single grade or may be of
multiple grades of ultra hard material. Preferably, two sets of
strips are employed. The first set 24 is made from a finer grade of
ultra hard material, while the second set 26 is made from a coarser
grade of ultra hard material. Strips from the first set are
alternated in parallel with strips from the second set along the
cutting element body cutting face. Strips from the first set,
preferably make up the edges of the cutting table that will contact
the earth formation: As it would become apparent to one skilled in
the art, one side of each of the edge strips 25 is curved so as to
be aligned with the cutting element body.
[0019] In yet a further embodiment shown in FIG. 4, two sets of
strips 28, 30 are used. The strips of the first set are positioned
on the cutting element cutting face at an angle to the strips of
the second set. The strips may be of a single grade or multiple
grades of ultra hard material. Preferably, two grades 32, 34 are
used wherein strips within each set alternate from strip of a finer
grade to a strip of a coarser grade of ultra hard material.
[0020] To maximize the life of the cutting elements of the
embodiments which have a cutting table formed from chordwise strip
segments of ultra hard material, it is preferred that such cutting
elements are mounted on the rock bit bodies so as to contact the
earth formations at an angle perpendicular to the ultra hard
material strips.
[0021] With any of the above embodiments, the segments may have
cross-sections as shown in FIG. 5. For example, a set of
spaced-apart segments may have a wider bottom 36 and a narrower top
38 in cross-section, while a second set of spaced-apart segments
which is inter-fitted with the first set may have a wider top 40
and a narrower bottom 42 such that the second set is complementary
to the first set as shown in FIG. 5.
[0022] With any of the above described embodiments, more than two
different grade ultra hard material segments may be used. In such
cases, it is preferred that the segments alternate from a first, to
a second, to a third grade and so forth across the cutting table.
In yet further embodiments, all of the ultra hard material segments
employed in any of the above described embodiments may be formed
from a single grade of ultra hard material. With these embodiments,
the bond line between the successive segments would serve to divert
and arrest crack growth. In yet further embodiments, instead of
alternating segments of different grades or ultra hard material
across the table, segments of different types of ultra hard
materials are alternated across the cutting table. For example,
diamond segments may be alternated with cubic boron nitride
segments. These segments may contain ultra hard material of the
same or different grades.
[0023] By being able to vary the material characteristics of the
cutting layer across its face, the compressive residual stresses
formed across the ultra hard material layer can be controlled or
tailored for the task at hand. In other words, the residual
compressive stress distribution on the ultra hard material layer
can be engineered. For example, in the embodiment shown in FIG. 2,
each ultra hard material ring-shaped segment may be made from a
coarser material than the segment immediately radially outward from
it. Since a coarser grade material shrinks less than a finer grade
material during sintering, each segment will impose a compressive
hoop stress on its immediately inward segment. As a result, a
cutting layer will be formed having compressive hoop stresses.
[0024] With all of the aforementioned embodiments, it is preferred
that the segments are cut from an ultra hard material tape, i.e.,
they are segments of the ultra hard material tape. Preferably, they
are cut from a high shear compaction sheet of commingled ultra hard
material and binder. Typically, such a high shear compaction sheet
is composed of particles of ultra hard materials such as diamond or
cubic boron nitride, and organic binders such a polypropylene
carbonate and possibly residual solvent such as methyl ethyl ketone
(MEK). The sheet of high shear compaction material is prepared in a
multiple roller process. For example, a first rolling in a multiple
roller high shear compaction process produces a sheet approximately
0.25 mm thick. This sheet is then lapped over itself and rolled for
a second time, producing a sheet of about 0.45 mm in thickness. The
sheet may be either folded or cut and stacked in multiple layer
thickness.
[0025] This compaction process produces a high shear in the tape
and results in extensive mastication of ultra hard particles,
breaking off comers and edges but not cleaving them and creating a
volume of relatively smaller particles in situ. This process also
results in thorough mixing of the particles, which produces a
uniform distribution of the larger and smaller particles throughout
the high shear compaction material. The breakage rounds the
particles without cleaving substantial numbers of the
particles.
[0026] Also, high shear during the rolling process produces a sheet
of high density, i.e., about 2.5 to 2.7 g/cm.sup.3, and preferably
about 2.6.+-.0.05 g/cm.sup.3. This density is characteristic of a
sheet having about 80 percent by weight diamond crystals (or cubic
boron nitride crystals), and 20 percent organic binder. At times,
it is desirable to include tungsten carbide particles and/or cobalt
in the sheet. There may also be times when a higher proportion of
binder and lower proportion of diamond or cubic boron nitride
particles may be present in the sheet for enhanced "drapability."
The desired density of the sheet can be adjusted proportionately
and an equivalent sheet produced.
[0027] The sheet of high shear compaction material is characterized
by a high green density, resulting in low shrinkage during firing.
For example, sheets used on substrates with planar surfaces have
densities of about 70 percent of theoretical density. The high
density of the sheet and the uniform distribution of particles
produced by the rolling process tend to result in less shrinkage
during the presinter heating step and presintered ultra hard layers
with very uniform particle distribution, which improves the results
obtained from the high pressure, high temperature process.
[0028] In yet a further alternate embodiment shown in FIG. 6, a
spiraling strip 44 forms the cutting table 14. To form the
spiraling strip, preferably an ultra hard material high shear
compaction sheet is rolled into a roll. A slice is cut off the end
of the roll. The slice which is in the form of a spiraling strip is
then bonded to the cutting element body cutting face forming the
cutting table.
[0029] In another embodiment shown in FIG. 7, the cutting table 14
is formed from two spiraling strips 46, 48 of an ultra hard
material. It is preferred that each of the strips is made from a
different grade of the ultra hard material. Alternatively, each
strip may be made from a different type of ultra hard such as
diamond and cubic boron nitride To form the cutting table,
preferably a first ultra hard material high shear compaction sheet
48 is placed over a second ultra hard material high shear
compaction sheet 46. The two sheets are rolled forming a roll. An
end of the roll is sliced off. The sliced portion which is made up
of two spiraling strips is bonded to the cutting face of the
cutting element body to form the cutting table.
* * * * *