U.S. patent application number 10/437469 was filed with the patent office on 2003-11-27 for polycrystalline diamond cutters with enhanced impact resistance.
Invention is credited to Raftery, Therese, Snyder, Shelly Rosemarie.
Application Number | 20030217869 10/437469 |
Document ID | / |
Family ID | 29420635 |
Filed Date | 2003-11-27 |
United States Patent
Application |
20030217869 |
Kind Code |
A1 |
Snyder, Shelly Rosemarie ;
et al. |
November 27, 2003 |
Polycrystalline diamond cutters with enhanced impact resistance
Abstract
Disclosed is an abrasive compact layer wherein the compact layer
contains >30% by volume large single crystal diamonds, and
wherein said diamond crystals are characterized as having a well
defined cubo-octahedral diamond shapes (aspect ratios>0.87), and
high toughness index crystals (TI>50).
Inventors: |
Snyder, Shelly Rosemarie;
(Millersport, OH) ; Raftery, Therese; (Columbus,
OH) |
Correspondence
Address: |
Hanh T. Pham
General Electric Company
One Plastics Avenue
Pittsfield
MA
01201
US
|
Family ID: |
29420635 |
Appl. No.: |
10/437469 |
Filed: |
May 14, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60382209 |
May 21, 2002 |
|
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|
Current U.S.
Class: |
175/428 ;
175/434 |
Current CPC
Class: |
C09K 3/1409 20130101;
C04B 2235/5436 20130101; C04B 2235/427 20130101; C04B 2235/5296
20130101; C04B 35/522 20130101; E21B 10/567 20130101 |
Class at
Publication: |
175/428 ;
175/434 |
International
Class: |
E21B 010/46 |
Claims
1. A preform cutting element comprising a body of a superhard
polycrystalline material comprising a plurality of diamond
crystals, wherein said diamond crystals having a particle size
distribution in the range of about 60 to 100 microns; a toughness
index of at least about 50; and an average aspect ratio of 0.80 or
greater.
2. The cutting element of claim 1, wherein said polycrystalline
body comprises a plurality of diamond crystals having a particle
size distribution in the range of about 70 to 90 microns.
3. The cutting element of claim 2, wherein said polycrystalline
body comprises a plurality of diamond crystals having an average
aspect ratio of at least 0.85.
4. The cutting element of claim 2, wherein said polycrystalline
body comprises a plurality of diamond crystals having a toughness
index of at least about 60.
5. A tool comprising the preform cutting element of claim 1.
6. The preform cutting element of claim 1, wherein the cutting
element is mounted upon a cutting face of a drill bit.
7. The preform cutting element of claim 1, further comprising a
cutting surface adapted for use as a cutting insert in a machining
operation.
8. The preform cutting element of claim 1, further comprising an
additive material prior to formation of the cutting element in a
high pressure high temperature operation.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority on U.S. Provisional
Application Serial No. 60/382,209, filed on May 21, 2002.
FIELD OF THE INVENTION
[0002] The present invention relates to superhard cutting elements
as machine-wear resistant materials. Specifically, this invention
relates to polycrystalline diamond and cubic boron nitride cutting
elements useful in rock drilling.
BACKGROUND OF THE INVENTION
[0003] Abrasive compacts are used extensively in cutting milling,
grinding, drilling and other abrasive operations. The abrasive
compacts typically consist of polycrystalline diamond and/or cubic
boron nitride (CBN) particles bonded into a coherent hard
conglomerate. Abrasive compacts are made under high temperature and
pressure conditions at which the abrasive particle, be it diamond
or cubic boron nitride, is crystallographically stable. Composite
compacts have found special utility as cutting elements or cutters
in drill bits.
[0004] Drill bits for use in rock drilling, machining of wear
resistant materials, and other operations which require high
abrasion resistance or wear resistance generally consist of a
plurality of polycrystalline abrasive cutting elements fixed in a
holder. See U.S. Pat. Nos. 4,109,737 and 5,379,854, which describe
drill bits with a tungsten carbide stud (substrate) having a
polycrystalline diamond compact on the outer surface of the cutting
element. A plurality of these cutting elements then are mounted
generally by interference fit into recesses into the crown of a
drill bit, such as a rotary drill bit.
[0005] In the prior art, attempts to improve the impact resistance
of polycrystalline diamond cutters have focused on one of several
methods. European Patent No. EP 0546725 discloses the use of large
diamond crystal in the PCD matrix for PCD cutting tools with high
impact resistance. This method has improved impact resistance but
at the expense of a markedly lower abrasion resistance.
[0006] Another approach has been aimed at minimizing of the
residual stress state between the polycrystalline diamond cutter
and the substrate to which it is bonded, typically tungsten
carbide, by modification of the geometry of the substrate (see, for
example, U.S. Pat. Nos. 5,875,862; 5,351,772; 6,029,760; and
5,829,541).
[0007] In yet another method, the particle size distribution of the
polycrystalline diamond powder is modified prior to sintering to
achieve impact resistance (U.S. Pat. Nos. 5,135,061 and 5,607,024).
This method, however, is at the expense of significantly reducing
the abrasion resistance of the cutting element.
[0008] Applicants have found that the performance of the cutting
element, specifically, the impact resistance, can be improved by
manipulation of the physical properties of the diamond crystals,
specifically the particle size distribution, the aspect ratio, and
the crystal toughness, while still maintaining desirable abrasion
resistance properties.
SUMMARY OF THE INVENTION
[0009] The invention relates to a pre-sintered diamond for use in
cutting elements, having characteristics of a large single crystal
of greater than about 60 micron, an aspect ratios of greater than
about 0.80, and high toughness index crystals of about 50 or
more.
[0010] The invention also relates to a method to improve the impact
resistance of cutting elements by the use of diamond crystals
having a particle size distribution of greater than about 60
micron, an aspect ratio of greater than about 0.80, and high
toughness index crystals of about 50 or more.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a SEM micrograph showing one embodiment of the
invention, with diamond crystals having a largely well defined
cubo-octahedral shape.
[0012] FIG. 2A is a SEM micrograph showing the highly dense matrix
of one embodiment of the invention, employing the diamond
crystals.
[0013] FIG. 2B is a SEM micrograph showing the matrix of the
traditional sintered diamond crystals of the prior art.
[0014] FIG. 3A shows the cutting element of the prior art after an
impact resistance test at 10.times..
[0015] FIG. 3B shows onembodiment of the cutting element of the
invention, after an impact resistance test, at 10.times..
DETAILED DESCRIPTION OF THE INVENTION
[0016] The invention relates to cutting elements for machine wear
materials, including rotary drill bits for use in drilling or
coring holes in subsurface formations. The invention may be applied
to a number of different kinds of rotary drill bits, including drag
bits, roller cone bits and percussion bits.
[0017] By way of example, the invention will be primarily described
in relation to a cutting element which comprises a preform element,
often in the form of a circular tablet, including a cutting table
of superhard material having a front cutting face, a peripheral
surface, and a rear face, the rear face of the cutting table being
bonded to a substrate of material which is less hard than the
superhard material.
[0018] The cutting table usually comprises diamond crystals,
although other superhard materials are available and may be used,
such as cubic boron nitride. The substrate of less hard material is
often formed from cemented tungsten carbide, and the cutting table
and substrate are bonded together during formation of the cutting
element in a high pressure, high temperature forming press. This
forming process is well known and will not be described here. The
preform cutting element may be directly mounted on the bit body or
may be bonded to a carrier disc, for example also of cemented
tungsten carbide, the carrier being in turn received in a socket in
the bit body. The bit body may be machined from metal, usually
steel, or may be formed from an infiltrated tungsten carbide matrix
by a powder metallurgy process.
[0019] In one embodiment, the substrate may be formed by joining
together two or more disparate carbide discs in the HTHP sintering
process to form the PDC cutter. The carbide discs may vary from
each other in binder content, carbide grain size, or carbide alloy
content. In another embodiment, the carbide discs may be selected
and arranged, therefore, to produce a gradient of materials content
in the substrate which modifies and provides the properties for the
cutting table.
[0020] The diamond clusters forming the cutting table are produced
by a method which provides a source of carbon and a plurality of
growth center particles, each growth center particle comprising a
bonded mass of constituent particles, producing a reaction mass by
bringing the carbon source and the growth center particles into
contact with a solvent/catalyst, subjecting the reaction mass to
conditions of elevated temperature and pressure suitable for
crystal growth and recovering a plurality of the diamond clusters,
as discrete entities, from the reaction mass. The carbon source may
be graphite, HPHT (high pressure high temperature) synthetic
diamond, chemical vapor deposited (CVD) diamond or natural diamond,
or a combination of two or more thereof or other carbon sources
known in the art.
[0021] Diamond crystals are commercially available from a number of
suppliers including, for example, General Electric Company, DeBeers
Industrial Diamond Division, or Dennis Tool Company. Typical
diamond used in PCD synthesis has a TI of <45, aspect ratios of
.about.0.7 and a broad PSD centered around 30 microns.
[0022] Applicants have found that during the HPHT process,
selection of the diamond crystal's physical properties allows
targeting of the dimensional, mechanical, and thermal properties of
the HPHT compact. Specifically, Applicants have found a method to
improve the impact resistance of a cutting tool by manipulation of
the physical properties of the diamond, e.g., the diamond particle
size distribution (PSD), aspect ratio, and crystal toughness, to
optimize the packing density and sinterability of the diamond after
high temperature and pressure sintering.
[0023] In one embodiment of the invention, the post sintered PCD of
this invention contains whole crystals bonded together in a highly
dense matrix as shown in the FIG. 2A, unlike the traditional
sintered PCD, as shown in FIG. 2B, which is amorphous in
structure.
[0024] Particle Size Distribution ("PSD"). The fabrication of the
diamond compact can be influenced by the porosity of the compact,
which can be controlled in a number of ways. For example, the
particle size distribution (PSD) of the precursor particulate
diamond can be varied to adjust the porosity of the compact formed
during the HPHT process. As a general rule, a very narrow PSD will
give a much more porous structure than a wide PSD which has been
optimized for maximum packing (e.g., particles having diameters
ranging from tens of microns to submicron sizes).
[0025] In one embodiment of the present invention, PCD toughness is
imparted through the use of single crystal diamond with a PSD of
>50 microns. In a second embodiment, the diamond crystals have a
PSD of about 60-100 microns. In a third embodiment, the diamond
crystals have a PSD in the range of about 70 to 90. In yet a fourth
embodiment, the PSD is >=75. In a fifth embodiment, the PSD is
<=95.
[0026] Aspect Ratio. The diamond crystals in the present invention
have relatively large aspect ratios. In one embodiment of the
invention, the diamond crystals have an average aspect ratio
>=0.80. In a second embodiment, the aspect ratio is >=0.85.
In a third embodiment, the average aspect ration is >=0.87.
[0027] In one embodiment of the invention, the diamond crystals
have largely well defined cubo-octahedral shapes as shown in FIG.
1. In a second embodiment, the crystals may have a large aspect
ratio in various shapes, including ellipsoids. In a third
embodiment, the crystals are essentially two dimensional such as
laminas and/or flakes. In yet another embodiment, the crystals are
essentially one dimensional, e.g. rods, fibers and/or needles.
[0028] Crystal Toughness. Diamond crystal toughness is indicated by
the toughness index "TI." TI is measured by placing 2 carats of
material in a capsule with a steel ball, agitating it vigorously
for a fixed amount of time, and measuring the weight of fragments
produced of a certain size with respect to a certain starting
weight of a certain size. The size of the steel ball employed and
the agitating time vary with the size of the diamond abrasive
grains. In one example, a certain amount of material which has
passed a 139 .mu.m-mesh screen and was retained on a 107 .mu.m-mesh
screen, corresponding the size 120/140, is put together with a
steel ball of 7.94 mm in diameter in a 2 ml-capsule, set on a
vibration tester, and subjected to milling for a certain time
period (30.0.+-.0.3 seconds), followed by screening with a 90
.mu.m-mesh screen. The amount of the crystals remained on the 90
.mu.m-mesh screen is expressed as a weight percent based on the
starting crystals.
[0029] In one embodiment of the present invention, improved impact
resistance is imparted through the use of diamond crystals with a
high toughness index with TI values of greater or equal to about
50. In a second embodiment, the diamond crystals are characterized
as having a TI of greater than or equal to about 55. In a third
embodiment, the diamond crystals are characterized as having a TI
or greater than or about 60.
[0030] Other parameters. In one embodiment of the invention, the
impact resistance and abrasion resistance may also be additionally
adjusted means known in the art, for example by adding cobalt to
the polycrystalline diamond particles has the effect of increasing
the impact resistance of the composition.
[0031] In one embodiment of the invention, the diamond body
constitutes >30 volume % and the binder-catalyzing material
constitutes <70 volume % of the cutting element. In another
embodiment of the invention, the cutting element comprises >50%
by volume large single crystal diamonds of >30 microns. In yet
another embodiment, the volume density of the diamond in the cutter
body is greater than about 70 volume %. In yet another embodiment
of the invention, experimental data show the new high performance
cutter has 50% improvement in impact resistance over a cutter in
the prior art.
[0032] The PCD cutting element of the invention can be used on a
drill bit for use in drilling or coring holes in rock surfaces. In
yet another embodiment, it can be in the form of a triangular,
rectangular, or other shaped material for use as a cutting insert
in machining operations. In yet a third embodiment, it can be used
for other applications such as hollow dies, friction bearings,
indentors for surface roughening, and the like. It should be
understood that applications for polycrystalline diamond requiring
high impact resistance in combination with excellent abrasion
resistance would benefit from a cutting element employing the
diamond crystals of the present invention.
[0033] EXAMPLE. The examples below are merely representative of the
work that contributes to the teaching of the present invention, and
the present invention is not to be restricted by the examples that
follow.
[0034] High grade MBG crystals available from General Electric
Company of Worthington, Ohio, having a TI value of 67 and
cubo-octahedral shaped diamonds having aspect ratio .about.0.97,
and with a PSD centered on 80 micron diameter are used. The diamond
crystals are used to synthesize PCD cutters on 14% cobalt
containing tungsten carbide substrate into various cylinders with
sizes ranging from 9-22 mm diameter and 3-25 mm height. The
cubo-octahedral shaped diamonds occupy .about.10% less volume than
diamond particles of a lower aspect ratio. Upon compaction, the
diamond shifts to a tri-modal PSD with peaks at 60, 20, and 1
micron.
[0035] For comparative tests, standard cutters of the same sizes as
available from General Electric Company of Worthington, Ohio, under
the trade name TITAN are used.
[0036] Abrasion, impact, and Parkson Mill data are measured on the
sintered cutter of the invention and the standard cutters of the
prior art, and are presented below.
[0037] Impact data: The impact drop test is to measure the
toughness of the cutter with respect to the thickness feed type and
interface/tungsten carbide features/composition. All parts tested
have a carbide chamfer of greater than about 0.2 mm, less than 1.0
mm radial or 45.degree. on the locating base. In the test, the
cutter (sharp edge) is mounted securely in a steel holder at an
angle of 20 deg. The diamond table is clear of the holder (clamping
forces). A steel striker plate is rested on the diamond table (one
point of contact on the diamond with the plate being supported by
sponge). A 35 lb weight with a contact area of 1 square inch is
dropped freely onto the plate transferring the impact energy
through the plate to the cutter edge. The test is first conducted
at 3.25" drop. After 10 successful drops, the weight release height
is increased to 6.5" (26.2 Joules) with the cutter being checked
for damage after each drop.
[0038] Experiments with 32 runs with the cutter of the present
invention give an average impact strength to initial failure of
279.6 Joules with a standard deviation of 97.5 Joules. In another
set of runs (4 totals) after initial failure, the average impact
strength to final failure is 620.8 Joules, with a standard
deviation of 68.75 Joules. The cutters of the present invention
demonstrate surprising and significant improvement over the cutter
of prior art. Experiments with 17 runs employing the cutters of the
prior art give an impact strength to final failure of 155.3 Joules,
and a standard deviation of 83.60 Joules.
[0039] FIGS. 3A and 3B compare a standard cutter in the prior art
(FIG. 3A) and the high performance cutter of this example (FIG.
3B). As shown in the photographs, minimal impact damage is seen
even at 653 joules (with micro-chippage failure) in the high
performance cutter of the invention while the standard cutter shows
extensive diamond table spalling at 157 Joules.
[0040] Parkson Mill Impact Resistance Test: This test is to
estimate the performance of the cutter on a chamfer piece, with
each piece having a carbide chamfer of greater than about 0.2 mm,
less than 1.0 mm radial or 45.degree. on the locating base. The
Diamond table has a 0.012" chamfer. In this test, the cutter
(chamfered edge) sample is mounted in a steel holder, with Rake
angle to work piece 7 deg radial/12 degrees axial. The cutter is
rotated and cuts in an interrupted fashion at a depth of 0.150" and
transverse distance of 0.010" through a granite work piece at a
cutting speed of 320 rpm and feed rate of about 3" per min. (7.62
cm/min). The test is stopped when the diamond table fails, and the
number of impacts (entries into the log) counted.
1 Average Tool Overall tool Run # Efficiency Efficiency Sample type
1 7942.9 8896.3 Prior art 2 3292.3 2556.3 Prior art 3 7158.6 6394.4
Prior art 4 3683.3 3191.4 Prior art 5 8519.6 5590.2 Prior art 6
5455.2 7082.5 Prior art 7 4225 4050.6 High Impact 8 8519.5 5590.2
High Impact 9 3378.8 2753.3 High Impact 10 4475.7 3105.5 High
Impact 11 4169.1 3336 High Impact 12 3038.8 2596.7 High Impact
[0041] Abrasion Resistance Test: In this test to measure the
abrasion resistance, with each piece having a carbide chamfer of
greater than about 0.2 mm, less than 1.0 mm radial or 45.degree. on
the locating base. First, a granite log is fitted to a lathe. The
cutter (sharp edge) is mounted into a steel support. The cutter
(rake angle 10 degrees) is run across the rotating log with a depth
of cut of 0.010" at a speed of 300 surface feet per minute (sfpm).
The size of the wear land on the cutter is measured after each pass
of the log. The volume of material removed from the log is
measured. The values are plotted against each other giving the
abrasion resistance of the cutter.
[0042] Abrasion resistance of the cutter has been calculated,
statistical anlyses are conducted and shown in the anova below. The
p-value between the high performance and standard cutter indicates
the difference in abrasion, while somewhat lower, is not
significant. When testing the cutters of this invention, is
interesting to note the presence of striations or grooves in the
log where the whole crystals have taken material away. This feature
indicates that the volume of material removed is greater than
calculated using the typical two-dimensional measurement. The test
is conducted with the Barre Granite Workpiece (Abrasion Resistance
Test).
2 Analysis of Variance for Average Source DF SS MS F P C5 1 5665002
5665002 1.28 0.283 Error 10 44086466 4408647 Total 11 49751468
Individual 95% CIs For Mean Based on Pooled Std. Dev Level N Mean
Std. Dev --+---------+---------+---------+---- HighP 6 4634 1981
(------------*------------) Standard 6 6009 2212
(------------*------------) --+---------+---------+---------+-- ---
Pooled Std. 2100 3000 4500 6000 7500 Dev =
[0043] While the invention has been described with reference to a
preferred embodiment, those skilled in the art will understand that
various changes may be made and equivalents may be substituted for
elements thereof without departing from the scope of the
invention.
* * * * *