U.S. patent application number 15/540747 was filed with the patent office on 2017-12-21 for superhard components and powder metallurgy methods of making the same.
The applicant listed for this patent is Element Six (UK) Limited. Invention is credited to Dong WANG.
Application Number | 20170361424 15/540747 |
Document ID | / |
Family ID | 52471683 |
Filed Date | 2017-12-21 |
United States Patent
Application |
20170361424 |
Kind Code |
A1 |
WANG; Dong |
December 21, 2017 |
SUPERHARD COMPONENTS AND POWDER METALLURGY METHODS OF MAKING THE
SAME
Abstract
A method of forming a super hard polycrystalline construction
comprises forming a liquid suspension of a first mass of
nano-ceramic particles and a mass of particles or grains of super
hard material having an average particle or grain size of 1 or more
microns, dispersing the particles or grains in the liquid
suspension to form a substantially homogeneous suspension, drying
the suspension to form an admix of the nano-ceramic and super hard
grains or particles, and forming a pre-sinter assembly comprising
the admix. The pre-sinter assembly is then sintered to form a body
of polycrystalline super hard material comprising a first fraction
of super hard grains and a second fraction, the nano-ceramic
particles forming the second fraction. The super hard grains are
spaced along at least a portion of the peripheral surface by one or
more nano-ceramic grains, the super hard grains having a greater
average grain size than that of the grains in the second fraction
which have an average size of less than around 999 nm.
Inventors: |
WANG; Dong; (Oxfordshire,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Element Six (UK) Limited |
Oxfordshire |
|
GB |
|
|
Family ID: |
52471683 |
Appl. No.: |
15/540747 |
Filed: |
December 30, 2015 |
PCT Filed: |
December 30, 2015 |
PCT NO: |
PCT/EP2015/081446 |
371 Date: |
June 29, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C04B 2235/5436 20130101;
C04B 2237/401 20130101; B22F 2998/10 20130101; C04B 2235/5445
20130101; C22C 2026/008 20130101; C04B 2237/363 20130101; C04B
2235/40 20130101; C04B 2235/427 20130101; E21B 10/567 20130101;
C22C 2026/005 20130101; B22F 2998/10 20130101; C04B 2235/386
20130101; C22C 2026/007 20130101; B24D 18/0009 20130101; C22C
2026/006 20130101; C04B 2235/3847 20130101; B22F 3/14 20130101;
B22F 9/026 20130101; B22F 3/1017 20130101; C22C 26/00 20130101;
B22F 2009/044 20130101; B22F 9/026 20130101; B22F 7/06 20130101;
B22F 2005/001 20130101; C04B 2235/96 20130101; C04B 37/021
20130101; B22F 1/0014 20130101; C04B 2235/5472 20130101; C04B
35/528 20130101; C04B 35/6264 20130101; C04B 35/62655 20130101;
C04B 35/645 20130101 |
International
Class: |
B24D 18/00 20060101
B24D018/00; B22F 9/02 20060101 B22F009/02; B22F 1/00 20060101
B22F001/00; C22C 26/00 20060101 C22C026/00; B22F 7/06 20060101
B22F007/06 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 31, 2014 |
GB |
1423409.0 |
May 21, 2015 |
GB |
1508726.5 |
Claims
1. A knob adapted for insertion into the hollow end of a sports
stick, the knob comprising a central longitudinal axis, a tang for
insertion into the hollow end of the sports stick, a grip adapted
for being grasped by the hand of an athlete, and a step between the
tang and the grip adapted for abutting the end surface of the
hollow end of the sports stick when the tang is inserted therein,
the grip comprising a grip end distal to the tang, a dorsal cantle
region and a ventral cantle region, the dorsal and ventral cantle
regions being between the tang and the grip end and on opposing
sides of an imaginary coronal plane containing the central
longitudinal axis and divided by an imaginary sagittal plane that
contains the central longitudinal axis and is orthogonal to the
imaginary coronal plane, the dorsal and ventral cantle regions each
providing a curved support surface for the hand of the athlete when
the athlete is gripping the sports stick, the dorsal cantle region
and the ventral cantle region each having a radius of curvature in
the sagittal plane, the radius of curvature of the ventral cantle
region being greater than the radius of curvature of the dorsal
cantle region.
2. The knob of claim 1 wherein a ratio of the radius of curvature
of the ventral cantle region to the radius of curvature of the
dorsal cantle region is (i) at least 2:1, respectively; or (ii) at
least 3:1, respectively, or (iii) at least 5:1, respectively.
3-4. (canceled)
5. The knob of claim 1 wherein a ratio of the radius of curvature
of the ventral cantle region to the radius of curvature of the
dorsal cantle region is (i) less than 20:1; or (ii) less than 15:1;
or (iii) less than 10:1.
6-7. (canceled)
8. The knob of claim 1 wherein the imaginary sagittal plane bisects
each of the dorsal and the ventral cantle regions into symmetrical
halves, respectively.
9. A knob adapted for insertion into the hollow end of a sports
stick, the knob comprising a central longitudinal axis, a tang for
insertion into the hollow end of the sports stick, a grip adapted
for being grasped by the hand of an athlete, and a step between the
tang and the grip adapted for abutting the end surface of the
hollow end of the sports stick when the tang is inserted therein,
the grip comprising a grip end distal to the tang, a dorsal cantle
region and a ventral cantle region, the dorsal and ventral cantle
regions being between the tang and the grip end and on opposing
sides of an imaginary coronal plane containing the central
longitudinal axis and bisected by an imaginary sagittal plane that
contains the central longitudinal axis and is orthogonal to the
imaginary coronal plane, the dorsal and ventral cantle regions each
providing a curved support surface for the hand of the athlete when
the athlete is gripping the sports stick, wherein the dorsal cantle
region and ventral cantle region are asymmetric relative to each
other about the coronal plane and the sagittal plane bisects each
of the ventral and the dorsal cantle regions into symmetrical
halves, respectively.
10. The knob of claim 1 wherein the ventral cantle region smoothly
transitions about the central longitudinal axis to the dorsal
cantle region.
11. The knob of claim 1 wherein the grip end has a circumference
that (i) is at least 110% of the circumference of the neck; or (ii)
at least 150% of the circumference of the neck; or (iii) at least
200% of the circumference of the neck; or (iv) at least 300% of the
circumference of the neck.
12-14. (canceled)
15. The knob of any of claim 1 wherein the tang has a length
measured along the central longitudinal axis of about 2 to about 12
inches, and optionally wherein the tang has an end that is beveled
at an angle of about 30.degree. to 60.degree. from the longitudinal
sides of the tang and toward the longitudinal central axis to allow
for easier initial guided insertion of the tang into the hollow end
of the stick.
16. (canceled)
17. The knob of claim 1 wherein (i) the grip has a length, as
measured along central longitudinal axis 1.2, that is about 5 to
about 95% of the length of the knob and the tang has a
complementary length, as measured along the central longitudinal
axis, that is about 95 to about 5% of the length of the knob; or
(ii) the grip has a length, as measured along central longitudinal
axis 1.2, that is about 15 to about 85% of the length of the knob
and the tang has a complementary length, as measured along the
central longitudinal axis, that is about 85 to about 15% of the
length of the knob; or (iii) the grip has a length, as measured
along central longitudinal axis 1.2, that is about 25 to about 75%
of the length of the knob and the tang has a complementary length,
as measured along the central longitudinal axis, that is about 75
to about 25% of the length of the knob; or (iv) the grip has a
length, as measured along central longitudinal axis 1.2, that is
about 35 to about 65% of the length of the knob and the tang has a
complementary length, as measured along the central longitudinal
axis, that is about 65 to about 35% of the length of the knob; or
(v) the grip has a length, as measured along central longitudinal
axis 1.2, that is about 40 to about 60% of the length of the knob
and the tang has a complementary length, as measured along the
central longitudinal axis, that is about 60 to about 40% of the
length of the knob.
18-21. (canceled)
22. The knob of claim 1 wherein the grip comprises a neck between
the flange and the tang.
23. The knob of claim 22 wherein (i) the neck has a length measured
along the central longitudinal axis of at least about 0.25 inches,
or (ii) the neck has a length measured along the central
longitudinal axis in the range of about 0.25 to about 4 inches, or
(iii) the neck has a length measured along the central longitudinal
axis in the range of about 1 to about 4 inches, or (iv) the neck
has a length measured along the central longitudinal axis in the
range of about 1 to about 2 inches.
24-26. (canceled)
27. The knob of claim 1 wherein (i) the knob comprises a ceramic,
metal, polymer, composite, wood or a composite or laminate thereof,
or (ii) the knob comprises a ceramic, metal, polymer, composite, or
a composite or laminate thereof.
28. (canceled)
29. A combination of a sport stick and a knob, the knob
corresponding to the knob of claim 1 and being inserted into a
hollow end of the sport stick.
30. The combination of claim 29 wherein (i) the sport stick is a
hockey stick, a lacrosse stick, a golf club, or a baseball bat; or
(ii) the sport stick is a hockey stick, a lacrosse stick, or a golf
club.
31. (canceled)
32. A combination of a hockey stick and a knob, the knob
corresponding to the knob of claim 1 and being inserted into a
hollow end of the hockey stick wherein the ventral cantle region of
knob is on the same side of the hockey stick as the blade of the
hockey stick.
33. A combination of (i) a lacrosse stick and a knob, the knob
corresponding to the knob of claim 1 and being inserted into a
hollow end of the lacrosse stick wherein the ventral cantle region
of knob is on the same side of the lacrosse stick as the net-side
of the head of the lacrosse stick; or (ii) a golf club and a knob,
the knob corresponding to the knob of claim 1 and being inserted
into a hollow end of the golf club wherein the ventral cantle
region of knob and the head of the golf club are on the same side
of the imaginary sagittal plane and the dorsal cantle region and
the head of the golf club are on opposite sides of the imaginary
sagittal plane; or (iii) a combination of a baseball bat and a
knob, the knob corresponding to the knob of any of claims 1-28 and
being inserted into a hollow end of the baseball bat wherein the
tang and step have a circular cross-section.
34-35. (canceled)
36. The combination of claim 33 wherein the knob comprises a cavity
at grip end of the knob sized to accommodate a motion sensor.
37. The combination of claim 33 wherein the knob comprises a cavity
at grip end of the knob sized to accommodate a motion sensor, and
the combination further comprises an electronic motion sensor
housed in the cavity.
38. The combination of claim 29 wherein the knob is securely
affixed to the sports stick, optionally by welding, screws, nails,
staples, glue, adhesive, heat-activated glue, or epoxy.
39. (canceled)
Description
FIELD
[0001] This disclosure relates to super hard constructions and
methods of making such constructions, particularly but not
exclusively to constructions comprising polycrystalline diamond
(PCD) structures attached to a substrate, and tools comprising the
same, particularly but not exclusively for use in rock degradation
or drilling, or for boring into the earth.
BACKGROUND
[0002] Polycrystalline super hard materials, such as
polycrystalline diamond (PCD) may be used in a wide variety of
tools for cutting, machining, drilling or degrading hard or
abrasive materials such as rock, metal, ceramics, composites and
wood-containing materials. In particular, tool inserts in the form
of cutting elements comprising PCD material are widely used in
drill bits for boring into the earth to extract oil or gas. The
working life of super hard tool inserts may be limited by fracture
of the super hard material, including by sinning and chipping, or
by wear of the tool insert.
[0003] Cutting elements such as those for use in rock drill bits or
other cutting tools typically have a body in the form of a
substrate which has an interface end/surface and a super hard
material which forms a cutting layer bonded to the interface
surface of the substrate by, for example, a sintering process. The
substrate is generally formed of a tungsten carbide-cobalt alloy,
sometimes referred to as cemented tungsten carbide and the super
hard material layer is typically polycrystalline diamond (PCD), or
a thermally stable product TSP material such as thermally stable
polycrystalline diamond.
[0004] Polycrystalline diamond (PCD) is an example of a super hard
material (also called a super abrasive material or ultra hard
material) comprising a mass of substantially inter-grown diamond
grains, forming a skeletal mass defining interstices between the
diamond grains. PCD material typically comprises at least about 80
volume % of diamond and is conventionally made by subjecting an
aggregated mass of diamond grains to an ultra-high pressure of
greater than about 5 GPa, and temperature of at least about
1,200.degree. C., for example. A material wholly or partly filling
the interstices may be referred to as filler or binder
material.
[0005] PCD is typically formed in the presence of a sintering aid
such as cobalt, which promotes the inter-growth of diamond grains.
Suitable sintering aids for PCD are also commonly referred to as a
solvent-catalyst material for diamond, owing to their function of
dissolving, to some extent, the diamond and catalysing its
re-precipitation. A solvent-catalyst for diamond is understood be a
material that is capable of promoting the growth of diamond or the
direct diamond-to-diamond inter-growth between diamond grains at a
pressure and temperature condition at which diamond is
thermodynamically stable. Consequently the interstices within the
sintered PCD product may be wholly or partially filled with
residual solvent-catalyst material. Most typically, PCD is formed
on a cobalt-cemented tungsten carbide substrate, which provides a
source of cobalt solvent-catalyst for the PCD. Materials that do
not promote substantial coherent intergrowth between the diamond
grains may themselves form strong bonds with diamond grains, but
are not suitable solvent--catalysts for PCD sintering.
[0006] Cemented tungsten carbide which may be used to form a
suitable substrate is formed from carbide particles being dispersed
in a cobalt matrix by mixing tungsten carbide particles/grains and
cobalt together then heating to solidify. To form the cutting
element with a super hard material layer such as PCD, diamond
particles or grains are placed adjacent the cemented tungsten
carbide body in a refractory metal enclosure such as a niobium
enclosure and are subjected to high pressure and high temperature
so that inter-grain bonding between the diamond grains occurs,
forming a polycrystalline super hard diamond layer.
[0007] In some instances, the substrate may be fully cured prior to
attachment to the super hard material layer whereas in other cases,
the substrate may be green, that is, not fully cured. In the latter
case, the substrate may fully cure during the HTHP sintering
process. The substrate may be in powder form and may solidify
during the sintering process used to sinter the super hard material
layer.
[0008] Ever increasing drives for improved productivity in the
earth boring field place ever increasing demands on the materials
used for cutting rock. Specifically, super hard materials, such as
PCD materials, with improved abrasion and impact resistance are
required to achieve faster cut rates and longer tool life.
[0009] Cutting elements or tool inserts comprising PCD material are
widely used in drill bits for boring into the earth in the oil and
gas drilling industry. Rock drilling and other operations require
high abrasion resistance and impact resistance. One of the factors
limiting the success of the polycrystalline diamond (PCD) abrasive
cutters is the generation of heat due to friction between the PCD
and the work material. This heat causes the thermal degradation of
the diamond layer. The thermal degradation increases the wear rate
of the cutter through increased cracking and spalling of the PCD
layer as well as back conversion of the diamond to graphite causing
increased abrasive wear.
[0010] Methods used to improve the abrasion resistance of a PCD
composite often result in a decrease in impact resistance of the
composite.
[0011] The most wear resistant grades of PCD usually suffer from a
catastrophic fracture of the cutter before it has worn out. During
the use of these cutters, cracks grow until they reach a critical
length as which catastrophic failure occurs, namely, when a large
portion of the PCD breaks away in a brittle manner. These long,
fast growing cracks encountered during use of conventionally
sintered PCD, result in short tool life.
[0012] Furthermore, despite their high strength, polycrystalline
diamond (PCD) materials are usually susceptible to impact fracture
due to their low fracture toughness. Improving fracture toughness
without adversely affecting the material's high strength and
abrasion resistance is a challenging task.
[0013] There is therefore a need for a super hard composite such as
a PCD composite that has good or improved abrasion, fracture and
impact resistance and a method of forming such composites.
SUMMARY
[0014] Viewed from a first aspect there is provided a method of
forming a super hard polycrystalline construction, comprising:
[0015] forming a liquid suspension of a first mass of nano-ceramic
particles and a mass of particles or grains of super hard material
having an average particle or grain size of 1 or more microns;
[0016] dispersing the nano-ceramic particles and mass of super hard
particles or grains in the liquid suspension to form a
substantially homogeneous suspension; [0017] drying the suspension
to form an admix of the nano-ceramic particles and super hard
grains or particles; [0018] forming a pre-sinter assembly
comprising the admix; [0019] treating the pre-sinter assembly in
the presence of a catalyst/solvent material for the super hard
grains at an ultra-high pressure of around 5 GPa or greater and a
temperature to sinter together the grains of super hard material to
form a body of polycrystalline super hard material comprising a
first fraction of super hard grains and a second fraction, the
super hard grains exhibiting inter-granular bonding and defining a
plurality of interstitial regions therebetween; [0020] the
nano-ceramic particles forming the second fraction; wherein [0021]
the super hard grains in the first fraction are spaced along at
least a portion of the peripheral surface by one or more
nano-ceramic grains in the second fraction; [0022] the super hard
grains in the first fraction having a greater average grain size
than the average grain size of the grains in the second fraction,
the average size of the grains in the second fraction being less
than around 999 nm and the average grain size of the grains of
superhard material in the first fraction being around 1 micron or
more.
[0023] Viewed from a second aspect there is provided a super hard
polycrystalline construction comprising: [0024] a body of
polycrystalline super hard material comprising a first fraction of
super hard grains and a second fraction of nano-ceramic material;
[0025] the super hard grains in the first fraction having a
peripheral surface; wherein [0026] the super hard grains in the
first fraction are spaced along at least a portion of their
peripheral surface by a plurality of nano-ceramic grains or
clusters of nano-ceramic grains; wherein the average grain size of
the super hard grains in the first fraction is around 1 micron or
more.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Various versions will now be described by way of example and
with reference to the accompanying drawings in which:
[0028] FIG. 1 is a perspective view of an example PCD cutter
element or construction for a drill bit for boring into the
earth;
[0029] FIG. 2 is a schematic cross-section of a portion of a
conventional PCD micro-structure with interstices between the
inter-bonded diamond grains filled with a non-diamond phase
material;
[0030] FIG. 3 is a schematic cross-section of a portion of an
example PCD micro-structure;
[0031] FIG. 4 is a plot showing the results of a vertical borer
test comparing a conventional PCD cutter element and an example
cutter element;
[0032] FIG. 5 is a plot showing the results of a vertical borer
test comparing a conventional PCD cutter element and two example
cutter elements which contained residual catalyst binder in the
interstitial spaces (unleached): and
[0033] FIG. 6 is a plot showing the results of a vertical borer
test comparing a conventional PCD cutter element and an example
cutter element from which residual catalyst binder in the
interstitial spaces had been removed (leached).
[0034] The same references refer to the same general features in
all the drawings.
DESCRIPTION
[0035] As used herein, a "super hard material" is a material having
a Vickers hardness of at least about 28 GPa. Diamond and cubic
boron nitride (cBN) material are examples of super hard
materials.
[0036] As used herein, a "super hard construction" means a
construction comprising a body of polycrystalline super hard
material. In such a construction, a substrate may be attached
thereto or alternatively the body of polycrystalline material may
be free-standing and unbacked.
[0037] As used herein, polycrystalline diamond (PCD) is a type of
polycrystalline super hard (PCS) material comprising a mass of
diamond grains, a substantial portion of which are directly
inter-bonded with each other and in which the content of diamond is
at least about 80 volume percent of the material. As used herein,
"interstices" or "interstitial regions" are regions between the
diamond grains of PCD material. In some examples of PCD material,
interstices between the diamond grains may be at least partly
filled with a binder material comprising a catalyst for diamond. In
some examples of PCD material, interstices or interstitial regions
may be substantially or partially filled with a material other than
diamond, or they may be substantially empty. PCD material may
comprise at least a region from which catalyst material has been
removed from the interstices, leaving interstitial voids between
the diamond grains.
[0038] A "catalyst material" for a super hard material is capable
of promoting the growth or sintering of the super hard
material.
[0039] The term "substrate" as used herein means any substrate over
which the super hard material layer is formed. For example, a
"substrate" as used herein may be a transition layer formed over
another substrate.
[0040] As used herein, the term "integrally formed" regions or
parts are produced contiguous with each other and are not separated
by a different kind of material.
[0041] An example of a super hard construction is shown in FIG. 1
and includes a cutting element 1 having a layer of super hard
material 2 formed on a substrate 3. The substrate 3 may be formed
of a hard material such as cemented tungsten carbide. The super
hard material 2 may be, for example, polycrystalline diamond (PCD),
or a thermally stable product such as thermally stable PCD (TSP).
The cutting element 1 may be mounted into a bit body such as a drag
bit body (not shown) and may be suitable, for example, for use as a
cutter insert for a drill bit for boring into the earth.
[0042] The exposed top surface of the super hard material opposite
the substrate forms the cutting face 4, also known as the working
surface, which is the surface which, along with its edge 6,
performs the cutting in use.
[0043] At one end of the substrate 3 is an interface surface 8 that
forms an interface with the super hard material layer 2 which is
attached thereto at this interface surface. As shown in the example
of FIG. 1, the substrate 3 is generally cylindrical and has a
peripheral surface 14 and a peripheral top edge 16.
[0044] The super hard material may be, for example, polycrystalline
diamond (PCD) and the super hard particles or grains may be of
natural or synthetic origin.
[0045] The substrate 3 may be formed of a hard material such as a
cemented carbide material and may be, for example, cemented
tungsten carbide, cemented tantalum carbide, cemented titanium
carbide, cemented molybdenum carbide or mixtures thereof. The
binder metal for such carbides suitable for forming the substrate 3
may be, for example, nickel, cobalt, iron or an alloy containing
one or more of these metals. Typically, this binder will be present
in an amount of 10 to 20 mass %, but this may be as low as 6 mass %
or less. Some of the binder metal may infiltrate the body of
polycrystalline super hard material 2 during formation of the
compact 1,
[0046] As shown in FIG. 2, during formation of a conventional
polycrystalline composite construction, the diamond grains are
directly inter-bonded to adjacent grains and the interstices 24
between the grains 22 of super hard material such as diamond grains
in the case of PCD may be at least partly filled with a non-super
hard phase material. This non-super hard phase material, also known
as a filler material, may comprise residual catalyst/binder
material, for example cobalt, nickel or iron. The typical average
grain size of the diamond grains 22 is larger than 1 micron and the
grain boundaries between adjacent grains is therefore typically
between micron-sized diamond grains, as shown in FIG. 2.
[0047] The working surface or "rake face" 4 of the polycrystalline
composite construction 1 is the surface or surfaces over which the
chips of material being cut flow when the cutter is used to cut
material from a body, the rake face 4 directing the flow of newly
formed chips. This face 4 is commonly also referred to as the top
face or working surface of the cutting element as the working
surface 4 is the surface which, along with its edge 6, is intended
to perform the cutting of a body in use. It is understood that the
term "cutting edge", as used herein, refers to the actual cutting
edge, defined functionally as above, at any particular stage or at
more than one stage of the cutter wear progression up to failure of
the cutter, including but not limited to the cutter in a
substantially unworn or unused state.
[0048] As used herein, "chips" are the pieces of a body removed
from the work surface of the body being cut by the polycrystalline
composite construction 1 in use.
[0049] As used herein, a "wear scar" is a surface of a cutter
formed in use by the removal of a volume of cutter material due to
wear of the cutter. A flank face may comprise a wear scar. As a
cutter wears in use, material may progressively be removed from
proximate the cutting edge, thereby continually redefining the
position and shape of the cutting edge, rake face and flank as the
wear scar forms.
[0050] FIG. 3 is a cross-section through an example of
polycrystalline super hard material forming the super hard layer 2
of FIG. 1 showing, schematically, the microstructure. The
polycrystalline material comprises a first phase dispersed in the
super hard phase 40 and comprising super hard grains 40 spaced by a
second phase comprising nano-sized particles or clusters of
particles 42 formed of a ceramic material that, in some examples,
may not chemically react with the super hard grains, and/or not
inter-grow. Residual catalyst/binder phase 43 may be disposed
between the first and second phases 40, 42. The second phase 42 may
comprise, for example, any one or more of an oxide material, a
carbide material, alumina, zirconia, yttria, silica, tantalum
oxide, cBN, PCBN, boron nitride, tungsten carbide, hafnium carbide,
zirconium carbide, silicon carbide, silicon nitride or any
combination thereof. The grain size of the dispersed second phase
particles 42 may, in some examples, be less than around 999 nm, and
in some examples 100 nm or less, and/or in the examples comprising
clusters of ceramic particles, the average size of the clusters of
nano-sized particles may be, for example around 5 microns or less
and in some examples, around 500 nm or less.
[0051] In some examples, these dispersed second phase particles 42
may be localized inside the binder pools or in between the grains
of the super hard particles, depending on the respective sizes.
[0052] The grains of super hard material may be, for example,
diamond grains or particles. In the starting mixture prior to
sintering they may be, for example, bimodal, that is, the feed
comprises a mixture of a coarse fraction of diamond grains and a
fine fraction of diamond grains. In some examples, the coarse
fraction may have, for example, an average particle/grain size
ranging from about 10 to 60 microns. By "average particle or grain
size" it is meant that the individual particles/grains have a range
of sizes with the mean particle/grain size representing the
"average". The average particle/grain size of the fine fraction is
less than the size of the coarse fraction. For example, the fine
fraction may have an average grain size of between around 1/10 to
6/10 of the size of the coarse fraction, and may, in some examples,
range for example between about 0.1 to 20 microns.
[0053] In some examples, the weight ratio of the coarse diamond
fraction to the fine diamond fraction may range from about 50% to
about 97% coarse diamond and the weight ratio of the fine diamond
fraction may be from about 3% to about 50%. In other examples, the
weight ratio of the coarse fraction to the fine fraction may range
from about 70:30 to about 90:10.
[0054] In further examples, the weight ratio of the coarse fraction
to the fine fraction may range for example from about 60:40 to
about 80:20.
[0055] In some examples, the particle size distributions of the
coarse and fine fractions do not overlap and in some examples the
different size components of the compact are separated by an order
of magnitude between the separate size fractions making up the
multimodal distribution.
[0056] Some examples consist of a wide bi-modal size distribution
between the coarse and fine fractions of super hard material, but
some examples may include three or even four or more size modes
which may, for example, be separated in size by an order of
magnitude, for example, a blend of particle sizes whose average
particle size is 20 microns, 2 microns, 200 nm and 20 nm.
[0057] Sizing of diamond particles/grains into fine fraction,
coarse fraction, or other sizes in between, may be through known
processes such as jet-milling of larger diamond grains and the
like.
[0058] In examples where the super hard material is polycrystalline
diamond material, the diamond grains used to form the
polycrystalline diamond material may be natural and/or
synthetic.
[0059] In some examples, the binder catalyst/solvent may comprise
cobalt or some other iron group elements, such as iron or nickel,
or an alloy thereof. Carbides, nitrides, borides, and oxides of the
metals of Groups IV-VI in the periodic table are other examples of
non-diamond material that might be added to the sinter mix. In some
examples, the binder/catalyst/sintering aid may be Co.
[0060] The cemented metal carbide substrate may be conventional in
composition and, thus, may be include any of the Group IVB, VB, or
VIB metals, which are pressed and sintered in the presence of a
binder of cobalt, nickel or iron, or alloys thereof. In some
examples, the metal carbide is tungsten carbide.
[0061] The cutter of FIG. 1 according to a first version having the
microstructure of FIG. 3 may be fabricated, for example, as
follows.
[0062] A mass of hard nano-ceramic particle materials, such as nano
cBN, nano tungsten carbide, nano boron carbide, nano silicon
carbide, nano silicon nitride having, for example, an average grain
size of less than around 100 nm, is thoroughly dispersed in a
liquid, such as (deionized) water or an organic solvent, for
example ethanol, with or without surfactants using a sonication
process by inserting an ultrasonic probe into the liquid to form a
suspension. Alternatively or in addition, a cluster of such hard
nano-ceramic particles may be pre-formed using a conventional nano
precipitation technique and dispersed in such a liquid to form a
suspension. The clusters may have, for example, an average size of
around 5 microns or less, or in some examples around 500 nm or
less. Micron sized diamond grits having an average grain size of
greater than 1 micron are added to the mixture and a sintering
agent such as cobalt may also be added. The mixture is then
subjected to a further sonication process by applying the
ultrasonic probe into the mixture for a further period of time to
form a homogeneous mixture. The resulting mixture is then dried
using a fast drying process to maintain the homogeneity. An example
of a suitable technique for drying the suspension is freeze drying
using, for example, liquid nitrogen, or spray drying, or spray
granulation to form a substantially homogeneously mixed admix
powder in which the nano-ceramic particles or clusters are coated
on/attached to micron-sized diamond grits. The admix powder is then
sintered under conventional diamond sintering conditions, for
example at a pressure of around 6.8 GPa, and temperature of around
1300 degrees C., in some examples with a preformed WC substrate to
form a PCD structure such as that shown in FIG. 3 in which the
nano-ceramic particles or clusters 42 are located between grain
boundaries of the larger diamond grains 40,
[0063] Various techniques may be used to achieve this dispersion
and homogenous mixture such as ultrasonic dispersing, ball milling,
homogenization, and jet milling techniques.
[0064] Also, a fast drying process to dry the nano-ceramic/diamond
suspension without agglomeration may assist in achieving the
desired microstructure in the sintered product. Suitable drying
techniques to assist in inhibiting agglomeration of the materials
during drying may include freeze drying, spray freeze drying, spray
drying, and spray granulation or spray freeze granulation.
[0065] In the example in which a spray drying technique is used, a
suitable inlet temperature may be, for example, around 120 deg C.,
and a suitable outlet temperature of around 50-56 deg C., and a
feeding rate of around 5.8 ml/min may be used.
[0066] In the example in which a freeze drying technique is used,
the admix may be in the form of a homogeneous paste which is frozen
using liquid nitrogen, and is then placed into a freeze dryer for
several days until the paste is thoroughly dried. The freeze drying
conditions may be optimized for different solvents, for example,
for deionized water, the preferred operation temperature is -55 deg
C. plus/minus 5 deg C., and the preferred pressure is between
around 50 to 500 microbar.
[0067] In some examples, the catalyst binder such as cobalt may
instead be added to the dried admix powder rather than be included
in the liquid suspension.
[0068] In some examples, a stabilizer such as a polymeric
stabiliser for example a surfactant may be added to the suspension
mixture. The surfactant may be, for example, a non-ionic or
cationic surfactant. Also, a binding material such as polyvinyl
alcohol may be added to the suspension mixture to assist in
inhibiting agglomeration.
[0069] The micron-sized diamond particles or grains may be
subjected to a heat treatment or acid treatment prior to adding
these to the suspension mixture to clean the particles or grains by
removing impurities. A suitable heat treatment temperature for
micron-sized diamond grits may be, for example, between around 1000
to around 1300 deg C., or between around 1100 to around 1300 deg
C., or between around 1200 to around 1300 deg C.
[0070] In some examples, the admix material comprising the
nano-ceramics and micron-sized diamond admix, and the carbide
material for forming the substrate plus any additional sintering
aid/binder/catalyst may be applied as powders and sintered
simultaneously in a single UHP/HT process. The admix of
nano-ceramic and micron sized diamond grains, and mass of carbide
powder material are placed in an HP/HT reaction cell assembly and
subjected to HP/HT processing. The HP/HT processing conditions
selected are sufficient to effect intercrystalline bonding between
the diamond grains as well as, optionally, the joining of sintered
particles to the cemented metal carbide support. In one example,
the processing conditions generally involve the imposition for
about 3 to 120 minutes of a temperature of at least about 1200
degrees C. and an ultra-high pressure of greater than about 5
GPa.
[0071] In another example, the substrate may be pre-sintered in a
separate process before being bonded to the polycrystalline
material in the HP/HT press during sintering of the ultrahard
polycrystalline material.
[0072] In a further example, both the substrate and a body of
polycrystalline super hard material are pre-formed. The preformed
body of polycrystalline super hard material is placed in the
appropriate position on the upper surface of the preformed carbide
substrate (incorporating a binder catalyst), and the assembly is
located in a suitably shaped canister. The assembly is then
subjected to high temperature and pressure in a press, the order of
temperature and pressure being again, at least around 1200 degrees
C. and 5 GPa respectively. During this process the solvent/catalyst
migrates from the substrate into the body of super hard material
and acts as a binder-catalyst to effect intergrowth in the layer
and also serves to bond the layer of polycrystalline super hard
material to the substrate.
[0073] In some examples, the cemented carbide substrate may be
formed of tungsten carbide particles bonded together by the binder
material, the binder material comprising an alloy of Co, Ni and Cr.
The tungsten carbide particles may form at least 70 weight percent
and at most 95 weight percent of the substrate. The binder material
may comprise between about 10 to 50 wt. % Ni, between about 0.1 to
10 wt. % Cr, and the remainder weight percent comprises Co.
[0074] The PCD construction 1 described with reference to FIGS. 1
and 3, may be further processed after sintering. For example,
catalyst material may be removed from a region of the PCD structure
adjacent the working surface or the side surface or both the
working surface and the side surface. This may be achieved by
treating the PCD structure with acid to leach out catalyst material
from between the diamond grains, or by other methods such as
electrochemical methods. A thermally stable region, which may be
substantially porous, extending a depth of at least about 50
microns or at least about 100 microns from a surface of the PCD
structure, may thus be formed which may further enhance the thermal
stability of the PCD element.
[0075] Furthermore, the PCD body in the structure of FIG. 1
comprising a PCD structure bonded to a cemented carbide support
body may be treated or finished by, for example, grinding, to
provide a PCD element which is substantially cylindrical and having
a substantially planar working surface, or a generally domed,
pointed, rounded conical or frusto-conical working surface. The PCD
element may be suitable for use in, for example, a rotary shear (or
drag) bit for boring into the earth, for a percussion drill bit or
for a pick for mining or asphalt degradation.
[0076] In addition, after sintering, the polycrystalline super hard
constructions may be ground to size and may include, if desired, a
chamfer, for example of around 45 degrees and of approximately 0.4
mm height measured parallel to the longitudinal axis of the
construction.
[0077] Some versions are discussed in more detail below with
reference to the following examples, which are not intended to be
limiting,
EXAMPLE 1
[0078] 3 g of nano cBN having an average particle size of less than
around 100 nm was suspended in 15 ml of ethanol and the suspension
was treated with sonication probe for at least 15 minutes to
thoroughly disperse the nano cBN. In a separate beaker, 1 g of B90
was dissolved into 20 ml ethanol, and then mixed with the nano cBN
dispersion. The mixture was concentrated to 20 ml by evaporating
the excess amount of ethanol in a Rotavap. Following the
concentration, 5 ml of deionized water was introduced into the
ethanol concentration and the nano cBN together with B90 was
precipitated out of the ethanol solution to form nano clusters of
nano cBN.
[0079] In a separate beaker, 67.9 g of diamond grains having an
average grain size of around 22 microns (Grade 22) was suspended in
30 ml deionized water and the nano clusters of nano cBN solution
were then introduced into the suspension. The mixture was gently
stirred with an overhead stirrer for at least half an hour to
obtain nano clusters of nano cBN coated diamond.
[0080] In a separate beaker, 2 g of SP cobalt and 1 g of surfactant
was mixed with 20 ml of deionized water, and subjected to a
sonication process with ultrasonic probe for 15 minutes. 29.1 g of
diamond grains having an average grain size of around 2 microns
(Grade 2) was introduced into the suspension and the suspension was
subjected to a sonication process for a further 5 minutes. This
suspension was then introduced into the suspension comprising the
diamond grains having an average grain size of 22 microns (grade
22) and the resulting mixture was gently stirred with an overhead
stirrer for 10 minutes to form a final admix suspension. The final
admix suspension was spray dried with a BUCHI Mini-290 spray dryer
to remove liquids and form an admix powder. The spray dryer
conditions were:
[0081] Atomization Pressure: 3 Bar
[0082] Inlet temperature: 120.degree. C.
[0083] Outlet temperature: 50-56.degree. C.
[0084] Feeding rate: 5.8 ml/min
[0085] 2.1 g of the admix powder was then placed into a canister
with a pre-formed cemented WC substrate to form a pre-sinter
assembly, which was then loaded into a press and subjected to an
ultra-high pressure and a temperature at which the super hard
material is thermodynamically stable to sinter the super hard
grains. The pressure to which the assembly was subjected was about
6.8 GPa and the temperature was at least about 1,200 degrees
centigrade. The sintered PCD construction was then removed from the
canister.
[0086] A conventional PCD cutter construction formed of the same
mixture of diamond grain sizes (grades) as set out in the above
example, but without adding the nano-ceramic material was prepared
in a conventional manner for forming PCD by mixing using
conventional milling and mixing techniques and the mixture was
sintered with a pre-formed cemented carbide substrate under the
same conditions as above for the example containing the
nano-ceramic additions.
[0087] The prepared PCD constructions formed according to the above
methods were compared in a vertical boring mill test. The results
are shown in FIG. 4.
[0088] The first PCD construction tested was that formed of the
conventional diamond grain mixture (without any nano-ceramic
additions) and the results are shown in FIG. 4 by line 100. The
second PCD construction tested was a first example formed with the
nano-cBN additions described above and the results are shown in
FIG. 4 by line 200.
[0089] In this test, the wear flat area was measured as a function
of the number of passes of the construction boring into the
workpiece and the results obtained are illustrated graphically in
FIG. 4.
[0090] The results provide an indication of the total wear scar
area plotted against cutting length. It will be seen that the PCD
construction formed according to the example (line 200) was able to
achieve a significantly greater cutting length than that occurring
in the conventional PCD compact (shown by line 100 in FIG. 4) which
was subjected to the same test for comparison and the PCD
construction formed according to the example (line 200) was able to
achieve a smaller wear scar area than that occurring in the
conventional PCD compact (shown by line 100 in FIG. 4).
[0091] Thus it will be seen from FIG. 4 that the PCD construction
formed with the inclusion of nano-ceramic material in the admix in
the manner described above from a homogeneously distributed
solution to enable the nano-ceramic to coat the larger diamond
grains as shown in FIG. 3 prior to sintering showed an improvement
in cutting distance and abrasion resistance over the conventional
PCD construction (line 100).
EXAMPLE 2
[0092] 3 g of nano WC having an average particle size of less than
around 100 nm was suspended in 15 ml of ethanol and the suspension
was treated with sonication probe for at least 15 minutes to
thoroughly disperse the nano WC. In a separate beaker, 1 g of B90
was dissolved into 20 ml ethanol, and then mixed with the nano WC
dispersion. The mixture was concentrated to 20 ml by evaporating
the excess amount of ethanol in a Rotavap. Following the
concentration, 5 ml of deionized water was introduced into the
ethanol concentration and the nano WC together with B90 was
precipitated out of the ethanol solution to form nano clusters of
nano WC having an average cluster size of around 1200 nm.
[0093] In a separate beaker, 67.9 g of diamond grains having an
average grain size of around 22 microns (Grade 22) was suspended in
30 ml deionized water and the nano clusters of nano WC solution
were then introduced into the suspension. The mixture was gently
stirred with an overhead stirrer for at least half an hour to
obtain nano clusters of nano WC coated diamond.
[0094] In a separate beaker, 2 g of SP cobalt and 1 g of surfactant
was mixed with 20 ml of deionized water, and subjected to a
sonication process with ultrasonic probe for 15 minutes. 29.1 g of
diamond grains having an average grain size of around 2 microns
(Grade 2) was introduced into the suspension and the suspension was
subjected to a sonication process for a further 5 minutes. This
suspension was then introduced into the suspension comprising the
diamond grains having an average grain size of 22 microns (grade
22) and the resulting mixture was gently stirred with an overhead
stirrer for 10 minutes to form a final admix suspension. The final
admix suspension was spray dried with a BUCHI Mini-290 spray dryer
to remove liquids and form an admix powder. The spray dryer
conditions were:
[0095] Atomization Pressure: 3 Bar
[0096] Inlet temperature: 120.degree. C.
[0097] Outlet temperature: 50-56.degree. C.
[0098] Feeding rate: 5.8 ml/min
[0099] 2.1 g of the admix powder comprising around 3 wt % WC
nano-clusters was then placed into a canister with a pre-formed
cemented WC substrate to form a pre-sinter assembly, which was then
loaded into a press and subjected to an ultra-high pressure and a
temperature at which the super hard material is thermodynamically
stable to sinter the super hard grains. The pressure to which the
assembly was subjected was about 6.8 GPa and the temperature was at
least about 1,200 degrees centigrade. The sintered PCD construction
was then removed from the canister.
[0100] A conventional PCD cutter construction formed of the same
mixture of diamond grain sizes (grades) as set out in the above
example, but without adding the nano-ceramic material was prepared
in a conventional manner for forming PCD by mixing using
conventional milling and mixing techniques and the mixture was
sintered with a pre-formed cemented carbide substrate under the
same conditions as above for the example containing the
nano-ceramic additions.
[0101] The prepared PCD constructions formed according to the above
methods were compared in a vertical boring mill test. The results
are shown in FIG. 5.
[0102] The first PCD construction tested was that formed of the
conventional diamond grain mixture (without any nano-ceramic
additions) and the results are shown in FIG. 5 by line 500. The
second PCD construction tested was a first example formed with the
nano-WC additions described above and the results are shown in FIG.
5 by line 600. A third PCD construction was also tested which was a
further example formed with the nano-WC additions described above
to test repeatability and the results are shown in FIG. 5 by line
700. All samples tested in the test whose results are shown in FIG.
5 were in the unleached state, that is, the samples had not been
subjected to a post synthesis treatment to remove residual binder
catalyst from the interstices.
[0103] As shown in FIG. 5, the two example constructions (600, 700)
showed no reduction on abrasive resistance compared to the
conventional PCD construction in the unleached state.
[0104] An additional sample according to example 2 was produced as
was an additional reference cutter which was formed of the same
mixture of diamond grain sizes (grades) as set out in the above
example 2, but without adding the nano-ceramic material, and it was
prepared in a conventional manner for forming PCD by mixing using
conventional milling and mixing techniques and the mixture was
sintered with a pre-formed cemented carbide substrate under the
same conditions as above for the example containing the
nano-ceramic additions. The constructions were then subjected to an
acid leaching treatment to remove residual catalyst binder from the
interstices. The treated PCD constructions were then compared in a
further vertical boring mill test. The results are shown in FIG.
6.
[0105] In this test, the wear flat area was measured as a function
of the number of passes of the construction boring into the
workpiece and the results obtained are illustrated graphically in
FIG. 6.
[0106] The results provide an indication of the total wear scar
area plotted against cutting length. It will be seen that the PCD
construction formed according to the example (line 800) was able to
achieve a significantly greater cutting length than that occurring
in the conventional PCD compact (shown by line 900 in FIG. 6) which
was subjected to the same test for comparison and the PCD
construction formed according to the example (line 800) was able to
achieve a smaller wear scar area than that occurring in the
conventional PCD compact (shown by line 900 in FIG. 6).
[0107] Thus it will be seen from FIG. 6 that the leached PCD
construction formed with the inclusion of nano-ceramic material in
the admix in the manner described above from a homogeneously
distributed solution to enable the nano-ceramic to coat the larger
diamond grains as shown in FIG. 3 prior to sintering showed an
improvement in cutting distance and abrasion resistance over the
conventional PCD construction (line 900).
[0108] Whilst not wishing to be bound by a particular theory, it is
believed that the fracture performance of PCD may be improved
through the introduction of a nano-sized second phase comprising
hard ceramic materials which may not chemically react with the
super hard grains, and/or may not inter-grow. The second phase,
particularly those formed of a cluster of nano particles, are
believed to promote crack bifurcation or multiple crack fronts in
the PCD material in use, resulting in a redistribution of available
strain energy or energy release rate (G) amongst the various crack
tips, and/or favourably divert cracks in the PCD material. A
material that is able to generate multiple cracks under loading
would behave tougher than a material with only one major crack
since multiple crack fronts ensures that the net energy supplied to
the material is divided between several cracks, resulting in a much
slower rate of crack growth through the material. The end result in
application of the PCD material including such micro-defects is
that, in use, the number of cracks initiated on the wear scar may
be increased as compared to conventional PCD, thus reducing the
strain energy available for each individual crack, hence slowing
the growth rate, and the generation of shorter cracks. The ideal
case is where the wear rate is comparable to the crack growth rate,
in which case no cracks will be visible behind the wear scar
thereby forming a smooth wear scar appearance with no chips or
grains pulled out of the sintered PCD.
[0109] The addition of such a second phase may also have the effect
of increasing the thermal stability of the PCD through the
resultant lower cobalt content in the material of the examples
compared to conventional PCD.
[0110] The size, shape and distribution of these second phase
particles, grains, clusters, granules or agglomerates may be
tailored to the final application of the PCD material. It is
believed possible to improve fracture resistance without
significantly compromising the overall abrasion resistance of the
material, which is desirable for PCD cutting tools.
[0111] Thus, it is believed that one or more examples may provide a
means of toughening PCD material without compromising its high
abrasion resistance and may assist in enabling the creation of
multiple crack-fronts or defects which may help to redistribute or
dissipate the available fracture energy. These defects may also
promote crack bifurcations, which is another energy dissipation
mechanism. The end result is that there may be insufficient energy
available to each individual crack to enable it to propagate
quickly and hence this may significantly slow down the rate of
crack growth.
[0112] The vertical borer test results of these engineered
structures show a considerable increase in PCD cutting tool life
compared to conventional PCD, and with no degradation in abrasion
resistance.
[0113] Observation of the wear scar development during testing
showed the example material's ability to generate large wear scars
without exhibiting brittle-type micro-fractures (e.g. spalling or
chipping), leading to a longer tool life.
[0114] Thus, examples of a PCD material may be formed having that a
combination of high abrasion and fracture performance.
[0115] The microstructure of the PCD constructions formed according
to one or more of the above described example methods may be
determined using conventional image analysis techniques such as
scanning electron micrographs (SEM) taken using a backscattered
electron signal.
[0116] The homogeneity or uniformity of the PCD structure may be
quantified by conducting a statistical evaluation using a large
number of micrographs of polished sections. The distribution of the
filler phase, which is easily distinguishable from that of the
diamond phase using electron microscopy, can then be measured in a
method similar to that disclosed in EP 0 974 566 (see also
WO2007/110770). This method allows a statistical evaluation of the
average thicknesses of the binder phase along several arbitrarily
drawn lines through the microstructure. This binder thickness
measurement is also referred to as the "mean free path" by those
skilled in the art.
[0117] While various versions have been described with reference to
a number of examples, those skilled in the art will understand that
various changes may be made and equivalents may be substituted for
elements thereof and that these examples are not intended to limit
the particular examples or versions disclosed.
[0118] For example, in some embodiments of the method, the PCD
material may be sintered for a period in the range from about 1
minute to about 30 minutes, in the range from about 2 minutes to
about 15 minutes, or in the range from about 2 minutes to about 10
minutes.
[0119] In some examples of the method, the sintering temperature
may be in the range from about 1,200 degrees centigrade to about
2,300 degrees centigrade, in the range from about 1,400 degrees
centigrade to about 2,000 degrees centigrade, in the range from
about 1,450 degrees centigrade to about 1,700 degrees centigrade,
or in the range from about 1,450 degrees centigrade to about 1,650
degrees centigrade.
[0120] In one example, the method may include removing residual
metallic catalyst/binder material for diamond from interstices
between the diamond grains of the PCD material. In some examples,
the PCD structure may have a region adjacent a surface comprising
at most about 2 volume percent of catalyst material for diamond. In
further examples, the PCD structure may additionally have a region
remote from the surface comprising greater than about 2 volume
percent of catalyst material for diamond. In some such examples,
the region adjacent the surface may extend to a depth of at least
about 20 microns, at least about 80 microns, at least about 100
microns or even at least about 400 microns from the surface, or
greater.
* * * * *