U.S. patent application number 15/103293 was filed with the patent office on 2016-10-20 for super hard constructions & methods of making same.
The applicant listed for this patent is ELEMENT SIX ABRASIVES S.A.. Invention is credited to DAVID CHRISTIAN BOWES.
Application Number | 20160303709 15/103293 |
Document ID | / |
Family ID | 50031072 |
Filed Date | 2016-10-20 |
United States Patent
Application |
20160303709 |
Kind Code |
A1 |
BOWES; DAVID CHRISTIAN |
October 20, 2016 |
SUPER HARD CONSTRUCTIONS & METHODS OF MAKING SAME
Abstract
A super hard construction (1) comprises a substrate (30) and a
super hard material layer (32) formed over the substrate. One of
the interface surface (38) of the substrate or the interface
surface of the super hard material layer comprises a plurality of
spaced-apart projections (44, 46); the projections (44) being
arranged in an annular discontinuous first array around the central
longitudinal axis and spaced from the peripheral surface (40) of
the substrate by a distance of between around 1 mm to around 1.5 mm
A second annular discontinuous array of projections (46) is
positioned radially within the first array. The projections in the
second array are positioned to radially align with spaces between
the projections in the first array, the interface surface between
the projections being substantially planar; and the projections in
the first array are of a greater height than the projections in the
second array.
Inventors: |
BOWES; DAVID CHRISTIAN;
(DIDCOT, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ELEMENT SIX ABRASIVES S.A. |
Luxembourg |
|
LU |
|
|
Family ID: |
50031072 |
Appl. No.: |
15/103293 |
Filed: |
December 17, 2014 |
PCT Filed: |
December 17, 2014 |
PCT NO: |
PCT/EP2014/078284 |
371 Date: |
June 9, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B24D 3/06 20130101; E21B
10/5735 20130101; B24D 3/007 20130101 |
International
Class: |
B24D 3/00 20060101
B24D003/00; B24D 3/06 20060101 B24D003/06; E21B 10/573 20060101
E21B010/573 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 2013 |
GB |
1322340.9 |
Claims
1. A super hard construction comprising: a substrate comprising a
peripheral surface, an interface surface and a longitudinal axis;
and a super hard material layer formed over the substrate and
having an exposed outer surface, a peripheral surface extending
therefrom and an interface surface; wherein one of the interface
surface of the substrate or the interface surface of the super hard
material layer comprises: a plurality of spaced-apart projections
arranged to project from the interface surface; the projections
being arranged in a substantially annular discontinuous first array
around the central longitudinal axis and spaced from the peripheral
surface of the substrate by a distance of between around 1 mm to
around 1.5 mm and a second substantially annular discontinuous
array of projections radially within the first array; the
projections in the second array being positioned to radially align
with spaces between the projections in the first array; the
interface surface between the projections being substantially
planar; and wherein the projections in the first array are of a
greater height than the projections in the second array.
2. The super hard construction of claim 1, wherein the first and
second arrays are substantially concentric with the substrate.
3. The super hard construction of claim 1, wherein the first array
comprises substantially the same number of projections as the
second array.
4. The super hard construction of claim 1, wherein the projections
in the first and second arrays are staggered relative to each
other.
5. The super hard construction of claim 1, wherein one or more of
the surfaces of all or a majority of the projections extend in one
or more planes which are not substantially parallel to the plane of
the exposed outer surface of the super hard material layer and/or
in one or more planes which are not substantially parallel to a
plane through which the central longitudinal axis of the substrate
extends.
6. The super hard construction of claim 1, wherein the thickness of
the super hard material layer about the central longitudinal axis
of the substrate is substantially the same as the thickness of the
super hard material layer at the peripheral surface.
7. The super hard construction of claim 1, wherein the super hard
material layer comprises polycrystalline diamond.
8. The super hard construction of claim 1, wherein the exposed
outer surface of the super hard layer is substantially planar.
9. The super hard construction of claim 1, wherein the interface
surface of the substrate is a negative or reversal of the interface
surface of the super hard material layer such that the two
interface surfaces form a matching fit.
10. The super hard construction of claim 1, wherein the super hard
construction is a cutter element.
11. The super hard construction of claim 1, wherein the projections
are arranged such that there is reflective symmetry along a plane
though the central axis.
12. An earth boring drill bit comprising a body having the super
hard construction of claim 1 mounted thereon as a cutter
element.
13. A method of forming the super hard construction of claim 1.
14. (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 for use as cutter
inserts or elements for drill bits for boring into the earth.
BACKGROUND
[0002] Polycrystalline super hard materials, such as
polycrystalline diamond (PCD) and polycrystalline cubic boron
nitride (PCBN) 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 spalling 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),
polycrystalline cubic boron nitride (PCBN) 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 superabrasive 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 often
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 or PCBN,
diamond particles or grains or CBN 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
or CBN grains occurs, forming a polycrystalline super hard diamond
or polycrystalline CBN 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] Cobalt has a significantly different coefficient of thermal
expansion from that of diamond and, as such, upon heating of the
polycrystalline diamond material during use, the cobalt in the
substrate to which the PCD material is attached expands and may
cause cracks to form in the PCD material, resulting in the
deterioration of the PCD layer.
[0009] To reduce the residual stresses created at the interface
between the substrate and the super hard layer, interface surfaces
on substrates are known to have been formed with a plurality
concentric annular rings projecting from the planar interface
surface. Due to the difference in the coefficients of thermal
expansion of the substrate and the super hard material layer, these
layers contract at different rates when the cutting element is
cooled after HTHP sintering. Tensile stress regions are formed on
the upper surfaces of the rings, whereas compressive stress regions
are formed on/in the valleys between such rings. Consequently, when
a crack begins to grow in use, it may grow annularly along the
entire upper surface of the annular ring where it is exposed to
tensile stresses, or may grow along the entire annular valley
between the projecting rings where it is exposed to compressive
stresses, leading to the early failure of the cutting element.
[0010] It is also known for cutting element substrate interfaces to
comprise a plurality of spaced apart projections, the projections
having relatively flat upper surfaces projecting from a planar
interface surface.
[0011] Common problems that affect cutting elements are chipping,
spalling, partial fracturing, and cracking of the super hard
material layer. Another problem is cracking along the interface
between the super hard material layer and the substrate and the
propagation of the crack across the interface surface. These
problems may result in the early failure of the super hard material
layer and thus in a shorter operating life for the cutting element.
Accordingly, there is a need for a cutting element having an
enhanced operating life in high wear or high impact applications,
such as boring into rock, with a super hard material layer in which
the likelihood of cracking, chipping, and fracturing is reduced or
controllable.
SUMMARY
[0012] Viewed from a first aspect there is provided a super hard
construction comprising: [0013] a substrate comprising a peripheral
surface, an interface surface and a longitudinal axis; and [0014] a
super hard material layer formed over the substrate and having an
exposed outer surface, a peripheral surface extending therefrom and
an interface surface; [0015] wherein one of the interface surface
of the substrate or the interface surface of the super hard
material layer comprises: [0016] a plurality of spaced-apart
projections arranged to project from the interface surface; the
projections being arranged in a substantially annular discontinuous
first array around the central longitudinal axis and spaced from
the peripheral surface of the substrate by a distance of between
around 1 mm to around 1.5 mm and a second substantially annular
discontinuous array of projections radially within the first array;
[0017] the projections in the second array being positioned to
radially align with spaces between the projections in the first
array; [0018] the interface surface between the projections being
substantially planar; and [0019] wherein the projections in the
first array are of a greater height than the projections in the
second array.
[0020] Viewed from a second aspect there is provided an earth
boring drill bit comprising a body having the aforementioned super
hard construction mounted thereon as a cutter element.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Non-limiting embodiments will now be described by way of
example and with reference to the accompanying drawings in
which:
[0022] FIG. 1 is a schematic perspective view from above of an
embodiment of a cutting element showing the substrate features in
phantom;
[0023] FIG. 2a is a perspective view of a substrate of the cutting
element of FIG. 1;
[0024] FIG. 2b is a schematic plan view of the substrate of the
substrate of FIG. 2a; and
[0025] FIG. 2c is a schematic cross-sectional view of the substrate
along the axis A-A shown in FIG. 2b.
DETAILED DESCRIPTION
[0026] In the embodiments described herein, when projections or
depressions are described as being formed on the substrate surface,
it should be understood that they could be formed instead on the
surface of the super hard material layer that interfaces with the
substrate interface surface, with the inverse features formed on
the substrate. Additionally, it should be understood that a
negative or reversal of the interface surface is formed on the
super hard material layer interfacing with the substrate such that
the two interfaces form a matching fit.
[0027] 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.
[0028] As used herein, a "super hard construction" means a
construction comprising a body of polycrystalline super hard
material and a substrate attached thereto.
[0029] As used herein, polycrystalline diamond (PCD) is a type of
polycrystalline super hard material (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. In one embodiment
of PCD material, interstices between the diamond grains may be at
least partly filled with a binder material comprising a catalyst
for diamond. As used herein, "interstices" or "interstitial
regions" are regions between the diamond grains of PCD material. In
embodiments 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.
[0030] As used herein, PCBN (polycrystalline cubic boron nitride)
material refers to a type of super hard material comprising grains
of cubic boron nitride (cBN) dispersed within a matrix comprising
metal or ceramic. PCBN is an example of a super hard material.
[0031] A "catalyst material" for a super hard material is capable
of promoting the growth or sintering of the super hard
material.
[0032] 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. Additionally, as used herein, the terms "radial"
and "circumferential" and like terms are not meant to limit the
feature being described to a perfect circle.
[0033] The super hard construction 1 shown in the attached figures
may be suitable, for example, for use as a cutter insert for a
drill bit for boring into the earth.
[0034] Like reference numbers are used to identify like features in
all drawings.
[0035] In an embodiment as shown in FIG. 1, a cutting element 1
includes a substrate 30 with a layer of super hard material 32
formed on the substrate 30. The substrate may be formed of a hard
material such as cemented tungsten carbide. The super hard material
may be, for example, polycrystalline diamond (PCD), polycrystalline
cubic boron nitride (PCBN), 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). The exposed
top surface of the super hard material opposite the substrate forms
the cutting face 34, which is the surface which, along with its
edge 36, performs the cutting in use.
[0036] At one end of the substrate 30 is an interface surface 38
that interfaces with the super hard material layer 32 which is
attached thereto at this interface surface. The substrate 30 is
generally cylindrical and has a peripheral surface 40 and a
peripheral top edge 41.
[0037] In the embodiment shown in FIGS. 1 and 2a, the interface
surface 38 includes a plurality of spaced-apart projections 44 that
are arranged in a substantially annular discontinuous first array
and are spaced from the peripheral edge 41 by a distance D, and a
second or inner substantially annular discontinuous array of
projections 46 that are radially within the first array 44. The
distance D ranges, for example from between around 1 mm to around
1.5 mm.
[0038] As shown in FIGS. 2a to 2c, in this embodiment the
spaced-apart projections 44, 46 are arranged in two arrays which
are disposed in two substantially circular paths around a central
longitudinal axis of the substrate 30. Also, whilst the projections
46 of the inner array are shown to be closer to the outer array 44
than to the longitudinal central axis of the substrate, in other
embodiments the projections 46 of the inner array may be closer to
the longitudinal central axis.
[0039] The projections 46 in the second array may be positioned to
radially align with the spaces between the projections 44 in the
first array. The projections 44, 46 and spaces may be staggered,
with projections in one array overlapping spaces in the next array.
This staggered or mis-aligned distribution of three-dimensional
features on the interface surface may assist in distributing
compressive and tensile stresses and/or reducing the magnitude of
the stress fields and/or arresting crack growth by preventing an
uninterrupted path for crack growth.
[0040] As shown in FIGS. 2a to 2c, in these embodiments, the
interface surface between the projections 44, 46 is, for example,
substantially planar and all or a majority of the projections 44,
46 are shaped such that all or a majority of the surfaces of the
projections are not substantially parallel to the cutting face 34
of the super hard material 32 or to the plane through which the
longitudinal axis of the substrate extends.
[0041] The projections 44, 46 may have a smoothly curving upper
surface or may have a sloping upper surface. In some embodiments,
the projections 44, 46 may be slightly trapezoidal or tapered in
shape, being widest nearer the interface surface from which they
project.
[0042] It is believed that such a configuration acts to disturb
`elastic` wave formation in the material and deflect cracks at the
interface.
[0043] In FIGS. 2a to 2c, the projections 44, 46 are spaced
substantially equally in/round the respective substantially annular
array, with each projection 44, 46 within a given array having the
same dimension. However, the projections 44, 46 may be formed in
any desired shape, as described above, and spaced apart from each
other in a uniform or non-uniform manner to alter the stress fields
over the interface surface 38 to form substantially annular
concentric discontinuous rings. The projections 44 in the outer
array are, as shown in the embodiment of FIGS. 2a to 2c, larger in
size than those in the inner array.
[0044] In the embodiment shown in FIGS. 1 and 2a to 2c, the outer
array includes the same number of projections 44 as the inner
array, for example three projections. This permits the cutter
element 1 to have pseudo axi-symmetry thereby providing freedom in
positioning the cutter in the tool or drill bit in which it is to
be used as it would not require specific orientation, and in this
embodiment, there is reflective symmetry along a plane though the
central axis. The projections 44, 46 are positioned and shaped in
such a way that they inhibit one or more continuous paths along
which cracks could propagate across the interface surface 38.
[0045] The arrangement and shape of the projections 44, 46 and
spaces therebetween may affect the stress distributions in the
cutting element 1 and may act to improve the cutting element's
resistance to crack growth, in particular crack growth along the
interface surface 38, for example by arresting or diverting crack
growth across the stress zones in, around and above the projections
44, 46.
[0046] As shown in the embodiment of FIG. 1, the depth of super
hard material in the region around the central longitudinal axis of
the substrate 30 may be substantially the same depth as the depth
of the super hard material at the periphery of the super hard
material layer 32. This may enable the volume and area of super
hard material exposed to the work surface in use not to decrease
significantly with wear progression thereby improving the lifespan
of the cutter element 1. It may also assist in stiffening the
cutter element 1 when loaded in the axial direction. Furthermore,
it may assist in decreasing or substantially eliminating the
possibility of grooving wear formation during use.
[0047] In one or more of the above-described embodiments, the
projections 44, 46 of the interface surfaces 38 may be formed
integrally whilst the substrate is being formed through use of an
appropriately shaped mold into which the particles of material to
form the substrate are placed. Alternatively, the projections 44,
46 of the interface surface 38 may be created after the substrate
has been created or part way through the creation process, for
example by a conventional machining process such as EDM or by laser
ablation. Similar procedures may be applied to the super hard
material layer 32 to create the corresponding shaped interface
surface for forming a matching fit with that of the substrate, or
such a matching fit may be created in the interface of the super
hard material layer by placing the particles of super hard material
onto a pre-formed substrate and subjecting the combination to the
sintering process such that the matching interface in the super
hard material layer is formed during sintering.
[0048] The super hard material layer 32 may be attached to the
substrate by, for example, conventional brazing techniques or by
sintering using a conventional high pressure and high temperature
technique.
[0049] The durability of the cutter product including the substrate
and super hard material layer with the aforementioned interface
features and/or the mitigation of elastic stress waves therein may
be further enhanced if the super hard material layer 32 is leached
of catalyst material, either partially or fully, in subsequent
processing, or subjected to a further high pressure high
temperature sintering process. The leaching may be performed whilst
the super hard material layer 32 is attached to the substrate or,
for example, by detaching the super hard material layer 32 from the
substrate, and leaching the detached super hard material layer 32.
In the latter case, after leaching has taken place, the super hard
material layer 32 may be reattached to the substrate using, for
example, brazing techniques or by resintering using a high pressure
and high temperature technique.
[0050] Although particular embodiments have been described and
illustrated, it is to be understood that various changes and
modifications may be made. For example, the substrate described
herein has been identified by way of example. It should be
understood that the super hard material may be attached to other
carbide substrates besides tungsten carbide substrates, such as
substrates made of carbides of W, Ti, Mo, Nb, V, Hf, Ta, and Cr.
Furthermore, although the embodiments shown in FIGS. 1 to 2c are
depicted in these drawings as comprising PCD structures having
sharp edges and corners, embodiments may comprise PCD structures
having rounded, bevelled or chamfered edges or corners. Such
embodiments may reduce internal stress and consequently extend
working life through improving the resistance to cracking,
chipping, and fracturing of cutting elements through the interface
of the substrate or the super hard material layer having unique
geometries.
* * * * *