U.S. patent application number 12/038309 was filed with the patent office on 2008-06-19 for multi-edge working surfaces for polycrystalline diamond cutting elements.
This patent application is currently assigned to ReedHycalog UK, Ltd.. Invention is credited to Andrew Bell, Nigel Dennis Griffin, Peter Raymond Hughes.
Application Number | 20080142267 12/038309 |
Document ID | / |
Family ID | 33485109 |
Filed Date | 2008-06-19 |
United States Patent
Application |
20080142267 |
Kind Code |
A1 |
Griffin; Nigel Dennis ; et
al. |
June 19, 2008 |
Multi-Edge Working Surfaces for Polycrystalline Diamond Cutting
Elements
Abstract
A polycrystalline diamond cutting element for earth boring drill
bits presents at least three regions of different abrasion
resistance to the earthen formation when in operation. The cutting
element has an end working surface and the regions, which are
substantially free of catalyzing material, form a series of at
least three layers. In operation, these layers wear at different
rates causing a series of protruding lips. The end working surface
may be substantially planar or frusto-conical in form.
Inventors: |
Griffin; Nigel Dennis;
(Nympsfield, GB) ; Hughes; Peter Raymond; (Stroud,
GB) ; Bell; Andrew; (Eastington, GB) |
Correspondence
Address: |
JEFFREY E. DALY;GRANT PRIDECO, L.P.
400 N. SAM HOUSTON PARKWAY EAST, SUITE 900
HOUSTON
TX
77060
US
|
Assignee: |
ReedHycalog UK, Ltd.
|
Family ID: |
33485109 |
Appl. No.: |
12/038309 |
Filed: |
February 27, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11163323 |
Oct 14, 2005 |
|
|
|
12038309 |
|
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Current U.S.
Class: |
175/57 ;
175/434 |
Current CPC
Class: |
E21B 10/567
20130101 |
Class at
Publication: |
175/57 ;
175/434 |
International
Class: |
E21B 10/52 20060101
E21B010/52 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 23, 2004 |
GB |
0423597.4 |
Claims
1. A cutting element for an earth boring drill bit comprising a
facing table of a polycrystalline diamond material integrally
bonded to a tungsten carbide substrate, the facing table comprising
a generally planar, generally circular end working surface, and a
generally cylindrical peripheral working surface, the
polycrystalline diamond material comprising layers of differing
diamond constituency, arranged one adjacent the other to form a
multiple of discreet layers; wherein in operation an outermost,
first layer is exposed at the end working surface and a least a
plurality of the other layers are exposed at the cylindrical
peripheral working surface such that at least three of the discreet
layers of the polycrystalline diamond material are exposed, and
wherein adjacent layers have different abrasion resistances.
2. The cutting element of claim 1 wherein the diamond material in
the outermost, first layer is treated to remove a catalyzing
material from the polycrystalline diamond material, forming a new
layer on the working surface that is substantially free of the
catalyzing material.
3. The cutting element of claim 1 wherein at least two of the
layers have different thicknesses
4. The cutting element of claim 2 wherein a plurality of the layers
have differing volume densities.
5. The cutting element of claim 4 wherein, in operation, at least
three protruding lips form along the generally cylindrical
peripheral working surface.
6. The cutting element of claim 5, wherein the peripheral working
surface is substantially perpendicular to the end working
surface.
7. The cutting element of claim 2 wherein at least two of the
layers are comprised of diamond crystals of differing particle
size.
8. The cutting element of claim 7 wherein, in operation, at least
three protruding lips form along the generally cylindrical
peripheral working surface.
9. The cutting element of claim 8, wherein the peripheral working
surface is substantially perpendicular to the end working
surface.
10. The cutting element of claim 9 wherein the layers contain
encapsulated diamond material which has been pre-synthesized.
11. The cutting element of claim 9 wherein a portion of the diamond
material is made with powdery carbonates.
12. The cutting element of claim 6 wherein, in operation, the
protruding lips form on a worn portion of the end working
surfaces.
13. A method of using a cutting element comprising: forming a
continuous table of polycrystalline diamond material having at
least three different layers, each layer having a different diamond
constituency, the diamond material bonded to a tungsten carbide
substrate comprising a facing table having a generally planar,
generally circular end working surface, and a generally cylindrical
peripheral working surface; treating at least part of each of the
end working surface and the peripheral working surface to remove
catalyzing material therefrom; exposing untreated superhard
material between the end and peripheral working surfaces, and
preferentially wearing the exposed, untreated polycrystalline
diamond material of the cutting element to expose at least three
protruding lips.
14. The method of claim 13, wherein the step of preferentially
wearing the exposed, untreated polycrystalline diamond material
comprises machining away the polycrystalline diamond material.
15. The method of claim 13, wherein the step of preferentially
wearing the exposed, untreated polycrystalline diamond material
comprises wearing away the polycrystalline diamond material during
a drilling operation.
16. A PDC cutting element for use in earth boring, comprising a
continuous facing table of a polycrystalline diamond material
integrally bonded to a tungsten carbide substrate, the facing table
comprising a generally planar, generally circular end working
surface, and a generally cylindrical peripheral working surface,
the polycrystalline diamond material remote from the working
surfaces comprising a first series of interstices containing a
catalyzing material and having a first wear resistance, the
polycrystalline diamond material adjacent the working surfaces
forming a region at the surface of the facing table comprising a
second series of interstices adjacent at least part of the end
working surface and at least part of the peripheral working
surface, the second series of interstices are substantially free of
the catalyzing material to a depth of between about 0.02 mm and
0.25 mm, whereby the region formed at the surface of the facing
table adjacent the working surfaces has a thickness from the
surface of between 0.02 mm and 0.25 mm and has at least three
different layers polycrystalline diamond material, each layer
having a different wear resistance, and all the layers having a
higher wear resistance than the polycrystalline diamond material
remote from the working surfaces.
17. The cutting element of claim 16, wherein the peripheral working
surface is substantially perpendicular to the end working
surface.
18. The cutting element of claim 16 wherein at least two of the
layers have different thicknesses.
19. The cutting element of claim 17 wherein a plurality of the
layers have differing volume densities.
20. The cutting element of claim 19 wherein, in operation, at least
three protruding lips form along the generally cylindrical
peripheral working surface.
21. The cutting element of claim 20, wherein the peripheral working
surface is substantially perpendicular to the end working
surface.
22. The cutting element of claim 17 wherein at least two of the
layers are comprised of diamond crystals of differing particle
size.
23. The cutting element of claim 22 wherein, in operation, at least
three protruding lips form along the generally cylindrical
peripheral working surface.
24. The cutting element of claim 23, wherein the peripheral working
surface is substantially perpendicular to the end working
surface.
25. The cutting element of claim 24 wherein the layers contain
encapsulated diamond material which has been pre-synthesized.
26. The cutting element of claim 24 wherein a portion of the
diamond material is made with powdery carbonates.
27. The cutting element of claim 23 wherein, in operation, the
protruding lips form on a worn portion of the end working surfaces.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This Application is a Division of pending U.S. patent
application Ser. No. 11/163,323 entitled "Dual-Edge Working
Surfaces for Polycrystalline Diamond Cutting Elements", filed on
Oct. 14, 2005, incorporated by reference herein for all it
contains, which claims priority from GB Provisional application
0423597.2, filed on Oct. 23, 2004.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to superhard polycrystalline material
elements for earth drilling, cutting, and other applications where
engineered superhard surfaces are needed. The invention
particularly relates to polycrystalline diamond and polycrystalline
diamond-like (collectively called PCD) elements with dual edged
working surfaces.
[0004] 2. Description of the Related Art
[0005] Polycrystalline diamond and polycrystalline diamond-like
elements are known, for the purposes of this specification, as PCD
elements. PCD elements are formed from carbon based materials with
exceptionally short inter-atomic distances between neighboring
atoms. One type of diamond-like material similar to PCD is known as
carbonitride (CN) described in U.S. Pat. No. 5,776,615. In general,
PCD elements are formed from a mix of materials processed under
high-temperature and high-pressure into a polycrystalline matrix of
inter-bonded superhard carbon based crystals. A common trait of PCD
elements is the use of catalyzing materials during their formation,
the residue from which, often imposes a limit upon the maximum
useful operating temperature of the element while in service.
[0006] A well known, manufactured form of PCD element is a
two-layer or multi-layer PCD element where a facing table of
polycrystalline diamond is integrally bonded to a substrate of less
hard material, such as tungsten carbide. The PCD element may be in
the form of a circular or part-circular tablet, or may be formed
into other shapes, suitable for applications such as hollow dies,
heat sinks, friction bearings, valve surfaces, indentors, tool
mandrels, etc. PCD elements of this type may be used in almost any
application where a hard wear and erosion resistant material is
required. The substrate of the PCD element may be brazed to a
carrier, often also of cemented tungsten carbide. This is a common
configuration for PCD's used as cutting elements, for example in
fixed cutter or rolling cutter earth boring bits when received in a
socket of the drill bit, or when fixed to a post in a machine tool
for machining.
[0007] PCD elements are most often formed by sintering diamond
powder with a suitable binder-catalyzing material in a
high-pressure, high-temperature press. One particular method of
forming this polycrystalline diamond is disclosed in U.S. Pat. No.
3,141,746 herein incorporated by reference for all it discloses. In
one common process for manufacturing PCD elements, diamond powder
is applied to the surface of a preformed tungsten carbide substrate
incorporating cobalt. The assembly is then subjected to very high
temperature and pressure in a press. During this process, cobalt
migrates from the substrate into the diamond layer and acts as a
binder-catalyzing material, causing the diamond particles to bond
to one another with diamond-to-diamond bonding, and also causing
the diamond layer to bond to the substrate.
[0008] The completed PCD element has at least one body with a
matrix of diamond crystals bonded to each other with many
interstices containing a binder-catalyzing material as described
above. The diamond crystals comprise a first continuous matrix of
diamond, and the interstices form a second continuous matrix of
interstices containing the binder-catalyzing material. In addition,
there are necessarily a relatively few areas where the
diamond-to-diamond growth has encapsulated some of the
binder-catalyzing material. These `islands` are not part of the
continuous interstitial matrix of binder-catalyzing material.
[0009] In one common form, the diamond body constitutes 85% to 95%
by volume and the binder-catalyzing material the other 5% to 15%.
Such an element may be subject to thermal degradation due to
differential thermal expansion between the interstitial cobalt
binder-catalyzing material and diamond matrix beginning at
temperatures of about 400 degrees C. Upon sufficient expansion the
diamond-to-diamond bonding may be ruptured and cracks and chips may
occur.
[0010] A common problem with these PCD elements, especially when
used in highly abrasive cutting application, such as in drill bits,
has been the limitation imposed between wear resistance and impact
strength. This relationship has been attributed to the fact that
the catalyzing material remaining in the interstitial regions among
the bonded diamond crystals contributes to the degradation of the
diamond layer.
[0011] It has become well known in the art to preferentially remove
this catalyzing material from a portion of the working surface in
order to form a surface with much higher abrasion resistance
without substantially reducing its impact strength. This new type
of PCD element is described in U.S. Pat. Nos. 6,601,662; 6,592,985
and 6,544,308 all these U.S. patents incorporated by reference
herein for all they disclose.
[0012] PCD elements made in accordance with these and in other
related patents have become widely used in the oilfield drilling
industry. One surprising observation resulting from this usage,
however, has been an increase in the cutting efficiency of these
cutters, which has been manifested in higher drilling rates of
penetration--typically by 40%, but occasionally by as much as a
factor of two to four times.
[0013] In observing these PCD cutting elements in the worn
condition, it was discovered that the differential wear rate caused
a protruding lip to form on the wear edge of the working surface.
This lip caused the PDC cutting element to appear `sharper` to the
earth formation being drilled, producing the higher drilling rates
of penetration.
[0014] U.S. Pat. No. 4,976,324 describes an arrangement in which a
vapour deposition technique is used to apply a catalyst free
diamond layer to a surface of a cutting element, but it will be
appreciated that the vapour deposition technique used does not bond
the diamond layer to the underlying diamond table. U.S. Pat. No.
6,068,913 and U.S. Pat. No. 4,766,040 both describe multi-layered
elements, and U.S. Pat. No. 6,187,068 describes providing the
element with concentric ring shaped regions of different abrasion
resistance.
[0015] An arrangement is described in U.S. Pat. No. 6,189,634 in
which, when worn, part of the substrate of a cutting element
becomes exposed at the working surface.
BRIEF SUMMARY OF THE INVENTION
[0016] The present invention is a PCD cutting element, which in
operation (and as it wears to a worn condition) presents at least
two cutting lips to the material being cut. One particularly
advantageous use of this new PDC cutting element is as cutting
elements for earth boring drill bits.
[0017] According to the present invention there is provided a
cutting element comprising a table of superhard material bonded to
a substrate of less hard material, the table of superhard material
defining a plurality of interstices containing a catalyzing
material, the table of superhard material defining an end working
surface and a peripheral working surface, wherein at least part of
the end working surface and at least part of the peripheral working
surface are substantially free of catalyzing material. The catalyst
free or substantially free parts may extend to a depth in the
region of about 0.02 to about 0.70 mm, preferably about 0.15 to
about 0.25 mm.
[0018] The element may have an edge of the part of the end working
surface which is substantially free of catalyzing material which
defines a first protruding lip, and an edge of the part of the
peripheral working surface which is substantially free of
catalyzing material defining a second protruding lip. The end
working surface may be substantially planar, and the peripheral
working surface may be substantially perpendicular thereto.
Alternatively, the peripheral working surface may be of
substantially frusto-conical form. The superhard material may be
polycrystalline diamond, and may incorporate regions of different
abrasion resistance, for example arranged in a series of layers, or
in a series of concentric rings. The table of superhard material
may incorporate encapsulated diamond material, for example made
using powdery carbonate. A region of superhard material containing
catalyzing material may be exposed between the parts of the
peripheral working surface and the end working surface which are
substantially free of catalyzing material. The first protruding lip
may be formed adjacent said region at an edge of the part of the
end working surface which is substantially free of catalyzing
material and the second protruding lip may be formed adjacent said
region at an edge of the part of the peripheral working surface
which is substantially free of catalyzing material. The said region
may be formed by machining away of material or be formed in use by
part of the cutting element wearing.
[0019] As a cutting element for an earth boring drill bit, one of
the protruding lips of the cutting element forms or is formed on a
first working surface presented from generally 10 degrees normally,
to up to 45 degrees backrake to an earthen formation as the bit is
operated to drill into the earth. The second lip forms or is formed
on a second working surface which adjoins the first working surface
and may be (but is not necessarily required to be) normal to the
first working surface. The PDC cutting element is oriented and
operated in a manner that presents both working surfaces to the
earthen formation as the drill bits progresses into the earth.
[0020] The invention also relates to a method of manufacturing a
cutting element comprising forming a table of superhard material
bonded to a less hard substrate, the table of superhard material
defining a plurality of interstices containing a catalyzing
material, the table defining an end working surface and a
peripheral working surface, and treating at least part of each of
the end working surface and the peripheral working surface to
remove the catalyzing material therefrom. A further step of
exposing untreated superhard material between the end and
peripheral working surfaces, may be incorporated. The step of
exposing may comprise machining away treated material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a perspective view of a PCD element of an
embodiment of the present invention in the form of a planar-face
cutting element.
[0022] FIG. 2 is a perspective view of a fixed cutter drill bit
suitable for using the PCD elements of the present invention.
[0023] FIG. 3 is a perspective view of a PCD element of the present
invention in the form of a domed-face cutting element.
[0024] FIG. 4 is a perspective view of a rolling cutter drill bit
suitable for using the PCD elements of the present invention.
[0025] FIG. 5 is a section view of a prior art PCD cutting
element.
[0026] FIG. 6 is a perspective view of a prior art planar face PCD
cutting element drilling into the earth.
[0027] FIG. 7 is a section view of a planar face PCD cutting
element of the present invention.
[0028] FIG. 8 is a section view of an alternative planar face PDC
cutting element of the present invention.
[0029] FIG. 9A is a top view of another embodiment of a planar face
PCD cutting element of the present invention.
[0030] FIG. 9B is a cross-section view through section X-X of the
planar face PCD cutting element of FIG. 9A.
[0031] FIG. 10 is a partial sectional view of one type of cutter of
the present invention, drilling into the earth.
[0032] FIG. 11 is a partial sectional view of a second geometry for
a cutter of the present invention, drilling into the earth.
[0033] FIG. 12 is a partial sectional view of the cutter of FIG. 7,
drilling into the earth.
[0034] FIG. 12A illustrates the cutter of FIG. 7 when worn.
[0035] FIG. 13 is a partial sectional view of the cutter of FIG. 8,
drilling into the earth.
[0036] FIG. 14 is a sectional view of the cutter of FIG. 7 in a
worn condition.
[0037] FIG. 15 is a sectional view of another embodiment of a
cutter of the present invention in a worn condition.
[0038] FIG. 16 is a sectional view of the cutter of FIGS. 9A and 9B
in a worn condition.
[0039] FIG. 17 is a diagrammatic view illustrating the structure of
part of a cutter.
DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED
EMBODIMENT
[0040] Referring now to FIGS. 1-4, the polycrystalline diamond and
polycrystalline diamond-like (PCD) element 1010 of the present
invention may be a preform cutting element 1010 for a fixed cutter
rotary drill bit 1012 (as shown in FIG. 1). The bit body 1014 of
the drill bit is formed with a plurality of blades 1016 extending
generally outwardly away from the central longitudinal axis of
rotation 1018 of the drill bit. Spaced apart side-by-side along the
leading face 1020 of each blade is a plurality of the PCD cutting
elements 1010 of the present invention.
[0041] Typically, the PCD cutting element 1010 has a body in the
form of a circular tablet having a thin front facing table 1022 of
diamond or diamond-like (PCD) superhard material, bonded in a
high-pressure high-temperature press to a substrate 1024 of less
hard material such as cemented tungsten carbide or other metallic
material. The cutting element 1010 is preformed and then typically
bonded on a generally cylindrical carrier 1026 which is also formed
from cemented tungsten carbide, or may alternatively be attached
directly to the blade. The PCD cutting element 1010 has peripheral
and end working surfaces 1028 and 1030 which, as illustrated, are
substantially perpendicular to one another.
[0042] The cylindrical carrier 1026 is received within a
correspondingly shaped socket or recess in the blade 1016. The
carrier 1026 will usually be brazed, shrink fit or press fit in the
socket. Where brazed, the braze joint may extend over the carrier
1026 and part of the substrate 1024. In operation the fixed cutter
drill bit 1012 is rotated and weight is applied. This forces the
cutting elements 1010 into the earth being drilled, effecting a
cutting and/or drilling action.
[0043] In a second embodiment, a shaped cutting element 1032 (as
shown in FIG. 3) of the present invention is provided on a rolling
cutter type drill bit 1034, shown in FIG. 4. A rolling cutter drill
bit 1034 typically has one or more truncated rolling cone cutters
1036, 1038, 1040 assembled on a bearing spindle on the leg 1042 of
the bit body 1044. The cutting elements 1032 may be mounted, for
example by press fitting as one or more of a plurality of cutting
inserts arranged in rows on rolling cutters 1036, 1038, 1040, or
alternatively the PCD cutting elements 1032 may be arranged along
the leg 1042 of the bit 1034. The PCD cutting element 1032 has a
body in the form of a facing table 1046 of diamond or diamond like
material bonded to a less hard substrate 1048. The facing table
1046 in this embodiment of the present invention is in the form of
a convex surface 1050 and has peripheral and end working surfaces
1052 and 1054. Accordingly, there are often a number of
transitional layers between the facing table 1046 and the substrate
1048 to help more evenly distribute the stresses generated during
fabrication, as is well known to those skilled in the art. The end
working surface 1052 is of domed or part-spherical form whilst the
peripheral working surface 1054 is of frusto-conical form.
[0044] In operation the rolling cutter drill bit 1032 is rotated
and weight is applied. This forces the cutting inserts 1032 in the
rows of the rolling cone cutters 1036, 1038, 1040 into the earth,
and as the bit 1036 is rotated the rolling cutters 1036, 1038, 1040
turn, effecting a drilling action.
[0045] As illustrated in FIG. 17, the structure of the table 1046
defines a series of interstices 1046a between the diamond crystals
1046b, the interstices 1046a containing binder catalyst material
1046c used during the synthesis of the table 1046.
[0046] The remaining discussion and description of the present
invention will be drawn, by way of example, to the planar face type
of cutting element 1010 shown in FIG. 1. It is understood, however,
that the same general principals and outcomes will apply as well to
the domed type cutting element 1032, as shown in FIG. 3.
[0047] A cross section view of a preform cutting element of the
prior art 1100 is shown in FIGS. 5 and 6 to illustrate and contrast
the present invention. The prior art cutting element 1100 shares
many elements in common with the PCD cutting element 1010, 1048,
1112, 1114, 1116, 1118, 1120 and 1122 of the present invention,
such as having a relatively thin front facing table 1022 of
diamond, bonded to a substrate 1024 of cemented tungsten carbide.
All the cutting elements 1010, 1048, 1112, 1114, 1116, 1118, 1120,
1122 and 1100 have working surfaces 1028 and 1030. A layer 1102 of
the facing table 1022 in many of these cutting elements is treated
in a manner such that the catalyzing material is substantially
removed from a relatively thin layer adjacent to the end working
surface 1030. Removal of the catalyzing material in this manner had
been found to greatly increase the wear resistance of the cutting
element, and to surprisingly increase its drilling rate.
[0048] Note, however, that the peripheral working surface 1028 on
the outside periphery 1104 on the prior art cutting element 1100
was not treated to remove the catalyzing material. The cutting
element 1100 is operated in a manner as illustrated in FIG. 6. This
is a typical representation in which the cutting element 1100 is
operated at a backrake angle 1106 of from typically 10 to 45
degrees. When operated in this manner, the treated layer 1102 of
the facing table 1022 is presented to the earth formation 1108.
[0049] In the present invention--as represented by FIGS. 7-16 a
plurality of protruding lips 1110 form as the cutter 1010, 1112,
1114, 1116, 1118, 1120 drills into the earth formation 1108. As a
cutting element for earth boring drill bits, one of the protruding
lips 1110 of the cutting element forms or is formed on a first
working surface 1030 presented from about 10 up to about 45 degrees
backrake to an earthen formation 1108 as the bit is operated to
drill into the earth 1108. The second lip 1110 forms or is formed
on a second working surface 1028 which adjoins the first working
surface 1030 and is generally, but not necessarily normal to the
first working surface 1030. The PDC cutting element is oriented and
operated in a manner that presents both working surfaces 1028, 1030
to the earthen formation 1108 as the drill bits 1012, 1034 progress
into the earth.
[0050] In the prior art cutter 1100, as shown in FIGS. 5 and 6, a
single lip 1109 would often form as the cutter 1100 began to wear
when drilling. The inventors believed that this lip 1109 formed
because the layer 1102 had higher abrasion resistance than the
other diamond material. What was not appreciated at the time of
that invention was that this lip tended to increase the drilling
rate of penetration by a factor of two and often more. The
mechanism behind this increase in rate of penetration is believed
to be the interaction of the lip 1109 with the earth formation 1108
during drilling. As drilling progresses, the underlying diamond
wears from beneath the lip 1109 causing ever further protrusion.
Once this protrusion reaches a critical amount the lip fractures.
This changes the cutting geometry of the cutter 1100 in a manner
that tends to make it self-sharpening--as when the lip fractures,
the lines of stress cause a cup-shaped or crescent-shaped portion
of the facing table to be lost. Until the lip re-forms, however,
the cutters 1100 will not be as sharp, and at least for a period of
time will not drill as efficiently. However, there are typically
many of these cutters 1100 on a drill bit 1012 so the average
drilling rate of penetration remains relatively stable. This is
overall a more efficient cutting shape than the flats that tend to
wear onto diamond tables of untreated cutters, however. As shown in
FIG. 5, the treated surface layer 1102 ended at the edge 1103 of
the prior art cutter 1100, and it is at this edge 1103 that the lip
1109 forms.
[0051] Although there are a nearly infinite number of possible
geometrical shapes for the cutters 1010, 1112, 1114, 1116, 1118,
1120 of the present invention, two preferred shapes are shown in
FIGS. 10 and 11. FIG. 10 shows a generally right circular
cylindrical shape cutter 1112 (similar to cutting element 1010 in
FIG. 1). The cutter 1112 is shown in partial section view mounted
on the face of a drill bit 1012 and drilling the formation 1108.
The cutter 1112 is shown orientated at a backrake 1106 from a line
parallel to the longitudinal axis 1018 of the drill bit 1012.
[0052] In FIG. 11, a second preferred shape for a cutter 1114, is
also shown orientated at a backrake 1106 from a line parallel to
the longitudinal axis 1018 of the drill bit 1012. Its cutting face
1122 is formed as a truncated cone, with the cone angle 1124
approximately equal to the backrake angle 1106. It may be
synthesized to this form, or may be machined to be of this form.
This cutter 1122 is also shown in partial section view mounted on
the face of a drill bit 1012 and drilling the formation 1108. The
advantages of this configuration will be explained later in this
specification.
[0053] FIGS. 7, 8, 9A, and 9B show three ways to form cutters which
produce the protruding lips 1110, and which may be used or adapted
for use in the formation of cutters having the configurations shown
in FIGS. 10 and 11.
[0054] In FIG. 7 a cutter 1116 of the preferred embodiment has a
layer 1030 which is treated in much the same manner as in the prior
art cutters 1100 shown in FIGS. 5 and 6. However, in the cutter
1116 of the present invention, the treatment is applied
additionally to the outside periphery 1124 of cutter 1116. As shown
in FIG. 12, the representation of this cutter 1116 after drilling
for a short period of time, as the cutter wears, two lips 1110
form. This configuration has been shown to increase the drilling
rate of penetration of the preferred embodiment cutter 1116 by as
much as 40% of the prior art cutter 1100--which is a total of
approximately a 50% to 60% improvement in rate of penetration of
cutters without the wear resistant layer shown of the cutter 1100
shown in FIGS. 5 and 6--but otherwise similar in shape and mode of
operation.
[0055] As mentioned hereinbefore, the treatment forms a relatively
thin layer 1102 which is free of or substantially free of
catalyzing material. The depth or thickness 1102a of the layer 1102
conveniently falls within the range of about 0.02 to about 0.70 mm,
preferably about 0.15 to about 0.25 mm.
[0056] It is believed that this improvement in rate of penetration
is due to a synergistic relationship between the plurality of lips
1110 that form as the cutter 1116 drills. As described above, as
the lips 1110 fracture, the lines of stress cause a cup-shaped or
crescent-shaped portion of the facing table to be lost. The
plurality of lips, however interact, in that when one of the lips
fractures, the cutting action may be transferred to another of the
lips. The likelihood of the cutter having at least one sharp edge
engaging the formation, at any given time is therefore improved,
thus maintaining the drilling rate of penetration lost by the prior
art cutters 1100 as shown in FIGS. 5 and 6, as while `new` lip
forms into a cutting edge after fracture the other lip is doing
most of the drilling. It will be appreciated that the lips of a
cutter may act on different parts of the formation being drilled,
and that whilst a new lip is forming, at least some of the material
which would have been cut by the fractured lip is instead cut by
part of a radially adjacent cutter.
[0057] In time, however, as shown in FIGS. 12A and 14, the cutter
1116 wears until only a small part of the working surface 1028 has
the lip 1110. The lifetime of this cutter 1116 is dependent,
therefore upon the how far down the outside periphery 1124 the
treatment extends, and the wear angle 1126 (shown in FIG. 14). It
is also dependent upon other factors including the rate of
penetration and the interaction of the cutter with radially
adjacent cutters. Wear angle 1126 is generally an angle
complimentary to the backrake 1106 of the cutter, but may also be
profoundly related to the type of formation drilled, the manner in
which the drill bit is operated, and the thickness of the wear
resistant layer.
[0058] Other ways of producing wear resistant layers which produce
lips 110 are disclosed in FIGS. 8, 9A, 9B, 15 and 16. In FIG. 8
shown is a cutter 1118 with multiple layers 1128, 1130, 1132 of
diamond material. These layers may be of differing thicknesses and
comprised of diamond crystals of differing particle size, and
volume density. In addition, these layers may contain encapsulated
diamond material which has been pre-synthesized. For example,
diamond material made with powdery carbonates or other means. The
diamond material in these multiple layers 1128, 1130, 1132 may be
further treated to removed the catalyzing material forming a
treated layer 1102 superimposed upon the discreet diamond layers
1128, 1130, 1132.
[0059] The arrangement of FIG. 15 includes a number of discrete
layers 1134, 1136, 1138, 1140, 1142, 1144, 1146, 1148, 1150 1152.
Under certain drill bit 1012 applications where the wear angle 1128
may be quite steep, it may be advantageous to have layers in this
manner. Again treated layer 1102 is provided.
[0060] Finally, concentric rings identified by the letters a, b,
and c, with base material d in FIGS. 9A and 9B may also effectively
provide a cutter 1120 with multiple lips. In this instance, as
indicated in FIG. 16, they may be negative--that is material a
produces a lip 1110 which stands apart from the base diamond
material d and ring b. This effectively forms double lips in
adjacent materials a and b, particularly if the wear angle 1130 is
quite high. A treated layer 1102 may, again, be provided.
[0061] Each of the configurations as disclosed in FIGS. 7, 8, 9A,
9B and 15 can apply equally as well to both the `standard` geometry
shown in FIG. 10 and the truncated cone geometry of FIG. 11. One
advantage of the geometry shown in FIG. 11, however, is that
minimal wear of the diamond surface is necessary for a plurality of
lips 1110 to form.
[0062] The invention encompasses, as well as the cutting element, a
method of manufacture thereof. The method comprises forming a table
of superhard material bonded to a substrate of a less hard
material. The table defines a plurality of interstices containing a
catalyzing material. End and peripheral working surfaces are
defined by the table. The method involves treating at least part of
the end working surface and at least part of the peripheral working
surface to remove the catalyzing material therefrom. The treatment
may comprise a leaching operation.
[0063] Whereas the present invention has been described in
particular relation to the drawings attached hereto, it should be
understood that other and further modifications apart from those
shown or suggested herein, may be made within the scope and spirit
of the present invention.
* * * * *