U.S. patent application number 12/397597 was filed with the patent office on 2009-07-16 for methods of making cemented carbide inserts for earth-boring bits.
This patent application is currently assigned to TDY Industries, Inc.. Invention is credited to Prakash K. Mirchandani, Alfred J. Mosco.
Application Number | 20090180915 12/397597 |
Document ID | / |
Family ID | 36572346 |
Filed Date | 2009-07-16 |
United States Patent
Application |
20090180915 |
Kind Code |
A1 |
Mirchandani; Prakash K. ; et
al. |
July 16, 2009 |
METHODS OF MAKING CEMENTED CARBIDE INSERTS FOR EARTH-BORING
BITS
Abstract
This invention relates to cuffing inserts for earth boring bits
comprising a cutting zone, wherein the cutting zone comprises first
cemented hard particles and a body zone, wherein the body zone
comprises second cemented hard particles. The first cemented hard
particles may differ in at least one property from the second
cemented hard particles. As used herein, the term cemented hard
particles means a material comprising hard particles in a binder.
The hard particles may be at least one of a carbide, a nitride, a
boride, a silicide, an oxide, and solid solutions thereof and the
binder may be at least one metal selected from cobalt, nickel, iron
and alloys of cobalt, nickel or iron.
Inventors: |
Mirchandani; Prakash K.;
(Houston, TX) ; Mosco; Alfred J.; (Spring,
TX) |
Correspondence
Address: |
ALLEGHENY TECHNOLOGIES INCORPORATED
1000 SIX PPG PLACE
PITTSBURGH
PA
15222-5479
US
|
Assignee: |
TDY Industries, Inc.
Pittsburgh
PA
|
Family ID: |
36572346 |
Appl. No.: |
12/397597 |
Filed: |
March 4, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11013842 |
Dec 16, 2004 |
7513320 |
|
|
12397597 |
|
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Current U.S.
Class: |
419/8 ;
264/113 |
Current CPC
Class: |
B22F 2005/001 20130101;
E21B 10/52 20130101; B22F 7/06 20130101; B22F 2998/00 20130101;
B22F 2998/00 20130101; C22C 29/005 20130101; C22C 29/067
20130101 |
Class at
Publication: |
419/8 ;
264/113 |
International
Class: |
B22F 7/02 20060101
B22F007/02 |
Claims
1-10. (canceled)
11. A method of preparing a cutting insert for an earth-boring bit,
the method comprising: partially filling a mold with a first
cemented hard particle powder; filling at least a portion of the
remaining portion of the mold with a second cemented hard particle
powder; consolidating the first and second cemented hard particle
powders into a single green compact; and sintering the single green
compact.
12. The method of claim 11, wherein sintering the single green
compact is performed at a temperature between 1300.degree. C. and
1500.degree. C.
13. The method of claim 11, wherein at least one of the first
cemented hard particle powder and the second cemented hard particle
powder is a cemented carbide powder.
14. The method of claim 11, wherein at least one of the first
cemented hard particle powder and the second cemented hard particle
powder comprises a recycled cemented carbide powder.
15. The method of claim 13, wherein the cemented carbide powder
comprises: a carbide of at least one transition metal selected from
titanium, chromium, vanadium, zirconium, hafnium, tantalum,
molybdenum, niobium, and tungsten; and a binder comprising cobalt,
a cobalt alloy, nickel, a nickel alloy, iron, and an iron
alloy.
16. The method of claim 15, wherein the binder further comprises an
alloying agent selected from tungsten, titanium, tantalum, niobium,
chromium, molybdenum, boron, carbon, silicon, and ruthenium.
17. The method of claim 13, wherein the cemented carbide powder
comprises a hybrid cemented carbide powder, the hybrid cemented
carbide powder comprising a plurality of first cemented carbide
grade particles and a plurality of second cemented carbide grade
particles.
18. The method of claim 11, wherein sintering the single green
compact provides a sintered compact comprising a first region of a
first cemented hard particle material autogenously bonded to a
second region of a second cemented hard particle material.
19. The method of claim 13, wherein: sintering the single green
compact provides a sintered compact comprising a first region of a
first cemented hard particle material autogenously bonded to a
second region of a second cemented hard particle material; and
wherein at least one of the first cemented hard particle material
and the second cemented hard particle material is a cemented
carbide including a carbide of at least one transition metal
selected from titanium, chromium, vanadium, zirconium, hafnium,
tantalum, molybdenum, niobium, and tungsten, and a binder
comprising cobalt, a cobalt alloy, nickel, a nickel alloy, iron,
and an iron alloy.
20. The method of claim 17, wherein sintering the single green
compact provides a sintered compact comprising a first region of a
first cemented hard particle material autogenously bonded to a
second region of a second cemented hard particle material, and
wherein at least one of the first cemented hard particle material
and the second cemented hard particle material is a hybrid cemented
carbide.
21. A method of preparing a cutting insert for an earth-boring bit,
the method comprising: consolidating a first cemented carbide
powder in a mold to provide a first green compact; placing the
first green compact in a second mold, wherein the first green
compact fills a portion of the second mold; filling at least a
portion of a remaining portion of the second mold with a second
cemented carbide powder; consolidating the second cemented carbide
powder and the first green compact together to form a second
compact; and sintering the second compact.
22. The method of claim 21, wherein at least one of the first
cemented carbide powder and the second cemented carbide powder
comprises a recycled cemented carbide powder.
23. The method of claim 21, further comprising, prior to placing
the first green compact in the second mold, presintering the first
green compact at a temperature up to 1250.degree. C.
24. The method of claim 21, wherein sintering the second compact
comprises heating the second compact at a temperature between
1300.degree. C. and 1500.degree. C.
25. The method of claim 21, wherein the first cemented carbide
powder and the second cemented carbide powder independently
comprise: a carbide of at least one transition metal selected from
titanium, chromium, vanadium, zirconium, hafnium, tantalum,
molybdenum, niobium, and tungsten; and a binder comprising cobalt,
a cobalt alloy, nickel, a nickel alloy, iron, and an iron
alloy.
26. The method of claim 25, wherein the binder further comprises an
alloying agent selected from tungsten, titanium, tantalum, niobium,
chromium, molybdenum, boron, carbon, silicon, and ruthenium.
27. The method of claim 21, wherein at least one of the first
cemented carbide powder and the second cemented carbide powder
comprises a hybrid cemented carbide powder, the hybrid cemented
carbide powder comprising a plurality of first cemented carbide
grade particles and a plurality of second cemented carbide grade
particles.
28. The method of claim 21, wherein sintering the second compact
provides a sintered compact comprising a first region of a first
cemented carbide autogenously bonded to a second region of a second
cemented carbide.
29. The method of claim 25, wherein sintering the second compact
provides a sintered compact comprising a first region of a first
cemented carbide autogenously bonded to a second region of a second
cemented carbide, and wherein the first cemented carbide and the
second cemented carbide individually comprise: a carbide of at
least one transition metal selected from titanium, chromium,
vanadium, zirconium, hafnium, tantalum, molybdenum, niobium, and
tungsten; and a binder comprising cobalt, a cobalt alloy, nickel, a
nickel alloy, iron, and an iron alloy.
30. The method of claim 27, wherein sintering the second compact
provides a sintered compact comprising a first region of a first
cemented carbide autogenously bonded to a second region of a second
cemented carbide, and wherein at least one of the first cemented
carbide and the second cemented carbide is a hybrid cemented
carbide.
31. A method of preparing a cutting insert for an earth-boring bit,
comprising: pressing a first cemented carbide powder and a second
cemented carbide in a mold to form a green compact, wherein at
least one of the first cemented carbide and the second cemented
carbide powder comprise a recycled cemented carbide powder; and
sintering the green compact.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This non-provisional application is a divisional application
of co-pending U.S. patent application Ser. No. 11/013,842, entitled
CEMENTED CARBIDE INSERTS FOR EARTH-BORING BITS, which was filed on
Dec. 16, 2004.
FIELD OF TECHNOLOGY
[0002] This invention relates to improvements to cutting inserts
and cutting elements for earth-boring bits and methods of producing
cutting inserts for earth-boring bits. More specifically, the
invention relates to cemented hard particle cutting inserts for
earth-boring bits comprising at least two regions of cemented hard
particles and methods of making such cutting inserts.
BACKGROUND OF THE INVENTION
[0003] Earth-boring (or drilling) bits are commonly employed for
oil and natural gas exploration, mining and excavation. Such
earth-boring bits may have fixed or rotatable cutting elements.
FIG. 1 illustrates a typical rotary cone earth-boring bit 10 with
rotatable cutting elements 11. Cutting inserts 12, typically made
from a cemented carbide, are placed in pockets fabricated on the
outer surface of the cutting elements 11. Several cutting inserts
12 may be fixed to the rotatable cutting elements 11 in
predetermined positions to optimize cutting.
[0004] The service life of an earth-boring bit is primarily a
function of the wear properties of the cemented carbide inserts.
One way to increase earth-boring bit service life is to employ
cutting inserts made of materials with improved combinations of
strength, toughness, and abrasion/erosion resistance.
[0005] As stated above, the cutting inserts may be made from
cemented carbides, a type of cemented hard particle. The choice of
cemented carbides for this application is predicated on the fact
that these materials offer very attractive combinations of
strength, fracture toughness, and wear resistance (i.e., properties
that are extremely important to the efficient functioning of the
boring or drilling bit). Cemented carbides are metal-matrix
composites comprising carbides of one or more of the transition
metals belonging to groups IVB, VB, and VIB of the periodic table
(Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W) as the hard particles or
dispersed phase, and cobalt, nickel, or iron (or alloys of these
metals) as the binder or continuous phase. Among the different
possible hard particle-binder combinations, cemented carbides based
on tungsten carbide (WC) as the hard particle, and cobalt as the
binder phase, are the ones most commonly employed for earth-boring
applications.
[0006] The properties of cemented carbides depend upon, among other
properties, two microstructural parameters, namely, the average
hard particle grain size and the weight or volume fraction of the
hard particles or binder. In general, the hardness and wear
resistance increases as the grain size decreases and/or the binder
content decreases. On the other hand, fracture toughness increases
as the grain size increases and/or the binder content increases.
Thus there is a trade-off between wear resistance and fracture
toughness when selecting a cemented carbide grade for any
application. As wear resistance increases, fracture toughness
typically decreases and vice versa.
[0007] FIGS. 2A-2E illustrate some of the different shapes and
designs of the cemented carbide inserts typically employed in
rotary cone earth-boring bits. Cutting inserts for earth-boring
bits are typically characterized by the shape of the domed portion
22A-22E, such as, ovoid 22A (FIG. 2A), ballistic 22B (FIG. 2B),
chisel 22C (FIG. 2C), multidome 22D (FIG. 2D), and conical 22E
(FIG. 2E). The choice of the shape and cemented carbide grade
employed depends upon the type of rock being drilled. Regardless of
shape or size, all inserts have a dome portion, such as, 22A-22E
and a body portion 21. The cutting action is performed by the dome
portion 22A-22E, while the body portion 21 provides support for the
dome portion 22A-22E. Most, or all, of the body portion 21 is
embedded within the bit body or cutting element, and the body
portion is typically inserted into the bit body by press fitting
the cutting insert into a pocket.
[0008] As previously stated, the cutting action is primarily
provided by the dome portion. The first portion of the dome portion
to begin wearing away is the top half of the dome portion, and, in
particular, the extreme tip of the dome portion. As the top of the
dome portion begins to flatten out, the efficiency of cutting
decreases dramatically since the earth is being removed by more of
a rubbing action, as opposed to the more efficient cuffing action.
As rubbing action continues, considerable heat may be generated by
the increase in friction, thereby resulting in the insert failing
by thermal cracking and subsequent breakage. In order to retard
wear at the tip of the dome, the drill bit designer has the choice
of selecting a more wear resistant grade of cemented carbide from
which to fabricate the inserts. However, as discussed earlier, the
wear resistance of cemented carbides is inversely proportional to
their fracture toughness. Hence, the drill bit designer is
invariably forced to compromise between failure occurring by wear
of the dome and failure occurring by breakage of the cutting
insert. In addition, the cost of inserts used for earth-boring
applications is relatively high since only virgin grades of
cemented hard particles are employed for fabricating cutting
inserts for earth-boring bits.
[0009] Accordingly, there is a need for improved cutting inserts
for earth-boring bits having increased wear resistance, strength
and toughness. Further, there is a need for lower cost cutting
inserts.
SUMMARY OF PRESENT INVENTION
[0010] Embodiments of the cutting inserts for earth-boring bits of
the present invention comprise at least two zones having different
properties, such as hardness and fracture toughness. Embodiments of
the present invention include earth-boring cutting inserts
comprising at least a cutting zone, wherein the cutting zone
comprises first cemented hard particles, and a body zone, wherein
the body zone comprises second cemented hard particles. In a
particular embodiment, the cutting zone may occupy a portion of the
dome region while the body zone occupies the remainder of the dome
region as well as all or part of the body region.
[0011] The first cemented hard particles differ in at least one
property from the second cemented hard particles. As used herein,
cemented hard particles means a material comprising a discontinuous
phase of hard particles in a binder. The hard particles are
"cemented" together by the binder. An example of cemented hard
particles is a cemented carbide. The hard particles may be at least
one of a carbide, a nitride, a boride, a silicide, an oxide, and
solid solutions thereof and the binder may be at least one metal
selected from cobalt, nickel, iron, and alloys of cobalt, nickel,
or iron.
[0012] Further embodiments of the cutting insert for an
earth-boring drill bit comprise a cutting zone and a body zone,
wherein the at least one of the cutting zone and the body zone
comprises a hybrid cemented carbide. In one embodiment, the cutting
zone comprises a hybrid cemented carbide and the body zone
comprises a conventional cemented carbide. Generally, a hybrid
cemented carbide comprises a discontinuous phase of a first
cemented carbide grade dispersed throughout a continuous phase of a
second cemented carbide continuous phase.
[0013] The present invention is also directed to a method of
preparing a cutting insert for an earth-boring bit. One embodiment
of the method of the present invention comprises partially filling
the mold with a first cemented hard particle powder, followed by
filling the remaining volume of the mold with a second cemented
hard particle powder, and then consolidating the two cemented hard
particle powders as a single green compact. Another embodiment of
the method of the present invention comprises consolidating a first
cemented hard particle powder in a mold, thereby forming a first
green compact and placing the first green compact in second mold,
wherein the first green compact fills a portion of the second mold.
The remaining portion of the second mold may then be filled with a
second cemented hard particle powder and the second hard particle
powder and the green compact may be further consolidated together
to form a second green compact. The second green compact may then
be sintered.
[0014] A further embodiment of the method of the present invention
includes preparing a cutting insert for an earth-boring bit
comprising pressing a first cemented carbide powder and a second
cemented carbide powder in a mold to form a green compact, wherein
at least one of the first cemented carbide powder and the second
cemented carbide powder comprise a recycled cemented carbide
powder, and sintering the green compact.
[0015] Unless otherwise indicated, all numbers expressing
quantities of ingredients, time, temperatures, and so forth used in
the present specification and claims are to be understood as being
modified in all instances by the term "about." Accordingly, unless
indicated to the contrary, the numerical parameters set forth in
the following specification and claims are approximations that may
vary depending upon the desired properties sought to be obtained by
the present invention. At the very least, and not as an attempt to
limit the application of the doctrine of equivalents to the scope
of the claims, each numerical parameter should at least be
construed in light of the number of reported significant digits and
by applying ordinary rounding techniques.
[0016] Notwithstanding that the numerical ranges and parameters
setting forth the broad scope of the invention are approximations,
the numerical values set forth in the specific examples are
reported as precisely as possible. Any numerical value, however,
may inherently contain certain errors necessarily resulting from
the standard deviation found in their respective testing
measurements.
[0017] The reader will appreciate the foregoing details and
advantages of the present invention, as well as others, upon
consideration of the following detailed description of embodiments
of the invention. The reader also may comprehend such additional
details and advantages of the present invention upon making and/or
using embodiments within the present invention.
BRIEF DESCRIPTION OF THE FIGURES
[0018] The features and advantages of the present invention may be
better understood by reference to the accompanying figures in
which:
[0019] FIG. 1 illustrates a typical rotary cone earth-boring drill
bit;
[0020] FIGS. 2a-2e illustrate different shapes and sizes of cutting
inserts typically employed in rotary cone earth-boring bits such as
ovoid (FIG. 2a), ballistic (FIG. 2b), chisel (FIG. 2c), multidome
(FIG. 2d), and conical (FIG. 2e);
[0021] FIGS. 3a-3e illustrate an embodiment of a cutting insert 30
of the present invention as described in Example 1 wherein FIG. 3a
is a photograph of a cross section of the cutting insert comprising
a cutting zone 31 and a body zone 32; FIG. 3b is a photomicrograph
of the cutting zone 31 of the cutting insert; FIG. 3c is a
photomicrograph of a transition zone between the cutting zone 31
and the body zone 32 of the cutting insert; FIG. 3d is a
photomicrograph of the body zone 32 of the cutting insert; FIG. 3e
illustrates the exterior of the embodiment of a cutting insert for
an earth-boring bit of the present invention comprising a cutting
zone and a body zone;
[0022] FIGS. 4a-4e illustrate an embodiment of a cutting insert 40
of the present invention as described in Example 2 wherein FIG. 4a
is a photograph of a cross section of the cutting insert comprising
a cutting zone 41 and a body zone 42; FIG. 4b is a photomicrograph
of the cutting zone 41 of the cutting insert; FIG. 4c is a
photomicrograph of a transition zone between the cutting zone 41
and the body zone 42 of the cutting insert; FIG. 4d is a
photomicrograph of the body zone 42 of the cutting insert; FIG. 4e
illustrates the exterior of the embodiment of a cutting insert for
an earth-boring bit of the present invention comprising a cutting
zone and a body zone;
[0023] FIGS. 5a-5e illustrate an embodiment of a cutting insert 50
of the present invention as described in Example 3 wherein FIG. 5a
is a photograph of a cross section of the cutting insert comprising
a cutting zone 51 and a body zone 52; FIG. 5b is a photomicrograph
of the cutting zone 51 of the cutting insert comprising a hybrid
cemented carbide; FIG. 5c is a photomicrograph of a transition zone
between the cutting zone 51 and the body zone 52 of the cutting
insert; FIG. 5d is a photomicrograph of the body zone 52 of the
cutting insert; FIG. 5e illustrates the exterior of the embodiment
of a cutting insert for an earth-boring bit of the present
invention comprising a cutting zone and a body zone;
[0024] FIGS. 6a-6e illustrate an embodiment of a cutting insert 60
of the present invention as described in Example 4 wherein FIG. 6a
is a photograph of a cross section of the cutting insert comprising
a cutting zone 61 and a body zone 62; FIG. 6b is a photomicrograph
of the cutting zone 61 of the cutting insert; FIG. 6c is a
photomicrograph of a transition zone between the cutting zone 61
and the body zone 62 of the cutting insert; FIG. 6d is a
photomicrograph of the body zone 62 of the cutting insert; FIG. 6e
illustrates the exterior of the embodiment of a cutting insert for
an earth-boring bit of the present invention comprising a cutting
zone and a body zone; and
[0025] FIG. 7 is a schematic representation of the cutting insert
70 of the present invention comprising a cutting zone 71 of virgin
cemented carbide and a body zone 72 comprising a recycled cemented
carbide grade.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0026] Embodiments of the present invention provide cutting inserts
for earth-boring drill bits. Further embodiments of the cutting
inserts of the present invention comprise at least two zones
comprising cemented hard particles having different properties,
such as, for example, wear resistance, hardness, fracture
toughness, cost, and/or availability. The two zones may be for
example, a cutting zone and a body zone. In such an embodiment, the
cutting zone may comprise at least a portion of the dome region
while the body zone may comprise at least a portion of the body
region and may further comprise a portion of the dome region.
Embodiments of the invention include various shapes and sizes of
the multiple zones. For example, the cutting zone may be a portion
of the dome regions having the shapes shown in FIGS. 2A-2E, which
are ovoid (FIG. 2A), ballistic (FIG. 2B), chisel (FIG. 2C),
multidome (FIG. 2D), and conical (FIG. 2E). Additional zones within
the cutting inserts of the present invention may include central
axis support zones, bottom zones, transitional zones or other zones
that may enhance the properties of the cutting inserts for
earth-boring drill bits. The various zones may be designed to
provide, for example, improved wear characteristics, toughness, or
self-sharpening characteristics to the cutting insert.
[0027] Embodiments of the earth-boring cutting inserts of the
present invention comprise a cutting zone, wherein the cutting zone
comprises first cemented hard particles and a body zone, wherein
the body zone comprises second cemented hard particles. For
example, FIGS. 3a-3e illustrate an embodiment of a cutting insert
30 of the present invention as prepared in Example 1. A cross
section of the cutting insert 30 shows a cutting zone 31 and a body
zone 32. FIG. 3b is a photomicrograph of the cutting zone 31 of the
cutting insert comprising a first cemented carbide and FIG. 3d is a
photomicrograph of the body zone 32 of the cutting insert
comprising a second cemented carbide. The hard particles (i.e. the
discontinuous phase) of the cemented hard particles may be selected
from at least one of a carbide, a nitride, a boride, a silicide, an
oxide, and solid solutions thereof.
[0028] FIGS. 4a-4e illustrate a further embodiment of a cutting
insert 40 of the present invention as prepared in Example 2. The
embodiment of FIGS. 4a-4e comprises different cemented carbides
than the embodiment of FIGS. 3a-3e. FIG. 3a is a cross section of
the cutting insert 40 showing a cutting zone 41 and a body zone 42.
FIG. 4b is a photomicrograph of the cutting zone 41 of the cutting
insert comprising a first cemented carbide. FIG. 4d is a
photomicrograph of the body zone 32 of the cutting insert
comprising a second cemented carbide.
[0029] In embodiments wherein the cemented hard particles in the
two or more zones of the cutting insert are different cemented
carbides, the cemented carbide materials in the cutting zone and/or
body zone may include carbides of one or more elements belonging to
groups IVB through VIB of the periodic table. Preferably, the
cemented carbides comprise at least one transition metal carbide
selected from titanium carbide, chromium carbide, vanadium carbide,
zirconium carbide, hafnium carbide, tantalum carbide, molybdenum
carbide, niobium carbide, and tungsten carbide. The carbide
particles preferably comprises about 60 to about 98 weight percent
of the total weight of the cemented carbide material in each
region. The carbide particles are embedded within a matrix of a
binder that preferably constitutes about 2 to about 40 weight
percent of the total weight of the cemented carbide within each
zone in each zone.
[0030] The binder of the cemented hard particles may comprise at
least one of cobalt, nickel, iron, or alloys of these elements. The
binder also may comprise, for example, elements such as tungsten,
chromium, titanium, tantalum, vanadium, molybdenum, niobium,
zirconium, hafnium, and carbon up to the solubility limits of these
elements in the binder. Additionally, the binder may contain up to
5 weight percent of elements such as copper, manganese, silver,
aluminum, and ruthenium. One skilled in the art will recognize that
any or all of the constituents of the cemented hard particle
material may be introduced in elemental form, as compounds, and/or
as master alloys. Preferably, the cutting zone and the body zone
independently comprise different cemented carbides comprising
tungsten carbide in a cobalt binder. The different cemented hard
particles have at least one property that is different than at
least one other cemented hard particle in the cutting insert for
the drilling bit.
[0031] Embodiments of the cutting insert may also include hybrid
cemented carbides, such as, but not limited to, any of the hybrid
cemented carbides described in copending U.S. patent application
Ser. No. 10/735,379, which is hereby incorporated by reference in
its entirety. Generally, a hybrid cemented carbide is a material
comprising particles of at least one cemented carbide grade
dispersed throughout a second cemented carbide continuous phase,
thereby forming a composite of cemented carbides. The hybrid
cemented carbides of U.S. patent application Ser. No. 10/735,379
have low contiguity ratios and improved properties relative to
other hybrid cemented carbides. Preferably, the contiguity ratio of
the dispersed phase of a hybrid cemented carbide may be less than
or equal to 0.48. Also, a hybrid cemented carbide composite of the
present invention preferably has a dispersed phase with a hardness
greater than the hardness of the continuous phase. For example, in
certain embodiments of the hybrid cemented carbides used in one or
more zones of cutting inserts of the present invention, the
hardness of the dispersed phase is preferably greater than or equal
to 88 HRA and less than or equal to 95 HRA, and the hardness of the
continuous phase is greater than or equal to 78 and less than or
equal to 91 HRA.
[0032] Additional embodiments or the cutting insert according to
the present invention may include hybrid cemented carbide
composites comprising a first cemented carbide dispersed phase
wherein the volume fraction of the dispersed phase is less than 50
volume percent and a second cemented carbide continuous phase,
wherein the contiguity ratio of the dispersed phase is less than or
equal to 1.5 times the volume fraction of the dispersed phase in
the composite material.
[0033] FIG. 5 shows an embodiment of a cutting insert of the
present invention comprising a cutting zone 51 made of a hybrid
cemented carbide. The cemented carbides of the hybrid cemented
carbide of the cutting zone comprise tungsten carbide in cobalt.
The dispersed phase of a hybrid cemented carbide comprises a first
cemented carbide grade and continuous phase of a second cemented
carbide. The first cemented carbide comprises 35 weight percent of
the total hybrid cemented carbide in the cutting zone 51. The first
cemented carbide grade has a cobalt content of 10 weight percent,
an average grain size of 0.8 .mu.m, and a hardness of 92.0 HRA. The
second cemented carbide grade of the hybrid cemented carbide
comprises the remaining 65 weight percent of the cutting zone 51
and is a cemented carbide grade having a cobalt content of 10
weight percent, an average WC grain size of 3.0 .mu.m, and a
hardness of 89.0 HRA.
[0034] FIGS. 5a-5e illustrate an embodiment of a cutting insert 50
of the present invention as described in Example 3 wherein FIG. 5a
is a photograph of a cross section of the cutting insert comprising
a cutting zone 51 and a body zone 52; FIG. 5b is a photomicrograph
of the cutting zone 51 of the cutting insert comprising a hybrid
cemented carbide; FIG. 5c is a photomicrograph of a transition zone
between the cutting zone 51 and the body zone 52 of the cutting
insert; FIG. 5d is a photomicrograph of the body zone 52 of the
cutting insert; FIG. 5e illustrates the exterior of the embodiment
of a cutting insert for an earth-boring bit of the present
invention comprising a cutting zone and a body zone.
[0035] The body zone 52 of the cutting insert 50 of FIG. 5(a)
comprises a cemented carbide grade having a cobalt content of 10
weight percent and an average WC grain size of 3.0 .mu.m. The
resultant body zone 62 has a hardness of 89.0 HRA.
[0036] This invention relates to cutting inserts having novel
microstructures that allow for tailoring the wear resistance and
toughness levels at different zones of regions of the insert. In
this manner it is possible to provide improved combinations of wear
resistance and toughness compared to "monolithic" inserts (i.e.,
inserts made from a single grade of cemented carbide, and thus
having the same properties at all locations within the insert).
This invention also relates to inserts made from combinations of
cemented carbide grades to achieve cost reductions. This invention
relates not only to the design of the inserts, but also to the
manufacturing processes employed to fabricate the inserts.
[0037] In the preferred embodiments of this invention, a cutting
zone of the cutting insert has a hardness (or wear resistance) that
is greater than that of a body zone. It will be understood,
however, that any combination of properties may be engineered into
embodiments of the present invention by selection of zones and
suitable materials in the zones.
[0038] The manufacturing process for articles of cemented hard
particles typically comprises blending or mixing a powdered metal
comprising the hard particles and a powdered metal comprising the
binder to form a metallurgical powder blend. The metallurgical
powder blend may be consolidated or pressed to form a green
compact. See Example 4. The green compact is then sintered to form
the article or a portion of the article having a solid monolithic
construction. As used herein, an article or a region of an article
has a monolithic construction if it is composed of a material, such
as, for example, a cemented carbide material, having substantially
the same characteristics at any working volume within the article
or region. Subsequent to sintering, the article may be
appropriately machined to form the desired shape or other features
of the particular geometry of the article.
[0039] For example, the metallurgical powder blend may be
consolidated by mechanically or isostatically compressing to form
the green compact. The green compact is subsequently sintered to
further densify the compact and to form an autogenous bond between
the regions or portions of the article. Preferably, the compact is
over pressure sintered at a pressure of 300-2000 psi and at a
temperature of 1350-1500.degree. C.
[0040] Embodiments of the present invention include methods of
producing the cutting inserts for drilling bits or earth-boring
bits. One such method includes placing a first metallurgical powder
into a first region of a void of a mold. A second metallurgical
powder blend may be placed into a second region of the void of the
mold. Depending on the number of regions of different cemented hard
particle or cemented carbide materials desired in the cutting
insert, the mold may be partitioned into additional regions in
which additional metallurgical powder blends may be disposed. For
example, the mold may be segregated into regions by placing one or
more physical partitions in the void of the mold to define the
several regions, or by merely filling the portions of the mold
without providing a partition. The metallurgical powders are chosen
to achieve the desired properties of the corresponding regions of
the cutting as described above. The powders with the mold are then
mechanically or isostatically compressed at the same time to
densify the metallurgical powders together to form a green compact
of consolidated powders. The method of preparing a sintered compact
provides a cutting insert that may be of any shape and have any
other physical geometric features. Such advantageous shapes and
features may be understood to those of ordinary skill in the art
after considering the present invention as described herein.
[0041] A further embodiment of the method of the present invention
comprises consolidating a first cemented carbide powder in a mold
forming a first green compact and placing the first green compact
in second mold, wherein the first green compact fills a portion of
the second mold. The second mold may be at least partially filled
with a second cemented carbide powder. The second cemented carbide
powder and the first green compact may be consolidated to form a
second green compact. Finally, the second green compact is
sintered. For example, the cutting insert 60 of FIG. 6 comprises a
cutting zone 61 and a body zone 62. The cutting zone 61 was
prepared by consolidating a first cemented carbide into a green
compact. The green compact was then surrounded by a second cemented
carbide powder to form the body zone 62. The first green compact
and the second cemented carbide powder were consolidated together
to form a second green compact. The resulting second green compact
may then be sintered to further densify the compact and to form an
autogenous bond between the body zone 62 and the cutting zone 61,
and, if present, other cemented carbide regions. If necessary, the
first green compact may be presintered up to a temperature of about
1200.degree. C. to provide strength to the first green compact.
[0042] Such embodiments of the method of the present invention
provide the cutting insert designer increased flexibility in design
of the different zones for particular applications. The first green
compact may be designed in any desired shape from any desired
cemented hard particle material. In addition, the process may be
repeated as many times as desired, preferably prior to sintering.
For example, after consolidating to form the second green compact,
the second green compact may be placed in a third mold with a third
powder and consolidated to form a third green compact. By such a
repetitive process, more complex shapes may be formed, cutting
inserts including multiple clearly defined regions of differing
properties may be formed, and the cutting insert designer will be
able to design cutting inserts with specific wear capabilities in
specific zones or regions.
[0043] One skilled in the art would understand the process
parameters required for consolidation and sintering to form
cemented hard particle articles, such as cemented carbide cutting
inserts. Such parameters may be used in the methods of the present
invention, for example, sintering may be performed at a temperature
suitable to densify the article, such as at temperatures up to
1500.degree. C.
[0044] As stated above, the cutting action of earth-boring bits is
primarily provided by the dome area. The first region of the dome
to begin wearing away is typically the top half of the dome, and,
in particular, the extreme tip of the dome. As the top of the dome
begins to flatten out, the efficiency of cutting decreases
dramatically since the earth is being removed by a rubbing action
as opposed to a cutting action. The cost of inserts used for
earth-boring applications is relatively high since only virgin
powder grades are employed for fabricating inserts. Considering
that less than 25% of the volume of the inserts (i.e., the dome) is
actually involved in the cutting action, the present inventors
recognize that there is clearly an opportunity for significant cost
reduction if the body zone could be made from a cheaper powder
grade (using recycled materials, for example), as long as there is
no reduction in strength in the zone separating the dome and the
body zone.
[0045] The service life of an earth-boring bit can be significantly
enhanced if the wear of the top half of the dome can be retarded
without compromising the toughness (or breakage resistance) of the
cutting inserts. Furthermore, significant cost reductions can be
achieved if the inserts could be fabricated using and recycled
materials. Such an embodiment of a cutting insert is shown in FIG.
7. The cutting insert 70 includes a cutting zone 71 manufactured
from a virgin cemented carbide and a body zone 72 manufactured from
recycled cemented carbide. In this embodiment, the cutting zone 71
comprises all of the dome of the cutting insert 80 and a portion of
the cylindrical body zone. One skilled in the art would understand
that the cutting zone may comprise any desired percentage of the
volume of the entire cutting insert and is not limited to the
percentage, shape, or design shown in FIG. 7.
[0046] Embodiments of the cutting inserts for drilling bits of the
present invention may comprise at least one zone comprising
recycled cemented carbides. For example, tungsten and other
valuable constituents of certain cemented carbides may be recovered
by treating most forms of tungsten containing scrap and waste. In
addition, embodiments of the present invention include methods of
preparing a cutting insert for an earth-boring bit, comprising
pressing a first cemented carbide powder and a second cemented
carbide in a mold to form a green compact, wherein at least one of
the first cemented carbide and the second cemented carbide comprise
a recycled cemented carbide, and sintering the green compact.
[0047] Worn but clean cemented carbide articles comprising
particles of transition metal carbides in a binder, such as worn or
broken cutting inserts and compacts, may be recycled to produce a
transition metal powder. Cemented carbide scrap may be recycled by
a variety of processes including direct conversion, binder
leaching, and chemical conversion. Direct conversion into graded
powder ready for pressing and resintering is typically only
performed with sorted hard metal scrap. The zinc process, a direct
conversion process well known in the art, comprises treating the
clean cemented carbide articles with molten zinc typically at a
temperature between 900.degree. C. and 1000.degree. C. The molten
zinc dissolves the binder phase. Both the zinc and binder are
subsequently distilled under vacuum from the hard metal at a
temperature between 900.degree. C. and 1000.degree. C., leaving a
spongy hard metal material. The spongy material may be easily
crushed, ballmilled, and screened to form the recycled transition
metal powder.
[0048] The coldstream process is another direct conversion recycle
process. The coldstream process typically comprises accelerating
cleaned and sorted hardmetal scrap, such as cemented carbides, in
an airjet. The hardmetal scrap is crushed through impact with a
baffle plate. The crushed hard metal is classified by screens,
cyclones, and/or filters to produce the graded hardmetal powder
ready for use. For brittle hardmetals with low binder content,
direct mechanical crushing is also an alternative direct conversion
method of recycling.
[0049] Leaching processes are designed to chemically remove the
binder from between the metal carbide particles while leaving the
metal carbide particles intact. The quality and composition of the
starting material used in the leaching process determines the
quality of the resulting recycled carbide material.
[0050] Contaminated scrap may be treated in a chemical conversion
process to recover of the cemented carbide constituents as powders.
A typical chemical conversion process includes oxidation of the
scrap at a temperature in the range of 750.degree. C. to
900.degree. C. in air or oxygen. The oxidized scrap is the
subjected to a pressure digestion process with sodium hydroxide
(NaOH) at 200.degree. C. and 20 bar for 2 to 4 hours. The resulting
mixture is filtered and, subsequently, precipitation and extraction
steps are performed to purify the metal carbide. Finally,
conventional carbide processing steps are performed, such as,
calcination, reduction, and carburization, to produce the metal
carbide powder for use in producing recycle cemented carbide
articles. The recycled transition metal powder may be used in the
manufacturing process for the production of any of the articles of
the present invention.
EXAMPLE 1
[0051] FIG. 3(a) shows an embodiment of a cutting insert 30 of the
present invention having a cutting zone 31 comprising a cemented
carbide grade having a Co content of 10 weight percent and an
average WC grain size of 0.8 .mu.m. The cutting zone 31 has a
hardness of 92.0 HRA. The second zone, the body zone 32, comprises
a cemented carbide grade having a Co content of 10 weight percent
and an average WC grain size of 3.0 .mu.m. The body zone 32 has a
hardness of 89.0 HRA. FIGS. 3(b)-3(d) illustrate the
microstructures of the cutting zone (FIG. 3(b)), the transition
zone between the cutting zone 31 and the body zone 32 (FIG. 3(c)),
and the body zone 32(FIG. 3(d)), respectively. FIG. 3(e)
illustrates the exterior of the insert.
[0052] The insert of example 1 was fabricated by filling a portion
of the dome of the lower punch with the first cemented carbide
powder corresponding to the cutting zone, followed by raising the
die table and filling the mold with powder grade corresponding to
the body zone 32. The entire powder volume was pressed and liquid
phase sintered as a single piece.
EXAMPLE 2
[0053] FIG. 4(a) shows an embodiment of a cutting insert 41 of the
present invention having a cutting zone 41 comprising a cemented
grade having a Co content of 6 weight percent and an average WC
grain size of 1.5 .mu.m. The resultant cutting zone 41 has a
hardness of 92.0 HRA. The body zone 42 comprises a cemented carbide
grade having a Co content of 10 weight percent and an average WC
grain size of 3.0 .mu.m. The body zone has a hardness of 89.0 HRA.
FIGS. 4(b)-4(d) illustrate the microstructures of the cutting zone
41 (FIG. 4(b)), the transition zone between the cutting zone 41 and
the body zone 42 (FIG. 4(c)), and the body zone 42 respectively.
FIG. 4(e) illustrates the exterior of the insert.
[0054] The fabrication method employed for the inserts of example 2
was similar to the one employed for example 1.
EXAMPLE 3
[0055] FIG. 5(a) shows an embodiment of an insert 50 having a
cutting zone 51 based on a hybrid cemented carbide grade consisting
of a mixture of two cemented carbide grades. The discontinuous
phase with the cutting zone 51 is a first grade comprises 35 weight
percent of the cutting zone 51, and is a cemented carbide grade
having a Co content of 10 weight percent, an average grain size of
0.8 .mu.m, and a hardness of 92.0 HRA. The continuous phase second
grade of the hybrid cemented carbide comprises the remaining 65
weight percent of the cutting zone 51 and is a cemented carbide
grade having a Co content of 10 weight percent, an average WC grain
size of 3.0 .mu.m, and a hardness of 89.0 HRA.
[0056] The body zone 52 of the cutting insert 50 of FIG. 5(a)
comprises a cemented carbide grade having a Co content of 10 weight
percent and an average WC grain size of 3.0 .mu.m. The resultant
body zone 52 has a hardness of 89.0 HRA. FIGS. 5(b)-5(d) illustrate
the microstructures of the cutting zone (FIG. 5(b)), the transition
zone between the cutting zone 51 and the body zone 52 (FIG. 5(c)),
and the body zone (FIG. 5(d)) respectively. FIG. 5(e) illustrates
the exterior of the insert.
[0057] The fabrication method employed for the inserts of example 3
was similar to the one employed for example 1 with the exception of
using a hybrid cemented carbide in the cutting zone 51.
EXAMPLE 4
[0058] FIG. 6(a) shows an embodiment of an insert 60 of the present
invention having a cutting zone 61 based on a grade having a Co
content of 6 weight percent and an average WC grain size of 1.5
.mu.m. The cutting zone 61 has a hardness of 92.0 HRA. The body
zone 62 is based on a cemented carbide grade having a Co content of
10 weight percent and an average WC grain size of 3.0 gm. The body
zone 62 has a hardness of 89.0 HRA. FIGS. 6(b)-6(d) illustrate the
microstructures of the cutting zone 61 (FIG. 6(b)), the transition
zone between the cutting zone 61 and the body zone 62 (FIG. 6(c)),
and the body zone 62 (FIG. 6(d)) respectively. FIG. 6(e)
illustrates the exterior of the insert 60.
[0059] The fabrication method employed for example 4 consisted of
pressing a green compact from the cemented carbide grade of the
cutting zone, placing the pre-pressed green compact on the lower
punch, raising the die table and filling the mold with the cemented
carbide powder grade corresponding to the body zone, followed by
pressing the powder and sintering as one piece.
EXAMPLE 5
[0060] The cutting insert 70 of example 5 was made with a cutting
zone 71 comprising a cemented carbide grade having a Co content of
10 weight percent and an average WC grain size of 5.0 .mu.m. The
grade of the cutting zone 71 was prepared using virgin raw
materials. The cutting zone has a hardness of 87.5 HRA. The body
zone 72 comprises a cemented grade having a Co content of 11 weight
percent and an average WC grain size of 4.5 .mu.m. The cemented
carbide grade of the body zone 72 was prepared using recycled raw
materials and is considerably lower in cost compared with the
cemented carbide grade used in the cutting zone. The resultant body
zone has a hardness of 88.0 HRA. FIG. 7 schematically illustrates
the configuration of the insert of example 5. Either of the
fabrication methods used for examples 1 through 4 may be used for
fabricating the inserts of example 5.
[0061] It is to be understood that the present description
illustrates those aspects of the invention relevant to a clear
understanding of the invention. Certain aspects of the invention
that would be apparent to those of ordinary skill in the art and
that, therefore, would not facilitate a better understanding of the
invention have not been presented in order to simplify the present
description. Although embodiments of the present invention have
been described, one of ordinary skill in the art will, upon
considering the foregoing description, recognize that many
modifications and variations of the invention may be employed. All
such variations and modifications of the invention are intended to
be covered by the foregoing description and the following
claims.
* * * * *