U.S. patent application number 13/906861 was filed with the patent office on 2013-12-05 for sintered superhard compact for cutting tool applications and method of its production.
The applicant listed for this patent is DIAMOND INNOVATIONS, INC.. Invention is credited to Torbjorn Selinder, Rui Shao, Gerold Weinl.
Application Number | 20130323107 13/906861 |
Document ID | / |
Family ID | 48670070 |
Filed Date | 2013-12-05 |
United States Patent
Application |
20130323107 |
Kind Code |
A1 |
Weinl; Gerold ; et
al. |
December 5, 2013 |
SINTERED SUPERHARD COMPACT FOR CUTTING TOOL APPLICATIONS AND METHOD
OF ITS PRODUCTION
Abstract
A method and composition of a sintered superhard compact is
provided. The sintered superhard compact body may comprise
superhard particles and a binder phase. The binder phase may bond
the superhard particles together. The binder phase comprises
tungsten and cobalt. The ratio of tungsten to cobalt is between 1
and 2 and sum of W and Co in the sintered superhard compact is in a
range of from about 2 to about 20 percent by weight.
Inventors: |
Weinl; Gerold; (Alvsjo,
SE) ; Selinder; Torbjorn; (Westerville, OH) ;
Shao; Rui; (Dublin, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DIAMOND INNOVATIONS, INC. |
Worthington |
OH |
US |
|
|
Family ID: |
48670070 |
Appl. No.: |
13/906861 |
Filed: |
May 31, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61653779 |
May 31, 2012 |
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Current U.S.
Class: |
419/10 ; 419/62;
75/228; 75/232; 75/236; 75/243; 75/244 |
Current CPC
Class: |
C04B 2235/3813 20130101;
C22C 26/00 20130101; B22F 3/12 20130101; C22C 2026/007 20130101;
C22C 2026/008 20130101; C22C 29/04 20130101; C22C 1/05 20130101;
C22C 29/005 20130101; C04B 2235/3804 20130101; B22F 3/02 20130101;
C04B 2235/386 20130101; C04B 35/58014 20130101; C04B 35/58021
20130101; C04B 35/5831 20130101; C22C 2026/006 20130101; C22C 29/16
20130101 |
Class at
Publication: |
419/10 ; 75/228;
75/243; 75/244; 75/232; 75/236; 419/62 |
International
Class: |
C22C 1/05 20060101
C22C001/05; B22F 3/12 20060101 B22F003/12; B22F 3/02 20060101
B22F003/02 |
Claims
1. A sintered superhard compact body, comprising: superhard
particles; and a binder phase bonding the superhard particles
together, wherein the binder phase comprises W and Co, wherein the
weight % ratio of W/Co in the sintered superhard compact falls
between 1.0 and 2.0, and sum of weight % W and Co in the sintered
superhard compact is in a range of from about 2.0 to about 20.
2. The sintered superhard compact body of claim 1, wherein the
superhard particles are selected from a group of cubic boron
nitride, diamond, and diamond composite materials.
3. The sintered superhard compact body of claim 1, further
comprises stoichiometric carbides, nitrides, oxides, or sums
thereof from aluminum, titanium or other metals in transition group
IV, V, and VI in Periodic Table of elements.
4. The sintered superhard compact body of claim 1, further
comprises substoichiometric carbides, nitrides, oxides, or sums
thereof from aluminum, titanium or other metals in transition group
IV, V, and VI in Periodic Table of elements.
5. The sintered superhard compact body of claim 1, wherein a ratio
of tungsten to cobalt is in a range of from 1.0 to 1.8.
6. The sintered superhard compact body of claim 1, wherein a ratio
of tungsten to cobalt is in a range of from 1.0 to 1.5.
7. The sintered superhard compact body of claim 1, further
comprising at least one boron containing tungsten, cobalt, or
tungsten-cobalt phases as detected by X-Ray diffraction (XRD).
8. The sintered superhard compact body of claim 1, further
comprising at least one phase selected from a group of WB.sub.2,
Co.sub.2B, or CoW.sub.2B.sub.2 as detected by X-Ray diffraction
(XRD).
9. The sintered superhard compact body of claim 1, wherein tungsten
or tungsten carbide is not detected by X-Ray diffraction (XRD).
10. The sintered superhard compact body of claim 1, wherein the
tungsten and cobalt are from milling debris of milling bodies.
11. A sintered superhard compact body, comprising: superhard
particles; and a binder phase bonding the superhard particles
together, wherein the binder phase comprises tungsten and cobalt
derived from milling debris, wherein the binder phase comprises
stoichiometric or substoichiometric carbides, nitrides, oxides, or
sums thereof from aluminum, titanium or other transition metals of
group IV, V, or VI in the periodic table of elements, wherein the
milling debris is from a low tungsten content milling body.
12. The sintered superhard compact body of claim 11, wherein the
milling body is a cermet milling body.
13. The sintered superhard compact body of claim 11, wherein the
superhard particles are selected from a group of cubic boron
nitride, diamond, and diamond composite materials.
14. The sintered superhard compact body of claim 11, wherein a sum
of the tungsten and cobalt is in a range of from about 2 to about
10 percent by weight.
15. The sintered superhard compact body of claim 11, wherein a
ratio of tungsten to cobalt is in a range from 1.0 to 2.0.
16. The sintered superhard compact body of claim 11, wherein a
ratio of tungsten to cobalt is in a range from 1.0 to 1.8.
17. The sintered superhard compact body of claim 11, wherein a
ratio of tungsten over cobalt is in a range from 1.0 to 1.5.
18. The sintered superhard compact body of claim 11, further
comprising at least one boron containing tungsten, cobalt, or
tungsten-cobalt phases as detected by X-Ray diffraction (XRD).
19. A sintered superhard compact body of claim 11, wherein
superhard particles comprise 31 wt % cBN, wherein the binder phase
includes 5 wt % Al, 32 wt % Ti(C.sub.0.6N.sub.0.4), 32 wt %
substoichiometric TiN.sub.0.72 milled using cermet bodies in an
attritor mill giving an addition of 3.1+/-1 wt % W and 2.2+/-1 wt %
Co from the milling bodies.
20. The sintered superhard compact body of claim 19, further
comprising at least one phase selected from a group of WB.sub.2,
Co.sub.2B, or CoW.sub.2B.sub.2 as detected by X-ray diffraction
(XRD).
21. A method of making a superhard compact, comprising: providing
milling bodies; milling a powder mixture of superhard powder,
binder materials, and fluids with the milling bodies; and
incorporating cobalt and tungsten from the milling bodies into the
superhard compact, wherein the milling bodies are low tungsten
content milling bodies.
22. The method of making a superhard compact of claim 21, further
comprising preparing granules from a mixture of supperhard powder
blend, organic binder materials, and fluids.
23. The method of making a superhard compact of claim 21, further
comprising pre-compacting the granules to form a soft green part of
defined shape.
24. The method of making a superhard compact of claim 23, further
comprising heating the soft green part in a vacuum furnace to form
a hard green part.
25. The method of making a superhard compact of claim 21, further
comprising inserting one or more the hard green parts in a
container.
26. The method of making a superhard compact of claim 21, further
comprising sintering the container in a pressure cell at a
predetermined pressure and temperature.
27. The method of making a superhard compact of claim 21, further
comprising removing the container from the pressure cell to reveal
the superhard compact.
28. The method of making a superhard compact of claim 21, wherein
the superhard powder includes a material selected from the group of
cubic boron nitride, diamond, and diamond composite materials.
29. The method of making a superhard compact of claim 21, wherein
the granules comprise a mixture of cubic boron nitride and aluminum
in organic binder materials of polyethylene glycol.
30. The method of making a superhard compact of claim 21, wherein
the powder mixture contains W and Co containing compounds to
accomplish a desired composition.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority of provisional application,
No. 61/653,779, filed May 31, 2012. The application is related to
co-pending application, titled "CUTTING TOOLS MADE FROM STRESS FREE
CBN COMPOSITE MATERIAL AND METHOD OF PRODUCTION", which claims
priority of provisional application No. 61/653,699, filed on May
31, 2012. The application is further related to co-pending
application, titled "Method of making a cBN material", which claims
priority of provisional application No. 61/653,686, filed on May
31, 2012.
TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY
[0002] The present disclosure relates to a sintered superhard
material made from powdered composition suitable for use in the
manufacture of superhard abrasive compacts, and specifically to a
sintered body containing cubic boron nitride (cBN) which may be
used in cutting tools for hard part turning applications with
enhanced toughness and good consistency.
[0003] Polycrystalline cubic boron nitride (PcBN), diamond and
diamond composite materials are commonly used to provide a
superhard cutting surface for cutting tools such as those used in
metal machining.
[0004] It is generally accepted that such described materials
suffer from more or less brittle behavior, that is, the materials
exhibit undesirable random breakages in toughness demanding
operations, such as intermittent machining of hardened steel. This
brittleness entails partly as a result of the binder phase being
ceramic, but is also due to imperfect dispersion of cBN particles
and tungsten carbide mill debris. Imperfect dispersion leads to
mechanically weak parts, or defects, in the material.
[0005] Therefore, there is a need for homogeneous and consistent
dispersion in the material in order to produce a superhard compact
for hard part machining having superior toughness characteristics
to be used in toughness demanding operations, in particular in
intermittent hard part turning, or milling.
SUMMARY
[0006] In one embodiment, a sintered superhard compact body may
comprise superhard particles; and a binder phase bonding the
superhard particles together, wherein the weight percent ratio of
W/Co in the sintered compact falls between 1.0 and 2.0, and sum of
weight percent of W and Co in the sintered compact is in a range
from about 2 to about 20.
[0007] In another embodiment, a sintered superhard compact body may
comprise superhard particles; and a binder phase bonding the
superhard particles together, wherein the binder phase comprises
tungsten and cobalt derived from milling debris, wherein the binder
phase comprises stoichiometric or substoichiometric carbides,
nitrides, oxides, or sums thereof from aluminum, titanium or other
transition metals of group IV, V, or VI in the periodic table of
elements.
[0008] In yet another embodiment, a method of making a superhard
compact may comprise steps of providing milling bodies; milling a
powder mixture of superhard powder and a binder material, and
fluids with the milling bodies; and incorporating W and Co from the
milling bodies into the superhard compact.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The foregoing summary, as well as the following detailed
description of the embodiments, will be better understood when read
in conjunction with the appended drawings. It should be understood
that the embodiments depicted are not limited to the precise
arrangements and instrumentalities shown.
[0010] FIG. 1 is a backscattered scanning electron micrograph (BSE)
image of a microstructure of a sintered superhard compact body made
from a roll mill using cemented carbide milling bodies;
[0011] FIG. 2 is a backscattered scanning electron micrograph (BSE)
image of a microstructure of a sintered superhard compact body made
from a roll mill using cermet milling bodies;
[0012] FIG. 3 is a backscattered scanning electron micrograph (BSE)
image of a microstructure of a sintered superhard compact body made
from an attritor mill using cermet milling bodies according to an
embodiment;
[0013] FIG. 4 is a graph of flank wear progression for a cutting
tool made from materials milled by an attritor mill with cermet
milling bodies, compared with a commercial grade;
[0014] FIG. 5 is a graph of crater wear progression for a cutting
tool made from materials milled by an attritor mill with cermet
milling bodies, compared with a commercial grade; and
[0015] FIG. 6 is a graph of toughness test result for a cutting
tool made from materials milled by an attritor mill with cermet
milling bodies, compared with a commercial grade.
DETAILED DESCRIPTION
[0016] An embodiment provides a sintered superhard compact body
with a defined weight percent ratio of W/Co and its manufacturing
method. The superhard particles may be selected from a group of
cubic boron nitride, diamond, and diamond composite materials. The
composition of starting material used in producing the
polycrystalline cBN compact comprises cBN and a binder phase, in
powder or particular form. The binder phase may at least partially
melt and react with cBN and form bonding by reaction sintering
during high pressure and high temperature (HPHT) sintering.
[0017] An embodiment may improve the toughness of a cBN material
with an increased wear resistance and a reduction of variability of
tool life for a given application area. A superhard sintered
compact and a method for its production that provides significantly
improved microstructural homogeneity and better toughness than
other superhard sintered compacts.
[0018] Embodiments use milling bodies, such as cermet milling
bodies. Cermet milling bodies may be made from a raw material
powder blend which comprises 18% hexagonal close-packed (HCP) WC by
weight, 16% HCP Co, and balanced face centered cubic (FCC) TiCN.
After sintering, the cermet milling bodies may contain W in a range
from 15% to 20%, which may be dissolved in (FCC) (Ti, W) (C, N).
The cermet material may also contain up to 15% cobalt, which, in
turn, may contain up to 12% dissolved tungsten.
[0019] Dispersion of cBN particles is mainly accomplished during
the milling step. Milling, in general, as a means of comminution
and dispersion, is well known in the art. Commonly used milling
techniques in grinding ceramic powder include conventional ball
mills, tumbling ball mills, planetary ball mills, attritor mills,
and agitated ball mills. In conventional ball milling, the energy
input is determined by the size and density of the milling media,
the diameter of the milling pot and the speed of rotation. Since
the method requires that the balls tumble, rotational speeds, and
therefore energy are limited. Conventional ball milling is well
suited for milling powders with low to medium particle strength.
Typically, conventional ball milling is used where powders are to
be milled to a final particle size around 1 micron or more.
[0020] In planetary ball milling, the planetary motion of the
milling pots allows acceleration up to 20 times the gravitational
acceleration. When dense milling bodies are used, this allows for
substantially more energy in milling compared to conventional ball
milling. This technique is well suited for comminution with
particles of moderate strength, with final particle sizes of around
1 micron.
[0021] Attritor mills on the other hand consist of an enclosed
grinding chamber with an agitator that rotates at high speeds in
either a vertical or horizontal configuration. Milling bodies are
typically in the size ranging from 0.2 to 15 mm and, where
comminution is the objective, milling media typically are high
density cemented carbide. The high rotational speeds of the
agitator, coupled with high density, small diameter milling bodies,
provide high energy. Furthermore, the high energy in attritor mill
results in high shear in the slurry, which provides for very
successful co-dispersion, or blending of powders. Attritor mill
typically achieves finer particles and better homogeneity of
materials in the sintered compact than the other methods
mentioned.
[0022] An embodiment may use attritor or other mills with milling
bodies made from cemented carbide hard metal, also known as WC/Co
hard metal, containing 85-90% HCP WC, and 7-15% Co. In some
embodiments, the desirable form of milling debris may allow for a
longer milling time and improved dispersion. As used herein, the
term "milling debris" refers to any materials produced from milling
bodies or the linings of a mill due to the friction between
abrasive particles, milling bodies and linings. The dispersion of
the different phases during milling is critical. The maximum
possible dispersion is limited in prior art, by the fact that the
cemented carbide milling bodies wear and produce milling debris
containing high WC content. This may cause an increased WC content
in the PcBN blend with extended milling time. This is tolerable to
some degrees; however, it may cause considerable deterioration of
the material properties if the WC content becomes too high.
Therefore, because cemented carbide has much higher W content than
cermet, the tolerable milling time for cemented carbide milling
bodies is much lower than that for cermet milling bodies, which
greatly restricts the level of dispersion that can be achieved
through milling using cemented carbide milling bodies.
[0023] In other embodiments, cermet hard metal milling bodies may
comprise a composition of (Ti,W)(C,N). The composition may be
beneficial to add as a part of the final blank composition. Even in
these other embodiments, W and/or Co containing raw materials may
be added to achieve the desired final material composition. In one
embodiment, the tungsten and cobalt are from milling debris. By
using the cermet milling bodies, a more favorable form of milling
debris may be formed, where the milling debris is actually a part
of the raw material blend. The advantage of using cermet milling
debris as raw material is that the mill debris contains (Ti,W)(C,N)
and Co with the right proportion of W/Co and they are always
together. During a pre-sintering process or early stage of HPHT
sintering, the W in the (Ti,W)(C,N) is reduced to metallic W, which
dissolves in molten Co during HPHT sintering. Therefore, molten Co
may help distribute W uniformly around particles and helps increase
homogeneity of the reactions between Co, W, and Al with cBN and
binder phase particles. After HPHT sintering, at least some of the
Co and W have reacted and formed ceramic phases.
[0024] Similar to this concept, it is also possible to crush
sintered cermet solids into powder and blend it together with cBN
and ceramic binder phase materials to achieve the same effect. On
the contrary, if the PCBN blend is milled with cemented carbide
milling bodies, W from the mill debris will be too much to be
dissolved in Co. Even though with added Co powder in the blend, W
and Co particles are not always adjacent to each other. Therefore,
there are often large W or WC particles sitting in the
microstructure, which may not be desirable for the machining
application.
[0025] In one embodiment, superhard particles may comprise 31 wt %
cBN, wherein the binder phase includes 5 wt % Al, 32 wt %
Ti(C.sub.0.6N.sub.0.4), 32 wt % substoichiometric TiN.sub.0.72. The
materials are milled by using cermet bodies in an attritor mill
giving an addition of 3.1+/-1 wt % W and 2.2+/-1 wt % Co from the
milling bodies
[0026] In one embodiment, a ratio of tungsten to cobalt may be in a
range of 1.0 to 2.0. In another embodiment, a ratio of tungsten to
cobalt may be in a range of 1.0 to 1.8. In yet another embodiment,
a ratio of tungsten to cobalt may be in a range of 1.0-1.5.
[0027] PCBN based materials for hard part turning typically
comprise sintered bodies having a volume share in the range of 35
to 85 vol. % cBN particles, and a ceramic binder phase which
comprises carbides, nitrides, oxides, or sums thereof of aluminum,
titanium or any other transition metal group IV, V, or VI in the
periodic table of elements. The cBN based material is sintered in a
high pressure, high temperature (HPHT) process. Phase transitions
during the HPHT process result in generating new phases, such as,
borides, nitrides and carbonitrides, for example. Small amounts of
inevitable contaminants may be present in these materials, which
may be generated in certain process steps, such as, milling, which
gives rise to tungsten and cobalt content originating in the
milling bodies.
[0028] In an embodiment of a process to make a superhard compact,
raw superhard materials, such as cBN, may be blended by a milling
process with fluids and ceramic materials which comprises
stoichiometric or substoichiometric carbides, nitrides, oxides, or
sums thereof from aluminum, titanium or other transition metals of
group IV, V, or VI in the periodic table of elements. An embodiment
may further include steps of preparing granules from a mixture of
superhard powders, ceramic powders, organic binder materials, and
fluids; pre-compacting the granules to form a soft green part of
defined shape; heating the soft green part in a vacuum furnace to
form a hard green part; inserting one or more the hard green parts
in a container. An embodiment may further include steps of
sintering the hard greens in the container in a pressure cell at a
predetermined pressure and temperature; removing the container from
the pressure cell to reveal the superhard compact.
[0029] PCBN may be typically made by HPHT sintering of a powder
blend of cBN, ceramic phase and aluminum or aluminum compound, and
may be often formed in the shape of a large PCBN disc or "blank".
In addition, two phases attributable to the cBN and binder phase
material may be selected from a group of Al.sub.2O.sub.3,
TiB.sub.2, AlN, for example. And at least one boride containing W,
Co, or W--Co alloy phases may be detected by an X-Ray Diffraction
(XRD), such as WB.sub.2, Co.sub.2B, or CoW.sub.2B.sub.2. In some
embodiments, the W phase is not detected in the blank.
[0030] The PCBN blank may also be made from HPHT sintering of
pre-compacted hard green discs. In addition to cBN and added binder
phase material, such hard greens have intermediary phases that may
include AI.sub.3Ti, Ti.sub.2AlN, W, CoAl, AIB.sub.2 that are
produced in the pre-sintering step.
EXAMPLE 1
[0031] Example A. Powders of cBN (39% by weight), substoichiometric
TiN (ssTiN) (56% by weight) and Al (5% by weight) were milled in a
roll mill with cemented carbide milling bodies in isopropyl alcohol
for 2 hours. The slurry was then dried in an oven in air to remove
the alcohol. Then the powder was dispersed in ethanol (99.6% pure),
which was mixed with a polyethylene glycol (PEG) solution. The
slurry was then spray dried into spherical granules, which is
pre-compacted into round discs. The discs were fired in hydrogen at
about 400.degree. C. and then pre-sintered at 900.degree. C. in
vacuum. After pre-sintering, the hard green discs were loaded in a
cell and HPHT sintered at temperature around 1300 to 1450.degree.
C. with pressure of at least 2 GPa.
[0032] Example B. Powders of cBN (39% by weight), ssTiN (56% by
weight) and Al (5% by weight) were milled in a roll mill with
cermet milling bodies. ssTiN and Al powders were milled in ethanol
(99.6% pure) for 15 hours, and then cBN powders were added to the
slurry and milled for another 10 hours. Then the slurry was mixed
with a PEG solution after milling. The following spray drying,
pre-compaction, pre-sintering and HPHT processes were the same as
described in Example A.
[0033] Example C. Powders of cBN (39% by weight), ssTiN (27% by
weight), TiCN (28% by weight), and Al (6% by weight) were milled
together in ethanol in an attritor mill with cermet milling bodies
for 3 hours. The cermet milling bodies had the composition of
(weight %): W 17.36, Co 17.47, Ti 50.65, N 4.84, and C 9.83. The
slurry was mixed with a PEG solution after milling. The following
spray drying, pre-compaction, pre-sintering and HPHT processes were
the same as described in Example A.
[0034] Table 1 shows the W and Co contents by X-Ray Fluorescence
(XRF) and the calculated W/Co ratios and sum of W and Co contents
of Examples A, B and C. All three examples had the same W level
(4.2 to 4.5% by weight), but the Co level was much higher in
Example C than in the other two cases. In Example B, although the
powders were milled with cermet milling bodies, because the milling
bodies were grinding the surface of the milling jar, which had a WC
lining, WC mill debris might come from the WC lining as well as the
milling bodies. Therefore, the W/Co ratio might be much higher than
that from the cermet milling bodies. In Example C, the attritor
milling action determined that the wearing between milling bodies
was much more severe than from the mill jar. As a result, even
though the attritor milling jar was made of stainless steel, there
was not much mill debris from the attritor milling jar. The iron
content in the final blend was only about 0.3% by weight. The mill
debris in attritor milling with cermet milling bodies mainly came
from the milling bodies, which resulted in the low W/Co ratio.
[0035] FIGS. 1, 2 and 3 show the back scattered electronic (BSE)
micrographs of examples A, B and C. FIG. 1 shows the BSE image of
example A with 39 wt % cBN which was roll milled with cemented
carbide milling bodies for two hours. FIG. 2 illustrates the BSE
image of example B with 39 wt % cBN which was roll milled with
cermet milling bodies for 25 hours. FIG. 3 illustrates the BSE
image of example C with 39wt % cBN which was attritor milled with
cermet milling bodies for three hours. It can be seen that with the
same W level, dispersion in Example A is not very good. Dispersions
in Example B and C much improved compared to Example A. It should
be noted that in both Examples A and B, because of the excess W,
large mill debris (white spots in the micrographs) were visible,
whereas in example C, because W was dissolved in Co and uniformly
distributed in the microstructure, large mill debris was
scarce.
TABLE-US-00001 TABLE 1 Milling W Co W + Exam- Milling Time (wt (wt
Co ple Mill Body (hours) %) %) W/Co (wt %) A Roll Cemented 2 4.3
0.2 21.5 4.5 carbide B Roll Cermet 25 4.5 0.8 5.6 5.3 C Attritor
Cermet 3 4.2 3.4 1.2 7.6
EXAMPLE 2
[0036] Table 2 shows a number of other material blends which were
milled using different milling bodies (cermet or cemented carbide)
and different mills (roll mill or attritor mill). The lining of the
roll mills might be stainless steel (ss) or cemented carbide (cc).
All materials had a good dispersion of the constituents except for
mill D, which was milled for too short duration. The W/Co ratio was
the highest (over 10) in the case of milling with cemented carbide
bodies, because the W/Co ratio was high in the milling body
material. In the case of roll milling with cermet bodies, again
because the experiments were conducted in mills with cemented
carbide lining, WC mill debris from the lining in addition to the
cermet milling bodies contributed to the higher overall W/Co ratio
(such as over 5) than that of cermet material. The lowest W/Co
ratio was achieved through attritor milling with cermet bodies,
because, as explained above, majority of the milling debris came
from the cermet milling bodies. It should be noted that it was
possible to achieve similar low W/Co ratio through roll milling
with stainless steel lining. However, it required much longer time
than attritor milling to achieve the same dispersion and W level,
and the iron content would be rather high due to mill debris from
the milling jar.
TABLE-US-00002 TABLE 2 cBN Lining Milling W Co W + Co Example (vol
%) Mill of Mill Body (wt %) (wt %) W/Co (wt %) D 38 attritor Ss
cermet 3.1 2.0 1.6 5.1 E 47 roll Cc cemented 5.9 0.5 11.8 6.4
carbide F 47 roll Cc cermet 4.5 0.8 5.6 5.3 G 47 attritor Ss
cemented 2.1 0.2 10.5 2.3 carbide H 47 attritor Ss cermet 3.0 2.2
1.4 5.2 I 65 roll Ss cemented 5.8 0.5 11.6 6.3 carbide J 65 roll Cc
cermet 3.5 0.6 5.8 4.1 K 65 attritor Ss cermet 2.7 2.1 1.3 4.8 L 65
attritor Ss cermet 6.6 5.4 1.2 12.0
EXAMPLE 3
[0037] Powders of aluminum (5 wt %%), TiCN (32 wt %), ssTiN (32 wt
%), and cBN (31 wt %) were milled in an attritor mill with cermet
milling bodies in ethanol for 5 hours. After milling, the slurry
was mixed with a PEG solution and the material was spray dried,
pre-compacted, pre-sintered and HPHT sintered in the same way as
described in Example 1. Then tips were Electrical Discharge
Machining (EDM) cut from HPHT sintered discs and standard cutting
tools were made and machining tests were conducted together with a
commercial hard part turning grade, which was referred to as
"comparison grade" or "Comparison" in the following text, FIGS. 4,
5 and 6 and Table 4.
[0038] Table 3 shows the XRD data after pre-sintering and HPHT for
Example 3. Co and W had reacted to form several different reaction
products. In the material after HPHT, cBN, TiCN, Al.sub.2O.sub.3,
and TiB.sub.2 were detected, as expected traditionally. The new
phases were some boron-containing tungsten, cobalt, or
tungsten-cobalt phases, such as WB.sub.2, Co.sub.2B, or
CoW.sub.2B.sub.2. Most notably, the intermediary phases after
pre-sintering, such as AIB.sub.2, Ti.sub.2AlN, W, were not visible
after HPHT. The TiN peak detectable after pre-sintering also
disappeared after HPHT due to solid state diffusion and
homogenization between the TiCN/TiN binders during HPHT
sintering.
TABLE-US-00003 TABLE 3 Variant M Peak HPHT Presint. AlB2 5 Al2O3 3
cBN 28 40 Co2B 2 CoW2B2 6 Ti2AlN 1 TiB2 10 TiCN 100 100 TiN 55 W 8
W2B 3
[0039] FIGS. 4 and 5 show the flank wear and crater wear test
results on Example 3 compared with the comparison grade. The test
was conducted on 8620 steel with continuous cutting. Cutting was
stopped every 2 to 4 minutes, and flank wear and crater wear were
measured and recorded. It could be seen that Example 3 had similar
crater wear to the comparison grade, but much lower flank wear than
the comparison grade.
[0040] Table 4 shows a series of wear test by cutting 8620 steel on
Example 3 compared with the comparison grade. Flank wear was
measured every 4 minutes and tool life was determined based on 0.15
mm of flank wear. Different cutting speeds (240 and 180 m/min),
feeds (0.1 and 0.15 mm/rev), and depth of cut (0.1 to 0.2 mm/doc)
were tested. It could be seen that in every case, Example 3 has
much longer tool life than the comparison grade illustrating this
material may have a potential for broad application.
TABLE-US-00004 TABLE 4 Example 3 Comparison Cutting (tool life,
minutes) (tool life, minutes) Parameters Group 1 Group 2 Average
Group 1 Group 2 Average 240 m/min, 38.7 37.1 37.9 21.2 21.0 21.1
0.1 mm/rev., 0.1 mm doc 180 m/min., 26.5 22.9 24.7 21.0 21.4 21.2
0.15 mm/rev., 0.2 mm doc 180 m/min., 84.0 84.0 55.8 55.8 0.1
mm/rev., 0.1 mm doc
[0041] FIG. 6 shows the toughness test result on Example 3 compared
with the comparison grade. The test was conducted on 52100 steel
with hardness of Rc 60 to 62. Four samples of each were tested and
the failing feed of each sample was recorded. Traditionally,
toughness increases with cBN content. However, it could be seen
that although Example 3 had much lower cBN content than the
comparison grade, 38 vol % in Example 3 and 50 vol % in the
comparison grade, it had the same toughness level as the comparison
grade, and much better consistency. This could be attributed to the
higher Co content and more uniform distribution of mill debris.
[0042] While reference has been made to specific embodiments, it is
apparent that other embodiments and variations can be devised by
others skilled in the art without departing from their spirit and
scope. The appended claims are intended to be construed to include
all such embodiments and equivalent variations.
* * * * *