U.S. patent application number 11/517806 was filed with the patent office on 2007-03-08 for brazed diamond tools and methods for making the same.
Invention is credited to Chien-Min Sung.
Application Number | 20070051355 11/517806 |
Document ID | / |
Family ID | 32041789 |
Filed Date | 2007-03-08 |
United States Patent
Application |
20070051355 |
Kind Code |
A1 |
Sung; Chien-Min |
March 8, 2007 |
Brazed diamond tools and methods for making the same
Abstract
Multi-layered superabrasive tools and methods for the making
thereof are disclosed and described. In one aspect, superabrasive
particles are chemically bonded to a matrix support material
according to a predetermined pattern by a braze alloy. The brazing
alloy may be provided as a powder, thin sheet, or sheet of
amorphous alloy. A template having a plurality of apertures
arranged in a predetermined pattern may be used to place the
superabrasive particles on a given substrate or matrix support
material.
Inventors: |
Sung; Chien-Min; (Taipei
County, TW) |
Correspondence
Address: |
THORPE NORTH & WESTERN, LLP.
8180 SOUTH 700 EAST, SUITE 200
SANDY
UT
84070
US
|
Family ID: |
32041789 |
Appl. No.: |
11/517806 |
Filed: |
September 8, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10259168 |
Sep 27, 2002 |
7124753 |
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11517806 |
Sep 8, 2006 |
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09935204 |
Aug 22, 2001 |
6679243 |
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10259168 |
Sep 27, 2002 |
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09399573 |
Sep 20, 1999 |
6286498 |
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09935204 |
Aug 22, 2001 |
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08835117 |
Apr 4, 1997 |
6039641 |
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09399573 |
Sep 20, 1999 |
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08832852 |
Apr 4, 1997 |
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09399573 |
Sep 20, 1999 |
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10109531 |
Mar 27, 2002 |
6884155 |
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11517806 |
Sep 8, 2006 |
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09558582 |
Apr 26, 2000 |
6368198 |
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10109531 |
Mar 27, 2002 |
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09447620 |
Nov 22, 1999 |
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09558582 |
Apr 26, 2000 |
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Current U.S.
Class: |
125/12 |
Current CPC
Class: |
B01J 2203/0645 20130101;
B24B 53/017 20130101; C22C 1/051 20130101; B24D 7/02 20130101; B01J
2203/0655 20130101; B24D 7/066 20130101; B01J 2203/061 20130101;
B24D 3/06 20130101; B24D 3/08 20130101; B01J 2203/068 20130101;
C22C 26/00 20130101; C22C 45/00 20130101; B01J 2203/0685 20130101;
B24D 18/00 20130101; C04B 35/52 20130101; C22C 21/06 20130101; E21B
10/5676 20130101; B22F 2999/00 20130101; B23D 65/00 20130101; B23K
35/0233 20130101; B23P 15/28 20130101; B22F 2999/00 20130101; B23D
61/18 20130101; B01J 2203/066 20130101; B24D 99/005 20130101; B22F
2005/001 20130101; B01J 3/062 20130101; B22F 2999/00 20130101; B23D
61/028 20130101; C22C 2204/00 20130101; B24B 53/12 20130101; B01J
2203/062 20130101; B24D 5/066 20130101; B28D 1/041 20130101; B22F
2999/00 20130101; B24D 2203/00 20130101; B23D 61/04 20130101; C22C
26/00 20130101; B22F 1/0011 20130101; B22F 2207/03 20130101; C22C
1/051 20130101; B22F 2207/03 20130101; B22F 2003/1046 20130101;
B22F 3/004 20130101 |
Class at
Publication: |
125/012 |
International
Class: |
B28D 1/02 20060101
B28D001/02 |
Claims
1. A method of making a superabrasive tool, comprising: a)
providing a plurality of matrix support material layers having
exposed surfaces and a plurality of sheets of amorphous brazing
alloy; and b) brazing a plurality of superabrasive particles
directly to the exposed surface of the matrix support material
using the plurality of sheets of amorphous brazing alloy.
2. The method of claim 1, further comprising: a) affixing the
superabrasive particles on the plurality of amorphous braze sheets
in a predetermined pattern; b) applying the plurality of sheets
having superabrasive particles thereon to the exposed surfaces of
the matrix support material to form a plurality of individual
superabrasive segments; c) assembling the individual superabrasive
segments into a tool precursor having a three-dimensional
arrangement of superabrasive particles in accordance with a
predetermined pattern; and d) consolidating the tool precursor by
heating to a temperature sufficient to melt the brazing alloy and
sinter the matrix support material.
3. The method of claim 1, wherein the brazing alloy includes a
material selected from the group consisting of titanium, vanadium,
chromium, zirconium, molybdenum, tungsten, manganese, iron, silicon
and aluminum.
4. The method of claim 3, wherein the brazing alloy includes
between about 2% and about 50% by weight of a material selected
from the group consisting of chromium, manganese, titanium, silicon
and aluminum.
5. The method of claim 4, wherein the material is chromium.
6. The method of claim 1, wherein the sheets of amorphous brazing
alloy have a liquidus temperature of less than 1,100.degree. C.
7. The method of claim 1, further comprising: a) affixing the
superabrasive particles on the exposed surface of the matrix
support material; and b) applying the sheet of amorphous braze on
the superabrasive particles.
8. The method of claim 7, wherein the superabrasive particles are
affixed to the matrix support material using an adhesive.
9. The method of claim 7, wherein the step of affixing further
comprises placing the superabrasive particles in a predetermined
pattern.
10. The method of claim 1, wherein the superabrasive particles are
placed in a predetermined pattern by the steps of: a) providing a
template having a plurality of apertures corresponding to the
predetermined pattern; b) placing the template on a transfer sheet;
c) filling the apertures with the superabrasive particles; d)
removing the template, such that the superabrasive particles remain
in place on the transfer sheet in accordance with the predetermined
pattern of the template; and e) transferring the superabrasive
particles to the exposed surface of the substrate using the
transfer sheet, such that the superabrasive particles become
affixed to the exposed surface of the substrate in accordance with
the predetermined pattern.
11. The method of claim 10, wherein the sheet of amorphous brazing
alloy is the transfer sheet.
12. A superabrasive tool comprising: a) a plurality of consolidated
metal support material layers each having a plurality of
superabrasive particles; and b) a plurality of sheets of amorphous
brazing alloy chemically bonding the plurality of superabrasive
particles to each consolidated metal support material layers.
13. The superabrasive tool of claim 12, wherein the brazing alloy
includes a material selected from the group consisting of titanium,
vanadium, chromium, zirconium, molybdenum, tungsten, manganese,
iron, silicon and aluminum.
14. The superabrasive tool of claim 13, wherein the brazing alloy
includes between about 2% and 50% by weight of a material selected
from the group consisting of chromium, manganese, titanium, silicon
and aluminum.
15. The superabrasive tool of claim 13, wherein the material is
chromium.
16. The method of claim 12, wherein the sheets of amorphous brazing
alloy have a liquidus temperature of less than 1,100.degree. C.
17. The superabrasive tool of claim 12, wherein the plurality of
superabrasive particles are placed in a predetermined pattern.
18. The superabrasive tool of claim 17, wherein the predetermined
pattern consists of superabrasive particles positioned
substantially along an exterior edge of the superabrasive tool.
19. The superabrasive tool of claim 17, wherein the predetermined
pattern comprises an exterior portion concentration of
superabrasive particles that is higher than an interior portion
concentration of superabrasive particles.
20. The superabrasive tool of claim 17, wherein the predetermined
pattern is a uniform grid.
Description
PRIORITY INFORMATION
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/259,168, filed on Sep. 27, 2002, which is a
continuation-in-part of U.S. patent application Ser. No.
09/935,204, filed Aug. 22, 2001, which is a continuation-in-part of
U.S. patent application Ser. No. 09/399,573, filed Sep. 20, 1999,
now issued as U.S. Pat. No. 6,286,498, which is a
continuation-in-part of U.S. patent application Ser. No.
08/835,117, filed Apr. 4, 1997, now issued as U.S. Pat. No.
6,039,641, and of U.S. patent application Ser. No. 08/832,852,
filed Apr. 4, 1997, now abandoned, all of which are incorporated
herein by reference.
[0002] This application is also a continuation-in-part of U.S.
patent application Ser. No. 10/109,531, filed Mar. 27, 2002, which
is a continuation-in-part of U.S. patent application Ser. No.
09/588,582, filed Apr. 26, 2000, now issued as U.S. Pat. No.
6,368,198, which is a continuation-in-part of U.S. patent
application Ser. No. 09/447,620, filed Nov. 22, 1999, now
abandoned, all of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0003] The present invention relates generally to tools having
diamond particles chemically bonded to a matrix support material,
or a substrate, and arranged in a predetermined pattern.
Accordingly, the present invention involves the fields of
chemistry, metallurgy, and materials science.
BACKGROUND OF THE INVENTION
[0004] Abrasive tools have long been used in numerous applications,
including cutting, drilling, sawing, grinding, lapping and
polishing of materials. Because diamond is the hardest abrasive
material currently known, it is widely used as a superabrasive on
saws, drills, and other devices, which utilize the abrasive to cut,
form, or polish other hard materials.
[0005] Diamond tools are particularly indispensable for
applications where other tools lack the hardness and durability to
be commercially practical. For example, in the stone industry,
where rocks are cut, drilled, and sawed, diamond tools are about
the only tools that are sufficiently hard and durable to make the
cutting, etc., economical. If diamond tools were not used, many
such industries would be economically infeasible. Likewise, in the
precision grinding industry, diamond tools, due to their superior
wear resistance, are uniquely capable of developing the tight
tolerances required, while simultaneously withstanding wear
sufficiently to be practical.
[0006] A typical superabrasive tool, such as a diamond saw blade,
is manufactured by mixing diamond particles (e.g., 40/50 U.S. mesh
saw grit,) with a suitable metal support matrix powder (e.g.,
cobalt powder of 1.5 micrometer in size). The mixture is then
compressed in a mold to form the right shape (e.g., a saw segment).
This "green" form of the tool is then consolidated by sintering at
a temperature between 700-1200.degree. C. to form a single body
with a plurality of abrasive particles disposed therein. Finally,
the consolidated body is attached (e.g., by traditional brazing or
soldering) to a tool body; such as the round blade of a saw, to
form the final product.
[0007] Despite their prevailing use, diamond tools generally suffer
from several significant limitations, which place unnecessary
limits on their useful life. For example, the abrasive diamond or
cubic boron nitride (CBN) particles are not distributed uniformly
in the matrix that holds them in place. As a result, the abrasive
particles are not positioned to maximize efficiency for cutting,
drilling, grinding, polishing, etc.
[0008] The distance between diamond or CBN abrasive particles
determines the work load each particle will perform. Improper
spacing of the diamond or CBN abrasive particles typically leads to
premature failure of the abrasive surface or structure. Thus, if
the diamond/CBN abrasive particles are too close to one another,
some of the particles are redundant and provide little or no
assistance in cutting or grinding. In addition, excess particles
add to the expense of production due the high cost of diamond and
cubic boron nitride. Moreover, these non-performing diamond or CBN
particles can block the passage of debris, thereby reducing the
cutting efficiency. Thus, having abrasive particles disposed too
close to one another adds to the cost, while decreasing the useful
life of the tool.
[0009] On the other hand, if abrasive particles are spaced too far
apart, the workload (e.g., the impact force exerted by the work
piece) for each particle becomes excessive. The sparsely
distributed diamond or CBN abrasive particles may be crushed, or
even dislodged from the matrix into which they are disposed. The
damaged or missing abrasive particles are unable to fully assist in
the workload. Thus, the workload is transferred to the surviving
abrasive particles. The failure of each abrasive particle causes a
chain reaction which soon renders the tool ineffective to cut,
drill, grind, etc.
[0010] Different applications may require different size of diamond
(or cubic boron nitride) abrasive particles. For example, drilling
and sawing applications may require a large sized (20 to 60 U.S.
mesh) diamond grit to be used in the final tool. The metal
substrate of the tool is typically selected from cobalt, nickel,
iron, copper, bronze, alloys thereof, and/or mixtures thereof. For
grinding applications, a small sized (60/400 U.S. mesh) diamond
grit (or cubic boron nitride) is mixed with either metal (typically
bronze), ceramic/glass (typically a mixture of oxides of sodium,
potassium, silicon, and aluminum) or resin (typically
phenolic).
[0011] Often the tool may include a matrix support material, such
as a metal powder, which holds or supports the diamond particles.
However, because diamond or cubic boron nitride is much larger than
the matrix powder (300 times in the above example for making saw
segments), and it is much lighter than the latter (about 1/3 in
density for making saw segments), it is very difficult to mix the
two to achieve uniformity. Moreover, even when the mixing is
thorough, diamond particles can still-segregate from metal powder
in the subsequent treatments such as pouring the mixture into a
mold, or when the mixture is subjected to vibration. The
distribution problem is particularly troublesome for making diamond
tools when diamond is mixed in the metal support matrix.
[0012] There is yet another limitation associated with the many
methods of positioning diamond grits in a tool. Many times a metal
bond diamond tool requires different sizes of diamond grits and/or
different diamond concentrations to be disposed at different parts
of the same diamond tool. For example, saw segments tend to wear
faster on the edge or front than the middle. Therefore, higher
concentrations and smaller diamond grit are preferred in these
locations to prevent uneven wear and thus premature failure of the
saw segment. These higher concentration/smaller size segments (i.e.
"sandwich" segments) are difficult to fabricate by mixing diamond
particles with metal powder. Thus, despite the known advantages of
having varied diamond grit sizes and concentration levels, such
configurations are seldom used because of the lack of a practical
method of making thereof.
[0013] Another drawback of many diamond tools is that the abrasive
particles, or "grits" are insufficiently attached to the tool
substrate, or matrix support material, to maximize useful life of
the cutting, drilling, polishing, etc., body. In fact, in most
cases, diamond grits are merely mechanically embedded in the matrix
support material. As a result, diamond grits are often knocked off
or pulled out prematurely. Moreover, the grit may receive
inadequate mechanical support from the loosely bonded matrix under
work conditions. Hence, the diamond particles may be shattered by
the impact of the tool against the workpiece to which the abrasive
is applied.
[0014] It has been estimated that, in a typical diamond tool, less
than about one tenth of the grit is actually consumed in the
intended application (i.e. during actual cutting, drilling,
polishing, etc). The remainder is wasted by either being leftover
when the tool's useful life has expired, or by being pulled-out or
broken during use due to poor attachment and inadequate support.
Most of these diamond losses could be avoided if the diamond
particles can be properly positioned in and firmly attached to the
surrounding matrix.
[0015] In order to maximize the mechanical hold on the diamond
grits, they are generally buried deep in the substrate matrix. As a
result, the protrusion of the diamond particles above the tool
surface is generally less than desirable. Low grit protrusion
limits the cutting height for breaking the material to be cut. As a
result, friction increases and limits the cutting speed and life of
the cutting tool.
[0016] In order to anchor diamond grit firmly in the support
matrix, it is highly desirable for the matrix to form carbide
around the surface of the diamond. The chemical bond so formed is
much stronger than the traditional mechanical attachment. The
carbide may be formed by reacting diamond with suitable carbide
formers such as a transition metal. Typical carbide forming
transition metals are: titanium (Ti), vanadium (V), chromium (Cr),
zirconium (Zr), molybdenum (Mo), and tungsten (W).
[0017] The formation of carbide requires that the carbide former be
deposited around the diamond and that the two subsequently be
caused to react to form carbide. Moreover, the non-reacted carbide
former must also be consolidated by sintering or other means. All
these steps require treatment at high temperatures. However,
diamond may be degraded when exposed to a temperature above about
1,000.degree. C. The degradation is due to either the reaction with
the matrix material or the development of micro-cracks around metal
inclusions inside the crystal. These inclusions are often trapped
catalysts used in the formation of synthetic diamond.
[0018] Most carbide formers are refractory metals so they may not
be consolidated below a temperature of about 1,200.degree. C.
Hence, refractory carbide formers are not suitable as the main
constituent of the matrix support material.
[0019] There are, however, some carbide formers that may have a
lower melting temperature, such as manganese (Mn), iron (Fe),
silicon (Si), and aluminum (Al). However, these carbide formers may
have other undesirable properties that prohibit them from being
used as the primary constituent of the matrix support material. For
example, both manganese and iron are used as catalysts for
synthesizing diamond at high pressure (above 50 Kb). Hence, they
can catalyze diamond back to graphite during the sintering of the
matrix powder at a lower pressure. The back conversion is the main
cause of diamond degradation at high temperature.
[0020] Aluminum, on the other hand, has a low melting point
(660.degree. C.), thus, making it easy to work with for securing
the diamond particles. However, the melting point of aluminum can
be approached when diamond grit is cutting aggressively. Hence,
aluminum may become too soft to support the diamond grit during the
cutting operation. Moreover, aluminum tends to form the carbide
Al.sub.4C.sub.3 at the interface with diamond. This carbide is
easily hydrolyzed so it may be disintegrated when exposed to
coolant. Hence, aluminum typically is not a suitable carbide former
to bond diamond in a matrix.
[0021] To avoid the high temperature of sintering, carbide formers,
such as tungsten, are often diluted as minor constituents in the
matrix that is made of primarily either Co or bronze. During the
sintering process, there is a minimal amount, if any, of liquid
phase formed. The diffusion of carbide former through a solid
medium toward diamond is very slow. As a result, the formation of
carbide on the surface of diamond is negligible. Therefore, by
adding a carbide former as a minor matrix constituent, the
improvement of diamond attachment is marginal at best.
[0022] In order to ensure the formation of carbide on the surface
of diamond, the carbide former may be coated onto the diamond
before mixing with the matrix powder. In this way, the carbide
former, although it may be a minor ingredient in the matrix, can be
concentrated around diamond to form the desired bonding.
[0023] The coating of diamond may be applied chemically or
physically. In the former case, the coated metal is formed by a
chemical reaction, generally at a relatively high temperature. For
example, by mixing diamond with carbide formers such as titanium or
chromium, and heating the mixture under a vacuum or in a protective
atmosphere, a thin layer of the carbide former may be deposited
onto the diamond. Increasing temperature may increase the thickness
of the coating. The addition of a suitable gas (e.g. HCl vapor)
that assists the transport of the metal may also accelerate the
deposition rate. Alternatively, the coating may be performed in a
molten salt.
[0024] In addition to sintering, infiltration is also a common
technique for making diamond tools; in particular for drill bits
and other specialty diamond tools that contain large (i.e. greater
than U.S. mesh 30/40) diamond grit. Most commonly used infiltrants
for these tools are copper based alloys. These infiltrants must
flow and penetrate the small pores in the matrix powder. In order
to avoid the diamond degradation at high temperature, the melting
point of the infiltrant must be low. Hence, the infiltrant often
contains a low melting point constituent, such as zinc (Zn). In
addition to lowering the melting point of the infiltrant, the low
melting point constituent also reduces the viscosity so the
infiltrant can flow with ease. However, as most carbide formers
tend to increase the melting point of the infiltrant, they are
excluded from most infiltrants. As a result, these infiltrants
cannot improve the bonding of diamond.
[0025] One specific process that has become dependent on the use of
diamond tools is chemical mechanical polishing (CMP). This process
has become standard in the semi-conductor and computer industry for
polishing wafers of ceramics, silicon, glass, quartz, etc. In
general terms, the work piece to be polished is held against a
spinning polishing pad of polyurethane, or other suitable material.
The top of the pad holds a slurry of acid and abrasive particles,
usually by a mechanism such as fibers, or small pores, which
provide a friction force sufficient to prevent the particles from
being thrown off of the pad due to the centrifugal force exerted by
the pad's spinning motion. Therefore, it is important to keep the
top of the pad as flexible as possible, and to keep the fibers as
erect as possible, or to assure that there are an abundance of open
and pores available to receive new abrasive particles.
[0026] A problem with maintaining the top of the pad is caused by
an accumulation of polishing debris coming from the work piece,
abrasive slurry, and polishing disk. This accumulation causes a
"glazing" or hardening of the top of the pad, and significantly
decreases the pad's overall polishing performance. Therefore,
attempts have been made to revive the top of the pad by "combing"
or "cutting" it with various devices. This process has come to be
known as "dressing" or "conditioning" the CMP pad. The device most
widely used for pad dressing is a disk with a plurality of super
hard crystalline particles, such as diamond particles or cBN
particles attached thereto.
[0027] Dressing disks made by conventional methods share several
problems with other superabrasive tools, made by conventional
methods. However, such issues may have a much greater impact on the
CMP process. For example, poor superabrasive grit retention may
lead to scratching and ruining of the work piece. Uneven work
loading of the superabrasive grits resulting from clustered or
unevenly spaced particle groups may cause overdressing of certain
pad areas and under dressing of others, which results in unsuitable
work piece polishing. Moreover, when the superabrasive particles of
dressing disks do not extend to a uniform height above the
substrate surface of the disk uneven dressing of the CMP pad is
further propagated, because many particles from the dresser may not
touch the pad.
[0028] In addition to the above-recited issues with particle
retention and distribution, the CMP pad dressing process itself
creates additional issues that make uncontrolled superabrasive
particle placement unacceptable. For example, the downward pressing
force of a dressing disk on a CMP may depress the pad upon contact
with the leading edge of the dresser, and prevent the remaining
superabrasive particles on the pad dresser from sufficiently
contacting the pad to achieve even dressing.
[0029] Warping of the pad dresser working surface during the
brazing process also often causes abrasive particles to dislodge.
During the brazing process the pad dresser must be exposed to very
high temperatures. Exposure to this extreme heat can cause the
working surface of the pad dresser to warp, thus compromising the
smoothness and planarity of the pad dresser's working surface. As a
result, the braze portion of the working surface will be rough,
having high and low spots. Such spots are undesirable, as they may
cause the braze to begin flaking off, and making micro-scratches on
the polished surface of the work piece.
[0030] As a result, suitable methods of maximizing the efficiency,
useful life, and other performance characteristics of diamond tools
are continually being sought.
SUMMARY OF THE INVENTION
[0031] It has been recognized by the inventor that it would be
advantageous to develop a method for making diamond tools which
meets the challenges discussed above.
[0032] In one aspect, the present invention resolves the problems
set forth above by providing a method for forming metal bonded
diamond or other superabrasive tools having a customized pattern of
individual grit placement. Because the distribution of the diamond
grits is controlled, the diamond grits can be disposed in detailed
patterns which cause a specific pattern of tool wear, including
uniform wear. Further, each superabrasive grit is more fully
utilized, and there is no need for redundant superabrasive grits as
a back up. Therefore, the cost of making the metal bond diamond or
other superabrasive tools can be minimized by reducing the overall
amount of superabrasive particles needed.
[0033] In accordance with another aspect of the present invention,
the process involves providing a substrate, and then brazing a
plurality of superabrasive particles directly to an exposed surface
of the substrate in accordance with a predetermined pattern, thus
chemically bonding the diamond particles in place on the substrate
with a brazing alloy.
[0034] In one aspect of the invention, the brazing alloy may be
provided as a layer of amorphous braze alloy, a powder, or rolled
continuous film. The brazing alloy is chosen to contain an element
which will chemically bond with the superabrasive particles and the
support material, such as titanium, vanadium, chromium, zirconium,
molybdenum, tungsten, manganese, iron, silicon, aluminum and
mixtures or alloys of these elements. In a more detailed aspect of
the present invention, the brazing alloy may be applied either
before or after the superabrasive particles are affixed to the
substrate. A wide variety of brazing alloys may be used in
connection with the present invention to bond the diamond particles
to the substrate. The brazing alloy should braze the superabrasive
particles to the substrate at a temperature which avoids
back-conversion of diamond to carbon. In a more detailed aspect of
the present invention, the brazing is carried out at a temperature
of less than about 1,100.degree. C.
[0035] The process of bonding the diamond particles to the
substrate using the brazing alloy may be accomplished by a variety
of methods. In one aspect, the brazing alloy may be applied to the
exposed surface of the substrate, after the diamond particles have
been distributed thereon. The brazing alloy is then heated to a
temperature sufficient to braze (i.e. chemically bond) the diamond
particles to the substrate. This same principle applies when the
diamond particles are used in connection with a matrix support
material rather than, or in addition to a substrate. In another
aspect, the brazing alloy may be first placed on the exposed
surface of the substrate or matrix support material, and the
diamond particles are then distributed on or in the brazing alloy
in accordance with a predetermined pattern. Heating to a
temperature sufficient to attain chemical bonding of the diamond
particles to the substrate or matrix support material then
ensues.
[0036] The arrangement of the diamond particles in a predetermined
pattern on the matrix support material may be accomplished by a
variety of methods. However, in one aspect, such a process includes
using a template having a plurality of apertures in a desired
pattern. Typically, the template is placed on the surface where the
diamond particles are to be affixed, and the apertures are filled
with diamond particles. As the particles fill the apertures, they
may be subjected to pressure or otherwise held in place on the
desired surface using an organic binder or adhesive. Next, the
template may be removed, and depending on the requirements of the
tool being formed, the diamond particles may be further adjusted on
the surface of the substrate. Because of the template, the
particles are each positively planted or positioned, at specific
locations and held according to a predetermined pattern on the
substrate or matrix support material. In a more detailed aspect, a
plurality of substrate or matrix support material layers with
diamond particles thereon or therein, may then be bonded together
to form a tool having a three dimensional arrangement of diamond or
other superabrasive particles in accordance with a predetermined
pattern.
[0037] In another aspect of the present invention, the
superabrasive particles may also be affixed to a transfer plate and
then transferred to the substrate. In one aspect of this
embodiment, the transfer plate can be made of metal or plastic, and
may be flexible or rigid. The affixing of superabrasive particles
to the transfer plate can be facilitated by coating the transfer
plate with a thin layer of adhesive. The template is then used to
distribute the superabrasive particles onto the transfer plate in
the desired predetermined pattern. The transfer plate having
superabrasive particles adhered thereto on one side is pressed
against the substrate or matrix material. The superabrasive
particles are transferred to the matrix support layer by adhering
to an adhesive coated on the surface of the matrix support
material. For ease of processing, the adhesive coated on the
substrate preferably adheres the superabrasive particles more
strongly than the adhesive coated on the transfer plate.
[0038] Next, the brazing alloy sheet is placed on top of the
substrate having abrasive particles adhered thereto. Alternatively,
a brazing powder may be sprinkled on the surface of the substrate
having superabrasives affixed thereto. In an alternative aspect of
the present invention, a slurry of brazing powder may be formed and
then applied to the substrate or matrix support material having
superabrasives adhered thereto, for example, by spraying, pasting,
etc.
[0039] In one variation of the transfer plate method, the transfer
plate is a sheet of amorphous braze which then becomes part of the
final tool. A plurality of superabrasives may be affixed to the
sheet of amorphous braze using an adhesive, or otherwise held in
place, in a predetermined pattern. The sheet of amorphous braze
having superabrasives affixed thereon is then placed on a
substrate. In a more detailed aspect of this embodiment of the
present invention, a template is used to create a specific pattern
of superabrasives on the sheet of amorphous braze in a similar
manner as when affixing the superabrasives to a substrate. The
apertures of the template are configured to admit one superabrasive
particle in each aperture. Once all the apertures have been filled
with superabrasive particles, any excess particles are removed, and
the abrasive particles are pressed into the sheet of amorphous
braze to embed them therein, by using a generally flat surface such
as a steel plate. Alternatively, rather than pressing the particles
into the brazing alloy sheet, they may be held in place by a tacky
substance, or adhesive, such as a glue, or other polymeric resin.
The template is then removed and sheet of brazing alloy containing
the abrasive particles is placed on or affixed to a substrate with
an adhesive, for example acrylic glue. Finally, the whole assembly
is brazed in a vacuum furnace to complete the brazing process and
firmly fix the abrasive particles to the substrate or matrix
support material. In one aspect of the invention, the flexible
sheet of brazing alloy may also be affixed to the substrate or
matrix support material prior to introduction of the abrasive
particles.
[0040] The arrangement of apertures used in the template may be
configured in a wide variety of patterns, including those
determined to maximize tool performance during specific
applications. In one aspect, the pattern of apertures, and thus the
resulting predetermined pattern of diamond particles, may be a
uniform grid. In another aspect the superabrasive particles may be
disposed in varied concentration patterns to compensate for uneven
wear. Thus, the diamond distribution for the cutting edge of a saw
may have a greater distribution of diamond particles on the lead
edge and sides than on the middle portion which is generally
subjected to less wear. Likewise, the sizes of the superabrasive
particles can be controlled to provide a cutting, grinding, etc.,
surface which is tailored to the particular uses and wear patterns
for the tool.
[0041] In another aspect of the present invention a matrix support
material may be used that consists solely, or essentially, of a
sheet of amorphous brazing alloy. As such, the superabrasive
particles can be distributed or planted in the sheet of brazing
alloy. The superabrasive embedded sheet of brazing alloy can then
be bonded directly to a tool substrate or matrix support material.
Alternatively, the superabrasive particles may be glued to a tool
substrate or matrix support material using a suitable binder. Then
the sheet of brazing alloy may then be applied to the substrate or
matrix support material, and the assembly is heated above the
melting point of the braze. Thus the molten braze can chemically
bond with the superabrasive particles and the substrate or matrix
support material. In another alternative embodiment the sheet of
brazing alloy having superabrasive particles is layered with a thin
layer of unmelted metal.
[0042] In accordance with still yet another aspect of the present
invention, the matrix support material may contain ingredients
designed to enhance certain properties. For example, hard materials
such as tungsten, tungsten carbide and silicon carbide may be added
to increase wear resistance. Soft materials, such as molybdenum
sulfide, copper, and silver, may also be added as solid
lubricants.
[0043] In a yet more detailed aspect of the present invention,
after heating the assembly of brazing alloy and abrasive particles,
a layer of overlay material may be affixed to the working surface
of the brazing alloy to create a smooth working surface. Because of
the molten state and surface tension that the brazing alloy sheet
endures during the heating process, the finally formed working
surface thereof may be quite rough, containing many jagged points
that are easily flaked off during use. This is of particular
concern during fine polishing and dressing applications where the
workpiece may be damaged as a result of loose particulates. The
overlay material has a predetermined thickness, so as not to
interfere with the polishing or dressing capabilities of the
abrasive particles. In addition, the overlay material generally
comprises any one of many metallic substances, such as nickel,
tungsten, cobalt, chromium, or a zirconium nickel alloy. The
overlay material may be applied by several methods, but in certain
aspects, may be applied by either electroplating or physical vapor
deposition (PVD) processes.
[0044] In another aspect of the present invention, a thin coating
of optional anti-corrosive material may also be applied to the
diamond tool following the brazing process. Addition of the
anti-corrosive material effectively "seals" the working surface of
the tool. Thereby protecting the abrasive particles, the brazing
alloy, and/or the overlay material from chemical attack by various
chemicals and/or coolants found in actual use of the tool. The
anti-corrosive material generally includes a super-abrasive
material, such as diamond-like carbon, or amorphous diamond.
Similar to the overlay material, the anti-corrosive layer may have
a predetermined thickness, so as effectively seal the working
surface of the tool without interfering with the performance of the
abrasive particles.
[0045] Yet another important aspect of the present invention is the
ability to specifically control the placement of various
superabrasive particles on the surface of the tool. Thus, for
example, several sheet segments may be assembled to form a tool
precursor (see FIGS. 6A through 9 and 12C) for heat and pressure
processing. Each segment is assembled by providing a thin layer of
unmelted metal and disposing superabrasive grits on the layer in a
predetermined pattern. After the diamond particles are placed onto
the thin layer of metal according to a predetermined pattern, a
sheet of amorphous brazing alloy is placed on the superabrasive
particles to form a superabrasive layer sheet segment. The process
may be repeated until a desired number of layers have been formed.
These layers are then assembled to form the desired
three-dimensional body. Subsequently the diamond tool is
consolidated (e.g., by sintering or infiltration) to form the final
product. By assembling substantially two-dimensional segments to
form a three-dimensional body, the distribution of diamond grit in
a tool can be positively controlled. Thus, diamond concentration in
different parts of the same tool may be adjusted (see FIGS. 6A
through 9). Such a control of diamond distribution is highly
desirable to improve the wear characteristics of the tool. For
example, the sides of a diamond saw blade are often worn faster
then the center, so it is advantageous to add more diamond grit on
the sides (see FIG. 6B). The layers can be of uniform distribution
pattern and concentration, or of differing distribution patterns,
concentrations and/or particle size.
[0046] By assembling layers of metal matrix having superabrasives
thereon in a predetermined pattern and concentration into a three
dimensional body, the present invention not only provides the
desirable diamond distribution pattern in the tool body, but also
provides the flexibility for possible manipulation of diamond
concentration at different parts of the same tool body. Thus, for
example, diamond particles can be disposed in denser concentrations
in some layers than others, and the layers with the greater diamond
concentrations can be disposed within the three-dimensional
structure created in such a manner as to prevent the uneven wear
patterns that are typical in many prior art abrasive tools.
[0047] Another example of the importance of improving the
performance of abrasive tools by employing a specific pattern or
design of abrasive particles is in dressing applications. As
indicated above, the use of a template allows the positioning or
placement of abrasive particles, each at specific locations in
accordance with a predetermined pattern. In one aspect, such
patterns may be designed to present specific gaps or configurations
that enhance the grooming of a CMP pad. For example, the working
surface of the CMP pad dresser may be configured to facilitate the
rising of the CMP pad under an interior, or central portion of the
dresser, rather than only along an outside or "leading edge"
thereof. Such additional rising allows the dresser to more
effectively cut into and groom the pad.
[0048] Use of the template also provides the ability to uniformly
space the abrasive particles on the substrate. Uniform spacing and
uniform size of each abrasive particle is ensured through the use
of a template as described above. Further, the use of a brazing
alloy in a sheet or cut out with an even surface, in connection
with uniformly sized abrasive particles that are adhered thereto,
allows the creation of a uniform height between the abrasive
particles.
[0049] There has thus been outlined, rather broadly, various
features of the invention so that the detailed description thereof
that follows may be better understood, and so that the present
contribution to the art may be better appreciated. Other features
of the present invention will become clearer from the following
detailed description of the invention, taken with the accompanying
claims, or may be learned by the practice of the invention.
[0050] Additional features and advantages of the invention will be
apparent from the detailed description which follows, taken in
conjunction with the accompanying drawings, which together
illustrate, by way of example, features of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0051] FIG. 1 is a side view of a final tool segment produced in
accordance with an embodiment of the present invention;
[0052] FIG. 2 is a side view of a segment showing placement of
superabrasive particles using a template;
[0053] FIG. 3 is a side view of a segment showing a method of
placing superabrasive particles on a substrate using a transfer
plate;
[0054] FIG. 4 is a side view of a segment showing an alternative
method of forming a pattern of superabrasive particles;
[0055] FIG. 5 is a side view of a precursor segment showing a
possible placement of the braze alloy;
[0056] FIG. 6A shows a segment from a super abrasive tool formed by
a plurality of linear, longitudinal layers disposed adjacent one
another to form a three-dimensional super abrasive member;
[0057] FIG. 6B shows a cross-sectional view of one typical
configuration of the tool segment shown in FIG. 6A, wherein a layer
formed by a matrix support material and a relatively large
superabrasive is sandwiched between two layers of matrix support
materials, which have smaller grit, and higher concentration of the
abrasive;
[0058] FIG. 7A shows a segment from a superabrasive tool formed by
a plurality of arcuate, longitudinal layers, which are attached to
one another to form a three-dimensional super abrasive member;
[0059] FIG. 7B shows a cross-sectional view of a plurality of
layers matrix support material as may be used with the segment
shown in FIG. 7A;
[0060] FIG. 8 shows another possible layout of a segment of a
cutting tool with transverse layers configured with a denser
concentration of abrasive material disposed at a forward, cutting
end of the three-dimensional super abrasive member;
[0061] FIG. 9 shows yet another layout of a segment wherein a
three-dimensional super abrasive member is formed with
progressively denser abrasive distribution toward the upper surface
of a tool with horizontal layers;
[0062] FIGS. 10A through 10D show one possible method for forming
layers with controlled superabrasive distribution within the
layer;
[0063] FIGS. 11A through 11C show an alternate method for forming
one or more layers with controlled superabrasive distribution;
[0064] FIGS. 12A through 12C show another alternative method for
forming one or more layers with controlled superabrasive
distribution using a sheet of amorphous brazing alloy.
[0065] FIG. 13 shows a side view of a consolidated tool segment
formed from multiple layers having a three-dimensional pattern of
superabrasives.
DETAILED DESCRIPTION
[0066] Reference will now be made to the exemplary embodiments
illustrated in the drawings, and specific language will be used
herein to describe the same. It will nevertheless be understood
that no limitation of the scope of the invention is thereby
intended. Alterations and further modifications of the inventive
features, process steps, and materials illustrated herein, and
additional applications of the principles of the inventions as
illustrated herein, which would occur to one skilled in the
relevant art and having possession of this disclosure, are to be
considered within the scope of the invention. It should also be
understood that terminology employed herein is used for the purpose
of describing particular embodiments only and is not intended to be
limiting.
[0067] A. Definitions
[0068] In describing and claiming the present invention, the
following terminology will be used.
[0069] The singular forms "a," "an," and "the" include plural
referents unless the context clearly dictates otherwise. Thus, for
example, reference to "a matrix material" includes reference to one
or more of such materials, and reference to "an alloy" includes
reference to one or more of such alloys.
[0070] As used herein, "substantially free of" refers to the lack
of an identified element or agent in a composition. Particularly,
elements that are identified as being "substantially free of" are
either completely absent from the composition, or are included only
in amounts which are small enough so as to have no measurable
effect on the composition.
[0071] As used herein, "predetermined pattern" refers to a
non-random pattern that is identified prior to construction of a
tool, and which individually places or locates each superabrasive
particle in a defined relationship with the other diamond
particles, and with the configuration of the tool. For example,
"positively planting particles in a predetermined pattern" would
refer to positioning individual particles at specific non-random
and pre-selected positions. Further, such patterns are not limited
to uniform grid patterns but may include any number of
configurations based on the intended application.
[0072] As used herein, "amorphous braze" refers to a homogenous
braze composition having a non-crystalline structure. Such alloys
contain substantially no eutectic phases that melt incongruently
when heated. Although precise alloy composition is difficult to
ensure, the amorphous brazing alloy as used herein should exhibit a
substantially congruent melting behavior over a narrow temperature
range.
[0073] As used herein, "uniform grid pattern" refers to a pattern
of diamond particles that are evenly spaced from one another in all
directions.
[0074] As used herein, "irregularly shaped" refers to a shape that
is not a standard geometric shape, e.g. shapes that are not round,
oval, square, etc.
[0075] As used herein, "matrix," "matrix support material," "matrix
support layer," and "matrix material," may be used interchangeably,
and refer to a non-sintered particulate material to which
superabrasive particles may be bonded. Notably, sintering or
consolidation of the particulate material may occur during a
process of chemically bonding superabrasive particles thereto. In
one aspect, the superabrasive particles may be bonded or fixed to a
surface of the matrix. In another aspect, the superabrasive
particles may be fixed or planted into the matrix. In yet another
aspect, the matrix material may take the shape of a tool body. In a
further aspect, the matrix material may take the shape of a sheet
having a specified thickness.
[0076] As used herein, "substrate" refers to a solid metal
material. While many solid metal materials may be a product of
metal particulate sintering or consolidation, it is to be
understood, that as used herein, "substrate" does not include
powdered or particulate metal materials that have not yet been
sintered or consolidated into a solid mass or form.
[0077] As used herein, "alloy" refers to a solid or liquid mixture
of a metal with a second material, said second material may be a
non-metal, such as carbon, a metal, or an alloy which enhances or
improves the properties of the metal.
[0078] As used herein, "metal brazing alloy," "brazing alloy,"
"braze alloy," "braze material," and "braze," may be used
interchangeably, and refer to a metal alloy which is capable of
chemically bonding to superabrasive particles, and to a matrix
support material, or substrate, so as to substantially bind the two
together. The particular braze alloy components and compositions
disclosed herein are not limited to the particular embodiment
disclosed in conjunction therewith, but may be used in any of the
embodiments of the present invention disclosed herein.
[0079] As used herein, the process of "brazing" is intended to
refer to the creation of chemical bonds between the carbon atoms of
the superabrasive particles and the braze material. Further,
"chemical bond" means a covalent bond, such as a carbide or boride
bond, rather than mechanical or weaker inter-atom attractive
forces. Thus, when "brazing" is used in connection with
superabrasive particles a true chemical bond is being formed.
However, when "brazing" is used in connection with metal to metal
bonding the term is used in the more traditional sense of a
metallurgical bond. Therefore, brazing of a superabrasive segment
to a tool body does not require the presence of a carbide
former.
[0080] As used herein, "superabrasive particles" and "superabrasive
grits" may be used interchangeably, and refer to particles of
either natural or synthetic diamond, super hard crystalline, or
polycrystalline substance, or mixture of substances and include but
are not limited to diamond, polycrystalline diamond (PCD), cubic
boron nitride (CBN), and polycrystalline cubic boron nitride
(PCBN). Further, the terms "abrasive particle," "grit," "diamond,"
"PCD," "CBN," and "PCBN," may be used interchangeably.
[0081] As used herein, in conjunction with the brazing process,
"directly" is intended to identify the formation of a chemical bond
between the superabrasive particles and the identified material
using a single brazing metal or alloy as the bonding medium.
[0082] As used herein, "precursor" refers to an assembly of
superabrasive particles, substrate or matrix support material,
and/or a braze alloy. A precursor describes such an assembly prior
to the brazing and/or sintering process, i.e. such as a "green
body".
[0083] As used herein, "aperture" refers to an opening through a
template surface which has a predetermined size and shape depending
on the intended application. For example, the aperture size may be
designed to accommodate a plurality of superabrasive particles of a
given mesh size. However, it is often desirable to design the
apertures such that only one superabrasive particle is accommodated
by each aperture.
[0084] As used herein, "euhedral" means idiomorphic, or having an
unaltered natural shape containing natural crystallographic
faces.
[0085] As used herein, "sharp portion" means any narrow apex to
which a crystal may come, including but not limited to corners,
ridges, edges, obelisks, and other protrusions.
[0086] As used herein, "metallic" means any type of metal, metal
alloy, or mixture thereof, and specifically includes but is not
limited to steel, iron, and stainless steel.
[0087] As used herein with respect to distances and sizes,
"uniform" refers to dimensions that differ by less than about 75
total micrometers.
[0088] Concentrations, amounts, and other numerical data may be
presented herein in a range format. It is to be understood that
such range format is used merely for convenience and brevity and
should be interpreted flexibly to include not only the numerical
values explicitly recited as the limits of the range, but also to
include all the individual numerical values or sub-ranges
encompassed within that range as if each numerical value and
sub-range is explicitly recited.
[0089] For example, a concentration range of about 1% w/w to about
4.5% w/w should be interpreted to include not only the explicitly
recited concentration limits of 1% w/w to about 4.5% w/w, but also
to include individual concentrations such as 2% w/w, 3% w/w, 4%
w/w, and sub-ranges such as 1% w/w to 3% w/w, 2% w/w to 4% w/w,
etc. The same principle applies to ranges reciting only one
numerical value, such as "less than about 4.5% w/w," which should
be interpreted to include all of the above-recited values and
ranges. Further, such an interpretation should apply regardless of
the breadth of the range or the characteristic being described.
[0090] B. The Invention
[0091] Reference will now be made to the drawings in which the
various elements of the present invention will be given numeral
designations and in which the invention will be discussed. It is to
be understood that the following description is only exemplary of
the principles of the present invention, and should not be viewed
as narrowing the appended claims.
[0092] Referring now to FIG. 1, a plurality of superabrasive
particles 20 are brazed to an exposed surface of substrate 102 in
accordance with a predetermined pattern. A braze material 25 is
used to braze or bond the superabrasive particles to the substrate.
In keeping with the present invention, a variety of methods may be
used to obtain the desired results and are discussed in more detail
below.
[0093] The substrate may include a variety of materials, such as
various metals. Examples of specific metals include without
limitation, cobalt, nickel, iron, copper, carbon, and their alloys
or mixtures (e.g. tungsten or its carbide, steel, stainless steel,
bronze, etc). The present invention is useful for a variety of
diamond tools such as for grinding, polishing, cutting, dressing or
any tool used to remove material from a workpiece. For example,
saws are not limited to, but may include, circular saws, straight
blades, gang saws, reciprocating saws, frame saws, wire saws,
thin-walled cutoff saws, dicing wheels, and chain saws. In another
aspect, the diamond tool may be a CMP pad conditioner.
[0094] Typically, the substrate has an exposed surface upon which
the superabrasive particles are to be affixed and may be
substantially flat or contoured and may have multiple faces, such
as in some drill bits or circular saws. However, in one embodiment
of the present invention, the superabrasives may be bonded to a
matrix support material rather than directly to a substrate. The
matrix support material may either be sufficiently configured to
act as a tool body, or may be further coupled to a substrate to
form a complete tool.
[0095] In another alternative embodiment, the abrasive particles
may be temporarily affixed to a substrate with an acrylic glue, or
other adhesive using the template as described below in order to
prevent movement during the brazing process. Most common adhesives
will vaporize at temperatures above about 400.degree. C. and do not
chemically react with the braze alloy or superabrasive
particles.
[0096] The brazing alloy of the present invention may be provided
as a thin sheet, powder, or continuous sheet of amorphous braze
alloy. There are many ways that the brazing alloy can be provided
in accordance with the present invention. For example, a brazing
alloy powder can first be mixed with a suitable binder (typically
organic) and a solvent that can dissolve the binder. This mixture
is then blended to form a slurry or dough with a proper viscosity.
In order to prevent the powder from agglomeration during the
processing, a suitable wetting agent (e.g., menhaden oil, phosphate
ester) may also be added. The slurry may then be sprayed or
otherwise applied to the matrix support material and/or
superabrasive particles. In another embodiment, the slurry can then
be poured onto a plastic tape and pulled underneath a blade or
leveling device. By adjusting the gap between the blade and the
tape, the slurry can be cast into a plate with the desired
thickness. The tape casting method is a well-known method for
making thin sheets out of powdered materials and works well with
the method of the present invention.
[0097] The brazing alloy may also be provided as a sheet of
amorphous brazing alloy. The sheet of amorphous brazing alloy may
be flexible or rigid and may be shaped based on the desired tool
contours. This sheet of brazing alloy also aids in the even
distribution of the braze over the surface of the tool. The sheet
of brazing alloy contains no powder or binder, but rather is simply
a homogenous braze composition. Amorphous brazing alloys have been
found to be advantageous for use in the present invention, as they
contain substantially no eutectic phases that melt incongruently
when heated. Although precise alloy composition is difficult to
ensure, the amorphous brazing alloy used in the present invention
should exhibit a substantially congruent melting behavior over a
relatively narrow temperature range. Thus, during the heating
portion of the brazing process the alloy does not form grains or a
crystalline phase in substantial quantities, i.e. via
vitrefication. Further, the melting behavior of the amorphous braze
alloy is distinct from sintering which requires the reduction or
elimination of voids between particles of alloy material which does
not exist in the amorphous form of the alloy. However, the
originally amorphous braze may form non-homogeneous phases during
crystallization via the slower cooling process. Generally,
amorphous alloys are formed by quickly quenching the liquid into a
solid to avoid localized crystallization and variations in
composition. Notably, in each of the processes recited herein, the
brazing alloy may be presented as either a sheet, film, or other
punched out layer that corresponds to the desired tool segment
shape.
[0098] Alternatively, a powdered brazing alloy can be mixed with a
suitable binder and its solvent to form a deformable cake. The cake
can then be extruded through a die with a slit opening. The gap in
the opening determines the thickness of the extruded plate.
Alternatively, the material can also be drawn between two rollers
with adjustable gap to form sheets with the right thickness. In
another aspect, the braze powder may be showered directly onto
diamond particles and substrate as more fully elaborated below.
[0099] It is desirable to make the sheets pliable for subsequent
treatments (e.g., bending over the tool substrate). Therefore, a
suitable organic plasticizer can also be added to provide the
desired characteristics.
[0100] The use of organic agents for powder (metal, plastics, or
ceramics) processing is documented in many textbooks and it is well
known by those skilled in the art. Typical binders include
polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyethylene
glycol (PEG), paraffin, phenolic resin, wax emulsions, and acrylic
resins. Typical binder solvents include methanol, ethanol, acetone,
trichlorethylene, toluene, etc. Typical plasticizers are
polyethylene glycol, diethyl oxalate, triethylene glycol
dihydroabietate, glycerin, octyl phthalate. The organic agents so
introduced are to facilitate the fabrication of metal layers. They
must be removed before the consolidation of metal powders. The
binder removal process (e.g., by heating in a furnace with
atmospheric control) is also well known to those skilled in the
art.
[0101] In one aspect, the brazing alloy may be substantially free
of zinc, lead, and tin. One commercially available powdered braze
alloy, which is suitable for use with the present invention, is
known by the trade name NICROBRAZ LM (7 wt % chromium, 3.1 wt %
boron, 4.5 wt % silicon, 3.0 wt % iron, a maximum of 0.06 wt %
carbon, and balance nickel), made by Wall Colmonoy Company, Madison
Heights, Mich. Other suitable alloys included copper, aluminum, and
nickel alloys containing chromium, manganese, titanium, and
silicon. In one aspect, the brazing alloy may include chromium. In
another aspect, the brazing alloy may include a mixture of copper
and manganese. In an additional aspect, the amount of chromium,
manganese, and silicon may be at least about 5 percent by weight.
In another aspect, the alloy may include a mixture of copper and
silicon. In yet another aspect, the alloy may include a mixture of
aluminum and silicon. In a further aspect, the alloy may include a
mixture of nickel and silicon. In another aspect, the alloy may
include a mixture of copper and titanium.
[0102] Preferably, the diamond braze contains at least 3% by weight
of a carbide forming member selected from the group consisting of
chromium, manganese, silicon, titanium, and aluminum, and alloys
and mixtures thereof. Additionally, the diamond braze should have a
liquidus temperature of less than 1,100.degree. C. to avoid damage
to the diamond during the brazing process. One commercially
available sheet of amorphous brazing alloy which melts at a
sufficiently low temperature is an amorphous brazing alloy foil
(MBF) manufactured by Honeywell having the NICROBRAZ LM
composition. These foil sheets are about 0.001'' thickness and
typically melt at between about 1,010.degree. C. and about
1,013.degree. C.
[0103] In one aspect, the brazing process may be carried out in a
controlled atmosphere, such as under a vacuum, typically about
10.sup.-5 torr, an inert atmosphere (e.g., argon (Ar) or nitrogen
(N.sub.2)), or a reducing atmosphere (e.g., hydrogen (H.sub.2)).
Such atmospheres may increase the infiltration of the brazing alloy
into the matrix support material, and therefore, enhance the
diamond-braze and matrix-braze bonding.
[0104] Referring now to FIG. 2, a substrate 102 is selected and a
template 110 is laid on the top of the substrate. The template 110
contains apertures 114 that are larger than one superabrasive
particle, but smaller than two abrasive particles, thereby allowing
a single particle of the abrasive to be disposed at each specific
location. The thickness of the template is preferably between 1/3
to 2/3 of the height of the average abrasive particle. However,
other thicknesses may be used if appropriate accommodations are
made for seating the abrasive particles in the desired locations.
In some aspects, the thickness of the template may be up to two (2)
times the height of the abrasive particles. An adhesive may be
applied to the surface of the substrate to hold the superabrasive
particles in place during the brazing process.
[0105] After the template 110 is properly positioned, a layer of
abrasive particles 20 is then spread over the template so that each
aperture 114 receives an abrasive particle. Those particles not
falling into the apertures in the template are removed by tilting
the substrate, sweeping the template with a broom, or some other
similar method. Optionally, a generally flat surface, such as a
steel plate, may then be laid over the superabrasive particles,
which rest in the apertures in the template. The flat surface
presses the superabrasive particles to seat the particles. The
pressed particles are therefore firmly attached to the substrate by
either slight mechanical impression into the substrate, or into a
braze layer (not shown), or adhesive layer (not shown) which was
applied to the exposed surface of the substrate prior to placing
the superabrasive particles thereon. The template 110 is then
removed such that the superabrasive particles 20 remain in place on
the substrate 102 in accordance with the predetermined pattern of
the template.
[0106] Alternatively, as shown in FIG. 3, the substrate may be a
transfer plate 106 onto which the superabrasive particles 20 are
affixed to one side using a thin adhesive film (not shown).
Optionally, the same methods as described above with regard to
using a template 110 to achieve a particular pattern of
superabrasive particles may be used to effect particle placement.
The transfer plate 106 having superabrasive particles 20 affixed
thereon is then pressed against a substrate 102. The transfer plate
may be made of metal or plastic, however it has been found that a
transparent plastic transfer plate increases ease of use and
facilitates monitoring of the process. Affixing of the particles to
the transfer plate may be accomplished using any adhering means,
such as an adhesive. In order to facilitate transfer of the
superabrasive particles to the substrate 102 an adhesive layer (not
shown) which adheres the particles 20 more strongly to the
substrate 102 than to the transfer plate can be used. The transfer
plate is then removed and treatment such as adding a braze to form
a tool precursor and heating to produce the final product may be
performed. Therefore, the abrasive particles are transferred to the
substrate in the pattern dictated by the template.
[0107] In another alternative embodiment, the transfer sheet 106
may be a sheet of amorphous brazing alloy. In a similar process to
that described above, the superabrasive particles 20 are affixed to
a substrate. First, a template 110 having apertures 114 is placed
upon a sheet of brazing alloy 106, as illustrated in FIG. 4. In one
aspect of the present invention, the sheet may be a sheet or film
of continuous amorphous brazing alloy, as described above. The use
of the template allows controlled placement of each abrasive
particle at a specific location by designing the template with
apertures in a desired pattern.
[0108] After the template 110 is place on the brazing alloy sheet,
the apertures 114 are filled with abrasive particles 20. The
apertures have a predetermined size, so that only one abrasive
particle will fit in each. Any size of abrasive particle, or grit
is acceptable, however in one aspect of the invention, the particle
sizes may be from about 100 to about 350 micrometers in diameter.
Although various aperture sizes and shapes would restrict access to
one particle per aperture, the apertures of the present invention
may be designed for very careful placement of the superabrasive
particles. Thus, for average particle sizes of 100 micrometers the
apertures could be designed about 150 micrometers across.
[0109] In another aspect of the invention, the size of the
apertures in the template may be customized in order to obtain a
pattern of abrasive particles having a size within a uniform size
range. In one particular embodiment of CMP pad dressing, the
apertures of the template are sufficient to select only grits
within a size range having a variance no greater than 50
micrometers. This uniformity of grit size contributes to the
uniformity of CMP pad dressing, as the workload of each abrasive
particle is evenly distributed. In turn, the even workload
distribution reduces the stress on individual abrasive particles,
and extends the effective life of the CMP pad dresser. In various
superabrasive tools, the template may take a wide variety of
configurations. The patterns may include various arrangements, as
well as, include multiple size apertures to accommodate differing
size superabrasive particles in the same tool in which case the
larger particles would be applied first followed by the smaller
particles.
[0110] After the apertures of the template are all filled with
superabrasive particles, any excess abrasive particles are removed,
and optionally a flat surface is applied to the abrasive particles.
The flat surface should be of an extremely strong, rigid material,
so that it is capable of pushing abrasive particles down into the
brazing alloy sheet or film 106. Such materials typically include,
but are not limited to steel, iron, alloys thereof, etc.
[0111] After removing the template, the flat surface may be used
again to press the abrasive particles firmly into the sheet of
brazing alloy. While a flat surface is preferable, those skilled in
the art will appreciate that there may be occasions when it is
desirable to have some of the abrasive particles extend outwardly
from the final tool more than other abrasive particles. In such
situations, a contoured or otherwise shaped surface could be used
to seat some of the abrasive particles deeper into the sheet of
brazing alloy, than other particles. The abrasive particles will
thus extend away from the substrate to a predetermined height.
[0112] While the method described above to press the superabrasive
particles into the brazing alloy is preferred for many
applications, there are instances where it is desirable to have the
abrasive particles extend outwardly from the sheet of brazing
alloy. For example, some tools may only have one layer of abrasive.
This can be accomplished simply by leaving the template 110 in
place when pressing the superabrasives using a flat surface, and
not further pressing the particles into the brazing alloy once the
template has been removed.
[0113] In the alternative, the sheet or film of brazing alloy in
FIGS. 3 through 5 is formed to be of a lesser thickness than the
cross-sectional thickness or diameter of the superabrasive
particles 20. When the particles are pressed into the sheet 106,
the thickness of the sheet forces the particles to protrude from
the sheet of brazing alloy. The sheet is then applied to the matrix
support material in a manner discussed above.
[0114] In creating the predetermined pattern of the present
invention, the spacing of the apertures in the template, while
non-random, need not be uniform. Rather, variations in spacing can
be provided to facilitate different concentrations on various areas
to facilitate different concentrations on various portions of the
sheet of amorphous brazing alloy. Likewise, by controlling the size
of the apertures and the order in which the diamond particles are
placed in the apertures, a single layer could be provided with
particles of different sizes.
[0115] In a more detailed aspect of the present invention,
superabrasive particle height may be important in CMP pad dresser
performance. A uniform particle height can be determined by the
thickness of the template 110, and in a preferred embodiment, each
abrasive particle will extend to within 50 micrometers of this
distance. As such, each abrasive particle grooms to substantially
the same depth on the CMP pad. However, it is to be understood that
in certain applications, grit height may not be desired to be
uniform. As such, those of ordinary skill in the art will recognize
that grit patterns of varied height may be provided by so
configuring the template, and the surface used to press the
particles to provide such a design.
[0116] Abrasive particles 20 as shown in FIGS. 1-12C are various
shapes. The scope of the present invention encompasses abrasive
particles of any shape, including euhedral, or naturally shaped
particles. However, in one embodiment, the abrasive particles have
a predetermined shape with a sharp point extending in a direction
away from the substrate.
[0117] In an alternative embodiment, rather than pressing the
abrasive particles into the sheet of brazing alloy, they may be
fixed in the templated position by disposing an adhesive on the
surface of the sheet of brazing alloy. In this manner, the
particles remain fixed in place when the template is removed, and
during heat processing.
[0118] While the use of the sheet of amorphous brazing alloy 106
been discussed with respect to the patterned distribution of
superabrasive particles, it is equally applicable to the random
distribution of diamond particles on a matrix support material.
Thus, the superabrasive particles may be distributed on either the
sheet of brazing alloy or a matrix support material without the use
of a template or otherwise creating a predetermined pattern.
Similar methods and arrangements could be employed as described
above in connection with the use of a template.
[0119] After the superabrasive particles are at least partially
embedded in, or adhered to, the sheet of brazing alloy 106, the
sheet is affixed to the substrate 102 as shown in FIG. 5.
Alternatively, in some embodiments, the sheet of brazing alloy may
be first affixed to the substrate, and the abrasive particles
subsequently added thereto using the template procedure described
herein. In another alternative embodiment, the sheet of brazing
alloy having superabrasive particles affixed thereto is applied to
the exposed surface of the substrate in such a manner that the
superabrasive particles are oriented between the sheet and the
substrate as shown in FIG. 3.
[0120] The brazing alloy used in several embodiments of the present
invention may be any brazing material known in the art, but in one
aspect, may be a nickel alloy that has a chromium content of at
least about 2% by weight. A brazing alloy of such a composition
will be nearly super hard in and of itself, and less susceptible to
chemical attack from solutions used in various applications such as
an abrasive containing slurry. In such an embodiment, additional
anti-corrosive layers or overlay material would be optional.
[0121] Because the abrasive particles are firmly held in, or on the
sheet of brazing alloy, the surface tension of the liquid brazing
alloy is insufficient to cause particle clustering during the
brazing process. Additionally, braze thickening occurs to a much
lesser degree and few or no "mounds" are formed. Rather, the braze
25 forms a slightly concave surface between each abrasive particle,
due to the wetting action of the chemical bonding between the braze
and the particles, which provides additional structural support, as
shown in FIG. 1. In one embodiment, the thickness of the sheet of
amorphous brazing alloy 106 is predetermined to allow at least
about 10% to about 90% of each abrasive particle to protrude above
the outer, or working, surface of brazing material. In another
aspect, when an overlay material is used, the abrasive particles
may be selected or placed, so that at least about 10% to about 90%
of each abrasive particle protrudes above the outer, or working,
surface of the overlay material.
[0122] In addition to the specific methods of embedding, or
adhering the abrasive particles to the sheet of brazing alloy,
those skilled in the art will recognize suitable alternative
procedures, such as fixing the abrasive particles to the substrate,
and then placing the braze thereon. In this case, the particles may
be positioned on the substrate using the template method recited
above, and held in place by glue, or other suitable binder.
Alternatively, a powdered braze material is then showered, or
placed on the substrate around the abrasive particles and heated to
cause the braze material to form chemical bonds with the
superabrasive particles and bond to the substrate.
[0123] Once the superabrasive particles and brazing alloy have been
placed on the substrate, or matrix support material, to form a
superabrasive tool precursor the precursor is heated to braze the
superabrasives to the matrix support material. The selection of the
brazing alloy is important and directly affects the final tool
properties such as durability and strength. Although many types of
brazing alloys are commercially available, the brazing alloys
useful in connection with the present invention are limited. The
brazing alloy should contain a carbide former as discussed above,
such as titanium, vanadium, chromium, zirconium, molybdenum,
tungsten, manganese, iron, silicon, aluminum, and mixtures or alloy
thereof.
[0124] Of particular importance are chromium, manganese, silicon or
alloys or mixtures thereof and have proven effective in the present
invention. The carbide former may be present in the brazing alloy
between about 2% and about 50% by weight of the brazing alloy.
Examples of these brazes are NICROBRAZ LM (Ni--Cr--B--Si--Fe),
manufactured by Wall Colmonoy Company (U.S.A.), with a melting
range of 970-1000.degree. C., and 21/80 (Cu--Mn--Ni), manufactured
by Degussa (Germany), with a melting range of 970-990.degree. C.
Other possible brazes include: Cu--Mn alloy near the eutectic
composition (about 25 wt % Mn) with a melting point of about
880.degree. C.; Ni--Si alloy near the eutectic composition (about
50 wt % Si) with a melting point of about 970.degree. C.; Cu--Si
alloy near the eutectic composition (about 30 wt % Si) with a
melting point of about 810.degree. C.; Al--Si alloy near the
eutectic composition (about 15 wt % Si) with a melting point of
about 600.degree. C.
[0125] The above-recited examples of diamond brazes cover a wide
range of mechanical properties and infiltration or sintering
temperatures (generally about 50.degree. C. above the liquidus
temperature). Various alloys of these brazes may also be used for
further adjustments of brazing temperature and mechanical
properties. The selection of diamond braze depends largely on the
intended application. In general, more severe applications, such as
sawing granite, concrete, or asphalt, would require a stronger
diamond grit that may tolerate a higher temperature of brazing.
Brazes which melt at higher temperatures are, in general, more wear
resistant. On the other hand, less demanding applications, such as
sawing limestone or marble, require lower strength diamond grit.
Such a diamond is degraded easily at high temperature so it must be
brazed at a lower temperature. Brazes of this type are typically
less wear resistant.
[0126] Brazing material should be kept to a minimum in order to
avoid completely covering the abrasive particles. This problem is
compounded by the fact that typical brazing materials are
mechanically very weak. This mechanical weakness offsets the
strength of the chemical bonds created between the abrasive
particles and the brazing material. In fact, when dislodgment
occurs, the chemical bonds between the abrasive particles and the
brazing material are strong enough that the brazing material itself
will often shear off along with detached abrasive particles. The
brazing material is also very susceptible to chemical attack by the
abrasive slurry. This contributes to the detachment of abrasive
particles, as it further weakens the brazing material, which is
already mechanically weak.
[0127] While prior art brazes typically include metals which were
designed to facilitate flow of the braze material, such as zinc,
lead and tin, it has been found in accordance with the present
invention that such materials actually impair the brazing process.
The prior art materials are generally more volatile, and have a
tendency to contaminate the vacuum or inert atmosphere used in
infiltration. While very small amounts of the volatile metals will
not significantly interfere with brazing, amounts over about 1 or 2
percent by weight can inhibit proper infiltration. As used herein,
substantially free of volatile metals, or substantially free of
zinc, etc. is used to characterize such a situation in which the
volatile metal is present in sufficiently small amounts as to not
provide any meaningful impediment to infiltration and brazing.
[0128] It is important that the brazing temperature be kept lower
than the melting point of the substrate so the tool body can
maintain the shape during the brazing of the superabrasive
particles. Moreover, the brazing temperature must also be low
enough to not cause diamond to degrade, typically less than about
1,100.degree. C. For embodiments involving infiltration, a
temperature typically 50.degree. C. above the liquidus temperature
of the braze alloy is required. In addition to control the brazing
temperature, the brazing time should also be kept short so the
braze will not react excessively with diamond or the substrate. In
the former case, diamond may also be degraded. In the later case,
the alloying with the surface of the substrate may raise the
melting point of the diamond braze. As a result, the diamond braze
may solidify gradually and eventually stop flowing. Also, a coarse
braze powder will require longer heating times and/or
temperatures.
[0129] An additional consideration in selection of a brazing alloy
is that it should also wet the superabrasive particles and
chemically bond with the superabrasives. Therefore, as the brazing
alloy 25 bonds with the superabrasive particles the alloy creeps up
the sides of the superabrasives as can be seen in FIG. 1. This
wetting action is beneficial for several reasons including improved
mechanical support for the particles, as well as the strong carbide
bonds. Typically, a carbide former contained in a suitable solvent
alloy meets this requirement. However, various carbide formers may
be adversely impacted by the brazing atmosphere.
[0130] The atmospheric environment for brazing also may be
controlled to provide superior performance. For example, if the
braze material contains a strong attractor of oxygen or nitrogen,
such as titanium, a high degree of vacuum (10.sup.-6 torr maximum),
or a dew point below -60.degree. C., must be maintained during the
brazing process. This restraint often adds unnecessary costs to
manufacturing of diamond bond tools. The presence of minute amounts
of oxygen may oxidize the carbide former and prevent the formation
of carbide bonds with the diamond. On the other hand, if the braze
material contains a less sensitive getter, such as chromium and
manganese, a lower degree of vacuum (10.sup.-5 torr minimum) or a
hydrogen atmosphere may be adequate for brazing. However, if the
carbide former reactivity is too low, such as with cobalt or
nickel, minimal carbide bonds will be formed with the diamond
particles. Hence there is a compromise in selection of carbide
formers between the ability to bond with diamond and the tendency
to oxidize.
[0131] After brazing, the produced part (e.g., a saw segment) may
be trimmed (e.g., by grinding) to the finished dimension. It can
then be mounted (e.g., by conventional brazing) onto a tool body
(e.g., a round steel blade) to make a finished product.
[0132] As discussed above, this invention uses a diamond braze that
wets the matrix support material of a diamond tool. Most diamond
brazes can wet easily common matrix support materials with major
constituents of cobalt, nickel, iron, copper or bronze, so the
brazing may proceed smoothly. Referring again to FIG. 1, typically,
the final diamond tool produced in accordance with the method of
the present invention includes diamond particles 20 having carbide
bonds with a component of the braze alloy, such as chromium, and a
braze 25 containing various eutectic phases which includes both
mechanical brazing and partial alloying with the substrate 102.
[0133] In addition to brazing using the methods described above,
the bonding of the diamond particles to the matrix material using
the brazing alloy may be accomplished by mixing a powdered form of
brazing alloy with a powdered form of matrix material. The organic
binder is then added, and the matrix support material and brazing
alloy are formed into a sheet, or layer as described above. Diamond
particles are then distributed by being positioned or located in a
predetermined pattern using a template as described. The sheet may
then be stamped, or pressed into desired tool shapes, which are
heated to a temperature sufficient to bond the diamond particles to
the matrix support material using the brazing alloy, as well as to
sinter together the metal particles of the matrix. Such a process
generally may be accomplished using low temperatures which do not
incur many of the afore-wamed risks to the tool.
[0134] The most widely used matrix powder for making diamond tools
(e.g., saw segments) is cobalt powder. The standard sizes of cobalt
powder for making conventional diamond tools are less than 2
micrometers. In the last decade, the diamond tool manufacturers
have demanded finer and finer matrix powders. The commercial
suppliers (e.g., Eurotungsten Co.) are therefore, moving toward
making ultrafine (one micrometer), and even ultra-ultrafine
(submicron) powders. With such a trend, the sintering temperature
is continuously decreasing. A lower sintering temperature not only
reduces the degradation of diamond; it also reduces the cost of
manufacturing. For example, the powder consumption is lower.
Moreover, the oxidation loss of graphite mold is also
minimized.
[0135] However, one embodiment of the present invention uses a
diamond braze to fill up the pores of the matrix powder. Hence,
coarse-sized powders, i.e. greater than 400 U.S. mesh or 34
microns, are preferred. Moreover, while conventional methods
require the density be as high as possible so sintering can proceed
rapidly, it is preferred in the present invention to use a
precursor with a lower packing density to allow the easy flow of
the diamond braze. In fact, sometimes, the porosity of the
precursor body may be intentionally increased by using irregularly
shaped matrix particles. This preference, again, is contrary to the
conventional wisdom that requires the particles be as spherical as
possible so the packing density can be increased.
[0136] The use of a coarse matrix powder has other benefits. For
example, a coarse powder can mix better with different
compositions. Hence, the diamond grit may distribute more uniformly
in the matrix. Moreover, a coarse powder has a smaller surface
area, and hence, a lower frictional force for infiltration.
Therefore, it can flow easier in the mold. Of course, a coarse
matrix powder is also much less expensive, so the production cost
may be reduced.
[0137] It is important to note that this invention utilizes the
matrix merely as the network for holding the diamond grit in place.
Hence, the matrix may not have to be made of powder. For example,
the matrix body may be made of a piece of steel with openings that
contain diamond grits of PCD bodies. Further, the superabrasive
containing segments may be easily formed to accommodate a variety
of substrate shapes prior to brazing.
[0138] In another alternative embodiment of the present invention,
a three-dimensional tool is formed having a predetermined pattern
of diamond grits therein. By assembling substantially
two-dimensional segments to form a three-dimensional body, the
distribution of diamond grit in a tool can be positively
controlled. Thus, diamond concentration in different parts of the
same tool may be adjusted (see FIGS. 6A through 9). Such a control
of diamond distribution is highly desirable to improve the wear
characteristics of the tool. For example, the sides of a diamond
saw blade are often worn faster then the center, so it is
advantageous to add more diamond grit on the sides (see FIG.
6B).
[0139] Referring to FIG. 6A, there is shown a perspective view of a
tool segment, generally indicated at 10, formed by a plurality of
layers, 14, 16 and 18. Each of the layers 14, 16 and 18 is formed
by matrix support material impregnated with diamond particles,
indicated by the dark circles 20, and has been infiltrated with a
braze selected to chemically bond to the diamond particles and the
matrix support material, such bonding firmly holds the particles in
the matrix support material. Preferably, the diamond particles 20
constitute less than 50 percent of the matrix support
material-diamond mixture, and more preferably less than 40 percent.
Keeping the amount of diamond particles to the minimum helps to
minimize cost while optimizing the useful life of the product.
Although FIGS. 6A through 9 show discrete layers of matrix support
material, the final sintered tool segment is essentially a
continuous metal matrix having superabrasive particles distributed
in a particular three-dimensional pattern. Thus, the layers meld to
form an essentially seamless unitary matrix having superabrasive
particles therein. This continuous melded matrix improves the
strength and durability of the final multi-layered tool.
[0140] As discussed in U.S. Pat. No. 6,159,286, which is
incorporated herein, forming the segment 10 in a plurality of thin
layers provides remarkably improved control over the distribution
of the diamond particles 20. By controlling the distribution of the
diamond particles 20 within each layer and then combining layers, a
three-dimensional segment can be formed in which distribution of
the diamond particles is controlled in each dimension. This, in
turn, enables the formation of segments, which are particularly
adapted to the likely use of the segment, be it for polishing,
cutting, grinding, etc. By tailoring the distribution and
concentration of the super abrasive particles within the segment
10, more precise control is given over performance of the tool
under actual working conditions.
[0141] For example, when using a diamond saw blade to cut rocks
(e.g., granite), the two sides of the diamond saw segments are
cutting more materials than the center. As a result of uneven wear,
the cross section of the saw segment becomes convex in shape with
the center bulging above both sides. This configuration typically
slows the cutting rate of the saw blade. Moreover, the protruding
profile may also cause the saw blade to deflect sideways in the cut
slot. In order to maintain a straight cutting path, it is sometimes
desirable to make a "sandwich diamond segment" to reinforce both
sides of the segment with layers impregnated with more diamond or
superabrasive grits. Such a "sandwich segment" is difficult to
manufacture by mixing diamond grit with metal powder by
conventional means, but it can be easily accomplished by methods of
the present invention: first planting diamond grits with desirable
patterns and concentrations in a metal matrix layer and then
assembling these metal matrix layers with diamond grits impregnated
in the predetermined patterns and concentrations together to form a
sandwiched segment.
[0142] The present invention further improves the above technique
by infiltrating the matrix support material with a braze which is
selected to chemically bond to the diamond particles and to the
matrix support material. Thus, while the placement of the diamond
particles shown in FIG. 6A is a marked improvement over the prior
art, an additional increase in the useful life of segment 10 is
obtained by utilizing a braze to form a chemical bond, rather than
merely relying on mechanical retention of the diamond
particles.
[0143] Likewise, the selective placement of differing sizes of
diamond particles can used to form a cutting segment formed to
resist premature wear to the sides of the segment, thereby
extending the cutting segment's useful life. Referring specifically
to FIG. 6B, there is shown a cross-sectional view of the cutting
segment 10 of FIG. 6A. Unlike the cutting segments of the prior
art, the cutting segment 10 is formed of three layers, 14, 16 and
18 respectively. The middle layer 16 has a plurality of super
abrasive particles 20a, which are of a first size (e.g. 40/50 mesh)
and a first concentration. The outer layers 14 and 18, in contrast,
have a plurality of super abrasive particles 20b, which are of a
second size (e.g. 50/60 mesh) smaller than the first size, and in a
second concentration greater than that present in the middle layer
16. The smaller, more densely distributed super abrasive particles
20b provide the outer layers 14 and 18 with a greater resistance to
wear as they cut through concrete, rock, asphalt, etc. Because the
outer layers 14 and 18 are more resistant to wear, the cutting
segment 10 resists formation of a convex outer surface, as has
traditionally occurred with cutting elements. By maintaining a more
planar cutting surface, the cutting segment is able to maintain a
straight cutting path so it can cut more efficiently with a longer
useful life. Moreover, by using a smaller grit on the flank of the
saw, the finish of the cut surface is smoother and chipping of the
workpiece can be avoided.
[0144] Furthermore, an additional increase in useful life is
obtained by infiltrating the matrix support material with a braze
formed from chromium, manganese, silicon, titanium, and/or
aluminum, or an alloy or mixture thereof. While a wide variety of
quantities of these materials may be used, it has been found that
it is preferable if the chromium, manganese, silicon, titanium, or
aluminum or alloy or mixture in the diamond braze constitutes at
least 3 percent of the braze by weight (and more preferably 5
percent). The braze fills the pores in the matrix support material,
which is typically powder selected from the group including iron,
cobalt, nickel or alloys or mixtures thereof.
[0145] Another advantage to the use of multiple layers of matrix
with diamond or some other super abrasive particle disposed therein
is that the layers are easily formed into other desirable shapes
for the cutting, drilling, grinding, etc., segment. For example,
FIG. 7A shows a perspective view of a segment, generally indicate
at 30, of a super abrasive tool formed by a plurality of arcuate,
longitudinal layers of matrix support material which are attached
to one another to form a three-dimensional super abrasive member
which has been infiltrated with the braze to thereby hold the
diamond within the matrix material of the member. The segment 30 is
formed from first, second and third layers, 34, 36 and 38, which
are each arcuate. When the three are joined together, an arcuate
segment 30 is created. Such a segment, of course, may be used on
cutting tools, which are non linear, and on other types of tools
for which a nonlinear superabrasive segment is desired. Because the
layers 34, 36 and 38 are initially formed independent of one
another, they are much easier to conform to a desired shape, and
are able to do so while the brazed diamond particles 20 disposed
therein are held in their predetermined positions.
[0146] Each of the layers is impregnated with a plurality of
superabrasive particles 20, typically diamond or cubic boron
nitride. Because each layer is a relatively thin layer of metal
matrix, (i.e., the metal matrix will usually be no more than two
times the thickness of the diameter of the particles), superior
control over placement of the superabrasive particles in the metal
matrix layer can be easily achieved. As discussed above, the random
placement of superabrasives in abrasive tools in the current art
often lead to ineffective use of superabrasive particles. By
controlling distribution of superabrasives the present invention
enables either even distribution which prevents under or over
spacing, or controlled distribution so that different portions of
the segment have different sizes and concentrations which are
matched to prevent traditional wear patterns.
[0147] Referring now to FIG. 7B, there is shown a cross-sectional
view of a plurality of the layers 34, 36 and 38 of the segment 30.
Of course, the configuration of the diamond particles may be used
with the segment shown in FIG. 6A or that shown in FIG. 7A. Unlike
the embodiment of FIG. 6B, the layers are each provided with the
same size and concentration of the diamond particles 20. However,
because the spacing is substantially uniform, there is no under
spacing or over spacing between the superabrasive particles, and
the segment 30 wears more evenly than the segments of the prior art
with randomly spaced particles. The more even wear prevents
premature failure of the segment 30, and thus extends the life of
the tool while keeping the amount of superabrasive used to a
minimum. Furthermore, the braze which bonds to the diamond
particles and the matrix further strengthens each layer and
prevents loss of the diamond particles.
[0148] FIG. 8 shows another possible embodiment of a segment 50
made in accordance with the teachings of the present invention. The
layered structure in a diamond segment may also be assembled
transversely or horizontally, and the braze may be applied to every
layer, or to select layers as shown in FIG. 8. Thus, the segment 50
in FIG. 8 is formed from a plurality of transverse layers,
generally indicated at 54. A first plurality of the layers (i.e.
the first four layers), indicated at 56, are provided with a first
concentration of diamond particles 20 which are brazed to bond to
the matrix support material. A second plurality of layers (i.e. the
remaining 9 layers), indicated at 58, are provided with a second
concentration, less than the first concentration and are also
brazed to bond to the matrix support material.
[0149] Many cutting tools are configured such that the cutting
segment 50 is provided with a lead edge which performs a majority
of the cutting and which receives most of the impact force when
contacting the surface to be cut. For example, a circular saw blade
will usually have a plurality of teeth or segments, each tooth
having a leading edge, which takes the force of the cutting.
Because the leading edge performs a significant portion of the
cutting, it is much more susceptible to wear than are rotationally
rearward portions of the tooth. When formed in accordance with the
prior art, the teeth, however, often had relatively consistent
abrasive disposed thereon. Over time the leading edge wears
significantly, but the other portions coated with diamond particles
are subjected to minimal wear. Eventually, the abrasive is worn off
the leading edge, while significant amounts remain on the other
portions of each tooth. Thus, a considerable amount of super
abrasive is wasted when the blade is discarded. The embodiment of
FIG. 8 is specifically configured to overcome such concerns. The
layers 56 and 58 are configured to provide substantially even wear
across the cutting segment 50 by placing a larger percentage of the
diamond particles 20 near the leading edge 56, than on rotationally
distal portions 58. Thus, by the time the leading edge has reached
the end of its useful life, the remaining portions of the cutting
segment 50 have also been worn out. Such controlled distribution of
the superabrasive particles 20 decreases the use of the expensive
material and lowers the cost for making the cutting segment 50
without hurting performance. Additionally, by providing more ever
wear, the cutting segment 50 will often be able to maintain most of
its cutting speed until shortly before the end of its useful life.
Additionally, brazing the diamond particles 20 in layers 56 and 58
further extends tool life.
[0150] FIG. 9 shows yet another layout of a segment wherein a
three-dimensional super abrasive member is formed with
progressively denser abrasive distribution toward the upper surface
of a tool with horizontal layers. As with the embodiment of FIG. 8,
the controlled distribution of the diamond particles 20 forms an
improved abrasive segment 70, while at the same time decreasing the
cost of abrasive tools by decreasing the unnecessary consumption of
diamond particles. Additionally, brazing may be used on some of the
layers, while being omitted from other layers, to thereby customize
the abrasive segment 70.
[0151] With routine experimentation and the teachings of the method
of the present invention, those skilled in the art will be able to
customize cutting, drilling, grinding, polishing and other types of
abrasive segments which are specifically formed to maximize their
abrasive ability (i.e. cutting, drilling, grinding, etc.) over an
extended useful life, while simultaneously decreasing the amount of
super abrasive which is used to form the tool in accordance with
the principles of the method of the present invention.
[0152] Referring now to FIGS. 10A through 10D, there is shown one
method for forming layers in accordance with the principles of the
present invention. Many of the same principles may be applied with
respect to the formation of layered segments as to the formation of
segments described in connection with FIGS. 1 through 5 above. The
first step of the method is to form a sheet 100 of matrix support
material 104 which will be bonded to the super abrasive particles
20. The sheet 100 of matrix support material 104 can be formed from
conventional powders such as cobalt, nickel, iron, copper, bronze,
or any other suitable bonding agents. Additionally, for reasons,
which are discussed in detail below, it is highly advantageous to
use coarse powders, such as those above 34 microns (400 mesh) in
diameter. While the use of coarse powders is inconsistent with the
current teachings that it is desirable to use the finest powder
available, considerable benefits may be achieved by combining
course powder and braze to secure diamond particles in place.
[0153] Once the sheet 100 of matrix support material 104 is formed,
a template 110 is laid on the top of the sheet as shown in FIG.
10A. The template 110 contains apertures 114 that are larger than
one abrasive particle 20, but smaller than two abrasive particles,
thereby allowing a single particle of the abrasive to be disposed
at each specific location. The thickness of the template is
preferably between 1/3 to 2/3 of the height of the average abrasive
particle 20. However, other thicknesses may be used if appropriate
accommodations are made for seating the abrasive particles in the
desired locations.
[0154] After the template 110 is properly positioned, a layer of
abrasive particles 20 is then spread over the template so that each
aperture 114 receives an abrasive particle. Those particles not
falling into the apertures 114 in the template 110 are removed by
tilting the substrate, sweeping the template with a broom, or some
other similar method.
[0155] As shown in FIG. 10B, a generally flat surface 120, such as
a steel plate, is then laid over the particles 20, which rest in
the apertures 114 in the template 110. The flat surface 120 presses
the abrasive particles 20 at least partially into the pliable sheet
100 of matrix support material 104 to seat the particles.
[0156] After removing the template 110, the flat surface 120 is
used again to press the abrasive particles 120 firmly into the
sheet 100 of matrix support material 104 as shown in FIG. 10C.
While the flat surface 120 is preferable, those skilled in the art
will appreciate that there may be occasions when it is desirable to
have some of the abrasive particles 20 extend outwardly from the
sheet 100 of matrix support material more that other abrasive
particles. In such situations, a contoured or otherwise shaped
surface could be used to seat some of the abrasive particles 20
deeper into the sheet 100 of matrix support material 104, than
other particles.
[0157] The sheets 100 may be first assembled to form the precursor
of the tool segment and then hardened and finished using the
infiltration and sintering techniques set forth above, or they can
be hardened and finished individually, and subsequently assembled
and combined to form the tool segment or the entire tool body where
appropriate. Typically, the assembly of the sheets 100 is
accomplished by a known method such as cold compaction with a
press. The "green" body so formed can then be consolidated to form
a final tool product by sintering or infiltration as described
above.
[0158] If desired, the process shown in FIGS. 10A through 10C can
be repeated on the other side of the sheet 100 of matrix support
material 104 (as shown in FIG. 10D), to form an impregnated layer
having diamond particles 20 distributed throughout the layer in
some predetermined, desired pattern. The process is typically
repeated several times to obtain multiple thin layers or sheets
100, which are impregnated with the diamond particles 20. Of
course, each sheet 100 need not have the same distribution pattern
for the diamond particles 20, nor need the concentration of the
abrasive particles be the same in each sheet.
[0159] While the method described in FIGS. 10A through 10D is
preferred for many applications, there are instances where it is
desirable to have the abrasive particles 20 extend outwardly from
the sheet 100 of matrix support material. For example, some tools
may only have one layer of abrasive. This can be accomplished
simply by leaving the template 110 in place when performing the
steps shown in FIG. 10A and 10B, and not further pressing the
particles 20 into the matrix support material once the template has
been removed.
[0160] In the alternative, FIGS. 11A through 11C show a side view
of an alternate to the method discussed in FIGS. 10A through 10D.
The sheet 130 of matrix support material 134 in FIGS. 11A through
11C is formed to be of a lesser thickness than the cross-sectional
thickness or diameter or the superabrasive particles 20. When the
particles are pressed into the sheet 130, the thickness of the
sheet forces the superabrasive particles 20 to protrude from the
matrix support material 134. The sheet 130 is then infiltrated with
diamond braze in the manner discussed above.
[0161] While the spacing of apertures of the template shown in
FIGS. 11A through 11C is generally uniform, according to one aspect
of the invention, such spacing need not be uniform, and can be
according to any desired pattern. As such, variations in spacing
can be provided to facilitate different concentrations on various
portions to facilitate different concentrations on various portions
of the sheet 130 of matrix material 134. Likewise, by controlling
the size of the apertures and the order in which the diamond
particles are placed in the apertures, a single layer could be
provided with particles of different sizes.
[0162] In yet another alternative, FIGS. 12A through 12C show a
side view of a method of forming superabrasive containing layers
using sheets of amorphous braze alloy. Again, in a similar manner
as previously discussed, FIG. 12A shows a template 110 having a
plurality of apertures 114 arranged in a predetermined pattern,
which is placed on a thin substrate or sheet of matrix support
material 107. The superabrasive particles 20 are then placed in the
apertures and fixed in position with an adhesive or the like. As
before, the flat surface may be contoured to accommodate various
tool configurations. The template 114 may then be removed. A sheet
of amorphous brazing alloy 106 is then placed over the
superabrasive particles 20 as shown in FIG. 12B to form a single
layer segment 15. In an alternative embodiment, the sheet of
amorphous brazing alloy 106 may be placed on the substrate or
matrix support material layer prior to placement of the
superabrasive particles thereon.
[0163] Several single layer segments 15 may then be formed and
combined into a single multi-layered precursor 18, or green body,
as shown in FIG. 12C. The single layer segments 15 may be secured
using an adhesive as in the discussion of FIGS. 6A through 6D or
brazed using a traditional (i.e. does not necessarily contain a
carbide former) brazing alloy. This precursor may be formed of
layers of uniform distribution of superabrasive grits similar to
FIG. 7B or of varying configurations, concentrations and/or
particle size as in FIG. 6B. The method of the present invention
includes configurations in which some of the layers are void of
superabrasive particles altogether. Further, the matrix support
material 107 may be a layer of metal or an unsintered metal powder
as described above. The resulting tool segment would have different
properties depending on which type of support material is
chosen.
[0164] The precursor 18 is then placed in a vacuum furnace and
heated to a sufficient temperature to cause the sheet of amorphous
braze alloy 106 to melt and bond to the superabrasive particles 20
and to the layer of metal 107 to form a melded multi-layered tool
having the desired pattern of superabrasive particles distributed
throughout as shown in FIG. 13. FIG. 13 shows a consolidated
superabrasive tool segment 19 wherein the superabrasive particles
20 are arranged in a predetermined three-dimensional pattern. The
areas identified by 108 and 109 illustrate generally the layers of
metal and braze alloy, respectively. The dotted lines are for
illustrative purposes only and those skilled in the art will
recognize that the actual final tool segment may differ. For
example, if the sheet of braze alloy is thinner than the diameter
of the particles and the metal layer is solid during the
consolidation process the final tool may have empty voids between
particles. Further, if the layer of metal is formed of unsintered
powder the consolidation process will cause the final tool to be
much more homogenous due to infiltration of the brazing alloy
throughout the metal powder. The thickness of the layer of metal
107 and the sheet of braze alloy 106 may be of varying thickness.
The thickness of the layer of metal 107 and/or the sheet of brazing
alloy may be less than the diameter of the superabrasive particles
20, as shown in FIG. 12A or either may be thicker than the diameter
of the superabrasive particles used.
[0165] During the heating process the precursor assembly is heated
to just over the liquidus temperature to allow the braze alloy to
flow somewhat. Maintaining the braze alloy, and the matrix or metal
layer, near the liquidus temperature helps to prevent substantial
movement of the particles from their intended positions. Typically,
a temperature of about 5.degree. C. above the liquidus temperature
over a relatively short period of time, about 10 to about 20
minutes, is sufficient to obtain the desired results.
EXAMPLES
Example 1
[0166] 40/50 mesh diamond grit (SDA-85+ made by De Beers Company)
were mixed with iron powders and an organic binder to form a
mixture with diamond concentration of 20 (5% of total value). The
mixture was cold pressed in a steel mold to form the shape of a saw
segment. The precursor was placed in a graphite mold and overlaid
with a powder of Nicrobraz LM. The mold was heated under vacuum to
about 1,050.degree. C. for 20 minutes. The infiltrated braze had
bonded diamond and matrix powder together for form a segment.
Twenty-four of such segments were manufactured and they were
trimmed to desirable tolerances. These segments were brazed onto a
14-inch round steel circular saw blade. The blade was used to cut
granite at a faster cutting rate than was possible with
conventional diamond saw blades. Additionally, the brazed saw
blades had a longer useful life than a conventional diamond saw
blade.
Example 2
[0167] 40/50 mesh diamond grit (SDA-85.sup.+ made by De Beers
Company) were mixed with metal powder to form a mixture with a
diamond concentration of 20 (5% of total volume). Five different
proportions of cobalt (about 1.5 micrometer in size) and bronze
(about 20 micrometers in size) were used for the matrix powder. An
acrylic binder was added (8% by weight) to the mixture and the
charge was blended to form a cake. The cake was then rolled between
two stainless steel rollers to form sheets with a thickness of 1
mm. These sheets were cut in the shape of saw segments with a
length of 40 mm and width of 15 mm. Three each of such segments
were assembled and placed into a typical graphite mold for making
conventional diamond saw segments. The assembled segments were
pressed and heated by passing electric current through the graphite
mold. After sintering for three minutes, the segments were
consolidated to a height of 9 mm with less then 1% porosity.
Twenty-four segments for each composition were fabricated. They
were brazed onto a circular saw of 14 inches in diameter. These
five blades were used for cutting granites and found to perform
equal or better than those with higher diamond concentrations (e.g.
23) made by conventional methods. Microscopic examination of the
wom segment indicated that although diamond particles were not
planted into the layered matrix, they were distributed more evenly
than segments prepared by the traditional method. The segregation
of particles in a layered matrix was considerably less than that in
the thick body of conventional segments.
Example 3
[0168] The same procedures were followed as Example 2, but with 8
thinner layers (0.4 mm) for each segment. The diamond concentration
was reduced to 15 and particles were positively planted according
to the illustration as shown in FIGS. 10A through 10D. The diamond
distribution was much improved. As a result, the performance of
these blades were equal or better than those made by conventional
methods with diamond concentration of 20.
Example 4
[0169] Iron powders of about 100 mesh were mixed with an S-binder
made by Wall Colmonoy Company to form a cake. The cake was then
rolled to form sheets of 0.4 mm in thickness. 40/50 mesh
SDA-100.sup.+ diamond grit was positively planted into these sheets
to attain a concentration of 15. These diamond containing sheets
were cut in the shape of saw segments with a length of 40 mm and
width of 9 mm. Eight of such segments were assembled as a group and
placed in a graphite mold. Twenty-four groups were placed
horizontally, and another twenty-four groups were placed vertically
in the graphite mold. Nicrobraz LM powder (-140 mesh) (made by Wall
Colmonoy Company) was added on the top of these segments. These
samples were heated in a vacuum furnace (10.sup.-5 torr) to
1050.degree. C. for 20 minutes for horizontally placed segments,
and 30 minutes for vertically placed segments. The melted LM alloy
(Ni--Cr--B--Si with a liquidus point at 1000.degree. C.)
infiltrated into these segments and filled the porosity. The excess
LM braze on these segments were ground by electrode discharge
(EDG). Each of the 24 segments so fabricated were brazed onto a 14
inch (diameter) circular saw blade. These blades were used to cut
granite and showed marked improvement over conventional saw
blades.
Example 5
[0170] Nicrobraz LM powder was mixed with an acrylic binder and
rolled to form layers of about 0.25 mm. 40/50 mesh MBS-960 diamond
grit manufactured by General Electric Company was positively
planted into these metal layers according to the method as
illustrated in FIGS. 10A through 10D. These diamond planted metal
layers were cut in proper size and wrapped around 2,000 beads
(pearls) of wire saw. These beads (10 mm in diameter by 10 mm long)
were divided into two groups; one contains 280 crystals (about 0.2
carat). These beads were heated in a vacuum furnace to a
temperature of 1,000.degree. C. for 8 minutes. These beads were
mounted on several wire saws and were used to cut marble,
serpentine and granite. The performance of these beads was found to
be superior to conventional beads. The latter beads were typically
made by either hot pressing or electroplating. These conventional
beads may contain a much higher amount of diamond (up to 1 carat)
per bead.
Example 6
[0171] The same method as described by Example 5, but applied to
other products, e.g., circular saws, thin-wall core bits, and
curvature grounder. Each of these products shows superior
performance over conventional electro-plated diamond tools having
similar superabrasive concentrations.
Example 7
[0172] Mixture of metal powders that contain 87 wt % of -40 mesh
Nicrobraz LM (made by Wall Colmonoy, U.S.), 8 wt % of iron of -125
mesh, and 5 wt % of copper of -60 mesh were mixed with 3 wt % of an
acrylic binder to form a dough. The dough is rolled between two
rollers to form sheets of 0.6 mm thick. Each sheet is cut to shape
and covered with a template. 30/40 mesh (0.420 to 0.595 mm) diamond
grits of SDA-100+ grade (made by De Beers, South Africa) were
positively planted into the metal layers in a predetermined pattern
with a diamond-to-diamond distance of about 2 mm. Three layers were
stacked together and wrapped around a steel sleeve to form a
diamond bead of 10 mm in diameter and 10 mm in length. These beads
were heated in a vacuum furnace to consolidate the metal and also
braze the diamond in place and onto the steel sleeve. 1,000 of such
diamond beads were fitted over 5 mm steel cable that contained
7.times.19 wires, and they are spaced by plastic coating formed by
injection molding. The wire was 25 meters long and it was joined
end-to-end to form a loop. This wire saw was used to cut granite
blocks (3.5 meter long by 1.8 meter high) of all grades. The life
achieved was 0.5 square meter cut surface per diamond bead consumed
(0.5 carat). This area cut is twice of that cut by conventional
diamond beads made by a powder metallurgical method.
Example 8
[0173] This is the same as example 7, except many diamond
impregnated layers were assembled to form a block of 20 mm long by
5 mm thick by 7 mm high. These blocks were consolidated in a vacuum
furnace to form diamond segments. Each segment contained about 8
volume percent diamond. 30 of such segments were brazed onto a 4
meter long steel frame and the fame was mounted on a reciprocating
sawing machine. The saw was used to cut marble blocks with a life
more than twice longer than conventional diamond segments produced
by powder metallurgical methods.
Example 9
[0174] This is the same as example 8, except the diamond planted
layers were assembled to form segments of about 24 mm long by 3.5
mm thick for a core bits of 150 mm in diameter. The diamond content
in these segments was about 4 V %. 10 of such core bits were used
to drill concrete. The drilling speed and the life of these core
bits were much higher than conventional diamond segments made by
powder metallurgical methods.
Example 10
[0175] This is the same as example 9, except the shape of segments
is for circular saws. These segments were brazed to make circular
saws of 230 mm (with 18 segments of 40 mm by 8.5 mm by 2.4 mm), 300
mm (with 21 segments of 50 mm by 8.5 mm by 2.8 mm), and 350 mm
(with 24 segments of 50 mm by 8.5 mm by 3.2 mm) in diameter. These
saws were used to cut granite, asphalt, and concrete with superior
performance.
Example 11
[0176] This is the same as Example 8, except the segments are used
as dressers for conditioning grinding wheels.
Example 12
[0177] A single layer of 14/16 mesh (1.4 mm to 1.2 mm in size)
diamond grits (natural diamond EMB-S made by De Beers) positively
planted sheet is covered over a pellet of 20 mm diameter by 8 mm
thickness. Many of these pallets were brazed in a vacuum furnace.
More than 3000 of such pallets were mounted on floor grinding
machines to grind stone and wood floors. The results indicate that
the grinding speed could be three times faster than conventional
diamond grinders.
Example 13
[0178] A single layer that contained positively planted diamond
grits of 40/50 mesh (0.420-0.297 mm size) ISD 1700 grade (made by
Iljin Diamond of Korea) was laid over the curved surface of a
profile wheel and brazed to form a rigid tool in a vacuum furnace.
More than 100 of such profile wheels of various diameters were used
to form the edges of granite and marble slabs. These profile wheels
were capable to cut more than 3 times faster than conventional
diamond tools made by either electroplating or sintering
method.
Example 14
[0179] This is the same as example 13, except that the diamond
planted layer is wrapped around a steel sleeve to form a single
layered diamond beads. More than 100,000 of such beads were
manufactured. They were used to cut granite or marble with superior
performance.
Example 15
[0180] This is the same as example 12, except the diamond grits
were 80/100 mesh, and the diamond planted layer was used to cover
the surface of a flat disk of 4 inches in diameter. 4 such disks
were produced and used as conditioner to dress the CMP (chemical
and mechanical polishing) pad that polished silicon wafers. The
result indicated that the CMP efficiency was much improved and the
conditioner outlasted conventional conditioners made by either
electroplating or brazing.
Example 16
[0181] Wall Colmonoy's Nicrobraz LM powder is used as the braze. It
is mixed with either iron powder (Fe), copper powder (Cu), or both
in various proportions (the following refer to the weight
percentage of the overall mixture): 90LM/10SiC; 90LM/10WC; 100LM;
92LM/8Fe; 90LM/10Cu; 82LM/8Fe/10Cu; 80LM/20Cu; 72LM/8Fe/20Cu;
70LM/30Cu; and 60LM/40Cu. The mixture also contains 4 weight
percent of an acrylic binder that is used to glue all powder
together. The mixture is cold pressed to form a sheet and heated to
400.degree. C. for 30 minutes in air to bum out most of the organic
binder. The preform is then placed in a vacuum oven maintained at a
pressure of 10.sup.-5 torr. Heating is applied to a temperature of
1010.degree. C. for 12 minutes. After the LM was completely melted
and it infiltrated (or metal sintered by the aid of molten LM) the
solid metal powder the consolidated mass is cooled. After cooling
the consolidated mass is taken out of the oven and tested for
hardness and abrasion resistance. It was discovered that the HRB
hardness for these compositions are 140, 130, 120, 118, 116, 110,
108, 100, 100, and 70, respectively. The abrasion resistance is
decreases in the same order.
[0182] The hardness or abrasion resistance is important, as it must
match the wear rate of diamonds in a tool so the grit can be
exposed to the proper height for cutting a work piece efficiently.
When an abrasive material, such as diamond particles, is bonded to
a soft matrix it may become over exposed. As a result, the abrasive
material may be shattered or dislodged during the cutting action
thus reducing the tool life.
[0183] It has been determined based on these experiments that
diamond bonded on a 92LM/8Fe matrix is most suitable to cut hard
materials such as concrete, granite, and sandstone. A 80LM/20Cu
matrix is more suitable to cut softer materials such as limestone
and marble.
[0184] Diamond grits of 30/40 mesh (SDA-100+ of De Beers Company)
were mixed with an 80LM/20Cu matrix. Various cutting tools
containing 30 concentration diamonds (about 8 volume percent) were
produced. Tools included circular saw segments, gang saw segments,
and wire saw beads which were then brazed to circular saw blades,
reciprocatively cutting gang saw blades, and steel cables
respectively. Although somewhat random, these tools were used to
saw a variety of rocks with long lives and high cutting rates.
Example 17
[0185] This is an example of sintering solid braze powder together
without the melting step. LM powder was mixed with either Fe, Cu,
or both in various proportions and an acrylic binder (4 weight
percent) to form a dough. The dough is then rolled using steel
rollers to form sheets 1 mm thick. 30/40 (18 concentration) and
40/50 (22 concentration) diamond grits of SDA-100+ were positively
planted into these sheets using a template that contained holes of
proper size in fixed positions. These sheets were cut to a size of
40 mm long by 8 mm wide. Five of these cut sheets were stacked
together with three center layers that contained 30/40 mesh
diamond. The assembly was hot pressed in a graphite mold at 400 atm
and 900.degree. C. After cooling, the segments were brazed onto
circular steel blades. The blades with matrices containing
80LM/20Cu and 80LM/10Fe/10Cu performed satisfactorily.
Example 18
[0186] In this example single layer diamond forms are brazed
directly onto the substrate for making a pad conditioner. LM powder
is mixed with 4 weight percent of acrylic binder to form a
malleable dough. The dough is rolled between two steel rolls to
form a layer 0.2 mm thick. 80/90 mesh diamond grits of IMD-H as
manufactured by Iljin Diamond Company was used to plant into the
sheet. The planting was guided by a template that fixed the diamond
to diamond distance as 0.7 mm. The diamond planted LM layer is then
trimmed in size and glued using an organic binder to a flat
stainless (316) plate 6.5 mm thick. The assembly is then heated in
vacuum to 1010.degree. C. for 10 minutes. The heating caused the LM
to melt and bond to the substrate. The finished diamond disk is
used as a pad conditioner that dressed the pad during the chemical
and mechanical planarization (CMP) of silicon wafers. The result
indicates that such diamond disk can double the life when compared
to a conventional diamond disk that contains randomly distributed
diamond grits.
Example 19
[0187] This is the same as Example 18, except the Nicrobraz LM
powder is 140 mesh.
Example 20
[0188] Nicrobraz LM powder of 325 mesh is mixed with Nicrobraz S
binder to form a slurry. The slurry is then sprayed onto 100 round
stainless steel pallets of 20 mm in diameter and 8 mm thickness to
form a thin coating. The spraying process was repeated until a
thickness of 0.15 mm was achieved. After the coating is dried, a
template with holes drilled to form a square grid with a distance
of 0.5 mm between holes is placed on the substrate. 100/120 mesh
diamonds are then placed on the substrate to form the predetermined
grid pattern. The template is then removed leaving the diamond
particles adhered to the surface. The binder is then removed by
heating in an oven in air at 200.degree. C. for 2 hours. The
assembly is then heated in a vacuum to 1,005.degree. C. for 10
minutes. During this process, the molten braze has wetted the
diamond and capillary force has pulled down the diamond particles
to touch the substrate. The results are diamond pallets with
diamond firmly brazed to form a wetting slope and these diamond
crystals form a predetermined pattern of grid. The resulting tool
is well suited for use in CMP applications.
Example 21
[0189] This is the same as example 12, except that the slurry is a
ready made product supplied by Wall Colmonoy as NICRO-SPRAY.
Example 22
[0190] This is the same as example 12, except the slurry is
prepared by suspending NICROBRAZ LN powder in a methanol benzene
solution containing Nanbau resin (manufactured in Taiwan).
Example 23
[0191] The braze is provided as a sheet of amorphous braze alloy
manufactured by Honeywell as MBF-20 foil about 0.001'' thick.
Various sizes are punched out of the foil and glued to round
stainless steel substrate. A template is then used to arrange 80/90
mesh diamond particles in a predetermined grid pattern. The
assembly is then dewaxed and heated in a vacuum furnace to melt the
alloy and bond the diamond to the substrate. The final tool is used
as a pad conditioner for CMP applications. The resulting tool
demonstrates that the polishing rate can be sustained much longer
than conventional pad conditioners. Further, defects on the
semiconductor wafers is greatly reduced.
Example 24
[0192] The braze is provided as a sheet of amorphous braze alloy
manufactured by Honeywell as MBF-20 foil, having a thickness of
0.002''. Annular sections 100 mm in diameter having 50 mm holes at
the center are punched out of the foil. A template is then placed
on the annular ring of amorphous braze and 60/80 mesh diamond
particles are sprinkled over the template surface. The excess
diamonds are removed and then the template is removed leaving the
diamonds particles set in a predetermined pattern. An additional
annular ring is glued on the top of these diamond particles. Six of
such amorphous alloy-diamond amorphous alloy sandwiches are
assembled with a stainless ring of the same size but with a
thickness of 0.1 mm between every two of such layers. An acrylic
adhesive is used to glue the assembly together. The final assembly
is then heated to 200.degree. C. for 2 hours to drive off the
adhesive. The assembly is then heated in a vacuum furnace at
1,005.degree. C. for 15 minutes. The resulting tool is a three
dimensional structure that contains a diamond array not just on
surface but also in volume. This three dimensional structure is
then mounted to a chuck with a shaft for use as a grinding wheel.
Such a grinding wheel has the unique feature of containing
connected pores around diamond. These pores can serve as runways
for removing cutting debris. The openness of this grinding wheel
makes it free cutting so the cutting speed is twice that of
conventional grinding wheels. Conventional grinding wheels using
metal as matrix contains no such interconnected pores.
[0193] A distinct advantage cutting tools of the present invention
have over the prior art cutting tools lies in the manner in which
the tool may be used. Diamond saws are typically made in the form
of a circular blade that cuts the workpiece by rotation in the same
direction with each rotation. This one directional movement causes
a "tail" to be formed, wherein the matrix material rotationally
forward of the diamond particle is worn away, but the matrix
material behind the diamond particle is protected by the diamond
particle. If the saw rotation were to be reversed, the diamond
particle would easily be knocked free of the matrix.
[0194] Round saws, however, can only cut the work piece to a depth
of less than one-half the diameter of the saw. In order to cut
thicker workpieces, a frame or gang saw is typically used. Because
these saws move reciprocally, the diamond particles must be
securely held on each side. As a result, tails of diamond matrix
cannot be maintained to hold the diamond particles in place. It is
for this reason that reciprocating diamond saws have not been used
to cut hard rock such as granite. Rather they are used to cut only
soft materials such as marble.
[0195] This invention allows diamond to be held chemically by a
braze. Hence, matrix tails are not needed to support the diamond.
As a result, tools made according to the present invention can be
used on reciprocating saws to cut hard materials. This breakthrough
can expand diamond applications to markets, which were previously
unavailable due to limitations of the prior art.
[0196] In addition to being able to improve the performance of the
tool and to reduce the cost of manufacturing, this invention also
provides an easier method for making thin bladed tools. For
example, the electronic industry requires using larger and larger
silicon wafers (now 12 inches in diameter). Hence, thinner saw
blades for slicing silicon crystals, and thinner dicing wheels for
grooving silicon chips with tighter partitions have been in great
demand.
[0197] Prior to the present invention, it has been extremely
difficult to make very thin tools that contain evenly distributed
diamond particles. The present invention provides an alternative
method for making such tools. For example, it has been discovered
that by mixing micron powders of diamond, a blend of metal powders
(e.g., bronze and cobalt) and a suitable binder, the material can
be rolled to a thickness thinner than 0.1 mm--a thickness which is
thinner than most dicing wheels. By firing this thin sheet and
mounting it on a tool holder, a thin dicing wheel can be made.
[0198] In the alternative to the above, it has been found in
accordance with the present invention that some of the advantages
of the controlled distribution, multilayered superabrasive
configurations described above can be achieved without the use of a
template. More specifically, the abrasive particles can also be
mixed in with the matrix powder and made as an ingredient of the
layered sheet. In this case, the distribution of abrasive particles
is still somewhat random. Even so, their distribution is typically
more uniform than that in a conventional abrasive body. The
segregation of abrasive particles and matrix powders discussed in
the background section is less extensive in a substantially
two-dimensional sheet than in a three-dimensional body. This is
particularly true for sheets made by a deforming process (e.g., by
rolling). In this case, abrasive particles are further spread out
in the matrix by the shearing action of the rollers.
[0199] This invention may also be applicable to other applications
not related to making abrasive tools. For example, graphite or
metal sheets planted with diamond particles may be used as seeds
for diamond growth under high pressure and temperature. Industrial
diamonds are typically produced by compressing alternative layers
of graphite and metal catalyst (e.g., Fe, Co, or Ni alloy) to high
pressure and heating above the melting point of the catalyst.
Diamond will then nucleate randomly on the interface of these
layers. The quality of the diamond crystal formed often suffers by
the impingement of growing crystals that are distributed unevenly.
Hence, the yield and cost of diamond synthesis can be substantially
improved by making the nuclei uniformly distributed. This invention
can provide layers of either graphite or metal catalyst with a
pre-determined pattern of diamond seeds. If organic binders are
introduced during the fabrication of these layers, they can be
removed by heating in a furnace before loading into the press.
[0200] Thus, there is disclosed an improved method for making
superabrasive tools with improved performance. The above
description and examples are intended only to illustrate certain
potential uses of this invention. It will be readily understood by
those skilled in the art that the present invention is susceptible
of a broad utility and applications. Many embodiments and
adaptations of the present invention other than those herein
described, as well as many variations, modifications and equivalent
arrangements will be apparent from or reasonably suggested by the
present invention and the forgoing description thereof without
departing from the substance for scope of the present invention.
Accordingly, while the present invention has been described herein
in detail in relation to its preferred embodiment, it is to be
understood that this disclosure is only illustrative and exemplary
of the present invention and is made merely for purpose of
providing a full and enabling disclosure of the invention. The
forgoing disclosure is not intended or to be construed to limit the
present invention or otherwise to exclude any such other
embodiment, adaptations, variations, modifications and equivalent
arrangements, the present invention being limited only by the
claims appended hereto and the equivalents thereof.
[0201] It is to be understood that the above-referenced
arrangements are illustrative of the application for the principles
of the present invention. Numerous modifications and alternative
arrangements may be devised by those skilled in the art without
departing from the spirit and scope of the present invention and
the appended claims are intended to cover such modifications and
arrangements. Thus, while the present invention has been described
above with particularity and detail in connection with what is
presently deemed to be the most practical and preferred embodiments
of the. invention, it will be apparent to those of ordinary skill
in the art that numerous modifications, including, but not limited
to, variations in size, materials, shape, form, function, manner of
operation, assembly, and use may be made without departing from the
invention as set forth in the claims.
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