Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SEGN~NTED DI~MOND COMPAC~
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ck~o~d of t~o In~ti~
This invention relates to a dia~ond co~pact for tools
comprised of interlocking segments and a process for the
~ - production of such compacts. More partic~larly, it is
- ~ concerned with diamond compacts useful as tool components
. ;. comprising at least two interlocking segments of
polycrystalline, self-bonded diamond particles produced
.;; independently, preferably with diamond particles of a
;
different average grain size.
Diamond finds use as an abrasive material in the form
of (a) aggregated particles bonded by a resin or metal
matrix, (b) compacts, and (c) composite compacts. As
bonded aggregates, particles of diamond abrasive are
embedded in a grinding or cut~ing section of a tool such as
a grinding wheel or drill bit.
A compact is defined herein as a cluster of diamond
crystals bound together either in a self-bonded
relationship, by means of a chemically bonded sintering aid
or bonding medium, or some combination of the two. Diamond
compacts can be made by converting graphite particles
directly into a diamond cluster, with or without a metal
catalyst or bonding medium. Alternatively, diamond
compacts can be ~ade by first forming dia~ond particles and
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subsequently bonding them, with or without a sintering aid
or bonding medium. Where a catalyst is used, the diamond
compacts formed are polycrystalline.
Compacts which contain residual metal from a catalyst,
- 5bonding medium, or sintering aid are thermally sensitive
and will experience thermal degradation at elevated
temperatures. Compacts which contain self-bonded
particles, with substantially no secondary non-abrasive
phase, are thermally stable. The "porous compacts"
10-. described in U.S. Patent Nos. 4,224,380 and 4,228,248 are
polycrystalline and contain some non-diamond phase (less
than 3 wt~), yet they are thermally stable. These
compacts have pores dispersed therethrough which comprise
5-30% of the compact. The porous compacts are made
15thermally stable by removal of the metallic phase through
liquid zinc extraction, electrolytic depletion, or a
~" similar process.
A composite compact is defined herein as a compact
bonded to a substrate material such as a cemented tungsten
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-~ 20carbide. The bond to the substrate is formed under high
pressure/high temperature conditions either during or
subsequent to formation of the compact. Examples of
composite compacts and methods for making the same are
.; found in Re. 32,380 and U.S. Patent Nos. 3,743,489;
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~ 253,767,371; and 3,918,219.
.j., :
Diamond compacts and aggregated diamond particles are
used to provide tools for drilling and boring. There is a
~ continuing effort to enhance the useful life of such tools.
; Diamond compacts comprised of coarse-grain diamond are
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30well known to be useful in such tools, as are compacts of
~;~ fine-grain diamond. Advantages are recognized with each
type of compact. Fine-grain compacts often provide the
advantage of leaving smooth surfaces in the material cut or
abraded and show improved impact resistance over compacts
;~ 35of a coarser Igrain. In contrast, compacts of a coarse-
,'''! grain diamond typically show improved wear resistance over
fine-grain compacts. In many industries, such as drilling
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and mining, both impact resistance and abrasion resistance
are important properties for the abrasive components.
While fine-grain diamond compacts provide the desired
impact resistance, they are relatively expensive, making
improvements in wear performance desirable. Coarse-grain
diamond compacts provide the desired wear performance;
however, these diamond compacts often fracture due to poor
impact resistance. It is desirable to provide compacts
with improved abrasion and impact resistance over the
single-grain compacts used commercially.
U.S. Patent No. 4,505,746 describes a diamond compact
for tools such as a wire die comprised of fine-grain
diamond particles and coarse-grain diiam~nd particles. U.S.
Patent No. 3,~85,637 deficribes boring tools wherein coarse-
` 15 grain abrasives are embedded in a matrix layer also
containing fine-grain abrasives embedded therein. U.S.
Patent No. 4,696,352 describes a coated insert for a
drilling tool used in mining and boring, wherein the
coating is a refractory material formed on the substrate of
t~ol steel, cemented carbide, and the like.
; Summary of the Invention
It is an object of the present invention to provide
` diamond compacts with high impact resistance and abrasion
resistance to enhance the useful life of the tools in which
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they are used.
It is another object of the present invention to
provide improved diamond compacts for tools used in
drilling and mining industries that exhibit a longer useful
life and are more economical than diamond compacts
currently employed in tools.
It is a further object of the present invention to
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o provide diamond compacts which comprise at least two
,~ segments of ~onded diamond particles produced
independently !
It is still a further object of the present invention
-` to provide diamond compacts comprised of at least two --
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segments of bonded diamond particles of a different average
grain size.
It is another object of the present invention to
provide a process for producing a segmented, polycrystal-
5line diamond compact comprised of bonded diamond particles
of a different average grain size.
It is an additional object of the present invention to
provide individual geometrically interlocking segments of
` diamond particles and kits thereof which can be assembled
10to form a diamond compact.
The above objects are achieved by providing a diamond
compact which comprises at least two interlocking segments
of bonded diamond particles produced independently,
preferably with dia~ond particles of differing average
15grain size.
These segmented diamond co~pacts are prepared from two
or more clusters of bonded diamond particles produced under
~ independent high temperature/high pressure processes, with
; the aid of a catalyst. The clusters of bonded diamond
, 20particles are cut into in~erlocking segments with geometric
, patterns, and the catalyst is leached therefrom. The
geometric patterns of the interlocking diamond segments are
'; matched, and the matched diamond sections are bonded
together.
25Brief Description of the Drawin~s
~' Figure 1 is a perspective view of a segmented diamond
compact of the present invention shown unasse~bled.
Figure 2 is a perspective representation of another
segmented diamond compact of the present invention shown
30unassembled.
Figure 3 is a perspective representation of another
~segmented diamond compact of the present invention shown
`~ unassembled. ;
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Figure 4 is a perspective representation of another
segmented diamond compact of the present invention shown
unassembled.
Figure 5 is a perspective representation of another
segmented diamond compact of the present invention shown
unassembled.
Figure 6 is a perspective representation of another
segmented diamond compact of the present invention shown
unassembled.
lo Figure 7 is a perspective representation of another
segmented diamond compact of the present invention shown
unassembled.
Figure 8 is a perspective representation of another
segmented diamond compact of the present invention which is
assembled.
Figure 9 is a perspective representation of another
segmented diamond compaçt of the present invention which is
assembled.
Detailed DescriDtion of the Invention
The diamond compacts of the present invention comprise
at least two segments of bonded diamond particles produced
independently. Compacts with more than twenty segments are
.~ within the scope of this invention; however, the practical
limit may be about six segments for most applications due
to the costs of preparing and handling compacts. Special
` applications may call for compacts with many more segments.
Unlike multiple diamond compact segments used to form
abrasive tools, such as in U.S. Patent No. 4,246,004, the
segments of the present invention are interlocked to form
a single oompact. The term "interlocked" as used herein is
intended to define geometric shapes wherein the surface
~; area of the interface between segments is greater than the
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cross sectional area a~ the interface. Preferably, the
- surface area~at the interface i5 more than 150% of the
cross sectional area and, ~ore preferably, the surface area
is more than twice (200%) the cross sectional area at the
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interface. The amount of surface area desired at the
interface will depend on the intended use of the tool
assembled with these compacts.
This can be accomplished with a variety of geometric
designs, as shown in Figures 1-7. The geometric designs
include dovetail joints, as shown in Figures 2 and 9;
- keyhole joints, as shown in Figure 4; tongue-and-groove
joints, as shown in Figures 3 and 5; and m~difications
thereof, as in Figure 6. Figures 7 and 8 show
-~ 10 modifications of the dovetail joint. Figure 1 shows a
corrugated joint with corrugations of a sinusoidal wave
form. Figures 1 and 3 illustrate geometries which provide
moderate levels of surface area at the interface. Such
geometries are more than adequate where the compact will
- 15 not experience shear forces in the plane of the interface
during use.
The segments can vary in size and proportion depending
- on the intended use. Preferably, the segments comprise
from 10-90 wt% of the completed compact, and are typically
from 40-60 wt%, i.e., about 50 wt%, of the completed
compact. Where a dovetail joint, keyhole joint, or tongue-
and-groove joint is used, the cross sectional area at the
base of any protrusion may fall within the range of 20-80~
of the total cross sectional area of the compact. The size
~ 25 of the bases for opposing protrusions may be balanced as
- desired to provide a bond with high shear strength across
~ the plane of the interface.
h.- Individual segments of bonded diamond particles can be
interlocked with other segments to form diamond compacts
which are considered a part of this invention. Kits
comprised of two or more interlocking segments which form
a completed compact are also a part of this invention.
At least two of the segments of the bonded diamond
particles are produced independently, i.e., they are
produced ini separate high pressure/high temperature
processes. The processes used and the segments obtained
` can be the same or different. Particular advantage is
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obtained where the segments are comprised of diamond
particles of a different grain size to provide a balance of
different features availa~le from each segment. Also
included in this invention are multisegmented compacts,
wherein at least two segments are of identical composition
and sandwich one or more segments of a distinct
composition. The identical segments can be produced
simultaneously or cut from the same cluster of bonded
diamond particles.
The average particle size ~or the diamond within each
segment can vary widely. The particles can be of submicron
size to as large as 1000 ~m in diameter. Typically, the
average particle diameter falls within the range of 0.25-
200 ~m. Preferably, at least one segment has diamond
particles of an average grain size in the range of 30-150
mesh. Such seqments are preferably interlocked with
segments having diamond particles of a~ average particle
diameter of less than 20 ~m, and preferably from 1-15 ~m.
; These diamond compacts, which comprise fine-grain diamond
segments and coarse-grain diamond segments, show improved
impact resistance and/or abrasion resistance over single-
grain diamond compacts.
The impact strength of a diamond compact is lowered
with an increase in the average grain size of the diamond
-~ 25 particles therein. A compact of fine diamonds is excellent
in transverse rupture strength, as well as in toughness.
However, since individual grains are held by small
skeletons, their bonding strengths are weak, and the
individual grains can fall off relatively easily during
cutting, resulting in a relatively low overall wear
resistance. On the other hand, in a compact of coarse
diamond grains held by large skeletons, individual diamond
grains have the high bonding strength to impart excellent
wear resistance; but cracks, once formed, tend to be
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propagated due the large skeleton parts, thus leading to
breakage of the edge. Therefore, fine diamond grains with
i a particle diameter of 20 ~m or less provide good impact
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resistance, and coarse diamond grains provide high
toughness. The average grain size of coarse diamond
particles used in the compacts of the present invention
should have an average particle diameter of 20 ~m or more.
A typical example of a bimodal compact of the present
invention is one comprised of two segments, wherein one
segments has diamond particles of an average grain size of
80-120 mesh, and the other segment comprises diamond
particles with an average particle diameter of 4-12 ~m.
The segments of the bonded diamond particles utilized
in this invention can be those obtained by converting
graphite directly into a diamond by high pressure/high
temperature techniques or by two-step procedures whereby
graphite is first converted to diamond, with or without a
catalyst, and the resultant diamond particles are bonded in
a cluster, with the aid of a bonding agent, sintering aid,
or residual conversion catalyst. U.S. Patént Nos.
3,136,615 and 3,233,988 describe examples of suitable
methods for producing diamond compacts or clusters with the
aid of a bonding medium or sintering aid.
-~ The materials that function as the sintering aid can
vary widely. Any metal or ceramic thereof can form the
metallic phase. ~owever, preferred materials used as a
sintering aid typically include metals recognized as
- 25 catalysts for converting graphite into a stronger, more
compact state or for forming compact masses thereof and, in
addition, include ceramics -of such metals such as the
carbides and nitrides of Ti, Ta, Mo, Zr, V, Cr, and Nb.
Reference made herein to a compact segment with a metallic
phase is intended to include those containing more than one
metal.
The amount of material which forms the metallic phase
can vary widely and is preferably below 3 wt% to maintain
- thermal stability. The upper limi~ on the amount of the
I ~ 35 metallic phase within a particular segment is defined by
the performance and effectiveness expected of the tool
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~ component~ The presence of any metallic phase is expected
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to cause some instability at temperatures greater than
700-C. For example, less than 0.05 vol% of a metallic
phase will cause instability under such conditions.
Thermally stable diamonds include clusters of bonded
diamond particles which are porous, as defined in U.S.
Patent Nos. 4,224,380 and 4,288,248. The abrasive in these
porous clusters comprises about 70-95 vol% of the cluster,
which is bonded to form a network of interconnected empty
pores. For porous clusters of bonded diamond particles,
suitable sintering materials include those catalysts
described in U.S. Patent Nos. 2,947,609 and 2,947,610, such
as Group IIIA metals, chromium, manganese, and tantalum.
The porous clusters of bonded diamond particles are not
thermally stable until the second phase is removed.
15Upon formation of the individual clusters of bonded
diamond particles by high temperature/high pressure
processes, the metallic phase may ~e removed first. The
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individual dfamond clusters are cut using a laser into
interlocking segments having geometric patterns.
Conventional power intensities and beam widths can be used.
- Alternatively, the individual clusters may be cut to a
desired shape with a traveling wire electron discharge
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- machine (EDM) before leaching the metallic phase. Such
individual clusters are not thermally stable, and complex
25geometric shapes can be obtained. Once the clusters are
shaped, the metal phase is leached away to provide a
thermally stable segment. -
Matching segments are then bonded together to form a
;~ compact. The individual segments are preferably bonded
30together with the aid of an intermediate metal layer, such
as a carbide former, under high pressure and high
temperature or a low temperature sintering metal such as
~` nickel. The intermediate metal layer may be applied by
conventional techniques such as chemical vapor deposition,
- 35electrolytic deposition, electroless deposition, or salt
bath deposition. The pressures and temperatures utilized
to bond the segments are consistent with those used to form
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conventional sintered bonds within compacts of diamond
particles.
High temperature/high pressure apparatus suitable for
` forming the clusters of bonded diamond particles used to
form the segments herein are described in U.S. Patent No.
`~ 2,941,248. Suitable devices are typically capable of
providing pressures in excess of 100 kilobars and
temperatures in excess of 2000-C. Common components of the
device include a pair of cemented tungsten carbide punches
and a die member of the same material which can withstand
extreme temperatures and-pressures.
Reaction conditions used to form the clusters of
bonded diamond particles and the duration of reaction can
vary widely with the composition of the starting materials,
i.e., graphite types, and the desired end product.
Temperatures and pressures of from 1000-2000-C and
pressures greater than 10 kilobars, such as from 50-95
kilobars, are typical. The actual conditions are dictated
by pressure/temperature phase diagrams for carbon, as
` 20 described in U.S. Patent Nos. 4,188,194; 3,212,852; and
2,947,617.
; The compacts produced find ~lse in dies, cutting tools,
drill bits, and dressers. The compacts can be brazed
directly to a tool substrate such as a tungsten carbide-
cobalt substrate. A chemically bonded metal layer may be
applied to aid adhesion. ~he position and configuration of
the compacts in the tool substrate can vary widely,
depending on the intended use. In some applications, the
compact is preferably positioned to expose the stock to be
cut to all segments of the compact simultaneously.
Without further elaboration, it is believed that one
skilled in the art can, using the preceding description,
utilize the present invention to its fullest extent. The
following preferred specific embodiments are, therefore, to
be construed as merely illustrative and not limitative of
the remainder of the disclosure in any way whatsoever.
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In the foregoing and in the following example, all
temperatures are set forth in degrees Celsius; and, unless
otherwise indicated, all parts and percentages are by
weight.
The entire disclosure of all applications, patents and
publications, cited above and below, are hereby
incorporated by reference.
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BXA~PLE
Clusters of bonded, non-thermally stable
polycrystalline diamond particles, produced by conventional
methods, such as those of U.S. Patent No. 4,224,380, are
selected for cutting into geometric shapes with a traveling
wire EMD. One cluster has diamond particles of from 80-120
mesh size. Another cluster has diamond particles of an
average diameter of from 4-12 ~m. The clusters to be cut
are about 1 g in total weight and about 1 cm3 in size. The
clusters are cut to a desired shape wi~h a conventional
automatic traveling wire electron discharge machine (EDM).
;~ The power and speed of the EDM can vary over conventional
operating conditions. The wire automatically cuts a
` geometric pattern into the surface of each of the clusters
- 15 which complements a surface of another cluster such that
the surface area at the interface is more than 150% of the
cross sectional area. The clusters are cut in the shape of
a sinusoidal wave form, as shown in Figure 1. The segments
: are then leached of the metallic phase by conventional
methods such as that of U.S. Patent No. 4,224,380 to
'~ provide thermally stable interlocking segments. The cut
` surface is coated with a metal interlayer by chemical vapor
deposition at a thickness of about 1-10 ~m, and the two cut
segments are assembled and sintered at a conventional
'~ 25 sintering temperature and pressure.
The preceding example can be repeated with similar
success by substituting the generically or specifically
described reactants and/or operating conditions of this
; invention for those used in the preceding example.
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