CA2105190A1

CA2105190A1 - Segmented diamond compact

Info

Publication number: CA2105190A1
Application number: CA002105190A
Authority: CA
Inventors: Ronald L. Frazee
Original assignee: Individual
Current assignee: General Electric Co
Priority date: 1992-09-11
Filing date: 1993-08-19
Publication date: 1994-03-12
Also published as: CA2108405A1; GB2270492A; ZA936325B; GB2270492B; GB9318457D0

Abstract

ABSTRACT OF THE INVENTION

A diamond compact which comprises at least two interlocking segments of thermally stable, polycrystalline diamond is provided wherein the diamond segments are prepared independently and are preferably comprised of diamond particles of a different average grain size to provide improvements in impact resistance and abrasion resistance in tools used for drilling and mining. These compacts are prepared by cutting two or more separately formed diamond clusters to provide complementary surfaces which are bonded together to form one composite compact.

Description

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1 (60-SD-614) SEGN~NTED DI~MOND COMPAC~
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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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i3 2 (60-SD-614) 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 , -~ 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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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 . ~
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 ~i _ , ~ . ~ .

210~(~99 3 (60-SD-614) 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 ::
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 , ~ , 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 --: ' . , ~, 4 (60-SD-614) 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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(60-SD-614) 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 ,~.
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 .~

6 (60-SD-614) 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 ., :, 2 1 ~

7 (60-SD-614) 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 1., 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 f ~1 ~ a ~
8 (60-SD-614) 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 /
~ component~ The presence of any metallic phase is expected .: s .

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21~1g`0 9 (60-SD-614) 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 . ~,,.
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 :
- 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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(60-SD-614) 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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210~1~90 11 (60-SD-614) 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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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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Claims

1. A diamond compact which comprises at least two interlocking segments of thermally stable, polycrystalline diamond produced independently.

2. A diamond compact as in claim 1, wherein at least two of the interlocking segments comprise diamond particles of a different average grain size.

3. A diamond compact which comprises interlocking segments of thermally stable, polycrystalline diamond, wherein at least one segment comprises diamond particles of an average grain size within the range of 30-150 mesh, and at least one segment comprises diamond particles of an average particle diameter of less than 20 µm.

4. A diamond compact as in claim 3, wherein the surface area at the interface between the interlocking segments is more than 150% of the cross sectional area at the interface.

5. A diamond compact as in claim 3, wherein the surface area at the interface between interlocking segments is at least two times that of the cross sectional area of the compact at the interface.

6. A diamond compact as in claim 3, wherein the interlocking segments have a geometric shape which conforms to a corrugated joint, a dovetail joint, a tongue-and-groove joint, a keyhole joint, or a modification thereof.

7. A diamond compact which comprises at least two interlocking segments of thermally stable, polycrystalline diamond, wherein each segment comprises from 10-90% by weight of the total compact, wherein one segment comprises diamond particles of an average grain size within the range of 30-150 mesh, and the other segment comprises diamond par-ticles of an average particle diameter of less than 20 µm.

8. A diamond cluster as in claim 7, wherein the two segments are interlocked by a dovetail joint, a keyhole joint, a tongue-and-groove joint, a corrugated joint, or a modification thereof.

9. A drill bit which comprises a diamond compact of claim 1.

10. A cluster of bonded diamond particles having of a geometric pattern or configuration complementary to another cluster of bonded diamond particles, said diamond cluster of bonded diamond particles being capable of forming a diamond compact when bonded to said other cluster.

11. A kit which comprises at least two clusters of bonded diamond particles having a configuration which enables them to be interlocked and bonded to form a diamond compact.

12. A method for preparing a diamond compact of at least two interlocking segments of thermally stable, polycrystalline diamond which comprises:
forming two or more individual clusters of non-thermally stable bonded diamond particles of a different average grain size with a metallic phase;
cutting each of the clusters of non-thermally stable bonded diamond particles, each with a geometrically shaped surface which complements a geometrically shaped surface of another cluster of bonded diamond particles, wherein the geometrically shaped surfaces have a surface area of more than 100% of the cross sectional area at the interface;

leaching the metallic phase from the cut clusters of non-thermally stable bonded diamond particles to provide thermally stable interlocking segments; and bonding the two or more thermally stable interlocking segments across the complementary surfaces to form a diamond compact.

13. A method as in claim 13, wherein at least one segment comprises diamond particles of an average grain size within the range of 30-150 mesh, and at least one segment comprises diamond particles of an average particle diameter of less than 20 µm.

14. A method as in claim 13, wherein the cut diamond clusters are bonded by the application of a metal interlayer between the segments and sintering the interlayer.

15. A method as in claim 13, wherein each cluster of bonded diamond particles is cut into the desired surface configuration with a traveling wire electron-discharge machine to form interlocking segments, and the metal phase is leached from the cut segments to provide thermal stability.

16. A method for preparing a diamond compact of at least two interlocking segments of thermally stable, polycrystalline diamond which comprises:
forming two or more individual clusters of non-thermally stable bonded diamond particles of a different average grain size with a metallic phase;
leaching the metallic phase from the individual clusters of non-thermally stable bonded diamond particles to provide clusters of thermally stable bonded diamond particles; and cutting each of the clusters of thermally stable bonded diamond particles in geometric shapes which complement each other to provide thermally stable interlocking diamond segments having a surface area of more than 150% of the cross sectional area at the interface; and bonding the thermally stable interlocking diamond segments across the complementary surfaces to form a diamond compact.

17. The invention as defined in any of the preceding claims including any further features of novelty disclosed.