SEGMENTED DIAMOND COMPACTCross-Reference to Related ApplicationsThis application is related to copending applicationSerial No. (Attorney Docket No.: GEMAT 20], entitled,Encapsulation of Segmented Diamond Compact", and assigned to the same assignee as the present invention , filed concurrently herewith.
Background of the InventionThis invention relates to a diamond compact for tools comprised of interlocking segments and a process for the production of such compacts. More particularly, 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 cutting 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 made by first forming diamond particles and 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, bonding 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" 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 5-30t of the compact. The porous compacts are made thermally 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 carbide. 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; 3,767,371; and 3,918,219.
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 well 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 of a coarser grain. In contrast, compacts of a coarsegrain diamond typically show improved wear resistance over fine-grain compacts. In many industries, such as drilling 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 diamond particles. U.S.
Patent No. 3,885,637 describes boring tools wherein coarsegrain 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 tool steel, cemented carbide, and the like.
stsmmary of the InventionIt 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 provide diamond compacts which comprise at least two segments of bonded diamond particles produced independently.
It is still a further object of the present invention to provide diamond compacts comprised of at least two 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, polycrystalline 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 to 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 diamond particles of differing average grain size.
These segmented diamond compacts 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 particles are cut into interlocking 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.
Brief Descrirtion of the DrawingsFigure 1 is a perspective view of a segmented diamond compact of the present invention shown unassembled.
Figure 2 is a perspective representation of another segmented diamond compact of the present invention shown unassembled.
Figure 3 is a perspective representation of another segmented diamond compact of the present invention' shown unassembled.
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.
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 compact of the present invention which is assembled.
Detailed DescriDtion of the InventionThe 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 compact. 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 at the interface. Preferably, the surface area at the interface is more than 150% of the cross sectional area and, more preferably, the surface area is more than twice (200%) the cross sectional area at the 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 modifications thereof, as in Figure 6. Figures 7 and 8 show 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 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 tongueand-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 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.
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 in separate high pressure/high temperature processes. The processes used and the segments obtained can be the same or different. Particular advantage is obtained where the segments are comprised of diamond particles of a different grain size to provide a balance of different features available 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 for the diamond within each segment can vary widely. The particles can be of submicron size to as large as 1000 ym in diameter. Typically, the average particle diameter falls within the range of 0.25200 pm. Preferably, at least one segment has diamond particles of an average grain size in the range of 30-150 mesh. Such segments are preferably interlocked with segments having diamond particles of an average particle diameter of less than 20 m, and preferably from 1-15 pm.
These diamond compacts, which comprise fine-grain diamond segments and coarse-grain diamond segments, show improved impact resistance and/or abrasion resistance over singlegrain diamond compacts.
The impact strength of a diamond compact is lowered with an increase in the average grain size of the diamond 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 propagated due the large skeleton parts, thus leading to breakage of the edge. Therefore, fine diamond grains with a particle diameter of 20 Mm or less provide good impact 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 pm 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 Am.
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. Patent 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. However, preferred materials used as a sintering aid typically include metals recognized as 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 limit on the amount of the 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 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.
Upon formation of the individual clusters of bonded diamond particles by high temperature/high pressure processes, the metallic phase may be removed first. The individual diamond 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 geometric 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 together 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, electrolytic deposition, electroless deposition, or salt bath deposition. The pressures and temperatures utilized to bond the segments are consistent with those used to form 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 2000he. 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 1000-2000sC 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 described in U.S. Patent Nos. 4,188,194; 3,212,852; and 2,947,617.
The compacts produced find use in dies, cutting tools, drill bits, and dressers. The compacts can be brazed directly to a tool substrate such as a tungsten carbidecobalt substrate. A chemically bonded metal layer may be applied to aid adhesion. The 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.
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.
EXAMPLE 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 corm. The clusters to be cut are about 1 g in total weight and about 1 cm in size. The clusters are cut to a desired shape with 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 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 corm, and the two cut segments are assembled and sintered at a conventional 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.
From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.