Patent Application
20140283457
Cutting elements, such as shear cutter type cutting elements used in rock bits or other cutting tools, typically have a body (i.e., a substrate) and an ultra hard material. The ultra hard material forms the cutting surface of the cutting element, and the substrate is typically provided for the purpose of attacking the Ultra hard material to the cutting tool. The substrate is generally made from tungsten carbide-cobalt (sometimes referred to simply as “cemented tungsten carbide,” “tungsten carbide” or “carbide”). The ultra bard material layer is a polycrystalline ultra hard material, such as polycrystalline diamond (“PCD”), polycrystalline cubic boron nitride (“PCBN”) or thermally stable product (“TSP”) such as thermally stable polycrystalline diamond. The ultra hard material provides a high level of wear and/or abrasion resistance that is greater than that of the metallic substrate.
The PCD material is formed by a known process in which diamond crystals are mixed with a catalyst material and sintered with a substrate at high pressure and high temperature. Catalyst from the substrate also infiltrates the diamond crystals during the sintering process. This sintering process creates as polycrystalline diamond structure having a network of intercrystalline bonded diamond crystals, with the catalyst material remaining in the voids or gaps between the bonded diamond crystals. The catalyst material facilitates and promotes the inter-crystalline bonding. The catalyst material is typically a solvent catalyst metal from Group VIII of the Periodic table (CAS version of the periodic table in the CRC Handbook of Chemistry and Physics), such as cobalt. However, the presence of the catalyst material in the sintered PCD material introduces thermal stresses to the PCD material, when the PCD material is heated, as for example by frictional heating during use, as the catalyst typically has a higher coefficient of thermal expansion than does the PCD material. Thus, the sintered PCD is subject to thermal stresses, which limit the service life of the cutting element. Furthermore, when the operating or servicing temperature reaches or exceeds 700° C., the diamond structure in the PCD layer converts back to graphite with the presence of Group VIII catalyst material, causing structural disintegration in the PCD layer.
To address this problem, the catalyst is substantially removed from the PCD material, such as by leaching, in order to create TSP. For example, one known approach is to remove a substantial portion of the catalyst material from at least a portion of the sintered PCD by subjecting the sintered PCD construction to a leaching process, which forms a TSP material portion substantially free of the catalyst material. The entire PCD layer can be subjected to this leaching process to remove the catalyst material. If the PCD material is attached to a substrate, the substrate and the PCD material can be separated from each other either before or after the leaching process.
After the TSP material has been formed, it is bonded onto a substrate in order to form a cutting element. During this bonding process, the TSP material and substrate are subjected to heat and pressure. An infiltrant material (such as cobalt from the substrate) infiltrates the TSP material, moving into the voids (i.e., the interstitial spaces) between the bonded crystals, previously occupied by the catalyst material. Other metal or metal alloy or non-metallic infiltrants may be used in addition to or instead of cobalt from the substrate. After bonding, the infiltrant(s) can be removed from a portion of the infiltrated TSP material. For example, the infiltrant can be leached from the cutting surface of the infiltrated TSP (opposite the substrate) to remove the infiltrant materials in order to create a thermally stable cutting surface, while retaining the infiltrant in the portion of the infiltrated TSP closer to the substrate, in order to retain a strong bond between the diamond layer and the substrate.
During the catalyst removing step, when the catalyst material is removed from the PCD to form TSP, some residual materials are left behind in the voids between the diamond crystals. Some residuals may be, for example, the residual cobalt carbides in the voids not completely digested by the leaching agent, and corresponding oxides forming afterwards. The presence of these residuals hinders the infiltration of cobalt (or other infiltrant) into the TSP during bonding. Additionally, gases, moisture, and residual leaching agent occupy the voids between the diamond crystals. These gases, moisture, oxides, and other residuals inhibit the infiltration of the infiltrant into the TSP material, as they exert a force against the infiltrant material, that is moving into the TSP.
The result is TSP material that is only partially infiltrated or not properly infiltrated, as the infiltration path is blocked by those residual materials. Partial infiltration is problematic, as thermal and other stresses build in the non-infiltrated region of the TSP. Partial infiltration also makes leaching more difficult, and weakens the bond between the TSP layer and the substrate. Partial infiltration also creates inconsistencies in the performance of the TSP cutting elements. Accordingly, there is a need for a system and method for forming TSP material that facilitates infiltration during bonding, and improves the thermal characteristics of the material.
This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.
In one aspect, embodiments disclosed herein relate to a method for forming a diamond body that includes placing a thermally stable polycrystalline diamond body and a first substrate into an enclosure, the thermally stable polycrystalline diamond body comprising a plurality of bonded diamond crystals and a plurality of interstitial regions between the bonded diamond crystals, the interstitial regions being substantially free of a catalyst material, heating the thermally stable polycrystalline diamond body and the first substrate to remove residual materials from the thermally stable polycrystalline diamond body, subjecting the thermally stable polycrystalline diamond, body and the first substrate to a vacuum for evacuating such residual material, and pressing under high temperature the enclosure, the thermally stable polycrystalline diamond body and the first substrate while maintaining a vacuum in the enclosure to bond the thermally stable polycrystalline diamond body to the substrate.
In another aspect, embodiments disclosed herein relate to a method for forming a diamond body that includes placing a thermally stable polycrystalline diamond body and a substrate into an enclosure, the thermally stable polycrystalline diamond body formed using high temperature and high pressure sintering conditions, heating the thermally stable polycrystalline diamond body and the substrate to remove residual materials from the thermally stable polycrystalline diamond body, maintaining a vacuum in the enclosure while the enclosure, the thermally stable polycrystalline diamond body and the substrate are subjected to high temperature and high pressure to bond the thermally stable polycrystalline diamond body to the substrate, wherein the high temperature and high pressure used in bonding are lower than the high temperature and high pressure sintering conditions.
Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims.
The present invention involves the use of a vacuum-sealed enclosure during a bonding process to improve the properties of an infiltrated TSP cutting element. In one exemplary embodiment, diamond crystals and a catalyst material are high-pressure high-temperature sintered to form a polycrystalline diamond material (PCD). If a substrate is present during this sintering step, catalyst material from the substrate infiltrates the diamond crystal layer. After sintering, the substrate is removed. The catalyst is removed from the PCD, forming a thermally stable product (TSP). In this leaching or removal process, substantially all (about 95% or more, for example 98% or more, or even 99% or more) of the catalyst is removed from at least a portion of the PCD, forming TSP. Alternatively, leaching can be done prior to removing the substrate from the PCD. The TSP is then bonded to a substrate via an HPHT bonding process. The TSP material and the substrate are placed into an enclosure such as a can assembly, heated, and subjected to a vacuum in order to remove gas, moisture, residual leaching agent, and other residuals that can inhibit infiltration of the TSP layer. The TSP material is then bonded to the substrate in a HPHT bonding process. During bonding, an infiltrant such as metal from the substrate infiltrates the TSP layer. Other infiltrants may be used, instead of or in addition to material from the substrate. This method produces a bonded, infiltrated TSP cutting element that is more fully infiltrated than TSP cutting elements created through prior art methods. After the bonding, a portion of the infiltrated TSP cutting layer, such as the top portion of the layer opposite the substrate, may be leached to form a thermally stable cutting surface.
An exemplary embodiment of as method of forming an infiltrated, bonded TSP cutting element according to the present invention is outlined in
The catalyst material may be a metal from Group VIII of the Periodic table (CAS version of the periodic table in the CRC Handbook of Chemistry and Physics), such as cobalt. This material can be provided in powder form and mixed with the ultra hard material to form a uniform distribution, or a substrate, such as a tungsten carbide substrate (WC—Co), may be provided as the source of the catalyst material. If a substrate is used, such as a WC—Co substrate, the catalyst from the substrate, i.e., the cobalt, moves into the voids between the diamond crystals during the HPHT sintering. The catalyst material encourages the growth and bonding of crystals during the HPHT sintering to loon polycrystalline diamond. As used herein, the term “catalyst material” refers to the material that is initially used to facilitate diamond-to-diamond bonding or sintering during the initial HPHT process used to form the PCD.
The HPHT sintering 112 creates a polycrystalline structure as shown in
The leaching can be accomplished by subjecting the PCD material to a leaching agent (such as an acid wash) over a particular period of time or by other known leaching methods such as electrolytic process, and others. When reference is made to leaching or removing the catalyst material from the PCD, it should be understood to mean that a substantial portion of the catalyst material is removed from the part. However, it should also be understood that some small/trace amount of catalyst material may still remain in the TSP part such as within the interstitial regions or adhered to the surface of the diamond crystals. Thus, the leaching or removal process creates a TSP material in which substantially all (about 95% or more, as for example at least 98% or at least 99%) of the catalyst material has been removed from at least a portion of the PCD. In an embodiment, the catalyst material is removed from at least a surface of the PCD. When the resulting TSP layer is bonded to a new substrate, this leached surface faces the substrate so that infiltrant from the substrate can move into the ultra-hard layer, moving into the voids left by the catalyst. In an embodiment, the catalyst material is removed from the entire PCD layer.
Once the catalyst material has been removed, the result is a thermally stable polycrystalline diamond product or body (“TSP”). The TSP body has a material microstructure characterized by a polycrystalline phase of bonded-together diamond crystals 50 and a plurality of substantially empty voids 54 between the bonded diamond crystals 50, as shown in
Referring again to
The bonding process 116 includes placing the TSP material and the substrate into an enclosure 118, such as a can assembly, which protects the TSP material and substrate during bonding. The enclosure will now be described, referring to
The substrate 12 and TSP layer 14 are placed in the can through a top opening 44, with the substrate 12 above the TSP layer 14. The TSP layer rests on an insulator layer 36 that prevents the TSP material from touching and reacting with the walls and floor of the can 32. In an exemplary embodiment, the insulator is in powder form. The TSP and substrate are pushed down into the can to cause the insulator 36 to flow up around the sides of the TSP layer and the substrate. The insulator material is a non-sintering, non-reacting material such as hexagonal boron nitride (HBN), cubic boron nitride (CBN), silicon nitride, an oxide, or a ceramic. HBN is preferred for its good flowability. The insulator layer insulates the can from the TSP diamond and vice versa. A disc 38 made from the same material as the can is placed on top of the substrate 12 in the can, as shown in
After the insulator layer 36, TSP material 14, substrate 12, and disc 38 are placed into the can 32, and the TSP and substrate have been pushed down into the insulator, the top end 34a of the peripheral wall 34 of the can is folded over to retain these materials in the can 32. A layer or disc of braze material 40 is placed on top of the disc 38 and folded end 34a, whereby the folded end is sandwiched between the disc 38 and the braze material disc 40. In an exemplary embodiment, the folded portion overlaps the disc 38 along its entire periphery. Finally, a can cap or lid 42 is placed over the braze material to complete the can assembly 30. Optionally, the outer end 42a of the cap 42 is folded over as shown in
The braze material 40 may be provided in the form of a disc 40, as shown in
Referring again to
The method also includes applying a vacuum to the can assembly. In an exemplary embodiment, the vacuum is applied by a vacuum furnace. The vacuum can be applied after the heating step is completed, or the vacuum can be initiated before heating and maintained simultaneously with the heating. Thus, referring to
While maintaining the vacuum, the temperature is then raised to a second temperature that is equal to or higher than the melting point of the braze. This temperature may be just past the melting temperature of the braze. This second temperature may be between 800-1200° C. As the braze melts it flows around the cap 42 and on disc 38 to seal the top opening 44 of the can 32. After the braze has melted and flowed into the gaps 46, the temperature is lowered so that the braze cools and solidifies to seal the can. The vacuum is maintained as the braze solidifies, such that a vacuum is created inside the sealed can. In one embodiment, the vacuum inside the can is 10−4 Ton or lower, and preferably 10−5 Torr or even 10−6 Torr or lower. The vacuum may be within the typical pressure range of any suitable commercially-available vacuum furnace.
Alternatively, the can assembly can be heated first and then subjected to vacuum. Thus, in an embodiment, the bonding process includes heating the can 122 and then (sequentially) applying a vacuum 124. The material is heated to a temperature that is high enough to clean the TSP and substrate materials, as described before. Then, the can assembly is allowed to cool to room temperature. A vacuum is applied to evacuate all of the residuals and gases that accumulated during the heating step. The can is then sealed at room temperature such as by welding it closed, so that a vacuum is formed inside the can. Electron beam welding (“EB welding”) is well known as a sealing process. In this embodiment, it is not necessary to include the braze disc 40.
In both cases (applying the heat and vacuum simultaneously 120 or sequentially 122, 124), in an exemplary embodiment the vacuum is sufficient to remove at least 20% of the residuals in the TSP layer, and in another embodiment at least 50%, and in another embodiment at least 80%. In exemplary embodiments, the vacuum is sufficient to remove at least 95% of the residuals in the TSP layer, such as about 98% or about 99%. The amount of residuals removed from the TSP layer can be determined through gas fusion analysis.
The vacuum furnace may be any suitable, commercially-available vacuum furnace, such as one provided, by Centorr Vacuum Industries, of Nashua, N.H. A combination of a mechanical pump and a turbomolecular vacuum pump/diffusion pump may be used. The can assembly is typically cooled to room temperature inside the vacuum furnace after it is heated and sealed. A vacuum may still be applied while the sealed can assembly is cooling to room temperature.
Finally, the bonding process 116 includes applying heat and pressure to the sealed can, with the TSP and the substrate inside, to bond the TSP to the substrate 126. This can be referred to as “HPHT bonding” and includes placing the vacuum-sealed can assembly into an HPHT assembly and pressing it at high heat and pressure to bond the TSP material to the substrate. The HTHP bonding step may have different durations, temperatures, and pressures than the HTHP sintering step. For example, the temperatures and pressures may be lower during bonding than during HPHT sintering 112. During this final bonding step, an infiltrant will infiltrate the leached TSP material, moving into the voids between the diamond crystals and acting as a glue to bond the TSP layer to the substrate. The infiltrant is typically a metal from the substrate, such as cobalt, but other infiltrants such as other metals or metal alloys may be used. For example, an added infiltrant in the form of a powder, foil, or film may be provided between the TSP and substrate to infiltrate both the TSP layer and the substrate and facilitate bonding of these two layers, or additional infiltrant may be placed on the side of the TSP layer opposite the substrate. The term “infiltrant” as used herein refers to a material other than the catalyst material used to initially form the PCD material, and can include materials in Group VIII of the Periodic table (CAS version of the periodic table in the CRC Handbook of Chemistry and Physics). In an exemplary embodiment, the lower half of the TSP layer (nearest the substrate) is substantially infiltrated by the infiltrant.
Optionally, after bonding, the infiltrant can be removed from a portion of the infiltrated TSP material 128 as for example from the portion that does the cutting and is exposed to high frictional heat, to improve the thermal stability of that portion of the TSP layer. For example, in one embodiment, substantially all of the infiltrant is removed by leaching from the exposed cutting surface of the TSP layer to a certain depth, but not all the way through the TSP layer to the substrate. Thus, a portion of the infiltrated TSP layer closer to the substrate still retains the infiltrant in the voids between the diamond crystals. The presence of the infiltrant here preserves the bonding of the infiltrated TSP layer to the substrate. As before, in the areas where substantially all of the infiltrant is removed, trace amounts of infiltrant may remain. The TSP material layer having at least a portion leached of an infiltrant may be infiltrated with an oxide, nitride or a ceramic for improving the TSP material toughness and wear resistance.
The infiltrated TSP cutting element can then he incorporated into a cutting tool such as a tool for mining, cutting, machining, milling, and construction applications, where properties of thermal stability, wear and abrasion resistance, and reduced thermal stress are desirable. For example, the cutting element of this invention may be incorporated into machine tools and drill and mining bits such as roller cone drill bits, and drag bits (fixed cutter drill bits).
Maintaining a vacuum in the can assembly during bonding improves the infiltration of the infiltrant material into the TSP diamond interstitial spaces. The vacuum prevents residual materials and outgases from pushing against, the infiltrant and blocking its path. As a result, the infiltrant can move more easily into the TSP layer, and the TSP layer is more fully infiltrated than a TSP material formed without maintaining a vacuum during the bonding process, providing for a better bond between the TSP layer and the substrate. Fully infiltrating the TSP reduces stresses between infiltrated and non- or partially-infiltrated regions. Vacuum sealing aids in fully infiltrating thicker TSP layers and enhances process consistency.
For example,
As explained above, during bonding, the metal infiltrant moves into voids between bonded diamond crystals. When the TSP layer is only partially infiltrated, due to the presence of residual materials as described above, the voids 16 will be only partially filled with the infiltrant 18, leaving un-filled areas 18a, as shown in
Relative sizes are exaggerated in
Although the present invention has been described and illustrated in respect to exemplary embodiments, it is to be understood that it is not to be so limited, since changes and modifications may be made therein which are within the full intended scope of this invention as hereinafter claimed. For example, the infiltrants identified herein for infiltrating the TSP material have been identified by way of example. Other infiltrants may also be used to infiltrate the TSP material and include any metals and metal alloys such as Group VIII and Group IB metals and metal alloys (CAS version of the periodic table in the CRC Handbook of Chemistry and Physics). Moreover, it should be understood that the TSP material may he attached to other carbide substrates besides tungsten carbide substrates, such as substrates made of carbides of W, Ti, Mo, Nb, V, Hf, Ta, and Cr.
This Application is a Continuation of U.S. application Ser. No. 12/852,071, filed on Aug. 6, 2010, which claims priority to and the benefit of U.S. Provisional Application 61/232,228, filed on Aug. 7, 2009, the contents of both of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61232228 | Aug 2009 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12852071 | Aug 2010 | US |
| Child | 14297320 | US |
