Methods Of Forming Polycrystalline Diamond Cutters

Abstract

A method for forming a cutting element that includes forming at least one cavity in at least one surface of a polycrystalline abrasive body; placing the polycrystalline abrasive body adjacent a substrate such that an opening of at least one cavity is adjacent the substrate at an interface, wherein an interface surface of the substrate is non-mating with the polycrystalline abrasive body; and subjecting the polycrystalline abrasive body and substrate to high pressure/high temperature conditions is disclosed.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority, under 35 U.S.C. .sctn.119, to U.S. Patent Application No. 61/081,619, filed on Jul. 17, 2008, which is herein incorporated by reference in its entirety.

BACKGROUND OF INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates generally to polycrystalline diamond composites and cutting structures. More particularly, this invention relates to polycrystalline diamond cutting structures that having non-planar interfaces and method of forming such non-planar interfaces.

[0004] 2. Background Art

[0005] Polycrystalline diamond compact ("PDC") cutters have been used in industrial applications including rock drilling and metal machining for many years. In a typical application, a compact of polycrystalline diamond (PCD) (or other superhard material) is bonded to a substrate material, which is typically a sintered metal-carbide to form a cutting structure. PCD comprises a polycrystalline mass of diamonds (typically synthetic) that are bonded together to form an integral, tough, high-strength mass or lattice. The resulting PCD structure produces enhanced properties of wear resistance and hardness, making PCD materials extremely useful in aggressive wear and cutting applications where high levels of wear resistance and hardness are desired.

[0006] A PDC cutter may be formed by placing a cemented carbide substrate into the container of a press. A mixture of diamond grains or diamond grains and catalyst binder is placed atop the substrate and treated under high pressure, high temperature conditions. In doing so, metal binder (often cobalt) migrates from the substrate and passes through the diamond grains to promote intergrowth between the diamond grains. As a result, the diamond grains become bonded to each other to form the diamond layer, and the diamond layer is in turn bonded to the substrate. The substrate often comprises a metal-carbide composite material, such as tungsten carbide. The deposited diamond layer is often referred to as the "diamond table" or "abrasive layer."

[0007] An example of a drag bit for earth formation drilling using PDC cutters is shown in FIG. 1. FIG. 1 shows a rotary drill bit 10 having a bit body 12. The lower face of the bit body 12 is formed with a plurality of blades 14, which extend generally outwardly away from a central longitudinal axis of rotation 16 of the drill bit. A plurality of PDC cutters 18 are disposed side by side along the length of each blade. The number of PDC cutters 18 carried by each blade may vary. The PDC cutters 18 are individually brazed to a stud-like carrier (or substrate), which may be formed from tungsten carbide, and are received and secured within sockets in the respective blade.

[0008] Common problems that plague cutting elements and specifically cutters having an ultra hard diamond-like cutting table such as PCD, polycrystalline cubic boron nitride (PCBN), or thermally stable polycrystalline diamond (TSP) bonded on a cemented carbide substrate are chipping, spalling, partial fracturing, cracking or exfoliation of the cutting table. These problems result in the early failure of the cutting table and thus, in a shorter operating life for the cutter.

[0009] It has been thought that these problems, i.e., chipping, spalling, partial fracturing, cracking, and exfoliation of the diamond layer may be caused in part by the difference in the coefficient of thermal expansion between the diamond and the substrate. Specifically, the problems are thought to be caused by the abrupt shift in the coefficient of thermal expansion on the interface between the substrate and the diamond. This abrupt shift causes the build-up of residual stresses on the cutting layer.

[0010] The cemented carbide substrate has a higher coefficient of thermal expansion than the diamond. During sintering, both the cemented carbide body and diamond layer are heated to elevated temperatures forming a bond between the diamond layer and the cemented carbide substrate. As the diamond layer and substrate cool down, the substrate shrinks more than the diamond because of its higher coefficient of thermal expansion. Consequently, stresses referred to as thermally induced stresses are formed at the interface between the diamond and the body.

[0011] Moreover, residual stresses are formed on the diamond layer from decompression after sintering. The high pressure applied during the sintering process causes the carbide to compress more than the diamond layer. After the diamond is sintered onto the carbide and the pressure is removed, the carbide tries to expand more than the diamond imposing a tensile residual stress on the diamond layer.

[0012] In an attempt to overcome these problems, many have turned to use of non-planar interfaces between the substrate and the cutting layer. The belief being, that a non-planar interface allows for a more gradual shift in the coefficient of thermal expansion from the substrate to the diamond table, thus, reducing the magnitude of the residual stresses on the diamond. Similarly, it is believed that the non-planar interface allow for a more gradual shift in the compression from the diamond layer to the carbide substrate.

[0013] Accordingly, there exists a continuing need for developments in non-planar interfaces, and methods of forming non-planar interfaces, for cutting elements having a polycrystalline abrasive cutting layer attached to a substrate.

SUMMARY OF INVENTION

[0014] In one aspect, embodiments disclosed herein relate to a method for forming a cutting element that includes forming at least one cavity in at least one surface of a polycrystalline abrasive body; placing the polycrystalline abrasive body adjacent a substrate such that an opening of at least one cavity is adjacent the substrate at an interface, wherein an interface surface of the substrate is non-mating with the polycrystalline abrasive body; and subjecting the polycrystalline abrasive body and substrate to high pressure/high temperature conditions.

[0015] In another aspect, embodiments disclosed herein relate to a method for forming a cutting element that includes forming a polycrystalline diamond compact of a polycrystalline diamond body attached to a substrate, where the formation of the polycrystalline diamond compact includes placing a mixture of diamond particles and a catalyst material adjacent a substrate; and subjecting the mixture and substrate to high-pressure/high temperature conditions; then, once the polycrystalline diamond compact is formed, detaching the polycrystalline diamond body from the substrate; forming at least one cavity in at least one surface of the detached polycrystalline diamond body; placing the polycrystalline abrasive body adjacent a substrate material such that an opening of at least one cavity is adjacent the substrate material; and subjecting the polycrystalline abrasive body and substrate material to high temperature/high pressure conditions.

[0016] In another aspect, embodiments disclosed herein relate to a method for forming a cutting element that includes forming at least one cavity in at least one surface of a polycrystalline abrasive body; placing the polycrystalline abrasive body adjacent a substrate precursor material such that an opening of at least one cavity is adjacent the substrate precursor; and subjecting the polycrystalline abrasive body and substrate precursor materials to high pressure/high temperature conditions.

[0017] In another aspect, embodiments disclosed herein relate to a cutting element that includes a polycrystalline abrasive body; and a substrate attached to the polycrystalline abrasive body, wherein the polycrystalline abrasive body comprises, at the interface between the polycrystalline abrasive body and the substrate, at least one cavity formed therein, the at least one cavity having an opening with at least one dimension of less than 1 mm; and wherein the substrate comprises at least one projection mating the at least one cavity.

[0018] In yet another aspect, embodiments disclosed herein relate to a cutting element that includes a polycrystalline abrasive body; and a substrate attached to the polycrystalline abrasive body, wherein the polycrystalline abrasive body comprises, at the interface between the polycrystalline abrasive body and the substrate, at least one cavity formed therein; and wherein the substrate comprises at least one projection mating the at least one cavity, the at least one projection comprising a material composition distinct from the remaining substrate.

[0019] Other aspects and advantages of the invention will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

[0020] FIG. 1 is an illustration of a PDC drill bit.

[0021] FIGS. 2A-2E show cross-sectional side views of various embodiments of the present disclosure.

[0022] FIGS. 3A-3B show top views of various embodiments of the present disclosure.

[0023] FIGS. 4A-4C is an illustration of steps for forming a PDC cutter in accordance with an embodiment of the present disclosure.

[0024] FIGS. 5A-5D is an illustration of steps for forming a PDC cutter in accordance with an embodiment of the present disclosure.

[0025] FIGS. 6A-6E is an illustration of steps for forming a PDC cutter in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0026] In one aspect, embodiments disclosed herein relate to polycrystalline diamond (or other polycrystalline abrasive bodied) cutting elements and methods of forming non-planar interfaces between the polycrystalline diamond layer and a substrate. More specifically, embodiments disclosed herein are directed to non-planar interfaces resulting from forming cavities in a polycrystalline abrasive body and attaching the body to a substrate.

[0027] As used herein, the term "PCD" refers to polycrystalline diamond that has been formed, at high pressure/high temperature (HPHT) conditions, through the use of a solvent metal catalyst, such as those included in Group VIII of the Periodic table. However, the present disclosure is also directed to polycrystalline cubic boron nitride (formed from subjecting boron nitride particles to HPHT conditions) as well as thermally stable polycrystalline diamond. The term "thermally stable polycrystalline diamond," as used herein, refers to intercrystalline bonded diamond that includes a volume or region that has been rendered substantially free of the solvent metal catalyst used to form PCD, or the solvent metal catalyst used to form PCD remains in the region of the diamond body but is otherwise reacted or rendered ineffective in its ability to adversely impact the bonded diamond at elevated temperatures as discussed above.

[0028] Forming Polycrystalline Abrasive Bodies

[0029] A polycrystalline diamond body may be formed in a conventional manner, such as by a high pressure, high temperature sintering of "green" particles to create intercrystalline bonding between the particles. "Sintering" may involve a high pressure, high temperature (HPHT) process. Examples of high pressure, high temperature (HPHT) process can be found, for example, in U.S. Pat. Nos. 4,694,918; 5,370,195; and 4,525,178. Briefly, to form the polycrystalline diamond object, an unsintered mass of diamond crystalline particles is placed within a metal enclosure of the reaction cell of a HPHT apparatus. A suitable HPHT apparatus for this process is described in U.S. Pat. Nos. 2,947,611; 2,941,241; 2,941,248; 3,609,818; 3,767,371; 4,289,503; 4,673,414; and 4,954,139. A metal catalyst, such as cobalt or other Group VIII metals, may be included with the unsintered mass of crystalline particles to promote intercrystalline diamond-to-diamond bonding. The catalyst material may be provided in the form of powder and mixed with the diamond grains, or may be infiltrated into the diamond grains during HPHT sintering An exemplary minimum temperature is about 1200.degree. C. and an exemplary minimum pressure is about 35 kilobars. Typical processing is at a pressure of about 45 kbar and 1300.degree. C. Those of ordinary skill will appreciate that a variety of temperatures and pressures may be used, and the scope of the present invention is not limited to specifically referenced temperatures and pressures.

[0030] Diamond grains useful for forming a polycrystalline diamond body may include any type of diamond particle, including natural or synthetic diamond powders having a wide range of grain sizes. For example, such diamond powders may have an average grain size in the range from submicrometer in size to 100 micrometers, and from 1 to 80 micrometers in other embodiments. Further, one skilled in the art would appreciate that the diamond powder may include grains having a mono- or multi-modal distribution.

[0031] Moreover, the diamond powder used to prepare the PCD body may be synthetic diamond powder or natural diamond powder. Synthetic diamond powder is known to include small amounts of solvent metal catalyst material and other materials entrained within the diamond crystals themselves. Unlike synthetic diamond powder, natural diamond powder does not include such solvent metal catalyst material and other materials entrained within the diamond crystals. It is theorized that that inclusion of materials other than the solvent catalyst in the synthetic diamond powder can operate to impair or limit the extent to which the resulting PCD body can be rendered thermally stable, as these materials along with the solvent catalyst must also be removed or otherwise neutralized. Because natural diamond is largely devoid of these other materials, such materials do not have to be removed from the PCD body and a higher degree of thermal stability may thus be obtained. Accordingly, for applications calling for a particularly high degree of thermal stability, one skilled in the art would appreciate that the use of natural diamond for forming the PCD body may be preferred. The diamond grain powder, whether synthetic or natural, may be combined with or already includes a desired amount of catalyst material to facilitate desired intercrystalline diamond bonding during HPHT processing. Suitable catalyst materials useful for forming the PCD body include those solvent metals selected from the Group VIII of the Periodic table, with cobalt (Co) being the most common, and mixtures or alloys of two or more of these materials. In a particular embodiment, the diamond grain powder and catalyst material mixture may comprise 85 to 95% by volume diamond grain powder and the remaining amount catalyst material. Alternatively, the diamond grain powder can be used without adding a solvent metal catalyst in applications where the solvent metal catalyst can be provided by infiltration during HPHT processing from the adjacent substrate or adjacent other body to be bonded to the PCD body.

[0032] The diamond powder may be combined with the desired catalyst material, and the reaction cell is then placed under processing conditions sufficient to cause the intercrystalline bonding between the diamond particles. In the event that the formation of a PCD compact comprising a substrate bonded to the PCD body is desired, a selected substrate is loaded into the container adjacent the diamond powder mixture prior to HPHT processing. Additionally, in the event that the PCD body is to be bonded to a substrate, and the substrate includes a metal solvent catalyst, the metal solvent catalyst needed for catalyzing intercrystalline bonding of the diamond may be provided by infiltration, in which case is may not be necessary to mix the diamond powder with a metal solvent catalyst prior to HPHT processing.

[0033] In an example embodiment, the device is controlled so that the container is subjected to a HPHT process comprising a pressure in the range of from 5 to 7 GPa and a temperature in the range of from about 1320 to 1600.degree. C., for a sufficient period of time. During this HPHT process, the catalyst material in the mixture melts and infiltrates the diamond grain powder to facilitate intercrystalline diamond bonding. During the formation of such intercrystalline diamond bonding, the catalyst material may migrate into the interstitial regions within the microstructure of the so-formed PCD body that exists between the diamond bonded grains It should be noted that if too much additional non-diamond material is present in the powdered mass of crystalline particles, appreciable intercrystalline bonding is prevented during the sintering process. Such a sintered material where appreciable intercrystalline bonding has not occurred is not within the definition of PCD. Following such formation of intercrystalline bonding, a polycrystalline diamond body may be formed that has, in one embodiment, at least about 80 percent by volume diamond, with the remaining balance of the interstitial regions between the diamond grains occupied by the catalyst material. In other embodiments, such diamond content may comprise at least 85 percent by volume of the formed diamond body, and at least 90 percent by volume in yet another embodiment. However, one skilled in the art would appreciate that other diamond densities may be used in alternative embodiments. Thus, the polycrystalline diamond bodies being used in accordance with the present disclosure include what is frequently referred to in the art as "high density" polycrystalline diamond.

[0034] Further, one skilled in the art would appreciate that, frequently, a diamond layer is sintered to a carbide substrate by placing the diamond particles on a preformed substrate in the reaction cell and sintering. However the present disclosure is not so limited. Rather, the polycrystalline diamond bodies having cavities formed in accordance with the present disclosure may or may not be formed attached to a substrate. If the polycrystalline diamond body is formed attached to a carbide substrate, the substrate may be removed or detached from the polycrystalline diamond body so that cavities may be formed therein, and a non-planar interface may result when the diamond body reattached to a substrate.

[0035] In various embodiments, a formed PCD body having a catalyst material in the interstitial spaces between bonded diamond grains is subjected to a leaching process (before or after formation of the cavities), whereby the catalyst material is removed from the PCD body. As used herein, the term "removed" refers to the reduced presence of catalyst material in the PCD body, and is understood to mean that a substantial portion of the catalyst material no longer resides in the PCD body. However, one skilled in the art would appreciate that trace amounts of catalyst material may still remain in the microstructure of the PCD body within the interstitial regions and/or adhered to the surface of the diamond grains. Alternatively, rather than actually removing the catalyst material from the PCD body or compact, the selected region of the PCD body or compact can be rendered thermally stable by treating the catalyst material in a manner that reduces or eliminates the potential for the catalyst material to adversely impact the intercrystalline bonded diamond at elevated temperatures. For example, the catalyst material can be combined chemically with another material to cause it to no longer act as a catalyst material, or can be transformed into another material that again causes it to no longer act as a catalyst material. Accordingly, as used herein, the terms "removing substantially all" or "substantially free" as used in reference to the catalyst material is intended to cover the different methods in which the catalyst material can be treated to no longer adversely impact the intercrystalline diamond in the PCD body or compact with increasing temperature.

[0036] The quantity of the catalyst material remaining in the material PCD microstructure after the PCD body has been subjected to a leaching treatment may vary, for example, on factors such as the treatment conditions, including treatment time, as well as whether the cavities are formed before or after leaching. A U.S. Patent Application entitled "Methods of Forming Thermally Stable Polycrystalline Diamond Cutters," filed concurrently herewith (Attorney Docket No. 05516/392001), which is assigned to the present assignee and herein incorporated by reference in its entirety, is directed to the use of forming cavities or other acid infusion pathways to reduce leaching times. Further, one skilled in the art would appreciate that it may be desired in certain applications to allow a small amount of catalyst material to stay in the PCD body. In a particular embodiment, the PCD body may include up to 1-2 percent by weight of the catalyst material. However, one skilled in the art would appreciate that the amount of residual catalyst present in a leached PCD body may depend on the diamond density of the material, and body thickness.

[0037] A conventional leaching process involves the exposure of an object to be leached with a leaching agent, such as described in U.S. Pat. No. 4,224,380, which is herein incorporated by reference in its entirety. In select embodiments, the leaching agent may be a weak, strong, or mixtures of acids. In other embodiments, the leaching agent may be a caustic material such as NaOH or KOH. Suitable acids may include, for example, nitric acid, hydrofluoric acid, hydrochloric acid, sulfuric acid, phosphoric acid, or perchloric acid, or combinations of these acids. In addition, caustics, such as sodium hydroxide and potassium hydroxide, have been used to the carbide industry to digest metallic elements from carbide composites. In addition, other acidic and basic leaching agents may be used as desired. Those having ordinary skill in the art will appreciate that the molarity of the leaching agent may be adjusted depending on the time desired to leach, concerns about hazards, etc.

[0038] Further, one skilled in the art would appreciate that the same techniques used with polycrystalline diamond may be applied to polycrystalline cubic boron nitride (PCBN). Similar to polycrystalline diamond, PCBN may be formed by sintering boron nitride particles (typically CBN) via a HPHT process, similar to those for PCD, to sinter "green" particles to create intercrystalline bonding between the particles. CBN refers to an internal crystal structure of boron atoms and nitrogen atoms in which the equivalent lattice points are at the corner of each cell. Boron nitride particles typically have a diameter of approximately one micron and appear as a white powder. Boron nitride, when initially formed, has a generally graphite-like, hexagonal plate structure. When compressed at high pressures (such as 106 psi), CBN particles will be formed with a hardness very similar to diamond, and a stability in air at temperatures of up to 1400.degree. C.

[0039] According to one embodiment of the invention, PCBN may include a content of boron nitride of at least 50% by volume; at least 70% by volume in another embodiment; at least 85% by volume in yet another embodiment. In another embodiment, the cubic boron nitride content may range from 50 to 80 percent by volume, and from 80 to 99.9 percent by volume in yet another embodiment. The residual content of the polycrystalline cubic boron nitride composite may include at least one of Al, Si, and mixtures thereof, carbides, nitrides, carbonitrides and borides of Group IVa, Va, and VIa transition metals of the periodic table. Mixtures and solid solutions of Al, Si, carbides, nitrides, carbonitrides and borides of Group IVa, Va, and VIa transition metals of the periodic table may also be included.

[0040] Formation on Non-Planar Interface

[0041] Thus, formation of a cutting element having a non-planar interface between the abrasive cutting layer and substrate may involve any of the above-described abrasive bodies. Conventionally, formation of a non-planar interface involves forming such geometry in the substrate, and combining the substrate with diamond (or other super hard) particles in a reaction can and subjecting the can contents to HPHT conditions to form the polycrystalline structure. However, the techniques of the present disclosure rely on forming a desired geometry (cavity) in a pre-formed polycrystalline layer, and then attaching the polycrystalline layer with desired interface geometry to a substrate (or forming the substrate attached to the polycrystalline layer having the desired geometry).

[0042] Cavities formed by removal of PCD material may include partial cavities (cavities extending partially into the diamond layer) and/or through-cavities or channels (cavities extending the entire thickness of the diamond layer). Such cavities may be formed using any technique known in the art of cutting diamond, including, for example, methods such as EDM, laser micro machining, ion beam milling (also referred to as ion bombardment etching), etc. Alternatively, the cavity may be formed by incorporation of an aiding material into the diamond mixture prior to sintering, where the aiding material may be removed by chemical or physical methods prior to leaching, such that once subsequently removed, cavities are present in the polycrystalline diamond body. For example, a tungsten carbide aiding material may be formed in the diamond body, and then subsequently removed by machining or other physical methods so that a cavity remains in the diamond body to allow for the formation of the non-planar interface. Further, aiding materials other than tungsten carbide, such as other ceramics, may also easily be used so long as the aiding material is removable by physical or chemical methods. Use of such an aiding material may be desirable if the aiding material is more easily removed than cutting diamond.

[0043] Referring to FIGS. 2A-2E, various embodiments of PCD bodies 30 having cavities 35 formed therein are shown. As shown in FIG. 2A, cavities 35 are through-cavities or channels, extending the entire thickness or depth of PCD body 30, from a top surface 31 to a bottom surface 33. In FIG. 2B, cavities 35 are partial cavities, extending partially from bottom surface 33 a depth less than top surface 31. Moreover, while FIGS. 2A and 2B show cavities 35 formed perpendicular to surfaces 31, 33, the present invention is not so limited. Rather, as shown in FIGS. 2C and 2D, such cavities 35 may extend into or through PCD body 30 at an angle to surfaces 31, 33. Additionally, such cavities 35 may take any geometrical (regular or irregular) shape or form, including for example, having a generally equal or varying (e.g., cavity 35 may be a dimple as shown in FIGS. 2D and 2E) diameter along the length of the cavity 35, as well as any peaks, valleys, grooves, ridges, etc., or any other shape that may be formed in a substrate in conventional non-planar interface techniques. Additionally, as shown by comparing the general representative size of the various cavities 35 shown in FIGS. 2A-2E, cavities 35 may be selected to have different general relative dimensions depending, for example, on the methods by which the cavities 35 are being formed, among other design considerations. Thus, in some embodiments, for example, as shown in FIG. 2E, a cavity 35 may be selected to have a generally large diameter at the intersection between the cavity and a surface 33 of the PCD body 30, ranging as large as the diameter of the cutter or one-half the diameter of the PCD body 30, or may be smaller as illustrated shown in FIGS. 2A-2D. In particular embodiments, the diameters (or general dimension for non-circular cavity openings) of the cavities may range from millimeter scale (up to 3 mm in some embodiments) to microscale (less than 1 mm and less than 50 microns) to nanoscale (down to 100, 50, or 10 nm in various embodiments). In an even more particular embodiment, cavities of diameter ranging from 10 microns to 1 mm (or to 0.5 mm in another embodiment) may be formed in the diamond body. However, one skilled in the art would appreciate that the selected size may be based on factors such as the size of the PCD body, the techniques by which the cavities are formed, any effect on the material and mechanical properties of the PCD body, etc. It is also within the scope of the present disclosure that various combinations of type, number, shape, size of cavities may be made, such as shown in FIG. 2D.

[0044] Moreover, there is also no limit on the placement or pattern of the cavities formed in the PCD body. For example, as shown in FIGS. 3A and 3B, the pathways 35 may take any regular array of even spaced cavities or form a pattern of concentric circles. However, the cavities may also be randomly distributed across a PCD body.

[0045] Further, as mentioned above, while the above discussion has applied to PCD cutting elements or bodies, those having ordinary skill in the art will appreciate that these techniques may be more generally applied to any material that has a need for a non-planar interface. In a particular embodiment, the PCD bodies may be at least 1 mm thick, and at least 1.5 or 2 mm thick in alternate embodiments.

[0046] Further after such "free-standing" PCD bodies are having cavities formed therein, the PCD bodies may then be attached (or reattached) to a substrate and form the non-planar interface, to facilitate attached to a bit, cutting tool, or other end use, for example. Such methods of reattachment may include sintering a PCD body with a substrate in a second HPHT sintering step, such as discussed in U.S. Patent Publication No. 2008/0223623, which is assigned to the present assignee and herein incorporated by reference in its entirety. The HPHT sintering used to attach a diamond body to the substrate may be performed in a similar manner as described above with respect to formation of polycrystalline diamond, but in particular embodiments, such conditions may include a temperature ranging from 1350 to 1500.degree. C. and a pressure ranging from 4 to 7 GPa. When attaching a PCD body to a substrate, the PCD body may be placed such the surface intersecting the openings of the cavities is placed adjacent the substrate. Alternatively, the substrate may be formed during the attachment stage by placing powder for forming the substrate adjacent the surface intersecting the openings of the cavities, and sintering.

[0047] Thus, attachment or (reattachment) of the PCD body to a substrate may be achieved by placing the two pieces together and subjecting the two to sintering conditions to join the two bodies together. In embodiments in which the pathway openings are placed adjacent the substrate upper surface, during and due to the sintering conditions, some amount of carbide materials from the substrate may "bulge" into the open space of the cavities which have been formed in the PCD body, forming mechanical locking known in the art of non-planar interfaces. Alternatively, an intermediate material such as a refractory powder (tungsten or tungsten carbide powder in particular embodiments) may be used to fill at least a portion of the cavities in the PCD, such that the refractory powder will be sintered and bond together with the carbide substrate during the sintering conditions. In some embodiments, the intermediate material may also include diamond particles provided therewith such that a gradient may exist at the non-planar interface. In addition to a mechanical locking, the inclusion of diamond particles in the cavities may also allow for a chemical locking, through the formation of diamond-to-diamond bonds during the HPHT sintering process. Other intermediate materials may also be used.

[0048] In such embodiments, the substrate may have a substantially planar upper surface or may have a non-planar but non-mating upper surface. In the embodiment having the non-planar, but non-mating upper surface to the substrate, a diamond body may have a "larger" cavity than the projections that exist on the substrate upper surface. Thus, while the surfaces are non-mating (defined herein to mean that there is a gap of at least 10% of one dimension of the cavities between a surface of the diamond body and a surface of the substrate), the geometries would align based on location at the interface. Further, in such an embodiment, the intermediate material may be used to fill the gaps between the corresponding cavity and projection to aid in the attachment process. Yet another alternative may rely on addition of substrate precursors (a carbide powder and binder material, such as a Group VIII metal) to the PCD body, forming the substrate body during the attachment process.

[0049] Referring to FIGS. 4A-4C, collectively, an embodiment of the process steps of the present disclosure is shown. As shown in FIG. 4A, a polycrystalline diamond body 30 may be formed or provided. Alternatively, a polycrystalline diamond body 30 may be formed without a substrate. Formation of cavities 35 in the polycrystalline diamond body 30 may be achieved (in FIG. 4B) as described above. Further, as shown in FIG. 4C, the polycrystalline diamond body 30 may then be attached (or reattached) to a substrate 36 through sintering. During this attachment, the openings of cavities 35 are placed adjacent the substrate so that after reattachment sintering, a non-planar interface may be formed with a portion of substrate 37 filling any previously open space of cavities 35. As shown in FIG. 4C, the portion of substrate 37 filling the previously open space of cavities 35 may vary in some manner from the remaining portion of substrate 36. Such variations may result depending on the attachment technique selected. Specifically, when an intermediate material is used to fill at least a portion of cavities 35, the intermediate material may vary in some manner as compared to the preformed substrate being attached (or from precursor substrate materials). Such distinctions may lie in the binder content, powder type (e.g., tungsten or tungsten carbide alone or in combination with diamond powder) in amount, particle size, carbide type, etc. By using an intermediate material that varies from the remaining substrate, a gradient may be formed at the interface, as described above. Alternatively, the portion 37 of substrate may be identical to the remaining portion of substrate 36.

[0050] Referring to FIGS. 5A-5D, collectively, another embodiment of the process steps of the present disclosure is shown. As shown in FIG. SA, a polycrystalline diamond body 30 having a catalyzing material found in the interstitial regions between the diamond grains (as described above) may be formed attached to a carbide substrate 34. The polycrystalline diamond body 30 may be detached (shown in FIG. 5B) from the substrate 34 prior to formation of cavities 35 by techniques disclosed herein (shown in 5C). Further, as shown in FIG. 5D, the polycrystalline diamond body 30 may then be attached (or reattached) to a substrate 36 through sintering, and form a non-planar interface. In the embodiment shown in FIG. 5D, the portion 37 of substrate filling any previously open space of pathways 35 may be identical to the remaining portion of substrate 36.

[0051] Referring to FIGS. 6A-6E, collectively, yet another embodiment of the process steps of the present disclosure is shown. As shown in FIG. 6A, a polycrystalline diamond body 30 having a catalyzing material found in the interstitial regions between the diamond grains (as described above) may be formed attached to a carbide substrate 34. The polycrystalline diamond body 30 may be detached (shown in FIG. 6B) from the substrate 34 prior to formation of cavities 35 (shown in FIG. 6C) by techniques disclosed herein. Leaching of polycrystalline diamond body 30 removes at least a substantial portion of the catalyzing material from the interstitial regions, leaving a polycrystalline diamond body 32 (shown in FIG. 6D) having voids (other than cavities 35) dispersed in the diamond matrix or regions that were previously occupied by catalyzing material. Alternatively, leaching may occur prior to formation of cavities 35 in polycrystalline diamond body 30. Further, as shown in FIG. 6E, the polycrystalline diamond body 32 may then be attached (or reattached) to a substrate 36 through sintering, and form a non-planar interface. In the embodiment shown in FIG. 5D, the portion 37 of substrate filling any previously open space of pathways 35 may be identical to the remaining portion of substrate 36.

[0052] Embodiments of the present disclosure may provide for at least one of the following advantages. Conventional non-planar interfaces may be formed through formation of a geometrical surface in the substrate, and then placing diamond powder adjacent the geometrical surface to form a diamond layer having a mating surface during HPHT conditions. In accordance with embodiments of the present disclosure, a non-planar interface may be achieved by forming such geometrical surface in the diamond or other abrasive layer, and then attaching a substrate to the preformed diamond layer. Such methods may be particularly useful when a non-planar interface for a thermally stable cutting element formed by treating a "free-standing" PCD wafer is desired to increase the impact strength and reduce incidence of delamination.

[0053] While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

Claims

1. A method for forming a cutting element, comprising: forming at least one cavity in at least one surface of a polycrystalline abrasive body; placing the polycrystalline abrasive body adjacent a substrate such that an opening of at least one cavity is adjacent the substrate at an interface, wherein an interface surface of the substrate is non-mating with the polycrystalline abrasive body; and subjecting the polycrystalline abrasive body and substrate to high pressure/high temperature conditions.

2. The method of claim 1, wherein the polycrystalline abrasive body comprises at least one of polycrystalline diamond, polycrystalline diamond having at least a portion of catalyzing material removed therefrom, or polycrystalline cubic boron nitride.

3. The method of claim 2, wherein the portion of catalyzing material is removed before the forming.

4. The method of claim 2, wherein the portion of catalyzing material is removed after the forming.

5. The method of claim 1, further comprising: adding an intermediate material in at least a portion of the at least one cavity.

6. The method of claim 5, wherein the intermediate material comprises at least one of tungsten, tungsten carbide, or diamond powder.

7. The method of claim 1, wherein the opening of the at least one cavity is less than 3 mm in diameter.

8. The method of claim 7, wherein the opening of the at least one cavity is less than 1 mm in diameter.

9. The method of claim 8, wherein the opening of the at least one cavity is less than 50 microns in diameter.

10. The method of claim 1, wherein prior to placement adjacent the polycrystalline abrasive body, an upper surface of the substrate is substantially planar.

11. The method of claim 1, wherein prior to placement adjacent the polycrystalline abrasive body, an upper surface of the substrate is non-planar.

12. A method for forming a cutting element, comprising: forming a polycrystalline diamond compact of a polycrystalline diamond body attached to a substrate comprising: placing a mixture of diamond particles and a catalyst material adjacent a substrate; and subjecting the mixture and substrate to high-pressure/high temperature conditions; detaching the polycrystalline diamond body from the substrate; forming at least one cavity in at least one surface of the detached polycrystalline diamond body; placing the polycrystalline abrasive body adjacent a substrate material such that an opening of at least one cavity is adjacent the substrate material; and subjecting the polycrystalline abrasive body and substrate material to high temperature/high pressure conditions.

13. The method of claim 12, further comprising: removing at least a portion of the catalyst material from the polycrystalline diamond body.

14. The method of claim 12, further comprising: filling at least a portion of the at least one cavity with an intermediate material.

15. The method of claim 14, wherein the intermediate material comprises at least one of tungsten, tungsten carbide, or diamond powder.

16. The method of claim 12, wherein the opening of the at least one cavity is less than 3 mm in diameter.

17. The method of claim 16, wherein the opening of the at least one cavity is less than 1 mm in diameter.

18. A method for forming a cutting element, comprising: forming at least one cavity in at least one surface of a polycrystalline abrasive body; placing the polycrystalline abrasive body adjacent a substrate precursor material such that an opening of at least one cavity is adjacent the substrate precursor; and subjecting the polycrystalline abrasive body and substrate precursor materials to high pressure/high temperature conditions.

19. The method of claim 18, wherein the substrate precursor materials comprise a mixture of tungsten carbide powder and a Group VIII metal.

20. The method of claim 18, further comprising: contacting the polycrystalline abrasive body with a leaching agent.

21. The method of claim 18, wherein the opening of the at least one cavity is less than 3 mm in diameter.

22. The method of claim 21, wherein the opening of the at least one cavity is less than 1 mm in diameter.

23. A cutting element, comprising: a polycrystalline abrasive body; and a substrate attached to the polycrystalline abrasive body, wherein the polycrystalline abrasive body comprises, at the interface between the polycrystalline abrasive body and the substrate, at least one cavity formed therein, the at least one cavity having an opening with at least one dimension of less than 1 mm; and wherein the substrate comprises at least one projection mating the at least one cavity.

24. The cutting element of claim 23, wherein the wherein the polycrystalline abrasive body comprises at least one of polycrystalline diamond, polycrystalline diamond having at least a portion of catalyzing material removed therefrom, and polycrystalline cubic boron nitride.

25. The cutting element of claim 23, wherein the cavity comprises a channel extending through an entire thickness of the polycrystalline abrasive body.

26. The cutting element of claim 23, wherein the cavity extends a partial thickness into the polycrystalline abrasive body.

27. The cutting element of claim 23, wherein the opening has at least one dimension of less than 50 microns.

28. A cutting element, comprising: a polycrystalline abrasive body; and a substrate attached to the polycrystalline abrasive body, wherein the polycrystalline abrasive body comprises, at the interface between the polycrystalline abrasive body and the substrate, at least one cavity formed therein; and wherein the substrate comprises at least one projection mating the at least one cavity, the at least one projection comprising a material composition distinct from the remaining substrate.

29. The cutting element of claim 28, wherein the wherein the polycrystalline abrasive body comprises at least one of polycrystalline diamond, polycrystalline diamond having at least a portion of catalyzing material removed therefrom, and polycrystalline cubic boron nitride.

30. The cutting element of claim 28, wherein the cavity comprises a channel extending through an entire thickness of the polycrystalline abrasive body.

31. The cutting element of claim 28, wherein the cavity extends a partial thickness into the polycrystalline abrasive body.

32. The cutting element of claim 28, wherein the opening has at least one dimension of less than 50 microns.

33. The cutting element of claim 28, wherein the at least one projection comprises a binder content lower than the remaining substrate.

34. The cutting element of claim 28, wherein the at least one projection comprises hard particles distinct from the remaining substrate.

35. The cutting element of claim 28, wherein the at least one projection comprises a tungsten carbide and diamond composite.