BACKGROUND

Wear-resistant, superabrasive materials are traditionally utilized for a variety of mechanical applications. For example, polycrystalline diamond (“PCD”) materials are often used in drilling tools (e.g., cutting elements, gage trimmers, etc.), machining equipment, bearing apparatuses, wire-drawing machinery, and in other mechanical systems. Conventional superabrasive materials have found utility as superabrasive cutting elements in rotary drill bits, such as roller cone drill bits and fixed-cutter drill bits. A conventional cutting element may include a superabrasive layer or table, such as a PCD table. The cutting element may be brazed, press-fit, or otherwise secured into a preformed pocket, socket, or other receptacle formed in the rotary drill bit. In another configuration, the substrate may be brazed or otherwise joined to an attachment member such as a stud or a cylindrical backing. Generally, a rotary drill bit may include one or more PCD cutting elements affixed to a bit body of the rotary drill bit.

As mentioned above, conventional superabrasive materials have found utility as bearing elements in thrust bearing and radial bearing apparatuses. A conventional bearing element typically includes a superabrasive layer or table, such as a PCD table, bonded to a substrate. One or more bearing elements may be mounted to a bearing rotor or stator by press-fitting, brazing, or through other suitable methods of attachment. Typically, bearing elements mounted to a bearing rotor have superabrasive faces configured to contact corresponding superabrasive faces of bearing elements mounted to an adjacent bearing stator.

Cutting elements having a PCD table may be formed and bonded to a substrate using an ultra-high pressure, ultra-high temperature (“HPHT”) sintering process. Often, cutting elements having a PCD table are fabricated by placing a cemented carbide substrate, such as a cobalt-cemented tungsten carbide substrate, into a container or cartridge with a volume of diamond particles positioned on a surface of the cemented carbide substrate. A number of such cartridges may be loaded into a HPHT press. The substrates and diamond particle volumes may then be processed under HPHT conditions in the presence of a catalyst material that causes the diamond particles to bond to one another to form a diamond table having a matrix of bonded diamond crystals. The catalyst material is often a metal-solvent catalyst, such as cobalt, nickel, and/or iron, that facilitates intergrowth and bonding of the diamond crystals.

In one conventional approach, a constituent of the cemented-carbide substrate, such as cobalt from a cobalt-cemented tungsten carbide substrate, liquefies and sweeps from a region adjacent to the volume of diamond particles into interstitial regions between the diamond particles during the HPHT process. The cobalt may act as a catalyst to facilitate the formation of bonded diamond crystals. A metal-solvent catalyst may also be mixed with a volume of diamond particles prior to subjecting the diamond particles and substrate to the HPHT process.

The metal-solvent catalyst may dissolve carbon from the diamond particles and portions of the diamond particles that graphitize due to the high temperatures used in the HPHT process. The solubility of the stable diamond phase in the metal-solvent catalyst may be lower than that of the metastable graphite phase under HPHT conditions. As a result of the solubility difference, the graphite tends to dissolve into the metal-solvent catalyst and the diamond tends to deposit onto existing diamond particles to form diamond-to-diamond bonds. Accordingly, diamond grains may become mutually bonded to form a matrix of polycrystalline diamond, with interstitial regions defined between the bonded diamond grains being occupied by the metal-solvent catalyst. In addition to dissolving carbon and graphite, the metal-solvent catalyst may also carry tungsten, tungsten carbide, and/or other materials from the substrate into the PCD layer of the cutting element.

The presence of the metal-solvent catalyst and/or other materials in the diamond table may reduce the thermal stability of the diamond table at elevated temperatures. For example, the difference in thermal expansion coefficient between the diamond grains and the solvent catalyst is believed to lead to chipping or cracking in the PCD table of a cutting element during drilling or cutting operations. The chipping or cracking in the PCD table may degrade the mechanical properties of the cutting element or lead to failure of the cutting element. Additionally, at high temperatures, diamond grains may undergo a chemical breakdown or back-conversion with the metal-solvent catalyst. Further, portions of diamond grains may transform to carbon monoxide, carbon dioxide, graphite, or combinations thereof, thereby degrading the mechanical properties of the PCD material.

Accordingly, it is desirable to remove a metal-solvent catalyst from a PCD material in situations where the PCD material may be exposed to high temperatures. Chemical leaching is often used to dissolve and remove various materials from the PCD layer. For example, chemical leaching may be used to remove metal-solvent catalysts, such as cobalt, from regions of a PCD layer that may experience elevated temperatures during drilling, such as regions adjacent to the working surfaces of the PCD layer.

Conventional chemical leaching techniques often involve the use of highly concentrated and corrosive solutions, such as highly acidic solutions, to dissolve and remove metal-solvent catalysts from polycrystalline diamond materials. However, in addition to dissolving metal-solvent catalysts from a PCD material, leaching solutions may also dissolve any accessible portions of a substrate to which the PCD material is attached. For example, highly acidic leaching solutions may dissolve any accessible portions of a cobalt-cemented tungsten carbide substrate, causing undesired pitting and/or other corrosion of the substrate surface.

In some conventional leaching techniques, a polymeric leaching cup may be placed around a portion of a PCD element to protect the substrate from a leaching solution. A polymeric leaching cup may, for example, surround the substrate surface and a portion of the PCD layer near the substrate. Such leaching cups may not, however, provide adequate protection under various leaching conditions. It may be desirable to expose PCD articles to leaching solutions for varying periods of time and/or to expose the PCD articles to leaching solutions under various temperature and/or pressure conditions to obtain specified leach depths.

While various temperatures, pressures, and/or leach times may enable leaching of a PCD article to a desired degree, such conditions may undesirably cause portions of the substrate of the PCD article to be exposed to a leaching solution. For example, a leaching solution may pass between portions of the cup and the PCD article, resulting in portions of the substrate or other protected part of the PCD article being exposed to the leaching solution. Additionally, gases, such as air, may be trapped between a leaching cup and a PCD article when the cup is placed around the PCD article. During leaching, trapped gases may expand due to an increase in temperature and/or a decrease in pressure, pushing the PCD article out of the leaching cup and exposing a portion of the substrate or other protected part of the PCD article to the leaching solution. Such exposure to leaching solutions may result in undesired corrosion and/or damage to PCD substrates.

SUMMARY

The instant disclosure is directed to exemplary methods of processing polycrystalline diamond elements and leaching trays and protective leaching cups for arranging polycrystalline diamond elements and protecting portions of polycrystalline diamond elements from corrosion during leaching. In some embodiments, a method of processing a polycrystalline diamond element may comprise providing a polycrystalline diamond element having a cutting face, a rear face opposite the cutting face, and a side surface extending between the cutting face and the rear face. In at least one embodiment, the surface extending between the cutting face and the rear face may extend in a direction substantially parallel to a central axis of the polycrystalline diamond element. The polycrystalline diamond element may comprise a substrate and a polycrystalline diamond table bonded to the substrate.

The method may additionally comprise positioning the polycrystalline diamond element within a protective leaching cup. The protective leaching cup may include a seal region contacting a portion of the side surface of the polycrystalline diamond element adjacent the cutting face. The protective leaching cup may further include an encapsulating region surrounding the rear face and a portion of the side surface of polycrystalline diamond element adjacent the rear face. A length of a side wall of the protective leaching cup may exceed a length of the side surface of the polycrystalline diamond element. For example, the length of the side wall of the protective leaching cup may exceed the length of the side surface of the polycrystalline diamond element in the direction substantially parallel to the central axis of the polycrystalline diamond element

The method may also comprise exposing at least a portion of the polycrystalline diamond element to a leaching agent. Exposing at least the portion of the polycrystalline diamond element to the leaching agent may comprise submerging at least the portion of the polycrystalline diamond element and at least a portion of the protective leaching cup in the leaching agent.

In at least one embodiment, the protective leaching cup may comprise an extension region extending between the seal region and an opening of the protective leaching cup. The extension region may not contact the side surface of the polycrystalline diamond element. In certain embodiments, at least one of the extension region of the protective leaching cup and the encapsulating region of the protective leaching cup may have an inner diameter that is greater than an inner diameter of the seal region of the protective leaching cup. According to some embodiments, the seal region may further comprise a seal contact portion contacting a portion of the side surface of the polycrystalline diamond element and an extension portion extending between the seal contact portion and an opening of the protective leaching cup. The seal contact portion and the extension portion may have substantially the same inner diameter.

In at least one embodiment, a gap may be defined between the encapsulating region of the protective leaching cup and at least one of the side surface and the rear face of the polycrystalline diamond element. A wall of the seal region of the protective leaching cup may have a greater thickness than a wall of the encapsulating region of the protective leaching cup. Additionally, the encapsulating region of the protective leaching cup may have an inner diameter that is greater than an inner diameter of the seal region of the protective leaching cup.

According to various embodiments, exposing at least the portion of the polycrystalline diamond element to the leaching agent may comprise heating the leaching agent. The method may further comprise forcing at least a portion of the seal region of the protective leaching cup away from the side surface of the polycrystalline diamond element prior to exposing at least the portion of the polycrystalline diamond element to the leaching agent. In some embodiments, forcing at least the portion of the seal region of the protective leaching cup away from the side surface of the polycrystalline diamond element may comprise inserting a portion of an expansion apparatus through an opening of the protective leaching cup.

According to at least one embodiment, inserting the portion of the expansion apparatus through the opening of the protective leaching cup may comprise contacting the protective leaching cup adjacent the opening with the portion of the expansion apparatus. The portion of the expansion apparatus contacting the extension portion of the protective leaching cup may have a width that is greater than the inner diameter of the portion of the protective leaching cup. The expansion apparatus may comprise at least one sloped portion. In some embodiments, inserting the portion of the expansion apparatus through the opening of the protective leaching cup may further comprise forcing the at least one sloped portion of the expansion apparatus against a portion of the protective leaching cup adjacent the opening.

According to certain embodiments, the side surface of the polycrystalline diamond element may comprise a substantially cylindrical surface. The seal region of the protective leaching cup may have a substantially cylindrical inner surface corresponding to the substantially cylindrical outer surface of the polycrystalline diamond element. The seal region of the protective leaching cup may tightly surround at least the portion of the side surface of the of the polycrystalline diamond element so as to form a seal between the seal region and the side surface.

In some embodiments, the protective leaching cup may be heated prior to positioning the polycrystalline diamond element within the protective leaching cup. In additional embodiments, at least a portion of the polycrystalline diamond element may be mechanically and/or chemically smoothed prior to positioning the polycrystalline diamond element within the protective leaching cup.

According to at least one embodiment, a protective leaching cup for processing a polycrystalline diamond element may comprise a rear wall, an opening defined in a portion of the protective leaching cup opposite the rear wall, and a side wall extending between the opening and the rear wall, the side wall and the rear wall defining a cavity within the protective leaching cup. The protective leaching cup may comprise a polymer material. The side wall of the protective leaching cup may comprise a seal region adjacent the opening of the protective leaching cup, the seal region having a first inner diameter, and an encapsulating region extending between the seal region and the rear wall, the encapsulating region having a second inner diameter that is greater than the first inner diameter. At least one of the seal region and the encapsulating region may have a substantially cylindrical inner periphery.

In at least one embodiment, a leaching assembly for processing a polycrystalline diamond element may comprise a polycrystalline diamond element and a protective leaching cup. The polycrystalline diamond element may include a cutting face, a rear face opposite the cutting face, and a side surface extending between the cutting face and the rear face. The polycrystalline diamond element may be positioned within the protective leaching cup and the protective leaching cup may comprise a seal region contacting a portion of the side surface of the polycrystalline diamond element adjacent the cutting face and an encapsulating region surrounding the rear face and a portion of the side surface of the polycrystalline diamond element adjacent the rear face. A length of a side wall of the protective leaching cup may exceed a length of the side surface of the polycrystalline diamond element. In certain embodiments, the leaching assembly may comprise a leaching tray that includes a tray body having a front surface and a back surface opposite the front surface and a hole defined within the tray body, the hole extending through the tray body from an opening formed in the front surface to an opening formed in the back surface, the protective leaching cup being disposed within the hole.

In various embodiments, a method of processing a polycrystalline diamond element may comprise providing a particulate mixture comprising diamond particles and sintering the particulate mixture to form a polycrystalline diamond element. The method may additionally comprise smoothing at least a portion of a peripheral surface of the polycrystalline diamond element, positioning a sealing structure adjacent to a smoothed portion of the peripheral surface of the polycrystalline diamond element, and exposing at least a portion of the polycrystalline diamond element to a leaching agent. Smoothing at least the portion of the peripheral surface of the polycrystalline diamond element may include at least one of mechanically smoothing and chemically smoothing at least the portion of the peripheral surface of the polycrystalline diamond element.

Features from any of the described embodiments may be used in combination with one another in accordance with the general principles described herein. These and other embodiments, features, and advantages will be more fully understood upon reading the following detailed description in conjunction with the accompanying drawings and claims.

