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.
Cutting elements that have a superabrasive layer or a PCD table may be formed and bonded to a substrate using an ultra-high pressure, ultra-high temperature (“HPHT”) sintering process to form a polycrystalline diamond compact (“PDC”). Often, cutting elements that have 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. The substrate and diamond particle volumes may then be processed under diamond-stable HPHT conditions in the presence of a catalyst material, which causes the diamond particles to bond to one another to form a diamond table having a matrix of bonded diamond grains. The catalyst material is often a metal-solvent catalyst, such as cobalt, nickel, or iron, which facilitates intergrowth and bonding of the diamond crystals. The catalyst may come from the cemented-carbide substrate, such as cobalt from a cobalt-cemented tungsten carbide substrate, which 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 presence of the metal-solvent catalyst and/or other materials in the diamond table may reduce a thermal stability of the diamond table at elevated temperatures. For example, a difference in the thermal expansion coefficient between the diamond grains and the metal-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 when the PCD table or material may be exposed to high temperatures.
Chemical leaching is often used to dissolve and remove the metal-solvent catalyst from the PCD table. Conventional chemical leaching techniques often involve the use of highly concentrated and corrosive leaching solutions, such as highly acidic solutions, to dissolve and remove metal-solvent catalysts from polycrystalline diamond materials.
However, the leaching solutions may dissolve any accessible portions of the substrate to which the PCD table is attached. For example, highly acidic leaching solutions may dissolve any accessible portions of the cobalt-cemented tungsten carbide substrate, causing undesired pitting and/or other corrosion of the substrate surface.
U.S. patent application Ser. No. 14/084,058, entitled “Protective Leaching Cups, Systems, and Methods of Use,” filed on 19 Nov. 2013, discloses that a polymeric leaching cup may be placed around a portion of a PCD element or layer to protect the substrate from the leaching solutions. The polymeric leaching cup may, for example, surround the substrate surface and a portion of the PCD layer near the substrate. The entire disclosure of the U.S. patent application Ser. No. 14/084,058 is incorporated herein by reference.
U.S. patent application Ser. No. 14/084,058 also discloses an expansion apparatus for positioning a superabrasive element within a protective leaching cup and/or for expanding a portion of the protective leaching cup to at least partially evacuate gas(es) trapped between the superabrasive element and the protective leaching cup by expanding or bending a top portion of the protective leaching cup. The gas(es), such as air, may be trapped between the protective leaching cup and a PDC when the cup is placed around the PDC. During leaching, trapped gas(es) may expand due to an increase in temperature and/or a decrease in pressure, pushing the PDC out of the leaching cup and exposing a portion of the substrate or other protected part of the PDC to the leaching solution. Such exposure to leaching solutions may result in undesired corrosion and/or damage to the substrate.
Therefore, manufactures and users of PDCs continue to seek improved PDC processing techniques.