Method of processing body of polycrystalline diamond material

Abstract

A method for leaching polycrystalline diamond (PCD) cutting elements, the method comprising: providing a leaching vessel having an internal volume; introducing a volume of a liquid acid leach mixture into the leach vessel, the volume being from about 5% to about 80% of the internal volume of the leach vessel; attaching the PCD cutting element to a jig; applying a sealing member around the PCD cutting element; positioning the jig to which the PCD cutting element is attached in the leaching vessel to suspend the PCD cutting element above the acid leaching mixture; sealing the leaching vessel to provide a closed system; raising the temperature of the liquid acid leach mixture above ambient conditions to convert at least some of the liquid acid leach mixture to one or more acid vapors; and exposing the PCD cutting element to the one or more acid vapors to leach the PCD cutting element.

Description

[0001] This disclosure relates to a method for processing a polycrystalline diamond (PCD) material body and a PCD structure processed in this way. Background Technology

[0002] Cutting inserts for machine tools and other tools typically include a layer of polycrystalline diamond (PCD) material bonded to a bonded carbide substrate. PCD is an example of an ultrahard material (also known as a super abrasive) with a hardness value far exceeding that of bonded tungsten carbide.

[0003] Components incorporating PCD are used in a wide variety of tools for cutting, machine tools, drilling, or degrading hard or abrasive materials such as rock, metals, ceramics, composites, and wood. PCD comprises a large number of substantially inter-grown (inter-grown) diamond grains that form a framework material defining the spaces between the diamond grains. PCD materials typically contain at least about 80% by volume diamond and can be produced by subjecting the aggregated diamond grains to ultra-high pressures, typically about 5.5 GPa or greater, and temperatures of at least about 1200°C, typically about 1440°C, in the presence of a sintering aid (also known as a solvent catalyst material for diamond). The solvent catalyst material for diamond should be understood as a material that promotes the direct inter-grown diamond grains under pressure and temperature conditions under which diamond is thermodynamically more stable than graphite.

[0004] Examples of solvent catalyst materials used for diamond are cobalt, iron, nickel, and certain alloys (including alloys of any of these elements). The PCD can be formed on, for example, a cobalt-bonded tungsten carbide substrate, which can provide a source of cobalt catalyst material for the PCD. During the sintering of the PCD material mass, components of the bonded carbide substrate (such as cobalt from the cobalt-bonded tungsten carbide substrate) liquefy and are swept from regions adjacent to the volume of the diamond particles into the interstitial regions between the diamond particles. In this example, cobalt is used as a solvent catalyst to promote the formation of bonded diamond grains. Alternatively, the metal-solvent catalyst can be mixed with the diamond particles before subjecting the diamond particles and substrate to the HPHT process. The interstitial spaces within the PCD material can be at least partially filled with the solvent catalyst material. Thus, the intergrown (bonded) diamond structure comprises the original diamond grains and newly precipitated or regrown diamond phases bridging the original grains. In the final sintered structure, the catalyst / solvent material is typically retained within at least some of the interstitial spaces between the sintered diamond grains.

[0005] Sintered PCD typically possesses sufficient wear resistance and hardness for applications involving abrasive wear, cutting, and drilling. However, a well-known problem with this type of PCD composite or cutting element is that the presence of residual solvent catalyst material in the microstructure interstices can adversely affect the performance of the PCD composite at high temperatures, as the presence of solvent catalyst in the diamond wafer is believed to reduce the thermal stability of the diamond wafer at these elevated temperatures. For example, the difference in the coefficient of thermal expansion between the diamond grains and the residual solvent / catalyst is thought to cause the PCD wafer of the cutting element to fragment or crack during drilling or cutting operations, where operating temperatures can reach 700°C or higher. Fragmentation or cracking in the PCD material can reduce the mechanical properties of the cutting element or lead to its failure. Additionally, at high temperatures, diamond grains may undergo chemical decomposition or reverse transformation with the solvent catalyst. At extremely high temperatures, some diamond grains may transform into carbon monoxide, carbon dioxide, graphite, or combinations thereof, thereby reducing the mechanical properties of the PCD material.

[0006] A potential solution to these problems is to remove the residual solvent catalyst (also known as the binder phase) from the PCD material.

[0007] Chemical leaching is frequently used to remove metal solvent catalysts, such as cobalt, from interstitial regions of the PCD material, such as those adjacent to the working surface of the PCD. Effectively removing most of the metal solvent catalyst from PCD flakes, especially from the thicker PCD flakes required for current applications, is typically very difficult and time-consuming. Generally, current techniques focus on achieving high diamond density PCDs and correspondingly PCDs with very fine distributions of metal solvent catalyst pools. This fine network typically resists the penetration of leaching agents, resulting in residual solvent catalyst often remaining in the leached composite. Furthermore, achieving considerable leaching depth can be so time-consuming as to be commercially impractical, or requires undesirable interventions such as extreme acid treatment or physical drilling of the PCD flakes.

[0008] A common method for removing catalysts from PCD materials is leaching the PCD material to remove some or virtually all of the interstitial catalyst from the PCD lattice structure, thereby transforming the PCD material into a more thermally stable polycrystalline diamond material. Leaching typically involves placing the cutting element in a strong acid bath at elevated temperatures to expose the PCD sheet to the acid. Typical suitable acids for leaching include nitric acid, sulfuric acid, hydrofluoric acid, hydrochloric acid, and combinations thereof. While such leaching acids can help remove catalysts from the PCD material, they can also damage the underlying substrate to which the PCD sheet is attached, and appropriate sealing is required to protect the substrate from such damage. Conventional leaching techniques using acid baths are relatively time-consuming and can take days or weeks to remove a sufficient amount of residual solvent catalyst from the PCD material. This increases the total time and associated costs of manufacturing the cutting element and the fixed cutting drill bit in which such a cutter is located during use.

[0009] Therefore, a technique for handling or processing PCD material bodies is needed to overcome or substantially improve the above-mentioned problems. Summary of the Invention

[0010] From a first perspective, a method is provided for leaching a polycrystalline diamond (PCD) cutting element having a non-diamond phase comprising a solvent catalyst material, the method comprising:

[0011] (a) Provide an leaching container with internal volume;

[0012] (b) Introducing a certain volume of liquid acid leaching mixture into the leaching container, the volume being about 5% to about 80% of the internal volume of the leaching container;

[0013] (c) Attach the PCD cutting element to the fixture;

[0014] (d) Apply a sealing member around the PCD cutting element;

[0015] (d) Position the fixture with the PCD cutting element attached in the leaching container to suspend the PCD cutting element above the acid leaching mixture;

[0016] (e) Seal the leaching container to provide a closed system;

[0017] (f) Raising the temperature of the liquid acid leaching mixture above ambient conditions to convert at least some of the liquid acid leaching mixture into one or more acid vapors; and

[0018] (g) Exposing the PCD cutting element to one or more acid vapors to leach the PCD cutting element.

[0019] From a second perspective, a polycrystalline diamond structure is provided, which is processed according to the method defined above to remove residual solvent catalyst material from at least a portion of the interstitial space between interlocking diamond grains. Attached Figure Description

[0020] The various variations will now be described in more detail by way of example, with reference to the accompanying drawings, in which:

[0021] Figure 1 This is a schematic perspective view of a PCD cutter insert for a cutting drill bit used to drill into the ground;

[0022] Figure 2 yes Figure 1 A schematic cross-sectional view of a portion of the PCD cutter insert, showing it before processing. Figure 1 The microstructure of PCD material in PCD cutter inserts;

[0023] Figure 3 This is a schematic partial cross-sectional view of an example of a system for vapor leaching PCD cutting elements based on the principles disclosed herein; and

[0024] Figure 4 This is a schematic flowchart illustrating an example of a method for leaching PCD cutting elements based on the principles disclosed herein.

[0025] In all the accompanying drawings, the same reference numerals refer to the same corresponding features. Detailed Implementation

[0026] This disclosure pertains to methods for processing superabrasive products such as superabrasive cutting elements, superabrasive bearings, and superabrasive discs. The superabrasive products disclosed herein can be used in a variety of applications, such as drilling tools (e.g., composite discs, cutting elements, gauge dressers, etc.), machine tools, bearing assemblies, wire drawing machinery, and other devices.

[0027] As used in this article, "superhard materials," also known as "super abrasive" materials, are materials with a Vickers hardness of at least about 28 GPa. Diamond and cubic boron nitride (cBN) are examples of superhard or super abrasive materials.

[0028] As used herein, "superhard structure" or "superabrasive structure" refers to a structure or composite sheet comprising a polycrystalline superhard or superabrasive material body. In such a structure, a substrate may be attached thereto, or alternatively, the polycrystalline material body may be free-standing and unsupported.

[0029] As used herein, polycrystalline diamond (PCD) is a polycrystalline superhard (PCS) material comprising a large number of diamond grains, most of which are directly bonded to each other, and wherein the diamond content is at least about 80% by volume of the material. In one example of a PCD material, the gaps between the diamond grains may be at least partially filled with a binder material comprising a solvent catalyst for diamond. As used herein, a “gap” or “gap region” is a region between the diamond grains of a PCD material. In examples of PCD materials, the gaps or gap regions may be substantially or partially filled with a material other than diamond, or they may be substantially empty. A PCD material may include at least one region from which the catalyst material has been removed from the gap, thereby leaving gap voids between the diamond grains.

[0030] "Catalyst materials" used in superhard materials can promote the growth or sintering of superhard materials.

[0031] As used herein, the term "substrate" means any substrate on which an ultra-hard material layer is formed. For example, as used herein, "substrate" can be a transition layer formed on another substrate.

[0032] As used herein, the term “integral” refers to regions or parts that are adjacent to each other and are not separated by different kinds of materials.

[0033] As used herein, the term "molar concentration" can refer to a concentration in mol / L at a temperature of approximately 25°C. For example, a solution containing solute A with a molar concentration of 1 M can contain 1 mol of solute A per liter of solution.

[0034] As used herein, the term "leaching depth" or "leaching depth" refers to the distance from the outer surface of the PCD cutting element into the PCD cutting element to which the leaching acid penetrates during the leaching process to remove residual solvent catalyst.

[0035] In such Figure 1 In the example shown, the cutting element 1 includes a substrate 10 and a layered PCD material body 12 formed on the substrate 10. The substrate 10 may be formed of a hard material such as bonded tungsten carbide. The cutting element 1 may be mounted in a drill bit body such as a scraper drill bit body (not shown) and may be suitable, for example, as a cutting insert for a drill bit used for drilling into the soil.

[0036] The exposed top surface of the superhard material opposite the substrate forms a cutting surface 14, which is the surface that is cut together with its edge 16 during use.

[0037] At one end of the substrate 10 is an interface surface 18 that forms an interface with the PCD material body 12, to which the PCD material body is attached. Figure 1 As shown in the example, the substrate 10 is typically cylindrical and has a peripheral surface 22 and a peripheral top edge 20.

[0038] As used herein, a PCD grade is a PCD material characterized by the volume content and size of diamond grains, the volume content of interstitial regions between diamond grains, and the composition of materials that may be present in the interstitial regions. A grade of PCD material can be manufactured by providing an aggregated material having diamond grains of a size distribution suitable for the grade, optionally introducing a catalyst material or additive material into the aggregated material, and subjecting the aggregated material to pressures and temperatures at which diamond is more thermodynamically stable than graphite and the catalyst material is molten, in the presence of a source of catalyst material for diamond. Under these conditions, the molten catalyst material may infiltrate from the source into the aggregated material and may promote direct inter-growth between diamond grains during sintering to form a PCD structure. The aggregated material may comprise loose diamond grains or diamond grains held together by a binder material, and the diamond grains may be natural or synthetic diamond grains.

[0039] Different PCD grades may have different microstructures and different mechanical properties, such as elastic (or Young's) modulus E, elastic modulus, transverse fracture strength (TRS), toughness (such as so-called K1C toughness), hardness, density, and coefficient of thermal expansion (CTE). Different PCD grades may also behave differently in use. For example, different PCD grades may have different wear rates and fracture resistance.

[0040] All PCD grades may include interstitial regions filled with a material containing cobalt metal, an example of a solvent catalyst material used for diamond.

[0041] PCD structure 12 may include one or more PCD levels.

[0042] Figure 2 It is a cross-section penetrating the PCD material body, which can form the exemplary cutting element 1. Figure 1 The superhard layer 12. During the formation of a conventional polycrystalline diamond structure, diamond grains 23 are directly bonded to adjacent grains, and the gaps 24 between the diamond grains 23 can be at least partially filled with a non-superhard phase material. This non-superhard phase material, also known as a filler material, may include residual solvent catalyst materials, such as cobalt, nickel, or iron.

[0043] According to some examples of the method, a sintered PCD material body 12 is produced, which has diamond-to-diamond bonding and a second phase comprising a solvent catalyst material dispersed in at least a portion of its microstructure. The PCD material body 12 forming the cutting element 1 and the attached substrate 10 can be formed using HPHT conditions according to standard methods to produce a sintered composite sheet. For example, the PCD layer 12 can be formed by subjecting a plurality of diamond particles (e.g., diamond particles with an average particle size between about 0.5 μm and about 150 μm) to an HPHT sintering process in the presence of a metal solvent catalyst (such as cobalt, nickel, iron and / or any other suitable Group VIII element). During the HPHT sintering process, adjacent diamond grains among the numerous diamond particles can bond together to form a PCD sheet (PCD material body 12) containing interbonded diamond grains. In one example, the diamond grains in the sheet 12 may have an average grain size of about 20 μm or less. In addition, during the HPHT sintering process, diamond grains can bond to the adjacent substrate 10 at the interface 18.

[0044] In various examples, the substrate 10 is formed of a bonded tungsten carbide material, and after sintering, the resulting PCD material body 12 may contain tungsten and / or tungsten carbide in addition to diamond grains and residual solvent catalyst material. For example, tungsten and / or tungsten carbide can be swept from the substrate 10 into the PCD layer 12 during HPHT sintering because during HPHT sintering, the liquefied solvent catalyst from the substrate 10 (e.g., cobalt from a cobalt-bonded tungsten carbide substrate) can dissolve and / or carry tungsten and / or tungsten carbide from the substrate 10 into the large number of diamond particles used to form the PCD sheet 12. In another example, tungsten and / or tungsten carbide particles may be intentionally mixed with diamond particles before forming the PCD material body 12.

[0045] It has been found that, in various applications, removal of the binder-free phase from PCD wafers (conventionally referred to as leaching) is desirable. One reason for this is that the presence of residual solvent catalyst material in the microstructure interstices is thought to have an adverse effect on the performance of PCD composites at high temperatures, as the presence of solvent catalyst in the diamond wafer is believed to reduce the thermal stability of the diamond wafer at these elevated temperatures.

[0046] To improve the performance and heat resistance of the surface region of the PCD material body 12, at least a portion of the metal-solvent catalyst (such as cobalt) is removed from at least a portion of the gaps 24 in the PCD material body 12. Additionally, in some examples, tungsten and / or tungsten carbide may be removed from at least a portion of the PCD material body 12.

[0047] Chemical leaching is typically used to remove residual solvent catalyst from the PCD material body 12 at a desired depth, extending to or from substantially all of the PCD material body 12. Therefore, after leaching, the PCD material body 12 may include a first volume that is substantially free of solvent catalyst material. However, small amounts of solvent catalyst material may remain in gaps inaccessible during the leaching process. Additionally, after leaching, the PCD material body 12 may also include a volume or region containing solvent catalyst material. In some instances, this additional volume may be located away from one or more exposed surfaces of the PCD material body 12.

[0048] Interstitial materials, which may include, for example, metal solvent catalysts and one or more additives in the form of carbide additives, can be leached from the interstitial 24 in the PCD material body 12 by exposing the PCD material to an exemplary leaching mixture (e.g., in liquid or vapor form).

[0049] The PCD region 12 of the PCD composite sheet 1 to be leached by the method typically, but not exclusively, can have a thickness of about 1.5 mm to about 4 mm.

[0050] Figure 3 This is a schematic partial cross-sectional view of an example of a system 30 for vapor leaching a PCD cutting element 1, based on the principles disclosed herein. System 30 includes a leaching vessel 32, and in some instances, a liner 34 may be located within the leaching vessel. The liner may be acid-resistant to protect the interior of the leaching vessel 32 from the leaching acid mixture disposed within the vessel. Generally, the liner 34 can be made of any material suitable for use with the leaching acid mixture for an extended period of time at the relatively high temperatures experienced during the leaching process described in more detail below. Examples of suitable materials for the liner 34 may include, but are not limited to, fluoropolymers such as PTFE.

[0051] A certain volume of liquid acid leaching mixture 36 is inserted into leaching container 32. In some examples, the volume is about 5% to about 80% of the internal volume of leaching container 32. In other examples, the volume is about 50% of the internal volume of leaching container 32.

[0052] The PCD cutting element 1 is attached to the clamp 38. A sealing member 40 is applied around the peripheral edge of the cutting element 1, thereby exposing a portion of the surface of the PCD material body 12 of the cutting element. The clamp 38 with the PCD cutting element 1 attached is located in the leaching container 32 to suspend and space the PCD cutting element 1 above and from the acid leaching mixture 36. The leaching container 32 is sealed to the top clamp 38, thereby providing a closed system. In some instances, a threaded connection or other mechanical locking mechanism can be used to connect the top clamp 38 to the leaching container 32 to close the system 30. Threaded connections or connections can have the advantage of providing a uniformly distributed load during the assembly process and throughout the leaching cycle. However, alternative mechanical mechanisms, such as clamping or bolted connections, can be used.

[0053] To process the PCD cutting element to leach residual solvent catalyst from at least a portion thereof, system 30 is heated above ambient conditions, such as to about 100°C to about 300°C, to convert at least some of the liquid acid leaching mixture into one or more acid vapors. In some instances, the temperature is about 140°C to about 200°C, and in other instances, it is about 145°C to about 180°C. The exposed surfaces of the PCD material body 12 of the PCD cutting element 1 are spaced apart from the acid leaching mixture and exposed to one or more acid vapors, which leach non-diamond phase components from the PCD material body 12.

[0054] In some instances, the sealing member 40 around the PCD cutting element is an O-ring seal extending around the PCD cutting element to protect the substrate 10 from one or more acid vapors. This sealing member 40 can provide both mechanical and chemical protection of the unexposed portions of the PCD cutting element from acid vapors and can also be used to control the form of the leaching profile obtained in the PCD material body 12. Exemplary materials suitable for forming the sealing member 40 may include fluoroelastomers, such as fluorocarbon-based rubbers (including, for example, Viton VI780 grade FKM). TM O-rings). Other examples include, but are not limited to, those made from perfluoroelastomer compounds (FFKM).

[0055] like Figure 3 As shown, in the closed system configuration, the sealing member 40 is disposed in a mating annular groove 42 near the free-opening end of the clamp 38 to form an annular seal around the outer peripheral surface of the PCD material body 12. The sealing member 40 also contacts the leaching container 32 at the connection with the clamp 38 to provide an additional sealing mechanism for the system 30 in the assembled configuration.

[0056] Similarly, Figure 3As shown in the example, the fixture 38 suspends the PCD cutting element 1 above the acid leaching mixture 36, with the PCD material 12 of the cutting element 1 facing the acid leaching mixture 36 but spaced apart from it.

[0057] A suitable acid leaching mixture 36 for use in system 30 may include, for example, an acid leaching mixture comprising, in molar concentrations of about 4 M to about 9 M, any one or more of hydrochloric acid (HCl), hydrofluoric acid (HF), nitric acid (HNO3), sulfuric acid (H2SO4), and / or phosphoric acid (H3PO4), and water. In some instances, acid leaching mixture 36 may comprise, in molar concentrations of about 4 M to about 9 M, nitric acid, and water. In still other instances, acid leaching mixture 36 may be used comprising, in molar concentrations of about 5 M to about 7 M, nitric acid, and water, in molar concentrations of about 6.7 M to about 8 M. The water may be deionized water. In some instances, hydrofluoric acid comprises about 10 vol% to about 30 vol% of the acid mixture, nitric acid or one or more other acids comprises about 30 vol% to about 60 vol% of the acid mixture, and water comprises about 20 vol% to about 50 vol% of the mixture.

[0058] One or both of the clamp 38 and the leaching container 32 may be made of, for example, stainless steel, or any suitable material capable of withstanding the high temperatures within the leaching container 32 during the leaching process, which is described in more detail below.

[0059] Figure 4This is a flowchart of an exemplary method 1000 for processing a PCD material body 12. Method 1000 will be described as being performed using the previously described system 30; however, it should be understood that method 1000 can be performed using other suitable containers or containers while still conforming to the principles disclosed herein. As shown in this figure, and as indicated by 1002, a liquid acid mixture (e.g., acid 36) is placed within the leaching container 32 to a level below its open end 46. The acid leaching mixture can be any suitable acid for leaching the PCD material body, including but not limited to any of the leaching acid mixtures previously described. At stage 1010, the PCD cutting element 1 is positioned in a fixture 38, and a sealing member 40 is positioned around a portion of the peripheral side surface of the PCD material body to be leached. Stage 1010 can occur before or after stage 1002. In stage 1020, the system 30 is then sealed by attaching the clamp 38 holding the PCD cutting element 1 to the leaching container 32 via a threaded connection, thereby causing partial compression of the sealing member 40 to further seal the system 30. In the closed configuration, the cutting element 1 is suspended within the leaching container 32, above and spaced from the liquid acid mixture 36, such that the cutting element 1 does not contact the liquid acid mixture. In stage 1040, the temperature within the leaching container 32 is raised, causing at least a portion of the acid mixture 36 to begin evaporating and leaching the PCD material body of the cutting element 1. The substrate 10 of the cutting element is protected from one or more leaching acid vapors by the sealing member 40 or other suitable means.

[0060] In stage 1040 of method 1000, the elevated temperature within the leaching vessel 32 is maintained for a period of time to enable the PCD material mass to be leached to the desired leaching depth. Figure 3 As shown, the PCD material body to be leached is at least partially exposed and suspended above the acid leaching mixture 36. Therefore, the cutting element 1 does not directly contact the liquid acid mixture 36 during the leaching process in stage 1040.

[0061] In stage 1040, the temperature of system 30 is increased to begin the conversion of the acid leaching mixture 36 from liquid to vapor in the leaching vessel 32. Any suitable technique or apparatus known in the art can be used to increase the temperature. For example, a heating element can be attached to or placed in contact with the outer surface of the leaching chamber 32 such that the heat generated by the heating element can raise the temperature inside the leaching vessel 32. The temperature of the leaching vessel 32 during the leaching process can be, for example, from about 100°C to about 300°C.

[0062] During stage 1040, one or more acid vapors of the acid leaching mixture in the leaching vessel 32 come into contact with the exposed PCD material body 12 of the PCD cutting element 1 held within the fixture 38, but the acid vapors are restricted and / or prevented from contacting the substrate 10 via the sealing member 40. Heating the leaching vessel 32 and / or directly heating the acid leaching mixture 36 therein, and maintaining the acid leaching mixture 36 at a selected temperature during the leaching process, may be advantageous as it is believed to help maintain the integrity of the sealing member 40.

[0063] After exposure to the acid leaching mixture for the desired duration, the PCD material body is rinsed to remove any residual acid leaching mixture, such as... Figure 4 As illustrated in step 1200. The rinsing step may include cooling the leaching container after the step of exposing the PCD cutting element to one or more acid vapors to leach the PCD cutting element, removing residual acid leaching mixture from the leaching container, and then rinsing, for example, with deionized water to remove residual acid leaching mixture from the PCD cutting element 1. The rinsing step may include introducing deionized water into the leaching container, sealing the leaching container in the same manner as the leaching process, and raising the temperature of the leaching container and / or the water therein for a sustained period of time to evaporate the water and rinse the PCD material. The rinsing step may be repeated multiple times with clean water as needed or necessary. The necessity of this can be determined by testing the pH of the waste water to determine its acidity. Multiple rinsing cycles may be required to achieve a pH of 5 or higher, meaning that the sample is safe for treatment (with PPE) before drying, for example, at about 60°C to about 90°C for several hours.

[0064] Some variations are described in more detail with reference to the examples below, which are not intended to be limiting. The examples below provide further details relating to the examples above.

[0065] Example 1

[0066] Cutting elements were formed by HPHT sintering diamond particles in the presence of cobalt, each cutting element comprising a PCD material body 12 attached to a tungsten carbide substrate 10. The sintered PCD material body includes cobalt in the interstitial regions between interbonded diamond grains. Each PCD material body 12 was leached using a leaching mixture comprising 44 vol% 6.7M nitric acid, 18 vol% 5M hydrofluoric acid, and 38 vol% deionized water. The processing technique used was vapor leaching, in which the cutting tool was placed in a separate leaching chamber and suspended above a certain amount of an exemplary acid leaching mixture, which filled approximately 50% of the leaching chamber volume. The chamber was sealed and heated to a temperature of approximately 180°C to evaporate at least a portion of the acid leaching mixture. The PCD material body was leached with acid vapor for 100 hours. At this time, the leaching depth of the PCD material body in different portions of the PCD sheet was determined by X-ray analysis. An average leaching depth of approximately 800 to approximately 1541 micrometers was found to have been achieved after 100 hours. This contrasts with an equivalent cutting element formed from the same PCD sheet attached to a tungsten carbide substrate leached using a conventional aqueous leaching technique according to a conventional leaching mixture. In this process, the PCD material to be leached is partially immersed in a conventional acid leaching mixture containing hydrofluoric acid (HF) and nitric acid (HNO3) diluted in water (HF:HNO3 (1:3)) and heated to approximately 40°C–70°C for approximately 100 hours to leach the PCD material. Using this technique, it was found that the PCD material thus leached had an average leaching depth of approximately 345 micrometers after 100 hours.

[0067] Example 2

[0068] Cutting elements were formed by HPHT sintering diamond particles in the presence of cobalt, each cutting element comprising a PCD material body 12 attached to a tungsten carbide substrate 10. The sintered PCD material body includes cobalt in the interstitial regions between interbonded diamond grains. Each PCD material body 12 was leached using a leaching mixture comprising 44 vol% 6.7M nitric acid, 18 vol% 5M hydrofluoric acid, and 38 vol% deionized water. The processing technique used was vapor leaching, in which the cutting tool was placed in a separate leaching chamber and suspended above a certain amount of an exemplary acid leaching mixture, which filled approximately 50% of the leaching chamber volume. The chamber was sealed and heated to a temperature of approximately 200°C to evaporate at least some of the acid leaching mixture. The PCD material body was leached with acid vapor for 100 hours. At this time, the leaching depth of the PCD material body in different portions of the PCD sheet was determined by X-ray analysis. An average leaching depth of approximately 800 to approximately 1133 micrometers was found to have been achieved after 100 hours.

[0069] Example 3

[0070] Cutting elements were formed by HPHT sintering diamond particles in the presence of cobalt, each comprising a PCD material body 12 attached to a tungsten carbide substrate 10. The sintered PCD material body includes cobalt in the interstitial regions between interbonded diamond grains. Each PCD material body 12 was leached using a leaching mixture comprising approximately 44 vol% 6.7M nitric acid, approximately 18 vol% 5M hydrofluoric acid, and approximately 38 vol% deionized water. The processing technique used was vapor leaching, in which the cutting tool was placed in a separate leaching chamber and suspended above a quantity of an exemplary acid leaching mixture filling approximately 50% of the leaching chamber volume. The chamber was sealed and heated to a temperature of approximately 200°C to evaporate at least some of the acid leaching mixture. The PCD material body was leached with acid vapor for 100 hours. At this time, the leaching depth of the PCD material body in different portions of the PCD sheet was determined by X-ray analysis. An average leaching depth of approximately 1023 micrometers was found to have been achieved after 100 hours.

[0071] Example 4

[0072] The same technique described above in Examples 1 to 3 was used to leach PCD cutters, each with a PCD material body 12 to be leached. However, in this example, a leaching mixture containing approximately 30-60 vol% 7.5M nitric acid, approximately 10-30 vol% 6.7M hydrofluoric acid, and the remaining vol% deionized water was used. The PCD material bodies were leached with acid vapor for 100 hours. At this time, the leaching depth of the PCD material body in different portions of the PCD sheet was determined by X-ray analysis. An average leaching depth of approximately 1029 micrometers was found to have been achieved after 100 hours.

[0073] Example 5

[0074] The same technique described above in Examples 1 to 3 was used to leach PCD cutters, each with a PCD material body 12 to be leached, but in this example, a leaching mixture containing approximately 40-50 vol% 8.5M nitric acid, approximately 10-20 vol% 8M hydrofluoric acid, and the remaining vol% deionized water was used. The PCD material bodies were leached with acid vapor for 100 hours. At this time, the leaching depth of the PCD material body in different portions of the PCD sheet was determined by X-ray analysis. It was found that an average leaching depth of approximately 894 micrometers had been achieved after 100 hours.

[0075] Example 6

[0076] The same technique described above in Examples 1 to 3 was used to leach PCD cutters, each with a PCD material body 12 to be leached, but in this example, a leaching mixture containing approximately 30-60 vol% 9.2M nitric acid, approximately 10-30 vol% 9.6M hydrofluoric acid, and the remaining vol% deionized water was used. The PCD material bodies were leached with acid vapor for 100 hours. At this time, the leaching depth of the PCD material body in different portions of the PCD sheet was determined by X-ray analysis. It was found that an average leaching depth of approximately 762 micrometers had been achieved after 100 hours.

[0077] Example 7

[0078] The same technique described above in Examples 1 to 3 was used to leach PCD cutters, each with a PCD material body 12 to be leached. However, in this example, a leaching mixture containing approximately 30-60 vol% 6.9M nitric acid, approximately 10-30 vol% 9.6M hydrofluoric acid, and the remaining vol% (approximately 10-50 vol%) deionized water was used. The PCD material bodies were leached with acid vapor for 100 hours. At this time, the leaching depth of the PCD material body in different portions of the PCD sheet was determined by X-ray analysis. An average leaching depth of approximately 824 micrometers was found to have been achieved after 100 hours.

[0079] When compared with the leaching depth achievable using conventional leaching solutions (such as a mixture of HCl and water or hydrofluoric acid (HF) and nitric acid diluted in water (HF:HNO3(1:3))), it is determined that examples including the above-mentioned leaching mixtures can enable greater leaching efficiency, wherein greater leaching depth can be achieved in a shorter time period, and in some cases, enable the desired leaching depth to be achieved approximately 4 to 6 times faster than using conventional acid leaching mixtures and processing techniques.

[0080] In addition to providing a system with an increased leaching rate compared to conventional liquid leaching techniques, another important consideration in the system 30 and method for leaching PCD bodies described herein is health and safety. It is believed that there is a risk of system explosion if an inappropriate amount of acid leaching mixture is used. It has been found that filling the leaching vessel with approximately 5% to approximately 80% of the acid leaching mixture volume, and in some instances approximately 50%, provides both an accelerated leaching rate compared to conventional aqueous acid leaching techniques in an acid bath, and potentially helps to reduce the health and safety risks associated with such potentially hazardous acids. It is understood that if the volume of the acid leaching mixture is too large, overpressure may occur in the leaching vessel. In the case of insufficient filling, a reduced leaching rate or leaching cessation may occur due to decreased reactant availability. Other factors to consider are the byproducts of the reaction during the leaching process, which, in the case of HF / HNO3 acid leaching mixtures with the properties described herein, are NOx vapors, and in addition to the generated reaction vapors, these byproducts may also increase the internal vapor pressure during the leaching process. While not wishing to be bound by any particular theory, it can be assumed that as the amount of NOx generated increases, it can push the pressure balance to force more reagent vapor into the liquid phase, thereby slowing down the leaching rate.

[0081] The foregoing description has been provided to enable others skilled in the art to best utilize the various aspects described herein by way of example. This description is not intended to be exhaustive or limited to any precise form disclosed. Many modifications and variations are possible. In particular, some exemplary methods can be equally applied to the efficient leaching of PCD with other additives or interstitial materials, such as those in the form of other metal carbides, including one or more carbides of tungsten, titanium, niobium, tantalum, zirconium, molybdenum, vanadium, or chromium.

Claims

1. A method for leaching a polycrystalline diamond (PCD) cutting element having a non-diamond phase comprising a solvent catalyst material, the method comprising: (a) providing a leaching vessel having an internal volume; (b) introducing a volume of a liquid acid leach mixture into the leaching vessel, the volume being from about 5% to about 80% of the internal volume of the leaching vessel; (c) attaching the PCD cutting element to a jig; (d) applying a sealing member around the PCD cutting element; (d) positioning the jig with the PCD cutting element attached in the leaching vessel to suspend the PCD cutting element above the acid leach mixture; (e) sealing the leaching vessel to provide a closed system; (f) increasing the temperature of the liquid acid leach mixture above ambient conditions to convert at least some of the liquid acid leach mixture into one or more acid vapors; and (g) exposing the PCD cutting element to the one or more acid vapors to leach the PCD cutting element. The volume of the acid leach mixture is from about 30% to about 60% of the internal volume of the leaching vessel.

2. The method of claim 1, wherein, The volume of the acid leach mixture is from about 40% to about 50% of the internal volume of the leaching vessel.

3. The method of claim 1, wherein, The step of increasing the temperature of the liquid acid leach mixture above ambient conditions to convert at least some of the liquid acid leach mixture into one or more acid vapors comprises heating the leach mixture to from about 100°C to about 300°C.

4. The method of any one of the preceding claims, wherein, The step of applying a sealing member around the PCD cutting element comprises applying an O-ring seal around the PCD cutting element to protect the substrate from the one or more acid vapors.

5. The method of any one of the preceding claims, wherein, The step of positioning the jig comprises positioning the jig to suspend the PCD cutting element above the acid leach mixture with the PCD material of the cutting element facing but spaced apart from the acid leach mixture.

6. The method of any one of the preceding claims, wherein, The step of introducing a volume of a liquid acid leach mixture into the leaching vessel comprises introducing an acid leach mixture having a molarity of from about 4M to about 9M, the mixture comprising any one or more of hydrochloric acid (HC1), hydrofluoric acid (HF), nitric acid (HNO3), sulfuric acid (H2SO4), and / or phosphoric acid (H3PO4) and water.

7. The method of any one of the preceding claims, wherein, The step of introducing a volume of a liquid acid leach mixture into the leaching vessel comprises introducing an acid leach mixture comprising hydrofluoric acid having a molarity of from about 4M to about 9M, nitric acid having a molarity of from about 4M to about 9M, and water.

8. The method of any one of the preceding claims, wherein, The step of introducing a volume of a liquid acid leach mixture into the leaching vessel comprises introducing an acid leach mixture comprising hydrofluoric acid having a molarity of from about 5M to about 7M, and nitric acid having a molarity of from about 6.7M to about 8M, and water.

9. The method of any one of the preceding claims, wherein, The water comprises deionized water.

10. The method of any one of claims 7 to 9, wherein, The step of sealing comprises sealing the jig holding the PCD cutting element to the leaching vessel.

11. The method of any one of the preceding claims, wherein, ​ 12. The method of any one of the preceding claims, wherein, The step of raising the temperature of the liquid acid leach mixture includes heating the leach vessel and / or the acid leach mixture therein directly, and maintaining the acid leach mixture at a selected temperature during the leach process.

13. The method of any one of the preceding claims, further comprising cooling the leach vessel after the step of exposing the PCD cutting element to the one or more acid vapors to leach the PCD cutting element.

14. The method of claim 13, further comprising removing residual acid leach mixture from the leach vessel.

15. The method of claim 14, further comprising rinsing the PCD cutting element to remove residual acid leach mixture therefrom.

16. The method of claim 15, wherein, The step of rinsing includes introducing deionized water into the leach vessel and raising the temperature of the leach vessel and / or the water therein to evaporate the water.

17. The method of any one of the preceding claims, wherein, The step of raising the temperature of the liquid acid leach mixture above ambient conditions to convert at least some of the liquid acid leach mixture to one or more acid vapors includes heating the leach mixture to between about 140°C and about 200°C.

18. The method of any one of the preceding claims, wherein, The step of raising the temperature of the liquid acid leach mixture above ambient conditions to convert at least some of the liquid acid leach mixture to one or more acid vapors includes heating the leach mixture to between about 145°C and about 180°C.

19. A polycrystalline diamond structure treated in accordance with any one of the preceding claims to remove solvent catalyst material from at least a portion of interstitial spaces between mutually bonded diamond grains.

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