Patent Publication Number: US-10760344-B1

Title: Polycrystalline diamond compacts and methods of fabricating same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/199,571 filed on 6 Mar. 2014, which claims priority to U.S. Provisional Application No. 61/776,884 filed on 12 Mar. 2013, the disclosure of each of the foregoing applications is incorporated herein, in its entirety, by this reference. 
    
    
     BACKGROUND 
     Wear-resistant, polycrystalline diamond compacts (“PDCs”) are utilized in a variety of mechanical applications. For example, PDCs are used in drilling tools (e.g., cutting elements, gage trimmers, etc.), machining equipment, bearing apparatuses, wire-drawing machinery, and in other mechanical apparatuses. 
     PDCs have found particular utility as superabrasive cutting elements in rotary drill bits, such as roller-cone drill bits and fixed-cutter drill bits. A PDC cutting element typically includes a superabrasive diamond layer commonly known as a diamond table. The diamond table is formed and bonded to a substrate using a high-pressure/high-temperature (“HPHT”) process. The PDC cutting element may also be brazed directly into a preformed pocket, socket, or other receptacle formed in a bit body. The substrate may optionally be brazed or otherwise joined to an attachment member, such as a cylindrical backing. A rotary drill bit typically includes a number of PDC cutting elements affixed to the bit body. It is also known that a stud carrying the PDC may be used as a PDC cutting element when mounted to a bit body of a rotary drill bit by press-fitting, brazing, or otherwise securing the stud into a receptacle formed in the bit body. 
     Conventional PDCs are normally fabricated by placing a cemented carbide substrate into a container with a volume of diamond particles positioned on a surface of the cemented carbide substrate. A number of such containers may be loaded into an HPHT press. The substrate(s) and volume of diamond particles are then processed under HPHT conditions in the presence of a catalyst material that causes the diamond particles to bond to one another to form a matrix of bonded diamond grains defining a polycrystalline diamond (“PCD”) table. The catalyst material is often a metal-solvent catalyst (e.g., cobalt, nickel, iron, or alloys thereof) that is used for promoting intergrowth of the diamond particles. 
     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 acts as a catalyst to promote intergrowth between the diamond particles, which results in formation of a matrix of bonded diamond grains having diamond-to-diamond bonding therebetween, with interstitial regions between the bonded diamond grains being occupied by the solvent catalyst. 
     In some situations, the presence of the metal-solvent catalyst in the PCD table may reduce the thermal stability of the PCD table at elevated temperatures. For example, the difference in 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 table. 
     Accordingly, the metal-solvent catalyst may be removed from the PCD table to improve its thermal stability. Chemical leaching is often used to dissolve and remove the metal-solvent catalyst from the PCD table. 
     SUMMARY 
     Embodiments of the invention relate to methods of fabricating leached PDCs in which a PCD table thereof is leached and resized to provide a leached region having a selected geometry. Creating a leached region having such a selected geometry may improve the performance of the PDC in various conditions, such as impact strength and/or thermal stability. 
     In an embodiment, a method for fabricating a leached PDC includes providing a PDC including a PCD table bonded to a substrate. The PCD table includes a plurality of bonded diamond grains defining a plurality of interstitial regions that include an interstitial constituent disposed therein. A first chamfer may be formed between an upper surface of the PCD table and at least one side surface of the PCD table. The first chamfer may exhibit a first chamfer height measured from the upper surface of the PCD table to a bottom of the first chamfer. After forming the first chamfer, a region of the PCD table may be leached to at least partially remove the interstitial constituent therefrom to form a leached region. After leaching, a second chamfer may be formed in the PCD table that extends between the upper surface and the at least one side surface of the PCD table. The second chamfer exhibits a second chamfer height. 
     In another embodiment, a method for fabricating a PDC includes providing a PDC including a PCD table bonded to a substrate. The PCD table includes an upper surface and at least one side surface. The PCD table further includes a leached region that is substantially free of an interstitial constituent and extends to a leach depth from the upper surface. The method further includes forming a chamfer extending between the upper surface and the at least one side surface of the PCD table. The chamfer has a chamfer height that is at least about equal to the leach depth 
     In an embodiment, a PDC includes a substrate and a PCD table bonded to the substrate. The PCD table includes an upper surface, at least one side surface, and a chamfer extending between the upper surface and the at least one side surface. The chamfer exhibits a chamfer height measured from the upper surface to a bottom of the chamfer. The PCD table further includes a leached region from which an interstitial constituent is depleted. The leached region extends inwardly from the upper surface to a depth. The depth may be less than, substantially equal to, or greater than the chamfer height. 
     Features from any of the disclosed embodiments may be used in combination with one another, without limitation. In addition, other features and advantages of the present disclosure will become apparent to those of ordinary skill in the art through consideration of the following detailed description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings illustrate several embodiments, wherein identical reference numerals refer to identical or similar elements or features in different views or embodiments shown in the drawings. 
         FIGS. 1A-1C  are cross-sectional views illustrating different stages in a method of fabricating a PDC before the PDC is subjected to a leaching process according to an embodiment. 
         FIG. 2A  is a cross-sectional view illustrating a method of leaching a PCD table of the PDC shown in  FIG. 1C  according to an embodiment. 
         FIGS. 2B and 2C  are cross-sectional views illustrating different stages in finishing a PDC that has previously been leached according to an embodiment. 
         FIGS. 2D-2F  are cross-sectional views illustrating different leached region geometries with respect to the second chamfer according to various embodiments. 
         FIGS. 2G-2I  are cross-sectional views illustrating a method of forming a PDC according to another embodiment. 
         FIG. 3  is an isometric view of a rotary drill bit according to an embodiment that may employ one or more of the PDCs fabricated according to any of the embodiments disclosed herein. 
         FIG. 4  is a top elevation view of the rotary drill bit shown in  FIG. 3 . 
         FIG. 5  is an isometric cutaway view of a thrust-bearing apparatus according to an embodiment, which may utilize any of the disclosed PDC fabricated according to any of the embodiments disclosed herein as bearing elements. 
         FIG. 6  is an isometric cutaway view of a radial bearing apparatus according to an embodiment, which may utilize any of the disclosed PDC fabricated according to any of the embodiments disclosed herein as bearing elements. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention relate to methods of fabricating leached PDCs in which a PCD table thereof is leached and resized to provide a leached region having a selected geometry. Creating a leached region having such a selected geometry may improve the performance of the PDC in various conditions, such as impact strength and/or thermal stability. The PDC embodiments disclosed herein may be used in a variety of applications, such as rotary drill bits, bearing apparatuses, wire-drawing dies, machining equipment, and other articles and apparatuses. Generally, in one or more embodiments, fabricating a leached PDC includes forming a PCD table in an HPHT process, forming a first chamfer in the PCD table, at least partially leaching the PCD table having the first chamfer by exposing the PCD table to a leaching agent, and forming a second chamfer in the leached PCD table. 
       FIGS. 1A-1C  are cross-sectional views illustrating different stages in a method of fabricating a PDC before the PDC is subjected to a leaching process according to an embodiment. Referring to  FIG. 1A , a cross-sectional view of an assembly  100  is illustrated in which a plurality of diamond particles  104  (e.g., one or more, or two or more layers of diamond particles) are placed adjacent to a surface  106  of a substrate  108 . As shown in  FIG. 1B , a PCD table  124  may be fabricated by subjecting the assembly  100  including the plurality of diamond particles  104  and the substrate  108  to an HPHT sintering process in the presence of a catalyst, such as a metal-solvent catalyst (e.g., cobalt, nickel, iron, or alloys thereof), a carbonate catalyst, or a combination of the preceding catalysts to facilitate intergrowth between the diamond particles  104  and form the PCD table  124  comprising directly bonded-together diamond grains (e.g., exhibiting sp 3  diamond-to-diamond bonding) defining interstitial regions having the catalyst or other interstitial constituent disposed within at least a portion of the interstitial regions. The PCD table  124  is integrally formed with the substrate  108 . 
     In order to effectively HPHT sinter the plurality of diamond particles  104 , the assembly  100 , shown in  FIG. 1A , may be placed in a pressure transmitting medium, such as a refractory metal can, graphite structure, pyrophyllite or other pressure transmitting structure, or another suitable container or supporting element. The pressure transmitting medium, including the assembly  100 , may be subjected to an HPHT process using an HPHT press at a temperature of at least about 1000° C. (e.g., about 1300° C. to about 1600° C.) and a cell pressure of at least 4 GPa (e.g., about 5 GPa to about 10 GPa, about 7 GPa to about 9 GPa) for a time sufficient to sinter the diamond particles  104  and form the PCD table  124  that bonds to the substrate  108  during cooling from the HPHT process. 
     In the illustrated embodiment, the PCD table  124  is formed by HPHT sintering the diamond particles  104  on the substrate  108 , which may be a cobalt-cemented tungsten carbide substrate from which cobalt or a cobalt alloy infiltrates into the diamond particles  104  and catalyzes formation of the PCD table  124 . For example, the substrate  108  may comprise a cemented carbide material, such as a cobalt-cemented tungsten carbide material or another suitable material. For example, nickel, iron, or alloys thereof are other catalysts that may form part of the substrate  108 . Other materials for the substrate  108  include, without limitation, cemented carbides including titanium carbide, niobium carbide, tantalum carbide, vanadium carbide, and combinations of any of the preceding carbides cemented with iron, nickel, cobalt, or alloys thereof. 
     However, in other embodiments, the substrate  108  may be replaced with a catalyst material disc and/or catalyst particles may be mixed with the diamond particles  104 . As discussed above, in other embodiments, the catalyst may be a carbonate catalyst selected from one or more alkali metal carbonates (e.g., one or more carbonates of Li, Na, and K), one or more alkaline earth metal carbonates (e.g., one or more carbonates of Be, Mg, Ca, Sr, and Ba), or combinations of the foregoing. The carbonate catalyst may be partially or substantially completely converted to a corresponding oxide of Li, Na, K, Be, Mg, Ca, Sr, Ba, or combinations after HPHT sintering of the plurality of diamond particles  104 . 
     The diamond particle size distribution of the plurality of diamond particles  104  may exhibit a single mode, or may be a bimodal or greater grain size distribution. In an embodiment, the diamond particles  104  may comprise a relatively larger size and at least one relatively smaller size. As used herein, the phrases “relatively larger” and “relatively smaller” refer to particle sizes (by any suitable method) that differ by at least a factor of two (e.g., 30 μm and 15 μm). According to various embodiments, the diamond particles  104  may include a portion exhibiting a relatively larger average particle size (e.g., 50 μm, 40 μm, 30 μm, 20 μm, 15 μm, 12 μm, 10 μm, 8 μm) and another portion exhibiting at least one relatively smaller average particle size (e.g., 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, 1 μm, 0.5 μm, less than 0.5 μm, 0.1 μm, less than 0.1 μm). In an embodiment, the diamond particles  104  may include a portion exhibiting a relatively larger average particle size between about 10 μm and about 40 μm and another portion exhibiting a relatively smaller average particle size between about 1 μm and 4 μm. In some embodiments, the diamond particles  104  may comprise three or more different average particle sizes (e.g., one relatively larger average particle size and two or more relatively smaller average particle sizes), without limitation. 
     In another embodiment, the diamond particles  104  shown in  FIG. 1A  may be replaced with another type of diamond volume. For example, the diamond particles  104  may be replaced with a porous, at least partially leached PCD table that is infiltrated with a cementing constituent from the substrate  108  (e.g., a cobalt metallic infiltrant) and attached thereto during an HPHT process using any of the diamond-stable HPHT process conditions disclosed herein. For example, the cementing constituent from the substrate  108  shown in  FIG. 1A  may partially or substantially completely infiltrate into the at least partially leached PCD table. Upon cooling from the HPHT process, a strong metallurgical bond is formed between the infiltrated PCD table and the substrate. In other embodiments, another metallic infiltrant may be disposed between the at least partially leached PCD table and the substrate  108  that partially or substantially completely infiltrates into the at least partially leached PCD table. The at least partially leached PCD table includes a plurality of directly bonded-together diamond grains exhibiting diamond-to-diamond bonding therebetween (e.g., sp 3  bonding). The plurality of directly bonded-together diamond grains define a plurality of interstitial regions. The interstitial regions form a network of at least partially interconnected pores that enable fluid to flow from one side to an opposing side. For example, the at least partially leached PCD table may be formed by removing the PCD table  124  from the substrate  108  and subjecting the removed PCD table to a leaching process to substantially remove the catalyst therein. 
       FIG. 1B  is a cross-sectional view of a PDC  120  formed by HPHT processing of the assembly  100  shown in  FIG. 1A . In such an embodiment, the PCD table  124  so-formed may include tungsten and/or tungsten carbide that is swept in with the catalyst from the substrate  108 . For example, some tungsten and/or tungsten carbide from the substrate may be dissolved or otherwise transferred by the liquefied catalyst (e.g., cobalt from a cobalt-cemented tungsten carbide substrate) of the substrate  108  that sweeps into the diamond particles  104 . The PCD table  124  includes a plurality of directly bonded-together diamond grains exhibiting diamond-to-diamond bonding there between (e.g., sp 3  bonding) defining interstitial regions with the catalyst disposed within at least a portion of the interstitial regions. The PCD table  124  also becomes metallurgically bonded to the substrate  108  during HPHT processing of the assembly  100 . 
     More details about the manner in which the PDC  120  and/or the PCD table  124  may be formed may be found in U.S. Pat. No. 7,866,418, which is incorporated herein, in its entirety, by this reference. U.S. Pat. No. 7,866,418 discloses various embodiments for fabricating PCD and PDCs at ultra-high cell pressures. For example, PCD sintered at a cell pressure of at least about 7.5 GPa may exhibit a coercivity of 115 Oe or more, a high-degree of diamond-to-diamond bonding, a specific magnetic saturation of about 15 G·cm 3 /g or less, and a metal-solvent catalyst content of about 7.5 weight % (“wt %”) or less, such as about 1 wt % to about 6 wt %, about 1 wt % to about 3 wt %, about 3 wt % to about 6 wt %, greater than 0 to about 6 wt %, or less than 6 wt %. Generally, as the sintering cell pressure that is used to form the PCD increases, the coercivity may increase and the magnetic saturation may decrease. 
     The PCD table  124  defined collectively by the bonded diamond grains and the catalyst may exhibit a coercivity of about 115 Oe or more and a metal-solvent catalyst content of less than about 7.5 wt % (e.g., as may be indicated by a specific magnetic saturation of about 15 G·cm 3 /g or less). In another embodiment, the coercivity of the PCD may be about 115 Oe to about 250 Oe and the specific magnetic saturation of the PCD may be greater than 0 G·cm 3 /g to about 15 G·cm 3 /g. In yet another embodiment, the coercivity of the PCD may be about 115 Oe to about 175 Oe and the specific magnetic saturation of the PCD may be about 5 G·cm 3 /g to about 15 G·cm 3 /g. Further, in another embodiment, the coercivity of the PCD may be about 155 Oe to about 175 Oe and the specific magnetic saturation of the PCD may be about 10 G·cm 3 /g to about 15 G·cm 3 /g. The specific permeability (i.e., the ratio of specific magnetic saturation to coercivity) of the PCD may be about 0.10 G·cm 3 /g·Oe or less, such as about 0.060 G·cm 3 /g·Oe to about 0.090 G·cm 3 /g·Oe. Despite the average grain size of the bonded diamond grains being less than about 30 μm in some embodiments, the catalyst content in the PCD may be less than about 7.5 wt % to thereby result in a desirable thermal stability. 
     In some embodiments, the PDC  120  so-formed may be subjected to a number of different shaping operations. For example, an upper working surface  162  of the PCD table  124  may be planarized and/or polished. 
     Referring to  FIG. 1C , a peripherally-extending first chamfer  172  may be formed in the PCD table  124  that extends between the upper working surface  162  and the at least one side surface  164  of the PCD table  124 . A chamfer height  150  (also shown in  FIG. 2B ) is measured from the upper working surface  162  to a bottom/lowest point of the chamfer  172  on the at least one side surface  164 . For example, the first chamfer  172  may have a height of less than about 400 μm, less than about 100 μm, less than 20 μm, about 20 μm to about 300 μm, or about 100 μm to about 250 μm. 
     The first chamfer  172  may be formed by grinding, wire electro-discharge machining (“EDM”), laser machining, combinations thereof, or another suitable material-removal process. Additionally, the presence of the first chamfer  172  prior to leaching may influence the resulting leach region geometry. 
     Optionally, in some embodiments, a circumferential or other lateral portion of the substrate  108  and the PCD table  124  of the PDC  120  may be removed prior to leaching. For example, the PDC  120  of  FIG. 1B  is depicted as having first diameter  140 , or other lateral dimension if the PDC  120  is not cylindrical. A circumferential or other lateral portion of the PDC  120  may be removed such that the PDC  120  of  FIG. 1B  exhibits a second diameter  145  or other lateral dimension if PDC  120  is not cylindrical, as shown in  FIGS. 1B and 1C . For example, the circumferential or other lateral portion exceeding second diameter  145  of the PDC  120  may be removed by grinding (e.g., centerless grinding), wire EDM, laser machining, combinations thereof, or another suitable material-removal process. 
     Referring to  FIG. 2A , the PCD table  124  having the first chamfer  172  may be subjected to a leaching process. The PCD table  124  may be leached with a leaching agent  132  to at least partially remove the catalyst from the PCD table  124  to a selected maximum leach depth “d” (shown in  FIG. 2B ) measured from any of the upper working surface  162 , chamfer  172 , and/or at least one side surface  164 . For example, the PDC  120  may be enclosed in a leaching vessel  130 , as illustrated in  FIG. 2A , containing a flow or stagnant volume of the leaching agent  132  (e.g., hydrofluoric acid, nitric acid, hydrochloric acid, aqua regia, combinations thereof, or any other suitable leaching agent) to leach the catalyst from the PCD table  124  to form a leached region  224  (shown in  FIG. 2B ). The leached region  224  may be at least partially depleted of the catalyst (e.g., substantially free of the catalyst) and located remote from the substrate  108 . An un-leached region  226 , proximate to the substrate  108 , is relatively unaffected by the leaching process and includes the catalyst therein in the interstitial regions. 
     In the illustrated embodiment, the PDC  120  may be at least partially surrounded by a protective layer  216 . At least a portion of the PDC  120 , including the substrate  108 , may be surrounded by the protective layer  216 . In an embodiment, the protective layer  216  can comprise a mask or other protective coating. For example, the protective layer  216  is illustrated in  FIG. 2A  as an inert cup as disclosed in U.S. Provisional Application No. 61/728,953, which is incorporated herein, in its entirety, by this reference. However, any protective structure for leaching disclosed in U.S. Provisional Application No. 61/728,953 may be employed. The protective layer  216  may limit or prevent the leaching agent  132  from substantially chemically damaging certain portions of the PDC  120 , such as the substrate  108  and/or a selected portion of the PCD table  124  during leaching. The protective layer  216  may be selectively formed and/or provided over the substrate  108  and a selected portion of the PCD table  124  in varied patterns, designs, or as otherwise desired, without limitation. Such a configuration may enable selective leaching of the PCD table  124 . 
     In another embodiment, selected portions of the PCD table  124  may be subjected to a masking treatment to mask areas that are desired to remain unaffected by the leaching process, such as portions of the un-leached region  226  at and/or near the substrate  108 . For example, electrodeposition or plasma deposition of a nickel alloy (e.g., a suitable Inconel® alloy), a suitable metal, or another suitable metallic alloy covering the substrate  108  and the un-leached region  226  (shown in  FIG. 2B ) may be used to limit the leaching process to the desired directed area of the leached region  224  (shown in  FIG. 2B ). In other embodiments, protective leaching trays (not shown in  FIG. 2A ) for protecting portions of the PCD table  124  and the substrate  108  from leaching agents during leaching may be used. Examples of such protective trays are further described within U.S. Provisional Application No. 61/728,953, which was previously incorporated by reference. 
       FIG. 2B  is a cross-sectional view of the PDC  120  after subjecting the PCD table  124  to the leaching process as described above with respect to  FIG. 2A . In an embodiment, the leach depth “d” (shown in  FIG. 2B ) to which the leached region  224  extends may be greater than about 200 μm. In another embodiment, the leach depth “d” may be about 50 μm to about 800 μm. In another embodiment, the leach depth “d” may be about 400 μm to about 800 μm, about 100 μm to about 300 μm, or about 250 μm to about 800 μm. 
     As shown in  FIG. 2B , the first chamfer  172  has a height  150 . Additionally, the leached region  224  may optionally extend down the at least side surface  164  of the PCD table  124 . As previously stated above, it may be desirable to form the leached region  224  having a selected geometry. For example, it may be desirable to limit the volume or area that the leached region  224  occupies in the PCD table  124 . 
     In an embodiment, after the PDC  120  has been subjected to the leaching process, a circumferential portion of the PDC  120  or other lateral portion (if the PDC  120  is not cylindrical) may be optionally removed. For example, the PDC  120  of  FIG. 2B  is depicted as having the second diameter  145 . The circumferential or other lateral portion  228  of the PDC  120  may be removed such that the PDC  120  has a final diameter  230 . For example, the circumferential or other lateral portion  228  of the PDC  120  may be removed by grinding (e.g., centerless grinding), wire EDM, laser machining, combinations thereof, or another suitable material-removal process. In an embodiment, the difference between the final diameter  230  and second diameter  145  is substantially equal to any of the disclosed heights or height ranges for the first chamfer height  150 . 
     Referring now to  FIG. 2C , after the PDC has been subjected to the leaching process, a second chamfer  272  may be formed to selectively tailor a geometry of the leached region  224  and effectively replace the first chamfer  172 . For example, the second chamfer  272  may be formed by grinding, wire EDM, laser machining, combinations thereof, or another suitable material-removal process. Similar to the first chamfer  172 , the second chamfer  272  extends between the upper working surface  212  and the at least one side surface  164  of the PCD table  124 . In an embodiment, the second chamfer  272  may exhibit a height  220 , which is greater than the height  150  of the first chamfer  172 . For example, the height  150  of the first chamfer  172  may be approximately 254 μm, while the height  220  of the second chamfer  272  may be approximately 500 μm. In other embodiments, the height  220  of the second chamfer  272  may be about 1.5 to about 3 times the height  150  of the first chamfer  172 , such as about 1.5 to about 2 times. For example, the height  220  of the second chamfer  272  may be less than about 600 μm, less than about 500 μm, less than 200 μm, about 100 μm to about 300 μm, or about 200 μm to about 400 μm. The reader will understand that sizes and relative shapes of the chamfers and leached regions  224  depicted in  FIGS. 2A-2F  are only meant to illustrate various embodiments of the invention and other geometries are contemplated by this disclosure. 
     Prior to forming the second chamfer  272 , the leached region  224  may exhibit a substantially uniform depth with respect to any of the working surface  162 , the first chamfer  172 , or the at least one side surface  164 . After forming the second chamfer  272 , the leached region  224  may no longer exhibit a substantially uniform depth and/or may exhibit a different profile because material from the PCD table  124  is removed inwardly from the first chamfer  172 . For example, the leached region  224  shown in  FIG. 2C  after forming the second chamfer  272  may terminate proximate to a bottom edge of the second chamfer  272 . The leach depth as measured generally perpendicularly and inwardly from the second chamfer  272  may also decrease (e.g., substantially continuously decrease) along the second chamfer  272  with distance toward the at least one side surface  164 . In particular, a distance  290  between a bottom of the leached region  224  and a bottom of the second chamfer  272  shown in  FIG. 2C  may be substantially less than a distance  292  between a bottom of the first chamfer  172  and a bottom of the leached region  224  shown in  FIG. 2B . For example, in an embodiment, the distance  290  is less than about 100 μm, less than about 50 μm, less than about 75 am, less than about 10 μm, about 50 μm to about 100 μm, about 20 μm to about 50 μm, or about 30 μm to about 75 μm. Further still, in another embodiment (as depicted in  FIG. 2F ), the distance  290  is approximately zero, such that the bottom of the leached region  224  and the bottom of the second chamfer  272  are approximately equal and co-located (i.e., the depth of the leached region  224  being about equal to the second chamfer height  220 ). 
     As discussed briefly above, in various embodiments, the location of bottom of the leached region  224  with respect to the second chamfer  272  and/or a geometry of the leached region  224  may be adjusted based upon the geometry of the leached region  224  prior to forming the second chamfer  272  and the amount of material removed from the PCD table  124  to define the second chamber  272 . For example, as shown in  FIG. 2A , the protective layer  216  covers up to approximately the bottom of the first chamfer  172 . However, the protective masks or cups may be selectively placed in other locations such that leached regions of various sizes and shapes may be formed, which in conjunction with the amount of material removed from the PCD table  124  to form the second chamfer  272 , may affect the location of the bottom of the leached region  224  after forming the second chamfer  272 . Thus, the depth of the leached region  224  may be less than or substantially equal to the height  220  of the second chamfer  272 . In some embodiments, the depth of the leached region  224  may be greater than the height  220  of the second chamfer  272 . In an embodiment,  FIG. 2D  illustrates the PDC  120  in which the bottom of the leach region  224  is above the bottom of the second chamfer  272  by a distance  291 . For example, the distance  291  may be less than about 100 μm, less than about 50 μm, less than about 75 μm, less than about 10 μm, about 50 μm to about 100 am, about 20 μm to about 50 μm, or about 30 μm to about 75 μm. In another embodiment,  FIG. 2E  shows the PDC  120  in which the bottom of the leached region  224  extends below the second chamfer  272  the distance  290 . Further, in another embodiment,  FIG. 2F  illustrates the PDC  120  in which the bottom of the leached region  224  is substantially at the bottom of the second chamfer  272 . 
     It is currently believed by the inventor that limiting the extent of the leached region  224  may increase the impact resistance of the PCD table  124 , such as resistance to cracking. Specifically, it is currently believed by the inventor that the PCD table  124  having the selectively tailored geometry may exhibit greater performance under both high heat and high impact applications. 
     The reader will understand that the above-recited methods may be performed in alternate sequences. For example, as a non-limiting example, after the leaching process is applied, the second diameter  145  of the PDC  120  may be first ground down to the final diameter  230  and then the second chamfer  272  may be formed, or alternatively, the second chamfer  272  may be formed first and then the second diameter  145  may be ground down to the final diameter  230 . 
     In other embodiments, only a single chamfer may be employed to form a leached region defined by a generally horizontal boundary with the underlying, un-leached region. For example, in  FIG. 2G , the PCD table  124  without a chamfer may be subjected to a leaching process as previously described herein. The PCD table  124  may be leached with the leaching agent  132  to at least partially remove the interstitial constituent (e.g., catalyst or infiltrant) from the PCD table  124  to a selected maximum leach depth “d” (shown in  FIG. 2H ) measured from the upper working surface  162 . For example, the PDC  120  may be enclosed in the leaching vessel  130 , as illustrated in  FIG. 2G , containing a flow or stagnant volume of the leaching agent  132  (e.g., hydrofluoric acid, nitric acid, hydrochloric acid, aqua regia, combinations thereof, or any other suitable leaching agent) to leach the catalyst from the PCD table  124  to form a leached region  224  (shown in  FIG. 2H ). The leached region  224  may be at least partially depleted of the interstitial constituent (e.g., substantially free of the interstitial constituent) and located remote from the substrate  108 . An un-leached region  226 , proximate to the substrate  108 , is relatively unaffected by the leaching process and includes the catalyst therein in the interstitial regions. 
     In the illustrated embodiment, the PDC  120  may be at least partially surrounded by the protective layer  216 . At least a portion of the PDC  120 , including the substrate  108 , may be surrounded by the protective layer  216  or any other protective structure for leaching disclosed herein. For example, seal element  217  of the protective layer  216  may be positioned adjacent to the upper surface  162  of the PCD table  124 . As shown in  FIG. 2H , after leaching, the leached region  224  extends to the selected maximum leach depth “d” to define generally horizontal boundary  219  between the leached region  224  and the un-leached region  226 . For example, the generally horizontal boundary  219  may be substantially parallel to the upper surface  162  of the PCD table  124  and the interfacial surface of the substrate  108  bonded to the PCD table  124 . Referring to  FIG. 2I , a chamfer  221  may be formed between the at least one side surface  164  and the upper surface  162 . In some embodiments, the selected depth “d” may be substantially equal to a height  223  of the chamfer  221 . In other embodiments, the selected maximum leach depth “d” may be greater than the height  223  of the chamfer  221  as indicated by the dashed generally horizontal boundary  227 . The selected maximum leached depth “d” may be greater than about 200 μm, about 50 μm to about 800 μm, about 400 μm to about 800 μm, about 400 μm to about 800 μm, about 100 μm to about 300 μm, or about 250 μm to about 800 μm. 
     In some embodiments, a circumferential or other lateral portion of the substrate  108  and the PCD table  124  of the PDC  120  may be removed prior to leaching or after leaching. For example, the PDC  120  of  FIG. 1B  is depicted as having first diameter  140 , or other lateral dimension if the PDC  120  is not cylindrical. A circumferential or other lateral portion of the PDC  120  may be removed such that the PDC  120  of  FIG. 2G  exhibits a second, reduced diameter or other lateral dimension if PDC  120  is not cylindrical. For example, the circumferential or other lateral portion may be removed by grinding (e.g., centerless grinding), wire EDM, laser machining, combinations thereof, or another suitable material-removal process. In other embodiments, a circumferential or other lateral portion of the PDC  120  may be removed after leaching and/or after forming the chamfer  221 . 
       FIG. 3  is an isometric view and  FIG. 4  is a top elevation view of a rotary drill bit  300  according to an embodiment. The rotary drill bit  300  includes at least one PDC fabricating according to any of the previously described PDC embodiments. The rotary drill bit  300  comprises a bit body  302  that includes radially and longitudinally extending blades  304  with leading faces  306 , and a threaded pin connection  308  for connecting the bit body  302  to a drilling string. The bit body  302  defines a leading end structure configured for drilling into a subterranean formation by rotation about a longitudinal axis  310  and application of weight-on-bit. At least one PDC cutting element, manufactured and configured according to any of the previously described PDC embodiments (e.g., the PDC  120  shown in  FIG. 2C ), may be affixed to rotary drill bit  300  by, for example, brazing, mechanical affixing, or another suitable technique. 
     With reference to  FIG. 4 , each of a plurality of PDCs  312  is secured to the blades  304 . For example, each PDC  312  may include a PCD table  314  bonded to a substrate  316 . More generally, the PDCs  312  may comprise any PDC disclosed herein, without limitation. In addition, if desired, in an embodiment, a number of the PDCs  312  may be conventional in construction. Also, circumferentially adjacent blades  304  define so-called junk slots  318  there between, as known in the art. Additionally, the rotary drill bit  300  includes a plurality of nozzle cavities  320  for communicating drilling fluid from the interior of the rotary drill bit  300  to the PDCs  312 . 
       FIGS. 3 and 4  merely depict one embodiment of a rotary drill bit that employs at least one cutting element comprising a PDC fabricated and structured in accordance with the disclosed embodiments, without limitation. The rotary drill bit  300  is used to represent any number of earth-boring tools or drilling tools, including, for example, core bits, roller-cone bits, fixed-cutter bits, eccentric bits, bicenter bits, reamers, reamer wings, mining rotary drill bits, or any other downhole tool including PDCs, without limitation. 
     The PDCs disclosed herein may also be utilized in applications other than rotary drill bits. For example, the disclosed PDC embodiments may be used in thrust-bearing assemblies, radial bearing assemblies, wire-drawing dies, artificial joints, machining elements, PCD windows, and heat sinks. 
       FIG. 5  is an isometric cutaway view of a thrust-bearing apparatus  500  according to an embodiment, which may utilize any of the disclosed PDC embodiments as bearing elements. The thrust-bearing apparatus  500  includes respective thrust-bearing assemblies  502 . Each thrust-bearing assembly  502  includes an annular support ring  504  that may be fabricated from a material, such as carbon steel, stainless steel, or another suitable material. Each support ring  504  includes a plurality of recesses (not labeled) that receives a corresponding bearing element  506 . Each bearing element  506  may be mounted to a corresponding support ring  504  within a corresponding recess by brazing, press-fitting, using fasteners, combinations thereof, or another suitable mounting technique. One or more, or all of bearing elements  506  may be manufactured and configured according to any of the disclosed PDC embodiments. For example, each bearing element  506  may include a substrate  508  and a PCD table  510 , with the PCD table  510  including a bearing surface  512 . 
     In use, the bearing surfaces  512  of one of the thrust-bearing assemblies  502  bears against the opposing bearing surfaces  512  of the other one of the bearing assemblies  502 . For example, one of the thrust-bearing assemblies  502  may be operably coupled to a shaft to rotate therewith and may be termed a “rotor.” The other one of the thrust-bearing assemblies  502  may be held stationary and may be termed a “stator.” 
       FIG. 6  is an isometric cutaway view of a radial bearing apparatus  600  according to an embodiment, which may utilize any of the disclosed PDC embodiments as bearing elements. The radial bearing apparatus  600  includes an inner race  602  positioned generally within an outer race  604 . The outer race  604  includes a plurality of bearing elements  606  affixed thereto that have respective bearing surfaces  608 . The inner race  602  also includes a plurality of bearing elements  610  affixed thereto that have respective bearing surfaces  612 . One or more, or all of the bearing elements  606  and  610  may be configured according to any of the PDC embodiments disclosed herein. The inner race  602  is positioned generally within the outer race  604 , with the inner race  602  and outer race  604  configured so that the bearing surfaces  608  and  612  may at least partially contact one another and move relative to each other as the inner race  602  and outer race  604  rotate relative to each other during use. 
     While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting. Additionally, the words “including,” “having,” and variants thereof (e.g., “includes” and “has”) as used herein, including the claims, shall be open ended and have the same meaning as the word “comprising” and variants thereof (e.g., “comprise” and “comprises”).