Patent Publication Number: US-2019170186-A1

Title: Bearing apparatus including a bearing assembly having a continuous bearing element and a tilting pad bearing assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/528,709 filed on May 22, 2017, which is a U.S. national stage application of PCT Application No. PCT/US2015/062434 filed on Nov. 24, 2015, which claims priority to U.S. Provisional Application No. 62/087,132 filed on Dec. 3, 2014, the disclosure of each of which is incorporated herein, in its entirety, by this reference. 
    
    
     BACKGROUND 
     Wear-resistant, superhard compacts are utilized in a variety of mechanical applications. For example, polycrystalline diamond compacts (“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 and other superhard compacts have found particular utility as superhard bearing elements in thrust bearings within pumps, turbines, subterranean drilling systems, motors, compressors, generators, gearboxes, and other systems and apparatuses. For example, a PDC bearing element typically includes a superhard polycrystalline diamond layer that is commonly referred to as a diamond table. The diamond table is formed and bonded to a substrate using a high-pressure/high-temperature (“HPHT”) process. 
     A thrust-bearing apparatus includes a number of superhard bearing elements affixed to a support ring. The superhard bearing elements (e.g., a PDC bearing element) bear against other superhard bearing elements of an adjacent bearing assembly during use. Superhard bearing elements are typically brazed directly into a preformed recess formed in a support ring of a fixed-position thrust bearing. 
     Despite the availability of a number of different bearing apparatuses including such PDCs and/or other superhard materials, manufacturers and users of bearing apparatuses continue to seek bearing apparatuses that exhibit improved performance characteristics, lower cost, or both. 
     SUMMARY 
     Embodiments of the invention relate to bearing assemblies and apparatuses, which may be operated hydrodynamically. The disclosed bearing assemblies and apparatuses may be employed in bearing apparatuses for use in pumps, turbines, compressors, turbo expanders, or other mechanical systems. 
     In an embodiment, a bearing apparatus includes a first bearing assembly and a second bearing assembly. The first bearing assembly includes a first support ring and a plurality of tilting pads each of which includes a superhard bearing surface. Each tilting pad is tilted and/or tiltably secured relative to the first support ring. The second bearing assembly includes a continuous superhard bearing element. The continuous superhard bearing element includes a continuous superhard bearing surface generally facing the superhard bearing surface of each of the tilting pads. Additionally, the continuous superhard bearing element has a maximum lateral width greater than 5.1 cm (about 2 inches). 
     In an embodiment, the continuous superhard bearing element or a superhard bearing element of at least one tilting pad may include polycrystalline diamond, or a sintered or reaction-bonded ceramic (e.g., reaction-bonded silicon carbide or reaction-bonded silicon nitride). In an embodiment, the continuous superhard bearing element or a superhard bearing element of at least one tilting pad may have a surface finish less than about 0.64 micrometers (μm) (about 25 microinches). 
     Other embodiments are related to methods of using and manufacturing bearing apparatuses including a first bearing assembly having a plurality of tilting pads and a second bearing assembly having a continuous superhard bearing element. 
     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 of the present disclosure, wherein identical reference numerals refer to identical or similar elements or features in different views or embodiments shown in the drawings. 
         FIG. 1A  is an isometric view of a bearing assembly including continuous superhard bearing element having a continuous superhard bearing surface according to an embodiment. 
         FIG. 1B  is an isometric partial cross-sectional view taken along the line  1 B- 1 B of the bearing assembly of  FIG. 1A . 
         FIG. 2A  is an isometric view of a tilting pad thrust-bearing assembly according to an embodiment. 
         FIG. 2B  is an isometric partial cross-sectional view taken along line  2 B- 2 B of the tilting pad thrust-bearing assembly shown in  FIG. 2A . 
         FIG. 2C  is an isometric view of one of the tilting pads shown in  FIGS. 2A and 2B , with the tilting pad having a continuous superhard bearing surface according to an embodiment. 
         FIG. 2D  is a cross-sectional view taken along line  2 D- 2 D of the bearing tilting pad shown in  FIG. 2C . 
         FIG. 3  is a top plan view of a tilting pad including multiple segments having serrated ends that form seams between the multiple segments according to another embodiment. 
         FIG. 4  is an isometric view of a tilting pad comprising a continuous superhard bearing element according to another embodiment. 
         FIG. 5A  is an isometric cutaway view of an embodiment of a thrust-bearing apparatus that may include a rotor having continuous superhard bearing element and a stator including tilting pads, with a housing shown in cross-section. 
         FIG. 5B  is a partial cross-sectional schematic representation of the thrust-bearing apparatus of  FIG. 5A  during use taken along line  5 B- 5 B thereof showing a fluid film that develops between the tilting pads of the stator and the continuous superhard bearing element of the rotor. 
         FIG. 6A  is an exploded isometric view of a radial bearing apparatus that may include a rotor having a continuous superhard bearing element and a stator including tilting pads according to an embodiment. 
         FIG. 6B  is an isometric partial cross-sectional view of the stator of the radial bearing apparatus of  FIG. 6A  according to an embodiment. 
         FIG. 6C  is an isometric partial cross-sectional view of the rotor of the radial bearing apparatus of  FIG. 6A  according to an embodiment. 
         FIG. 7  is a partial isometric cutaway view of a rotary system of a turbine according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention relate to bearing assemblies and apparatuses, which may be operated hydrodynamically. The disclosed bearing assemblies and apparatuses may be employed in bearing apparatuses for use in pumps, turbines, compressors, turbo expanders, or other mechanical systems. Motor assemblies including at least one of such bearing assemblies or apparatus are also disclosed, as well as methods of using and fabricating such bearing assemblies and apparatuses utilizing superhard materials. 
     As will be discussed in more detail below, in one or more embodiments, a bearing apparatus includes a first bearing assembly and a second bearing assembly. The first bearing assembly includes a first support ring and a plurality of tilting pads each of which includes a superhard bearing surface. Each tilting pad is tilted and/or tiltably secured relative to the first support ring. The second bearing assembly includes a second support ring and a continuous superhard bearing element that is secured to the second support ring. The continuous superhard bearing element includes a continuous superhard bearing surface generally facing the superhard bearing surface of each of the tilting pads. In some embodiments, the continuous superhard bearing element has a maximum lateral width greater than about 5.1 cm (about 2 inches). 
     While the description herein provides examples relative to a pump or turbine bearing apparatus, the bearing assembly and apparatus embodiments disclosed herein may be used in any number of applications. For instance, the bearing assemblies and apparatuses may be used in subterranean drilling and motor assembly, motors, compressors, turbo expanders, generators, gearboxes, other systems and apparatuses, or combinations of the foregoing. Furthermore, the bearing assemblies and apparatuses may also be operated hydrodynamically, partially hydrodynamically, or not hydrodynamically, if desired or needed. 
       FIGS. 1A and 1B  are isometric and isometric partial cross-sectional views, respectively, of a thrust-bearing assembly  100  including a continuous superhard bearing element  102  having a continuous superhard bearing surface  104 . Such a configuration may improve wear performance as compared to an assembly in which the overall bearing surface is formed of a plurality of segmented, discontinuous bearing surfaces defined by the individual bearing elements. Additionally, such a configuration may improve wear performance and manufacturing costs as compared to an assembly in which the overall bearing surface is formed of a plurality of segmented bearing elements that form a substantially continuous bearing surface. Wear performance may be improved because the substantial absence of any discontinuities in the overall bearing surface may minimize and/or prevent chipping and/or cracking of the continuous bearing surface  104 , promote fluid film development and/or prevent fluid from leaking through seams formed between adjacent superhard bearing segments, increase fluid film strength, or combinations thereof. 
     The continuous superhard bearing element  102  includes a continuous superhard bearing surface  104 . The continuous superhard bearing surface  104  has an integral construction such that a single superhard bearing element forms the full continuous superhard bearing surface  104 . The continuous superhard bearing element  102  is attached to a support ring  106  in a fixed position. For example, the support ring  106  may define a recess  114  that receives the continuous superhard bearing element  102  partially therein. The continuous superhard bearing element  102  may be secured within the recess  114  to the support ring  106  by brazing, press-fitting, using fasteners, clamping, other type of mechanical attachment, another suitable technique, or combinations thereof. However, in other embodiments, the support ring  106  may be omitted. 
     The support ring  106  may be made from a variety of different materials. For example, the support ring  106  may comprise carbon steel, stainless steel, copper (e.g., brass or bronze alloys), tungsten carbide, or another suitable material. 
     The continuous superhard bearing surface  104  of the continuous superhard bearing element  102  may exhibit a relatively smooth surface finish. In an embodiment, a bearing apparatus includes a thrust-bearing assembly that includes continuous superhard bearing element  102  and another bearing assembly (e.g., a tilting pad bearing assembly). As the thrust-bearing assembly that includes the continuous superhard bearing element  102  rotates relative to the other bearing surface of the other bearing assembly, a fluid film may develop between the continuous superhard bearing surface  104  of the continuous superhard bearing element  102  and the surface of the other bearing assembly, thereby increasing the wear resistance and/or performance of the bearing apparatus. A smooth surface finish may facilitate the formation of the fluid film between the bearing surfaces of the bearing apparatus. For example, a surface defect caused by a rough surface finish (e.g., a bump, a ridge, etc.) on the continuous superhard bearing surface  104  of the continuous superhard bearing element  102  may prevent the development of a sufficient fluid film at least proximate the defect. The surface defect may also increase the friction or contact between the bearing surfaces. Such conditions may result in chipping, power losses, cracking or increased wear on both bearing surfaces. As such, the continuous superhard bearing surface  104  of the continuous superhard bearing element  102  and/or the surface of the other bearing assembly may include a smooth surface finish. In an embodiment, the surface finish of the continuous superhard bearing surface  104  of the continuous superhard bearing element  102  or any other surface of the bearing apparatus (e.g., the tilting pad bearing assembly) may have a surface finish less than about 0.89 μm (about 35 microinches) (e.g., less than about 0.64 μm (about 25 microinches), less than about 0.38 μm (about 15 microinches), less than about 0.25 μm (about 10 microinches), less than about 0.13 μm (about 5 microinches)) as measured, for example, by a profilometer by root mean square (RMS). In another embodiment, the surface finish of the continuous superhard bearing surface  104  of the continuous superhard bearing element  102  or any other surface of the bearing apparatus may have a surface finish of about 0.64 μm (25 microinches) to about 0.89 μm (about 35 microinches), about 0.38 μm (about 15 microinches) to about 0.64 μm (about 25 microinches), about 0.38 μm (about 15 microinches) to about 0.51 μm (about 20 microinches), about 0.25 μm (about 10 microinches) to about 0.38 μm (about 15 microinches), about 0.18 μm (about 7 microinches) to about 0.25 μm (about 10 microinches), about 0.13 μm (about 5 microinches) to about 0.18 μm (about 7 microinches), about 0.064 μm (about 2.5 microinches) to about 0.13 μm (about 5 microinches), less than about 0.064 μm (about 2.5 microinches), less than about 0.051 μm (about 2 microinches), less than about 0.025 μm (about 1 microinch), or submicrometers (submicroinches). The surface finish of any bearing surface of the bearing apparatuses disclosed herein may exhibit any of the disclosed surface finishes and may be selected based on the type of fluid used for lubrication of the bearing surfaces, the expected fluid pressure or flow through the bearing apparatus, the expected rate of rotation, the expected load in the bearing apparatus and the expected tilting of any tilting pad in a bearing assembly, other performance criteria, or combinations thereof. 
     The continuous superhard bearing element  102  may have a maximum lateral width “W,” such as a maximum diameter. In an embodiment, the maximum lateral width “W” of the continuous superhard bearing element  102  is greater than about 5.1 cm (about 2 inches) (e.g., greater than about 7.6 cm (about 3 inches), greater than about 12.7 cm (about 5 inches). In another embodiment, the maximum lateral width “W” of the continuous superhard bearing element  102  is about 5.1 cm (about 2 inches) to about 7.6 cm (about 3 inches), about 7.6 cm (about 3 inches) to about 12.7 cm (about 5 inches), about 12.7 cm (about 5 inches) to about 17.8 cm (about 7 inches), about 17.8 cm (about 7 inches) to about 25.4 cm (about 10 inches), about 25.4 cm (about 10 inches) to about 30.5 cm (about 12 inches) (e.g., 28 cm (about 11 inches)), or about 30.5 cm (about 12 inches) to about 40.6 cm (about 16 inches). In some applications, the maximum lateral width “W” of the continuous superhard bearing element  102  may be less than about 5.1 cm (about 2 inches). The maximum lateral width “W” of the continuous superhard bearing element  102  may be limited at least partially based on the type of material used for the continuous superhard bearing element  102 . 
     The continuous superhard bearing element  102  may be formed from of a variety of superhard materials. The term “superhard” means a material having a hardness at least equal to the hardness of tungsten carbide, silicon carbide, or silicon nitride. In an embodiment, the continuous superhard bearing element  102  may include polycrystalline cubic boron nitride, polycrystalline diamond (e.g., formed by chemical vapor deposition or by HPHT sintering), diamond crystals, silicon carbide, silicon nitride, tantalum carbide, tungsten carbide (e.g., binderless tungsten carbide, cobalt-cemented tungsten carbide), other metal carbides, other superhard carbides, or combinations thereof. In another embodiment, the continuous superhard bearing element  102  may be composed of sintered or reaction-bonded silicon carbide, or sintered or reaction-bonded silicon nitride. The sintered or reaction-bonded silicon carbide, or sintered or reaction-bonded silicon nitride may have additional materials therein. For example, the additional materials in a sintered or reaction-bonded ceramic may include diamond, polycrystalline diamond, cubic boron nitride, a material exhibiting a hardness greater than the reaction-bonded ceramic or a material exhibiting a thermal conductivity greater than the reaction-bonded ceramic. Adding materials to the sintered or reaction-bonded continuous superhard bearing element may increase the thermal conductivity and/or wear resistance of continuous superhard bearing element  102 . For example, adding diamond particles to sintered or reaction-bonded silicon carbide, or sintered or reaction-bonded silicon nitride may increase the wear resistance of the continuous superhard bearing element  102  by more than 500%. In an embodiment, the diamond particles may be added to the sintered or reaction-bonded ceramic in an amount less that about 80 weight % (e.g., about 50 weight % to about 80 weight %, about 25 weight % to about 50 weight %, or less than about 25 weight %). Suitable reaction-bonded ceramics from which the superhard bearing element  102  may be made are commercially available from M Cubed Technologies, Inc. of Newark, Del. In an embodiment, the continuous superhard bearing element  102  may be formed from a single material or a single piece of any of the superhard materials disclosed herein. 
     In the illustrated embodiment, the continuous superhard bearing element  102  includes a superhard table  108  defining the continuous superhard bearing surface  104  and a substrate  110  to which the superhard table  108  is bonded. In an embodiment, the continuous superhard bearing element  102  may be a polycrystalline diamond compact (“PDC”). The PDC includes a polycrystalline diamond (“PCD”) table defining the superhard table  108  to which the substrate  110  is bonded. For example, the substrate  110  may comprise a cobalt-cemented tungsten carbide substrate. The PCD table includes a plurality of directly bonded-together diamond grains exhibiting diamond-to-diamond bonding therebetween (e.g., sp 3  bonding), which define a plurality of interstitial regions. A portion of, or substantially all of, the interstitial regions of such the PCD table may include a metal-solvent catalyst or a metallic infiltrant disposed therein that is infiltrated from the substrate  110  or from another source. For example, the metal-solvent catalyst or metallic infiltrant may be selected from iron, nickel, cobalt, and alloys of the foregoing. The PCD table may further include thermally-stable diamond in which the metal-solvent catalyst or metallic infiltrant has been partially or substantially completely depleted from a selected surface or volume of the PCD table  108 , for example, an acid leaching process. 
     For example, appropriately configured PDCs may be used as the continuous superhard bearing element  102 , which may be formed in an HPHT processes. Suitable PDCs having a PCD table with a maximum diameter over 6.4 cm (about 2.5 inches) are commercially available from Iljin Diamond Co., Ltd. of Korea. For example, diamond particles may be disposed adjacent to the substrate  110 , and subjected to an HPHT process to sinter the diamond particles to form the PCD table that bonds to the substrate  110 , thereby forming the PDC. The temperature of the HPHT process may be at least about 1000° C. (e.g., about 1200° C. to about 1600° C.) and the cell pressure of the HPHT process may be at least 4.0 GPa (e.g., about 5.0 GPa to about 12 GPa or about 7.5 GPa to about 11 GPa) for a time sufficient to sinter the diamond particles. 
     The diamond particles may exhibit an average particle size of about 50 μm or less, such as about 30 μm or less, about 20 μm or less, about 10 μm to about 18 μm, or about 15 μm to about 18 μm. In some embodiments, the average particle size of the diamond particles may be about 10 μm or less, such as about 2 μm to about 5 μm or submicron. In some embodiments, the diamond particles 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 mass of diamond particles may include a portion exhibiting a relatively larger size (e.g., 30 μm, 20 μm, 15 μm, 12 μm, 10 μm, 8 μm) and another portion exhibiting at least one relatively smaller 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 one embodiment, the diamond particles may include a portion exhibiting a relatively larger size between about 10 μm and about 40 μm and another portion exhibiting a relatively smaller size between about 1 μm and 4 μm. In some embodiments, the diamond particles may comprise three or more different sizes (e.g., one relatively larger size and two or more relatively smaller sizes), without limitation. The PCD table  108  so-formed after sintering may exhibit an average diamond grain size that is the same or similar to any of the foregoing diamond particle sizes and distributions. 
     More details about diamond particle sizes and diamond particle size distributions that may be employed to form the PCD table in any of the embodiments disclosed herein are disclosed in U.S. patent application Ser. No. 13/734,354; U.S. Provisional Patent Application No. 61/948,970; and U.S. Provisional Patent Application No. 62/002,001. U.S. patent application Ser. No. 13/734,354; U.S. Provisional Patent Application No. 61/948,970; and U.S. Provisional Patent Application No. 62/002,001 are each incorporated herein, in their entirety, by this reference. 
     In an embodiment, the superhard table  108  may be integrally formed with the substrate  110 . For example, the superhard table  108  may be a sintered PCD table that is integrally formed with the substrate  110 . In such an embodiment, the infiltrated metal-solvent catalyst from the substrate  110  may be used to catalyze formation of diamond-to-diamond bonding between diamond grains of the superhard table  108  from diamond powder during HPHT processing. In another embodiment, the superhard table  108  may be a pre-formed superhard table that has been HPHT bonded or brazed to the substrate  110  in a second HPHT process after being initially formed in a first HPHT process. For example, the superhard table  108  may be a pre-formed PCD table that has been leached to substantially completely remove metal-solvent catalyst used in the manufacture thereof and subsequently HPHT bonded or brazed to the substrate  110  in a separate process. 
     In some embodiments, the superhard table  108  may be leached to deplete a metal-solvent catalyst or a metallic infiltrant therefrom in order to enhance the thermal stability of the superhard table  108 . For example, when the superhard table  108  is a PCD table, the superhard table  108  may be leached to remove at least a portion of the metal-solvent catalyst from a working region thereof to a selected depth that was used to initially sinter the diamond grains to form a leached thermally-stable region. The leached thermally-stable region may extend inwardly from the continuous superhard bearing surface  104  to a selected depth. In one example, the depth of the thermally-stable region may be about 10 μm to about 600 μm. More specifically, in some embodiments, the selected depth is about 50 μm to about 100 μm, about 200 μm to about 350 μm, or about 350 μm to about 600 μm. The leaching may be performed in a suitable acid, such as aqua regia, nitric acid, hydrofluoric acid, or mixtures of the foregoing. 
     The substrate  110  may also be formed from any number of different materials, and may be integrally formed with, or otherwise bonded or connected to, the superhard table  108 . Materials suitable for the substrate  110  may include, without limitation, cemented carbides, such as tungsten carbide, titanium carbide, chromium carbide, niobium carbide, tantalum carbide, vanadium carbide, or combinations thereof cemented with iron, nickel, cobalt, or alloys thereof. For example, in an embodiment, the substrate  110  comprises cobalt-cemented tungsten carbide. However, in certain embodiments, the superhard tables  108  may be omitted, and the continuous superhard bearing element  102  may be made from a superhard material, such as cobalt-cemented tungsten carbide. In other embodiments, the substrate  110  may be omitted and the continuous superhard bearing element  102  may be a superhard material, such as a polycrystalline diamond body that has been leached to deplete metal-solvent catalyst therefrom or may be an un-leached PCD body. 
     A hole  112  may be formed in the continuous superhard bearing element  102  using a variety of techniques. The hole  112  may be sized and configured to receive a rotating shaft of pump, turbine, or other machine. In an embodiment, the hole  112  may be machined into a disk from which the continuous superhard bearing element  102  is made using electrical discharge machining (e.g., plunge electrical discharge machining and/or wire electrical discharge machining), drilling, laser drilling, other suitable techniques, or combinations thereof. For example, plunge electrical discharge machining may be used to create a small starter though hole in the disk from which the continuous superhard bearing element  102  is made. Wire electrical discharge machining may then be used to enlarge the small starter though hole to form the hole  112 . In another example, a laser is used to create the small starter through hole or the laser may be used to form the hole  112 . In another embodiment, a sacrificial material that is more easily removed than the superhard material from which the superhard bearing element  102  is made may be used to define the hole  112  of the continuous superhard bearing element  102 . For example, a sacrificial material (e.g., tungsten, tungsten carbide, hexagonal boron nitride, or combinations thereof) is laterally surrounded by unsintered diamond particles and is then subjected to an HPHT process. The sacrificial material is then removed from the PCD table so formed (e.g., mechanically, by blasting or via a leaching process) from the PCD surrounding it to form the hole  112 . 
     In another embodiment, the continuous superhard bearing element  102  may include a coating that forms the continuous superhard bearing surface  104 . The coating may be formed using a chemical vapor deposition technique, a physical vapor deposition technique, or any other deposition technique. For example, diamond may be deposited on a less hard surface to form the continuous superhard bearing surface  104  using a chemical or physical vapor deposition technique. 
       FIGS. 2A and 2B  are isometric and isometric partial cross-sectional views, respectively, of a tilting pad thrust-bearing assembly  200  according to an embodiment. The tilting pad thrust-bearing assembly  200  includes a support ring  218  that carries a plurality of circumferentially spaced tilting pads  216 . The tilting pads  216  may include, for instance, fixed tilting pads, adjustable tilting pads, self-establishing tilting pads, other bearing pads or elements, or combinations of the foregoing. Examples of tilting pad thrust-bearing assemblies for the tilting pad thrust-bearing assembly  200  are disclosed in U.S. Pat. No. 8,545,103, the disclosure of which is incorporated herein, in its entirety, by this reference. 
     The bearing surface of each of the tilting pads  216  of the illustrated embodiment generally has a truncated pie-shaped geometry or a generally trapezoidal geometry, and may be distributed about a thrust axis  220 , along which a thrust force may be generally directed during use. Each tilting pad  216  may be located circumferentially adjacent to another tilting pad  216 , with a circumferential space  222  or other offset therebetween. For instance, the circumferential space  222  may separate adjacent tilting pads  216  by a distance of about 2.0 mm to about 20.0 mm, or a distance of about 3.5 mm to about 15 mm, although the separation distance may be greater or smaller. For instance, as the size of the tilting pad bearing assembly  200  increases, the size of the tilting pads  216  and/or the size of the circumferential space  222  may also increase. For example, the tilting pads  216  may exhibit a nominal radial width less than about 7.6 cm (about 3 inches) (e.g., less than about 5.1 cm (about 2 inches), less than about 2.5 cm (about 1 inch), less than 1.3 cm (about 0.5 inches), between 0.64 cm (about 0.25 inches) to about 1.3 cm (about 0.5 inches), between about 1.3 cm (about 0.5 inches) to about 2.5 cm (about 1 inch), between about 2.5 cm (about 1 inch) to about 5.1 cm (about 2 inches)). In other embodiment, the tilting pads  216  may exhibit a nominal radial width greater than about 7.6 cm (about 3 inches). 
     Each tilting pad  216  may include a discrete superhard bearing element  224 , such that the tilting pads  216  collectively provide a non-continuous superhard bearing surface. The superhard bearing element  224  may include a superhard table  226  that may be bonded to a substrate  228 . For example, the superhard bearing element  224  may be formed from any of the materials and compacts previously described with respect to the continuous superhard bearing element  102 . 
     To support the tilting pads  216  of the tilting pad thrust-bearing assembly  200 , the support ring  218  may define a channel  230  and the tilting pads  216  may be placed within the channel  230 . In other embodiments, the support ring  218  may define multiple pockets or otherwise define locations for the tilting pads  216 . The tilting pads  216  may then be supported or secured within the support ring  218  in any suitable manner. For instance, as discussed hereafter, a pivotal connection may be used to secure the tilting pads  216  within the support ring  218 , although any other suitable securement or attachment mechanism may also be utilized. The support ring  218  may also include an inner, peripheral surface defining a hole  212 . The hole  212  may be generally centered about the thrust axis  220 , and may be adapted to receive a shaft (e.g., a downhole drilling motor shaft). The support ring  218  may be formed of the same materials as the support ring  106 . 
     In the illustrated embodiment, the tilting pad thrust-bearing assembly  200  includes  10  tilt pads. In other embodiments, more or less than  10  tilt pads may be used in the tilting pad thrust-bearing assembly  200 . For example, between 3 to 16 tilt pads (e.g., 3 to 6, 6 to 8, 8 to 10, or 10 to 12) may be included in the tilting pad thrust-bearing assembly  200 . The number of tilt pads included in the tilting pad thrust-bearing assembly  200  may be chosen based on the expected load, the superhard materials of the continuous superhard bearing element  102  and the superhard bearing element  224 , the size of the continuous superhard bearing element  102 , and the desired life of the bearing apparatus. 
     In the embodiment illustrated in  FIGS. 2A and 2B , the tilting pads  216  may be used in connection with a runner or other superhard bearing element (e.g., the continuous superhard bearing element  102  shown in  FIG. 1A ). In general, the tilting pad bearing assembly  200  may rotate relative to a runner or other bearing assembly, while a lubricant or other fluid (e.g., seawater) floods the tilting pad bearing assembly  200  and the runner/other bearing assembly. For example, as the runner  100  is rotated relative to a tilt pad bearing assembly  200 , a fluid film separating the runner/other bearing assembly from a superhard bearing element  224  may develop. For favorable use of the hydrodynamic forces within the lubricant, the tilting pads  216  may tilt which may result in a higher lubricant film thickness existing at a leading edge (i.e., an edge of a tilting pad  216  that would be traversed first by a reference line on the runner while the runner  100  moves in the direction of rotation), than at a trailing edge (i.e., an edge of a tilting pad  216  over which such reference line is second to pass in the direction of rotation), at which or near which a minimum film thickness may develop. The tilt pads may be manufactured such that respective superhard bearing surfaces thereof exhibit the same or similar smooth surface finishes as the continuous superhard bearing element  102 , as previously described. Of course, in other embodiments, the tilt pad bearing assembly  200  may rotate with respect to the runner  100 , if desired, without limitation. 
     In the illustrated embodiment, each of the plurality of superhard bearing elements  224  is secured to a support plate  232  ( FIG. 2B ). The support plate  232  may, for example, be formed of a metal, an alloy, a cemented carbide material, other material, or any combination thereof. The substrate  228  of the superhard bearing element  224  may be secured to the support plate  232  by brazing, welding, or other method. In some embodiments, the support plate  232  may define a pocket into which the superhard bearing segments may be tiltably or fixedly assembled and/or positioned. In an embodiment, the support plate  232  has an integral construction such that a single body may form substantially the full support plate  232 . In other embodiments, multiple segments of one or more materials may be used to form or define the support plate  232 . In another embodiment, multiple superhard bearing segments may be used to form the superhard bearing element  224 . 
     The degree to which the tilting pads  216  rotate or tilt may be varied in any suitable manner. For instance, in an embodiment, the tilting pads  216  may be tilted about respective radial axes that extend generally radially from the thrust axis  220 . In  FIG. 2B , the support plate  232  may be attached to a pin  234 . The pin  234  may, for example, be formed of a metal, an alloy, a cemented carbide material, other material, or any combinations thereof. The pin  234  may be allowed to at least partially rotate, or may otherwise define or correspond to a tilt axis  236 . For example, according to some embodiments, the pin  234  is journaled or otherwise secured within the support ring  218  in a manner that allows the pin  234  to rotate relative to the support ring  218 . The pin  234  may be fixed to the support plate  232  such that as the pin  234  rotates relative to the support ring  218 , the support plate  232  may also rotate or tilt relative to the tilt axis  236  of the pin  234 . The pin  234  and support plate  232  may rotate or tilt between zero and twenty degrees in some embodiments, such that the superhard bearing element  224  of the respective tilting pads  216  may also tilt between about zero and about twenty degrees relative to the pin  234  or other horizontal axis. In other embodiments, the pin  234  and/or the superhard bearing element  224  may rotate between about zero and about fifteen degrees, such as a positive or negative angle (θ) of about 0.5 to about 3 degrees (e.g., about 0.5 to about 1 degree or less than 1 degree) relative to the tilt axis  236  of the pin  234 . In some cases, the support ring  218  may be configured for bidirectional rotation. In such a case, the pin  234  may be allowed to rotate in clockwise and/or counter-clockwise directions. For example, the superhard bearing element  224  may thus tilt in either direction relative to the axis of the pin  234  and/or the support ring  218 . For instance, the superhard bearing element  224  may be rotated to a position anywhere between a positive or negative angle of about twenty degrees relative to an axis of the pin  234 , such as a positive or negative angle (θ) of about 0.5 to about 3 degrees (e.g., about 0.5 to about 1 degree or less than 1 degree) relative to the tilt axis  236  of the pin  234 . 
     The pin  234  may be used to allow one or more tilting pads  216  to selectively rotate. For instance, the tilting pads  216  may be self-establishing or limiting such that the tilting pads  216  may automatically or otherwise adjust to a desired tilt or other orientation based on the lubricant used, the axial forces applied along the thrust axis, the rotational speed of the runner and/or the tilting pad bearing assembly  200 , other factors, or combinations of the foregoing. In still other embodiments, the tilting pads  216  may be fixed at a particular tilt, or may be manually set to a particular tilt with or without being self-establishing. 
     Further, the pin  234  represents a single mechanism for facilitating rotation, translation, or other positioning of the tilting pads  216  so as to provide tilting pad superhard bearing element  224 . In other embodiments, other mechanisms may be used. By way of illustration, leveling links, pivotal rockers, spherical pivots, other elements, or any combination of the foregoing may also be used to facilitate positioning of the tilting pads  216  in a tilted configuration. In an embodiment, the support plate  232  may be used to facilitate rotation of a respective tilting pad  216 . The support plate  232  may, for instance, be machined or otherwise formed to include a receptacle, an opening, or other structure into which the pin  234  may be at least partially received or secured. In embodiments in which the pin  234  is excluded, the support plate  232  may be machined or otherwise formed to include other components, such as spherical pivot, pivotal rocker, or leveling link interface. The support plate  232  may be formed of any suitable material, such as steel or other alloy; however, in some embodiments the support plate  232  is formed of a material that is relatively softer than the substrate  228 , such that the support plate  232  may be relatively easily machined or formed into a desired shape or form. In other embodiments, the support plate  232  can be eliminated and the substrate  228  may be directly machined or formed to facilitate tilting of the tilting pad  216 . Examples of tilting mechanisms that may be used for tilting the tilting pads disclosed herein are disclosed in U.S. Patent Published Application No. 20140102810, the disclosure of which is incorporated herein, in its entirety, by this reference. 
     In some embodiments, the tilt axis of the tilting pads  216  may be aligned with a radial reference line dividing (e.g., symmetrically) the bearing surface  223 . For example, where the support ring  218  may be configured for bi-directional rotation, the tilt axis of the tilting pads  216  may be centered circumferentially between opposing edges of the tilting pads  216  (e.g., the leading edge and the trailing edge). In other embodiments, the tilt axis of a tilting pad  216  may be offset relative to a center of the bearing surface  223  of the tilting pad  216 . For example, where the support ring  218  is part of a rotor configured for only unidirectional rotation, the axis of rotation of the tilting pad  216  may be offset such that the axis of rotation is closer to one of the leading edge or the trailing edge of the tilting pad  216 . In other embodiments, a tilt axis may be offset from a circumferential center of its bearing surface despite a rotor being configured for bidirectional rotation, or a tilt axis may be circumferentially centered despite a rotor being configured for unidirectional rotation. 
       FIGS. 2C and 2D  are isometric and cross-sectional views, respectively, of a single one of the tilting pads  216  shown in  FIGS. 2A and 2B  that may be used in connection with the tilting pad bearing assembly  200  described above. The tilting pad  216  includes the continuous superhard bearing element  224 . As previously discussed, each tilting pad  216  may include the superhard table  226  bonded to the substrate  228 , and the substrate  228  may further be secured within the support plate  232  by brazing, using high temperature adhesives, press-fitting, fastening with fasteners, or other suitable attachment mechanism. In the illustrated embodiment, the support plate  232  may facilitate attachment of the substrate  228  to the support plate  232  by including an interior surface  238  that defines an interior pocket  240 . The interior pocket  240  may be sized to generally correspond to a size of the substrate  228 . It is noted that the support plate  232  merely represents one embodiment for a support plate and other configurations may be used. For example, according to another embodiment, a support plate may lack a pocket or other receptacle. In still another embodiment, the support plate may be eliminated. 
     In the illustrated embodiment, a superhard bearing surface  223  of the superhard bearing element  224  (e.g., the superhard table  226 ) is substantially planar, although such an embodiment is merely illustrative. In other embodiments, the superhard bearing surface  223  of the superhard bearing element  224  may be curved, or have another contour or topography. Moreover, outer edges of the superhard bearing element  224  may optionally include a chamfer  242 . The chamfer  242  may be formed by placing a chamfer on the individual outer edge regions of the superhard bearing element  224  or, if present, the superhard table  226 . The superhard bearing element  224  may also take a number of other forms. For example, in  FIG. 2C , the superhard bearing surface  223  is substantially pie-shaped with a chamfered edge. In other embodiments, the edges of a superhard bearing element  224  may define other shapes, including radiused, arcuate, generally circular, generally elliptical, generally trapezoidal, other shaped surfaces, or may form a sharp edge, or combinations thereof. 
       FIGS. 3 and 4  illustrate top plan and isometric views, respectively, of different embodiments of tilting pads that may be employed in a tilting pad bearing assembly according to an embodiment.  FIG. 3  illustrates a tilting pad  316  that may include a plurality of superhard bearing segments  344   a - d , each of which includes a superhard bearing element  324  that may include a superhard table  326  bonded to a substrate (not shown). The superhard table  326  and substrate (not shown) is optionally bonded or otherwise connected to a support plate  332 . Each superhard table  326  includes a superhard bearing surface  327  that collectively form a larger, substantially continuous superhard bearing surface. 
     The superhard bearing segments  344   a - d  each may include an outer edge region  346  and an interior edge region  348 . The superhard bearing segments  344   a - d  may be configured with a serrated geometry at the interior edge regions  348 . Such a configuration may allow adjacent superhard bearing segments  344   a - d  to mate and at least partially interlock, while also defining seams  350  of a geometry that limits fluid leakage radially through the gaps between adjoining superhard bearing segments  344   a - d.    
     The illustrated and described seams  350  between adjacent superhard bearing segments  344  are merely illustrative, and seams  350  between superhard bearing segments  344  and/or configurations of interior edge regions  348  of superhard bearing segments  344  may have any number of configurations. For, instance, a set of interconnecting superhard bearing segments may have substantially straight, serrated, saw-toothed, sinusoidal-like, curved, or otherwise shaped interior edge regions, or any combination of the foregoing. Moreover, some portions of an interior edge region may have one configuration of shape while another portion of an interior edge region on the same superhard bearing segment may have a different configuration or shape. Accordingly, different superhard bearing segments may also include different mating geometry or other configurations. The plurality of superhard bearing segments  344   a - d  may have a coating thereon that at least partially fills the seams  350 . The coating may be applied using chemical vapor deposition, physical vapor deposition, other deposition techniques or combinations thereof. Additionally, sealant materials may at least partially fill the seams  350 , such as braze alloy, tungsten carbide, polycrystalline diamond, other ceramic materials, or combinations thereof. 
     As discussed herein, a tilting pad bearing assembly including superhard bearing segments may be utilized where certain conditions are met, or in any number of other circumstances or industries. For instance, an application may be identified where it would benefit to use a superhard bearing element including a superhard material. However, the superhard material may have associated production limits (e.g., size, availability, etc.). Where the superhard bearing element has a size, shape, or other feature(s) exceeding such production limits, the superhard bearing element may be fashioned out of multiple individual segments that collectively define a superhard bearing surface of the superhard bearing element. In other cases, however, the type of material used in the superhard bearing element may not have the same production limits as PDCs or other superhard materials, or the superhard bearing element may be sized small enough to allow a single superhard or other material to be used to form the superhard bearing surface. 
       FIG. 4  illustrates an embodiment in which a tilting pad  416  may have a size and/or comprise a material configured such that a single segment may form a substantially continuous surface of the superhard bearing element  424 . In particular, the tilting pad  416  may include a superhard table  426  bonded to a substrate  428 . The substrate  428  may in turn be bonded to a support plate  432 . Optionally, the support plate  432  is oversized relative to the substrate  428 ; however, the support plate  432  may also be about the same size or smaller than the substrate  428 . In this embodiment, a single element may define substantially the entire superhard bearing element  424 . For instance, the element may exhibit a length and/or width that may measure approximately 15 mm by 10 mm, such that a single superhard table  426  made from polycrystalline diamond or other materials may be fashioned into the desired shape, even in the absence of providing multiple interlocking, adjoining, or adjacent segments. In other embodiments, the element may have other sizes and may even exceed a maximum size available for PDCs. For instance, other superhard materials (e.g., tungsten carbide, reaction-bonded ceramics, reaction-bonded ceramics containing diamond particles) or any other superhard material disclosed herein may be used to form the superhard bearing element  424  using a single, integral segment. 
     Any of the above-described embodiments including a bearing assembly having a continuous superhard bearing element and/or a tilting pad bearing assembly may be employed in a thrust-bearing apparatus. For example, a thrust-bearing apparatus may include a rotor configured as the thrust-bearing assembly  100  and a stator configured as the tilting pad thrust-bearing assembly  200 , although any combination of the bearing assemblies with the continuous superhard bearing element and a tilting pad bearing assembly may be employed in other embodiments.  FIGS. 5A  is an isometric cutaway view of a thrust-bearing apparatus  500  according to an embodiment.  FIG. 5B  is a partial cross-sectional schematic representation of a thrust-bearing apparatus  500  during use. One of the bearing assemblies is a stator while the other bearing assembly is a rotor. In the illustrated embodiment, the tilting pad bearing assembly is a stator  552  and the bearing assembly having the continuous superhard bearing element is a rotor  554 . The stator  552  and rotor  554  may be configured as any of the described embodiments of bearing assemblies. The terms “rotor” and “stator” refer to rotating and stationary components of the tilting pad bearing apparatus  500 , respectively, although the rotating and stationary status of the illustrated embodiments may also be reversed. 
     The stator  552  may include a support ring  506  and a plurality of tilting pads  516  mounted or otherwise attached to a support ring  518 , with each of the tilting pads  516  having a superhard bearing element. The tilting pads  516  may be tilted and/or tilt relative to a rotational axis  520  of the thrust-bearing apparatus  500  and/or one or more surfaces of the support ring  506 . The tilting pads  516  may be fixed at a particular tilt, may be manually adjusted to exhibit a particular tilt, may self-establish at a particular tilt, or may be otherwise configured. 
     The rotor  554  may be configured in any suitable manner, including in accordance with any of the embodiments described herein. The rotor  554  may include a support ring  506  connected to continuous superhard bearing element  502 . The continuous superhard bearing element  502  of the rotor  554  is generally adjacent to the superhard bearing elements of the stator  552 . A fluid film may develop between the continuous superhard bearing element  502  of the rotor  554  and the superhard bearing element of the stator  552 . The continuous superhard bearing element  502  may be mounted or otherwise attached to a support ring  518  by brazing, a press-fit, mechanical fasteners, or in another manner. 
     As shown in  FIG. 5A , a shaft  556  may be coupled to the support ring  506  and operably coupled to an apparatus capable of rotating the shaft section  556  in a direction R (or in an opposite direction). For example, the shaft  556  may extend through and may be secured to the support ring  506  of the rotor  554  by press-fitting or a threaded connection that couples the shaft  556  to the support ring  506 , or by using another suitable technique. A housing  558  may be secured to the support ring  518  of the stator  552  by, for example, press-fitting or threadly coupling the housing  558  to the support ring  518 , and may extend circumferentially about the shaft  556 , the stator  552 , and the rotor  554 . 
     The operation of the thrust-bearing apparatus  500  is discussed in more detail with reference to  FIG. 5B .  FIG. 5B  is a partial cross-sectional schematic representation in which the shaft  556  and housing  558  are not shown for clarity. In operation, lubrication, drilling fluid, mud, or some other fluid may be pumped between the shaft  556  and the housing  558 , and between the tilting pads  516  of the stator  552  and the continuous superhard bearing element  502  of the rotor  554 . More particularly, rotation of the rotor  554  at a sufficient rotational speed may sweep the fluid onto superhard bearing elements of the stator  552  and may allow a fluid film  560  to develop between the continuous superhard bearing element  502  of the rotor  554  and the superhard bearing element of the stator  552 . The fluid film  560  may develop under certain operational conditions in which the rotational speed of the rotor  554  is sufficiently great and the thrust load is sufficiently low. 
     In an embodiment, the tilting pads  516  may be positioned at a fixed tilt angle or at a configurable or self-establishing tilt angle. The tilting pads  516  of the stator  552  may have a leading edge  562  at a different position than a trailing edge  564  relative to the rotor  554 . For instance, in  FIG. 5B , the tilting pads  516  may be tilted such that a greater separation exists between the tilting pads  516  and the continuous superhard bearing element  502  at a leading edge  562  (illustrated on one tilting pad  516 ) than at a trailing edge  564  (illustrated on another tilting pad  516 , for clarity). Under such circumstances, the lubricant film  560  may have a variable thickness across the tilting pad  516 . In this particular embodiment, a higher lubricant film thickness may exist at the leading edge  562  than at the trailing edge  564 . 
     Under certain operational conditions, the pressure of the fluid film  560  may be sufficient to substantially prevent contact between the continuous superhard bearing element  502  of the rotor  554  and the superhard bearing elements of the stator  552  and thus, may substantially reduce wear of the continuous superhard bearing element  502  and the superhard bearing elements. When the thrust loads exceed a certain value and/or the rotational speed of the rotor  554  is reduced, the pressure of the fluid film  560  may not be sufficient to substantially prevent the continuous superhard bearing element  502  of the rotor  554  and the superhard bearing elements of the stator  552  from contacting each other. Under such operational conditions, the thrust-bearing apparatus  500  is not operated as a hydrodynamic bearing. Thus, under certain operational conditions, the thrust-bearing apparatus  500  may be operated as a hydrodynamic bearing apparatus and under other conditions the thrust-bearing apparatus  500  may be operated so that the continuous superhard bearing element  502  and superhard bearing elements of the tilting pad  516  contact each other during use or a partially developed fluid film is present between the continuous superhard bearing element  502  and superhard bearing elements of the tilting pad  516 . However, the superhard bearing elements of the plurality of tilting pads  516  and continuous superhard bearing element  502  may comprise superhard materials that are sufficiently wear-resistant to accommodate repetitive contact with each other, such as during start-up and shut-down of a system employing the thrust-bearing apparatus  500  or during other operational conditions not favorable for forming the fluid film  560 . In still other embodiments, a backup roller or other bearing (not shown) may also be included for use during certain operational conditions, such as during start-up, or as the fluid film  560  develops. 
     In an embodiment, the continuous superhard bearing element  502  and one or more of the plurality of tilt pads  516  may be formed from different materials. For example, the continuous superhard bearing element  502  may be formed from any of the reaction-bonded ceramics disclosed herein (e.g., reaction-bonded silicon carbide or reaction-bonded silicon nitride with or without diamond) and the bearing elements of each tilt pads  516  may be formed from a PDC or any other type of polycrystalline diamond element disclosed herein. Because the superhard bearing surface of the continuous superhard bearing element  502  and one or more tilt pads  516  may include different materials, a non-diamond bearing surface may wear preferentially relative to wear of a polycrystalline diamond bearing surface. Providing such a bearing assembly including different material bearing surfaces may provide for better heat transfer and better maintenance of the fluid film  560  between the superhard bearing surfaces of the continuous superhard bearing element  502  and the superhard bearing elements of the tilting pad  516  than if all the superhard bearing surfaces included the same non-diamond superhard material (e.g., where both include silicon carbide). 
     Polycrystalline diamond and reaction-bonded ceramics containing diamond particles have substantially higher thermal conductivity than superhard carbides, such as sintered silicon carbide, reaction-bonded silicon carbide, or tungsten carbide. Because one of the superhard bearing surfaces of the continuous superhard bearing element  502  or the superhard bearing element of the tilting pad  516  includes polycrystalline diamond or reaction-bonded ceramics containing diamond particles, heat generated during use (e.g., at non-diamond bearing surfaces) may be better dissipated as a result of its proximity or contact with polycrystalline diamond bearing surfaces. Thus, a bearing assembly including a polycrystalline diamond or reaction-bonded ceramics containing diamond particles bearing surfaces may provide increased wear resistance as compared to a bearing assembly in which all the bearing surfaces include a non-diamond superhard materials (e.g., silicon carbide), but at significantly lower cost than would be associated with a bearing assembly in which both of the opposed bearing surfaces include only polycrystalline diamond. 
     In an embodiment, at least one superhard bearing element of the stator  552  may include at least one non-diamond superhard bearing surface, such as only including non-diamond bearing surfaces. Meanwhile the rotor  554  may include a polycrystalline diamond continuous superhard bearing element  502 . The stator  552  within the tilting pad bearing apparatus  500  often fails before the rotor  554 . In some instances, this may occur because the stator  552  bearing surfaces are often subjected to unequal heating and wear. For example, wear on the stator  552  is often unequal as a result of a small number of stator  552  bearing elements beings somewhat more “prominent” than the other stator  552  bearing elements. As a result, contact, heating, and wear during use may be preferentially associated with these more prominent stator  552  bearing elements. For example, the bulk of the load and resulting wear may be borne by, for example, the one to three most prominent bearing elements, while the other stator  552  bearing elements may show little wear by comparison. Such wear may result from the difficulty of perfectly aligning the bearing elements of the bearing assembly. 
     Because the stator  552  may typically wear faster than the rotor, in an embodiment the stator  552  bearing elements may not include diamond, but include a non-diamond superhard material, as the stator  552  may fail first. In such an embodiment, the stator  552  may be replaced once failure or a given degree of wear occurs. In another embodiment, the stator  552  may include at least one, one or more, or only diamond bearing surfaces, and the rotor  554  may not include a diamond bearing surface. It is currently believed that having at least one diamond surface and at least one non-diamond surface facilitates faster breaking in of the bearing surfaces as the less hard bearing surfaces wear/break in relatively faster. In other embodiments, both the continuous superhard bearing element  502  and the superhard bearing elements of each tilt pads  516  may be formed from a PDC, diamond or any other type of polycrystalline diamond element disclosed herein. In another embodiment, both the continuous superhard bearing element  502  and the superhard bearing elements of each tilt pads  516  may be formed from non-polycrystalline diamond materials such as reaction-bonded ceramics or other superhard materials. In yet another embodiment, the continuous superhard bearing element  502  may be formed from non-polycrystalline diamond materials such as reaction-bonded ceramics or other superhard materials, and the superhard bearing elements of each tilt pads  516  may be PDCs or other type of polycrystalline diamond elements. 
     The concepts used in the thrust-bearing assemblies and apparatuses described herein may also be employed in radial bearing assemblies and apparatuses.  FIGS. 6A to 6C  are isometric, exploded, and isometric partial cross-sectional views, respectively, of a radial bearing apparatus  600  according to yet another embodiment. The radial bearing apparatus  600  may include an inner race  654  (e.g., a runner or rotor) that may have an interior surface  668  defining an hole  612  for receiving a shaft or other component. The inner race  654  may also include a continuous superhard bearing element  602  positioned at or near an exterior surface  670  of the inner race  654 . The continuous superhard bearing element  602  may include a convexly-curved continuous superhard bearing surface  604  and may be formed from any of the materials previously discussed for use with the continuous superhard bearing element  102 . 
     The support ring  606  of the inner race  654  may include a circumferentially-extending recess that receive the continuous superhard bearing element  602 . The continuous superhard bearing element  602  may be secured within the recess or otherwise secured to the support ring  606  by brazing, press-fitting, using fasteners, or another suitable technique. The support ring  606  may also define an interior surface  668  defining an opening  612  that is capable of receiving, for example, a shaft (not shown) or other apparatus. 
     The radial bearing apparatus  600  may further include an outer race  652  (e.g., a stator) configured to extend about and/or receive the inner race  654 . The outer race  652  may include a plurality of circumferentially-spaced tilting pads  616 , each of which may include a superhard bearing element  624 . A superhard bearing surface of the superhard bearing element  624  may be substantially planar, although in other embodiments the surface of the superhard bearing element  616  may be a concavely-curved superhard bearing surface to generally correspond to shapes of convexly-curved continuous superhard bearing surface  604  of the inner race  654 . The terms “rotor” and “stator” refer to rotating and stationary components of the radial bearing system  600 , respectively. Thus, if the inner race is configured to remain stationary, the inner race may be referred to as the stator and the outer race may be referred to as the rotor. 
     Rotation of a shaft (not shown) secured to the inner race  654  may effect rotation of the inner race  654  relative to the outer race  652 . Drilling fluid or other fluid or lubricant may be pumped between the continuous superhard bearing surface  604  of the continuous superhard bearing element  602  of the inner race  654  and the surface of the superhard bearing element  624  of the outer race  652 . When the inner race  654  rotates, the leading edge sections of the tilting pads  616  may sweep lubricant (e.g., drilling fluid or other lubricant) onto the surface of the superhard bearing element  624  of the outer race  652 . As previously described with respect to the hydrodynamic tilting pad bearing apparatus  500 , at sufficient rotational speeds for the inner race  654 , a fluid film may develop between the superhard bearing element  624  of the tilting pads  618  and the continuous superhard bearing element  602 , and may develop sufficient pressure to maintain the superhard bearing element  624  and the continuous superhard bearing element  602  apart from each other. Accordingly, wear on the superhard bearing element  624  and continuous superhard bearing element  602  may be reduced compared to when direct contact between superhard bearing element  624  and continuous superhard bearing element  602  occurs. 
     As further illustrated in  FIGS. 6A and 6B , the outer race  652  includes a support ring  618  extending about an axis  620 . The support ring  618  may include an interior channel  630  configured to receive a set of tilting pad  616  superhard bearing elements  624  distributed circumferentially about the axis  620 . Each tilting pad  616  may include a superhard table  626 . The superhard bearing element  624  may be curved (e.g., concavely-curved) or substantially planar and, in some embodiments, may include a peripheral chamfer. The tiling pad  616  may be formed from any of the superhard materials and structures disclosed herein. In other embodiments, the superhard bearing element  624  may be otherwise curved, lack a chamfered edge, may have another contour or configuration, or any combination of the foregoing. Each superhard table  626  may be bonded to a corresponding substrate  628 . Further, each superhard bearing element  624  may be tilted circumferentially relative to an imaginary cylindrical surface. The superhard tables  626  and substrates  628  may be fabricated from the same materials described above for the tilting pads  216  shown in  FIGS. 2A and 2B . 
     Each superhard bearing element  624  of a corresponding tilting pad  616  may be tilted in a manner that facilities sweeping in of a lubricant or other fluid to form a fluid film between the inner race  654  and the outer race  652 . Each tilting pad  616  may be tilted and/or tilt about an axis that is generally parallel to the central axis  620 . As a result, each tilting pad  616  may be tilted at an angle relative to the inner and outer surfaces of the ring  618  and in a circumferential fashion such that the leading edges of the tilting pads  616  are about parallel to the central axis  620 . The leading edge may help to sweep lubricant or another fluid onto the surfaces of the superhard bearing elements  624  of the stator  652  to form a fluid film in a manner similar to the tilting pads  516  shown in  FIGS. 5A and 5B . More particularly, when the inner race  654  is concentrically positioned relative to the outer race  652 , the leading edges may be offset relative to the outer edge of the outer race  652 , and by a distance that is larger than a distance between the outer race  652  and a trailing edge of the superhard bearing surface  624 . It should be noted that in other embodiments, the radial bearing apparatus  600  may be configured as a journal bearing. In such an embodiment, the inner race  654  may be positioned eccentrically relative to the outer race  652 . 
     In some embodiments, the tilting pad  616  may be formed from a plurality of superhard bearing segments (not shown) that collectively define a respective tilting pad  616 . Each superhard bearing segment may be substantially identical, or the superhard bearing segments may be different relative to other of the superhard bearing segments. In some embodiments, the superhard bearing segments each include a superhard table  626  bonded to a substrate  628  as described herein. Optionally, the substrate  628  may be connected or supported relative to a support plate  632 , the support ring  618 , or other material or component. Additionally, seams (not shown) may be formed between circumferentially and/or longitudinally adjacent to the superhard bearing elements  604 . The edges of the superhard bearing segments  626  may have any number of configurations or shapes, and may correspond to or interlock with adjoining edges in any number of different manners. Further, sealant materials may be disposed within a gap (not shown) that may be formed between adjacent superhard bearing segments to help further prevent fluid leakage through the seams. 
       FIG. 7  is a partial isometric cutaway view of an embodiment of a turbine system  700 , such as a wind turbine system, which may incorporate any of the bearing apparatus embodiments disclosed herein. The turbine system  700  may include a housing  758  and a main gear shaft  756  operably connected to another device such as a wind turbine, i.e., blades attached to a hub, (not shown). At least one rotor  754  including a continuous superhard bearing element  702  may be operably connected to the main shaft  756 . For example, the rotor  754  may be configured as the bearing assembly  100  shown in  FIG. 1  or any other bearing assembly including a continuous superhard bearing element disclosed herein. At least one stator  752  including a plurality of tilting pads may be connected to the housing  758 . For example, the stator  752  may be configured as the bearing assembly  200  shown in  FIG. 2A  or any other tilting pad bearing assembly disclosed herein. The stator  752  or the rotor  754  may be a split bearing (e.g., manufactured in multiple components) to facilitate assembly. The shaft  756  may extend through a central hole  712  in the rotor  754  and stator  752  and may be secured to each rotor  754  by press fitting or otherwise attaching the gear shaft  756  to each rotor  754  bearing assembly, threadly coupling the shaft  756  to each rotor  754  bearing assembly, or another suitable technique. In the illustrated embodiment, the wind turbine system includes two bearing apparatuses. However, in other embodiments, the wind turbine system may include one or more bearing apparatuses (e.g., one bearing apparatus, or three or more bearing apparatuses). 
     In an embodiment, the rotor  754  may include a support ring  706  and a continuous superhard bearing element  702  attached or bonded to the support ring  706 . The continuous superhard bearing element  702  includes a continuous superhard bearing surface  704 . The continuous superhard bearing element  702  may include a superhard table  708  bonded to a substrate  710 . Similarly, the stator  752  may include a support ring  718  having a channel  730  therein and a plurality of tilt pads  716  positioned inside the channel  730 . The plurality of tilting pads  716  may include a superhard bearing element  724  that may have a superhard bearing table  726  bonded to a substrate  728 . The plurality of tilting pads  716  may further include a support plate  732  above a pin  734  wherein the superhard bearing element  724  is bonded or attached to the support place  732 . While the stator  752  bearing assembly and the rotor bearing assembly  754  is shown including only one row of the superhard bearing elements  724  and  702 , respectively, the stator  752  bearing assembly and the rotor bearing assembly  754  may include two rows, three rows, or any number of suitable rows of the superhard bearing elements. 
     In an embodiment, wind may turn the blades on the wind turbine (not shown), which in turn may rotate the main shaft  756  about a rotation axis  720 . The main shaft  756  may rotate the rotor  754  bearing assembly about the rotation axis  720 . As shown, the main shaft  756  may go through a gear transmission box  766 . For example, the main shaft  774  may be connected to a first gear  776  that turns a second gear  778  or vice versa. The first gear  776  may be larger than the second gear  778 . The second smaller gear  778  may be connected to a shaft  780  that turns a generator (not shown) to produce electricity. 
     As wind speed increases and energy builds within the system  700 , the high thermal conductivity of a diamond or other high thermal conductivity bearing element may help remove heat from the contact surface between the surfaces of the bearing assemblies. Such a configuration may help reduce the likelihood of temperature induced strength reductions and/or failure in the bearing assemblies. Further, in an embodiment where either the continuous superhard bearing element  702  and at least one of the superhard bearing elements  724  of the tilt pads  716  are formed of more than one material, the modulus contrast between materials may help provide resistance to shock and vibration loading. Such a configuration may help reduce the likelihood of fretting, micro pitting, and/or other types of wear in the rotor  754  and stator  752  bearing assemblies. This may be advantageous given the frequent starts and stops of the system  700 . Moreover, in an embodiment, differences between the elasticity of superhard materials may help reduce the likelihood of adhesion. 
     While the bearing apparatus including the rotor  754  and the stator  752  is shown in a turbine application, the bearing apparatus may be used in other diverse applications. For example, the bearing apparatuses disclosed herein may be used in subterranean drilling and motor assembly, motors, pumps, compressors, generators, gearboxes, and other systems and apparatuses, or in any combination of the foregoing. 
     While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated. The various aspects and embodiment 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”).