Abstract:
A bearing assembly for a rotating shaft uses a carbide sleeve to prevent wear and carry load. The carbide sleeves provide increased life for rotating components used in the severe environments in the oil and gas industries. Various mechanisms can couple the carbide sleeve to the rotating shaft, including keys, keyways, drive rings, reaction rings, and other members to provide particular benefits. These mechanisms allow the carbide sleeve to bear the compressive load of other components, for example, or to slide axially on the shaft, when needed.

Description:
RELATED APPLICATIONS 
       [0001]    This divisional patent application claims the benefit of priority to copending U.S. patent application Ser. No. 12/643,223, filed Dec. 21, 2009, and entitled, “Rotor Bearing Assembly,” which is incorporated herein by reference in its entirety, and in turn claims priority to U.S. Provisional Patent Application No. 61/140,939 filed Dec. 27, 2008, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    This section provides background information to facilitate a better understanding of the various aspects of the invention. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art. 
         [0003]    Submersible pumping systems have been employed in the pumping of oil and water from wells for many years. Commonly, a submersible pumping system comprises an electric motor, a motor protector and a pump suspended colinearly in a well by tubing or cable. The pump is generally a centrifugal pump which is coupled to the motor. The motor rotates a power transmission shaft that concurrently operates the pump. The motor and motor protector are filled with oil to aid in heat dissipation, to maintain proper internal lubrication of the motor, and to separate the internal components of the motor from surrounding wellbore fluids. 
         [0004]    Because these pumping systems are generally disposed within a narrow well, the motor, motor protector, and pump are generally long and cylindrically shaped. The motors vary in horsepower depending on the application. Accordingly, the motors of submersible pumping systems can be quite long leading to particular difficulties not encountered in other electric motor applications. 
         [0005]    The motors of submersible pumping systems typically comprise a stator secured within a tubular housing and a rotor secured to a power transmission shaft that rotates within the stator. The rotor typically is made up of a number of rotor sections, the number of rotor sections depending upon the length and power rating of the motor. Generally, each rotor section comprises laminated steel plates or disks secured by copper rods. The rotor sections are spaced apart from each other, and a rotor bearing assembly is located between each rotor section. Each rotor section is connected to the shaft so that all of the rotor sections rotate as the shaft rotates. 
         [0006]    Each rotor bearing assembly within a rotor section acts to support the shaft and to maintain it in proper axial alignment. A rotor bearing assembly comprises a sleeve connected to the shaft so that the sleeve and shaft rotated together and a journal (e.g., bearing, bushing) disposed coaxially around the sleeve. The sleeve and journal are rotatively coupled to one another. The journal may be configured to frictionally engage the inner wall of the stator (e.g., housing) to prevent the journal from rotating and to maintain proper alignment of the shaft. Thus, a portion of the rotor bearing assembly is rigidly coupled to the shaft but not to the stator. 
         [0007]    Due to the high operating temperatures within the well, thermal expansion tends to cause the shaft, rotor, and stator to grow axially. Generally, the rotor and shaft tend to grow axially downward during high temperature operation. The stator also tends to grow axially downward, however, to a lesser extent than the rotor and the shaft. Due to these thermal expansion effects, the motor is constructed so that each rotor bearing assembly attached to the motor shaft within a rotor section offers a limited amount of axial mobility. Thus, because each rotor bearing assembly is coupled to the motor shaft, the shaft retains the same limited amount of axial mobility. In some pumps, axial mobility is limited by thrust washers adjacent to each rotor bearing assembly. 
         [0008]    Angular misalignment of the shaft within the motor can occur because the rotor, shaft, and stator are subject to these dimensional changes due to thermal expansion and because of imbalances in the rotating assembly. Misalignment of the shaft during operation opposes the centering, or aligning force of the bearing assembly and causes vibrations within the motor. Excess vibration can lead to premature motor or component failure. 
         [0009]    Ideally, the journal remains stationary while the sleeve, rotor, and shaft are rotating. Rotor bearing assemblies have been used in which the peripheral surface of the journal frictionally engages the inner surface of the stator through metal-to-metal contact, such as via a metallic washer. Such metal-to-metal frictional fit rotor bearing assemblies have a tendency to become loose and then to rotate with the shaft. Rotation of the journal tends to gouge and deface the inner surface of the stator. Once the journal begins to rotate with the shaft, the centering force of the rotor bearing assembly is diminished leading to increasing angular misalignment, vibration, and motor failure. This type of construction is also unsatisfactory because due to thermal expansion of the bearing assembly during motor operation, the journal may tightly engage the stator wall which can cause angular misalignment of the shaft and thus excessive thrust loads onto the thrust bearing surfaces adjacent to the rotor bearing assembly. 
         [0010]    Some electric submersible pumps utilize ceramic carbide (e.g., tungsten carbide, silicon carbide, aluminum nitrite, boron carbide, cobalt) bearings (e.g., sleeve and/or bushing) to resist the abrasive action of sand or other hard particles in the well fluid and to function with very low viscosity lubrication. A major challenge with ceramic carbide devices is securing the mating bearing components in a manner that does not create serious stress raisers that make the ceramic carbide susceptible to cracking. Cracking may be caused by shock loads encountered during shipping, handling or installation. Cracking may also be caused by thermal expansion stresses due to running in a poor lubricant that insufficiently lubricates or cools the bearing, such as low viscosity fluid or in a well fluid with a high gas content. Cracking may also be caused by axial or transverse shocks during operation, particularly as the pump shaft constantly moves upward and downward during gas slugging. A catastrophic pump failure may occur, if even one of the cracked bearings (e.g., sleeves) in the rotor (e.g., impeller) stack actually breaks apart. 
       SUMMARY 
       [0011]    A bearing assembly for a rotating shaft uses a carbide sleeve to prevent wear and carry load. The carbide sleeves provide increased life for rotating components used in the severe environments in the oil and gas industries. Various mechanisms can couple the carbide sleeve to the rotating shaft, including keys, keyways, drive rings, reaction rings, and other members to provide particular benefits. These mechanisms allow the carbide sleeve to bear the compressive load of other components, for example, or to slide axially on the shaft, when needed. This summary section is not intended to give a full description of a rotor bearing assembly. A detailed description with example implementations follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion. 
           [0013]      FIG. 1  is a schematic elevation view of an apparatus according to one or more aspects of the invention utilized in an electric submersible pump. 
           [0014]      FIG. 2  is a cut-away view of a pump motor of an electrical submersible pump according to one or more aspects of the invention. 
           [0015]      FIG. 3  is an enlarged view of a rotor bearing assembly according to one or more aspects of the invention. 
           [0016]      FIG. 4  is schematic illustration of a bearing sleeve according to one or more aspects of the invention disposed on a shaft between impellers. 
           [0017]      FIG. 5A  is a schematic illustration of a bearing sleeve assembly according to one or more aspects of the invention attached to a shaft. 
           [0018]      FIG. 5B  is section view along the line I-I of  FIG. 5A . 
           [0019]      FIG. 6A  is a schematic illustration of another bearing sleeve assembly according to one or more aspects of the invention attached to a shaft. 
           [0020]      FIG. 6B  is section view along the line I-I of  FIG. 5A . 
           [0021]      FIG. 7A  is a schematic illustration of a bearing sleeve assembly according to one or more aspects of the invention. 
           [0022]      FIG. 7B  is a sectional view of the bearing sleeve assembly along the line I-I of  FIG. 7A . 
           [0023]      FIG. 8A  is a schematic, end view of a bearing sleeve according to one or more aspects of the invention. 
           [0024]      FIG. 8B  is a sectional view of the bearing sleeve along the line I-I of  FIG. 8A . 
           [0025]      FIG. 9A  is a schematic end view of a bearing sleeve assembly according to one or more aspects of the invention. 
           [0026]      FIG. 9B  is a schematic view of the bearing sleeve assembly of  FIG. 7A . 
           [0027]      FIG. 10  is sectional view of a bearing sleeve according to one or more aspects of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. 
         [0029]    Aspects of the invention relate to rotor bearing assemblies which may be utilized for example in various types of pumps, compressors separators and the like. For purposes of clarity and brevity, aspects of the invention are described generally with reference to electric submersible pumps and wellbore operations. How to utilize aspects of the invention in devices (e.g., intakes, pumps, compressors, etc.) other than electric submersible pumps will be understood by those skilled in the art in view of this disclosure. 
         [0030]    As used herein, the terms “up” and “down”; “upper” and “lower”; “top” and “bottom”; and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements. Commonly, these terms relate to a reference point as the surface from which drilling operations are initiated as being the top point and the total depth of the well being the lowest point, wherein the well (e.g., wellbore, borehole) is vertical, horizontal or slanted relative to the surface. 
         [0031]      FIG. 1  is an elevation view of a submersible pumping system disposed in a well and depicted as including a pump module and a motor module. Pump module  2  comprises of a pump  4  and an inducer or intake section  6  for the pump. Motor module  8  comprises a motor protector  10  and a motor  12 . The pump module and the motor module are coupled to one another and disposed colinearly within a well  14  and suspended at an appropriate position within well  14  by tubing  16 . Electrical power is provided to the motor by means of a power cable  18 . The fluid of interest (e.g., formation fluid, water, hydrocarbons, etc.) is pumped from the well by the submersible pumping system to the surface through tubing  16  and through well head  20 . 
         [0032]      FIG. 2  illustrates a submersible pump motor  12  in accordance with one or more aspects of the invention. The motor is contained within a housing  22  into which an electrical connector  24  penetrates for transmitting power from cable  18  (See  FIG. 1 ). The motor comprises a rotating group and a non-rotating group. The rotating group includes a power transmission shaft  26 , a rotor section  28  and sleeve  48 . The depicted system comprises multiple rotor sections  28  and sleeves  48 . In the depicted embodiment, sleeve  48  is constructed in whole or in-part of a carbide (e.g., ceramic carbide), including without limitation, tungsten carbide, silicon carbide, aluminum nitrite, boron carbide, cobalt. 
         [0033]    The non-rotating group includes a stator  34  and journal(s)  36 . Depicted stator  34  is constructed of metal laminations. Stator  34  may be configured with slots running axially through the stator body through which windings  38  run. Each journal  36  is disposed circumferentially about a sleeve  48  and is positioned between stator  34  and the respective sleeve  48 . According to one or more aspects of the invention, each rotor bearing assembly  30  comprises a sleeve  48  and journal  36 . Rotor sections  28  lie immediately adjacent above and below each journal  36  in the embodiment depicted in  FIG. 2 . 
         [0034]      FIG. 3  is an enlarged view of a portion of a rotor bearing assembly according to one or more aspects of the invention. Depicted in  FIG. 3 , each rotor section  28  includes a laminated rotor core  40  and a copper end ring  42 . Each rotor section  28  has an outer wall  44  which is spaced apart from the inner wall  46  of stator  34 . According to one or more aspects of the invention, sleeve  48  is constructed of a carbide and is rotatively coupled (e.g., attached) to power transmission shaft  26 . According to one or more aspects of the invention, the bearing assembly comprises one or more features to reduce and/or limit the stress raiser on one or more ceramic carbide features of the bearing assembly. For example, according to one or more aspects of the invention elements may be utilized to limit the torque applied to sleeve  48  and/or to limit the axial or radial load on sleeve  48  relative to a sleeve that does not utilize the features. According to one or more aspects of the present invention, the devices rotatively coupling sleeve  48  to shaft  26  facilitate providing a carbide cylindrical without a carbide torque-transmitting feature such as a keyway or the like formed in the carbide surface of sleeve  48 . 
         [0035]    Rotor sections  28 , while rotatively coupled to shaft  26 , are not individually axially coupled to shaft  26 . The lower most rotor section at the end of shaft  26  is, however, axially locked to the shaft in order to support the other rotor sections. Sleeves  48 , while rotatively coupled to shaft  26  are likewise not axially locked to shaft  26 . Thus, the rotor sections  28  and the sleeves  48  have a certain amount of freedom to move in an axial direction, i.e., either upward or downward due to relative thermal expansion and contraction. In the embodiment depicted in  FIG. 3 , an upper edge or circular rim of sleeve  48 , or a load carrying portion of sleeve  48 , contacts an upper thrust washer  64  which is immediately adjacent to the lowermost lamination of upper rotor section  28 . The lower edge of sleeve  48  contacts a lower thrust washer  64  which is immediately adjacent to the uppermost lamination of the lower rotor section  28 . The thrust washers  64  are constructed of a phenolic laminate. Thus, each sleeve  48  supports the weight of the rotor section  28  immediately above it and transmits any force from that rotor section to the rotor section  28  immediately below. As will be understood by those skilled in the art with reference to the various Figures, sleeve  48  may comprise one or more features to limit the load that is applied to a ceramic carbide portion of sleeve  48 . 
         [0036]    The non-rotating group includes stator  34  and journals  36 . Each journal  36  is disposed circumferentially about a sleeve  48 . Thus, where sleeve  48  and journal  36  abut one another is a rotating interface  50 . Multiple axially disposed cylindrical passageways  52  through journal  36  provide for oil flow through journal  36  in order that the oil filling the motor can communicate with adjacent rotor sections for cooling and lubrication. 
         [0037]    Journal  36  extends radially outward from sleeve  48  to a peripheral surface  54 . Peripheral surface  54  is slightly spaced apart from the inner surface  46  of stator  34  in the depicted embodiment. Clearance between these components is commonly about 0.005″ to about 0.009″. Thus, there is no material-to-material contact between journal  36  and stator  34  in the embodiment of  FIG. 3 . However, according to one or more aspects of the invention as described with reference to the figures that follow, journal  36  may be attached (e.g., coupled) to stator  34  (e.g., a housing) for example by a key extending between peripheral surface  54  and inner surface  46 . 
         [0038]    In the embodiment of  FIG. 3 , the outer peripheral surface of journal  36  presents a pair of annular support regions  60  and  62 . Seals  56  and  58  are positioned within circumferential support regions  60  and  62  and frictionally engage inner surface  46  of stator  34 . Circumferential support regions  60  and  62  are preferably spaced apart from one another. In the depicted embodiment a circumferential support region  60  is disposed adjacent the upper surface of journal  36  and region  62  is disposed adjacent the lower surface. This spacing of the circumferential support regions, and thus the seals, may provide improved resistance to angular misalignment of the shaft. 
         [0039]      FIG. 4  is schematic illustration of a bearing sleeve according to one or more aspects of the invention disposed between impellers. Features of the bearing assembly (e.g., housing, journal) are removed in  FIG. 4  to depict the sleeve assembly. In a compression pump, for example, thrust load generated by impellers  100  is transmitted through the stack of impellers  100  and bearing sleeves  48  to the thrust bearing in the protector (e.g., motor protector  10  of  FIG. 1 ). When a sleeve  48  breaks up, the impeller thrust is transferred to the adjacent diffusers which can cause rapid wear in the abrasive environment of a wellbore for example. According to one or more aspects of the invention, sleeve  48  (e.g., sleeve assembly  49 ) may comprise a feature to transfer the axial thrust load across the ceramic carbide portion of the sleeve thereby, in effect, removing the ceramic carbide sleeve  48  member from the stack for purposes of the axial thrust load. 
         [0040]    Members and/or features of the invention may be utilized in rotor bearing assemblies such as the rotor bearing depicted in  FIG. 3  (e.g., rotor bearing assembly  30  of  FIG. 2 ) as well as other current and prior rotor bearing assemblies. Examples of rotor bearing assemblies utilized in electric submersible pump systems include those disclosed in U.S. Pat. Nos. 5,795,075, 6,091,175 and 6,424,066 all of which are incorporated herein by reference. 
         [0041]    Refer now to  FIGS. 5A and 5B  which illustrates an embodiment of rotor bearing according to one or more aspects of the invention.  FIGS. 4A and 4B  depict a keyless rotor bearing sleeve  48  (e.g., sleeve  48  does not have a keyway) which is driven by a drive ring  66 . In this embodiment, sleeve  48  is a silicon carbide member. Shaft  26  comprises a keyway  68  extending axially along shaft  26 . A depression  70  (e.g., dip) may be provided along a portion of keyway  68  for example to attach the assembly to shaft  26  for example when keyway  68  does not extend the full length and or to a terminal end of shaft  26 . Depression  70  may be described is a reduced diameter portion relative to the outside diameter of shaft  26  and keyway  68 . 
         [0042]    In this embodiment, sleeve assembly  49  assembly includes sleeve  48  member, a key  72  have opposing tabs  74  (e.g., ears), and a drive ring  66 . Sleeve assembly  49  may further comprise a reaction ring  76 . Drive ring  66  comprises a face  78  having a protrusion  80 . Protrusion  80  may be formed in various manners, such as and without limitation as a tab, peg, arm or other portion. In the depicted embodiment, face  78  is a contoured surface (e.g., sinusoidal) which forms protrusion  80 . Protrusion  80  is adapted to mate with notch  82  formed along the shoulder  84  of sleeve  48 . 
         [0043]    The contact between protrusion  80  of drive ring  66  and shoulder  84 , for example at notch  82 , of sleeve  48  generates a small axial force that tends to separate the members. Key  72  couples drive ring  66  and sleeve  48  and tends to maintain face  78  and shoulder  84  in contact countering the separation that may occur for example because of the slack that is provided to address thermal expansion in the rotor and bearing stack. Reaction ring  76  may be disposed along the opposing shoulder (e.g., end) of sleeve  48  from drive ring  66 . Reaction ring  76  and drive ring  66  are coupled to sleeve  48  via key  72  and opposing key tabs  74 . Sleeve assembly  49  provides a mechanism for rotationally locking (e.g., attaching, coupling) sleeve  48  with shaft  26 , so that they rotate together, and allow for axial movement relative to shaft  26  for example to address thermal expansion. Key  72  and drive ring  66  provide a locking mechanism that eliminates a need to cut a keyway in sleeve  48  that creates an undesired stress raiser. Further, the utilization of key  72 , drive ring  66  and optional retainer ring  76  may reduce the axial load that is applied to sleeve  48 , for example by the rotor sections and/or impellers. The locking features, for example key  72 , drive ring  66  and retainer ring  76  may be constructed of various materials such as metal and steel. 
         [0044]      FIGS. 6A and 6B  depict another embodiment of a sleeve assembly according to one or more aspects of the invention. This embodiment depicts a means of coupling or locking one or more components of a rotor bearing assembly with another member. For example,  FIGS. 5A ,  5 B depict sleeve  48  rotationally locked relative to shaft  26  without utilizing a keyway or pressed ring. 
         [0045]    Sleeve  48  is constructed of a carbide material, such as silicon carbide. Sleeve  48  comprises an internal bore  48   a  defined by a tapered internal surface  86 . A cylindrical member  88  (e.g., collet, bushing) having an outer surface  90  and an inner surface  92  forming a bore  88   a  is disposed between sleeve  48  and shaft  26 . Member  88  is a metal member in this embodiment. Outer surface  90  is tapered surface, tapering down in thickness from one end  102   a  of member  88  to the other end  102   b.  Tapered outer surface  90  corresponds with internal tapered surface  86  of sleeve  48 . Member  88  forms an axial (e.g., longitudinal) slit  94  which extends radially through member  88  from the inner surface  92  to outer surface  90  and may extend partially or entirely along the axial length of member  88 . One or more slits  94  may be formed. For example, instead of forming a slit  94  extending the axial length of member  88  it may be desired to utilize one or more slits  94  that extend less than the full axial length of member  88 . Slit(s)  94  permit member  88  to forcefully expand and/or contract in diameter and to provide a friction lock around shaft  26 . According to one or more aspects of the invention sleeve assembly  49 , comprising carbide sleeve  48  and member  88 , may reduce the forces (e.g., loads) applied to the carbide sleeve  48 . Ceramic carbide sleeve  48  is not required to deflect and does not have any stress raising notches, keyways and the like. 
         [0046]    In the depicted sleeve assembly  49 , member  88  receives shaft  26  in bore  88   a  and carbide bearing sleeve  48  is receives member  88  in bore  48   a  (e.g., coaxially aligned with member  88 ). The opposing ends  102   a,    102   b  of inner member  88  extend beyond the axial opposing ends of carbide bearing sleeve  48 . In this embodiment, a member  96  (e.g., collar) is attached to member  88  (e.g., at end  102   b ), for example via threading, adjacent to an end of sleeve  48  (e.g., the bottom end). A hole  98   a  is depicted for connecting a spanner wrench to threadedly couple collar  96  to member  88 . A biasing member  98  is depicted disposed between collar  96  and sleeve  48 . Biasing member  98  (e.g., leaf spring, Belleville spring, wave spring, etc.) maintains the fit of sleeve  48  with member  88  across a range of thermal contraction and expansion of the members relative to one another. According to one or more aspects of the invention, sleeve assembly  49 , comprising member  88  (e.g., metal), carbide sleeve  48  and one or more of collar  96  and biasing member  98  may reduce the axial force applied to carbide sleeve  48 . 
         [0047]      FIGS. 7A and 7B  are schematic illustrations of another embodiment of a rotor bearing sleeve assembly according to one or more aspects of the invention. Bearing sleeve assembly  49  comprises an inner cylindrical member  102  (e.g., liner, sleeve, collar, etc.) having an internal bore  103  adapted for disposing the shaft and sleeve member  48  coaxially disposed over at least a portion of inner member  102 . In the depicted embodiment, sleeve  48  is constructed of a ceramic carbide and inner member  102  is metal. Inner member  102  comprises a terminal lip  104  extending radially away from bore  103 . Terminal lip  102  may have a face (e.g., contoured) providing a protrusion  80  adapted to mate with a notch  82  formed on sleeve member  48  which may prevent rotation of sleeve  48  and inner member  102  relative to one another. In the depicted embodiment a member  96  (e.g., collar, collet) is coupled to end  102   a  (e.g., by threading) of inner member  102  distal from end  102   a  and terminal lip  104 . Thus, inner member  102 , which is metal in this embodiment, extends beyond the ends  47   a,    47   b  of outer sleeve  48  providing a means for transferring an axial load across ceramic carbide sleeve  48  instead of the axial load acting on carbide sleeve  48 , for example as depicted in the embodiment of  FIG. 4 . Assembly  49  depicted in  FIGS. 7A and 7B  may include one or more features to facility attaching sleeve assembly to a shaft for example. Some examples of linking or attaching features include, without limitation, keys, keyways, hooks, threads, assemblies such as depicted in  FIGS. 5A-5B  and  6 A- 6 B. 
         [0048]      FIGS. 8A and 8B  are schematic illustrations of a ceramic carbide bearing sleeve  48  according to one or more aspects of the invention. Sleeve  48  comprises an internal surface  86  defining bore  48   a  and an outer surface  51  which may provide rotating interface  50  with journal  36  as depicted for example in  FIG. 3 . In this embodiment, a metal key  106  is provided at internal surface  86  to rotationally lock sleeve  48  to shaft  26  and key  68  (See  FIGS. 5A ,  5 B). In the depicted embodiment, key(s)  106  are attached to inner surface  86  by a metallurgical bond (e.g., solder, brazing, silver soldering, welding, and sintering). 
         [0049]    Cutting a keyway into the inside diameter of sleeve  48  to engage a loose key, which may engage a shaft keyway, creates as stress raiser. In the depicted embodiment, one or more attachment (e.g., linking, fastening) features  106 , which are depicted as keys in  FIGS. 7A-7B , are attached to the inside diameter of sleeve  48  by a metallurgical bond. The metallurgical bond (e.g., soldering, brazing) forms a joint that is sufficiently strong for the light torque that the key must transmit from the shaft to sleeve  48 . To address the differential thermal expansion of metal key  106  over the axial length of sleeve  48 , key  106  may be constructed in relatively short sections. If greater shear strength and/or greater key engagement are needed, a plurality of keys  106  may be attached to sleeve  48  to increase the shear strength and provide a greater contact between the shaft and sleeve. Metallurgical bonding of metal key(s)  106  to ceramic carbide sleeve  48  introduces a lower stress raiser than a keyway formed in sleeve  48  or a notch formed at an end face of sleeve  48  because it does not create an interruption in the continuous cylindrical surface of sleeve  48 . Additionally, this configuration may provide a shorter sleeve assembly and/or rotor bearing assembly than a traditional bearing assembly. 
         [0050]      FIGS. 9A and 9B  are schematic illustrations of another embodiment of a sleeve according to one or more aspects of the invention. In the depicted embodiment, sleeve assembly  49  comprises a ceramic carbide sleeve  48  coaxially receiving or carried by an inner member  102  (e.g., liner, sleeve) constructed for example of metal. Ceramic carbide sleeve  48  and metal inner member  102  may be coupled by metallurgical bonding. Internal member  102  provides an attachment feature  106  for attaching sleeve assembly  49  for example to a shaft  26  (e.g.,  FIGS. 3 ,  4 ,  5 A,  5 B) for transmission of torque. In the depicted embodiment, attachment feature  106  is a keyway for engaging a key  107  which is coupled to shaft  26 . Depicted key  107  is a loose key disposed in keyway  106  of sleeve assembly  49  and keyway  68  of shaft  26 . Other examples of attachment features  106  include, without limitation, a keys, lugs, holes, threads, and hooks. For example, attachment feature  106  may be a metal key attached to inner member  102  or formed by inner member  102 . In the depicted embodiment of  FIGS. 9A-9B , ends  102   a,    102   b  of inner member  102  extend beyond the ends of sleeve  48  for example to transmit axial loads around sleeve  48 . 
         [0051]    The depicted embodiment further depicts grooves  108 . Scoring ceramic carbide sleeve  48  for example to form grooves  108  may promote controlled cracking of sleeve  48 . In another embodiment, described with reference to  FIGS. 9A-9B , sleeve  48  comprises a plurality of ceramic carbide tiles  112  attached to inner member  102  for example by metallurgical bonding or non-metallurgical connections. The plurality of tiles  112  may alleviate cracking and breaking up compared to a monolithic ceramic carbide component due to thermal expansion and contraction or deflection under load. 
         [0052]    The inner metal member may comprise strain relief features to alleviate problems, due to differential thermal expansion for example, by allowing the metal member  102  to yield in one direction while retaining its strength in another direction. For example, a metal sleeve or liner may include axial slits  94  (e.g., slots) as depicted in  FIGS. 6A-6B . Referring to  FIG. 10 , relief features  110  are depicted formed through inner metal member  102 . In the embodiment depicted in  FIG. 10 , relief features  110  are not formed through ceramic carbide sleeve  48 . 
         [0053]    Metal alloys that are commonly used in electric submersible pumps have a coefficient of thermal expansion (“CTE”) significantly higher than that of ceramic carbide materials used in bearing components. The CTE (microinches/in/F) of tungsten carbide is 3.9, while alloy steels range from about 6.3 to 8.3 (e.g., Monel is 7.8 and Inconel is 6.4). This differential CTE can lead to cracking or spalling of the carbide. To alleviate such problems, the metal components can be made, for example, of iron-nickel or iron-nickel-cobalt alloys having CTE&#39;s more closely matching the CTE of the ceramic carbide members. 
         [0054]    The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the invention. The features and/or aspects of the depicted embodiments are provided for purposes of illustration and description, therefore it will be recognized by those skilled in the art that various features and aspects of the depicted embodiments may be combined with one another in manners not illustrated. Those skilled in the art will appreciate that they may readily use the disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art will also realize that such equivalent constructions do not depart from the spirit and scope of the invention, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the invention. The scope of the invention should be determined only by the language of the claims that follow. The term “comprising” within the claims is intended to mean “including at least” such that the recited listing of elements in a claim are an open group. The terms “a,” “an” and other singular terms are intended to include the plural forms thereof unless specifically excluded. 
         [0055]    Conclusion 
         [0056]    Although exemplary systems and methods have been described in language specific to structural features or techniques, the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as example forms of implementing the claimed systems, methods, and structures.