Abstract:
A protective coating is applied to an inner or an outer member of a rotary fluid bearing by sputtering to minimize scuffing, wear and premature failure of the members during starts and stops of the bearing. The coating may include titanium, tungsten, chromium, amorphous carbon with or without metallic impurities, and hydrogenated amorphous carbon with or without metallic impurities. One of the members is formed in two sections to accommodate assembly of the bearing and these sections abut at end faces. Features on each end face are imparted to the other end face in a compression coining process to facilitate rapid and repeatable alignment of the two sections when separated and rejoined during subsequent manufacturing steps.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     This invention relates in general to bearings and more particularly to a rotary fluid bearing and a process for manufacturing the same. 
     The typical fluid bearing includes a journal and a hub, one of which rotates with respect to the other. Sometimes a small electric motor is integrated into the journal and hub to effect the rotation. The journal and hub have matching surfaces which, during the operation of the bearing, are separated by a thin layer of fluid. In this sense, a fluid may comprise any material, such as a liquid or gas that possesses fluid properties or characteristics. Hence, the surfaces do not contact each other and essentially no friction exists to impede the rotation. The fluid for the layer, and the pressure associated with the fluid, may come from an external source (hydrostatic) or it may derive from the rotation itself (hydrodynamic). Bearings which operate on the latter principle normally have grooves in the surfaces of the journal or hub to elevate the fluid pressure in the gap between opposed thrust-oriented surfaces. Such bearings are referred to as self-acting bearings. 
     However, the journal and hub in a self-acting bearing contact one another when the bearing is not rotating or otherwise not in use. Each time the bearing activates, the hub and journal surfaces that are in contact rub against one another during initial rotation, that is, before sufficient fluid pressure separates the surfaces. The journal and hub surfaces thereby suffer scuffing and wear, which leads to inefficiency and premature failure. If one of the bearing members has an epoxy or resin liner that chemically reacts with the metal of the opposing bearing member, such as aluminum or steel, physical contact between the members intensifies the inefficiencies and accelerates premature failure. 
     Further, in certain configurations the self-acting fluid bearing has its opposed thrust-oriented surfaces tapered, indeed, down from each end toward the mid-region of the bearing. The tapers, in effect, capture the hub on the journal, but this presents manufacturing problems. In this regard, the tapered regions of the journal are normally manufactured separately and then assembled within the hub. Since the two tapered regions are not machined on the same center, the possibility exists that their axes may not coincide precisely as they must when assembled in the hub. This can produce error in motion. In addition, the surfaces conjoining between the two tapered regions must be manufactured so as to prevent any slippage at the interface during bearing rotation. 
     SUMMARY OF THE INVENTION 
     The present invention resides in the formulation for, and process of applying, a coating on one or more of the internal members of the bearing that has a lower coefficient of friction and lower chemical reactivity than the material it coats, and in the “coining” of features on the abutting end faces of two separable sections of the internal bearing member. 
     The present invention greatly reduces the scuffing and wear associated with starting and stopping the bearing, and eliminates the chemical reaction between the liner and opposing metal bearing components, through the application of a specially formulated and applied coating on one or more of the internal members of the bearing. The coating may also be formulated to increase the hardness of the substance it coats. 
     The present invention also resides in “coining” features onto the surfaces of the tapered sections abutting one another that thereafter properly mate with one another in only one position. The present invention provides an alignment mechanism that also eliminates lateral slippage of the sections when they are conjoined. In this way, the sections can be quickly, reliably and repeatably aligned together properly to enable multiple manufacturing steps that separate and rejoin the sections, including final bearing assembly. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     In the accompanying drawings, which form part of the specification and wherein like numerals and letters refer to the like parts, wherever they occur: 
     FIG. 1 is a perspective view, partially broken away and in section, of a fluid bearing constructed in accordance with the process of and embodying the present invention; 
     FIG. 2 is an elevational view of the journal for the bearing; 
     FIG. 3 is a sectional view of the hub for the bearing with the polymer liner and grooves in the liner; 
     FIG. 4 is a perspective view of both sections of the journal, separated, and at an early process stage; 
     FIG. 5 is a perspective view of both sections of the journal, separated, and at an intermediate process stage prior to “coining”; 
     FIG. 6 is a perspective view of both sections of the journal, pressed together during the “coining” process; 
     FIG. 7 is a perspective view of both sections of the journal, separated, after “coining”; 
     FIG. 8 is a lateral view of both sections of the completed journal, separated and rotated to expose the “coined” surfaces; 
     FIG. 9 is a cross-sectional view of the protective coating on the journal. 
    
    
     Corresponding reference numerals will be used throughout the several figures of the drawings. 
     DETAILED DESCRIPTION 
     In the preferred embodiment, a self-acting fluid bearing A (FIG. 1) includes a fixed journal  2  and a rotary hub  4  which fits around the journal  2  where it revolves about an axis X of rotation, the common axis of the journal  2  and the hub  4 . The journal  2  constitutes the inner member of the bearing A, whereas the hub  4  represents the outer member. The journal  2  has a low friction coating C bonded to it. The hub  4  has a molded liner  6  bonded to it, with the liner  6  being presented inwardly toward the journal  2  such that small gaps G exist between the liner  6  and coating C on the journal. A fluid component is present in the gaps G. This fluid consists of air in the preferred embodiment, but may comprise any substance, including gases and liquids, that exhibits fluid characteristics. Further, the bearing A may contain an electric motor  8  which, when energized, imparts torque to the hub  4 , causing the hub  4  to rotate about the axis X at high velocity. 
     The journal  2  is formed from a hardenable steel, such as  440 C, and exists in two sections  10  and  12  which are held firmly together by a machine screw  14  (FIG.  1 ). The sections  10  and  12 , which are essentially identical, abut along an interface  16 . Each section  10  and  12  has a cylindrical surface  20  and a conical surface  18  which tapers downwardly toward the cylindrical surface  20  (FIG.  2 ), with the conical envelopes formed by the two surfaces preferably having their apices at a common point along the axis X. When the two sections are held together in the bearing A, the conical surfaces  18  of the two sections  10  and  12  are separated by the intervening cylindrical surfaces  20 . At their opposite or large ends, the two sections  10  and  12  have cylindrical spindles  24  which are directed axially beyond the ends of the conical surfaces  18 . 
     The journal  2  also contains a through bore  26  that extends axially between the two spindles  24  and indeed opens out of the ends of the journal  2  at the spindles  24 . The through bore  26 , which likewise has its axis coincident with the axis X, receives the screw  14  which holds the two sections  10  and  12  firmly together at an interface  16 . 
     The hub  4  is formed from a light weight and durable substance, such as aluminum, in two axially aligned sections  36  and  38  (FIG. 3) which are held together by a suitable clamping device. The hub  4  has conical surfaces  40  which are presented inwardly toward the axis X and taper downwardly to an intervening cavity  42  that lies between them and is accessible when the sections  36  and  38  are separated. The cavity  42  houses the motor  8 . At their opposite ends the conical surfaces  40  open into short end bores  44  which, in turn, open out of the ends of the hub  4 . The conical surfaces  40  of the hub  4 , insofar as their taper is concerned, conform to the conical surfaces  18  of the journal  2 , but are somewhat larger. Indeed, the conical surfaces  40  of the hub  4  lie between 0.005 and 0.04 inches, and preferably about 0.015 inches, measured radially, beyond the coating C on the opposing conical surfaces  18  of the journal  2 . This spacing far exceeds the size of the gaps G. 
     The liner  6  has spiral grooves  32 , which open out atop the conical surfaces  40  of the hub  4 , yet are quite shallow. The process for forming the grooves  32  in the liner  6  is explained in Timken&#39;s co-pending U.S. patent application Ser. No. 09/403,881, filed on Oct. 15, 1999, and International Patent No. WO 98/46894, published on Oct. 22, 1998, both entitled “ROTATRY AIR BEARING AND PROCESS FOR MANUFACTURING THE SAME.” The grooves  32  extend all the way out to the large ends of the conical surfaces  40 , near to the end bores  44 , but terminate short of the small ends so that continuous or smooth frustoconical lands  34  exist atop the conical surfaces  40  between the ends of the grooves  32  and the cylindrical intervening cavity  42 . The grooves  32  serve to pressurize the fluid F in the gaps G, when the hub  4  revolves about the journal  2 , particularly in the regions around the lands  34 . 
     The low friction liner  6  (FIG. 1) bonds to the conical surfaces  40  of the hub  4  and occupies most of the space between those surfaces and the coating C on the conical surfaces  18  and of the journal  2 . It too has conical surfaces  46  which conform in taper to the tapered surfaces  18  of journal  2 , yet lie slightly beyond the surfaces  18 , so that small clearances exist between the conical surfaces  46  of the liner  6  and the conical surfaces  18  of the journal  2  when the bearing A is in operation. Those clearances form the gaps G which, measured radially, should range between 30 and 100 microinches, and preferably about 50 microinches. The liner  6  has a generally consistent thickness across the conical surfaces  40  of hub  4 . The liner  6  derives from a replicant, such as epoxy resin, which when hardened on the hub  4 , should have a low coefficient of friction against a smooth steel surface, such as the conical surfaces  18  of the journal  2 . Resins sold by Master Bond, Inc. of Hackensack, N.J., under the trademark MASTER BOND possess the desired characteristics and are suitable for the liner  6 . 
     Finally, in this embodiment the bearing is motorized. The motor  8 , which may be a brushless D.C. motor, mounts upon the intervening surface  20  of the journal  2  and within the cavity  42  of the hub  4 . The leads for supplying the motor  8  with electrical energy pass through the bore  26  in the journal  2 . When energized, the motor  8  exerts a torque on the hub  4 , causing the hub  4  to rotate around the journal  2 . 
     Initially, before the motor  8  is energized, some of the conical surfaces  46  of the resin liner  6  may rest against the coating C on the conical surfaces  18  of the journal  2 . However, as the hub  4  accelerates, it pressurizes the air in the gaps G, particularly in the regions between the conical surfaces  18  of the journal  2  and the frustoconical regions  34  on the conical surfaces  46  of the liner  6 . A layer of air develops in the gaps G for the full circumferences of the gaps G, and the hub  4  and its liner  6  separate from the journal  2  and the coating C on the journal and, in effect, float on the cushion of air in the gaps G. The air pressure necessary to sustain the separation between the journal  2  and hub  4  derives from the rotation itself, or in other words, the bearing A acts as a pump which forces fluid F, in this case air, into the gaps G. With the conical surfaces  46  and the coating C on the opposing conical surface  18  being separated by a layer of air, essentially no friction exists between the hub  4  and the journal  2 , and the air, having extremely low viscosity, does little to impede the rotation. The hub  4  rotates freely and carries a payload, such as a disk or a multi-surface mirror. 
     Were it not for the coating C, each time the motor  8  is initially energized or each time the journal  2  and hub  4  of the fluid bearing otherwise rotate against each other, the conical surfaces  46  of the resin liner  6  would rub against the conical surfaces  18  of the journal  2 , causing friction, scuffing and/or other wear at those surfaces. In addition, chemo-mechanical reactions between the materials composing the liner  6  and the conical surfaces  18  might result in undesirable oxidation at the interface. Such wear and oxidation lead to bearing inefficiencies and premature failure. The coating C provides low friction and hardness, thereby allowing the liner  6  and surfaces  18  to freely slide over one another with minimal scuffing or wear. The coating C also exhibits a low chemical reactivity to the material in the surfaces  18  that thereby insulates the liner  6  from the surfaces  18 , and inhibits chemical reaction between them. Hence, the incorporation of coating C onto the surfaces  18  markedly reduces the risk of premature fluid bearing failure. 
     The coating C (FIG.  9 ), having a thickness significantly thinner than the gap G, is applied to the journal  2 , and comprises an adhesion layer C 1 , a gradient layer C 2 , and a final layer C 3 . The adhesion layer C 1  enhances the adhesion between the coating C and the surface of the journal  2  through physical and chemical bonding. The gradient layer C 2  provides a stress-relieving buffer zone in the form of a gradual compositional transition from material comprising the adhesion layer C 1  to the material comprising the final layer C 3 . The gradient layer C 2  minimizes otherwise inherent mechanical weaknesses in the coating caused by interlayer stresses. The final layer C 3  lends the desired characteristics of low friction, hardness, and low chemical reactivity to the surfaces  18  of the journal  2 . Three interfaces are thereby formed along the different layers of coating C. An interface  11  exists between the surface  18  of journal  2  and adhesion layer C 1 , an interface  12  exists between adhesion layer C 1  and the gradient layer C 2 , and an interface  13  exists between the gradient layer C 2  and the final layer C 3 . Both the interfaces  12  and  13 , each constituting a transition between different layers of a single coating C, are somewhat diffuse and indistinct. 
     The coating C may consist of the final layer C 3  essentially comprising sputtered amorphous carbon with titanium impurities, the adhesion layer C 1  essentially comprising sputtered titanium, and the gradient layer C 2  essentially comprising a mixture of sputtered titanium and sputtered amorphous carbon wherein the amorphous carbon content gradually increases across the layer C 2  from essentially 0 atomic percent at the interface  12  with the adhesion layer to a level of 90 to 100 atomic percent, and preferably 95 to 97 atomic percent, at the interface  13  with the final layer. In this configuration, the thickness of adhesion layer C 1  should be between 0.01 and 1.00 micrometers, and preferably about 0.10 micrometers, the thickness of gradient layer C 2  should be between 0.01 and 1.00 micrometers, and preferably about 0.10 micrometers, and the thickness of final layer C 3  should be between 0.10 and 5.00 micrometers, and preferably between 0.80 and 0.90 micrometers. Furthermore, the final layer should have a titanium to carbon impurity level of approximately 1 to 20 atomic percent, and preferably 5 to 15 atomic percent, a physical structure incorporating 1.0 to 3.0 nanometer titanium carbide particles embedded in a matrix of amorphous carbon, a hardness of 5 to 25 gigapascals, and preferably 15 gigapascals, as measured using nanoindention techniques, a dry sliding friction coefficient of approximately 0.02 to 0.14, and preferably less than 0.08, measured at a rate of 50 centimeters per second with a 1.0 gigapascal load at 25% relative humidity, and a rms_ surface roughness of approximately 1 to 10 nanometers, and preferably 5 nanometers. 
     To acquire such a configuration, the coating C is applied to the journal  2  through a continuous sputtering process. First, the journal  2  is placed in an unbalanced magnetron sputtering system and subjected to an argon gas plasma etch to remove contaminants and generate nucleation sites for adhesion. Then, the adhesion layer C 1  is applied using a titanium deposition target. Upon reaching the desired adhesion layer thickness, a carbon deposition target is introduced into the ongoing sputtering process to begin depositing amorphous carbon along with titanium. This forms the interface I 2  between the adhesion layer C 1  and gradient layer C 2 . Thereupon, adjustments are made to control settings for the sputtering system to gradually increase the deposition rate of the carbon while simultaneously reducing the deposition rate of the titanium. This forms the gradient layer C 2 . Upon reaching the desired composition for the interface I 3  between the gradient layer C 2  and the final layer C 3 , the sputtering continues uninterrupted while the deposition rates for the amorphous carbon and the titanium thereafter remain constant. Upon achieving the desired thickness for the final layer C 3 , the sputtering system is shut off and the newly coated journal  2  is removed. 
     The coating C may also consist of the final layer C 3  essentially comprising sputtered hydrogenated amorphous carbon with titanium impurities, the adhesion layer C 1  essentially comprising sputtered titanium, and the gradient layer C 2  essentially comprising a mixture of sputtered titanium and sputtered hydrogenated amorphous carbon wherein the hydrogenated amorphous carbon content gradually increases across the layer C 2  from essentially 0 atomic percent at the interface I 2  with the adhesion layer to a level of 80 to 100 atomic percent, and preferably 85 to 95 atomic percent, at the interface  13  with the final layer. In this configuration, the thickness of adhesion layer C 1  should be between 0.01 and 1.00 micrometers, and preferably about 0.10 micrometers, the thickness of gradient layer C 2  should be between 0.01 and 1.00 micrometers, and preferably about 0.10 micrometers, and the thickness of final layer C 3  should be between 0.10 and 5.00 micrometers, and preferably between 2.00 and 3.00 micrometers. Furthermore, the final layer should have a titanium impurity level of approximately 1 to 20 atomic percent, and preferably 5 to 15 atomic percent, a physical structure incorporating 1.0 to 3.0 nanometer titanium carbide particles embedded in a matrix of hydrogenated amorphous carbon, a hardness of 5 to 50 gigapascals, and preferably 15 to 25 gigapascals, as measured using nanoindention techniques, a dry sliding friction coefficient of approximately 0.05 to 0.25, and preferably 0.10 to 0.15, measured at a rate of 50 centimeters per second with a 1.0 gigapascal load at 25% relative humidity and a rms surface roughness of approximately 5 to 25 nanometers, and preferably 10 to 20 nanometers. 
     To acquire such a configuration, the coating C is also applied to the journal  2  through a continuous sputtering process. First, the journal  2  is placed in an unbalanced magnetron sputtering system and subjected to an argon gas plasma etch to remove contaminants and generate nucleation sites for adhesion. Then, the adhesion layer C 1  is applied using a titanium deposition target. Upon reaching the desired adhesion layer thickness, argon and acetylene gases, and a carbon deposition target are introduced into the ongoing sputtering process to begin depositing hydrogenated amorphous carbon along with titanium. This forms the interface I 2  between the adhesion layer C 1  and gradient layer C 2 . Thereupon, adjustments are made to control settings for the sputtering system to gradually increase the deposition rate of the hydrogenated amorphous carbon while simultaneously reducing the deposition rate of the titanium. This forms the gradient layer C 2 . Upon reaching the desired composition for the interface I 3  between the gradient layer C 2  and the final layer C 3 , the sputtering continues uninterrupted while the deposition rates for both the hydrogenated amorphous carbon and the titanium thereafter remain constant. Upon achieving the desired thickness for the final layer C 3 , the sputtering system is shut off and the newly coated journal  2  is removed. 
     The coating C may also consist of the final layer C 3  essentially comprising sputtered hydrogenated amorphous carbon with tungsten impurities, the adhesion layer C 1  essentially comprising sputtered chromium, and the gradient layer C 2  essentially comprising a mixture of sputtered chromium and sputtered hydrogenated amorphous carbon and tungsten wherein the hydrogenated amorphous carbon to tungsten content gradually increases across the layer C 2  from essentially 0 atomic percent at the interface I 2  with the adhesion layer to a level of 80 to 90 or 100 atomic percent, and preferably 85 to 95 atomic percent, at the interface I 3  with the final layer. In this configuration, the thickness of adhesion layer C 1  should be between 0.01 and 1.00 micrometers, and preferably about 0.10 micrometers, the thickness of gradient layer C 2  should be between 0.01 and 1.00 micrometers, and preferably about 0.10 micrometers, and the thickness of final layer C 3  should be between 0.10 and 5.00 micrometers, and preferably between 2.00 and 3.00 micrometers. Furthermore, the final layer should have a tungsten impurity level of approximately 1 to 20 atomic percent, and preferably 10 to 15 atomic percent, a physical structure incorporating 1.0 to 3.0 nanometer tungsten carbide particles embedded in a matrix of hydrogenated amorphous carbon, a hardness of 5 to 30 gigapascals, and preferably 15 to 25 gigapascals, as measured using nanoindention techniques, a dry sliding friction coefficient of approximately 0.05 to 0.25, and preferably 0.10 to 0.15, measured at a rate of 50 centimeters per second with a 1.0 gigapascal load at 25% relative humidity, and a rms surface roughness of approximately 5 to 25 nanometers, and preferably 10 to 20 nanometers. 
     To acquire such a configuration, the coating C is also applied to the journal  2  through a continuous sputtering process. First, the journal  2  is placed in an unbalanced magnetron sputtering system and subjected to an argon gas plasma etch to remove contaminants and generate nucleation sites for adhesion. Then, the adhesion layer C 1  is applied using a chromium deposition target. Upon reaching the desired adhesion layer thickness, argon and acetylene gases, a carbon deposition target and a tungsten deposition are introduced into the ongoing sputtering process to begin depositing hydrogenated amorphous carbon and tungsten along with chromium. This forms the interface I 2  between the adhesion layer C 1  and gradient layer C 2 . Thereupon, adjustments are made to control settings for the sputtering system to gradually increase the deposition rate of the hydrogenated amorphous carbon and tungsten while simultaneously reducing the deposition rate of the chromium. This forms the gradient layer C 2 . Upon reaching the desired composition for the interface  13  between the gradient layer C 2  and the final layer C 3 , wherein the chromium target has been removed from the sputtering operation and the chromium deposition rate essentially equals zero, the sputtering continues uninterrupted while the deposition rates for the hydrogenated amorphous carbon and the tungsten thereafter remain constant. Upon achieving the desired thickness for the final layer C 3 , the sputtering system is shut off and the newly coated journal  2  is removed. 
     In addition, sections  10  and  12  of journal  2  (FIGS. 7 and 8) further comprise a face F 1  and a face F 2 , respectively, where each face F 1  and F 2  is on the end of its respective member opposite the spindle  24  for that member. Both the faces F 1  and F 2  are perpendicular to axis X and mate against one another when the journal  2  is assembled. The faces F 1  and F 2  are both circular, concentric with the axis X, and comprise primarily flat surfaces S 1  and S 2 , respectively, through which passes the through bore  26 . Rising from the face F 1  are ridges R 1  and R 2 , wherein the spines of both ridges are collinear along a diameter of the face F 1 . Likewise, rising from the face F 2  are ridges R 3  and R 4 , wherein the spines of both ridges are collinear along a diameter of the face F 2 . Each ridge, R 1 , R 2 , R 3  and R 4 , possesses a triangular cross-section, it being isosceles with respect to its axis or symmetry and essentially uniform in shape along its full length. 
     The face F 1  also possesses two trenches T 1  and T 2 , wherein the centerline of each trench lies collinear along a diameter of the face F 1  that is perpendicular to the diameter along which lie the ridges R 1  and R 2 . Likewise, face F 2  comprises trenches T 3  and T 4 , wherein the centerline of each trench lies collinear along a diameter of the face F 2  that is perpendicular to the diameter along which lie the ridges R 3  and R 4 . Each trench, T 1 , T 2 , T 3  and T 4 , comprises an inverted triangular cross-section, isosceles with respect to its vertical axis and essentially uniform in shape along its full length. 
     The ridges R 1 , R 2 , R 3  and R 4  and the trenches T 1 , T 2 , T 3  and T 4 , are therefore located such that when the sections  10  and  12  of the journal  2  are positioned coaxially with the axis X, with their respective faces F 1  and F 2  facing one another, the sections  10  and  12  can be rotated such that ridges R 1  and R 2  face and align to trenches T 3  and T 4 , and ridges R 3  and R 4  face and align to trenches T 1  and T 2 . When faces F 1  and F 2  are then brought together, such that their respective surfaces S 1  and S 2  approach or touch one another, the ridges R 1  and R 2  fit snugly into the reciprocal trenches T 3  and T 4 , the ridges R 3  and R 4  fit snugly into the reciprocal trenches T 1  and T 2 , and the journal  2  properly conjoins with the correct angular orientation between its sections  10  and  12 . 
     By constraining the lateral and longitudinal relationship between sections  10  and  12  when both are properly conjoined, the ridges R 1 , R 2 , R 3  and R 4  and the trenches T 1 , T 2 , T 3  and T 4 , thereby act in unison as an orientation means that serves to correctly locate and align the two sections  10  and  12  rotationally about the axis X with respect to each other. 
     Precise fit of the ridges R 1 , R 2 , R 3  and R 4  into the trenches T 1 , T 2 , T 3  and T 4  requires a novel application of a manufacturing process referred to as “coining.” First, each section  10  and  12  is machined to its final shape, less the ridges and trenches, using standard turning practices (FIG.  4 ). Material is then removed from each face F 1  and F 2  to form the ridges R 1 , R 2 , R 3  and R 4  (FIG.  5 ). The faces F 1  and F 2  are then abutted against one another such that both are coaxial with the axis X and the line between the ridges R 1  and R 2  is perpendicular to the line between the ridges R 3  and R 4 . A compressive load is then applied along the axis X in an amount sufficient to press the surface S 1  of the face F 1  against the surface S 2  of the face F 2 , such that the ridges R 1 , R 2  and R 3 , R 4  compress into and plastically deform the surfaces S 2  and S 1 , respectively (FIG.  6 ). This results in the permanent formation of the trenches T 1 , T 2 , T 3  and T 4  that constitute corresponding mirror images to the ridges R 1 , R 2 , R 3  and R 4  (FIG.  7 ). When conjoined, the two sections  10  and  12  form an assembly. The assembly is then ground and superfinished as a single unit, to essentially the final configuration for the journal  2 , to ensure the uniform roundness and concentricity about the axis X between the sections that is critical to proper bearing operation. 
     During final bearing assembly, the two sections  10  and  12  are brought together at interface  16  within the interior of the hub  4  (FIG.  1 ), and the ridges R 1 , R 2 , R 3  and R 4  and trenches T 1 , T 2 , T 3  and T 4  jointly act as a guide to properly align the sections coaxially with the axis X. Upon properly and positively mating the ridges and trenches, the ridges and trenches act as a locking mechanism to secure sections  10  and  12  from undesirable lateral and/or rotational shifts. The two sections  10  and  12  are thereby brought together within the hub  4  such that they are aligned axially as well as rotationally, and are thus in the same orientation with respect to each other as they were during the journal manufacturing process. 
     Variations on the basic construction and process are available. For example, the hub  4  may be stationary and the journal  2  may rotate. The grooves  32  may be formed in the journal  2  instead of the liner  6 . The grooves  32  may be formed in the surfaces  40  of the hub  4  and thereby translated into the form of the liner  6 . The grooves  32  may be formed at the small diameter ends of the conical surfaces of the journal  2  or the hub  4 , rather than the larger ends, and will then be configured to pump away from the intervening surface  20 . 
     The liner  6  may be bonded to the conical surfaces  18  of the journal  2  instead of the surfaces  40  of the hub  4 , in which event the coating C may be applied to the conical surfaces  40  of the hub  4 . The coating C may also be applied to both the surface  18  of the journal  2  and onto the liner  6  bonded to the hub  4 . Alternately, the coating C may be applied to one or both of the surface  40  of the hub  4  and the liner  6  if the liner is bonded to the journal  2 , or the coating C may be applied just on the liner  6  if the liner  6  is bonded to both the hub  4  and the journal  2 . The journal  2  may remain stationary while the hub  4  rotates, or the journal  2  may rotate about a stationary hub  4 . Further, the bearing A may be configured without an integral motor. 
     The coating C itself may consist of one or more layers, and not specifically three, so long as the desired levels of adhesion, and chemical and mechanical durability can be achieved. The coating C may also be applied in a variety of other processes, such as chemical vapor deposition, low pressure chemical vapor deposition, and wet bath chemical deposition, and may be applied in more than one continuous process. Materials, such as chromium, may be used in place of titanium and tungsten for adhesion. The coating C may be formulated to exhibit a hardness greater than that of the substance upon which it is bonded. 
     In addition, the ridges R 1 , R 2 , R 3  and R 4  and their corresponding trenches T 1 , T 2 , T 3  and T 4  may be formed with cross-sectional shapes other than isosceles triangles, may be of different dimensions and may not necessarily be constrained to run collinear with a diameter of the face F 1  or F 2 . Further, the ridges and trenches may be formed earlier or later in the bearing manufacturing process. For example, the entire journal  2  may be first cut and machined from a single piece of bar stock before being split at the center intervening section  20  to allow for formation of the ridges and trenches. The above-described “coining” process may also be utilized on the two sections  36  and  38  of the hub  4 . 
     As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.