Abstract:
A process for manufacturing a bearing, which may be used in a tool within a bore hole. The process includes providing a tubular sleeve, applying a hard facing material on an outer surface of the tubular sleeve so that the hard facing material is fixed to the outer surface, and thereafter applying a material layer over the hard facing material so that the material layer is fixed to the hard facing material. The process further includes machining the material layer so that a portion of the material layer is removed, and then machining the inner surface so that only the hard facing material is left as an inner surface. The process further includes machining the inner and outer surfaces to form the bearing. The process further includes placing the bearing into a housing and inserting a mandrel into the bearing, where a hard coating of the mandrel abuts the bearing.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This continuation-in-part application claims the benefit of and priority to U.S. patent application Ser. No. 11/157,730, filed on Jun. 21, 2005, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates to a wear surface, hard facing and process. More specifically, but not by way of limitation, this invention relates to a bearing used in surface facilities as well as down hole tools situated in a well bore, and a process for manufacturing the bearing. 
         [0003]    In the search for oil and gas, operators find it necessary to drill with a down hole tool that utilizes a down hole motor. As those of ordinary skill in the art will appreciate, the down hole motor includes a stationary housing and a concentrically disposed drive shaft, wherein the drive shaft has attached a bit means for boring a bore hole. The mandrel is rotated while concentrically located within the stationary housing. The friction created by the rotation of the stationary housing relative to the rotating mandrel can cause significant problems including wear, deformation and over-heating. Bearings have been developed for use in these tools. Prior art remedies include use of a coating process about the drive shaft, as well as the inner diameter of the stationary housing. Prior art techniques further include use of carbide inserts as well as using standard roller and ball bearing technology. 
         [0004]    At least two prior art coating processes are available, namely the adhesion process and the fusion process. Generally, the fusion process is more reliable than the adhesion process because when fusion occurs, the coating material melts into the carrier metal. One inexpensive adhesion process is spray coating, wherein the coating material bonds to the carrier material only due to adhesion force. There are several commercial adhesion process applications available. 
         [0005]    As those of ordinary skill in the art will recognize, the fusion process requires significant temperature to melt the surface of materials. Thus, large spray heads and large heating sources are required, and wherein these space limitations make it very impractical for the fusion of inner diameter surfaces such as required for the down hole motors. 
         [0006]    As noted earlier, solid carbide and carbide tiles (or splits or balls) are also available for bearings, and wherein the solid carbide and/or carbide tiles are compressed or glued into the inner diameter of a radial bearing. The solid carbide is very sensitive to shock loading, and the filler matrix of the tiles is very sensitive to temperature, which are both problematic. 
         [0007]    Therefore, there is a need for a bearing that can withstand the high temperature and shock loading of down hole applications. There is also a need for an efficient and economical bearing for use with surface equipment and down hole tools. Further, there is a need for a radial bearing used in mud motors. These and many other needs will be met by a reading of the following disclosure. 
       SUMMARY OF THE INVENTION 
       [0008]    A process for manufacturing a bearing is disclosed. The process comprises providing a tubular sleeve having an inner diameter and an outer diameter, and applying a hard facing material on the outer diameter of the tubular sleeve so that the hard facing material is fused onto the outer diameter of the tubular sleeve. The process further includes applying a material layer on the outer diameter of the tubular sleeve so that the material layer is fused onto the outer diameter, and then machining the outer diameter of the tubular sleeve so that a portion of the material layer is removed, and machining the inner diameter of the tubular sleeve so that only the hard facing material is left as an inner diameter. 
         [0009]    The process may further comprise cutting the length of the tubular sleeve, and thereafter machining the outer diameter of the tubular sleeve. The process may include grinding the inner diameter of the tubular sleeve in order to form the bearing. In one preferred embodiment, the hard facing material is selected from the group consisting of: tungsten carbide, silicon carbide, or ceramics. Also, the material layer comprises a ductile carbon steel, in one preferred embodiment. 
         [0010]    The step of applying the hard facing material may include rapidly cooling the hard facing material, and wherein the step of rapidly cooling may include cooling the hard facing material (post application) from approximately 3500 degrees Fahrenheit to approximately 200 degrees Fahrenheit in roughly two (2) to five (5) minutes. Additionally, the step of rapidly cooling may further include forming micro cracks within the hard facing material. 
         [0011]    Also disclosed is a process for manufacturing a radial bearing for use in a down hole mud motor. The process comprises providing a tubular sleeve having an inner diameter and an outer diameter, fusing a hard facing material on the outer diameter of the tubular sleeve so that the hard facing material is applied onto the outer diameter of the tubular sleeve, and fusing a material layer on the outer diameter of the tubular sleeve so that the material layer is applied onto the outer diameter. The process further includes machining the outer diameter of the tubular sleeve so that a portion of the material layer is, removed, and machining the inner diameter of the tubular sleeve so that only the hard facing material is left as an inner diameter. The operator could then cut the length of the tubular sleeve, machine the outer diameter of the tubular sleeve, and then machine the inner diameter of the tubular sleeve in order to form the radial bearing. The process further includes placing the radial bearing into a housing, and inserting a mandrel into the radial bearing, and wherein the outer diameter of the mandrel has a hard coating so that the hard coating of the mandrel abuts the radial bearing. In one preferred embodiment, the tubular sleeve is constructed with a carbon steel material, the material layer may be a soft carbon steel, and the hard facing material is selected from the group consisting of: tungsten carbide, silicon carbide, or ceramics. Also, the step of fusing the hard facing is performed using a laser process, in the most preferred embodiment. 
         [0012]    Also disclosed is a down hole mud motor for rotating a bit in a well bore. The down hole mud motor comprises a stationary tubular housing and a radial bearing concentrically disposed within the tubular housing. The radial bearing is produced by fusing a first material to an outer surface of a core sleeve, fusing a second material to the outer surface, and machining the core sleeve so that the radial bearing comprises the first material and the second material. The down hole mud motor further comprises an inner mandrel concentrically disposed within the tubular housing, and wherein the inner mandrel has a hard coating applied to an outer diameter of the inner mandrel so that the hard coating and the radial bearing abut. The inner mandrel is capable of rotating the bit. In one preferred embodiment, the housing has an opening for placement of a punch means for punching and removing the radial bearing from the stationary tubular housing. 
         [0013]    In yet another embodiment, there is disclosed a process for manufacturing an inner wear surface of a radial bearing for use in a down hole mud motor. The process comprises providing a cylindrical member having an outer diameter and applying a hard facing material on the outer diameter of the cylindrical member so that the hard facing material is fixed onto the outer diameter of the cylindrical member. The process further includes applying a material layer on the outer diameter of the cylindrical member so that the material layer is fixed onto the outer diameter of the cylindrical member and machining the outer diameter of the cylindrical member so that a portion of the material layer is removed. In preferred embodiment, the cylindrical member is a rod and the process further comprises drilling out the rod so that only the hard facing material is left as an inner diameter. The process further includes cutting the length of the rod, machining the outer diameter of the tubular sleeve, and grinding the inner diameter of the tubular sleeve in order to form an inner wear surface of a radial bearing. The process may further include placing the radial bearing into a housing, and inserting a mandrel into the radial bearing, and wherein the mandrel has an outer diameter that has a hard coating so that the hard coating of the mandrel abuts the inner wear surface of the radial bearing. 
         [0014]    An advantage of the present invention includes use of an outer diameter fusion process which eliminates the need for separate radial bearing systems and components. Another advantage is that the radial bearing product of the present invention is stronger and more rugged than prior art bearings. Yet another advantage is that the coating of the present invention will endure the severe temperature and shock loads imposed on down hole tools employed in boring holes in subterranean formations. 
         [0015]    Another advantage of the present invention is that no radial bearing components are needed other than the housing and mandrel, which are an integral part of a radial bearing. Thus, a more robust mandrel and housing can be used since more radial space is available within the housing. Accordingly, more loading capacity and better reliability are experienced with the radial bearing of the present disclosure. 
         [0016]    Yet another advantage is the rapid cooling of the hard facing material in one embodiment which allows for good particle distribution. Also, the rapid cooling process allows, in one preferred embodiment, for the formation of micro cracks in the hard facing material. 
         [0017]    A feature of the present invention is that the materials used are applied to the outer diameter of a core sleeve. Another feature is that the outer diameter of the core sleeve, with the materials of the present invention applied thereto, can be machined with conventional tools. Still yet another feature is that the core sleeve, after application of the various materials, can be machined from the inner diameter using known milling and grinding tools. A feature of the present invention is that the starting tubular sleeve may be of sufficient length that it is possible for the operator, after the application of the various layers and machining of the outer and inner diameter, to cut the bearings into several predetermined lengths so that a plurality of bearings are produced, which will result in cost savings and lessen the manufacturing time. 
         [0018]    In another embodiment, a process for manufacturing a radial bearing for use in a down hole mud motor may include providing a tubular sleeve having a first inner surface and a first outer surface and fusing a hard facing material on the first outer surface of the tubular sleeve to form a second outer surface of the tubular sleeve. The process may include fusing a material layer on the second outer surface of the tubular sleeve to form a third outer surface of the tubular sleeve. The process may include controlled cooling the hard facing material from a process temperature of about 3500 degrees Fahrenheit to a temperature of about 500 degrees Fahrenheit in a material specific time period in the range of two to five minutes. The third outer surface of the tubular sleeve may be machined so that a portion of the material layer is removed, and the first inner surface of the tubular sleeve may be machined to form a second inner surface of the tubular sleeve composed of the hard facing material. The process may also include cutting the length of the tubular sleeve, machining the third outer surface of the tubular sleeve, machining the second inner surface of the tubular sleeve in order to form a radial bearing. The radial bearing may be placed into a housing and a mandrel may be inserted into the radial bearing. The mandrel may have an outer surface with a hard coating so that the hard coating of the mandrel abuts the radial bearing. 
         [0019]    The process may further include slowly cooling the material layer after the material specific time period by providing an insulation layer around the third outer surface of the tubular sleeve. The material layer may cooled to a temperature of 250 degrees Fahrenheit with the insulation layer around the third outer surface of the tubular sleeve. The tubular sleeve may be constructed of hard plastic, carbon steel, stainless steel, or inconel material. The step of fusing the hard facing material may be performed using an oxygen settling process or a laser process. The material layer may be a soft carbon steel, stainless steel, or inconel material. The hard facing material may be a tungsten carbide, silicon carbide, or ceramic. The step of machining the second inner surface may be performed with a grinder tool. The tubular sleeve may be cut into a plurality of parts so that a plurality of tubular sleeves are formed. 
         [0020]    In another embodiment, a process for manufacturing a bearing may include providing a tubular sleeve having a first outer surface and a first inner surface, applying a hard facing material on the first outer surface so that the hard facing material is fused onto the first outer surface to form a second outer surface of the tubular sleeve, and applying a material layer on the second outer surface so that the material layer is fused onto the second outer surface to form a third outer surface of the tubular sleeve. The process may include controlled cooling the hard facing material from a process temperature of about 3500 degrees Fahrenheit to a temperature of about 500 degrees Fahrenheit in a material specific time period in the range of two to five minutes. The third outer surface of the tubular sleeve may be machined so that a portion of the material layer is removed, and the first inner surface of the tubular sleeve may be machined to form a second inner surface composed of the hard facing material. 
         [0021]    The process may further include slowly cooling the material layer after the material specific time period by providing an insulation layer around the third outer surface of the tubular sleeve. The material layer may cooled to a temperature of 250 degrees Fahrenheit with the insulation layer around the third outer surface of the tubular sleeve. The process may further include cutting the length of the tubular sleeve, machining the third outer surface of the tubular sleeve, and grinding the second inner surface of the tubular sleeve in order to form the radial bearing. The hard facing material may be tungsten carbide, silicon carbide, or ceramic. The material layer may be a ductile carbon steel, stainless steel, or inconel material. The controlled cooling of the tubular sleeve may include rapidly cooling the hard facing material which may involve forming micro cracks within the hard facing material. The process may further include slowly cooling the material layer after the material specific time period. The step of slowly cooling the material layer may include providing an insulation layer around the third outer surface of the tubular sleeve. The material layer may cooled to a temperature of 250 degrees Fahrenheit with the insulation layer around the third outer surface of the tubular sleeve. The step of slowly cooling the material layer may prevent the formation of major cracks in the material layer. 
         [0022]    In yet another embodiment, a process for manufacturing a wear surface may include providing a structure having a first surface and a second surface opposing the first surface, applying a hard facing material on the first surface so that the hard facing material is fixed to the first surface, and applying a material layer over the hard facing material so that the material layer is fixed to the hard facing material. The process may also include controlled cooling the hard facing material from a process temperature of about 3500 degrees Fahrenheit to a temperature of about 500 degrees Fahrenheit in a material specific time period in the range of two to five minutes, then slowly cooling the material layer by providing an insulation layer over the material layer. The process may further include machining the structure so that a portion of the material layer is removed, and machining the second surface of the structure to expose the hard facing material in order to form a wear surface. 
         [0023]    In still another embodiment, a process for manufacturing an inner wear surface of a radial bearing for use in a down hole mud motor may include providing a cylindrical member having a first outer surface, applying a hard facing material on the first outer surface so that the hard facing material is fixed onto the first outer surface to form a second outer surface of the cylindrical member, and applying a material layer on the second outer surface so that the material layer is fixed onto the second outer surface to form a third outer surface of the cylindrical member. The process may include controlled cooling the hard facing material from a process temperature of about 3500 degrees Fahrenheit to a temperature of about 500 degrees Fahrenheit in a material specific time period in the range of two to five minutes, then slowly cooling the material layer by providing an insulation layer over the third outer surface of the cylindrical member. The process may also include machining the third outer surface of the cylindrical member so that a portion of the material layer is removed, and drilling out the cylindrical member to expose the hard facing material which forms an inner surface of the cylindrical member in order to form an inner wear surface of the radial bearing. The cylindrical member may be a rod. The process may further include cutting the length of the rod, placing the radial bearing into a housing, and inserting a mandrel into the radial bearing. The outer surface of the mandrel may have a hard coating so that the hard coating of the mandrel abuts the inner wear surface of the radial bearing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1  is a cross-sectional view of a core sleeve of the present invention. 
           [0025]      FIG. 2  is a cross-sectional view of the core sleeve of  FIG. 1  with a first coating applied thereto. 
           [0026]      FIG. 3  is a cross-sectional view of the core sleeve of  FIG. 2  with a second coating applied thereto. 
           [0027]      FIG. 4  is a cross-sectional view of the core sleeve of  FIG. 3  having been machined on the outer diameter. 
           [0028]      FIG. 5  is a cross-sectional view of the core sleeve of  FIG. 4  having been machined on the inner diameter. 
           [0029]      FIG. 6  is a cross-sectional view of the core sleeve of  FIG. 5  having been machined on the outer diameter. 
           [0030]      FIG. 7  is a cross-sectional view of the core sleeve of  FIG. 6  having been machined on the inner diameter. 
           [0031]      FIG. 8  is a partial cross-sectional view of the core sleeve of  FIG. 7  concentrically disposed within a housing of a mud motor. 
           [0032]      FIG. 9  is a partial cross-sectional view of a mandrel with a hard coating applied to the outer diameter. 
           [0033]      FIG. 10  is a partial cross-sectional view of the mandrel within the housing of a mud motor. 
           [0034]      FIG. 11A  is a schematic illustration of a preferred embodiment of the hard facing material and the material layer which had undergone a controlled and rapid cooling. 
           [0035]      FIG. 11B  is a schematic illustration of the one embodiment of the hard facing material and the material layer which had not undergone rapid cooling. 
           [0036]      FIG. 11C  is a schematic illustration of the one embodiment of the hard facing material and the material layer which had not undergone controlled applying and cooling. 
           [0037]      FIG. 12  is a schematic illustration of the micro cracks formed in the hard facing material after rapid cooling. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0038]    Referring now to  FIG. 1 , a cross-sectional view of a core sleeve  2  of the present invention is shown. The core sleeve  2  is made up from easy weldable and machinable material such as carbon steel in the preferred embodiment. The core sleeve  2  can also be constructed of a hard plastic. The core sleeve  2  has an outer diameter surface  4  and an inner diameter surface  6 . As will be more fully set out, it is important to retain an accurate measurement of the outer diameter surface  4 . 
         [0039]      FIG. 2  is a cross-sectional view of the core sleeve  2  of  FIG. 1  with a first coating applied thereto. More specifically, the operator will apply a layer of hard facing to the outer diameter surface  4 . In the most preferred embodiment, the fusion process is utilized. An oxygen settling process or a laser process, both of which are commercially available, can be utilized in this hard facing step. In the most preferred embodiment, the laser process is utilized as set out below. Also in the most preferred embodiment, the hard facing material can be selected from the group consisting of tungsten carbide, silicon carbide or ceramics, all of which are commercially available. In the most preferred embodiment, tungsten carbide is used, and is commercially available. Thus, the hard facing material does not have to be heated up above temperatures that would change the mechanical property of the core or carrier sleeves. Also, very hot application temperatures can cause cracks in the structure (of the hard facing material) of the wear particles. 
         [0040]    As noted earlier, in the most preferred embodiment, a laser assisted procedure with inert gas coverage is used to apply the hard facing, and the temperature should not exceed 3500 degrees Fahrenheit. It should be noted that it is also possible to use a high velocity oxygen fuel process system (HVOS) in order to apply the hard facing to the outer diameter surface  4 . Both the HVOS and the laser assisted procedure is commercially available. The hard facing application in effect generates a new outer diameter surface  8 . 
         [0041]    Referring now to  FIG. 3 , a cross-sectional view of the core sleeve  2  of  FIG. 2  with a second coating applied thereto will now be described. More specifically, the process would include applying a layer of metal (material layer) on the top of the previously applied hard facing surface  8 . Thus, a new outer diameter surface  10  is formed. In this step, the operator applies a layer of metal on top of the hard facing. In the most preferred embodiment, the same process that was used for applying the hard facing is used in the step shown in  FIG. 3 . Also, the same set up is used, namely a laser assisted procedure with inert gas coverage while not going over temperatures above 3500 degrees Fahrenheit. The metal should have high ductility and medium yield i.e. soft carbon steel. In the most preferred embodiment, the metal used in  FIG. 3  is commercially available. 
         [0042]      FIG. 4  is a cross-sectional view of the core sleeve  2  of  FIG. 3  having been machined on the outer diameter  10 . In the preferred embodiment, a commercial lathe can be used. It is important to keep as close as possible to a cylindrical shape. Hence, this first cut is referred to as rough since it is important to get a cylindrical shape so that the inner diameter can be measured and machined, as will be discussed in more detail. 
         [0043]    Referring now to  FIG. 5 , a cross-sectional view of the core sleeve  2  of  FIG. 4  having been machined on the inner diameter  6  will now be described. A commercially available lathe can also be used. Hence, the operator will utilize known techniques to machine out the inner diameter  6  to a specific dimension, the specific dimension depending on the specific size mud motor used, thereby exposing a new inner diameter surface  12 . Additionally, the core sleeve  2  is cut to a specific length L, wherein the length L corresponds to the mud motor dimension as will be more fully set out later in the disclosure. The type of tool used to cut the length may be a commercially available saw. It should be noted that it is within the teachings of this invention that the starting tubular sleeve may be of sufficient length that it is possible for the operator, in this step, to cut several bearings to a predetermined length from this single piece. In other words, the finished bearing of  FIG. 5  may be cut into a plurality of bearings so that several bearings are produced, which will save on manufacturing cost and improve time efficiency. 
         [0044]    In  FIG. 6 , the cross-sectional view of the core sleeve  2  of  FIG. 5  having been machined on the outer diameter surface  10  to the specific dimensions and tolerances of the mud motor is shown. Therefore,  FIG. 6  depicts a new outer diameter surface  14  having been exposed through machining. A commercially available lathe may be used in this step. Referring now to  FIG. 7 , a cross-sectional view of the completed bearing, which is represented by the numeral  15 . Hence, bearing  15  is the core sleeve  2  of  FIG. 6  having been machined on the inner diameter thereby producing a new inner diameter surface  16 . In the most preferred embodiment, this cut is the final machine to the inner diameter area to given specifications and tolerances. The type of tool used to machine the inner diameter, in one preferred embodiment, is a grinding type of tool well known in the art. The steps illustrated in  FIGS. 4 through 7  represent the most preferred embodiment of manufacturing the bearing  15  and were done in this specific order, and wherein this specific order has been shown by experimentation to prevent deformation of the bearing  15  due to residual stress generated when machining. Another option to reduce residual stress caused when machining is a controlled heat stress relieve process which entails controlled heating and cooling procedures of the bearing. 
         [0045]    Referring now to  FIG. 8 , a partial cross-sectional view of the bearing  15  of  FIG. 7  concentrically disposed within a lower housing  20  of a mud motor is illustrated. The bearing  15  is a product made by the process illustrated in steps of  FIGS. 1 through 7 . The bearing  15  is press fitted in the most preferred embodiment into the inner bore  22  of the lower housing  20 . It should be noted that it is also possible to utilize heat shrinking or welding of the bearing  15  into the inner bore portion  22  of the lower housing  20 . All these processes are commonly used and known throughout the industry. The combination of the outer radial bearing female  15  placed in the lower housing  20  with the mandrel (that will be described in the discussion of  FIG. 9 ) provides a complete radial bearing assembly means of the present invention. 
         [0046]    Returning to  FIG. 8 , the lower housing  20  contains an outer surface  24 , which is generally cylindrical. The inner bore portion  22  contains a first inner diameter portion  26  that extends to a second inner diameter portion  28 , and wherein the inner bore portion  22  contains the radial shoulder  30 . The end  32  of the bearing  15  will abut the radial shoulder  30 . The lower housing  20  has an opening  33   a  for placement of punch means  33   b  for punching and removing the bearing. For instance, the operator may find it desirable to remove and replace the bearing, and therefore, the operator can utilize the punch  33   b  via opening  33   a  to crimp the radial bearing and remove as appropriate. 
         [0047]      FIG. 9  is a partial cross-sectional view of a mandrel  34  with a hard coating  36  applied to the first outer diameter surface  38 . The mandrel  34  may also be referred to as the drive shaft  34 . The hard coating  36  is applied to the outer diameter surface  38  using known techniques of applying metal material, as was discussed with reference to  FIG. 2  above. Returning to  FIG. 9 , the first outer diameter surface  38  extends to a second outer diameter surface  40 , which is an enlarged cylindrical surface. Extending radially inward is the inner bore  42 . Generally, the mandrel  34  is the rotational component of the mud motor, and the mandrel  34  can be attached to a bit means, as will be more fully explained later in the application. 
         [0048]    Referring now to  FIG. 10 , a partial cross-sectional view of the mandrel  34  within the lower housing  20  of a mud motor  44  will now be described. As will be appreciated by those of ordinary skill in the art, mud motors are commercially available from several vendors, and are attached to a drill string  45 . For instance, Baker Hughes Inc. has a commercially available mud motor under the name Navi Drill.  FIG. 10  depicts the lower housing  20  being connected to an upper housing  46 , and wherein the drive shaft  34  (i.e. mandrel  34 ) is disposed therein. The bearing  15  is shown disposed within the lower housing  20  and wherein the bearing  15  will cooperate with the hard coating  36  of the drive shaft  34 . The lower housing  20  and the upper housing  46  is collectively referred to as the housing. With the drive shaft  34  disposed within the housing, a cavity is formed, and wherein the thrust bearing  48  is disposed therein. The purpose of the thrust bearing  48  is to transmit the axial load from the drill string via drive shaft  34  to the bit  50 . 
         [0049]    As understood by those of ordinary skill in the art, the circulation of drilling fluid down the inner portion of the drill string, and through the mud motor  44 , will cause the drive shaft  34  to rotate. The drive shaft  34  will be connected to a bit means  50  for boring a bore hole  52 . The purpose of the radial bearing is to allow rotation of the drive shaft  34  relative to the lower housing  20 , to clutch radial forces and to allow stabilization of the drive shaft relative to the lower housing  20  while minimizing the friction forces. Operators find it desirable to design the mud motors to rotate at 100 to 300 revolutions per minute. Hence, having a bearing section is critical. The present invention allows for an economical and efficient bearing assembly, with a long life as compared to prior art bearing assemblies. 
         [0050]    Referring now to  FIG. 11A , a partial schematic illustration of a preferred embodiment of the hard facing material  60  and the material layer  62 , which have been applied according to the teachings of the present invention, as set out in  FIGS. 1  thru  7 . Additionally, the hard facing material  60  has undergone rapid cooling after application. More specifically,  FIG. 11A  depicts the particulate material  64  suspended within the filler material (seen generally at  66 ). The particulate material  64  may be a carbide and the filler material may be a cobalt or nickel composition, both being commercially available and well known in the art. The hard facing material  60 , which may also be referred to as the wear surface  60 , is the surface that will abut the mandrel. Therefore, the wear surface  60  bears the rotational and radial force (including friction) of the moving components. The material layer  62  will bear the stress imposed during operation. For instance, in the mud motor application, the material layer  62  will bear the normal stress, shear stress, radial stress, etc. 
         [0051]      FIG. 11A  depicts a good distribution of the particulate material. As understood by those of ordinary skill in the art, the hard facing material is applied at temperatures in the 3500 degree Fahrenheit range. One of the methods of obtaining good particle distribution is to rapidly cool the hard facing material after controlled application. In other words, the hard facing material is not allowed to cool normally, but rather is rapidly cooled so that the particles are not allowed to settle. This is done by fast cooling which includes cooling the hard facing, material from a temperature of 3500 degrees Fahrenheit (immediately after application) to a temperature of approximately 500 degrees Fahrenheit in approximately 2 to 5 minutes. Continued rapid cooling beyond this point could result in major cracks in the material layer  62  which could result in portions of the material layer  62  breaking off from the hard facing material. Instead, after the rapid cooling, the material layer  62  may be wrapped or otherwise covered with a layer of insulation and allowed to cool slowly. The material layer may be slowly cooled to a temperature of 250 degrees Fahrenheit with the layer of insulation around the material layer  62 . More preferably, the material layer may be slowly cooled to a temperature of 200 degrees Fahrenheit in this manner. In an alternate embodiment, the material layer may be cooled to ambient temperature in this manner. This subsequent slow cooling step will help to prevent major cracks in the material layer  62  while achieving good particle distribution in the hard facing material  60 . The layer of insulation may be formed of any insulating material. For example, a heat blanket may be used as the insulation layer. 
         [0052]      FIG. 11B  is a partial schematic illustration of one embodiment of the hard facing material and the material layer, wherein the hard facing material had not undergone rapid cooling. In the embodiment seen in  FIG. 11B , the particle distribution is poor. This poor distribution was caused by improper cooling. Referring now to  FIG. 11C , a schematic illustration of another embodiment of the hard facing material and the material layer, wherein the hard facing material has not been applied in a controlled manner. In  FIG. 11C , the particle distribution is poor. This poor distribution was caused by improper cooling, and an improper mixture of the filler material. Thus, according to the teachings of the present invention, the rapid cooling of the hard facing material  60  and the subsequent slow cooling of the material layer  62  will allow for good particle distribution in the hard facing material  60  and will prevent major cracks in the material layer  62 , thereby allowing the hard facing material  60  and the material layer  62  to assist its load and wear function of the bearing. 
         [0053]      FIG. 12  is a schematic illustration of the micro cracks formed in the hard facing material after rapid cooling, according to one preferred embodiment. The micro cracks are represented by the diagonal lines traversing  FIG. 12 . The micro cracks, such as seen at  68 , are introduced into the hard facing material  60  by the rapid cooling. The micro cracks makes the hard facing material flexible. At the same time, the hard facing material  60  is not allowed to chip and fall off. Hence, the hard facing material  60  is flexible, but does not fall off. 
         [0054]    While preferred embodiments of the present invention have been described, it is to be understood that the embodiments described are illustrative only and that the scope of the invention is to be defined solely by the appended claims when accorded a full range of equivalence, many variations and modifications naturally occurring to those skilled in the art from a review thereof.