Bearing assembly

Provided are bearing assemblies including one or more substrate assemblies, such as thrust bearing assemblies. The substrate assemblies include a bearing element fixed to a substrate. The bearing elements are formed from a thermally stable material such as a ceramic-bonded diamond composite. Methods for manufacturing the bearing assemblies are also provided.

FIELD OF THE DISCLOSURE

The present disclosure relates to bearing assemblies, in particular thrust bearing assemblies including at least one substrate and at least one bearing element fixed thereto. More specifically, the present disclosure relates to thrust bearing assemblies including a bearing element of a diamond composite material that is operable at high temperatures and has exceptional wear resistance as well as improved mechanical performance. The disclosure further relates to methods of manufacturing the thrust bearing assemblies.

BACKGROUND

In the discussion that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art against the present subject matter.

Bearings are used in a multitude of applications to facilitate relative motion between two surfaces to reduce energy loss associated with forces, including, e.g., friction while supporting load stresses. For example, in downhole drilling, holes in the earth may be drilled by rotating a drill pipe at the ground surface with a rock bit on the lower end of the pipe for drilling the earth. In such rotary drilling, the entire drill string rotates. However, for deep drilling or drilling through difficult materials, a hydraulic motor may be placed down a bore hole with a rock bit connected to the motor. Drilling fluid, commonly referred to as mud, is pumped down a pipe connected to the motor. The drilling fluid drives the motor which rotates the rock bit. The mud returns to the ground surface through the annulus surrounding the pipe in the bore hole. In such an arrangement it is not necessary to rotate the entire drill string. However, substantial thrust loads are created in this type of drilling.

Accordingly, between the motor and the bit for drilling there is a bearing assembly. Such an assembly has a fixed casing which is threaded to the casing for the motor and a shaft which is connected to the motor shaft. The bearing assembly may include, e.g., radial journal bearings between the shaft and housing and thrust bearings for carrying the substantial thrust loads involved in this mode of drilling.

High pressure drilling fluid is applied through the pipe to the motor while the bit is off of the bottom of the hole. This generates a high thrust load tending to push the shaft downhole. This is referred to as an off bottom load. After the bit is rotating, the assembly is lowered so that the bit is in engagement with the bottom of the hole with sufficient pressure to effect drilling. This reverses the direction of thrust in the bearing assembly and is referred to as the on-bottom thrust. Several such thrust reversals can be encountered as drilling is stopped and started each time a length of drill pipe is added to the string or for other reasons. The thrust bearings are subjected to high loads, vibration, and in some cases rather high rotational speeds. Speeds in a positive displacement motor can be in the range of 125 to 500 RPM, or greater. Turbo drill speeds can be four times larger and are typically 1000 RPM, or greater. Thus, the bearing assembly must last hundreds of hours so as to outlast the rock bit.

The off-bottom load to be carried by the thrust bearings can be as much as 30,000 pounds when a positive displacement motor is used. Off-bottom thrust can be as much as 40,000 pounds with rotational speeds as high as 2000 RPM with a turbine motor, although such conditions are preferably avoided. The on-bottom thrust loads at low to intermediate speeds (e. g., 125 to 400 RPM) range from 10,000 to 40,000 pounds. At high speeds (e.g., 1000 RPM) thrust loads can range up to 20,000 pounds or more.

Thrust bearings using balls operating in thrust carrying races have been used for the thrust bearings between a downhole drill motor and a rock bit. A substantial problem with ball bearing type thrust bearings is the ability to sustain high drilling loads for long enough periods of time. The ball bearing thrust bearings presently available are not suitable for carrying thrust of more than 9072 kg on a sustained basis, particularly at high speeds. When the assembly must carry very high thrust loads in either of two directions, a rather large number of separate ball bearing stages must be used so that no individual stage is excessively loaded. This results in a bearing assembly that is extraordinarily long. The assembly may need to be sealed to retain lubricant for the bearings and seals are difficult in the downhole conditions. Such assemblies are also costly to manufacture, assemble and adjust to the required precision.

A common thrust bearing assembly for a downhole drill is described in U.S. Pat. No. 4,560,014, incorporated herein by reference in its entirety. The thrust bearing described therein includes a bearing surface formed by a plurality of tungsten carbide inserts in a substrate. The cemented tungsten carbide inserts, which include cobalt as a catalyst and have a polycrystalline diamond face, are arranged so the diamond faces collectively form a planar thrust bearing face. However, when operating such a thrust bearing under standard conditions, the polycrystalline diamond faces quickly break down due to high temperatures generated by the speed of the motor. The degradation of the PCD faces is amplified when an abrasive slurry passes near or between the bearing surfaces.

The PCD bearing elements, such as those utilized in U.S. Pat. No. 4,560,014, are commonly used today in demanding applications. However, the use PCD bearing elements can limit the operating conditions in terms of speed and applied load. As the operating velocity or applied pressure is increased, the bearing surface temperatures rise rapidly which in turn degrade the PCD resulting accelerated wear. Therefore, PCD bearing are used at less than optimal operating conditions (lower speeds and lower loads).

Thus, it would be advantageous to have a thrust bearing assembly, or radial bearing assembly, in which the bearing element is formed from a material that is operable at high temperatures and has exceptional wear resistance and improved mechanical performance.

SUMMARY

The present disclosure is directed to bearing assemblies, in particular for thrust or radial bearings, that include a surface formed from a thermally stable diamond material. The thermally stable diamond material may be a diamond material that does not include cobalt, such as a sintered PCD body free from cobalt, or a sintered diamond-ceramic composite material, or other inherently thermally stable PDC cutter material. The thermally stable material allows for operating the bearing assembly at significant higher operating conditions than is possible today. The thermally stable diamond material may be attached to the bearing substrate by utilizing a high temperature epoxy or brazing, which in concert with thermally stable diamond material, protects the integrity of the joint formed between the thermally stable diamond material and substrate material. Additional features and advantages will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the subject matter. The objectives and other advantages of the disclosure will be realized and attained by the structures, particularly pointed out in the written description and claims thereof, as well as the appended drawings.

Provided is a bearing assembly. The bearing assembly may be a sliding or roller bearing assembly, including, for example, a thrust bearing assembly, a radial bearing assembly, a ball bearing assembly, a roller bearing assembly, a tapered bearing assembly, or the like.

The bearing assembly includes at least one substrate assembly. As used herein, the term “bearing assembly” may refer to one or more substrate assemblies either alone or in communication with another. The at least one substrate assembly may include a substrate and at least one bearing element joined at a surface thereof. When attached to a substrate, the bearing elements have an exposed outwardly facing bearing element face which is configured to be in sliding communication with a face of one or more opposing bearing elements joined to an opposing substrate assembly. The opposing substrate assembly may have the same or substantially same structure as the first provided at least one substrate assembly.

In such an arrangement, the first substrate assembly may include a first substrate with one or more bearing element attached to a surface thereof. A second substrate assembly with an identical, or substantially similar structure may also be provided. When assembled, the first substrate assembly is placed in sliding communication with the second substrate at the faces of the bearing elements.

In some instances, the bearing assembly may include more than two substrate assemblies. For example, a bearing assembly may be provided with three substrate assemblies. The bearing assembly may comprise or consist of an upper substrate assembly, a lower substrate assembly, and at least one intermediate substrate therebetween. The upper and lower substrate assemblies may each include at least one bearing element joined to a surface thereof while the intermediate substrate assembly may include at least one bearing element joined to each of opposing surfaces of the intermediate substrate. When assembled, the bearing elements are in sliding communication with one another at the respective faces of the substrate assemblies.

The bearing elements may comprise or consist of a thermally stable material. For example, the thermally stable material may be a ceramic-bonded diamond composite material, a leached PCD material, a PCD material free of, or substantially free of, cobalt, or other thermally stable material.

One ceramic-bonded diamond composite material that may be used is VERSIMAX® produced by Hyperion Materials and Technologies. VERSIMAX® includes, by weight, about 90% diamond grains, about 9% silicon carbide bonded to the diamond grains and about 1% unreacted silicon metal. VERSIMAX® is thermally stable at temperatures of up to 1400° C. Other thermally stable ceramic-bonded diamond composite materials may also be used for the bearing element material. For example, a thermally stable material may comprise or consist of, by weight, about 50 to about 96% diamond grains, about 3 to about 49% silicon carbide, and about 0.1 to about 10% unreacted silicon metal. The ceramic-bonded diamond material may also comprise or consist of, by weight, about 50-99% diamond grains, 1-25% silicon carbide bonded to the diamond grains and 0.01-5% unreacted silicon metal.

In the case of a leached PCD material, any PCD material that has been subject to a leaching process in order to remove cobalt may be used. The leached cutter may be leached at the cutting surface or on the sides of the cutter. Previously used or recycled PCD cutters may also be used, provided that the cutters are free from, or substantially free from, cobalt at the surface.

The substrate may comprise or consist of one or more substrate material. For example, the substrate may be an Fe based alloy, such as a steel. The substrate may comprise or consist of a carbide material such as a cemented carbide. Cemented carbides are metal-matrix composites comprising carbides of one or more of the transition metals belonging to groups IVB, VB, and VIB of the periodic table (Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W) as the hard particles or dispersed phase, and cobalt, nickel, or iron (or alloys of these metals) as the binder or continuous phase. Among the different possible hard particle-binder combinations, cemented carbides based on tungsten carbide (WC) as the hard particle, and cobalt as the binder phase, are often used. However, any cemented carbide may be utilized, including, e.g., those based on titanium carbide (TiC), tantalum carbide (TaC), chromium carbide (CrC) or niobium carbide (NbC).

The substrate as provided herein may also include two or more materials joined together. For example, the substrate may include a first portion formed from a first material, e.g., steel, and a second portion formed of a second material, e.g., a cemented carbide.

The bearing element may be joined to the substrate by any known process or material. For example, the bearing element may brazed to the substrate using one or more brazing materials. For example, the when the bearing element is brazed to the substrate the brazing material may be one or more brazing alloy, including active braze alloys, e.g., TICUSIL®, INCUSIL®, or PALNICRO®, all which are available from Wesgo Metals. However, any suitable brazing material may be utilized.

An epoxy or other adhesive formulation may also be used to join bearing elements to the substrate. As used herein, the term “epoxy” or “epoxy adhesive” means a composition, or combination of compositions, that comprises or forms epoxides or polymers of epoxides.

For example, suitable commercially available epoxy adhesive formulations include, e.g., JB WELD® 453u38, OMEGA® OB-700, among others. An example of another adhesive formulation, specifically a glue, is 620 LOCTITE® 4KM32. The epoxy or other adhesive formulation may be applied at room temperature under atmospheric conditions or subjected to a heating. For example, a substrate with one or more bearing element joined with JB WELD® 453u38 may be placed in a furnace at a temperature of 500° C. for a period of 30 minutes. JB WELD® 453u38 is an epoxy adhesive for suitable for temperatures from 0 to 1315° C. that includes, by weight, 40-50% silicic acid (sodium salt), 40-60% steel fines and an epoxy resin. However, any suitable high temperature epoxy or adhesive composition may be used.

The present disclosure also includes methods of manufacturing a bearing assembly, including a thrust bearing assembly, a radial bearing assembly or the like. The method may include providing one or more substrate assemblies. The substrate assemblies may include a substrate and a bearing element. The substrate may be any material or more than one material, including steel, a cemented carbide or other ceramic materials, and the like. The bearing element can be formed from any known thermally stable material. For example, the thermally stable material may be a ceramic-bonded diamond composite material, a leached PCD material, a PCD material free of, or substantially free of, cobalt, or other thermally stable material. The method may further comprise joining one or more bearing elements to the substrate at one or more surfaces thereof by known techniques including, e.g., brazing, epoxy, other adhesive formulations, a friction fit, a screw fit, or other methods.

Throughout the drawings and the detailed description, unless otherwise described, the same drawing reference numerals should be understood to refer to the same elements, features, and structures. The relative size and depiction of these elements may be exaggerated for clarity, illustration, and convenience. Also, for ease of viewing, in some instances only some of the named features in the figures are labeled with reference numerals.

DETAILED DESCRIPTION

Turning to the drawing figures,FIG.1Ashows a perspective view of a partially assembled substrate assembly101for a thrust bearing assembly according to the present subject matter. As shown, the substrate assembly101includes a substrate103. While the substrate101is shown as having an annular or substantially annular shape, the substrate101may be formed in any shape suitable for a specific use. Also shown are a plurality of bearing elements105. The bearing elements105are joined to the substrate103at the substrate surface107. The substrate assembly shown inFIG.1Aincludes bearing elements attached to one surface of the substrate103. However, one or more bearing elements105may also be joined to the opposing surface (not shown) of the substrate103. As shown, the substrate face107includes a plurality of recesses109shaped to accommodate the bearing elements105. Though not shown, the substrate face107may not include recesses109. In this regard, the substrate face may be substantially planar, planar or include formations the extend outward from the substrate face107. In such assemblies, the bearing elements105may be directly to the substrate or via on to which the bearing elements105. Alternatively, an intermediate structure (not shown) may be used to join the bearing elements105to the substrate103. The intermediate structure may be the same or a different material as the substrate103and/or the bearing elements105. An epoxy, adhesive formulation or braze may be utilized to join the bearing element105to the substrate103either directly or indirectly by joining the bearing element105to a surface of the intermediate structure and joining the opposing surface of the intermediate structure to the substrate surface107.

As shown inFIG.1A, the bearing elements105are formed or cut into a shape such as a cylinder. The bearing elements105may be cut from a larger piece of material, i.e., a blank, via any known method. One method for cutting the bearing elements is electrical discharge machining (EDM) in which a desired shape is obtained by using electrical discharges (sparks). Another possible method of forming the bearing elements105is by grinding or machining the bearing elements105from a rough or recycled material. Suitable bearing element shapes according to the present subject matter include, e.g., two or three dimensional forms of: a circle, a square, a rectangle, a triangle, a trapezoid, a nonagon, a octagon, a heptagon, a hexagon, a scalene triangle, a right triangle, a parallelogram, a rhombus, a square, a pentagon, a circle, an oval, a star and a crescent, or the like.

The bearing assembly may include a fluid restriction element (not shown) to increase the turbulence of, e.g., drilling fluid flow between the bearing elements105. The fluid restriction element is designed to increase the Reynold's number of the fluid flowing between the bearing elements105, thereby increasing the eddy currents and cavitation within the fluid, and as a result, increasing convective heat transfer.

For example, with specific regard to thrust bearing assemblies and radial bearing assemblies used in down hole drilling, drilling fluid acts as both a lubricant to the substrate assembly contact area (i.e., the face111of the bearing elements105), and as a source of heat transfer, pulling heat away from the bearing elements105. Increased turbulence in this flow will greatly improve the heat transfer from the bearing elements105to the drilling fluid (not shown).

In the field of fluid dynamics, the Nusselt number is the ratio of convective heat transfer to conductive heat transfer at the boundary of a system. In the present example, at the boundary between the bearing element105and the drilling fluid, a laminar flow results in a mostly conductive heat transfer, and the resulting Nusselt number is in the range of one to ten. When a baffle or other fluid restriction element is utilized in the substrate assembly, increased turbulence in the flow employs much more convective heat transfer, and the resulting Nusselt number is in the range of 100-1000.

While not limiting to the aforementioned representations, the fluid restriction element can be in the form of a baffle on the bearing element105, a concave depression or a convex protrusion on the substrate surface107, or the like. The size, placement, and number of fluid restriction element will determine the extent of the turbulence induced.

By way of example, the bearing elements105may further include one or more baffle to affect the flow of fluid between the bearing elements. The baffle may be a depression or void formed on the exterior of the bearing element105, or a protrusion extending outward from a surface of the bearing element. The baffle may be on the side109of the bearing element so the outwardly exposed bearing element face111is smooth and without obstruction.

FIG.1Bshows a substrate assembly in which all of the bearing elements105have been joined to the substrate103at the substrate surface107.

Turning toFIG.2A, shown is a partially assembled substrate assembly201for a thrust bearing assembly in which one of the plurality of thrust bearing elements203is not attached to the substrate205. As shown, the substrate assembly201includes two rows of concentrically placed bearing elements203. The bearing elements are oblong shaped and placed in a manner to control fluid flow therebetween when in operation.

FIG.2Bis a representation of the substrate assembly201shown inFIG.2Ain which all of the bearing elements203have been joined to the substrate205at a substrate surface207. The substrate bearing elements303shown are a trapezoidal in shape. However, any one or more shape may be selected based on desired properties.

FIG.3Bshows another substrate assembly according to the present subject matter.

As shown inFIG.4A, a substrate assembly401for a thrust bearing may include one or more bearing elements403, an intermediate substrate405and a substrate407. As discussed herein above, when an intermediate substrate405is employed, it may be the same or different material as the bearing element403and the substrate405. For example, the substrate407may comprise a steel material, the intermediate substrate405may comprise a cemented carbide material, and the bearing element may comprise a thermally stable material. The intermediate substrate405extends the life the bearing assembly by reducing any secondary erosion of the substrate due to material wash. As shown, the intermediate substrate is a carbide receptacle in the shape of a cup. However, the intermediate substrate405can be any shape suitable to join the bearing element403with the substrate407.

FIG.4Bshows of the substrate assembly401shown inFIG.4Ain which all of the bearing elements403have been joined to the substrate405via the intermediate structures405at the substrate surface409.

FIG.5Ashows another substrate assembly501for a thrust bearing. The substrate503comprises a first substrate body, i.e., a surface substrate505and a second substrate body, i.e., a base substrate507. The surface substrate and base substrate can both be formed from any material that is suitable for the present substrates. They may be formed from the same or different materials. For example, the base substrate507may comprise steel and the surface substrate505may comprise a cemented carbide. Generally, the surface substrate is formed from an erosion resistant material. Bearing elements509may be joined to the surface substrate505directly or via an intermediate substrate. The surface substrate may be joined to the base substrate by any known method, including brazing, epoxy or other adhesive formulation. Another surface substrate505may be provided on the opposing surface of the base substrate with or without additional bearing elements509attached thereto.

FIG.6Ashows a first, outer substrate601for a radial bearing assembly according to the present subject matter. As shown, a substrate603is provided with a plurality of bearing elements605joined proximate an upper surface607thereof. The substrate includes inner diameter surface609and outer diameter surface611. The bearing elements605include inner bearing contact surfaces613, which are configured to be in sliding communication with opposing bearing elements (not shown).

FIG.6Bshows an opposing second, inner substrate assembly650which may be placed concentrically inside the first substrate shown inFIG.6B. The inner substrate650includes a plurality of bearing elements653including outer diameter surfaces655that are may be configured to be in sliding contact with the outer diameter surface611shown inFIG.6A. The bearing elements655are joined to the inner substrate657by any suitable method to form the inner substrate assembly650.

In order to achieve preferred bearing assemblies according to the present subject matter, a pneumatic press is utilized to simultaneously seat the bearings into a substrate with an epoxy within 0.0025 cm of the same plane. This allows for the highest proficiency to achieve a solid and uniform hold while simultaneously seating bearings within 0.0025 cm of the same plane, which is preferred to achieve proper bearing load distribution.

An example of a pneumatic press that can be utilized is shown inFIG.7. Shown is a pneumatic arbor press701prepared for specialty alignment tooling. The press shown includes a pneumatic press arbor702, a bottom alignment plate703, and a pneumatic press stage704.

FIG.8shows the pneumatic press ofFIG.7with a substrate assembly801having just applied the epoxy to adhere the bearing elements to the substrate. Not visible inFIG.8is a thin sheet of separator material, e.g. non-stick paper, which is placed on top of the substrate assembly to prevent the excess epoxy from sticking or otherwise adhering to a top alignment plate.

FIG.9shows the pneumatic press ofFIG.8with the top alignment plate901in place for pressing. As noted above a sheet of separator material may be placed between the bearing assembly and the top alignment plate to prevent the excess epoxy from adhering to the top alignment plate.

Thus, provided is a method to manufacture a substrate assembly utilizing a pneumatic press that a solid and uniform hold while simultaneously seating inserts within 0.0025 cm coplanarity. This is a preferred geometry necessary to achieve proper bearing load distribution and functionality.

According to the method, an amount of epoxy is placed in each of the recesses in a substrate. Bearing elements are then placed into the epoxy loaded recesses with little to no force to achieve a wet substrate assembly. As used herein the phrases “wet bearing assembly” or “wet substrate assembly” means a substrate assembly in which the epoxy adhering the bearing elements to the substrate has not yet dried.

The pneumatic press is prepared by first adding a bottom alignment plate to pneumatic press stage, which may be self-centering. The wet substrate assembly is stacked on top of the bottom alignment plate. A special stick resistant separator material, e.g., a sheet of plastic, wax paper, or other non-stick material, is placed on top of the wet substrate assembly to prevent epoxy from adhering to the steel tooling components of the pneumatic press. On top of the separator material, a top alignment plate is placed. The pneumatic press can then be set at a pressure of from 0.2 Megapascal (MPa) to 0.8 MPa. A preferred pressure range is between 0.4 MPa and 0.6 MPa psi. For example, the pneumatic press can be set to a pressure of 70-psi 0.5 MPa.

If the pneumatic press pressure is below 30 psi during bearing seating, multi-plane bearing elements are met with poor parallelism (+0.05 cm out). This also leads to undesirable epoxy thickness compromising holding capabilities leading to bearing failure. Alternatively, when a pressure of greeter than 0.8 MPa is utilized, adverse effects are seen. For example the bearing elements may be chipped or cracked and too much epoxy may be forced out of the recesses in which the bearing elements sit, which leaves behind to thin a layer of epoxy to provide, which leads to bearing assembly failure in use.

Once staged, the pneumatic press is engaged for about 10 seconds, i.e., from 0-10, from 5-15 or from 8-12 seconds, prior to release. This time period ensures all inserts have seated under the same load to achieve the requisite coplanarity. Once released the entire tooling stack is removed from the pneumatic press and set aside for around 24 hours to ensure proper curing.

EXAMPLE

An Instron® push out test was conducted to test the ability to join bearing elements formed from a diamond composite material and stainless steel with epoxy or adhesive compositions. For the test, 9 mm×3 mm VERSIMAX® rounds were encapsulated 1 mm deep into 17-4 PH stainless steel holders that include an aperture to push the thermally stable rounds through. Three different adhesive compositions were used to create two assemblies with each adhesive composition. One of each pair of assemblies was subjected to a high temperature box furnace cycle (500° C. for 30 minutes) to recreate temperatures reflective of those encountered in the field. Once prepared the assemblies were subjected to pressure from a push out tool, i.e., a 0.48 cm steel tip, making contact in the center of the VERSIMAX® round through the aperture in the steel holder. The data collected is presented in table 1 below:

As shown from the push-out test results, all of the adhesive formulations were suitable for joining the VERSIMAX® round to stainless steel at room temperature. However, when subjected to heat, the LOCTITE® formulation was not sufficient to maintain adhesion between the VERSIMAX® round and the steel holder. It is understood that the LOCTITE® formulation was not sufficient because it is a glue rather than an epoxy as described herein.

Although the present subject matter has been described in connection with embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without departure from the spirit and scope of the subject matter as defined in the appended claims. For example, although described in relation to bearing assemblies, the principles, compositions, structures, features, arrangements and processes described herein can also apply to other materials, other compositions, other structures, other features, other arrangements and other processes as well as to their manufacture and to other reactor types.