Abstract:
A method for manufacturing a metal reinforced open cell carbon foam component comprises (a) placing a block of open cell carbon foam in a mold. The block comprise a plurality of interconnected pores distributed throughout the block. In addition, the method comprises (b) pouring a molten metal into the mold. Further, the method comprises (c) infiltrating the interconnected pores in the block during (b). Still further, the method comprises (d) allowing the molten metal to cool after (c) to form a metal reinforced open cell carbon foam casting.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       BACKGROUND 
       [0003]    1. Field of the Invention 
         [0004]    The invention relates generally to carbon foam metal matrix composite materials. More particularly, the invention relates to drilling mud pumps that employ carbon foam metal matrix composites as reinforcing materials to enhance durability and operating lifetime. 
         [0005]    2. Background of the Technology 
         [0006]    To obtain hydrocarbons such as oil and gas, boreholes are drilled by rotating a drill bit attached to a drillstring. The drill bit is typically mounted on the lower end of the drillstring as part of a bottomhole assembly (BHA) and is rotated by rotating the drillstring at the surface or by actuation of downhole motors or turbines, or by both methods. With weight applied to the drillstring, the rotating drill bit engages the earthen formation and proceeds to form a borehole along a path toward a target zone. 
         [0007]    During drilling operations, drilling fluid, or “mud” as it is also known, is pumped down through the drill string and into the hole through the drill bit. The drilling fluid exits the drill bit through nozzles or jet assemblies positioned in bores formed in the body of the bit. Drilling fluids are used to lubricate the drill bit and keep it cool. The drilling mud also cleans the bit, balances pressure, and carries sludge and formation cuttings created during the drilling process to the surface. 
         [0008]    Pumps, typically referred to as slush or mud pumps, are commonly used for pumping the drilling mud. Such pumps used in these applications are typically reciprocating pumps of the duplex or triplex type. A duplex pump has two reciprocating pistons that each force drilling mud into a discharge line, while a triplex reciprocating pump has three pistons that force drilling mud into a discharge line. These reciprocating mud pumps can be single acting, in which drilling mud is discharged on alternate strokes, or double acting, in which each stroke discharges drilling mud. 
         [0009]    In most mud pumps, a connecting rod extends between each piston and a reciprocating member that drives the movement of the piston within the corresponding cylinder. In some cases, an insert disposed in a mating recess of the reciprocating member pivotally supports the end of the connecting rod coupled to the reciprocating member. The insert also supports axial loads that are transferred between the reciprocating member and the piston via the connecting rod. A lubrication passage is provided in the reciprocating member and the insert to provide lubrication to the interface between the insert and the end of the connecting rod. In such pumps, the connecting rod is often made from hardened steel, the reciprocating member is often made from cast steel, and the insert is often made from bronze. Friction from the sliding engagement of the connecting rod and the insert during pumping operations creates heat that, over time, can detrimentally affect the insert, and hence the connection between the rod and the reciprocating member. For example, the combination of thermal stress and axial loads may induce cracking in the insert, particularly at the lubrication passage of the insert. Such cracks may propagate and increase in size over time, potentially leading to failure of the insert and/or damage to the mud pump. 
         [0010]    Accordingly, there remains a need in the art for improved materials for supporting loads between a connecting rod and a reciprocating member of a mud pump. Such materials would be particularly well-received if they offered the potential to reduce friction and resulting heat between the connecting rod and the insert, and enhance the durability of the connection between the reciprocating member and the connecting rod. 
       BRIEF SUMMARY OF THE DISCLOSURE 
       [0011]    These and other needs in the art are addressed in one embodiment by a method for manufacturing a metal reinforced open cell carbon foam component. In an embodiment, the method comprises (a) placing a block of open cell carbon foam in a mold. The block comprises a plurality of interconnected pores distributed throughout the block. In addition, the method comprises (b) pouring a molten metal into the mold. Further, the method comprises (c) infiltrating the interconnected pores in the block during (b). Still further, the method comprises (d) allowing the molten metal to cool after (c) to form a metal reinforced open cell carbon foam casting. 
         [0012]    These and other needs in the art are addressed in another embodiment by an apparatus. In an embodiment, the apparatus comprises a first component. In addition, the apparatus comprises an insert seated in a recess in the first component. The insert is made of a casting comprising an open cell carbon foam and a metal dispersed throughout a plurality of interconnected pores in the open cell carbon foam. The metal comprises at least one of bronze or steel. Further, the apparatus comprises a second component slidingly engaging the insert. The second component is made of steel. 
         [0013]    These and other needs in the art are addressed in another embodiment by a pump for pumping drilling fluid. In an embodiment, the pump comprises a housing. In addition, the pump comprises a plurality of pumping assemblies disposed within the housing. Each pumping assembly includes a cylinder coupled to the housing, a piston disposed within the cylinder, a reciprocating member, and a connecting rod. The reciprocating member includes a body and an insert seated in a counterbore in the body. The insert includes a semi-spherical recess. The connecting rod has a first end coupled to the piston and a second end comprising a spherical ball slidingly engaging the semi-spherical recess of the insert. The insert is made of a casting comprising a metal reinforced open cell carbon foam. Further, the pump comprises at least one drilling fluid inlet configured to distribute drilling fluid to the pumping assemblies. Still further, the pump comprises at least one drilling fluid outlet configured to supply pressurized drilling fluid from the pumping assemblies. 
         [0014]    Embodiments described herein comprise a combination of features and advantages intended to address various shortcomings associated with certain prior devices, systems, and methods. The foregoing has outlined rather broadly the features and technical advantages of the invention in order that the detailed description of the invention that follows may be better understood. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description, and by referring to the accompanying drawings. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which: 
           [0016]      FIG. 1  is a perspective view of an embodiment of a mud pump in accordance with the principles described herein; 
           [0017]      FIG. 2  is a perspective partial cut-away view of the mud pump of  FIG. 1 ; 
           [0018]      FIG. 3  is a perspective side view of the reciprocating member and the corresponding connecting rod of  FIG. 2 ; 
           [0019]      FIG. 4  is an end view of the reciprocating member and the corresponding connecting rod of  FIG. 2 ; 
           [0020]      FIG. 5  is a perspective view of the connecting rod of  FIG. 2 ; 
           [0021]      FIG. 6  is a cross-sectional view of the reciprocating member of  FIG. 2 ; 
           [0022]      FIG. 7  is a perspective bottom view of the insert of  FIG. 2 ; 
           [0023]      FIG. 8  is a cross-sectional view of the insert of  FIG. 2 ; 
           [0024]      FIG. 9  is an enlarged perspective view of an open cell carbon foam material used to make the insert of  FIGS. 7 and 8 ; and 
           [0025]      FIG. 10  is a schematic illustration of a system for forming the insert of  FIGS. 7 and 8  using the open cell carbon foam material of  FIG. 9  in a casting process. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    The following discussion is directed to various exemplary embodiments. However, one skilled in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment. 
         [0027]    Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness. 
         [0028]    In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . . ” Also, the terms “couple” or “couples” are intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices, components, and connections. In addition, as used herein, the terms “axial” and “axially” generally mean along or parallel to a central axis (e.g., central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to the central axis. For instance, an axial distance refers to a distance measured along or parallel to the central axis, and a radial distance means a distance measured perpendicular to the central axis. 
         [0029]    Referring now to  FIGS. 1 and 2 , an embodiment of a mud pump  100  for pumping drilling fluid during drilling operations is shown. In this embodiment, mud pump  100  has a central axis  105  and includes an outer body or housing  110  and a plurality of circumferentially-spaced pumping units or assemblies  120  disposed within housing  110 . In particular, mud pump  100  includes six pumping assemblies  120 , and thus, may also be referred to as a “hex” pump. In addition, mud pump  100  includes a drilling fluid inlet  101 , a drilling fluid outlet  102  and an annular drive ring  103  that actuates pumping assemblies  120 . Inlet  101  receives drilling fluid that has returned from the borehole and “cleaned” to remove contaminants and formation cuttings. The cleaned drilling fluid flows through inlet  101  and is distributed to pumping assemblies  120 , which pressurize and pump the drilling fluid through outlet  102  into the drillstring. 
         [0030]    Referring now to  FIG. 2 , each pumping assembly  120  has a central axis  125  oriented parallel to and radially spaced from axis  105 . In this embodiment, each pumping assembly  120  includes a cylinder  121  mounted to housing  110 , a piston  122  disposed within cylinder  121 , a reciprocating member or coupling  130 , and a connecting rod  140  extending axially between reciprocating member  130  and piston  122 . An annular wheel or roller  126  is rotatably coupled to each reciprocating member  130 . Each reciprocating member  130  is slidably mounted to an elongate, vertically oriented guide rail  104 , which restricts the corresponding member  130  to axially up and down movement. In addition, each member  130  is biased upward to maintain the corresponding roller  126  in engagement with drive ring  103 . 
         [0031]    To operate pumping assemblies  120 , drive ring  103  is rotated about axis  105  by a motor that rotates a pinion  107  intermeshing with an annular toothed ring  108  coupled to drive ring  103 . Drive ring  103  has an axially undulating lower surface  106  that engages rollers  126 . Thus, as drive ring  103  rotates about axis  105 , lower surface  106  pushes rollers  126  and reciprocating members  130  axially downward and then allows rollers  126  and reciprocating members  130  to be biased back upward, thereby axially reciprocating rollers  126  and members  130  in a sequential manner. The axial reciprocation of rollers  126  and members  130  is translated to pistons  122  via connecting rods  140 . 
         [0032]    Referring now to  FIGS. 3-5 , reciprocating member  130  and connecting rod  140  of one pumping assembly  120  will now be described it being understood that each pumping assembly  120  is configured the same. In this embodiment, connecting rod  140  is pivotally coupled to member  130  with a ball-and-socket joint  150 . In particular, connecting rod  140  is coaxially aligned with axis  125  and has an upper end  140   a  comprising a spherical ball  151  and an annular recess  142  axially adjacent ball  151 . Ball  151  is seated in and slidingly engaging a mating spherical socket  152  formed in reciprocating member  130  to form joint  150 . 
         [0033]    Moving now to  FIGS. 3 ,  4 , and  6 , in this embodiment, reciprocating member  130  comprises a generally u-shaped body  131 , an insert  160  coupled to body  131 , and a retention member  170  coupled to body  131 . Body  131  includes a horizontal lower plate or base  132  defining a lower end  131   a  of body  131 , a first vertical plate  133  extending perpendicularly upward from a first side  132   a  of base  132 , and a second vertical plate  134  oriented parallel to first plate  133  and extending perpendicularly upward from a second side  132   b  of base  132 . When reciprocating member  130  is disposed in pump  100 , plate  133  is slidingly coupled to guide rail  104  and is radially inward of plate  134  relative to axis  105 . Roller  126  is positioned between plates  133 ,  134  and rotates relative to body  131  about an axis oriented perpendicular to plates  133 ,  134 . 
         [0034]    As best shown in  FIGS. 4 and 6 , base  132  includes a cylindrical counterbore or recess  135  extending axially upward from lower end  131   a . In addition, in this embodiment, a lubrication port or bore  136  extends axially through base  132  from its upper surface to recess  135 . 
         [0035]    Referring now to  FIGS. 4 ,  7 , and  8 , insert  160  is seated in recess  135  and is coaxially aligned with axis  125 . In this embodiment, insert  160  is a cylindrical member having a planar first or upper end  160   a  and a planar second or lower end  160   b  opposite end  160   a . Lower end  160   b  includes a semi-spherical recess  161  that slidingly engages ball  151  and defines a portion of socket  152 . Thus, ball  151  may more generally be described as a first component, and insert may be more generally described as a second component, wherein the first component slidingly engages the second component. In addition, insert  160  includes a lubrication port or bore  162  extending axially from upper end  160   a  to recess  161 . As best shown in  FIG. 4 , when insert  160  is disposed in mating recess  135 , bores  136 ,  162  are aligned and in fluid communication and lower end  160   b  is generally flush with lower end  131   a . In this embodiment, bores  136 ,  162  define a flow passage for delivering lubricant to joint  150 . However, in other embodiments, bores  136 ,  162  are eliminated and lubricant is not provided to joint  150 . 
         [0036]    Referring again to  FIGS. 3 and 4 , retention member  170  is mounted to lower end  131   a  of body  131 , coaxially aligned with axis  125 , and disposed about connecting rod  140 . Retention member  170  is an annular member having a first or upper end  170   a  and a second or lower end  170   b . Upper end  170   a  includes a semi-spherical recess  171  that slidingly engages ball  151  and defines a portion of socket  152 . In addition, member  170  includes a through bore  172  extending axially from lower end  170   b  to recess  171 . 
         [0037]    As best shown in  FIG. 3 , together, semi-spherical recesses  161 ,  171  define spherical socket  152 . With ball  151  seated in socket  152 , connecting rod  140  extends downward through bore  172 . Annular recess  142  is sized and positioned to allow connecting rod  140  to pivot to a limited extent about ball  151  before rod  140  impinges member  170 . 
         [0038]    As previously described, in some conventional mud pumps, the insert disposed between the reciprocating member and the connecting rod is made of bronze, which is susceptible to cracking resulting from the combination of thermal stress and compressive loads. However, to enhance the durability and operating lifetime of joints  150 , and hence pump  100 , in embodiments described herein, each insert  160  is made of a carbon-metal composite, and more specifically, a metal-reinforced carbon foam. Such a material offers the potential for reduced friction, and hence reduced friction induced thermal stress, upon sliding engagement with a ball  151  made of steel such as 17-4PH stainless steel. 
         [0039]    The metal-reinforced carbon foam comprises an open cell carbon foam substrate that is infiltrated and saturated with a metal matrix. In general, an open cell foam (e.g., open cell carbon foam) comprises a plurality of bubble structures, each generally defined by about fourteen reticulated windows or facets. The polygonal opening through each open window is referred to as a “pore”. In any given bubble, the polygonal pores actually are of two or three different characteristic sizes and shapes, but for material designation purposes, they are simplified to an average size and circular shape. The number of these pores that would subtend one inch then designates the foam “pore size” defined in terms of pores per inch (PPI). 
         [0040]      FIG. 9  illustrates a representative block  200  of the open cell carbon foam material prior to infiltration with a metal matrix. The open cell carbon foam includes a plurality of interconnected cells or pores  201  defined by and disposed between a network of interconnected struts  202 . Pores  201  are dispersed throughout the entire volume of block  200 . The interconnected open pores or cells  201  the carbon foam allows fluids, such as molten metal, to pass freely through the structure. The density of pores  201  in block  200  can be varied as desired, but preferably ranges from 5 to 100 pores per inch (PPI), and more preferably ranges from 10 to 50 PPI. A commercially available open cell carbon foam that can be used to form embodiments of insert  160  described herein is Duocel® Carbon Foam available from ERG Materials and Aerospace Corporation. In general, Duocel® Carbon Foams can be manufactured with any desired pore density within the range of 5 to 100 PPI. The average pore diameter is about 50% to 70% the diameter of its parent bubble, and thus, a 10 PPI foam would have roughly 5 to 7 bubbles per inch. 
         [0041]    Referring now to  FIG. 10 , as previously described, the metal-reinforced carbon foam that forms embodiments of insert  160  comprises an open cell carbon foam substrate that is infiltrated and saturated with a metal matrix. To manufacture insert  160 , block  200  of open cell carbon foam material is placed inside a mold  300 . Block  200  can be placed in the center of mold  300  or offset from the center of mold  300 . In general, block  200  can be fabricated and pre-formed in any shape and size suitable for the casting process, and is preferably fabricated and pre-formed with a shape and size that simplifies and/or eliminates subsequent machining steps necessary to produce the desired geometry for insert  160 . For example, block  200  can be pre-formed or fabricated in the form of a cylinder, handlebar, cube, rectangle, disk, ring, or other geometry before being placed inside mold  300 . 
         [0042]    Next, molten metal  301  is poured into mold  300  around block  200  of open cell carbon foam material. In general, the molten metal  301  can be any metal or metal alloy that provides the desired material properties in the anticipated application. To form insert  160  for use in mud pump  100 , molten metal  301  is preferably 17-4PH stainless steel, 15-5PH stainless steel, 300 or 400-series stainless steel, bronze, or other metal or metal alloy capable of being cast and machined. Prior to pouring, the mold  300  and the block  200  can be pre-heated. The mold  300  can be pre-heated prior to the block  200  placement inside the mold, or can be pre-heated with the block  200  already placed in the mold. Block  200  may be pre-heated prior to placement in a pre-heated mold  300 , or in a non-pre-heated mold  300 . Upon pouring, molten metal  301  penetrates and infiltrates pores  201  throughout the block  200  of open cell carbon foam. In some embodiments, molten metal  301  is poured under vacuum to enhance migration throughout block  200  of open cell carbon foam, particularly in embodiments where pores  201  are relatively small (e.g., 40-50 ppi). Next, molten metal  301  is allowed to cool, thereby forming one solid machinable casting comprising a metal reinforced open cell carbon foam. After cooling, the finished casting can be cut and/or machined to form insert  160  of the desired size and shape. In addition, the finished casting may be heat treated as desired. 
         [0043]    As previously described, in some conventional mud pumps, the insert disposed between the reciprocating member and the connecting rod is made of bronze, which is susceptible to cracking resulting from the combination of thermal stress and compressive loads. Thermal stress is typically induced by friction arising between the bronze insert and the connecting rod. However, in embodiments described herein, insert  160  made of metal reinforced open cell carbon foam provides a lower coefficient of friction (static and kinetic) than a bronze insert in connection with a connecting rod made of a given material (e.g., steel). In particular, the carbon of the open cell carbon foam functions similar to lubrication between insert  160  and ball  151  of connecting rod  130 . Accordingly, embodiments described herein offer the potential for reduced friction and associated thermal stress as compared to conventional bronze inserts, thereby decreasing the potential for thermal stress induced thermal cracking. 
         [0044]    While preferred embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of the invention. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. Unless expressly stated otherwise, the steps in a method claim may be performed in any order. The recitation of identifiers such as (a), (b), (c) or (1), (2), (3) before steps in a method claim are not intended to and do not specify a particular order to the steps, but rather are used to simplify subsequent reference to such steps.