Abstract:
In a hard facing process, a core material is applied to the base material of an article, which may incorporate metal components. An additive is introduced into a molten puddle generated by the hard facing process. The additive functions to increase the wear resistant capabilities of the hard faced article. In one embodiment, the additive comprises mineral particulates, which may consist of diamond granules.

Description:
[0001]    This utility patent application claims priority to U.S. provisional patent application Ser. 61/103,074 filed on Oct. 6, 2008, entitled Methods and Materials for Hard-Facing, which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention pertains to methods and materials used in hard-facing, and more particularly, to particulates added during the hard-facing process. 
       BACKGROUND OF THE INVENTION 
       [0003]    Metal parts frequently fail their intended use, due not only to fracturing but also to wear and abrasion. Wear changes a metal part dimensionally and as such functionally. Processes are known for repairing worn metal parts where a durable material is adhered to the degraded surface. For metal components, this is commonly known as hard-facing, which can be defined as the application of building up wear-resistant material onto a part&#39;s surface by means of welding or joining. Hard-facing bonds a layer of core metal onto a worn component. In the prior art, wear resistant additives, like tungsten, are included to improve durability. The cost of hard-facing is considerably less expensive than replacement costs and since hard-facing can be applied to a variety of base metals like: steel, stainless steel, nickel-based alloys, and copper-based alloys, it is widely used throughout industry today. 
       BRIEF SUMMARY 
       [0004]    The embodiments of the present invention pertain to a welding process, and more particularly, to a hard-facing application using a source of welding power. During the process, wear resistant particulates are applied to a molten weld puddle. The particulates may be applied by the electrode across the welding arc or via a separate deposition process. The particulates embed in the solidified material forming a wear resistant surface capable of withstanding abrasion. The particulates may be comprised of nonmetallic and substantially elemental substances, like for example carbon atoms formed from an isometric lattice structure, more commonly known as diamond. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a perspective view of a welder hard-facing the surface of a component according to the embodiments of the subject invention. 
           [0006]      FIG. 2  is a close up of the perspective view of a hard-facing application according to the embodiments of the subject invention. 
           [0007]      FIG. 3  is a close up of the perspective view of a hard-facing application according to the embodiments of the subject invention. 
           [0008]      FIG. 4  is a close up, cross sectional view of a hard-facing bead according to the embodiments of the subject invention. 
           [0009]      FIG. 5  is a perspective view of wear resistant particulates according to the embodiments of the subject invention. 
           [0010]      FIG. 6  is a cross sectional view of wear resistant particulates embedded in a substrate according to the embodiments of the subject invention. 
           [0011]      FIG. 7  is a partial cutaway, close up view of an electrode incorporating wear resistant particulates according to the embodiments of the subject invention. 
           [0012]      FIG. 8  is partial cutaway, close up view of another electrode incorporating wear resistant particulates according to the embodiments of the subject invention. 
           [0013]      FIG. 9  is block diagram of a method of welding according to the embodiments of the subject invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    Referring now to the drawings wherein the showings are for purposes of illustrating embodiments of the invention only and not for purposes of limiting the same,  FIG. 1  depicts an end user  15  performing an operation utilizing an arc welder shown generally at  10 . In one embodiment, the end user  15 , or operator, is applying hard-facing material  19  onto a component  21 . Hard-facing may be defined as a process by which core material is adhered to the surface of an existing component. The process bonds or infuses the core material, which may be harder than the component material (also termed base material). In this manner, the core material comprises a wear resistant surface and a barrier to abrasion during use of the component  21 . For metal components  21 , an arc welding process may be used to apply the core material  19 , as will be discussed further below. However, the subject description of arc welding should not be construed as limiting. Rather, other processes and types of equipment may be used, including but not limited to oxyacetylene torches. In this manner, core material  19  is melted along with a surface portion of the metal component  21 . The materials  19 ,  21  coalesce and solidify to create a wear resistant exterior. 
         [0015]    Hard-facing may be applied to wide variety of applications. The metal component  21 , shown in  FIG. 1 , is depicted as generally planar for illustration purposes only. It will be appreciated that the embodiments of the present invention are not limited to the shape and/or size of existing metal component  21 , or type of material comprising the metal component  21 . Examples of such components  21  may include: impeller blades, extrusion screws, and drill bits, just to name a few. Still, the application of the hard-facing may be applied to any component  21 , metal or otherwise, as chosen with sound engineering judgment. 
         [0016]    As mentioned above, the operator  15  may apply the hard-facing material  19  via a manual welding process and may use stick or finite length electrodes  26 . Other methods incorporate more automated processes using continuous-feed electrodes  27 , shown in  FIG. 2 , and programmable equipment like for example articulated robotics. Accordingly, a welding power source  17  may supply electrical power for establishing a welding arc via welding cables  16  and an electrode holder  14  or welding gun  14 . Again, persons of ordinary skill in the art will understand the exemplary nature of the presently described process using an arc welding power source  17 . It will be appreciated that other types of equipment and processes, like brazing, are to be construed as falling within the scope of coverage of the embodiments of the subject invention. 
         [0017]      FIGS. 2 and 3  depict schematic representations of a hard-facing application. In the hard-facing process, an electrode  25  is fed through an electrode holder  14 . As previously mentioned, the electrode  25  is utilized to establish a welding arc capable of melting a surface portion of the component  21  to be hard-faced. The hard-facing process deposits a core material  19  of metal, which makes up a part of the electrode  25 . The core material  19  may include one or more substances, in this embodiment a metal or metal alloy, chosen for its wear resistant properties and/or for its ability to fuse with the base material of the existing component  21 . The core material  19  may be similar in composition to the material comprising the metal component  21  for effective bonding of the materials  19 ,  21 . However, it is noted that any type of core material  19  may be chosen as is appropriate for use with the embodiments of the present invention. Other materials may also be infused during the hard-facing process, which includes additives that contribute to the hardness and/or wear resistance of the hard faced surface, as will be discussed further in a subsequent paragraph. The electrode  25  may further include fluxing agents and other reagents, which aid the hard facing process, and more specifically which reduce the detrimental effects of ambient conditions. It follows that as the operator  15  directs the electrode holder  14  across the component  21 , the electrode  25  is consumed and core material  19  is deposited by the hard-facing process onto the surface of the metal component  21 . 
         [0018]    With reference now to  FIG. 4 , a close up, cross sectional view of a hard facing bead  30  is shown incorporating a plurality of wear resistant particulates  43 . In one embodiment, additives may be deposited in the hard facing bead  30  during the application of the hard facing material  19 , or core material  19 . It will be readily seen that the energy source, e.g. welding arc or torch flame, produces a molten puddle  28  on the surface of the metal component  21 , as depicted in  FIG. 3 . Prior to solidifying, additives may be introduced into the molten puddle  28 . Upon cooling, the additives become permanently embedded into the weld bead  30 . 
         [0019]    With reference again to  FIG. 3 , in one embodiment the additives, comprised of wear resistant particulates  43 , may be introduced into the molten puddle separate from the application of the energy source used to apply the hard-facing material  19 . In other words, wear resistant particulates  43  may be added by a delivery system  46  that is separate from the welding gun  14 , and associated welding power source  17 . The delivery system  46  may incorporate one or more components making up a gravity feed mechanism. A tubular member  47  may be incorporated that directs wear resistant particulates  43  from a feed source, not shown, to a specific point in the molten puddle  28 . The tubular member  47  may be adjustable with respect to its position behind the electrode  25 . It is noted that the tubular member  47 , also termed feed tube, may be positioned at any point spaced apart from the welding arc as is appropriate for allowing the wear resistant particulates  43  to settle into the viscous material of the molten puddle  28 . The tubular member  47  that delivers the wear resistant particulates  43  may also oscillate laterally for evenly distributing the particulates across the hard-faced bead  30 . 
         [0020]    With reference again to  FIG. 2 , another embodiment is contemplated whereby the wear resistant particulates  43  are introduced into the molten puddle  28  simultaneously with the electrode  25 . In this embodiment, wear resistant particulates  43  are transferred through the welding arc along with the hard-facing material  19 . The wear resistant particulates  43  may be incorporated into the electrode  25 . That is to say that the wear resistant particulates  43  may be integrally fashioned with the welding electrode  25  in either a covering applied to the exterior of the electrode core or packed into the hollow core of a tubular electrode. In any manner, flux and/or other reagents may be incorporated along with the wear resistant particulates  43 . Still any manner of introducing wear resistant particulates  43  as transferred across the welding arc may be chosen as is appropriate for use with the embodiments of the subject invention. 
         [0021]    With reference now to  FIG. 5 , the wear resistant particulates  43  may be comprised of a mineral substance. It is contemplated in one embodiment that the mineral substance may be substantially nonmetallic in nature; that is to say comprised mostly of elements that are categorized as nonmetallic. The wear resistant particulates  43  may also be substantially elemental in its construct. Additionally, in its solid phase, the mineral substance may be crystalline in nature. More specifically, the microscopic configuration of the crystalline lattice structure may be configured isometrically, which is to say that the lattice structure is arranged in an array of points repeating periodically in three dimensions. In one embodiment, the wear resistant particulates  43  may be comprised mostly of carbon atoms. In this configuration, carbon is more commonly known as diamond. It is known in the art that diamond substances are not necessarily comprised completely or purely of carbon. Rather other elements may be interspersed into the lattice structure like for example nitrogen, which is known to give diamond substances a yellow hue. All such variations are to be included within the scope of coverage of the embodiments of the subject invention. 
         [0022]    Other embodiments are contemplated wherein the wear resistant particulates  43  are comprised of mineral substances comprising compounds other than or in addition to carbon. Such mineral substances may similarly have a lattice structure that is isometrically configured. One type of mineral is made substantially from Aluminum Oxide commonly called Corundum. Examples of such wear resistant particulates  43  may include sapphires, rubies and the like. In this manner, the mineral substances may be characterized as gemstones and may be substantially homogenous in configuration. Mineral substances such as those described above may include various quantities of foreign particulates, which may be encased by the lattice structure or incorporated into the lattice structure. All such compounds are to be construed as falling within the scope of coverage of the embodiments of the subject invention. 
         [0023]    The wear resistant particulates  43  may be relatively small in diameter ranging in size from approximately 100μ (microns or micrometers) up to and exceeding 800μ (microns or micrometers). More specifically, the wear resistant particulates  43  may be in the range between 400μ (microns or micrometers) to 600μ (microns or micrometers). Still, it is to be construed the wear resistant particulates  43  may be somewhat larger or smaller than the stated ranges. In an exemplary manner, the figures depict generally circular or elliptically shaped particulates. However, the wear resistant particulates  43  may also be elongate or have any shape as is appropriate for use with the embodiments of the subject invention. 
         [0024]    Referencing  FIGS. 5 and 6 , another embodiment is contemplated wherein the wear resistant particulates  43  may be at least partially covered or coated with a veneer  41 . The veneer  41 , or coating  41 , may be comprised of metal or metal alloy. The metal or metal alloy may itself be hard or wear resistant. Additionally, the material comprising the veneer  41  may correspond to the base material  21  and/or the core material  19 . That is to say that the material comprising the metallic veneer  41  may effectively blend together with the base material  21  and/or the core material  19  for firmly holding the wear resistant particulates  43  in place. In one example, the veneer  41  is comprised of tungsten or tungsten carbide. The tungsten, once exposed to the energy source of the hard-facing process, melts forming a tungsten carbide substrate  50  within which the wear resistant particulates  43  become embedded. Other embodiments are contemplated wherein the veneer  41  is comprised of cobalt, chromium and/or alloys formed therefrom. Still, the veneer  41  may be comprised of any metal as is appropriate for use with the embodiments of the subject invention. 
         [0025]    In one embodiment, the type and/or amount of veneer  41  may be selectively adjusted to change the overall density of the wear resistant particulates  43 . In the present example of diamond particulates, it will be understood that the diamonds may be substantially homogeneous having a generally uniform density. As such, the diamond particulates will penetrate only so far into the molten puddle  28  regardless of its girth. To increase penetration into the hard-facing bead  30 , the amount of veneer may be thickened thereby increasing the overall density of the particulate  43  allowing it to sink further into the molten puddle  28 . In one example, the thickness of the veneer  41  may range from just a micrometer up to  50  micrometers. However, any thickness of veneer  41  may be chosen for the desired depth of penetration into the hard-facing bead  30 . It will be appreciated that, in the embodiment utilizing the delivery system  46 , the position of tubular member  47  may also affect the depth of penetration of the wear resistant particulates  43 . In this manner, the end user  15  may selectively adjust the position of the particulates with the hard-facing bead  30 . It is to be realized that different wear resistant particulates  43  may be constructed having different overall veneer thicknesses and hence different densities. When dispersed together, it will be seen that the particulates allow the end-user to populate the hard-facing bead  30  with particles throughout its thickness. Additionally, by adjusting the proportion of lighter and heavier wear resistant particulates  43 , the end-user  15  may distribute the wear resistant particulates  43  in any manner suitable for a specific application. All such proportions are to be construed as falling within the scope of coverage of the embodiments of the subject invention. 
         [0026]    With reference now to  FIGS. 7 and 8 , an electrode  53  is illustrated having a core rod  55 , which may include a solid core wire  55 ′ ( FIG. 7 ) or a hollow core wire  55 ″ ( FIG. 8 ). Other types of core rod material are also to be construed as falling within the scope of coverage of the embodiments of the subject invention including but not limited to composite cores, not shown. In a manner consistent with that described above, the core rod  55  comprises the core material  19  mentioned above as used in the hard facing process. As such, the core material  19  may be constructed from Carbon Steel, Cast Iron, Nickel alloys, Copper alloys and the like. However, the core material  19  may be constructed from any metal or metal alloy as is appropriate for a particular application. It is noted that while the subject embodiments discuss a hard facing application, the electrodes described herein may be applied to any type of welding application, hard-facing or otherwise. 
         [0027]    The core rod  55  may be surrounded by, or respectively filled with, ingredients that function, for example, to provide corrosion resistance, shielding from ambient conditions and purging of impurities from the molten metal. The ingredients may include metals and minerals for alloying and deoxidizing, for stabilizing the welding arc and for forming protective slag, as well as providing shielding from ambient conditions. In this manner, the core rod  55  may be coated, as shown in  FIG. 7 , with a covering  57  made of fluxing elements and other reagents, or alternatively filled with core ingredients  58 , as shown in  FIG. 8 , comprised of similar materials. In one embodiment, the wear resistant particulates  43  may be combined with the covering  57  or core ingredients  58 . Stated another way, the electrode covering  57  or electrode cored ingredients  58  incorporate diamond particulates  44 . It will be readily seen that by integrally fashioning the wear resistant particulates  43  directly into the electrode, the wear resistant particulates  43  may be directly and automatically transferred to the component  21  during application of the hard facing material  19 . 
         [0028]    With reference to  FIG. 9 , an embodiment of the hard-facing process will now be described. An end user  15  may establish a connection between the electrode  25 , a source of welding power and the work piece, which in the present example comprises component  21 . The source of welding power may be an arc welding power source  17  as mentioned above. It is expressly noted that other sources of welding energy may also be used including but not limited an oxyacetylene torch. Once connected, the operator may strike an arc between the electrode  25  and the component  21  causing welding energy to be applied to the weld site thereby melting the base metal of the component  21  and the core metal of the electrode  25  and subsequently forming a coalescence of material, which may be hard-facing material. In one embodiment, a delivery system  46 , separate from the welding equipment, may be incorporated to distribute wear resistant particulates  43  in the initially molten weld puddle  28 . In an alternate embodiment, the electrode  25  may contain the wear resistant particulates  43 , which as will be seen by persons of skill in the art, will be transferred across the arc into the weld bead. 
         [0029]    The invention has been described herein with reference to the disclosed embodiments. Obviously, modifications and alterations will occur to others upon a reading and understanding of this specification. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalence thereof.