Abstract:
A method of repairing a defect in a casting or cast article, where the defect comprises at least one of a manufacturing, intentional, or service-related defect. The cast article can comprise a casting core and a casting, the casting core comprising a bumper that creates a thin region, namely the defect. One method of repairing the bumper hole defect comprises locating the defect area in the cast article; removing an area of the casting at the defect area; removing an area of the casting core including the bumper at the defect area, where the removing the area of the casting at the defect area and removing an area of the casting core including the bumper at the defect area create a hole; positioning repair material in the hole; heating the defect area, the repair material and the area of the casting at the defect area to melt the repair material and area of the casting at the defect area into a molten material; and re-solidifying the molten material to form a repaired casting. Also, the method without forming the hole can be applied to repair surface defects. The invention also is directed to the repaired article formed by the methods.

Description:
FIELD OF INVENTION  
         [0001]    The invention relates to a process for the repair of defects in castings. In particular, this relates to a process for the repair of defects in engine and airfoil components and parts.  
         BACKGROUND OF THE INVENTION  
         [0002]    Modern gas turbine engines and their respective components, operate at high rotational speeds and high temperatures for increased performance and efficiency. Thus, the materials from which these components are made must be able to withstand severe operating environments.  
           [0003]    Most high temperature gas turbine components are made of nickel base superalloys, which are alloys that are specifically developed for applications involving extreme temperatures and mechanical stresses. Superalloys are often cast, by an appropriate process, into the component shape. For example, directional solidification is known in the art. This casting technique aligns grain boundaries parallel to the stress axis. This alignment enhances elevated temperature strength by increasing resistance to creep and minimizing grain boundary failure initiation sites.  
           [0004]    An extension of the above-described technique is single crystal casting. Casting of alloys in single crystal form eliminates internal crystal boundaries in the finished article. Single crystal turbine blades and vanes possess superior characteristics, such as strength, ductility and crack resistance at high operating temperatures. Thus, single crystal articles are extensively used in components of gas turbine engines.  
           [0005]    Although single crystal engine components are desirable, they are extremely costly to manufacture. Defects often occur during manufacturing, as well as after extensive engine operation. Upon detection of certain critical defects, such as cracks, the component must be repaired, replaced or otherwise scrapped. This incurs a significant expense and is undesirable.  
           [0006]    The fabrication of gas turbine components, for example blades or nozzles, can occur by various processes, such as by investment casting. In investment casting of relatively complex airfoil parts, intentional defects, such as “bumper holes,” may be required for casting the part, as is known in the art. The bumper holes constitute an “intentional” defect used to hold the casting core during casting of relatively complex articles.  
           [0007]    Ceramic bumpers are added to the ceramic core to limit the maximum distortion or motion of the core relative to the mold, to achieve a control of wall thickness in a cavity. The bumper holds the casting core in place during casting. After the core is removed, a thin spot remains where a bumper was located. This thin region is removed forming a “bumper hole” that can then be repaired to achieve the full required wall thickness.  
           [0008]    The bumper holes should be repaired when the casting is completed and prevent coolant leakage and to make the casting usable. Accordingly, post-processing of the investment casting is needed to remove the bumper holes.  
           [0009]    Several proposed repair methods for cracks in components have been proposed. For example, European patent application EP 0740976 (EP 976) discloses a method of repairing single crystal metallic articles using a laser technique. EP 976 attempts to overcome problems associated with the laser weld repair of these articles by optimizing laser parameters. In particular, EP 976 provides a molten material at the crack, solidifies the molten material, and provides a re-melt of a once solidified melt from a second energy source, in an attempt to provide an acceptable stress-free repair. However, EP 976 does not discuss a repair of as-cast articles. Further, EP 976 does not provide for removal of defects, and does not provide for melting of the casting to insure a sound metallurgical bond and physical repair. Furthermore, the second application of energy in EP 976 is costly and inefficient with respect to both in time and power consumption.  
           [0010]    It is desirable to reduce overall costs involved with casting. This cost reduction includes avoiding scrapping newly cast articles with manufacturing defects. This cost reduction also includes efficiently repairing, rather than scrapping and re-casting, parts with defects resulting from use of the part.  
         SUMMARY DESCRIPTION OF THE INVENTION  
         [0011]    Accordingly, it is desirable to provide a method for repairing defects in airfoils that reduces costs associated with the production of airfoils.  
           [0012]    Further it is desirable to provide a method for repairing defects in airfoil components and parts, which are produced by investment casting processes, that reduces costs associated with the production of said airfoil components.  
           [0013]    It is also desirable to provide a process with means to repair defects, both intentional, such as “bumper hole” defects, or unintentional, such as freckles and inclusions from the casting process or cracks resulting from use, thereby minimizing the need to scrap and recast. A reduction in process costs results in a savings to the manufacturer, and ultimately to the customer.  
           [0014]    Therefore, it is desirable to provide a method of repairing defects in cast articles, where the defect comprises at least one of a manufacturing, intentional, or service-induced defect. The cast article comprises a casting core and a casting, the casting core comprising a ceramic bumper that creates a thin region in the casting comprising the defect. The method of repairing the defect comprises locating a defect at a defect area in the cast article; removing an area of the casting at the defect area; removing an area of the casting core including the bumper at the defect area, where removing the area of the casting at the defect area and removing an area of the casting core including the bumper at the defect area to creates a hole through a wall of the casting; positioning repair material in the hole; heating the defect area, so the repair material and the area of the become molten; and re-solidifying the molten material to form a repaired casting.  
           [0015]    Also, it is desirable to provide a method, similar to that above, but without forming the hole, to repair surface defects, such as voids, freckles and inclusions.  
           [0016]    Further, it is desirable to provide a repaired article formed by the methods, as embodied by the invention.  
           [0017]    These and other aspects, advantages and salient features of the invention will become apparent from the following detailed description, which, when taken in conjunction with the annexed drawings, disclose embodiments of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    While the novel features of this invention are set forth in the following description, the invention will now be described from the following detailed description of the invention taken in conjunction with the drawings, in which:  
         [0019]    [0019]FIG. 1 is a side-sectional view of an intentional defect, for example, a thin region in a casting, for example resulting from a ceramic bumper;  
         [0020]    [0020]FIG. 2 is a side-sectional view of a “bumper hole” made to remove the cast product and thin region in a process, as embodied by the invention;  
         [0021]    [0021]FIG. 3 is a side-sectional view of a repair filler material in the bumper hole of FIG. 2;  
         [0022]    [0022]FIG. 4 is a side-sectional view of molten repair filler material and cast material;  
         [0023]    [0023]FIG. 5 is a flow chart of a process for repairing intentional defects, for example a bumper hole, as embodied by the invention;  
         [0024]    [0024]FIG. 6 is a side-sectional view of a surface defect in a casting;  
         [0025]    [0025]FIG. 7 is a side-sectional view of a surface defect repair filler material in the surface defect of FIG. 6;  
         [0026]    [0026]FIG. 8 is a side-sectional view of a molten surface defect repair filler material and cast material;  
         [0027]    [0027]FIG. 9 is a flow chart of a process for repairing surface defects, as embodied by the invention;  
         [0028]    [0028]FIG. 10 is a side-sectional view of a casting formed using an intentional defect, for example, a bumper hole, with the casting core removed;  
         [0029]    [0029]FIG. 11 is a side-sectional view of a hole in the casting, as embodied by the invention;  
         [0030]    [0030]FIG. 12 is a side-sectional view of a repair filler material in the hole of FIG. 11;  
         [0031]    [0031]FIG. 13 is a side-sectional view of molten repair filler material and casting;  
         [0032]    [0032]FIG. 14 is a flow chart of a process for repairing a casting having an intentional defect, such as a bumper hole, as embodied by the invention;  
         [0033]    [0033]FIG. 15 is a side-sectional view of a defect, for example, a through crack in a casting;  
         [0034]    [0034]FIG. 16 is a side-sectional view of a hole in the casting, as embodied by the invention;  
         [0035]    [0035]FIG. 17 is a side-sectional view of a repair filler material in the hole of FIG. 16;  
         [0036]    [0036]FIG. 18 is a side-sectional view of molten repair filler material and casting;  
         [0037]    [0037]FIG. 19 is a flow chart of a process of FIGS.  15 - 18 , as embodied by the invention;  
         [0038]    [0038]FIG. 20 is a side-sectional view of a defect, for example, a thin region formed by a bumper in a casting;  
         [0039]    [0039]FIG. 21 is a side-sectional view of repair material on the casting, as embodied by the invention;  
         [0040]    [0040]FIG. 22 is a side-sectional view of the repair filler material becoming molten material;  
         [0041]    [0041]FIG. 23 is a side-sectional view of molten repair filler material and casting; and  
         [0042]    [0042]FIG. 24 is a flow chart of a process of FIGS.  20 - 23 , as embodied by the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0043]    Defects resulting from casting processes can take several distinct forms. For example, defects resulting from casting processes may include surface defects. Surface defects resulting from casting processes can include cracks, freckles, or voids which may result during re-solidification of the casting. Also, as described above, intentional defects, such as bumper holes, constitute defects.  
         [0044]    Defects may also result from use of the cast component. For example, these defects can be cracks resulting from field use of the component. These cracks are due, at least in part to a critical combination of thermal and mechanical stresses that the components are subjected to during operation.  
         [0045]    Cracks that result from field use often require cleaning, because the crack surfaces may have been oxidized. Oxidized crack surfaces present an undesirable surface for repair. The oxidized surface is unreliable both mechanically and metallurgically. A mechanically and metallurgically sound repair by bonding a metal in an oxidized crack will be difficult, if not impossible, due to oxides on the crack surface.  
         [0046]    Accordingly, as embodied by the invention, it is desirable and advantageous to provide a method for repair of defects in castings, where the defects result from at least one of casting processes and use. By virtue of the repair process, as embodied by the invention, the casting will be reliably repaired, without the need for the casting to be scrapped. Therefore, as embodied by the invention, methods for repairing defects in cast products provide extended use of casting and avoid scrapping the casting.  
         [0047]    As embodied by the invention, the repair of defects in cast products comprises a method that includes heat treating the defect area, the repair material and the casting itself, with or without repair material. The heat treating is done by an appropriate device and method, for example by at least one of electron beam welding, plate welding and other welding processes.  
         [0048]    A repair method, as embodied by the invention, for the repair of a defect, such as bumper holes, will now be discussed with reference to FIGS.  1 - 4  and the flowchart of FIG. 5. The casting process is, for example but not limited to, an investment casting process. The cast article  1  relies upon at least one bumper  13  for casting due to the complexity of the casting  10 . Because investment casting is known in the art, an explanation of the process is omitted. Thus, the cast article  1  comprises a ceramic casting core  14  used in a casting process and a casting  10 .  
         [0049]    If the casting process uses at least one bumper  13 , the repair method for bumper recess or hole defects comprises first locating the defect  5 , in step S 1 . Location of the defects  5  is done prior to any removal, separation, or reduction of the ceramic casting core  14 . The ceramic core  14  provides a support for filler material  25 , which will be used to repair the defect  5 , as described hereafter.  
         [0050]    Once the defect  5  has been located, a part of a defect area  7  (dashed line in the Figures) of the cast article  1  that surrounds the bumper hole  12  is removed, in step S 2 . Next, a ceramic bumper  13 , which is used in the investment casting process to form the bumper hole  12  is removed, in step S 3 . Preferably, the removal of the ceramic bumper  13  is in the same step that removes the casting  10  at the defect area  7 . Accordingly, the removal of material forms a flat-bottomed hole  20  generally located at the defect area  7 .  
         [0051]    A repair material  25 , alternately referred to as a filler material, is then provided in the flat-bottomed hole  20 , in step S 4 . The repair material  25  is preferably the same material of the casting  10 . Alternatively, the repair material  25  may be a material that is compatible, metallurgically and physically, with the casting  10 .  
         [0052]    The repair material  25  is provided generally in the form of a repair material plug  26 . The repair material plug  26  preferably has a general shape approximately conforming to the shape of the flat-bottomed hole  20 . This conforming shape permits the repair material to substantially fill the entire flat-bottomed hole  20 . Alternatively, the repair material plug  26  need not approximate the shape of the flat-bottomed hole  20 , provided the volume of the repair material plug  26  is greater that the volume of the hole  20 .  
         [0053]    The volume of the repair material plug  26  should be sufficient to completely fill the flat-bottomed hole  20 , and extend above the hole  20  top surface  21 . In other words, the volume of the filler material  25  is greater than the volume of the flat-bottomed hole  20 . This extension of the repair material plug  26  above the hole surface  21  will assure that the repair material plug  26  will completely fill the hole  20  upon melting. Further, as embodied by the invention, cooling stresses that may form during the cooling of the molten material will tend to be distributed in any excess material above the top surface  21  of the flat-bottomed hole  20 . In other words, stresses are formed away from the casting  10 .  
         [0054]    Once the repair material plug  26  has been inserted into the flat-bottomed hole  20 , the defect area  7  is heat treated, with full penetration of the casting thickness t, in step S 5 . For example, the defect area  7  can be heated by an appropriate heating device, such as but not limited to, an electron beam welder. The heat in step S 5  is applied under predetermined conditions to bring at least a portion of surrounding material of the casting  10  and the repair material plug  26  into a molten condition  27  in FIG. 4.  
         [0055]    The heating preferably comprises a gradual heating of the casting  10  and the repair material plug  26 . The predetermined conditions also provide a gradual cooling of the molten material  27 . The gradual heating and gradual cooling minimizes temperature gradients formed during repair. Gradual heating and cooling minimizes temperature gradients formed during repair, thus minimizing stress generation in the defect area  7 .  
         [0056]    The predetermined conditions for heating are dependent upon several factors. These factors, include, but are not necessarily limited to: the material composition of the casting  10 ; the repair material  25  composition; the location of the defect area  7 ; the ambient environment of the cast article  1 , for example vacuum or a partial pressure of inert gaseous environment.  
         [0057]    With the surrounding material of the casting  10  and the repair material plug  26  as molten material  27 , the retained ceramic core  14  supports the molten material  27  until it re-solidifies, at step S 6 . Therefore, the molten material  27  is kept at the defect area  7 .  
         [0058]    Any excess material can be removed further in the repair process, step S 7 , if needed. The excess material remaining on the repaired casting surface can be removed by, for example, at least one of a machining process and a benching process. The core is then removed, by known methods, resulting in a repaired casting.  
         [0059]    After the molten material at  27  has re-solidified in step S 6  and any excess material is removed, as needed in step S 7 , the repaired casting is inspected at the defect area  7  by an appropriate inspection device. The inspection device determines whether the repair process has successfully repaired the defect  5 . If the inspection determines that the repair process has successfully repaired the defect, the manufacturing process continues.  
         [0060]    The cast article  1 , as embodied by the invention, can be in any form, such as one of an as-cast condition and a casting after a first solution heat treatment after initial casting.  
         [0061]    A casting  10  is often prone to cracking during any type of localized heating operations, such as in previously attempted repair processes. To eliminate cracking, as embodied by the invention, a slow, uniform heating and cooling, reduces thermal stresses in the molten material  27 .  
         [0062]    Heating, for example by electron beam welding, as embodied by the invention, provides a slow, uniform heating and cooling to reduce thermal stresses induced to the re-solidified material. Further predetermined parameters for heating by electron beam welding, comprise but are not limited to: 1) electron beam focus factors, such as a suitable raster pattern, for example area, line or spot patterns, a suitable amount of beam dither, and other electron beam focus variables; 2) at least partial, and alternatively, full, weld penetration, controlled by electron beam potential; 3) an appropriate casting material, such as but not limited to, a nickel base superalloy, which provides concomitant heating, holding, and cooling ramp rates; and 4) an appropriate pre-heat temperature for the cast article  1 .  
         [0063]    If the casting  10  comprises directionally solidified and single crystal structures, the above-described repair process creates grain structure in the repaired area  7  that is substantially similar to, and very compatible with, the initial micro-structure of the casting  10 . This is especially advantageous, as it provides a structurally and metallurgically sound and reliable repair.  
         [0064]    Inspection of the repaired part comprises any appropriate inspection device, such as but not limited to, an ultrasonic inspection device, a bright field illumination device, a fluorescent dye penetration inspection device, an x-ray inspection device and combinations of such devices.  
         [0065]    The above described method discusses a repair of bumper holes and other through-wall defects in an investment casting. A process for surface defect repair, including but not limited to voids, surface freckles, inclusions, cracks and freckles, as embodied by the invention, will now be discussed with reference to FIGS.  6 - 8  and the flowchart of FIG. 9.  
         [0066]    The repair of surface defects comprises initially locating the defect  52 , in step S 11 . Once the defect  52  has been located in the casting  54 , a defect repair material  56  may be provided to the defect  52 , in step S 12 .  
         [0067]    The surface defect repair material  56 , if needed, is preferably in the form of a filler wire, elongated strand-like material or other compatibly shaped surface defect repair material. The surface defect repair material  56  is preferably formed of a composition that is the same as the composition of the casting  54 . Alternatively, as discussed above, the surface defect repair material may be formed of a composition that is compatible with, both metallurgically and physically, with the material of the casting  54 .  
         [0068]    The surface defect repair material  56  is provided in a form of a filler wire, elongated strand-like material, or other compatible shape to approximate the shape of the defect  52 . The surface defect repair material  56  conforms to and substantially fills the volume of the surface defect  52 , while having a volume exceeding that of the defect  52 . Alternatively, the surface defect repair material  56  may not have a shape approximating the shape of surface defect  52 , as long as it has a volume greater than the volume of the surface defect. The surface defect repair material  56  can be provided as a cut piece of filler wire, an elongated strand-like material, or as a continuous feed wire, constituting a continuous feed wire repair process for surface defects. Alternatively, no additional repair material may be used.  
         [0069]    To repair a surface defect  52 , the repair material  56  is inserted into the defect  52 , at step S 12 . Next, the defect area is heated at step S 13  by heat treating with an appropriate heating device. As discussed above, the appropriate heating device may comprise, but is not limited to, an electron beam welder. The heat is applied under predetermined heating conditions, as discussed above.  
         [0070]    After the surface defect repair material  56  and the surrounding casting  54  are molten  58 , the molten material  58  is allowed to re-solidify in step S 14 . Any excess material is removed as needed, in step S 15 . Thereafter, the repaired casting  54  is inspected by an appropriate inspection device, as discussed above.  
         [0071]    As embodied by the invention, repair of surface defects, such as freckles and cracks, may not require additional material to fill the defect. The defect may be comprised of a superficial irregularity in the microstructure of the casting, and not necessarily by a lack of material at the defect site. In this case, the surface defect to be repaired, such as a surface freckle is first located. The area of the surface defect is heated to make the surface defect area molten. The molten material is then re-solidified, as described above. Accordingly, a repaired surface defect, that was in the form of a surface freckle, is repaired as embodied by the invention.  
         [0072]    A method for the repair of oxide-laden defects in castings, as embodied by the invention, such as but not limited to oxide-laden cracks, will now be discussed. The steps of the process for the repair of oxide-laden defects are substantially similar to the process of repairing surface defects, discussed above.  
         [0073]    To repair oxide-laden defects, the defect is first located. The repair material is positioned over the oxide-laden defect, and the defect area is heated to cause the repair material and the surrounding cast material to become molten, as described above.  
         [0074]    While molten, oxides are released from the surface of the defect. These oxides rise to the top of the molten material due to their relatively low density. With the oxides removed from the surface of the oxide-laden defect, a sound metallurgical bond and physically strong repair of the defect is achieved. Further details in the repair of oxide-laden defects, as embodied by the invention, are as discussed above, and further discussion is thus omitted.  
         [0075]    A repair method, as embodied by the invention, for the repair of a defect, such as bumper holes, will now be discussed with reference to FIGS.  10 - 13  and the flowchart of FIG. 14. The casting process is, for example but not limited to, an investment casting process. The casting  100  relies upon bumpers, as described above, due to the complexity of the casting  100 . Because investment casting is known in the art, a detailed explanation of the process is omitted.  
         [0076]    In this repair method, as embodied by the invention, the casting core and bumpers are removed prior to any steps of the repair. The casting core can be removed by any known methods relied upon in the art. Accordingly, the casting  100  comprises at least one bumper hole  112  and forms the article to be repaired.  
         [0077]    The repair method for a casting  100  with a bumper hole  112  comprises first locating the defect  105 , in step S 100 . The location of the defect  105  is done after removal, separation, or reduction of the ceramic casting core.  
         [0078]    Once the defect  105  has been located, a part of a defect area  107  (dashed line in the Figures) of the cast article  100  that surrounds the bumper hole  112  is removed, in step S 102 . Accordingly, the removal of material forms a through-hole  120  generally located at the defect area  107 .  
         [0079]    A repair material  125 , alternately referred to as a filler material, is then provided in the through-hole  120 , in step S 104 . The repair material  125  is preferably the same material as the casting  100 . Alternatively, the repair material  125  may be a material that is compatible, metallurgically and physically, with the casting  100 .  
         [0080]    The repair material  125  is provided generally in the form of a plug  126 . The plug  126  preferably has a shape approximately conforming to the through-hole  120 , permiting the repair material to substantially fill the entire hole volume  120 . However, the plug  126  need not approximate the shape of the through-hole  120 , as long as the volume of the plug  126  exceeds the volume of the hole  120 .  
         [0081]    The volume of the repair plug  126  should be sufficient to completely fill the through-hole  120  and extend above and below the hole  120  top  121  and bottom  122  surfaces. In other words, the volume of the filler material  125  is greater than the volume of the through-hole  120 . This extension of the repair plug  126  above the through-hole  120  top surface  121  and bottom surface  122  will assure that the plug  126  will completely fill the through-hole  120  when melted. Any residual stresses that may be formed in the process are believed to be concentrated in the last portion of the molten material to re-solidify, for example in the areas outside of the through-hole  120  above the top surface  121  and below the bottom surface  122 . Thus, any residual stresses that may cause cracks or other such defects can be removed by further machining of the repaired area.  
         [0082]    Once the repair material plug  126  has been inserted into the through-hole  120 , the defect area  107  is heat treated in step S 105 . However, contrary to the full-penetration heating described above, the beam does not fully penetrate the casting thickness, t. This partial-penetration heat treating, for example with an electron beam, prevents the electron beam from harming any material located behind the casting  100 . The heat in step S 105  is applied under predetermined conditions to bring at least a portion of surrounding material of the casting  100  and the repair material plug  126  into a molten condition  127 , as shown in FIG. 13.  
         [0083]    With the surrounding material of the casting  100  and the repair material plug  126  heated to molten material  127 , the molten material is retained in the through-hole  120  by surface tension of the molten material. The principles of surface tension are well known, and a further discussion of surface tension is omitted.  
         [0084]    The surface tension suspends the molten material  127  in the through-hole  120  within the support of the casting  100 . The electron beam used for heating in step S 105  is balanced to achieve melting of the plug  126  and the surrounding casting  100  at the defect area  107 , while not disturbing the surface tension forces that hold the molten material  127  in the through-hole  120 . Further, the electron beam strength is also balanced to maintain the suspension of the molten material  127  and avoid full penetration of the casting  100 .  
         [0085]    The heating preferably comprises a gradual heating of the casting  100  and the repair material plug  126 . The predetermined conditions also provide a gradual cooling of the molten material  127 . The gradual heating and gradual cooling minimizes temperature gradients formed during repair. Thus, the gradual heating and cooling provides for minimized stress generation in the defect area  107 . However, the above described balancing with respect to non-full penetration, surface tension and maintaining a suspension of the molten material  127  in the through-hole  120  must be observed. Other predetermined conditions for heating are as described above. Accordingly, a further description is not provided.  
         [0086]    The molten material  127  then re-solidifies at step S 106 . Any excess material above and below the casting  100  at the area where the through-hole  120  was located, including generated stresses, can be removed further in the repair process, in step S 107 , if needed. Excess material remaining on the repaired casting surface can be removed by, for example, at least one of a machining process and a benching process.  
         [0087]    After the molten material at  127  has re-solidified in step S 106  and any excess material is removed, as needed in step S 107 , the repaired casting is inspected at the defect area  107  by an appropriate inspection device. The inspection device determines whether the repair process has successfully repaired the defect area  107 . If the inspection determines that the repair process has successfully repaired the defect, the manufacturing process continues.  
         [0088]    A further repair process for non-intentional defects, as embodied by the invention, will now be discussed with reference to FIGS.  15 - 18  and the flowchart of FIG. 19. The non-intentional defects comprises defects such as cracks, both surface and through wall cracks, without bumpers.  
         [0089]    The repair process for non-intentional defects comprises defects such as cracks, both surface and through wall cracks, without bumpers comprises first locating the defect  212 , such as a through crack as illustrated, in a casting  210  in step S 110 . Next in step S 120 , an area of the casting  210  at the defect area  207  is removed to form a hole  220 . The hole can be a through-hole extending across the casting  200 , or can be a partial hole that extends only partially through the casting  200 .  
         [0090]    A repair material  225 , alternately referred to as a filler material, is then provided in the through-hole  220 , in step S 130 . The repair material  225  is preferably the same material of the casting  200 . Alternatively, the repair material  225  may be a material that is compatible, metallurgically and physically, with the casting  200 .  
         [0091]    The repair material  225  is provided generally in the form of a repair material plug  226 . The repair material plug  226  preferably has a general shape approximately conforming to the shape of the through-hole  220 . This conforming shape permits the repair material to substantially fill the entire through-hole  220 . Alternatively, the repair material plug  226  need not approximate the shape of the through-hole  220 . All that is needed is the volume of the repair material plug  226  is greater that the volume of the through-hole  220 .  
         [0092]    The volume of the repair material plug  226  should be sufficient to completely fill the through-hole  220 , and extend above the hole  220  top surface  221  and below the bottom surface  222  of the hole  220 . In other words, the volume of the filler material  225  is greater than the volume of the through-hole  220 . This extension above the through-hole  220  top surface  221  and the bottom surface  222  of the repair material plug  226  will assure that the repair material plug  226 , when melted, will completely fill the through-hole  220 .  
         [0093]    Once the repair material plug  226  has been inserted into the through-hole  220 , the defect area  207  is heated by heat treating in step S 140 . However, contrary to the full penetration as described above, the heating is not full penetration of the casting thickness t. This non-full penetration heat treating, for example with an electron beam, prevents the electron beam from hitting and disrupting and harming anything located behind the casting  200 . The heat in step S 140  is applied under predetermined conditions to bring at least a portion of surrounding material of the casting  200  and the repair material plug  226  into a molten condition as molten material  227  in FIG. 18.  
         [0094]    With the surrounding material of the casting  200  and the repair material plug  226  heated to molten material  227 , the molten material is retained in the through-hole  220  by the surface tension of the molten material interacting with the through-hole  220 . The principles of surface tension are well known, and a further discussion of surface tension is omitted.  
         [0095]    The surface tension suspends the molten material  227  in the through-hole  220  within the support of the casting  200 . The electron beam parameters used for heating in step S 140  are optimized to achieve melting of the plug  126  and the surrounding casting  100  at the defect area  207  while maintaining the molten material  227  in the through-hole  220 . Further, the electron beam strength is optimized to maintain the suspension of the molten material  227  and avoid full penetration of the casting  200 .  
         [0096]    The molten material  227  re-solidifies at step S 150 . Any excess material above and below the casting  200  at the area where the through-hole  220  was located can be removed as part of the repair process, step S 160 , if needed. Excess material remaining on the repaired casting surface can be removed by, for example, at least one of a machining process and a benching process.  
         [0097]    After the molten material at  227  has re-solidified in step S 150  and any excess material is removed, as needed, in step S 160 , the defect area  207  of the repaired casting is inspected by an appropriate inspection device to determines whether the repair process successfully repaired the defect  212 . If the inspection determines that the repair process has successfully repaired the defect, the manufacturing process continues.  
         [0098]    The heating preferably comprises a gradual heating of the casting  200  and the repair material plug  226 . The predetermined conditions also provide for a gradual cooling of the molten material  227 . Gradual heating and cooling minimizes temperature gradients formed during repair, thus mediating the residual stresses generated in the defect area  207 . Again, the above-described optimization with respect to partial penetration and maintaining a surface-tension governed suspension of the molten material  227  in the through-hole  220  must be observed, Other predetermined conditions for heating are as described above. Accordingly, a further description is not provided.  
         [0099]    Another repair method, as embodied by the invention, for the repair of a defect, such as bumper holes in a casting  300  with the casting core removed, will now be discussed with reference to FIGS.  20 - 23  and the flow chart of FIG. 24. The casting process is, for example but not limited to, an investment casting process. The casting  300  relies upon bumpers for casting due to the complexity of the casting  300 . Because investment casting is known in the art, an explanation of the process is omitted.  
         [0100]    If the casting process uses bumpers, the repair method for bumper hole defects comprises first locating the defects  305 , in step S 200 . Location of the defects  305  is accomplished after removal, separation, or reduction of the ceramic casting core (not illustrated).  
         [0101]    Once the defect  305  has been located, a repair material  325  is positioned at the defect area  307  (dashed line in the Figures) of the cast article  300  that is proximate the bumper hole  320 , in step S 201 . The figures illustrate the repair material  325  on the non-bumper hole surface  301  of the casting  300 . However, the scope of the invention comprises the repair material  325  being located on the bumper hole surface  302 .  
         [0102]    The repair material  325  is preferably the same material as the casting  300 . Alternatively, the repair material  325  may be another material that is metallurgically and physically compatible with the casting  300 .  
         [0103]    The repair material  325  is provided generally in the form of a plug  326 . The plug  326  has volume greater that the volume of the bumper hole  320 . The volume of the repair material plug  326  should be sufficient to completely fill the bumper hole  320 . In other words, the volume of the filler material  325  is greater than the volume of the bumper hole  320 . This volume will assure that the repair material plug  326 , when melted, will completely fill the bumper hole  320 . Any residual stresses that may be formed in the process are believed to be concentrated in the last portion of the molten material to re-solidify, for example in the areas outside of the bumper hole and above the top surface. Thus, any residual stresses that may cause cracks or other such defects can be removed by further machining of the repaired area.  
         [0104]    Once the repair material plug  326  has been located at the defect area  307 , the area is heat treated, in step S 203 , with partial penetration of the casting  300 , for example with an electron beam. This partial-penetration heat treatment prevents the electron beam from harming anything located behind the casting  300 . The heat in step S 203  is applied under predetermined conditions to bring at least a portion of surrounding material of the casting  300  and the repair material plug  326  into a molten condition  327 , as shown in FIG. 22.  
         [0105]    With the surrounding material of the casting  300  and the repair material plug  326  molten  327 , the molten material is retained in the casting  300  by the surface tension of the molten material  300 . However, the molten material  327  is sufficiently fluid to permit it to flow and conform to the surfaces  301  and  302  of the casting  300 , as illustrated in FIGS. 22 and 23. The principles of surface tension are well known, and a further discussion is omitted.  
         [0106]    The surface tension suspends the molten material  327  in the casting  300 . The electron beam used for heating in step S 203  is balanced to achieve melting of the repair material  325  and the surrounding casting  300  at the defect area  307 , while not disturbing the molten material  327  suspended in the casting  300 . Further, the electron beam strength is also balanced to maintain the suspension of the molten material  327  and avoid full penetration of the casting  300 .  
         [0107]    The molten material  327 , after flowing in step S 204 , is re-solidified in step S 205 . The excess material remaining on the repaired casting surface can be removed by, for example, at least one of a machining process and a benching process. The core is then removed, by known methods, to result in the repaired casting.  
         [0108]    After the molten material  327  has re-solidified in step S 205  and any excess material is removed, as needed in step S 206 , the repaired casting is inspected at the defect area  307  by an appropriate inspection device to determine whether the repair process has successfully repaired the defect  305 . If the inspection determines that the repair process has successfully repaired the defect, the manufacturing process continues.  
         [0109]    The heating and predetermined conditions for the heating process, as embodied by the invention, are as discussed above. Therefore, a further discussion of these features of the invention is omitted.  
         [0110]    Accordingly, the repair processes, as embodied by the invention, provides an economical, efficient repair of defects, whether intentional or non-intentional, regardless of cause. The repair methods, as embodied by the invention, enable castings to be repaired parts which would otherwise require scrapping of the part. Such repair is desirable from both economical and efficiency considerations.  
         [0111]    While the embodiments described herein are preferred, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made by those skilled in the art, and are within the scope of the invention.