Abstract:
A method of hole defect repair includes removing one or more defects at or near a desired hole shape in a substrate by removing a non-concentric portion of the substrate proximate the desired hole shape, and welding a filler material to the substrate after removing the non-concentric portion of the substrate.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to methods of repairing substrates, and more particularly to methods of repairing damaged substrates having holes disposed therethrough.  
         [0002]     It is possible to repair worn, corroded, or otherwise damaged holes in metallic substrates. However, known repair techniques cause excessive removal of parent substrate material. For instance, in order to repair a crack that has formed at a perimeter of a rivet hole in a flange made of 6061 aluminum (Al), the hole is remachined to a larger diameter to remove the crack. In other words, a circular hole would be remachined co-axially with the centerline axis of the existing (and damaged) rivet hole and to a diameter larger than the desired (i.e., blueprint) rivet hole diameter. A bushing is then press-fit or adhesively bonded to the flange inside the remachined hole to produce a repaired hole at the desired blueprint specifications, for parameters such as size and shape. However, this type of repair is not a structural repair, and the load-carrying capabilities of the repaired structure are less than ideal. Also, because of the parent flange material removal, there is a finite number of times the repair can be performed. Therefore, there is a need for improved methods of repairing damaged holes in metallic substrates.  
       BRIEF SUMMARY OF THE INVENTION  
       [0003]     The present invention provides an alternative method for repairing damage to a substrate with a hole. Hole defect repair according to the present invention includes removing one or more defects at or near a desired hole shape in a substrate by removing a non-concentric portion of the substrate proximate the desired hole shape, and welding a filler material to the substrate after removing the non-concentric portion of the substrate. In some embodiments, post-weld finishing may be necessary to obtain the final desired hole shape in the substrate. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]      FIG. 1A  is a schematic representation of a repair pattern for a hole in a substrate with a crack.  
         [0005]      FIG. 1B  is a schematic representation of the substrate of  FIG. 1A  after a filler material has been welded to the substrate.  
         [0006]      FIG. 1C  is a schematic representation of the substrate of  FIGS. 1A-1B  after finishing processes.  
         [0007]      FIG. 2  is a schematic representation of another repair pattern for a hole in a substrate with a crack.  
         [0008]      FIG. 3  is a schematic representation of a parabolic repair pattern for a hole in a substrate with a crack.  
         [0009]      FIG. 4A  is a schematic representation of a complex repair pattern for a hole in a substrate with circumferential damage and a crack.  
         [0010]      FIG. 4B  is a schematic representation of the substrate of  FIG. 4A  after a filler material has been welded to the substrate.  
         [0011]      FIG. 4C  is a schematic representation of the substrate of  FIGS. 4A-4B  after finishing processes.  
         [0012]      FIG. 5A  is a schematic representation of a parabolic repair pattern for a hole in a substrate with a crack.  
         [0013]      FIG. 5B  is a schematic representation of the substrate of  FIG. 5A  after a filler material has been welded to the substrate, and with a substantially solid insert positioned within the hole.  
         [0014]      FIG. 6  is a schematic representation of a filler material welded to a substrate with a hole in a parabolic repair pattern, and a hollow insert positioned within the hole. 
     
    
     DETAILED DESCRIPTION  
       [0015]     Metal parts having bolt holes, rivet holes, and other similar holes and openings can become worn, corroded, or otherwise oversized or damaged. Damage at or near such holes can include circumferential damage, cracks, corrosion, pitting, elongation, etc. due to localized wear. Such damage can be repaired to return the part, and more specifically the hole formed in the part, back to desired specifications (i.e., returning the hole to blueprint specifications). According to the present invention, the damage can be removed by first conducting localized machining (or other suitable material removal processes) and then welding the part with additional material to provide a hole with desired characteristics (e.g., size, shape and location). In some situations, additional finishing steps, such as additional machining, may be conducted to complete the repair process.  
         [0016]     In order to repair a damaged substrate, the damage is first identified. Known nondestructive inspection (NDI) techniques, such as visual, flourescent penetrant inspection (FPI), eddy current, ultrasonic and x-ray techniques, etc. can be used. Once the damage has been identified, an appropriate repair procedure can be selected. “Discrete damage”, as referred to herein, means damage to a substrate at or near a hole where the hole is otherwise substantially dimensionally acceptable. Discrete damage, such as one or more localized cracks located at or near a perimeter of a hole in a substrate, can be repaired as follows.  FIG. 1A  is a schematic representation of substrate  100  with substantially circular hole  102  therethrough, which is defined by hole centerline axis  104  and hole perimeter  106  at radius R H  about axis  104 . Crack  108  in substrate  100  extends from perimeter  106  of hole  102 . Moon-shaped pattern  110  is established around crack  108 . An outer edge of pattern  110  is defined by pattern centerline axis  112  and pattern perimeter  114  at a radius R P  about axis  112 . Pattern centerline axis  112  is spaced from hole centerline axis  104 , and is located within hole perimeter  106 . An inner edge of pattern  110  is defined by a portion of hole perimeter  106 . Crack  108  is located entirely within pattern  110 . Radius R P  is smaller than radius R H , although such a relationship is not required and radius R P  will vary depending on the size and location of crack  108 .  
         [0017]     Material of substrate  100  is removed within pattern  110 , which removes all of the material of substrate  100  containing crack  108 . Material can be removed by machining (e.g., using a reamer, drill bit, or other tooling), or any other suitable material removal processes. In practice, pattern  110  can be defined in reference to desired tooling for removing material of substrate  100 , for instance, a desired drill bit. It is generally desired that removal of material of substrate  100  (i.e., the parent material) be reduced. In other words, it is desired to leave as much of substrate  100  intact as is possible, while still removing crack  108  in its entirety. This can be accomplished through selection of parameters such as the location of pattern centerline axis  112  and the length of radius R P .  
         [0018]     Once material of substrate  100  is removed within pattern  110 , weld material  124  is welded to substrate  100  to fill at least a portion  126  of pattern  110 . The weld material fills at least a part of the pattern  110  where material of substrate  100  was removed to at least approximately define hole  102  with desired specifications. With certain substrates for aerospace applications, such as 6061 aluminum (Al), Inconel® 718 (a high strength austenitic nickel-chromium-iron alloy) and titanium (Ti) 6-4, conductive heat resistance welding can be used. Examples of conductive heat resistance welding processes are found in U.S. Pat. Nos. 6,545,244 and 6,281,467. In some situations, other welding processes can also be used such as gas tungsten arc welding (GTAW) and resistance welding. Weld material  124  is a weldable material selected according to the desired application, and can be the same material as substrate  100  or another material. For example, suitable combinations of substrate (i.e., the parent material) and weld material (i.e., the filler) are: Inconel® 718 (substrate) and Inconel® 718 (filler); Ti-6Al-4V (substrate) and commercially pure Ti (filler) or Ti-6Al-4V (filler); Al 6061 (substrate) and Al 4043 (filler) or Al 6061 (filler); Thermospan® (a low-expansion, precipitation hardenable iron-based alloy available from Carpenter Technology Corp., Wyomissing, Pa.) (substrate) and Inconel® 625 (filler) or Thermospan® (filler); and Waspaloy (a nickel-base, precipitation hardenable alloy) (substrate) and Waspaloy (filler). In addition, the weldable filler materials disclosed in U.S. Pat. No. 6,742,698 and U.S. Pat. App. Pub. No. 2005/0061858 may be suitable weld materials  124  for some applications.  
         [0019]     In some situations, weld material  124  (i.e., the filler) will not be formed to final specifications and tolerances immediately following the welding process, such as shown in  FIG. 1B . In such situations, additional finishing steps can be conducted. For instance, excess weld material  128  may be present within a perimeter of a desired hole location  130 . Excess weld material  128  can be removed by machining (e.g., using a reamer, drill bit, or other tooling), or other material removal processes. After finishing, hole  102  substantially matches desired hole location  130 , as shown in  FIG. 1C .  
         [0020]     It is possible to utilize other patterns for removing and welding material in order to repair a hole in a substrate.  FIG. 2  is a schematic representation of another repair pattern  210  for hole  202  (having centerline axis  204  and radius R H ) in substrate  200  with crack  208 . Pattern  210  is generally moon-shaped, and has an outer edge defined by pattern centerline axis  212  and perimeter  214  at radius R P2  about axis  212 . Axis  212  is located outside hole perimeter  206 .  FIG. 3  is a schematic representation of U-shaped or parabolic pattern  310  for hole  302  (having centerline axis  304 ) in substrate  300  with crack  308 . Pattern  310  has perimeter  314 , which extends between two spaced points along perimeter  306  of hole  302 . The procedure described above with respect to  FIG. 1A through 1B  can be conducted using patterns  210  and  310  as shown and described with respect to  FIGS. 2 and 3 , respectively.  
         [0021]     In some situations, a metal part may have multiple types of damage. For instance, a part may have non-discrete damage (e.g., corrosion damage over a significant area) as well as discrete damage (e.g., multiple localized cracks) near a hole. A metallic part with multiple types of damage can be repaired according to the present invention using a complex repair pattern made up of a plurality of repair patterns or repair pattern regions.  FIG. 4A  is a schematic representation of substrate  400  with desired hole location  402  indicated thereon, which is defined by hole centerline axis  404  and hole perimeter  406  at radius R HD  about axis  404 . Corroded hole perimeter  407  is located near desired hole location  402 . As shown in  FIG. 4A , a hole originally formed at desired hole location  402  has circumferential corrosion, which has enlarged the original hole slightly and produced an irregular shaped hole defined by corroded hole perimeter  407 . Crack  408  in substrate  400  extends from corroded hole perimeter  407 .  
         [0022]     A first, substantially circular pattern  410  is defined by first pattern perimeter  414  at radius R P3  about hole centerline axis  404 . First pattern  410  is coaxial with desired hole location  402 . Radius R P3  is larger than radius R HD , such that first pattern  410  encompasses all of corroded hole perimeter  407 . A second, U-shaped or parabolic pattern  416  is defined by second pattern perimeter  418 . Second pattern  416  is located around a portion of crack  408  at first pattern perimeter  414 , such that all of crack  408  is located within first pattern  410  and second pattern  416 .  
         [0023]     Material of substrate  400  is removed within first pattern  410 , which removes material of substrate  400  in which corroded perimeter  407  is defined. Material of substrate  400  is also removed within second pattern  416 , which removes material of substrate  400  containing a portion of crack  408  (i.e., the portion of crack  408  not contained in first pattern  410 ). Material may be removed within first pattern  410  and then from within second pattern  416 . Material can be removed by machining (e.g., using a reamer, drill bit, or other tooling), or other material removal processes. In further embodiments, additional patterns can be defined on substrate  400 . The particular number, shape, and arrangement of material removal patterns will vary depending on the particular types of damage to substrate  400 .  
         [0024]     Once material has been removed from within first pattern  410  and second pattern  416 , weld material  424  (i.e., the filler) material is welded within at least a portion  426  of first pattern  410  and within all of second pattern  416 , as shown in  FIG. 4B . This welding process can be generally similar to that described above with respect to  FIG. 1A-1C . The weld material  424  is generally welded within first pattern  410  and second pattern  416  at the same time. However, it is possible to weld filler  424  within second pattern  416  and then separately weld filler  424  within first pattern  410 . Machining can be performed between such separate welding steps. Moreover, different welding techniques can be used. For instance, second pattern  416  can be welded using GTAW techniques and first pattern  410  can be welded using conductive heat resistance welding techniques, etc.  
         [0025]     After filler  424  has been welded within at least portion  426  of first pattern  410  and within all of second pattern  416 , finishing process can be conducted as needed. For example, machining can be conducted as described above with respect to  FIG. 1A-1C  in order to form a finished hole through substrate  400  according to desired specifications (i.e., to blueprint specifications). As shown in  FIG. 4C , finished hole  432  substantially matches desired hole location  402 .  
         [0026]     In situations where only discrete damage to a substrate is present near a hole, an insert (i.e. a weld backing) can be used during welding in order to reduce and preferably eliminate the need for post-weld finishing, such as post-weld machining. When conducting a repair procedure using an insert according to the present invention, the damage is first identified and material of the substrate is then removed around the location of the damage, as described above. Then, generally prior to welding the filler to the substrate, an insert is positioned within the hole.  
         [0027]      FIG. 5A  is a schematic representation of substrate  500  having hole  502  defined therethrough. Hole  502  is defined by hole centerline axis  504  and hole perimeter  506  at radius R H  about axis  504 . Crack  508  extends from hole perimeter  506 . U-shaped or parabolic repair pattern  510 , which is defined by pattern perimeter  514 , is located at hole perimeter  506 .  
         [0028]      FIG. 5B  is a schematic representation of substrate  500  after substrate material has been removed within pattern  510 . Substantially solid insert  520  is positioned within hole  502 . Insert  520  is formed to the desired dimensions of desired hole shape. Insert  520  can be constructed of any suitable material, such as, for example, a common casting core, a refractory metal or a quartz weld backing, etc. Insert  520  can be provided in the form of a pre-shaped solid material, or provided as a formable paste made of a powder and a suitable binder. Insert  520  should have a melting temperature greater than substrate  500  and weld material  524 .  
         [0029]     Weld material  524  is welded where material was removed from pattern  510 . Weld material  524  abuts substrate  500  and insert  520 . Insert  520  acts like a casting mold during the welding process in order to form weld material  524  in a desired shape as weld material  524  becomes flowable during welding. This more closely provides desired hole specifications during the welding process, while reducing and preferably eliminating the need for post-weld finishing (e.g., machining of the weld material to desired hole specifications).  
         [0030]     In a further embodiment, the insert can be hollow.  FIG. 6  is a schematic representation of hollow insert  620  positioned within hole  602  (defined by hole centerline axis  604  and hole perimeter  606 ) in substrate  600 , with weld material  624  in a U-shaped or parabolic shaped opening defined adjacent to hole  602 . Hollow insert  620  is generally similar to substantially solid insert  520  shown and described with respect to  FIG. 5B .  
         [0031]     Although the present invention has been described with reference to several alternative embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For instance, many different repair pattern shapes and arrangements can be utilized.