Abstract:
The inventive method involves the inspection of a turbine engine. A damaged component of the turbine engine is identified. Portions of the turbine engine component are removed from the damaged area to accommodate an overlay. The overlay is sized smaller than the turbine engine component. The overlay is then placed in a location previously occupied by the removed portion and attached to the turbine engine component.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to a method of repairing a turbine engine, including parts of the engine. 
         [0002]    Parts of a turbine engine are subject to significant stress and wear. From time to time, it may become necessary to repair or replace these components. Because of their cost, repair may be preferable to the replacement of the entire component. Repair of these components may include the build-up of damaged areas to original dimensions by welding, nickel plating, plasma spraying or other restoration techniques. Further machining of these areas may be required to conform these parts to their original dimensions. Existing techniques for repairing worn parts are both time consuming and labor intensive. 
         [0003]    Accordingly, a need exists to reduce the time and labor associated with repairing the components of a turbine engine. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention concerns a method of repairing a turbine engine. During an inspection of the turbine engine, a part of the turbine engine that requires repair may be identified. Following identification of the part requiring service, portions of the part are removed in the damaged area so as to accommodate an overlay. The overlay allows the part to be reconditioned without the need to build up the damaged area. The overlay is then placed in the area where the portions of the part were removed and then attached. The overlay may be attached by brazing, welding, epoxy based resins or by other adhesive techniques. 
         [0005]    The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  illustrates a known turbine engine that would benefit from the inventive repair technique. 
           [0007]      FIG. 2A  illustrates a turbine engine component, here a compressor shroud segment, of the turbine engine of  FIG. 1 , showing areas of wear. 
           [0008]      FIG. 2B  shows a close-up of the areas of wear shown in  FIG. 2A . 
           [0009]      FIG. 3A  illustrates the removal of portions of the turbine engine component of  FIG. 2  to accommodate an overlay. 
           [0010]      FIG. 3B  shows a close-up of  FIG. 3A  where portions of the turbine engine component have been removed. 
           [0011]      FIG. 4A  illustrates an overlay in relation to the turbine engine component of  FIGS. 2 and 3 . 
           [0012]      FIG. 4B  illustrates another overlay having a larger dimension than the overlay of  FIG. 4A . 
           [0013]      FIG. 5  illustrates a cross-sectional view of a portion of the turbine engine component without wear, showing its original shape. 
           [0014]      FIG. 6  illustrates the turbine engine component of  FIGS. 2A and 3A , highlighting the matching of the overlay shape to the original shape of the portion of the turbine engine component of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0015]      FIG. 1  illustrates an example of a turbine engine  10 , here a turbofan engine, that would benefit from the inventive repair technique. As other types of turbine engines, such as a turbojet engine, will likewise benefit from the inventive technique, the term turbine engine is not limited to the disclosed embodiment. As shown, turbine engine  10  has a fan  12  or propeller through which ambient air is propelled. A multi-stage compressor  14  pressurizes the air and is in communication with a combustor  16  that mixes the compressed air with fuel. The combustor  16  ignites the fuel-air mixture. Expanded gas then passes through turbine section  18  as known. Surrounding turbine section  18  is a shroud  20 , composed of shroud segments, such as shown in  FIGS. 2A and 3A . 
         [0016]    As shown in  FIG. 2A  and  FIG. 5 , turbine engine component  24 , here a compressor shroud segment, may have tongue  58  and face  62  to be received by a groove (not shown) formed in shroud  20  to allow turbine engine component  24  to be fitted in shroud  20 , such as by a dovetail fit of the part. As shown in  FIG. 5 , turbine engine component  24  has original shape  52  having a first turbine engine component surface  56  and a second turbine engine component surface  60 . As shown in FIG.  2 B, first turbine engine component surface  56  and second turbine engine component surface  60  may become worn (shown schematically) in damaged area  28  so that turbine engine component  24  will not be secured to shroud  20  as closely as the original part. 
         [0017]    Rather than replace turbine engine component  24 , the inventive technique, as shown in  FIGS. 3A and 3B , eliminates portion  36  of turbine engine component  24  proximate damaged area  28  so as to accommodate overlay  40  as shown in  FIGS. 4A and 6 . In this way, the expense of part replacement may be eliminated and, as will be seen, significant time and labor required to build-up the worn part avoided. Overlay  40 , as shown in  FIG. 6 , has first overlay surface  64  and second overlay surface  68 . With reference to  FIG. 5  and  FIG. 6 , it can be seen that first overlay surface  64  mimics the shape, here planar, of first turbine engine component surface  56  while second overlay surface  68  mimics second turbine engine component surface  60 , here a curved and planar shape. Because a portion of overlay  40  conforms generally to original shape  52  of turbine engine component  24 , overlay  40  reduces time and labor involved in repairing turbine component  24 . In other words, machining and resurfacing of first overlay surface  64  and second overlay surface  68  are not required. Overlay  40  mimics areas of anticipated wear of turbo engine component  24  so that only small strips of material are used. 
         [0018]    In addition, first overlay  40  may be made of the same material as turbine engine component  24 . The materials are matched to ensure expansion coefficient of overlay  40  and turbo engine component  24  are consistent with each other. The hardness of turbine engine component  24  may be different to allow a part to wear longer, if harder, or to be more delicate to surrounding shroud  20 , if softer. Overlay  40  is also provided with attachment surface  80  so that it may be placed in location  100  previously occupied by removed portion  36  proximate damaged area  28 . Overlay  40  may be roll formed from sheet metal into strips. 
         [0019]    To attach overlay  40  to turbine engine component  24 , portion  36  of turbine engine component  24  may be removed, as shown in  FIG. 3B , so that overlay  40  will fit onto turbine engine component  24  more easily and more closely to the original dimensions of turbine engine component  24 . Portion  36  may be removed by machining, such as by turning or milling, or other known techniques. The amount of machining should be done with reference to the size of overlay  40 . 
         [0020]    As shown in  FIG. 4A , overlay  40  is then position in location  100 , an area formerly occupied by removed portion  36 , to determine whether its fit is adequate. Further machining of damaged area  28  may be required. Once overlay  40  fits into location  100  sufficiently, overlay  40  is then welded at points A and B as shown in  FIG. 6 , such as by laser, electron beam, tungsten inert gas, or other known welding technique. Alternatively, overlay  40  may be brazed or glued along attachment surface  80  to attach overlay  40  to turbine engine component  24 . Suitable glues/adhesives include, but are not limited to, Durabond™ 7025 high temperature aluminum putty, Durabond™ 7032 high temperature stainless putty, Duralco® 4703 structural epoxy adhesive and casting compound, or Duralco® 4701 one component toughened adhesive, all available from Cotronics Corp., Brooklyn, N.Y. 
         [0021]    Because the amount of wear may vary over time and between turbine engine components, a number of overlays of differing sizes may be available for selection by a repair technician so that the overlay may more closely fit in location  100  of damaged area  28 . Accordingly, as shown in  FIGS. 4A and 4B , a repair technician would have the option of choosing between two or more differently sized overlays, here overlay  40  and overlay  48 . Like overlay  40 , overlay  48  is shaped in the same way as overlay  40 , including having the same first overlay surface  64  and second overlay surface  68 , both of which mimic first turbine engine component surface  56  and second engine turbine component surface  60 , respectively, as explained. However, second overlay  48  is shown in  FIG. 4B  as thicker than overlay  40  shown in  FIG. 4A . Overlay  40  has thickness T 1  while overlay  48  has thickness T 2 . T 2  is greater than T 1 . Accordingly, if there is significant wear to damaged area  28 , overlay  48  may be selected by a repair technician instead of overlay  40 . 
         [0022]    The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.