Abstract:
A method for repairing a cantilevered stator vane includes removing a damaged portion leaving a remaining vane portion. A supplemental airfoil portion is then selected and is attached to the remaining vane portion to provide a repaired cantilevered stator vane.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This disclosure relates to repairing gas turbine engine components and, more particularly, to repairing a cantilevered stator vane. 
         [0002]    Gas turbine engine components, such as turbine blades, turbine vanes, compressor blades, compressor vanes, or other components typically operate in a relatively high stress and high temperature environment. The stresses and temperature may result in damage to the component from corrosion, erosion, deformation, or the like. Depending on the type and severity of the damage, the components may be repaired and reused. 
         [0003]    The type of repair process depends on the type of damage. For example, relatively elevated stresses and temperatures within the engine may cause deformation of a blade, vane, or other component. For a vane that is cantilevered, associated stresses may cause twisting of the vane, which could result in cracks being formed in an airfoil portion. Alternatively, a foreign object may enter the gas turbine engine and hit a cantilevered vane causing the vane to become cracked or chipped. 
         [0004]    The cantilevered vanes are configured in vane segments, with one vane segment including a plurality of vanes. When one vane becomes damaged beyond predetermined repair limits, the entire vane segment is generally replaced. Replacement of an entire vane segment is costly compared to repairing individual damaged vanes. 
         [0005]    Accordingly, there is a need for a cost-effective method to repair individual vanes without requiring an entire vane segment to be replaced. 
       SUMMARY OF THE INVENTION 
       [0006]    A method for repairing a cantilevered stator vane having an airfoil supported by a platform includes removing a damaged portion of the airfoil leaving a remaining vane portion. A supplemental airfoil portion is then selected and is attached to the remaining vane portion to provide a repaired cantilevered stator vane. 
         [0007]    In one example, the supplemental airfoil portion is welded to the remaining vane portion forming a weld attachment interface. After welding, the weld attachment interface is blended and smoothed out, and is then heat treated. 
         [0008]    In another aspect, the remaining vane portion is smoothed and cleaned prior to attachment of the supplemental air foil portion. 
         [0009]    In one example, the damaged portion is removed by cutting across a width of the airfoil. The cut is located just beyond the damaged portion, or the airfoil can be cut at a location near the platform. If the cut is just beyond the damaged portion, the supplemental airfoil portion is cut to the proper length and is then attached to the remaining vane portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows. 
           [0011]      FIG. 1  is a highly schematic view of a turbine engine. 
           [0012]      FIG. 2  is a cross-sectional view of a compressor section of the turbine engine. 
           [0013]      FIG. 3  is a schematic representation of a damaged cantilevered stator vane. 
           [0014]      FIG. 4  is a schematic representation of a repaired cantilevered stator vane. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]      FIG. 1  illustrates selected portions of an example turbine engine  10 , such as a gas turbine engine used for propulsion. In this example, the turbine engine  10  is circumferentially disposed about an engine centerline  12 . The turbine engine  10  includes a fan  14 , a compressor section  16 , a combustion section  18 , and a turbine section  20 . The compressor section  16  and the turbine section  20  include corresponding blades  22  and stator vanes  24 . As is known, air compressed in the compressor section  16  is mixed with fuel and burned in the combustion section  18  to produce hot gasses that are expanded in the turbine section  20 .  FIG. 1  is a highly schematic presentation for illustrative purposes only and is not a limitation on the disclosed examples. Additionally, there are various types of gas turbine engines, many of which could benefit from the examples disclosed herein and are not limited to the designs shown. For example, a gas turbine engine may contain a gearbox disposed between the turbine section  20  and the fan  14 , allowing the fan  14  to turn at a different speed than the turbine. Also, for example, the compressor section  16  can include low pressure and high pressure sections with a combination of blades and disks that are coupled to rotate about the engine centerline  12 . Further, the gas turbine engine may be used to turn an electrical generator instead of being used for propulsion. 
         [0016]      FIG. 2  illustrates a more detailed example of the compressor section  16 , and specifically shows a high pressure section  30  of the compressor. It should be understood that only the upper cross-section of the high pressure section  30  is shown in  FIG. 2 , with the lower cross-section being similarly configured to that of the upper cross-section as the compressor includes a component that circumscribes the engine centerline  12 . It should also be understood that the following description is also applicable to a low pressure section of the compressor section  16 . 
         [0017]    As shown in  FIG. 2 , the high pressure section  30  includes a plurality of high pressure compressor (HPC) disks  32  that are mounted to rotate with a main shaft  34  ( FIG. 1 ) about the engine centerline  12 . In the example shown, an attachment structure  36 , which is mounted for rotation with the main shaft  34 , is used to attach the HPC disks  32  to the main shaft  34 . A support structure  38  has a portion that extends in a direction that is generally parallel to the engine centerline  12 . One end of each of the HPC disks  32  is secured to the support structure  38 , and the HPC disks  32  extend radially inwardly to distal ends that are positioned adjacent to the main shaft  34 . 
         [0018]    When assembled in the compression section  16 , the blades  22  of the high pressure section  30  each have one end secured to the support structure  38  and extend radially outward to distal ends that are positioned adjacent to an outer shroud portion  40  and/or engine casing  42 . Each of the blades  22  has a root portion  44  that extends radially inward from a platform  46  in a direction toward the engine centerline  12 . Each blade  22  also includes an airfoil portion  48  that extends radially outward from the platform  46  in a direction away from the engine centerline  12 . The root portion  44  is secured within a recess  50  formed in the support structure  38 . 
         [0019]    The stator vanes  24  of the high pressure section  30  comprise cantilevered stator vanes  24  that each extends radially inward to distal ends that are positioned near the support structure  38 . The cantilevered stator vanes  24  each include one outer shroud portion  40 , an airfoil portion  52 , and a platform  54 . The airfoil portion  52  has one end fixed to the outer shroud portion  40  and radially inward from the platform  54  toward the engine centerline  12 . The outer shroud portion  40  includes feet  56  that extend in an axial direction and contact the engine casing  42 . 
         [0020]    An outer air seal  58  cooperates with the feet  56  to hold the outer shroud portion  40  in place against the engine casing  42 . The outer air seal  58  includes a first axially extending portion  60  that engages one foot  56   a  on one outer shroud portion  40  for a first cantilevered stator  24   a  and a second axially extending portion  62  that engages another foot  56   b  on the outer shroud portion  40  for a second cantilevered stator  24   b  that is positioned adjacent to the first cantilevered stator  24   a . One blade  22  is positioned between the first  24   a  and second  24   b  cantilevered stators to provide an alternating pattern of blades  22  and vanes  24 . The outer air seal  58  also includes a flange portion  64  that extends radially outward in a direction away from the engine centerline  12 . The flange portion  64  extends between portions of the engine casing  42  to facilitate providing a sealed interface. 
         [0021]    It should be appreciated that the feet  56  may also be held by an inner diameter of the engine casing  42  in slots formed similar to those provided by outer air seal foot portions  56   a  and  56   b . The slots in the inner diameter of the engine casing  42  position the cantilevered stator vanes  24  both axially and radially. 
         [0022]    When the airfoil portion  52  of one of the cantilevered stator vanes  24  becomes damaged, the airfoil portion  52  may be repaired by replacing only the damaged air foil portion  52 ′. In other words, the entire vane segment of stator vanes does not have to be replaced; only the damaged portion of the single vane is repaired. If the airfoil portion  52  is damaged at a point indicated at  70  ( FIG. 3 ), the damaged airfoil portion  52 ′ is removed from the vane segment at an airfoil location that is radially outward of the damage point  70 , or at an airfoil location that is at or near a junction of the airfoil portion  52  to the platform  54 . 
         [0023]    In one exemplary embodiment, the damaged airfoil portion  52 ′ may be separated from the vane segment by cutting the airfoil portion  52  across an entire width thereof. The airfoil portion  52  may be cut using an electric discharge machine (EDM) process or other machining processes. Once the airfoil portion  52  is removed, the remaining portion  72  (see  FIG. 3 ) of the airfoil is smoothed out and cleaned. A new or supplemental airfoil portion  74  ( FIG. 4 ) is then selected and welded to the remaining portion  72 . If the original airfoil portion  52  is not removed at or near the platform  54 , the supplemental airfoil portion  74  is cut to a desired length and is then welded to the remaining portion  72 . A linear friction welder, gas tungsten arc welding (GTAW), which is also known as tungsten inert gas (TIG) welding, or other welding methods are used to secure the supplemental airfoil portion  74  to the remaining portion  72  of the original airfoil portion  52  at a weld interface  76 . This welding process is similar to welding processes for integrated blade rotors (IBRs). 
         [0024]    After welding, the weld interface  76  is blended and smoothed and the repaired component is heat treated in a known manner for weld interfaces. The repaired component then undergoes nondestructive testing (NDT) such as fluorescent penetrant inspection (FPI) and X-ray inspection, for example. Once NDT has been satisfied, the repaired component can then be reinstalled in the turbine engine  10 . Using this repair process provides a significant cost savings as opposed to replacing the entire component. 
         [0025]    Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments. 
         [0026]    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 disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.