Patent Publication Number: US-2023151735-A1

Title: Airfoil joining apparatus and methods

Description:
FIELD 
     The present subject matter relates generally to gas turbine engines and, more particularly, to apparatus and methods for joining an airfoil component to a portion of a gas turbine engine airfoil. 
     BACKGROUND 
     Typical aircraft propulsion systems include one or more gas turbine engines, which each generally include a turbomachine. The turbomachine includes, in serial flow order, a compressor section, a combustion section, a turbine section, and an exhaust section. In operation, air is provided to an inlet of the compressor section where one or more axial compressors progressively compress the air until it reaches the combustion section. Fuel is mixed with the compressed air and burned within the combustion section to provide combustion gases. The combustion gases are routed from the combustion section to the turbine section. The flow of combustion gases through the turbine section drives the turbine section and is then routed through the exhaust section, e.g., to atmosphere. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present disclosure, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG.  1    provides a side schematic view of an airfoil extending radially outward from a platform and a dovetail extending in a radially opposite direction from the airfoil. 
         FIG.  2    provides a perspective schematic view of a blisk. 
         FIG.  3 A  provides a perspective view of a portion of an airfoil repair component positioned against a cropped airfoil. 
         FIG.  3 B  provides a perspective view of a portion of an airfoil repair component positioned against a cropped airfoil. 
         FIG.  4    provides a perspective view of a portion of a blisk with an airfoil repair component positioned against a cropped airfoil. 
         FIG.  5    provides a perspective view of an airfoil repair component having a projection on an airfoil joining face thereof. 
         FIG.  6    provides a side cross-section view of an electrode assembly of an airfoil repair system. 
         FIG.  7    provides a side cross-section view of a cropped airfoil electrode of an electrode assembly of an airfoil repair system. 
         FIG.  8    provides a side cross-section view of a repair component electrode of an electrode assembly of an airfoil repair system. 
         FIG.  9 A  provides a top view of a repair component electrode of an electrode assembly of an airfoil repair system. 
         FIG.  9 B  provides a perspective view of a portion of the repair component electrode of  FIG.  9 A . 
         FIG.  10 A  provides a side perspective view of a repair component electrode body of a repair component electrode. 
         FIG.  10 B  provides a side perspective view of a repair component electrode insert of a repair component electrode. 
         FIG.  10 C  provides an end perspective view of a repair component electrode. 
         FIG.  11    provides a perspective view of an electrode assembly of an airfoil repair system having an alignment assembly. 
         FIG.  12    provides a perspective view of a feedback assembly of a tooling assembly of an airfoil repair system. 
         FIG.  13    provides a side perspective view of an airfoil portion of a tooling assembly of an airfoil repair system for a blisk. 
         FIG.  14    provides a side perspective view of a tooling assembly of an airfoil repair system for a blisk. 
         FIG.  15    provides a flow diagram illustrating a method for repairing an airfoil. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to present embodiments of the disclosure, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the disclosure. 
     As used herein, the terms “first,” “second,” and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. 
     The terms “forward” and “aft” refer to relative positions within a gas turbine engine or vehicle and refer to the normal operational attitude of the gas turbine engine or vehicle. For example, with regard to a gas turbine engine, forward refers to a position closer to an engine inlet and aft refers to a position closer to an engine nozzle or exhaust. 
     The terms “upstream” and “downstream” refer to the relative direction with respect to fluid flow in a fluid pathway. For example, “upstream” refers to the direction from which the fluid flows, and “downstream” refers to the direction to which the fluid flows. 
     The terms “coupled,” “fixed,” “attached to,” and the like refer to both direct coupling, fixing, or attaching, as well as indirect coupling, fixing, or attaching through one or more intermediate components or features, unless otherwise specified herein. 
     The singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. 
     Approximating language, as used herein throughout the specification and claims, is applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” “approximately,” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value, or the precision of the methods or machines for constructing or manufacturing the components and/or systems. The approximating language may refer to being within a +/−1, 2, 4, 10, 15, or 20 percent margin in either individual values, range(s) of values, and/or endpoints defining range(s) of values. 
     Here and throughout the specification and claims, range limitations are combined and interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. 
     A typical compressor has multiple stages or rows of rotor blades and corresponding stator vanes that sequentially increase the pressure of the air as it flows in an axial downstream direction. In some compressors, the compressor blades include dovetails for being removably mounted in a corresponding dovetail slot in the perimeter of a rotor disk. The dovetail-to-dovetail slot configuration permits the individual manufacture of each blade, and the individual replacement thereof in the event of blade damage during operation. However, it can be expensive to completely replace damaged blades, particularly when the damage is located near the tip of the blade such that a majority of the blade and the dovetail remains intact and undamaged. 
     In other compressors, the compressor blades may be provided as a bladed disk, also referred to as a blisk. A blisk includes a row of rotor airfoils integrally formed with the perimeter of a rotor disk in a one-piece or unitary configuration. As such, unlike the removably mounted blades described above, in the event of a damaged blisk airfoil, either the entire blisk must be replaced or the damaged airfoil must be removed and replaced without damaging adjacent airfoils, which could be expensive and/or complicated. Other airfoils within a turbomachine, for example in the fan and turbine section, also may have either a dovetail configuration or be part of a blisk and face similar drawbacks or limitations as described above. 
     Accordingly, improved airfoil repair and airfoil handling methods and apparatus would be desirable. 
     Generally, the present subject matter provides methods and apparatus for airfoil repairs. For instance, the present subject matter provides methods and apparatus for removing a damaged portion of an airfoil to form a cropped airfoil and joining an airfoil repair component to the cropped airfoil to repair the airfoil. Such airfoil repairs can be time-consuming and/or expensive, while often also having low yield rates, but the methods and apparatus described herein can improve success and yield while reducing repair time and costs for repair of individual airfoils, e.g., airfoils secured to a disk via a dovetail, and/or integral airfoils, e.g., blisk airfoils that are integrally formed with a disk. For example, an airfoil repair component includes a repair attachment section for attaching the airfoil repair component to the cropped airfoil at a cropped airfoil attachment section. In at least some embodiments, the repair attachment section is oversized with respect to the cropped airfoil attachment section such that the repair attachment section has a repair chord length longer than a cropped chord length of the cropped airfoil attachment section and a repair width wider than a cropped width of the cropped airfoil attachment section. A locally or wholly oversized airfoil repair component can improve the chances of proper alignment between the airfoil repair component and the cropped airfoil (i.e., an airfoil with a damaged portion removed), with increased material margin or stock for post-joining processing to achieve the net shape of the original airfoil. Further, the present subject matter provides an electrode assembly comprising a repair component electrode and a cropped airfoil electrode, which surround the airfoil repair component and the cropped airfoil, respectively, and are positioned to align the airfoil repair component with the cropped airfoil such that when a current is passed therethrough under an applied force, the airfoil repair component is attached to the cropped airfoil. For instance, the present subject matter provides methods and apparatus for securing the airfoil repair component and/or the cropped airfoil within an electrode to eliminate over constraint and permit more accurate positioning of the airfoil repair component and/or cropped airfoil, while also reducing or eliminating hand tools in loading and unloading components from their respective electrodes, e.g., by using spring loaded design features and other easily hand-manipulated design features. Moreover, the present subject matter provides features for process feedback, environmental shielding, and/or stabilization that can produce higher quality welds or joints between the airfoil repair component and the cropped airfoil, better and/or faster alignment of the airfoil repair component with respect to the cropped airfoil, and/or easier post-joining extraction of the repaired airfoil. 
     Referring now to the drawings, wherein identical numerals indicate the same elements throughout the figures,  FIG.  1    is a schematic view of an airfoil  100 , e.g., an airfoil of a gas turbine engine.  FIG.  2    is a schematic view of a bladed disk  122 , also known as a blisk, having a plurality of airfoils  100  integrally formed with a rotor disk, such as may be used in a gas turbine engine. In at least some embodiments, the gas turbine engine may be a turbofan jet engine including a fan section and a core turbine engine disposed downstream from the fan section. The core turbine engine generally includes a substantially tubular outer casing that encases, in serial flow relationship, a compressor section including a booster or low pressure (LP) compressor and a high pressure (HP) compressor; a combustion section; a turbine section including a high pressure (HP) turbine and a low pressure (LP) turbine; and a jet exhaust nozzle section. A high pressure (HP) shaft or spool drivingly connects the HP turbine to the HP compressor. A low pressure (LP) shaft or spool drivingly connects the LP turbine to the LP compressor. During operation of the turbofan jet engine, a volume of air passes across fan blades of a fan disposed in the fan section. A first portion of the air is directed or routed into a bypass airflow passage and a second portion of the air is directed or routed into the LP compressor. The ratio between the first portion of air and the second portion of air is commonly known as a bypass ratio. 
     The pressure of the second portion of air is increased as it is routed through the high pressure (HP) compressor and into the combustion section, where it is mixed with fuel and burned to provide combustion gases. The combustion gases are routed through the HP turbine where a portion of thermal and/or kinetic energy from the combustion gases is extracted via sequential stages of HP turbine stator vanes that are coupled to the outer casing of the core turbine engine and HP turbine rotor blades that are coupled to the HP shaft or spool, thus causing the HP shaft or spool to rotate, thereby supporting operation of the HP compressor. The combustion gases are then routed through the LP turbine, where a second portion of thermal and kinetic energy is extracted from the combustion gases via sequential stages of LP turbine stator vanes that are coupled to the outer casing of the core turbine engine and LP turbine rotor blades that are coupled to the LP shaft or spool, thus causing the LP shaft or spool to rotate, thereby supporting operation of the LP compressor and/or rotation of the fan. The combustion gases are subsequently routed through the jet exhaust nozzle section of the core turbine engine to provide propulsive thrust. 
     Simultaneously, the pressure of the first portion of air is substantially increased as the first portion of air is routed through the bypass airflow passage before it is exhausted from a fan nozzle exhaust section, also providing propulsive thrust. The HP turbine, the LP turbine, and the jet exhaust nozzle section at least partially define a hot gas path for routing the combustion gases through the core turbine engine. 
     In some embodiments, the airfoil  100  depicted in  FIGS.  1  and  2    may be a compressor blade, such as a rotor blade of the LP compressor or the HP compressor of the turbofan jet engine described above. In other embodiments, the airfoil  100  depicted in  FIGS.  1  and  2    may be a turbine blade, such as a rotor blade of the LP turbine or the HP turbine of the turbofan jet engine. In still other embodiments, the airfoil  100  may be another airfoil of the turbofan jet engine described above, of another gas turbine engine, or of another assembly or system having one or more airfoils. 
     As shown in the depicted embodiments of  FIGS.  1  and  2   , the airfoil  100  includes a concave pressure side  102  opposite a convex suction side  104 . Opposite pressure side  102  and suction side  104  of the airfoil  100  extend radially along a span S from a root  106  to a tip  108  at the radially outermost portion of the airfoil  100 . That is, the root  106  defines a first radial extremity of the airfoil  100 , and the tip  108  defines a second radial extremity of the airfoil  100 , with the root  106  and the tip  108  spaced apart along a radial direction R. The pressure side  102  and the suction side  104  of the airfoil  100  extend axially along a chord length c between a leading edge  110  and an opposite trailing edge  112 . The leading edge  110  defines a forward end of the airfoil  100 , and the trailing edge  112  defines an aft end of the airfoil  100 , with the leading edge  110  and the trailing edge  112  spaced apart along an axial direction A. Further, the pressure side  102  defines an outer pressure surface  114  of the airfoil  100 , and the suction side  104  defines an outer suction surface  116  of the airfoil  100 . 
     More generally, the airfoil  100  may be described as having a first side opposite a second side, with either of the first side and the second side being the pressure side  102  or the suction side  104  and the other of the first and second sides being the other of the pressure side  102  and the suction side  104 . Each of the first side and the second side extend axially between a first edge and an opposite second edge, with either of the first edge and the second edge being the leading edge  110  or the trailing edge  112  and the other of the first and second edges being the other of the leading edge  110  and the trailing edge  112 . Further, the first side defines a first outer surface of the airfoil  100 , and the second side defines a second outer surface of the airfoil  100 , with either of the first outer surface and the second outer surface being the outer pressure surface  114  or the outer suction surface  116  and the other of the first and second outer surfaces being the other of the outer pressure surface  114  and the outer suction surface  116 . 
     In the embodiment of  FIG.  1   , the airfoil  100  extends radially outward from a platform  118 . A dovetail  120  extends from the platform  118  in a radially opposite direction from the airfoil  100 . The dovetail  120  is configured to be received within a complementarily shaped dovetail slot in a rotor disk (not shown). In the depicted embodiment, the airfoil  100 , the platform  118 , and the dovetail  120  are secured to one another, or integrally formed as a single piece or component, such that the airfoil  100 , platform  118 , and dovetail  120  together are removably received in the rotor disk. It will be appreciated that a plurality of airfoils  100  are secured to the rotor disk via a corresponding number of dovetails  120  to form a stage of rotor blades, e.g., a stage of compressor blades of a gas turbine engine compressor. The plurality of airfoils  100  are circumferentially spaced apart from one another, or spaced apart along a circumferential direction C, to define a ring of airfoils  100 , similar to the airfoils  100  of the blisk  122  shown in  FIG.  2   . 
     As further illustrated in  FIG.  1   , a fillet  105  defines a transition between the pressure side  102  and the platform  118 , as well as the suction side  104  and the platform  118 . Moreover, the airfoil  100  defines a section line SL, e.g., at one half of the distance between the tip  108  at the leading edge  110 , and a leading edge fillet tangency taken at the fillet  105  between the leading edge  110  and the platform  118 . 
     As previously stated,  FIG.  2    depicts a bladed disk or blisk  122  that has multiple airfoils  100  extending from a rotor disk  124  at an integral platform  126 . It will be appreciated that the airfoils  100  of the blisk  122  are configured as described with respect to  FIG.  1   . However, rather than a separate platform  118  and dovetail  120  for each airfoil  100  as in the embodiment of  FIG.  1   , the blisk  122  comprises a single platform  126  that serves as a platform for each of the multiple airfoils  100 . Further, no dovetails  120  are necessary in the embodiment of  FIG.  2    because the airfoils  100  are integrally formed with the rotor disk  124 . As such, while the airfoils  100  of  FIG.  1    are removable from the described rotor disk, the airfoils  100  of  FIG.  2    are not removable with respect to the rotor disk  124  but, instead, are integrally formed with the platform  126  and rotor disk  124  to form the blisk  122 . 
     From time to time, an airfoil  100  may become damaged during use. For instance, the airfoil  100  may experience localized damage during service, e.g., through inadvertent tip rub against a shroud or casing, impingement by a foreign object, and/or other contact between the airfoil  100  and another component, object, or substance. The airfoil  100  may develop a damaged area  128 , such as illustrated on an airfoil  100  of the blisk  122  shown in  FIG.  2   , which may be, e.g., a cavity. As used herein, the term “cavity” refers to any hollow space within the airfoil  100 , such as an opening, crack, gap, aperture, hole, etc. Such a cavity or damaged area  128  can be formed on or in the airfoil  100  through normal use and generally represents an area where fragments, chunks, pieces, etc. of the original airfoil material have broken off or been liberated from the airfoil  100 . 
     In at least some instances, the damaged area  128  hinders the functionality of the airfoil  100  such that the airfoil  100  should be repaired. Generally, the airfoil  100  could be repaired by replacing the entire airfoil  100  or through removal and replacement of a portion  130  of the airfoil  100  containing the damaged area  128 , which is referred to herein as the damaged portion  130 . In some embodiments, the damaged portion  130  may be removed along a plane below or radially inward with respect to the section line SL ( FIG.  1   ), such that more than half of the airfoil  100  is removed. In other embodiments, the damaged portion  130  may be removed along a plane above or radially outward with respect to the section line SL, such that less than half of the airfoil  100  is removed. 
     It will be appreciated that replacement of the entire airfoil  100  generally is more expensive than replacing only the damaged portion  130  of the airfoil  100 . Further, at least for the blisk  122 , replacing the entire airfoil  100  generally involves a complicated manufacturing process and could risk damaging the platform  126  and/or rotor disk  124  of the blisk  122 , as well as adjacent, undamaged airfoils  100 . Other complications of replacing the entire airfoil  100  may be realized as well. 
     Accordingly, to minimize replacement costs and manage complexity, the present subject matter provides methods, components, systems, and apparatus for replacing only the damaged portion  130 . For example, turning to  FIGS.  3 A,  3 B, and  4   , an airfoil component or airfoil repair component  200  to replace the damaged portion  130  is provided. As described in greater detail herein, the damaged portion  130  is removed from the airfoil  100  (e.g., above, below, or at the section line SL shown in  FIG.  1   ) to form a cropped airfoil  140 , such that the cropped airfoil  140  has a radial height less than the span S of the airfoil  100  ( FIG.  1   ). The cropped airfoil  140  comprises the airfoil root  106  and, thus, remains secured (or can be re-secured) to the platform  118  and dovetail  120  of the individual airfoils  100  described with respect to  FIG.  1   , or remains integral with the rotor disk  124  and platform  126  of the blisk  122  of  FIG.  2   . Further, the cropped airfoil  140  comprises the remaining portions of the pressure side  102 , suction side  104 , leading edge  110 , and trailing edge  112 , which are referred to herein as the cropped pressure side  102   c , the cropped suction side  104   c  ( FIGS.  3 A,  3 B ), the cropped leading edge  110   c  ( FIG.  7   ), and the cropped trailing edge  112   c  ( FIG.  7   ). 
     Like the airfoil  100 , the cropped airfoil  140  may have features that more generally be described as a cropped first side and an opposite cropped second side, which are either of the cropped pressure side  102   c  or the cropped suction side  104   c . Each of the cropped first side and the cropped second side extend axially between a cropped first edge and an opposite cropped second edge, which are either of the cropped leading edge  110   c  or the cropped trailing edge  112   c.    
     Referring to  FIG.  4   , because the airfoil repair component  200  attaches to the cropped airfoil  140  to yield a repaired airfoil  100 , the airfoil repair component  200  is configured similar to the airfoil  100  described with respect to  FIGS.  1  and  2   . More particularly, referring to  FIGS.  3 A,  3 B, and  4   , the airfoil repair component  200  comprises a body  205  having a repair pressure side  202  opposite a repair suction side  204 , and a repair leading edge  210  opposite a repair trailing edge  212 . Further, the repair pressure side  202  and the repair suction side  204  extend axially between the repair leading edge  210  and the repair trailing edge  212 . More generally, the airfoil repair component  200  comprises a body  205  having a first side opposite a second side, with the first and second sides being either of the repair pressure side  202  and the repair suction side  204 , and the first and second sides extend axially between a first edge and a second edge, with the first and second edges being either of the repair leading edge  210  and the repair trailing edge  212 . Like the cropped airfoil  140 , the airfoil repair component  200  has a radial height that is less than the span S of the airfoil  100  ( FIG.  1   ). 
     The body  205  of the airfoil repair component  200  defines a repair attachment section  242  for attaching the airfoil repair component  200  to the cropped airfoil  140 . As shown in  FIGS.  3 A,  3 B, and  4   , the cropped airfoil  140  comprises a cropped airfoil attachment section  142 , which is the radially outermost section of the cropped airfoil  140 . Likewise, as depicted in  FIGS.  3 A,  3 B, and  4   , the repair attachment section  242  is the radially innermost section of the airfoil repair component  200 . 
     To attach the airfoil repair component  200  to the cropped airfoil  140 , the repair attachment section  242  is aligned with the cropped airfoil attachment section  142  and the airfoil repair component  200  is secured to the cropped airfoil  140 , e.g., by welding the airfoil repair component  200  to the cropped airfoil  140  as described in greater detail below. For instance, the repair attachment section  242  defines a repair joining face  244  ( FIGS.  3 A,  3 B,  5 ,  8 ,  9 A,  9 B ) and the cropped airfoil attachment section  142  defines a cropped joining face  144  ( FIG.  7   ), and the repair joining face  244  interfaces with the cropped joining face  144  as the airfoil repair component  200  is aligned with the cropped airfoil  140 . Then, the airfoil repair component  200  may be joined to the cropped airfoil  140 , e.g., along the interface between the repair joining face  244  and the cropped joining face  144 , through a welding or other appropriate joining process. It will be appreciated that the repair joining face  244  defines an inner end of the airfoil repair component  200  and an opposite tip  208  ( FIGS.  4 ,  8   ) defines an outer end of the airfoil repair component  200 , while the cropped joining face  144  defines an outer end of the cropped airfoil  140  and the opposite root  106  defines an inner end of the cropped airfoil  140 . 
     As illustrated in  FIGS.  3 A and  3 B , at least the repair attachment section  242  is oversized with respect to the cropped airfoil attachment section  142 . For example, the repair attachment section  242  has a repair chord length c r  longer than a cropped chord length c c  of the cropped airfoil attachment section  142 , i.e., the repair chord length longer c r  than a cropped chord length c c  of the cropped airfoil attachment section  142 . As another example, the repair attachment section  242  is oversized with respect to the cropped airfoil attachment section  142  such that a repair width w r  of the body  205  at the repair attachment section  242  is wider than a cropped width w c  of the cropped airfoil  140  at the cropped airfoil attachment section  142 . In some embodiments, the repair attachment section  242  may be oversized with respect to the cropped airfoil attachment section  142  such that either the repair chord length c r  is longer than the cropped chord length c c  or the repair width w r  is wider than the cropped width w c . In other embodiments, such as illustrated in  FIGS.  3 A and  3 B , both the repair chord length c r  and the repair width w r  are larger than the cropped chord length c c  and the cropped width w c , respectively, i.e., the repair chord length c r  is longer than the cropped chord length c c  and the repair width w r  is wider than the cropped width w c . 
     Like the chord length c described above, the repair chord length c r  extends along the axial direction A from the repair leading edge  210  to the repair trailing edge  212  (or from the component first edge to the component second edge), and the cropped chord length c c  extends along the axial direction A from the cropped leading edge  110   c  to the cropped trailing edge  112   c  (or from the cropped first edge to the cropped second edge). The width of each airfoil section is measured along the circumferential direction C, from the pressure side to the suction side. Thus, the repair width w r  extends from the repair pressure side  202  to the repair suction side  204  (or between the component first side and component second side of the airfoil repair component  200 ), and the cropped width w c  extends along the circumferential C from the cropped pressure side  102   c  to the cropped suction side  104   c  (or between the cropped first side and the cropped second side of the cropped airfoil  140 ). At least the repair attachment section  242  of the airfoil repair component  200  is oversized with respect to the cropped airfoil attachment section  142  of the cropped airfoil  140  such that the repair attachment section  242  extends beyond the cropped airfoil attachment section  142  axially or chordwise as well as circumferentially or widthwise. 
     Referring still to  FIGS.  3 A and  3 B , in at least some embodiments, the oversized repair attachment section  242  defines a flared extension of the body  205 . As shown in  FIGS.  3 A and  3 B , the repair attachment section  242  flares outward from the body  205 , with the repair width w r  of the repair attachment section  242  wider than a body width w b  of the body  205 . The flared or oversized repair attachment section  242  provides a larger repair joining face  244  than would be defined by a remainder of the body  205 , which provides a larger surface to align with the cropped joining face  144  that can help in aligning or positioning the airfoil repair component  200  with the cropped airfoil  140 . For example, the larger repair joining face  244  of the oversized repair attachment section  242  may be easier to align with the cropped joining face  144  than a joining face that was approximately the same size and shape as the cropped joining face  144  of the cropped airfoil  140 . That is, the flared, oversized repair attachment section  242  provides a larger land on the airfoil repair component  200  to improve initial part fitment allowance. The rest of the body  205  may be net shape, e.g., the flared extension defined by the repair attachment section  242  may be the only oversized portion of the airfoil repair component  200 , with the remainder of the airfoil repair component  200  being the same shape and size as the portion of the original airfoil  100  that the airfoil repair component  200  is replacing. 
     Turning to  FIG.  4   , in some embodiments, the entire airfoil repair component  200  is oversized with respect to the cropped airfoil  140 . For instance, the body  205  of the airfoil repair component is oversized with respect to the cropped airfoil attachment section  142  such that the body  205  away from or outside of the repair attachment section  242  has a body chord length c b  longer than the cropped chord length c c  and a body width w b  wider than the cropped width w c . In addition to the body  205 , the repair attachment section  242  is oversized with respect to the cropped airfoil attachment section  142  as described above, i.e., the repair chord length c r  is longer than the cropped chord length c c , and the repair width w r  is wider than the cropped width w c . As such, the airfoil repair component  200  may be overall larger than the cropped airfoil  140 . 
     As shown in  FIG.  4   , the oversized, larger airfoil repair component  200  thus has “extra” or additional material, which may be machined away after the airfoil repair component  200  is attached to the cropped airfoil  140  to recover the desired net shape of the original undamaged airfoil  100 . That is, as illustrated in  FIG.  4   , the net shape of the airfoil  100  is contained within the oversized airfoil repair component  200 , and the net shaped is revealed through processing (e.g., machining, deformation processing, etc.) after the airfoil repair component  200  is attached to the cropped airfoil  140 . In at least some embodiments, the oversized airfoil repair component  200  provides a greater margin of error in aligning the airfoil repair component  200  with the cropped airfoil  140 , e.g., as compared to an airfoil repair component  200  that is enlarged or oversized locally, such as only in the region of the repair attachment section  242 . For example, an airfoil repair component  200  that is enlarged or oversized overall (instead of a locally enlarged/oversized airfoil repair component  200 ) may be used to repair a damaged airfoil  100  of a blisk  122  because there is less room to observe/detect and ensure the alignment of the airfoil repair component  200  with the cropped airfoil  140  on a blisk  122  because other airfoils  100  are adjacent the cropped airfoil  140 . The overall enlarged/oversized airfoil repair component  200  allows less precise placement of the airfoil attachment section  242  against the cropped airfoil attachment section  142  (e.g., compared to a locally enlarged or oversized airfoil repair component  200 , which may be used with a removable airfoil  100 ) because the additional material can be machined away after attachment to define the shape of the airfoil  100 . 
     In contrast, the airfoil repair component  200  illustrated in  FIGS.  3 A and  3 B  is locally enlarged or oversized, which an increased chord length c r  and increased width w r  only in the repair attachment section  242  as described above. The body  205  of the airfoil repair component  200  shown in  FIGS.  3 A and  3 B  has the final shape of the airfoil  100 , i.e., the body  205  is shaped like the original, undamaged airfoil  100 . In at least some embodiments, the repair attachment section  242  is consumed as the airfoil repair component  200  is attached to the cropped airfoil  140  such that, unlike the overall enlarged/oversized airfoil repair component  200  of  FIG.  4   , little to no processing is required once the airfoil repair component  200  is attached to the cropped airfoil  140  because the body  205  of the airfoil repair component  200  already defines the final shape of the airfoil  100 . 
     As shown in  FIGS.  3 A,  3 B, and  4   , the repair joining face  244  and the cropped joining face  144  interface in a plane-to-plane interaction. Stated differently, there is plane-to-plane contact between the airfoil repair component  200  and the cropped airfoil  140 . This interaction is designed to minimize the influence of alignment inaccuracies and counteract joining-induced stresses. When the airfoil repair component  200  is joined to the cropped airfoil  140  in a welding process, the repair joining face  244  and the cropped joining face  144  are consumed in the welding process as the two components are joined together. The planar interaction between the airfoil repair component  200  and the cropped airfoil  140  can help ensure the airfoil repair component  200  is properly aligned with respect to the cropped airfoil  140  to define the overall shape of the airfoil  100  once the joining process, and, if needed, any post-joining processing such as machining, deformation processing (e.g., cold or hot working, etc.), is complete. 
     Referring to  FIG.  5   , the repair joining face  244  may include one or more projections  246  extending away from the repair joining face  244 , e.g., toward the cropped joining face  144  ( FIG.  7   ) when the airfoil repair component  200  is positioned with respect to the cropped airfoil  140  for joining the airfoil repair component  200  to the cropped airfoil  140 , such as shown in  FIG.  6   . Additionally or alternatively, although not shown in  FIG.  5   , the cropped joining face  144  may include one or more projections  246  extending away from the cropped joining face  144 , e.g., toward the repair joining face  244  when the airfoil repair component  200  is positioned with respect to the cropped airfoil  140  for joining the airfoil repair component  200  to the cropped airfoil  140 . The one or more projections  246  change the profile of the repair joining face  244  (and/or the cropped joining face  144 , where the cropped joining face  144  includes one or more projections  246  such as shown in  FIG.  5    with respect to the repair joining face  244 ), e.g., to help direct current during a joining process, and each projection  246  may have any suitable shape and size. As shown in  FIG.  5   , the depicted projection  246  narrows the repair joining face  244  from the body  205  toward the cropped airfoil  140  such that a smaller surface area of the airfoil repair component  200  contacts the cropped airfoil  140 —e.g., compared to the surface area of the airfoil joining face  244  without the projection  246 —when the airfoil repair component  200  and cropped airfoil  140  are brought together for joining. Thus, the one or more projections  246 , which are consumed during the joining process, help localize the current when the joining process begins, which can help focus heat in a desired area early in the joining process. 
     In some embodiments, the airfoil  100  comprises a twist along the span S. For example, in  FIG.  2    the root  106  of the airfoil  100  may be offset from the tip  108  of the airfoil  100  along the circumferential direction C such that, e.g., the leading edge  100  does not extend in a generally straight line from the root  106  to the tip  108 . The twist, offset, or deviation from linearity need not exist over the entire span S, e.g., the airfoil  100  may not have a twist along a length of the span S. For instance, in some embodiments such as depicted in  FIG.  4   , the airfoil  100  may extend substantially linearly along the radial direction R from about mid-span to the tip  108 , i.e., the twist may be located between the root  106  and mid-span. Nonetheless, regardless of the location or degree of the twist, when repaired with an airfoil repair component  200 , the repaired airfoil  100  should also comprise a twist such that the repaired airfoil  100  has the same final shape as the original, undamaged airfoil  100 . 
     As illustrated in  FIG.  3 A , in at least some embodiments, the airfoil repair component  200  may be shaped to eliminate the twist in the repair attachment section  242 . For example, the repair attachment section  242  extends substantially straight or linearly along the radial direction R while the airfoil repair component  200  radially above the repair attachment section  242  incorporates a twist along the span S ( FIG.  1   ). In some embodiments, the cropped airfoil attachment section  142  of the cropped airfoil  140  also may be substantially straight or linear along the radial direction R. For instance, as shown at a location  145  in  FIG.  3 A , the twist may be removed, or the cropped airfoil  140  may be straightened, in the region of the cropped airfoil attachment section  142  using a localized coining operation or similar process. Having a straight or linear cropped airfoil attachment section  142  and/or repair attachment section  242  can help define a planar interaction between the cropped airfoil  140  and the airfoil repair component  200  along the cropped joining face  144  and the repair joining face  244 , which can help improve alignment between the cropped airfoil  140  and the airfoil repair component  200 . Further, the straight or linear cropped airfoil attachment section  142  and/or repair attachment section  242  are consumed during the joining process, e.g., as the airfoil repair component  200  is welded to the cropped airfoil  140 , such that the airfoil geometry that is modified to remove or be without the twist disappears during the joining process, leaving the repaired airfoil  100  with only the twist of the original airfoil  100 . 
     Although the flared or locally oversized airfoil repair component  200  is described with respect to an individual airfoil  100  ( FIGS.  3 A and  3 B ) and the overall oversized repair component  200  is described with respect to a blisk  122  ( FIG.  4   ), it will be appreciated that the features described with respect to  FIGS.  3 A and  3 B  and the features described with respect to  FIG.  4    apply to airfoil repair components  200  for either individual airfoils  100  or airfoils  100  incorporated into a blisk  122 . That is, the illustrations provided herein are not intended to limit the application of the features shown therein. Further, the projections  246  likewise can be used for airfoil repair components  200  and/or cropped airfoils  140  for either individual airfoils  100  or airfoils  100  incorporated into a blisk  122 . Similarly, other features described herein, although shown or described with respect to individual airfoils  100  or blisk airfoils  100 , may be used for airfoil repair components  200  and/or cropped airfoils  140  for either individual airfoils  100  or airfoils  100  incorporated into a blisk  122 . 
     Turning now to  FIGS.  6  through  14   , in at least some embodiments, the airfoil repair component  200  is part of an airfoil repair system  300  ( FIGS.  12 ,  14   ). The airfoil repair system  300  includes components for locating, positioning, and holding the airfoil repair component  200  with respect to the cropped airfoil  140 . The airfoil repair system  300  also includes components facilitating the joining of the airfoil repair component  200  to the cropped airfoil  140 . 
     Referring particularly to  FIG.  6   , the airfoil repair system  300  includes an electrode assembly  302 . The electrode assembly  302  comprises a repair component electrode  304  and a cropped airfoil electrode  306 . The repair component electrode  304  receives the airfoil repair component  200 , and the cropped airfoil electrode  306  receives the cropped airfoil  140 . As described herein, an electrical current is passed through the repair component electrode  304 , with the airfoil repair component  200  positioned therein, and the cropped airfoil electrode  306 , with the cropped airfoil  140  positioned therein, to join the airfoil repair component  200  to the cropped airfoil  140 . For example, a solid state resistance welding (SSRW) technique may be used to weld the airfoil repair component  200  to the cropped airfoil  140  by passing electrical current through the airfoil repair component  200  and the cropped airfoil  140  while the repair joining face  244  is in contact with (or is interfacing with) the cropped joining face  144 ; the repair component electrode  304  and cropped airfoil electrode  306  also can provide a compressive axial force, e.g., toward the end of the current pulses, to help weld the airfoil repair component  200  and cropped airfoil  140 . Other welding or joining techniques or processes may be used as well. 
     Turning to  FIG.  7   , in some embodiments, the cropped airfoil electrode  306  comprises a dovetail block  308 , an electrode body  310 , and a retention assembly  312 . As previously described, the cropped airfoil  140  formed from an individual or removable airfoil  100 , as illustrated in  FIG.  1   , comprises a dovetail  120  that helps secure the airfoil  100  to a rotor disk. As depicted in  FIG.  7   , the dovetail  120  is receivable within the dovetail block  308  of the cropped airfoil electrode  306 . For instance, the dovetail block  308  defines a dovetail opening  314  having a shape complementary to the shape of the dovetail  120 , and the dovetail  120  is received in the complementary shaped dovetail opening  314  of the dovetail block  308 . Thus, the dovetail block  308  helps secure and/or stabilize the cropped airfoil  140  within the cropped airfoil electrode  306  and constrains the cropped airfoil  140  along a stacking axis A S  ( FIG.  6   ) or along any longitudinal orientation where stabilization is beneficial to the joining process. The dovetail block  308  may or may not be constrained with respect to the cropped airfoil electrode  306 . For example, the dovetail block  308  may be locked into position using a set screw or the like, or no hard constraint may be placed on the dovetail block  308  such that it is free to move with respect to the cropped airfoil electrode  306 . It will be appreciated that in other embodiments, e.g., where the cropped airfoil  140  does not include a dovetail  120 , such as in blisk  122  embodiments, the dovetail block  308  of the cropped airfoil electrode  306  may be omitted. 
     Further, as depicted in  FIG.  7   , the cropped airfoil  140  is removably secured to the electrode body  310  by one-handed manipulation of the retention assembly  312 . For example, the retention assembly  312  comprises a thrust element  316 , such as a lever or button, and a stop  318 , which may be a pin or the like. The thrust element  316  and the stop  318  are disposed opposite one another along the cropped chord length c c , e.g., when the cropped airfoil  140  is loaded in the cropped airfoil electrode  306 , one of the thrust element  316  and the stop  318  is disposed against the cropped leading edge  110   c , and the other of the thrust element  316  and stop  318  is disposed against the cropped trailing edge  112   c . The thrust element  316  may be manipulated by a user, e.g., using a single finger (such as a thumb) or a single hand, to load and unload the cropped airfoil  140  from the cropped airfoil electrode  306 . For instance, each of the thrust element  316  and the stop  318  provides a point constraint on the cropped airfoil  140 , and the thrust element  316  is manipulable, or moveable, to relax the point constraint provided by the thrust element  316  to load and/or unload the cropped airfoil  140  with respect to the cropped airfoil electrode  306 . More particularly, the thrust element  316  may be moved away from the cropped airfoil  140 , or the area where the cropped airfoil  140  is positioned when loaded into the electrode body  310 , to load and/or unload the cropped airfoil  140  from the cropped airfoil electrode  306 . 
     Referring now to  FIG.  8   , in at least some embodiments, the airfoil repair component  200  similarly is removably secured to the repair component electrode  304 . For example, like the cropped airfoil electrode  306 , the repair component electrode  304  shown in  FIG.  8    comprises an electrode body  320  and a retention assembly  322 . To differentiate between the electrode body  310  and the electrode body  320  more easily, in at least some instances herein, the electrode body  310  of the cropped airfoil electrode  306  may be referred to as the cropped airfoil electrode body  310 , and the electrode body  320  of the repair component electrode  320  may be referred to as the repair component electrode body  320 . 
     The airfoil repair component  200  is removably secured to the electrode body  320  by one-handed manipulation of the retention assembly  322 . In the embodiment of  FIG.  8   , the retention assembly  322  comprises a thrust element  326 , such as a lever or button, and a stop  328 , which may be a pin or the like. The thrust element  326  and the stop  328  are disposed opposite one another along the repair chord length c r . For instance, when the airfoil repair component  200  is loaded in the repair component electrode  304 , one of the thrust elements  326  and stop  328  is disposed against the repair leading edge  210 , and the other of the thrust elements  326  and stop  328  is disposed against the repair trailing edge  212 . 
     The thrust element  326  may be manipulated by a user, e.g., using a single finger (such as a thumb) or a single hand, to load and unload the airfoil repair component  200  from the repair component electrode  304 . For example, each of the thrust element  326  and the stop  328  provides a point constraint on the airfoil repair component  200 . The thrust element  326  is manipulable, or moveable, to relax the point constraint provided by the thrust element  326  to load and/or unload the airfoil repair component  200  with respect to the repair component electrode  304 . That is, the thrust element  326  may be moved away from the airfoil repair component  200 , or the area where the airfoil repair component  200  is positioned when loaded into the electrode body  320 , to load and/or unload the airfoil repair component  200  from the repair component electrode  304 . 
       FIGS.  9 A and  9 B  illustrate another embodiment of the repair component electrode  304 . In the embodiment of  FIGS.  9 A and  9 B , the retention assembly  322  includes a stabilization element  324  defining an opening  325  that receives the airfoil repair component  200 , with a perimeter  323  extending about the opening  325 . Further, the stabilization element  324  includes a stabilization arm  327 , which contacts the repair suction side  204  to urge the airfoil repair component  200  into a first stop  328   a  contacting the repair pressure side  202 , and a second stop  328   b , which provides at least a point constraint on the repair leading edge  210 . Referring particularly to  FIG.  9 B , the stabilization arm  327  includes a set screw  329  for tightening the stabilization arm  327  against the airfoil repair component  200 , with one or more springs used to retract the stabilization arm  327 . In this way, the smallest force may be used to hold the airfoil repair component  200  in place, such that the airfoil repair component  200  is not over-constrained. In other embodiments, other means may be used to advance and retract the stabilization arm  327  with respect to the airfoil repair component  200 . 
     In various embodiments, the components of the stabilization element  324  (i.e., perimeter  323 , stabilization arm  327 , first stop  328   a , and second stop  328   b ) may provide point, line, and/or planar constraint on the airfoil repair component  200 , depending on, e.g., the configuration of the stabilization element component and the airfoil repair component  200 . It will be appreciated that the stabilization arm  327  may be manipulated to constrain or release the airfoil repair component  200 , with the perimeter  323 , stabilization arm  327 , first stops  328   a , and second stop  328   b  of the stabilization element  324  providing sufficient constraint to stabilize the airfoil repair component  200  for the joining process without over-constraining the airfoil repair component  200 . 
     Turning now to  FIGS.  10 A and  10 B , in some embodiments, the repair component electrode  304  comprises a repair component electrode insert  330  that surrounds at least a portion of the airfoil repair component  200  and is removable with respect to the repair component electrode body  320 . As shown in  FIG.  10 A , the repair component electrode insert  330  is received in the repair component electrode body  320 . In  FIG.  10 B , the repair component electrode insert  330  is shown removed from the repair component electrode body  320 . 
     As shown in  FIG.  10 B , the repair component electrode insert  330  defines an inert gas manifold  332  for receipt of an inert gas. Further, the repair component electrode insert  330  defines a first plurality of grooves  334   a  extending from the inert gas manifold  332  along a first outer surface  336   a  of the repair component electrode insert  330  and a second plurality of grooves  334   b  extending from the inert gas manifold  332  along a second outer surface  336   b  of the repair component electrode insert  330 . The first plurality of grooves  334   a  and the second plurality of grooves  334   b  direct the inert gas IG from the inert gas manifold  332  along a first side  338   a  and a second side  338   b , respectively, of the repair component electrode insert  330  to define an inert gas shield around the airfoil repair component  200 . 
     An inert gas shield is useful, e.g., when the airfoil  100  and airfoil repair component  200  are formed from a reactive material, such as a titanium alloy or the like. For instance, a reactive material may have undesired reactions during some joining processes, such as solid state resistance welding (SSRW), which could contaminate the weld interface between the cropped airfoil  140 , the airfoil repair component  200 . By providing a shield or barrier of inert gas, the undesirable atmospheric reactions can be reduced or eliminated. 
     In the illustrated embodiment of  FIGS.  9 A and  9 B , the repair component electrode insert  330  engages both the leading edge and trailing edge profiles of the airfoil repair component  200 . That is, the repair component electrode insert  330  is shaped such that an inner surface  340  of the repair component electrode insert  330  engages both the repair leading edge  210  and the repair trailing edge  212 . Further, the repair component electrode insert  330  includes a leading edge guide  331   a  and a trailing edge guide  331   b . The leading and trailing edge guides  331   a ,  331   b  are minimally conductive, high temperature and wear resistant guides that help stabilize the relatively thin edges of the airfoil repair component  200 , e.g., in titanium airfoil repair applications. For instance, the leading and trailing edge guides  331   a ,  331   b  hold the leading edge  210  and trailing edge  212 , respectively, to stabilize the airfoil repair component  200 . The leading and trailing edges guides  331   a ,  331   b  can also control heat and the leading edge  210  and trailing edge  212 , respectively, to help prevent overheating the leading and trailing edges  210 ,  212  during the joining process. The leading and trailing edge guides  331   a ,  331   b  may be made from a material selected to minimize conduction, withstand high temperatures, and resist wear. 
     In the depicted embodiment, the repair component electrode insert  330  defines a cavity  342  for receipt of the airfoil repair component  200 . In some embodiments, only one of the repair leading edge  210  and the repair trailing edge  212 , or only a portion of one or both of the repair leading edge  210  and the repair trailing edge  212 , is engaged by the repair component electrode insert  330 . Engagement between the repair component electrode insert  330  and the airfoil repair component  200  can help stabilize airfoil repair component  200  within the repair component electrode  304  by preventing buckling or lapping of the thinner leading and trailing edges of the cropped airfoil  140  and/or the airfoil repair component  200 . 
     As further shown in  FIGS.  10 A and  10 B , in some embodiments the repair component electrode insert  330  comprises a first half  330   a  and a second half  330   b . In the depicted embodiment, the repair component electrode insert  330  is divided chordwise or along the axial direction with respect to the airfoil repair component  200  to define the first half  330   a  and second half  330   b . Each of the first half  330   a  and the second half  330   b  defines a portion of the inert gas manifold  332  such that together the two halves  330   a ,  330   b  define the inert gas manifold  332 . 
     Moreover, each of the first half  330   a  and the second half  330   b  of the depicted repair component electrode insert  330  defines a portion of the plurality of grooves  334 . More particularly, the first half  330   a  defines a first plurality of grooves  334   a  of the plurality of grooves  334 , and the second half  330   b  defines a second plurality of grooves  334   b  of the plurality of grooves  334 . Each of the first plurality of grooves  334   a  and the second plurality of grooves  334   b  extends from the inert gas manifold  332  along the respective first half  330   a  and second half  330   b  of the repair component electrode insert  330 . 
     As illustrated in the embodiment of  FIGS.  10 A and  10 B , each groove  334  of the plurality of grooves  334  extends parallel to the remaining grooves  334  of the plurality of grooves  334 . In other embodiments, the plurality of grooves  334  may not all be parallel to one another, but instead, at least one groove  334  of the plurality of grooves  334  may extend in a different direction with respect to one or more of the plurality of grooves  334 . Further, the plurality of grooves  334  may be generally symmetric with respect to the repair component electrode insert  330 . For example, for the halved repair component electrode insert  330  shown in  FIGS.  10 A and  10 B , the number of the first plurality of grooves  334   a  equals the number of the second plurality of grooves  334   b , and each respective groove  334   a  of the first plurality of grooves  334   a  is defined across from a respective groove  334   b  of the second plurality of grooves  334   b  along the widthwise dimension of the airfoil repair component  200 . However, in other embodiments, the plurality of grooves  334  may not be symmetric, e.g., a different number of grooves  334   a  may be defined in the first half  330   a  than the number of grooves  334   b  defined in the second half  330   b.    
     Referring to  FIG.  10 C , in at least some embodiments, the repair component electrode  304  includes serrations  343  defined in the repair component electrode body  320 . The serrations  343  are openings or areas without material in the repair component electrode body  320 . As shown in  FIG.  10 C , each serration  343  includes a change in direction, e.g., a serration  343  includes a first portion angling from a first side of the repair component electrode body  320  toward an opposite second side of the repair component electrode body  320  and a second portion angling from the second side of the repair component electrode body  320  toward the opposite first side of the repair component electrode body  320 . The serrations  343  can act like a spring or other biased member to achieve better or improved contact between the repair component electrode  304  and the airfoil repair component  200 . Further, the serrations  343  can provide cooling, especially at the leading edge  210  and/or trailing edge  212  of the airfoil repair component  200  during the joining process, e.g., to protect the relatively thin leading edge  210  and trailing edge  212 . For example, the serrations  343  can throttle or choke current passing through the repair component electrode  304  to the airfoil repair component  200  at the leading edge  210  and/or trailing edge  212  to help avoid overheating the leading edge  210  and/or trailing edge  212  as the airfoil repair component  200  is joined to the cropped airfoil  140 . 
     Turning now to  FIGS.  11 ,  12 , and  13   , the airfoil repair system  300  includes a tooling assembly  344  for positioning the airfoil repair component  200  with respect to the cropped airfoil  140 . Referring particularly to  FIG.  11   , in at least some embodiments, the tooling assembly  344  comprises an alignment assembly  346 . In the embodiment of  FIG.  11   , the alignment assembly  346  is an independent axis three degree-of-freedom manipulator configured to adjust the position of the airfoil repair component  200  (enclosed within the repair component electrode  304  in  FIG.  11   ) with respect to the cropped airfoil  140  (enclosed within the cropped airfoil electrode  306  in  FIG.  11   ) along three separate axes defined by the cropped airfoil  140 . As shown, the alignment assembly  346  includes a first rotatable knob  348   a , which adjusts the position of the airfoil repair component  200  along a first degree of freedom, the axial direction A or chordwise along the cropped airfoil  140 ; a second rotatable knob  348   b , which adjusts the position of the airfoil repair component  200  along a second degree of freedom, the circumferential direction C or widthwise along the cropped airfoil  140 ; and a third rotatable knob  348   c , which adjusts the position of the airfoil repair component  200  with respect to a third degree of freedom, the stacking axis A S . Using rotatable knobs  348   a ,  348   b ,  348   c  to adjust the position of the airfoil repair component  200  may allow more precise alignment of the airfoil repair component  200  with respect to the cropped airfoil  140  than other modes of alignment. However, it will be appreciated that, in addition to or in place of rotatable knobs, in other embodiments the alignment assembly  346  may utilize other means for adjusting the position or alignment of the airfoil repair component  200  along the various degrees of freedom. It will be appreciated that the illustrated alignment assembly  346  is by way of example only. In other embodiments, the alignment assembly  346  can manipulate or adjust the position of the airfoil repair component  200  and/or the cropped airfoil  140  in any number of degrees of freedom, e.g., less or more than three. 
     Further, using the alignment assembly  346 , the airfoil repair component  200  may be tilted or biased with respect to the cropped airfoil  140 , e.g., to help ensure a desired geometry of the joined airfoil repair component  200  and cropped airfoil  140 . For example, the position of the airfoil repair component  200  may be manipulated along one or more degrees of freedom to control the post-joining (e.g., post-weld) geometry, which can minimize or eliminate post-joining cold working. As such, the alignment assembly  346  can help position the airfoil repair component  200  with respect to the cropped airfoil  140  (e.g., with a few degrees of tilt, such as within a range of 0°-10° with respect to the axial direction A, radial direction R, and/or circumferential direction C, or the like) to closely resemble or approximate the post-joining geometry of the airfoil  100 . 
     Referring now to  FIG.  12   , in at least some embodiments, the tooling assembly  344  comprises a feedback system  350  including at least one feedback device  352  located to determine a position of the airfoil repair component  200  with respect to the cropped airfoil  140  and/or to determine the size (e.g., height, width, and/or thickness) of the airfoil repair component  200 , repair component electrode  304 , etc. Determining the size of the respective component may be referred to as on-machine probing, in which one determines the size of a component and then decides where to position the component for a desired process. 
     In the embodiment of  FIG.  12   , the feedback system  350  includes a first feedback device  352   a  and a second feedback device  352   b  positioned radially outward from the electrode assembly  302 . The first feedback device  352   a  and the second feedback device  352   b  may provide feedback as to the position of the repair component electrode  304  (in which the airfoil repair component  200  is disposed) with respect to the cropped airfoil electrode  306  (in which the cropped airfoil  140  is disposed), or with respect to another reference point or component within the airfoil repair system  300 , and/or as to the size of the airfoil repair component  200  and/or the repair component electrode  304 . The feedback can be used to ascertain whether the airfoil repair component  200  is properly aligned with the cropped airfoil  140  prior to a joining process and, if not, may assist in repositioning the airfoil repair component  200  until the airfoil repair component  200  is adequately aligned with the cropped airfoil  140  to begin the joining process. It will be appreciated that the one or more feedback devices, such as the first feedback device  352   a  and the second feedback device  352   b , may be cameras, non-contact or contact-type gages, non-contact or contact-type measurement devices, or the like or a combination thereof that provide images, location data, and/or other data to a user interface, controller, etc. to allow a user or operator, a controller, etc. to manually or automatically initiate repositioning of the airfoil repair component  200  or the start of the joining process. Further, although not shown in  FIG.  12   , the feedback system  350  may be supported by a frame or other support system that allows the electrode assembly  302  to be removed from and replaced within the field of view or field of sensing of the at least one feedback device  352 , e.g., after one airfoil repair component  200  is joined to one cropped airfoil  140  and another airfoil repair component  200  is prepared to be joined to another cropped airfoil  140 . 
     Turning to  FIG.  13   , a cropped airfoil portion  344 C of the tooling assembly  344  for stabilizing the cropped airfoil  140  of a blisk  122  is illustrated. As shown in  FIG.  13   , in at least some embodiments, the cropped airfoil portion  344 C of the tooling assembly  344  includes a frame  354  that supports a hoop clamp  356 , a hydraulic clamp assembly  358  including an electrode element  360  and hydraulic cylinder  362 , and a band electrode  364 . The hoop clamp  356  and hydraulic clamp assembly  358  stabilize the cropped airfoil  140 , e.g., such that the airfoil repair component  200  can be aligned with the cropped airfoil  140  to perform a joining operation. The hoop clamp  356  is not directly coupled to the frame  354  but is joined to the frame  354  in such a way to avoid inducing any significant stress and/or distortion to the frame  354 , which helps ensure the highest level of accuracy while utilizing the least total material. As depicted in  FIG.  13   , the electrode element  360  of the hydraulic clamp assembly  358  extends from the hydraulic cylinder  362  and presses the cropped airfoil  140  into the band electrode  364 , which is supported by the hoop clamp  356  such that the cropped airfoil  140  is pressed into the hoop clamp  356 . 
     Further, the hoop clamp  356  extends about the hydraulic clamp assembly  358  and is free to slide within the frame  354 , and the hydraulic cylinder  362  is supported by the frame  354 . For example, in the arrangement depicted in  FIG.  13   , the hoop clamp  356  applies an enclosed structural loop of squeezing force to reduce or eliminate bending stress from the frame  354  and other interrelated tooling components. Thus, the tooling assembly  344  decouples the holding elements from the electrodes to help eliminate the bending moment on the cropped airfoil  140  and airfoil repair component  200 . 
     Moreover, one or more openings  366  may be formed in the hoop clamp  356 , as well as other components of the cropped airfoil portion  344 C of the tooling assembly  344 , to accommodate airfoils  100  of the blisk  122  that are adjacent the cropped airfoil  140 . It will be appreciated that the tooling assembly cropped airfoil portion  344 C may be made as compact as possible, e.g., for easier post-joining extraction of the blisk  122 , and the cropped airfoil portion  344 C captures the cropped airfoil  140  to position the blisk  122  and the cropped airfoil  140  with respect to the airfoil repair component  200 . Further, the cropped airfoil portion  344 C of the tooling assembly  344  can help stabilize the cropped airfoil electrode  306  and help ensure contact between the cropped airfoil  140  and the cropped airfoil electrode  306 . Additionally, the cropped airfoil portion  344 C of the tooling assembly  344  helps align the airfoil repair component  200  with the blisk  122  and its cropped airfoil  140 , e.g., as shown in  FIG.  14   . 
       FIG.  14    provides a side perspective view of the tooling assembly  344 , including airfoil-side tooling, i.e., the cropped airfoil portion  344 C, and airfoil repair component-side tooling, i.e., the airfoil repair component portion  344 R. For example, the tooling assembly  344  as illustrated in  FIG.  14    may be used to stabilize a blisk  122  and an airfoil repair component  200 , with the respective repair component electrode  304  and cropped airfoil electrode  306 , while joining the airfoil repair component  200  to a cropped airfoil  140  of the blisk  122 . As such, as shown in  FIG.  14   , the cropped airfoil portion  344 C of the tooling assembly  344  (or segments thereof) may be mounted onto a slide rail  368 , or other similar support element, to help move the blisk  122  with respect to the airfoil repair component portion  344 R of the tooling assembly  344 . As further depicted in  FIG.  14   , the feedback system  350  may be mounted vertically below the cropped airfoil  140  and airfoil repair component  200  in the tooling assembly  344 . It will be appreciated that, in other embodiments, the feedback system  350  may be mounted or supported at any suitable location of the airfoil repair system  300 , e.g., above, below, on one side, at an angle relative to the airfoil repair system  300 , or one or more components of the feedback system  350  may be mounted in one location while one or more components of the feedback system  350  are mounted in one or more different locations. 
     Referring now to  FIG.  15   , the present subject matter also provides methods of repairing an airfoil. As shown in  FIG.  15   , a method  1500  of repairing an airfoil  100  comprises ( 1502 ) removing a damaged portion  130  of the airfoil  100  to form a cropped airfoil  140 . As described herein, the damaged portion  130  may include a damaged area  128 , which is a hollow area or cavity such as an opening, crack, gap, aperture, hole, etc. in the airfoil  100 . For instance, as described with respect to  FIG.  1   , the airfoil  100  may include a section line SL, which may be, e.g., one half of the distance between the tip  108  at the leading edge and a leading edge fillet tangency T. The damaged portion  130  (including the damaged area  128 ) may be removed above, below, or at (or radially outward from, radially inward from, or at) the section line SL. 
     Further, the method  1500  may comprise ( 1504 ) locally removing a spanwise twist from the cropped airfoil  140 , which also may be referred to as coining the cropped airfoil  140  to remove the twist along at least a portion of the airfoil span S. As described herein, e.g., with respect to  FIG.  3 A , in at least some embodiments, the cropped airfoil  140  may be shaped to eliminate the twist in the cropped airfoil attachment section  142 , and the airfoil repair component  200  may be shaped to eliminate the twist in the repair attachment section  242 . For example, each of the cropped airfoil attachment section  142  and the repair attachment section  242  extends substantially straight or linearly along the radial direction R while the remainder of the cropped airfoil  140  and the airfoil repair component  200  incorporates a twist along the span S. Having a straight or linear cropped airfoil attachment section  142  and/or repair attachment section  242  can help define a planar interaction or surface or area contact between the cropped airfoil  140  and the airfoil repair component  200  along the cropped joining face  144  and the repair joining face  244 , which can help improve alignment between the cropped airfoil  140  and the airfoil repair component  200 . Further, the straight or linear section cropped airfoil attachment section  142  and/or repair attachment section  242  are consumed during the joining process, e.g., as the airfoil repair component  200  is welded to the cropped airfoil  140 , such that, during the joining process, the airfoil geometry that is modified to remove or be without the twist is expelled from the weld interface in the form of weld flash, and the repaired airfoil  100  has the twist of the original airfoil  100 . It will be appreciated that, in other embodiments, the original airfoil  100  may not include a spanwise twist such that ( 1504 ) locally removing the spanwise twist may be omitted from the method  1500 . 
     Referring still to  FIG.  15   , the method  1500  further may comprise ( 1506 ) disposing the cropped airfoil  140  in a cropped airfoil electrode  306  and ( 1508 ) disposing an airfoil repair component  200  within a repair component electrode  304 . The cropped airfoil  140 , airfoil repair component  200 , repair component electrode  304 , and cropped airfoil electrode  306  may be configured as described herein, e.g., with respect to  FIGS.  1 - 14   . For instance, the repair component electrode  304  and cropped airfoil electrode  306  may be part of an electrode assembly  302 , and in at least some embodiments, the repair component electrode  304  comprises a repair component electrode insert  330  removably received within a repair component electrode body  320 . The repair component electrode insert  330  may include an inert gas manifold  332  and a plurality of grooves  334  for creating an inert gas shield around the airfoil repair component  200 . 
     The method  1500  also may include ( 1510 ) positioning the airfoil repair component  200  with respect to the cropped airfoil  140 . As described herein, in at least some embodiments, positioning the airfoil repair component  200  with respect to the cropped airfoil  140  comprises locating the repair component electrode  304  using a feedback system to ascertain a position of the airfoil repair component  200  with respect to the cropped airfoil  140 . For example, the feedback system  350  may include one or more feedback devices  352 , such as cameras, measurement gages, or the like, positioned about the electrode assembly  302  to provide feedback as to the position of the repair component electrode  304  with respect to the cropped airfoil electrode  306 . 
     Further, in at least some embodiments, positioning the airfoil repair component  200  with respect to the cropped airfoil  140  comprises manipulating an alignment assembly  346 , such as an independent axis degree-of-freedom manipulator, to reposition the airfoil repair component  200  and/or the cropped airfoil  140  along one axes, e.g., defined by the cropped airfoil  140 . For instance, the alignment assembly  346  may comprise three rotatable knobs, e.g., a first knob  348   a , a second knob  348   b , and a third knob  348   c , where each knob  348   a ,  348   b ,  348   c  adjusts or manipulates the position of the repair component electrode  304  with respect to the cropped airfoil electrode  306  along one degree-of-freedom. 
     As further illustrated in  FIG.  15   , the method  1500  may comprise ( 1512 ) conducting a joining process to join the airfoil repair component  200  to the cropped airfoil  140 , thereby replacing the damaged portion  130  removed from the airfoil  100  with the airfoil repair component  200 . In at least some embodiments, the joining process comprises passing current through the cropped airfoil electrode  306  and the repair component electrode  304  to attach the airfoil repair component  200  to the cropped airfoil  140  and form a repaired airfoil. For example, passing current through the cropped airfoil electrode  306  and the repair component electrode  304  comprises welding the airfoil repair component  200  to the cropped airfoil  140  through solid state resistance welding. In other embodiments, other suitable methods for joining the airfoil repair component  200  to the cropped airfoil  140  may be used. 
     Further, for embodiments utilizing current to join the airfoil repair component  200  to the cropped airfoil  140 , the airfoil repair system  300  may incorporate adaptive current control to improve yield. For instance, the airfoil repair system  300  may utilize weld luminescence and/or thermal imaging and a controller or the like to analyze and adjust the supplied current, e.g., to match the weld uniformity to a predetermined weld uniformity. The current may be adjusted, e.g., through manipulation of a pulsing sequence. By adjusting the weld during the joining process, increased yield or repair success may be achieved. 
     Additionally, or alternatively, the airfoil repair system  300  may utilize a variety of power sources. For example, for a resistance welding joining process (such as solid state resistance welding), the airfoil repair system  300  may utilize single-phase alternating current (AC), primary and secondary rectified direct current (DC), capacitive discharge (CD), or medium frequency DC (MFDC). MFDC, for instance, may allow finer current control, faster rise time, and a smaller footprint than AC and DC power sources. However, AC, DC, and CD power may provide advantages over MFDC for some applications of the airfoil repair system  300 . 
     Referring still to  FIG.  15   , the method  1500  also may comprise ( 1514 ) obtaining a net shape finished part from the repaired airfoil  100 . For example, the method  1500  may include post-joining processing to achieve the net shape of the original airfoil  100  from the repaired airfoil  100 . For instance, after joining the airfoil repair component  200  to the cropped airfoil  140 , the repaired airfoil  100 , including the airfoil repair component  200 , may be machined (e.g., milled or the like) to obtain the net shape of the original airfoil  100 . As described herein, the airfoil repair component  200  may be locally oversized, e.g., in the region of the repair attachment section  242 , or wholly oversized (i.e., the entire airfoil repair component  200  is oversized), such that at least a portion of the airfoil repair component  200  does not have the net shape of the airfoil  100 . It will be appreciated that the term “oversized” refers to additional material of the airfoil repair component  200  that may provide increased margin or tolerance for alignment between the cropped airfoil  140  and the airfoil repair component  200  such that the two components do not have to be precisely aligned. For instance, the extra material of the oversized airfoil repair component  200  allows misalignment between the airfoil repair component  200  and the cropped airfoil  140  to be corrected through finish machining, e.g., the repair pressure side  202  or repair suction side  204  may be machined more or less than the other of the repair pressure side  202  and repair suction side  204  to compensate for widthwise misalignment. As another example, rather than machining after joining, the repaired airfoil  100  may undergo other post-joining processing, such as cold working or other deformation processing, to transform a non-conforming airfoil to a net shape part. In such embodiments, the repaired airfoil  100  may be largely the desired shape post-joining but may require some cold-working to shape the airfoil  100  within desired limits. 
     The airfoil repair component  200  may be oversized at least in the vicinity of where the airfoil repair component  200  is joined to the cropped airfoil  140 , such that at least a portion of the oversized section of the airfoil repair component  200  may be consumed in the joining process. After joining the airfoil repair component  200  and the cropped airfoil  140 , the portions of the airfoil repair component  200  that remain oversized may be machined to define the desired shape of the airfoil  100 . As described herein, the airfoil repair component  200  for an individual airfoil  100  (having a platform and dovetail, e.g., as shown in  FIG.  1   ) may be locally oversized while the airfoil repair component  200  for an airfoil  100  of a blisk  122  may be oversized all over, e.g., to minimize the risk of damaging the entire blisk  122  during repair of one blisk airfoil. Of course, in some embodiments, the airfoil repair component  200  for an individual airfoil  100  may be wholly oversized while the airfoil repair component  200  for an airfoil  100  of a blisk  122  may be locally oversized. 
     Various features of the airfoil repair component  200  and/or airfoil repair system  300  may be described or shown herein with respect to either an individual airfoil or a blisk airfoil. However, it will be appreciated that at least certain features of the airfoil repair component  200  and/or airfoil repair system  300  may apply to both configurations although shown and/or described herein with respect to only one configuration. Additionally, it will be understood that the various features of the airfoil repair component  200  and/or airfoil repair system  300  may be utilized in additional and/or alternative combinations than those shown and described herein. 
     Further, it will be appreciated that, although described above with respect to airfoil repairs, the present subject matter also could be used with respect to initial or new build parts. For example, the airfoil repair component  200  could, instead, be referred to as an airfoil component  200 , which is joined to a cropped or base airfoil  140  to form a whole or complete airfoil  100 . The airfoil component  200  can be formed as described herein as airfoil repair component  200 , e.g., the airfoil component  200  can have a flared attachment section  242  or a body  205  that is overall oversized, and the airfoil component  200  has a component pressure side  202  opposite a component suction side  204  (or a component first side and a component second side) that each extend axially between a component leading edge  210  and a component trailing edge  212  (or a component first edge and a component second edge). For instance, the attachment section  242  attaches the airfoil component  200  to the cropped or base airfoil  140  and is oversized with respect to a cropped airfoil attachment section  142  such that the attachment section  242  has a component chord length c r  longer than a cropped chord length c c  of the cropped airfoil attachment section  142  and a component width w r  wider than a cropped width w c  of the cropped airfoil attachment section  142 . Further, the airfoil component  200  can be received in an electrode like the repair component electrode  304 , which may be referred to as an airfoil component electrode  304 , and be positioned with the cropped or base airfoil  140  in its cropped airfoil electrode  306  using a tooling assembly  344  as described herein. Joining an airfoil component  200  to a cropped or base airfoil  140  may be useful, e.g., for some configurations of a blisk  122 , where certain size airfoils  100  may be easier to manufacture as a blisk  122  using the joining techniques and features described herein. 
     Accordingly, as described herein, the present subject matter provides methods and apparatus for repairing airfoils. For instance, the present subject matter provides airfoil repair components for replacing damaged portions of airfoils, where the airfoil repair components may be oversized, morphed, and/or have an extended sacrificial tip. For example, a locally or wholly oversized airfoil repair component improves the chances of proper alignment between the airfoil repair component and a cropped airfoil (i.e., an airfoil with a damaged portion removed), with extra cleanup stock for post-joining processing to achieve net shape. Further, the present subject matter provides methods and apparatus for securing an airfoil repair component and/or a cropped airfoil within an electrode to eliminate over constraint and permit more accurate positioning of the airfoil repair component and/or cropped airfoil. For example, the present subject matter eliminates hand tools in loading and unloading components from their respective electrodes by using spring loaded design features and other easily hand-manipulated design features. Moreover, the present subject matter provides adaptive current control, e.g., using weld luminescence or thermal imaging feedback; integral bi-alloy inserts and inert gas shielding, e.g., for solid state resistance welding of reactive materials such as titanium alloys; alignment tooling, such as cameras, etc., for better and/or faster alignment of the airfoil repair component to the cropped airfoil; and compact stabilization tooling to permit easier post-joining extraction of the repaired airfoil. Other advantages of the subject matter described herein also may be realized by those of ordinary skill in the art. 
     Further aspects of the present disclosure are provided by the subject matter of the following clauses: 
     An airfoil component for attaching to a cropped airfoil, the cropped airfoil comprising a cropped airfoil attachment section and a cropped first side opposite a cropped second side, the cropped first side and the cropped second side each extending axially between a cropped first edge and a cropped second edge to define a cropped chord length, the airfoil component comprising a body having a component first side opposite a component second side, the body defining an attachment section for attaching the airfoil component to the cropped airfoil at the cropped airfoil attachment section, the attachment section extending axially between a component first edge and a component second edge to define a component chord length, wherein the attachment section is oversized with respect to the cropped airfoil attachment section such that the component chord length is longer than the cropped chord length. 
     The airfoil component of any preceding clause, wherein a cropped width is defined between the cropped first side and the cropped second side, wherein a component width is defined between the component first side and the component second side, and wherein the component width at the attachment section is wider than the cropped width at the cropped airfoil attachment section. 
     The airfoil component of any preceding clause, wherein the body outside of the attachment section has a body chord length longer than the cropped chord length of the cropped airfoil attachment section and a body width wider than the cropped width of the cropped airfoil attachment section. 
     The airfoil component of any preceding clause, wherein the repair attachment section defines a repair joining face and the cropped airfoil attachment section defines a cropped joining face, and wherein the repair joining face interfaces with the cropped joining face. 
     The airfoil component of any preceding clause, wherein the repair joining face and the cropped joining face interface in a planar interaction. 
     An airfoil repair system comprising a cropped airfoil comprising a cropped airfoil attachment section and a cropped first side opposite a cropped second side, the cropped first side and the cropped second side each extending axially between a cropped first edge and a cropped second edge to define a cropped chord length; an airfoil repair component comprising a body having a repair first side opposite a repair second side, the body defining a repair attachment section for attaching the airfoil repair component to the cropped airfoil at the cropped airfoil attachment section, the repair attachment section extending axially between a repair first edge and a repair second edge to define a repair chord length, the repair attachment section being oversized with respect to the cropped airfoil attachment section such that the repair chord length is longer than the cropped chord length; a repair component electrode for receipt of the airfoil repair component, the repair component electrode comprising a repair component electrode insert removable with respect to a repair component electrode body, the repair component electrode insert surrounding at least a portion of the airfoil repair component; and a tooling assembly for positioning the airfoil repair component with respect to the cropped airfoil. 
     The airfoil repair system of any preceding clause, wherein the repair component electrode insert defines an inert gas manifold for receipt of an inert gas and a plurality of grooves extending from the inert gas manifold along the repair component electrode insert. 
     The airfoil repair system of any preceding clause, wherein the repair component electrode insert comprises a first half and a second half, each of the first half and the second half defining a portion of an inert gas manifold for receipt of an inert gas and each of the first half and the second half defining a plurality of grooves extending from the inert gas manifold along the respective half of the repair component electrode insert. 
     The airfoil repair system of any preceding clause, further comprising a cropped airfoil electrode for receipt of the cropped airfoil, wherein the cropped airfoil electrode comprises a dovetail block, a cropped airfoil electrode body, and a retention assembly, wherein the cropped airfoil comprises a dovetail receivable within the dovetail block, and wherein the dovetail block is removably secured to the cropped airfoil electrode body by one-handed manipulation of the retention assembly. 
     The airfoil repair system of any preceding clause, wherein the repair component electrode body defines a plurality of serrations, each serration having a change in direction. 
     The airfoil repair system of any preceding clause, wherein a blisk comprises the cropped airfoil, and wherein the tooling assembly comprises a cropped airfoil portion for positioning the airfoil repair component with respect to the blisk. 
     The airfoil repair system of any preceding clause, wherein the tooling assembly comprises a feedback system including at least one feedback device located to determine at least one of a size and a position of the airfoil repair component with respect to the cropped airfoil. 
     The airfoil repair system of any preceding clause, wherein the tooling assembly comprises an alignment assembly, wherein the alignment assembly is configured to adjust the position of the airfoil repair component with respect to the cropped airfoil along one or more independent axes defined by the cropped airfoil. 
     The airfoil repair system of any preceding clause, wherein the repair component electrode comprises a point constraint, a line constraint, and a planar restraint with respect to the airfoil repair component, and wherein the point constraint is configured to be manipulated to release the airfoil repair component for removal from the repair component electrode. 
     A method of airfoil repair comprising removing a damaged portion of an original airfoil to form a cropped airfoil, wherein the cropped airfoil comprises a cropped airfoil attachment section and a cropped first side opposite a cropped second side, the cropped first side and the cropped second side each extending axially between a cropped first edge and a cropped second edge to define a cropped chord length; disposing the cropped airfoil in a cropped airfoil electrode; disposing an airfoil repair component within a repair component electrode, the repair component electrode comprising a repair component electrode insert removably received within a repair component electrode body, wherein the airfoil repair component comprises a body having a repair first side opposite a repair second side, the body defining a repair attachment section for attaching the airfoil repair component to the cropped airfoil at the cropped airfoil attachment section, the repair attachment section extending axially between a repair first edge and a repair second edge to define a repair chord length, the repair attachment section being oversized with respect to the cropped airfoil attachment section such that the repair chord length is longer than the cropped chord length; positioning the airfoil repair component with respect to the cropped airfoil; and passing current through the cropped airfoil electrode and the repair component electrode to attach the airfoil repair component to the cropped airfoil and form a repaired airfoil. 
     The method of any preceding clause, further comprising coining the cropped airfoil to remove a twist from the cropped airfoil. 
     The method of any preceding clause, wherein positioning the airfoil repair component with respect to the cropped airfoil comprises locating the repair component electrode through a feedback system to ascertain at least one of a size and a position of the airfoil repair component with respect to the cropped airfoil. 
     The method of any preceding clause, wherein positioning the airfoil repair component with respect to the cropped airfoil comprises manipulating an alignment assembly to reposition the airfoil repair component along at least one independent axis defined by the cropped airfoil. 
     The method of any preceding clause, wherein passing current through the cropped airfoil electrode and the repair component electrode comprises welding the airfoil repair component to the cropped airfoil through solid state resistance welding. 
     The method of any preceding clause, further comprising post-joining processing the repaired airfoil to obtain the net shape of the original airfoil. 
     The method of any preceding clause, where post-joining processing comprises machining the repaired airfoil. 
     The method of any preceding clause, wherein post-joining processing comprises deformation processing the repaired airfoil. 
     The method of any preceding clause, wherein deformation processing the repaired airfoil comprises cold working the repaired airfoil. 
     An airfoil repair system comprising a repair component electrode for receipt of an airfoil repair component, the repair component electrode comprising a repair component electrode insert removable with respect to a repair component electrode body, the repair component electrode insert surrounding at least a portion of the airfoil repair component; and a tooling assembly for positioning the airfoil repair component with respect to a cropped airfoil. 
     The airfoil repair system of any preceding clause, wherein the cropped airfoil is an airfoil from which a damaged portion has been removed. 
     The airfoil repair system of any preceding clause, wherein the cropped airfoil comprises a dovetail configured to be received within a complementarily shaped dovetail slot in a rotor disk. 
     The airfoil repair system of any preceding clause, wherein the cropped airfoil is integrally formed with a rotor disk as part of a blisk. 
     The airfoil repair system of any preceding clause, further comprising a cropped airfoil electrode for receipt of the cropped airfoil. 
     The airfoil repair system of any preceding clause, wherein the tooling assembly is configured to position the airfoil repair component received within the repair component electrode adjacent to the cropped airfoil received within the cropped airfoil electrode for a joining processing to attached the airfoil repair component to the cropped airfoil. 
     The airfoil repair system of any preceding clause, wherein the tooling assembly comprises a feedback system including at least one feedback device. 
     The airfoil repair system of any preceding clause, wherein the feedback device comprises at least one camera. 
     The airfoil repair system of any preceding clause, wherein the feedback device comprises at least one measurement gage. 
     A method of repairing an airfoil comprising disposing a cropped airfoil in a cropped airfoil electrode; disposing an airfoil repair component within a repair component electrode, the repair component electrode comprising a repair component electrode insert removably received within a repair component electrode body; positioning the airfoil repair component with respect to the cropped airfoil; and conducting a joining process to attach the airfoil repair component to the cropped airfoil and form an airfoil. 
     The method of any preceding clause, further comprising removing a damaged portion of the airfoil to form the cropped airfoil. 
     The method of any preceding clause, wherein conducting a joining process comprises passing a current through the cropped airfoil electrode and the repair component electrode. 
     The method of any preceding clause, wherein passing the current through the cropped airfoil electrode and the repair component electrode includes solid state resistance welding the airfoil repair component received in the repair component electrode to the cropped airfoil received in the cropped airfoil electrode. 
     The method of any preceding clause, further comprising obtaining a net shape of the airfoil. 
     The method of any preceding clause, wherein obtaining the net shape of the airfoil comprises machining the airfoil. 
     The method of any preceding clause, wherein obtaining the net shape of the airfoil comprises deformation processing the airfoil. 
     This written description uses examples to disclose the present subject matter, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the present disclosure is defined by the claims and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.