Method of repairing airfoils with tip cooling channels

Abstract

A method of repairing an airfoil of a turbine component is provided. The airfoil includes a tip rail at least partially defining a plurality of tip cooling channels. The turbine component has undergone at least one operating cycle such that a tip portion of the tip rail is outside of design specifications. The method includes removing the tip portion of the tip rail such that a workpiece interface is defined at a radially outer end of the airfoil. After removing the tip portion, at least one tip cooling channel of the plurality of tip cooling channels extends to an opening on the workpiece interface. The method also includes additively manufacturing an extended section on the workpiece interface. The method also includes machining the extension section to form a replacement tip portion of the tip rail within the design specification range.

Description

Technical Field

[0001] The present disclosure generally relates to a method of repairing an airfoil of a turbine component. More specifically, the present disclosure relates to a method of repairing an airfoil of a turbine component having a tip cooling passage. Background Art

[0002] Turbines are used for energy transfer purposes in various industries and applications. For example, a gas turbine engine typically includes a compressor section, a combustion section, a turbine section, and an exhaust section. The compressor section gradually increases the pressure of the working fluid entering the gas turbine engine, and supplies the compressed working fluid to the combustion section. The compressed working fluid and fuel (e.g., natural gas) are mixed in the combustion section and burned in the combustion chamber to generate high-pressure and high-temperature combustion gases. The combustion gases flow from the combustion section into the turbine section, where they expand around the turbine components to do work. For example, the expansion of the combustion gases in the turbine section can rotate a rotor shaft connected to, for example, a generator to generate electricity. The combustion gases then leave the gas turbine via the exhaust section.

[0003] Turbine blades are surrounded by hot combustion gases and therefore require effective cooling to extend the service life of the turbine blades. Turbine blade airfoils are hollow and are arranged in fluid communication with the compressor so that pressurized air can be bled from the compressor and used to cool the airfoil. Airfoil cooling is quite complex and can be achieved using various forms of internal cooling passages and features as well as cooling holes through the wall of the airfoil to discharge cooling air.

[0004] The blade tip is particularly difficult to cool because it is located directly adjacent to the turbine shroud and the hot combustion gases flowing through the tip gap. Therefore, a portion of the air directed inside the blade is typically exhausted through the tip for cooling. The tip typically includes a continuous radially outwardly projecting edge rib formed coextensively between the leading edge and the trailing edge along the pressure side and the suction side. The edge rib follows the aerodynamic profile around the blade and is a significant contributor to the aerodynamic efficiency of the blade.

[0005] The edges of other types of rotor tips sometimes require repair after the turbine has been in service for some time due to the effects of corrosion or high temperature oxidation. The repair process typically involves adding material to the tip and then machining the tip back to meet the specifications of the turbine blade. However, due to the intensity of the welding heat around the tip cooling passages, known repair methods often result in cracks around this area. In addition, when the cooling holes are reopened and the drill or laser strikes the rear wall of the cooling passage, the known repair methods often result in destructive back strikes.

[0006] In view of these factors, it is apparent that new processes for repairing the tips of turbine blades would be favored in the art. Summary of the invention

[0007] Various aspects and advantages of methods according to the present disclosure will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the technology.

[0008] According to one embodiment, a method for repairing an airfoil of a turbine component is provided. The airfoil includes a tip rail that at least partially defines a plurality of tip cooling channels. The turbine component has undergone at least one operating cycle such that a tip portion of the tip rail is outside of a design specification range. The method includes removing the tip portion of the tip rail such that a workpiece interface is defined at a radially outer end of the airfoil. After removing the tip portion, at least one of the plurality of tip cooling channels extends to an opening at the workpiece interface. The method also includes additively manufacturing an extension section at the workpiece interface. The method also includes machining the extension section to form a replacement tip portion of the tip rail that is within the design specification range.

[0009] According to another embodiment, a method for repairing an airfoil of a turbine component is provided. The airfoil includes a tip rail that at least partially defines a plurality of tip cooling channels. The turbine component has undergone at least one operating cycle such that a tip portion of the tip rail is outside of a design specification range. The method includes removing the tip portion of the tip rail such that a workpiece interface is defined at a radially outer end of the airfoil. After removing the tip portion, at least one of the plurality of tip cooling channels extends to an opening on the workpiece interface. The method also includes additively manufacturing an extension segment on and across the opening at the workpiece interface. The method also includes machining the extension segment to form a replacement tip portion of the tip rail within the design specification range. The method also includes reopening at least one of the plurality of tip cooling channels.

[0010] These and other features, aspects and advantages of the inventive method will become better understood with reference to the following description and appended claims.The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the inventive technology and, together with the description, serve to explain the principles of the inventive technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] This specification sets forth a complete and enabling disclosure of the methods of the present invention, including the best modes for making and using the systems and methods of the present invention, for one of ordinary skill in the art, with reference to the accompanying drawings, wherein:

[0012] Figure 1is a schematic diagram of a turbine according to an embodiment of the present disclosure;

[0013] Figure 2 illustrates a perspective view of a turbine component according to an exemplary aspect of the present disclosure;

[0014] Figure 3 illustrates an enlarged view of an airfoil of a turbine component according to various aspects of the present disclosure;

[0015] Figure 4 illustrates an enlarged view of an airfoil of a turbine component according to various aspects of the present disclosure;

[0016] Figure 5 The first stage of the repair process according to the embodiment of the present disclosure is illustrated. Figure 3 A schematic cross-sectional view of the airfoil taken along line CC is shown;

[0017] Figure 6 The second stage of the repair process according to the embodiment of the present disclosure is illustrated. Figure 3 A schematic cross-sectional view of the airfoil taken along line CC is shown;

[0018] Figure 7 The third stage of the repair process according to the embodiment of the present disclosure is illustrated. Figure 3 A schematic cross-sectional view of the airfoil taken along line CC is shown;

[0019] Figure 8 The fourth stage of the repair process according to the embodiment of the present disclosure is illustrated. Figure 3 A schematic cross-sectional view of the airfoil taken along line CC is shown;

[0020] Fig. 9 illustrates a schematic diagram of an exemplary additive manufacturing system according to exemplary aspects of the present disclosure;

[0021] Fig.10 Depicts a digital representation of a field of view according to an exemplary aspect of the present disclosure, which may be represented by Fig. 9 The additive manufacturing system’s vision system is used to capture;

[0022] Fig.11 A flow chart illustrating a method of repairing an airfoil of a turbine component according to an embodiment of the present disclosure;

[0023] Fig.12 A flow chart illustrating a method of repairing an airfoil of a turbine component according to an embodiment of the present disclosure; and

[0024] Fig.13 A block diagram of a computing system according to an exemplary aspect of the present disclosure is illustrated, which computing system may be incorporated into Fig. 9 in additive manufacturing systems. DETAILED DESCRIPTION

[0025] Reference will now be made in detail to the embodiments of the inventive method, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the inventive technology, rather than as a limitation to the inventive technology. In fact, it will be apparent to those skilled in the art that modifications and variations may be made in the inventive technology without departing from the scope or essence of the inventive technology as protected by the claims. For example, a feature illustrated or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, the present disclosure is intended to encompass these modifications and variations that fall within the scope of the appended claims and their equivalents.

[0026] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. In addition, unless otherwise specifically stated, all embodiments described herein should be considered exemplary.

[0027] The detailed description uses numbers and letter names to refer to the features in the drawings. Similar or similar names in the drawings and description have been used to refer to similar or similar parts of the present invention. As used herein, the terms "first", "second", and "third" may be used interchangeably to distinguish one component from another, and are not intended to indicate the position or importance of the various components.

[0028] The term "fluid" may be a gas or a liquid. The term "fluid communication" means that two or more regions defining a flow channel are joined to each other so that a fluid can form a connection (ie flow) between the designated regions.

[0029] As used herein, the terms "upstream" (or "upward") and "downstream" (or "downward") refer to relative directions with respect to the flow of a fluid in a fluid passage. For example, "upstream" refers to the direction from which the fluid is flowing, and "downstream" refers to the direction toward which the fluid is flowing. In the context of an exhaust diffuser assembly, "upstream" refers to the direction closest to the turbine segment, and "downstream" refers to the outlet end of the exhaust diffuser assembly.

[0030] The term "radially" refers to relative directions that are substantially perpendicular to the axial centerline of a particular component; the term "axially" refers to relative directions that are substantially parallel and / or coaxially aligned with the axial centerline of a particular component; and the term "circumferentially" refers to relative directions that extend around the axial centerline of a particular component.

[0031] Terms with approximate meanings (such as "about", "approximately", "substantially" and "substantially") are not limited to the exact values ​​specified. In at least some cases, approximate language may correspond to the accuracy of an instrument used to measure a value, or the accuracy of a method or machine used to construct or manufacture a component and / or system. In at least some cases, approximate language may correspond to the accuracy of an instrument used to measure a value, or the accuracy of a method or machine used to construct or manufacture a component and / or system. For example, approximate language may refer to a tolerance of 1%, 2%, 4%, 5%, 10%, 15% or 20% in an individual value, a range of values, and / or an end value of a range of defined values. When used in the context of an angle or direction, such terms are included within ten degrees greater than or less than the angle or direction. For example, "substantially vertical" includes directions within ten degrees of vertical in any direction (e.g., clockwise or counterclockwise).

[0032] Unless otherwise indicated herein, the terms "coupled," "fixed," "attached to," and the like refer to both direct coupling, fixing, or attachment, as well as indirect coupling, fixing, or attachment through one or more intermediate components or features. The terms "directly coupled," "directly fixed," "directly attached to," and the like mean that two components are engaged in contact with one another and there are no intermediate components or features present.

[0033] As used herein, the terms "includes," "comprising," "having," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that includes a list of features is not necessarily limited to only those features but may include other features not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, unless expressly specified otherwise, "and / or" refers to a condition that is satisfied by any of the following: A is true (or present) and B is false (or absent); A is false (or absent) and B is true (or present); and both A and B are true (or present).

[0034] Here and throughout the specification and claims, where range limitations are combined and interchanged, such ranges are identified and include all 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.

[0035] Now referring to the accompanying drawings, Figure 1 A schematic diagram of one embodiment of a turbomachine is illustrated, which in the illustrated embodiment is a gas turbine engine 10. Although an industrial or land-based gas turbine engine is shown and described herein, the present disclosure is not limited to industrial and / or land-based gas turbine engines unless otherwise indicated in the claims. For example, the present invention as described herein may be used for any type of turbomachine, including but not limited to a steam turbine, an aircraft gas turbine, or a marine gas turbine.

[0036] As shown, the gas turbine engine 10 generally includes a compressor section 12. The compressor section 12 includes a compressor 14. The compressor section 12 includes an inlet 16 disposed at the upstream end of the gas turbine engine 10. The gas turbine engine 10 also includes a combustion section 18 having one or more combustors 20 disposed downstream of the compressor section 12. The gas turbine engine 10 also includes a turbine section 22 located downstream of the combustion section 18. A shaft 24 generally extends axially through the gas turbine engine 10.

[0037] The compressor segment 12 may generally include a plurality of rotor disks 21 and a plurality of rotor blades 23 extending radially outward from each rotor disk 21 and connected to each rotor disk. Each rotor disk 21 may in turn be coupled to or form an upstream portion of a shaft 24 extending through the compressor segment 12. The rotor blades 23 of the compressor segment 12 may include a turbine airfoil defining an airfoil shape (e.g., having a leading edge, a trailing edge, and a sidewall extending between the leading edge and the trailing edge). In addition, the compressor segment 12 includes stator vanes disposed between the rotor blades to define a series of compression stages. The stator vanes may extend from and be coupled to the compressor housing.

[0038] The turbine segment 22 may generally include a plurality of rotor disks 27 and a plurality of rotor blades 28 extending radially outward from each rotor disk 27 and interconnected to each rotor disk. Each rotor disk 27, in turn, may be coupled to or form a portion of a shaft 24 extending through the turbine segment 22. The turbine segment 22 also includes an outer casing 32 that circumferentially surrounds a downstream portion of the shaft 24 and the rotor blades 28. The turbine segment 22 may include a fixed nozzle 26 extending radially inward from the outer casing 32. The rotor blades 28 and the fixed nozzles 26 may be arranged in an alternating manner along the axial centerline 30 of the gas turbine 10. Both the rotor blades 28 and the fixed nozzles 26 may include a turbine airfoil defining an airfoil shape (e.g., having a leading edge, a trailing edge, and a sidewall extending between the leading edge and the trailing edge).

[0039] In operation, ambient air 36 or other working fluid is drawn into the inlet 16 of the compressor 14 and is gradually compressed to provide compressed air 38 to the combustion section 18. The compressed air 38 flows into the combustion section 18 and mixes with the fuel to form a combustible mixture. The combustible mixture is burned in the combustion chamber 40 of the combustor 20, thereby generating combustion gases 42 that flow from the combustion chamber 40 into the turbine section 22. Energy (kinetic energy and / or thermal energy) is transferred from the combustion gases 42 to the rotor blades 28, causing the shaft 24 to rotate and produce mechanical work. The combustion gases 42 leave the turbine section 22 and flow through the exhaust diffuser 34 across a plurality of struts 44 disposed within the exhaust diffuser 34.

[0040] The gas turbine engine 10 may define a cylindrical coordinate system having an axial direction A extending along the axial centerline 30 , a radial direction R perpendicular to the axial centerline 30 , and a circumferential direction C extending about the axial centerline 30 .

[0041] See now Figure 2 , illustrates a perspective view of a turbine component 100 according to an exemplary aspect of the present disclosure, wherein a portion of the pressure side wall 108 has been cut away to show the internal cooling passage 120. In an exemplary embodiment, the turbine component 100 may be a turbine blade. However, in other embodiments, the turbine component may be a turbine guide vane and / or a turbine nozzle. The turbine component 100 may be similar to the turbine component 100 described above with reference to FIG. Figure 1 The turbine section 22 of the gas turbine 10 is configured to be a rotor blade 28. As shown in the figure, the turbine component 100 includes a platform 102 disposed at a junction of an airfoil 104 and a dovetail 106, the platform being used to define a portion of a radial inner flow path of the combustion gas.

[0042] The airfoil 104 may include a generally concave pressure sidewall 108 and an opposing generally convex suction sidewall 110. The pressure sidewall 108 and the suction sidewall 110 may each extend between a leading edge 112 and a trailing edge 114. Additionally, the pressure sidewall 108 and the suction sidewall 110 each extend radially (e.g., in a radial direction R) from a root 116 at the platform 102 to a tip 118. The airfoil 104 may terminate radially at the tip 118. In this manner, the airfoil 104 may not include a tip shroud extending from the tip 118.

[0043] According to an exemplary aspect of the present disclosure, the airfoil 104 may include a tip rail or edge rail 122 extending radially outward from the pressure side wall 108 and the suction side wall 110. The tip rail 122 may define a tip cavity 124, which may be shaped similarly to the airfoil 104. Specifically, the tip cavity 124 may be defined by the tip rail 122 and a bottom plate 126. The bottom plate 126 may be radially inward of the tip 118. The tip rail 122 may extend radially outward from the bottom plate 126 to the tip 118.

[0044] In many embodiments, tip rail 122 can include a pressure side portion 128 and a suction side portion 130. Pressure side portion 128 can extend radially outward from pressure side 108, and suction side portion 130 can extend radially outward from suction side 110.

[0045] An internal cooling passage 120 may be defined within the airfoil 104, for example, between the pressure sidewall 108 and the suction sidewall 110. The cooling air supplied to the internal cooling passage 120 may be bled from the compressor segment 12 in any conventional manner. The interior of the airfoil 104 may have any configuration, including, for example, a spiral flow passage with various spoilers formed therein for improving cooling air efficiency. The cooling air from the internal cooling passage 120 may be discharged through film cooling holes 132 defined in the sidewalls 108, 110 and / or trailing edge exhaust holes 134 defined in the trailing edge 114. Additionally, one or more tip cooling passages 136 may be at least partially defined in the tip rail 122, such as in the pressure side portion 128 and / or the suction side portion 130.

[0046] In many embodiments, as shown, the tip rail 122 can define a tip shelf 138, which can include a bottom plate 140. The tip shelf can be a recess defined in the pressure side portion 128 of the tip rail 122. The bottom plate 140 can be generally perpendicular to the radial direction R. The bottom plate 140 can define a plurality of shelf outlets 142 that exhaust cooling air from the interior cooling channel 120 in the radial direction R.

[0047] See now Figure 3 and Figure 4 , each of which illustrates an enlarged view of an airfoil 104 according to various aspects of the present disclosure. As shown, tip cooling passages 136 may be defined on the tip rail 122 in the pressure side portion 128 and / or in the suction side portion 130. In addition, the tip cooling passages 136 may be equally spaced apart. The tip cooling passages 136 may each be disposed at substantially the same radial height (or span length) of the airfoil 104, such that each tip cooling passage 136 is disposed within about 0% to about 5% of a common radial height (or span length) of the airfoil 104.

[0048] Additionally, as shown, each of the tip cooling channels 136 may be elongated in the radial direction R such that the longest dimension of each of the tip cooling channels 136 is substantially parallel to the radial direction R. Specifically, each of the tip cooling channels 136 may be shaped as an ellipse, although other shapes are possible and within the scope of the present disclosure.

[0049] When in operation, the airfoil 104 (including the tip rail 122) may be exposed to high temperature combustion gases, operational vibrations, and mechanical forces that cause the airfoil 104 to fall outside of the design specifications. Specifically, the tip rail 122 may lose material and / or warp over time due to operation and exposure to combustion gases, thereby causing the tip rail 122 to fall outside of the design specifications (in which peak efficiency occurs). The lost and / or warped material can be removed and rebuilt using an additive manufacturing process. As will be discussed in further detail below, the process includes machining the tip rail 122 to a machining stop line 158 so that a portion of the tip cooling channel 136 is exposed; adding new material using an additive manufacturing system; and machining the new material to bring the tip rail back within the design specifications.

[0050] See now Figures 5 to 8 , each of which illustrates an embodiment according to the present disclosure Figure 3 Schematic cross-sectional view of the airfoil 104 taken along line CC shown. Specifically, Figures 5 to 8 Each illustrates a cross-sectional view of the airfoil 104 at various steps of the repair process. Figures 5 to 8 As shown, the airfoil 104 may include a pressure side wall 108 and a suction side wall 110. The airfoil 104 may include a tip rail 122 having a pressure side portion 128 extending (e.g., radially) from the pressure side wall 108 and a suction side portion 130 extending (e.g., radially) from the suction side wall 110. The tip rail 122 and a cap 125 (which defines a bottom plate 126) may define a tip cavity 124.

[0051] An internal cooling passage 120 may be defined within the airfoil 104 (e.g., between the pressure sidewall 108, the suction sidewall 110, and the cap 125). A tip cooling passage 136 may extend from the internal cooling passage 120. Specifically, the tip cooling passage 136 may include a counterbore 146 and a through-hole 148. The counterbore 146 may be defined in the tip rail 122, and the through-hole may be defined in both the tip rail 122 and / or the pressure sidewall 108. The through-hole 148 may extend from the internal cooling passage 120 to the counterbore 146, and the counterbore 146 may extend from the through-hole 148 to an outer surface 150 of the airfoil 104 on the pressure side 108. Additionally, the counterbore 146 may extend radially beyond the through-hole 148. The airfoil 104 may include a radially outermost surface 153, and the counterbore 146 may be radially spaced apart from the radially outermost surface 153 (e.g., prior to the repair process). The counterbore 146 may have a larger diameter than the through hole 148. Figures 5 to 8 The tip cooling passages 136 are illustrated as being defined on the pressure side, but it should be understood that the tip cooling passages 136 may also be provided on the suction side.

[0052] Figure 5 A cross-sectional view of the airfoil 104 of the turbine component 100 is illustrated before it has been machined down to remove a possibly worn / warped tip portion 172. In this state, the airfoil 104 may be (such as described above with reference to Figure 1 The gas turbine 10 in question has undergone at least one operating cycle such that the tip portion 172 of the tip rail 122 is worn and / or warped and has fallen outside of a design specification range. The design specification range may correspond to a peak efficiency range for the airfoil 104. That is, the design specification range is the aerodynamic profile and / or shape that extracts the most energy from the combustion gases when implemented in the gas turbine 10. Therefore, the repair method disclosed herein advantageously restores the tip portion 172 of the tip rail 122 of the airfoil 104 to the design specification range by removing the worn / warped material and adding back new material by means of laser deposition and / or additive manufacturing. Figure 5 As shown, the counterbore 146 of the tip cooling passage 136 may define a pre-machined radial height 152. The pre-machined radial height 152 may be defined at an opening 151 of the counterbore 146 on the outer surface 150 of the airfoil 104.

[0053] According to an exemplary implementation of the repair method, the method may include removing the tip portion 172 of the tip rail 122 (e.g., by machining or a subtractive process) such that a portion of the counterbore 146 is removed and the through hole 148 remains (e.g., intact and unmachined). Specifically, the method may include removing the tip portion 172 of the tip rail 122 such that a workpiece interface 220 (or top surface) is defined at the radially outer end of the airfoil 104. Figure 6 As shown, after removing the tip portion 172, at least one tip cooling channel 136 of the plurality of tip cooling channels extends to the opening 170 at the workpiece interface 220 (e.g., at least partially defined by the workpiece interface 220). More specifically, as shown, after removing the tip portion 172, the counterbore 146 may be exposed and may extend to the opening 170 at the workpiece interface 220.

[0054] like Figure 5 As shown, the machining stop line 158 can be set at about half of the pre-machined radial height 152 of the counterbore 146. Figure 3 and Figure 4 1. The machining stop line 158 can be seen in FIG. This line can represent the portion of the tip cooling channel 136 that is removed before further implementing the repair method. Specifically, the radially outer side of the machining stop line 158 can be removed. The machining stop line 158 can form a portion of a machining stop plane, which can be perpendicular to the radial direction R.

[0055] The machining stop line 158 may be set between about 40% and about 60% of the pre-machined radial height 152. In other embodiments, the machining stop line 158 may be set between about 45% and about 55% of the pre-machined radial height 152. In certain embodiments, the machining stop line 158 may be set at about 50% of the pre-machined radial height 152.

[0056] In other words, once the tip portion 172 is removed (e.g., by machining away), a remaining radial height 174 of the counterbore 146 may remain. The remaining radial height 174 may be the radial height of the counterbore 146 at the opening 151. Once the tip portion 172 is removed, the remaining radial height 174 may be between about 40% and about 60% of the pre-machined radial height 152, or such as between about 45% and about 55%, or such as about 50%.

[0057] Figure 6 The airfoil 104 is illustrated after the tip portion 172 of the tip rail 122 (e.g., the portion of the tip rail 122 located radially outward of the machining stop line 158) has been removed. At this stage, the airfoil 104 may define a workpiece interface 220 (or top surface). The workpiece interface 220 may define an opening 170 into which the remaining portion of the counterbore 146 of the tip cooling passage 136 extends. That is, after the worn portion of the tip rail 122 has been removed, the remaining portion of the counterbore 146 may extend radially outward to the opening 170 on the workpiece interface 220.

[0058] like Figure 5 and Figure 6 As shown collectively, the counterbore may include a top segment 176 (or radially outer segment) and a bottom segment 178. The top segment 176 may be located radially outward of the machining stop line 158, and the bottom segment 178 may be located radially inward of the machining stop line 158. The repair method may include removing the tip portion 172 of the tip rail 122 such that the top segment 176 of the counterbore 146 is removed and the bottom segment 178 of the counterbore extends radially to the opening 170 at the workpiece interface 220.

[0059] like Figures 5 to 8 As shown, in some implementations, the airfoil 104 may include a portion of the airfoil 104 that is formed as a result of operation within the gas turbine (e.g., Figure 5 In such embodiments, the repair method may include welding (e.g., manually welding) the defect 180 to produce a weld defect 182 ( Figures 6 to 8 ) and blend the welding defect flush with the tip rail 122 (e.g., flush with the outer surface of the tip rail 122).

[0060] Figure 7 The airfoil 104 is illustrated after having undergone additive manufacturing and / or laser deposition in which new material 160 in the form of an extension 162 has been added to the airfoil 104. The extension 162 may extend across the opening 170. The extension 162 may roughly fit the original shape of the airfoil 104 (e.g., when the airfoil 104 is initially manufactured before being used in a gas turbine), but the extension 162 may require additional post-machining to bring the tip rail 122 back to the design specification range. The extension 162 may be referred to below as Fig. 9 The discussed additive manufacturing system 200 is added to the airfoil 104 at the workpiece interface 220. After additive manufacturing (or printing), the counterbore 146 may define a post-printing height 186 that is substantially equal to the remaining radial height 174. Post-machining (e.g., drilling, boring, or utilizing an electrical discharge machine) may be required to reopen the top section of the counterbore 146.

[0061] Figure 8 The airfoil 104 is illustrated after undergoing post-machining to form a replacement tip portion 184 that is within design specifications. The replacement tip portion 184 may substantially match the profile of the tip portion 172, but may not be worn / warped such that the replacement tip portion 184 is within the design specifications. During post-machining, the new material 160 is partially removed to return the airfoil 104 to the design specifications and / or reopen the counterbore 146. Specifically, the repair method may include reopening the counterbore 146 (e.g., a top segment of the counterbore) by removing a portion of the extension segment 162. The removed portion may correspond to the size / shape of the top segment 176 such that a new top segment 179 of the counterbore 146 is formed within the extension segment 162.

[0062] See now Fig. 9, illustrates an exemplary additive manufacturing system 200 according to exemplary aspects of the present disclosure. As shown, the additive manufacturing system 200 includes a vision system 202, an additive welding machine 204, and a control system 206 operably configured to control the vision system 202 and / or the additive welding machine 204. The vision system 202 and the additive welding machine 204 can be provided as a single integrated unit or as separate stand-alone units. The vision system 202 and the additive welding machine 204 can be operably coupled to each other via a communication interface using wired or wireless communication lines, which can provide a direct connection between the vision system 202 and the additive welding machine 204. The control system 206 may include one or more control systems 206. For example, a single control system 206 may be operably configured to control the operation of the vision system 202 and the additive welding machine 204, or separate control systems 206 may be operably configured to control the vision system 202 and the additive welding machine 204, respectively. The control system 206 may be implemented as part of the vision system 202, as part of the additive welding machine 204, and / or as a stand-alone unit provided separately from the vision system 202 and / or the additive welding machine 204. The control system 206 may be operably coupled to the vision system 202 and / or the additive welding machine 204 via a communication interface using wired or wireless communication links, which may provide a direct connection between the control system 206 and the vision system 202 and / or between the control system 206 and the additive welding machine 204. The exemplary additive manufacturing system 200 may optionally include a user interface 208 and / or a management system 210.

[0063] In some embodiments, the control system 206 can determine the stretch-CAD model, generate one or more print commands based at least in part on the stretch-CAD model, and / or send the one or more print commands to cause the additive welding machine 204 to additively print the stretch based at least in part on the print commands.

[0064] The vision system 202 may include any suitable one or more cameras 212 or other machine vision devices that may be operably configured to obtain image data including digital representations of one or more fields of view 214. Such digital representations may sometimes be referred to as digital images or images; however, it should be understood that the present disclosure may be practiced without presenting such digital representations in a human-viewable form. However, in some embodiments, a human-viewable image corresponding to the field of view 214 may be displayed on the user interface 208 based at least in part on such digital representations of the field of view 214.

[0065] The vision system 202 allows the additive manufacturing system 200 to obtain information about one or more workpieces 216 on which one or more extensions can be additively printed, respectively. Specifically, the vision system 202 allows the one or more workpieces 216 to be positioned and defined so that the additive welding machine 204 can be instructed to print the one or more extensions on the corresponding one or more workpieces 216 with appropriately high accuracy and precision. The one or more workpieces 216 can be fixed to a build plate 218, wherein a workpiece interface (e.g., a top surface) 220 of the corresponding workpiece 216 is aligned with a build plane 222.

[0066] One or more cameras 212 of vision system 202 can be configured to obtain two-dimensional or three-dimensional image data, including a two-dimensional digital representation of field of view 214 and / or a three-dimensional digital representation of field of view 214. Alignment of workpiece interface 220 with build plane 222 allows one or more cameras 212 to obtain higher quality images. For example, one or more cameras 212 can have a focal length that is adjusted or adjustable with respect to build plane 222. With workpiece interface 220 of one or more workpieces 216 aligned with build plane 222, the one or more cameras can easily obtain a digital image of workpiece interface 220. One or more cameras 212 can include a field of view 214 that encompasses all or a portion of one or more workpieces 216 secured to build plate 218.

[0067] The image data obtained by the vision system 202, including the digital representation of the one or more workpieces 216, can be sent to the control system 206. The control system 206 can be configured to determine the workpiece interface 220 of each of the plurality of workpieces 216 from the one or more digital representations of the one or more fields of view 214 that have been captured by the vision system 202, and then determine one or more coordinates of the workpiece interface 220 of the corresponding workpiece in the plurality of workpieces 216. Based on the one or more digital representations, the control system 206 can generate one or more print commands that can be sent to the additive welding machine 204 so that the additive welding machine 204 can additively print a plurality of stretches on a corresponding workpiece in the plurality of workpieces 216. The one or more print commands can be configured to additively print a plurality of stretches, wherein each corresponding stretch of the plurality of stretches is located on the workpiece interface 220 of the corresponding workpiece 216.

[0068] The additive welding machine 204 can utilize any desired additive manufacturing technology. In an exemplary embodiment, the additive welding machine can utilize a powder bed fusion (PBF) technology, such as direct metal laser melting (DMLM), electron beam melting (EBM), selective laser melting (SLM), directional metal laser sintering (DMLS), or selective laser sintering (SLS). In some embodiments, the additive welding machine 204 can utilize a wire feed rod instead of or in addition to a powder bed. Furthermore, in other embodiments, the extension can be completed completely manually using a welding torch and a wire rod, such that the additive manufacturing machine 204 may not be necessary.

[0069] Still see Fig. 9 , the exemplary additive welding machine 204 includes a powder supply chamber 224 and a build chamber 228, the powder supply chamber containing a supply of powder 226. A build plate 218 having one or more workpieces 216 fixed thereto can be positioned in the build chamber 228, wherein the workpieces 216 can be additively printed in a layer-by-layer manner. The powder supply chamber 224 includes a powder piston 230 that raises a powder floor 232 during operation of the system 200. When the powder floor 232 is raised, a portion of the powder 226 is expelled from the powder supply chamber 224.

[0070] Recoater 234 (e.g., a roller or blade) pushes some of powder 226 across work surface 236 and onto build platform 238. Build plate 218 may be secured to build platform 238 using suction cup system 240 in a manner configured to position build plate 218 on build platform 238 and / or within build chamber 228 with sufficient accuracy and precision. Workpiece 216 may be secured to build plate 218 prior to securing build plate 218 to build platform 238. Recoater 234 fills build chamber 228 with powder 226 and then sequentially distributes thin layers of powder 226 across build plane 222 near the top of workpiece 216 to additively print sequential layers of workpiece 216. For example, a thin layer of powder 226 may be about 10 to 100 microns thick, such as about 20 to 80 μm thick, such as about 40 to 60 μm thick, or such as about 20 to 50 μm thick, or such as about 10 to 30 μm thick. Build plane 222 represents a plane corresponding to the next layer of workpiece 216 to be formed from powder 226.

[0071] To form an extended layer (e.g., an intermediate or subsequent layer) on workpiece 216, energy source 242 directs energy beam 244 (such as a laser or electron beam) along build plane 222 onto a thin layer of powder 226 to melt or fuse powder 226 to the top of workpiece 216 (e.g., to melt or fuse the layer to workpiece interface 220 and / or to fuse subsequent layers to the workpiece interface). Scanner 246 controls the path of the beam so as to melt or fuse only the portion of the layer of powder 226 that is to be melted or fused to workpiece 216. Typically, with a DMLM, EBM, or SLM system, powder 226 is completely melted, wherein the corresponding layer is melted or re-melted with a corresponding number of passes of energy beam 244. In contrast, with a DMLS or SLS system, the layer of powder 226 is sintered, thereby substantially fusing the particles of powder 226 to each other without reaching the melting point of powder 226. After the layer of powder 226 is melted or fused to workpiece 216, build piston 248 gradually lowers build platform 238 in increments, thereby defining a next build plane 222 for the next layer of powder 226, and recoater 234 distributes the next layer of powder 226 across build plane 222. Sequential layers of powder 226 can be melted or fused to workpiece 216 in this manner until the additive printing process is completed.

[0072] Fig.10 A digital representation 300 of the field of view 214 including the workpiece interface 220 of the workpiece 216 is depicted. Specifically, Fig.10 A digital representation 300 of the field of view 214 is depicted, wherein the workpiece 216 is a portion of the tip rail 122 of the airfoil 104. The digital representation 300 of the tip rail 122 may be acquired by the vision system 202 after the tip cooling channels 136 have been exposed by removing worn material from the tip rail 122 so that a plurality of the tip cooling channels 136 are visible on the workpiece interface 220 in the digital representation 300. For example, the tip rail 122 may be viewed while the airfoil is in a Figure 6 The illustrated condition allows a digital representation 300 of the airfoil 104 to be obtained when the opening 170 is visible at the workpiece interface 220 .

[0073] The vision system 202 may provide a digital representation 300 of the workpiece interface 220 to the control system 206, which may generate and / or position a plurality of digital markings 302 on the digital representation 300 along the perimeter of the tip rail 122 on the workpiece interface 220. The digital markings 302 may be positioned by the control system 206 in a reproducible manner or manually by a user using the user interface 208. A smooth line may connect each digital marking 302 to form a digital profile 304 of the airfoil 104. The digital markings 302 may provide the control system 206 and / or the additive welding machine 204 with a profile 304 of the airfoil 104 at the workpiece interface 220. Subsequently, the control system 206 may instruct the additive welding machine 204 to add material to the tip rail 122 by powder deposition and / or laser following the profile 304 (e.g., the path of the line connecting the digital markings 302). The digital markings 302 may be positioned on the outer surface 150 of the airfoil 104 on the workpiece profile 220. Specifically, the numerical markers 302 may be positioned between the plurality of openings 170 (i.e., the counterbores 146 of the tip cooling passages 136 that are exposed at the workpiece interface 220 due to the earlier removal of the tip rails 122 during the repair process). The numerical markers 302 may be positioned between two adjacent tip cooling passages 136. Positioning the numerical markers 302 in this manner is advantageous because a more accurate profile 304 of the airfoil 104 may be generated than, for example, if the tip cooling passages 302 were not visible (e.g., if the tip cooling passages were welded shut and therefore not visible, such that the numerical markers 136 could not be positioned relative thereto).

[0074] See now Fig.11 , illustrates a flow chart of one embodiment of a method 1100 for repairing an airfoil of a turbine component according to an embodiment of the present subject matter. In general, reference will be made herein to the above reference Figures 1 to 10 The method 1100 is described with reference to the turbine component 100, airfoil 104, and additive manufacturing system 200. However, one of ordinary skill in the art will appreciate that the disclosed method 1100 may generally be used with any turbine component and / or may be used in conjunction with an additive manufacturing system having any other suitable system configuration. Fig.11 For purposes of illustration and discussion, steps are depicted as being performed in a particular order, but the methods discussed herein are not limited to any particular order or arrangement unless otherwise indicated in the claims. One skilled in the art will appreciate, using the disclosure provided herein, that the various steps of the methods disclosed herein may be omitted, rearranged, combined, and / or adjusted in various ways without departing from the scope of the present disclosure. Dashed boxes indicate optional steps of method 1100.

[0075] like Fig.11As shown, a method for repairing an airfoil may include: at (1102), subjecting an airfoil of a turbine component to a pre-weld heat treatment. This may involve heating the airfoil to a set temperature to relieve stress or remove hydrogen before welding any cracks or defects to ensure better weld quality. In many specific implementations, method 1100 may include: at (1104), performing a pre-weld fluorescent penetrant inspection (FPI) on the airfoil. Pre-weld FPI may reveal defects that are not visible to the naked eye. The method may include preparing the surface by cleaning, applying a fluorescent penetrant, allowing the penetrant to dwell for a period of time, removing excess penetrant, and UV testing. The part is inspected under UV light, which reveals any cracks into which the penetrant has flowed, thereby revealing the defects.

[0076] In an exemplary implementation, method 1100 may include, at (1106), removing a tip portion of the airfoil. This may form a workpiece interface to which a replacement tip may be additively manufactured. Removal at (1106) may be accomplished using any conventional machining process, such as turning, milling, drilling, grinding, boring, broaching, electrical discharge machining (EDM), electron beam machining (EBM), laser cutting, water jet cutting, chemical machining, ultrasonic machining, or other machining processes.

[0077] Prior to step 1106 or after step 1106, method 1100 may include manually welding and flush blending a localized crack (or defect) in the airfoil at (1108). This may include filling any localized defects in the airfoil with the welding material and blending (e.g., grinding, sanding, or other blending techniques). Blending the weld defect flush may ensure that there is no protrusion between the surface of the airfoil and the weld defect.

[0078] In many specific implementations, the method 1100 may also include: at (1110), additively manufacturing an extension segment on the workpiece interface of the airfoil. This may be performed by an additive manufacturing system (such as the one described above with reference to Fig. 9The extension may be roughly matched to the profile of the removed portion of the airfoil, but some final machining / blending may be required to bring the airfoil back within design specifications. Thus, method 1100 may also include, at (1112), machining the extension to form a replacement tip portion. Machining at (1112) may be accomplished using any conventional machining process, such as turning, milling, drilling, grinding, boring, broaching, electrical discharge machining (EDM), electron beam machining (EBM), laser cutting, water jet cutting, chemical machining, ultrasonic machining, or other machining processes. Additionally, method 1100 may include, at (1114), blending the replacement tip portion flush with the airfoil 104, which may ensure that no protrusions exist at the intersection between the replacement tip portion and the airfoil. Blending may include sanding or other techniques.

[0079] In various embodiments, method 1100 may include, at (1116), reopening the tip cooling hole. For example, during the removal step, the tip cooling hole may have been partially removed such that during the additive manufacturing step, the tip cooling hole was covered by the extension. Thus, the tip cooling hole may be reopened by removing a portion of the extension. Removing a portion of the extension may include machining (e.g., drilling or boring) the tip cooling hole. In some embodiments, removing a portion of the extension to reopen the tip cooling hole may include utilizing an EDM process. Subsequently, the method may include, at (1118), checking the cooling hole diameter using a reference pin. For example, this may include inserting a reference pin into the cooling hole to ensure that the cooling hole diameter is within a desired range. Otherwise, the cooling hole may require additional machining. In many embodiments, method 1100 may include, at (1120), post-weld heat treatment. This may involve heating the airfoil to a set temperature to relieve stress. Finally, method 1100 may include, at ( 1122 ), performing a post-weld fluorescent penetrant inspection (FPI) on the airfoil using a similar process as described above with reference to step 1104 .

[0080] See now Fig.12 , illustrates a flow chart of one embodiment of a method 1200 for repairing an airfoil of a turbine component according to an embodiment of the present subject matter. In general, reference will be made herein to the above reference Figures 1 to 10 The method 1200 is described with reference to the turbine component 100, airfoil 104, and additive manufacturing system 200. However, one of ordinary skill in the art will appreciate that the disclosed method 1200 may generally be used with any turbine component and / or may be used in conjunction with an additive manufacturing system having any other suitable system configuration. Fig.12For purposes of illustration and discussion, the steps are depicted as being performed in a particular order, but the methods discussed herein are not limited to any particular order or arrangement unless otherwise indicated in the claims. One skilled in the art will appreciate, using the disclosure provided herein, that the various steps of the methods disclosed herein may be omitted, rearranged, combined, and / or adjusted in various ways without departing from the scope of the present disclosure. Dashed boxes indicate optional steps of method 1200.

[0081] Method 1200 may be used to repair an airfoil of a turbine component. The airfoil may include a tip rail that at least partially defines a plurality of tip cooling passages. The turbine component may have undergone at least one operating cycle such that a tip portion of the tip rail is outside of a design specification range. For example, while in operation, the airfoil (including the tip rail) may be exposed to high temperature combustion gases, operating vibrations, and mechanical forces that cause the tip portion to fall outside of a design specification range. Specifically, the tip portion may lose material and / or warp over time due to operation and exposure to combustion gases, causing the tip portion of the tip rail to fall outside of a design specification range in which peak efficiency occurs.

[0082] Method 1200 may include, at (1202), removing the tip portion of the tip rail such that a workpiece interface is defined at a radially outer end of the airfoil. Thus, after removing the tip portion, at least one of the plurality of tip cooling channels extends to an opening on the workpiece interface (such as all of the tip cooling channels in some implementations, or such as a portion of the tip cooling channels in other implementations). In many implementations, prior to the removal step at (1202), the plurality of tip cooling channels each include a through hole and a counterbore extending from and radially across the through hole. In such implementations, method 1200 may include removing the tip portion of the tip rail such that the counterbore extends radially to an opening on the workpiece interface. In various implementations, method 1200 may include removing the tip portion of the tip rail such that a top segment of the counterbore is removed and a bottom segment of the counterbore extends radially to an opening on the workpiece interface.

[0083] More specifically, prior to the removing step, the counterbore may define a pre-machined radial height. In such embodiments, the method may include removing a tip portion of the tip rail such that the remaining radial height of the counterbore is between about 40% and about 60%, or such as between about 45% and about 55%, or such as about 50%, of the pre-machined radial height.

[0084] In an exemplary implementation, method 1200 may include, at (1206), additively manufacturing an extension at the workpiece interface and across the opening (or in an embodiment where each of the tip cooling holes is exposed after removing the tip portion, across all of the openings). In many implementations, the additive manufacturing at (1206) is performed using an additive manufacturing system. The additive manufacturing system may include a vision system operably connected to an additive welding machine; a control system; and a user interface. In such embodiments, method 1200 may include, at (1204), after the removal step, positioning a digital marker between two adjacent openings on a digital representation of the workpiece interface. The digital representation is captured by the vision system. The positioning at (1204) may be performed manually by a user using a user interface or automatically by a control system. The positioning at (1204) may be after the removal at (1202) and before the additive manufacturing at (1206). For example, the digital marker may be positioned after the removal step because the opening will be exposed and therefore visible through the vision system. This advantageously increases the accuracy and precision of the additive manufacturing step, resulting in fewer defects in the printed stretches.

[0085] In various embodiments, method 1200 may include, at (1208), machining the extension to form a replacement tip portion of the tip rail within design specifications. Additionally, method 1200 may include, at (1210), reopening at least one of the plurality of tip cooling channels (e.g., by removing a portion of the extension).

[0086] Importantly, in an exemplary implementation, weld material may not be disposed in the tip cooling passages (such as in counterbores and / or through-holes) prior to removal at (1202) and prior to additive manufacturing at (1206). This advantageously allows the openings to be visible at the workpiece interface, which allows the digital indicia to be positioned relative to the openings, thereby enabling more efficient additive manufacturing of the extensions.

[0087] Fig.13 A block diagram of an exemplary computing system 600 is provided. The computing system 600 may be used to implement various aspects disclosed herein. The computing system 600 may include one or more computing devices 602. For example, the above reference Fig. 9 The control system 206 can be configured and operable in the same or similar manner as one of the computing devices 602 .

[0088] like Fig.13As shown, one or more computing devices 602 may each include one or more processors 604 and one or more memory devices 606. One or more processors 604 may include any suitable processing device, such as a microprocessor, a microcontroller, an integrated circuit, a logic device, or other suitable processing device. One or more memory devices 606 may include one or more computer-readable media, including but not limited to one or more non-transitory computer-readable media, RAM, ROM, hard disk drives, flash drives, and other memory devices, such as one or more buffer devices.

[0089] The one or more memory devices 606 may store information accessible by the one or more processors 604, including computer-readable or computer-executable instructions 608 that may be executed by the one or more processors 604. The instructions 608 may be any set of instructions or control logic that, when executed by the one or more processors 604, causes the one or more processors 604 to perform operations. The instructions 608 may be software written in any suitable programming language or may be implemented in hardware. In some embodiments, the instructions 608 may be executed by the one or more processors 604 to cause the one or more processors 604 to perform operations.

[0090] The memory device 606 may further store data 610 accessible by the processor 604. For example, the data 610 may include sensor data as described herein, such as engine parameters, model data, logic data, etc. According to an exemplary embodiment of the present disclosure, the data 610 may include one or more tables, functions, algorithms, models, formulas, etc.

[0091] The one or more computing devices 602 may also include a communication interface 612 for communicating, for example, with other components of the additive manufacturing system. The communication interface 612 may include any suitable components for interfacing with one or more networks, including, for example, a transmitter, a receiver, a port, a controller, an antenna, or other suitable components.

[0092] The technology discussed herein refers to computer-based systems and the actions taken by computer-based systems and the information sent to and from computer-based systems. It should be understood that the inherent flexibility of computer-based systems allows for the division of tasks and functionality between various possible configurations, combinations, and components. For example, the processes discussed herein can be implemented using a single computing device or multiple computing devices working in combination. Databases, memories, instructions, and applications can be implemented on a single system or distributed on multiple systems.

[0093] Although specific features of various embodiments may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the present disclosure, any feature of a drawing may be referenced and / or claimed in combination with any feature of any other drawing.

[0094] This written description uses examples to disclose the invention, including the best mode, and also enables any person skilled in the art to practice the invention, including making and using any device or system and performing any combined method. The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. If these other examples include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that do not differ substantially from the literal language of the claims, these other examples are intended to be within the scope of the claims.

[0095] Further aspects of the invention are provided by the subject matter of the following clauses:

[0096] A method for repairing an airfoil of a turbine component, the airfoil including a tip rail, the tip rail at least partially defining a plurality of tip cooling passages, the turbine component having undergone at least one operating cycle such that a tip portion of the tip rail is outside of design specifications, the method comprising: removing the tip portion of the tip rail such that a workpiece interface is defined at a radially outer end of the airfoil, wherein after removing the tip portion, at least one of the plurality of tip cooling passages extends to an opening at the workpiece interface; additively manufacturing an extension segment at the workpiece interface; and machining the extension segment to form a replacement tip portion of the tip rail within the design specifications.

[0097] A method according to any of the preceding clauses, wherein, prior to the removing step, the plurality of tip cooling channels each include a through hole and a counterbore, the counterbore extending from the through hole and radially beyond the through hole, and wherein removing the portion further comprises: removing the tip portion of the tip guide such that the counterbore extends radially to the opening at the workpiece interface.

[0098] A method according to any of the preceding clauses, wherein prior to the removing step, the counterbore defines a pre-machined radial height, and wherein removing the portion further comprises: removing the tip portion of the tip guide such that a remaining radial height of the counterbore is between approximately 40% and approximately 60% of the pre-machined radial height.

[0099] A method according to any of the preceding clauses, wherein, prior to the removing step, the plurality of tip cooling channels each include a through hole and a counterbore, the counterbore extending from the through hole and radially across the through hole, and wherein the method further comprises: removing the tip portion of the tip guide such that a top section of the counterbore is removed and a bottom section of the counterbore extends radially to the opening at the workpiece interface; additively manufacturing the extension section at the workpiece interface and across the opening; and removing a portion of the extension section corresponding to the top section of the counterbore to restore the counterbore.

[0100] A method according to any of the preceding clauses, wherein each of the plurality of tip cooling channels comprises a through hole and a counterbore, wherein the counterbore extends from the through hole and radially across the through hole, and wherein the method further comprises, after the additive manufacturing step, reopening the counterbore by removing a portion of the extension segment.

[0101] A method according to any preceding clause, wherein prior to the removing step and prior to the additive manufacturing step, no welding material is provided in the plurality of tip cooling channels.

[0102] A method according to any preceding clause, wherein the method further comprises: welding a defect in the tip rail to produce a weld defect; and blending the weld defect flush with the tip rail.

[0103] A method according to any of the preceding clauses, wherein additive manufacturing is performed using an additive manufacturing system, the additive manufacturing system including a vision system, the vision system being operably connected to an additive welding machine and a control system, wherein the method further comprises: after the removing step, positioning a digital mark between two adjacent openings on a digital representation of the workpiece interface, the digital representation being captured by the vision system.

[0104] A method according to any preceding clause, wherein the positioning step is subsequent to the removing step and prior to the additive manufacturing step.

[0105] A method for repairing an airfoil of a turbine component, the airfoil including a tip rail, the tip rail at least partially defining a plurality of tip cooling passages, the turbine component having undergone at least one operating cycle such that a tip portion of the tip rail is outside of design specifications, the method comprising: removing the tip portion of the tip rail such that a workpiece interface is defined at a radially outer end of the airfoil, wherein after removing the tip portion, at least one of the plurality of tip cooling passages extends to an opening at the workpiece interface; additively manufacturing an extension at and across the opening at the workpiece interface; machining the extension to form a replacement tip portion of the tip rail within the design specifications; and reopening the at least one of the plurality of tip cooling passages.

[0106] A method according to any of the preceding clauses, wherein, prior to the removing step, the plurality of tip cooling channels each include a through hole and a counterbore, the counterbore extending from the through hole and radially beyond the through hole, and wherein removing the portion further comprises: removing the tip portion of the tip guide such that the counterbore extends radially to the opening at the workpiece interface.

[0107] A method according to any of the preceding clauses, wherein prior to the removing step, the counterbore defines a pre-machined radial height, and wherein removing the portion further comprises: removing the tip portion of the tip guide such that a remaining radial height of the counterbore is between approximately 40% and approximately 60% of the pre-machined radial height.

[0108] A method according to any of the preceding clauses, wherein, prior to the removing step, the plurality of tip cooling channels each include a through hole and a counterbore, the counterbore extending from the through hole and radially across the through hole, and wherein the method further comprises: removing the tip portion of the tip guide such that a top section of the counterbore is removed and a bottom section of the counterbore extends radially to the opening at the workpiece interface; additively manufacturing the extension section at the workpiece interface and across the opening; and removing a portion of the extension section corresponding to the top section of the counterbore to restore the counterbore.

[0109] A method according to any of the preceding clauses, wherein each of the plurality of tip cooling channels comprises a through hole and a counterbore, wherein the counterbore extends from the through hole and radially across the through hole, and wherein the method further comprises, after the additive manufacturing step, reopening the counterbore by removing a portion of the extension segment.

[0110] A method according to any preceding clause, wherein prior to the removing step and prior to the additive manufacturing step, no welding material is provided in the plurality of tip cooling channels.

[0111] A method according to any preceding clause, wherein the method further comprises: welding a defect in the tip rail to produce a weld defect; and blending the weld defect flush with the tip rail.

[0112] A method according to any of the preceding clauses, wherein additive manufacturing is performed using an additive manufacturing system, the additive manufacturing system including a vision system, the vision system being operably connected to an additive welding machine and a control system, wherein the method further comprises: after the removing step, positioning a digital mark between two adjacent openings on a digital representation of the workpiece interface, the digital representation being captured by the vision system.

[0113] A method according to any preceding clause, wherein the positioning step is subsequent to the removing step and prior to the additive manufacturing step.

Claims

1. A method of repairing an airfoil of a turbine component, the airfoil comprising a tip rail, the tip rail at least partially defining a plurality of tip cooling passages, the turbine component having undergone at least one operating cycle such that a tip portion of the tip rail is outside of design specifications, the method comprising: removing the tip portion of the tip rail such that a workpiece interface is defined at a radially outer end of the airfoil, wherein after removing the tip portion, at least one tip cooling channel of the plurality of tip cooling channels extends to an opening on the workpiece interface; additively manufacturing an extension section on the workpiece interface; as well as The extension is machined to form a replacement tip portion of the tip rail within the design specifications.

2. The method according to claim 1, wherein: Prior to the removing step, the plurality of tip cooling passages each include a through hole and a counterbore extending from the through hole and radially across the through hole, and wherein removing the portion further comprises: The tip portion of the tip rail is removed such that the counterbore extends radially to the opening at the workpiece interface.

3. The method of claim 2, wherein prior to the removing step, the counterbore defines a pre-machined radial height, and wherein removing the portion further comprises: The tip portion of the tip rail is removed such that a remaining radial height of the counterbore is between about 40% and about 60% of the pre-machined radial height.

4. The method according to claim 1, wherein: Prior to the removing step, the plurality of tip cooling passages each include a through hole and a counterbore extending from and radially across the through hole, and wherein the method further comprises: removing the tip portion of the tip rail such that a top section of the counterbore is removed and a bottom section of the counterbore extends radially to the opening at the workpiece interface; additively manufacturing the extension segment at the workpiece interface and across the opening; and A portion of the extension section corresponding to the top section of the counterbore is removed to restore the counterbore.

5. The method of claim 1 , wherein the plurality of tip cooling passages each include a through hole and a counterbore extending from and radially across the through hole, and wherein the method further comprises: After the additive manufacturing step, the counterbore is reopened by removing a portion of the extension.

6. The method of claim 1, wherein prior to the removing step and prior to the additive manufacturing step, no welding material is disposed in the plurality of tip cooling channels.

7. The method according to claim 1, wherein the method further comprises: welding a defect in the tip rail to produce a weld defect; as well as The weld defect is blended flush with the tip rail.

8. The method of claim 1, wherein additive manufacturing is performed using an additive manufacturing system, the additive manufacturing system comprising a vision system operably connected to the additive welding machine and the control system, wherein the method further comprises: After the removing step, a digital marker is positioned between two adjacent openings on a digital representation of the workpiece interface, the digital representation being captured by the vision system.

9. The method of claim 8, wherein the positioning step is performed after the removing step and before the additive manufacturing step.

10. A method of repairing an airfoil of a turbine component, the airfoil comprising a tip rail, the tip rail at least partially defining a plurality of tip cooling passages, the turbine component having undergone at least one operating cycle such that a tip portion of the tip rail is outside of design specifications, the method comprising: removing the tip portion of the tip rail such that a workpiece interface is defined at a radially outer end of the airfoil, wherein after removing the tip portion, at least one tip cooling channel of the plurality of tip cooling channels extends to an opening on the workpiece interface; additively manufacturing an extension section at the workpiece interface and across the opening; machining the extension to form a replacement tip portion of the tip rail within the design specifications; as well as The at least one tip cooling channel of the plurality of tip cooling channels is reopened.

11. The method according to claim 10, wherein: Prior to the removing step, the plurality of tip cooling passages each include a through hole and a counterbore extending from the through hole and radially across the through hole, and wherein removing the portion further comprises: The tip portion of the tip rail is removed such that the counterbore extends radially to the opening at the workpiece interface.

12. The method of claim 11, wherein prior to the removing step, the counterbore defines a pre-machined radial height, and wherein removing the portion further comprises: The tip portion of the tip rail is removed such that a remaining radial height of the counterbore is between about 40% and about 60% of the pre-machined radial height.

13. The method according to claim 10, wherein: Prior to the removing step, the plurality of tip cooling passages each include a through hole and a counterbore extending from and radially across the through hole, and wherein the method further comprises: removing the tip portion of the tip rail such that a top section of the counterbore is removed and a bottom section of the counterbore extends radially to the opening at the workpiece interface; additively manufacturing the extension segment at the workpiece interface and across the opening; and A portion of the extension section corresponding to the top section of the counterbore is removed to restore the counterbore.

14. The method of claim 10, wherein the plurality of tip cooling passages each include a through hole and a counterbore extending from and radially across the through hole, and wherein the method further comprises: After the additive manufacturing step, the counterbore is reopened by removing a portion of the extension.

15. The method of claim 10, wherein prior to the removing step and prior to the additively manufacturing step, no welding material is disposed in the plurality of tip cooling channels.

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