Method of repairing airfoil having tip cooling passage

Abstract

To provide a new process for repairing a tip portion of a blade for a turbomachine.SOLUTION: An airfoil includes a tip rail that at least partially defines a plurality of tip cooling passages. A turbine component undergoes at least one operational cycle, and the tip portion of the tip rail is outside of a design specification range. A method includes a step of removing the tip portion of the tip rail such that a processed surface is defined at the radially outer end of the airfoil. After the tip portion is removed, at least one tip cooling passage of the plurality of tip cooling passages extends to the opening on the processed surface. The method further includes a step of additively manufacturing an extension segment onto the processed surface. The method further includes machining the extension segment to form a replacement tip portion of the tip rail, which is within the design specification range.SELECTED DRAWING: Figure 11

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] Turbo machines are used in various industries and applications for the purpose of energy transmission. For example, a gas turbine engine generally 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 flowing into the gas turbine engine and supplies this 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 gas. The combustion gas flows from the combustion section into the turbine section, and the combustion gas expands around the turbine components to generate work. For example, when the combustion gas expands in the turbine section, a rotor shaft connected to, for example, a generator can rotate to generate electricity. Next, the combustion gas flows through the exhaust section and is discharged from the gas turbine.

[0003] The turbine blade is surrounded by high-temperature combustion gas, and therefore, it is necessary to effectively cool the turbine blade in order to extend its service life. The airfoil of the turbine blade is hollow and is arranged to be in fluid communication with the compressor, and pressurized air is output from the compressor and can be used to cool the airfoil. Cooling of the airfoil is very complicated, and cooling can be achieved using various forms of internal cooling channels and internal cooling portions, as well as cooling holes penetrating the wall of the airfoil to discharge the cooling air.

[0004] The tip of the blade is particularly difficult to cool. This is because the tip of the blade is directly adjacent to the turbine shroud and hot combustion gases flow through the tip clearance. Therefore, a portion of the air flowing inside the blade can typically flow through the tip and be discharged and cooled. The tip typically includes edge ribs that project continuously and radially outwardly along the pressure side and the suction side between the leading edge and the trailing edge. The edge ribs follow the aerodynamic contour around the blade and contribute significantly to the aerodynamic efficiency of the blade.

[0005] The edges of other types of rotor tips may require repair after the turbomachine has been in use for some time due to the effects of erosion or high-temperature oxidation. In the repair process, material is typically added to the tip and then the tip is machined to match the specifications of the turbine blade. However, in known repair methods, due to the strong welding heat in this tip region, cracks may occur around the cooling passages of the tip. Furthermore, in known repair methods, when re-drilling the cooling holes, the drill or laser may collide with the rear wall of the cooling passage, causing damage due to backstrike.

[0006] From these considerations, it is clear that there is a need in the art for a new process for repairing the tips of blades for turbomachines. SUMMARY OF THE INVENTION

[0007] Aspects and advantages of the methods according to the present disclosure are described in part in the following description, will be apparent from the following description, or can be obtained through the practice of the present 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 passages. The turbine component has undergone at least one operating cycle, and a tip portion of the tip rail is outside the design specification range. The method includes removing the tip portion of the tip rail such that a machined surface is defined at a radially outer end of the airfoil. After the tip portion is removed, at least one of the plurality of tip cooling passages extends to an opening of the machined surface. The method further includes additive manufacturing an extension segment on the machined surface. The method further includes machining the extension segment to form a replacement tip portion within the design specification range of the tip rail.

[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 passages. The turbine component has undergone at least one operating cycle, and a tip portion of the tip rail is outside the design specification range. The method includes removing the tip portion of the tip rail such that a machined surface is defined at a radially outer end of the airfoil. After the tip portion is removed, at least one of the plurality of tip cooling passages extends to an opening of the machined surface. The method further includes additive manufacturing an extension segment across the machined surface and the opening. The method further includes machining the extension segment to form a replacement tip portion within the design specification range of the tip rail. The method further includes reopening at least one of the plurality of tip cooling passages.

[0010] These features, aspects, and advantages of the method, as well as other features, aspects, and advantages, will become further understood by reference to the following description and the claims. The drawings, which are incorporated herein and constitute a part of this specification, illustrate embodiments of the technology and, together with the specification, serve to explain the principles of the technology.

Brief Description of the Drawings

[0011] A complete and enabling disclosure of the present method, directed to those of ordinary skill in the art (including the best mode of making and using the present system and method), is set forth herein, and reference is made in the specification to the following drawings.

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[0012] Next, embodiments of the present invention will be described in detail, and one or more examples of the embodiments will be illustrated in the drawings. Each example is provided for the purpose of explanation, not to limit the technology. In fact, it is clear to those skilled in the art that the technology can be modified and deformed without departing from the scope or spirit of the claimed technology. For example, features illustrated or described as part of one embodiment can be used with another embodiment to obtain still another embodiment. Accordingly, the present disclosure is intended to cover modifications and variations that fall within the scope of the claims and their equivalents.

[0013] As used herein, the term "exemplary" is used in the sense of an example, instance, or illustration. Embodiments described as "exemplary" herein should not necessarily be construed as more preferred or advantageous than other forms. Any embodiment described as "exemplary" herein is not necessarily construed as more preferred or advantageous than other embodiments. Further, unless otherwise specified, all embodiments described herein should be considered exemplary.

[0014] In the detailed description of the invention, numerical and alphabetical symbols are used to refer to the features of the drawings. Like or similar reference numerals in the drawings and the detailed description are used to represent like or similar parts of the present invention. As used herein, the terms "first", "second", and "third" can be used interchangeably to distinguish between components and are not intended to mean the position or importance of individual components.

[0015] The term "fluid" may be a gas or a liquid. The term "fluid communication" means that two or more regions defining a flow path are joined together such that fluid can connect (i.e., flow) between the designated regions.

[0016] As used herein, the terms "upstream (of)" (or "forward (of)") and "downstream (of)" (or "rearward (of)") refer to relative directions with respect to the flow of fluid in a fluid path. For example, "upstream (of)" refers to the direction from which the fluid is flowing, and "downstream (of)" refers to the direction in which the fluid is flowing. In the case of an exhaust diffuser assembly, "upstream (of)" refers to the direction closest to the turbine section, and "downstream (of)" refers to the outlet end of the exhaust diffuser assembly.

[0017] The term "radially" refers to a relative direction that is substantially perpendicular to the axial centerline of a particular component, the term "axially" refers to a relative direction that is substantially parallel and / or coaxial with the axial centerline of a particular component, and the term "circumferentially" refers to a relative direction that extends around the axial centerline of a particular component.

[0018] Terms representing approximation (such as "about", "approximately", "substantially", etc.) are not limited to the specified exact values. In at least some examples, the language representing approximation may correspond to the accuracy of the device for measuring the value, or to the accuracy of the method or machine for constructing or manufacturing the component and / or system. In at least some examples, the language representing approximation may correspond to the accuracy of the device for measuring the value, or to the accuracy of the method or machine for constructing or manufacturing the component and / or system. For example, the language representing approximation may indicate that it is within a margin of 1%, 2%, 4%, 5%, 10%, 15%, or 20% at any of the individual values, ranges of values, and / or end values defining the range of values. When used in the context of an angle or direction, such terms include values within a range 10 degrees greater than or less than the angle or direction mentioned. For example, "substantially perpendicular" includes directions within 10 degrees of perpendicular in any direction (e.g., clockwise or counterclockwise).

[0019] Terms such as "coupled", "fixed", "attached to", etc., unless otherwise specified herein, represent both being directly coupled, directly fixed, or directly attached, and being indirectly coupled, indirectly fixed, or indirectly attached by the intervention of one or more intermediate components or intermediate parts. Terms such as "directly coupled", "directly fixed", "directly attached", etc., mean that two components are coupled such that they are in contact with each other and there are no intermediate components or intermediate parts.

[0020] As used herein, the terms "comprise," "comprising," "include," "including," "has," "having," or other variations of these terms are intended to be inclusive without limitation. For example, a process, method, article, or apparatus that includes a list of characteristic parts is not necessarily limited only to those characteristic parts, and may include other characteristic parts not explicitly listed or other characteristic parts not inherent to the process, method, article, or apparatus. Further, unless explicitly stated to the contrary, "and / or" represents a condition satisfied by any one of "A is true (or exists) and B is false (or does not exist)," "A is false (or does not exist) and B is true (or exists)," and "both A and B are true (or exist).

[0021] Throughout this specification and the claims, limitations that are combined, interchanged, and such ranges are specified, and unless the context or language indicates otherwise, include all sub-ranges included within that range. For example, all ranges disclosed herein include the end values of that range, and those end values can be combined independently of each other.

[0022] Referring now to the drawings, FIG. 1 shows a schematic diagram of one embodiment of a turbomachine, and in the illustrated embodiment, the turbomachine is a gas turbine 10. Industrial or land-based gas turbines are illustrated and described herein, but the present disclosure is not limited to industrial and / or land-based gas turbines unless otherwise specified in the claims. For example, the invention described herein can be used in any type of turbomachine (e.g., steam turbine, aircraft gas turbine, or marine gas turbine, but not limited thereto).

[0023] 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 section 16 disposed at the upstream end of the gas turbine engine 10. The gas turbine engine 10 further includes a combustion section 18 having one or more combustors 20 disposed downstream of the compressor section 12. The gas turbine engine 10 further includes a turbine section 22 downstream of the combustion section 18. The shaft 24 extends generally axially within the gas turbine engine 10.

[0024] The compressor section 12 can 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 21. Each rotor disk 21 may be coupled to an upstream portion of the shaft 24 that passes through the compressor section 12 or may form an upstream portion of the shaft 24. The rotor blades 23 of the compressor section 12 can include airfoils of a turbomachine that define an airfoil shape (e.g., an airfoil having a leading edge, a trailing edge, and sidewalls extending between the leading edge and the trailing edge). Further, the compressor section 12 includes stator vanes disposed between the rotor blades to define a series of compression stages. The stator vanes extend from the compressor casing and can be coupled to the compressor casing.

[0025] The turbine section 22 can generally include a plurality of rotor disks 27 and a plurality of rotor blades 28 that extend radially outward from each rotor disk 27 and are interconnected to each rotor disk 27. Each rotor disk 27 may be coupled to a portion of the shaft 24 that passes through the turbine section 22, or may form such a portion of the shaft 24. The turbine section 22 further includes an outer casing 32 that surrounds the downstream portion of the shaft 24 and the rotor blades 28 in the circumferential direction. The turbine section 22 can include stationary nozzles 26 that extend radially inward from the outer casing 32. The rotor blades 28 and the stationary nozzles 26 can be alternately arranged to form stages along the axial centerline 30 of the gas turbine 10. The rotor blades 28 and the stationary nozzles 26 can include airfoils of a turbomachine that define an airfoil shape (e.g., having a leading edge, a trailing edge, and sidewalls extending between the leading edge and the trailing edge).

[0026] In operation, ambient air 36 or other working fluid is drawn into the inlet 16 of the compressor 14 and gradually compressed to supply compressed air 38 to the combustion section 18. The compressed air 38 flows into the combustion section 18 and is mixed with 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, and the combustion gases 42 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 producing mechanical work. The combustion gases 42 exit the turbine section 22 and flow through the exhaust diffuser 34 across a plurality of struts 44 disposed within the exhaust diffuser 34.

[0027] The gas turbine engine 10 can define a cylindrical coordinate system having an axial direction A that extends along the axial centerline 30, a radial direction R that is perpendicular to the axial centerline 30, and a circumferential direction C that extends around the axial centerline 30.

[0028] Referring to FIG. 2, a perspective view of a turbine component 100 according to an exemplary aspect of the present disclosure is shown, in which a part of the positive pressure side wall 108 is cut away to show the internal cooling passage 120. In an exemplary embodiment, the turbine component 100 can be a turbine blade. However, in other embodiments, the turbine component can be a turbine vane and / or a turbine nozzle. The turbine component 100 can be configured in the same manner as the rotor blade 28 of the turbine section 22 of the gas turbine 10 described above with reference to FIG. 1. As shown, the turbine component 100 is a platform 102 disposed at the junction of the airfoil 104 and the dovetail 106, and includes a platform 102 that defines a portion of the radially inner flow path of the combustion gas.

[0029] The airfoil 104 can include a generally concave positive pressure side wall 108 and an opposite generally convex negative pressure side wall 110. Each of the positive pressure side wall 108 and the negative pressure side wall 110 can extend between a leading edge 112 and a trailing edge 114. Further, each of the positive pressure side wall 108 and the negative pressure side wall 110 extends radially (e.g., in the radial direction R) from the root portion 116 on the platform 102 to the tip portion 118. The airfoil 104 can terminate at the tip portion 118 in the radial direction. Thus, the airfoil 104 may not include a tip shroud extending from the tip portion 118.

[0030] According to an exemplary aspect of the present disclosure, the airfoil 104 can include a tip rail or edge rail 122 that extends radially outward from the positive pressure side wall 108 and the negative pressure side wall 110. The tip rail 122 defines a tip cavity 124 and can have the same shape as the airfoil 104. In particular, the tip cavity 124 can be defined by the tip rail 122 and a floor 126. The floor 126 can be located radially inside the tip portion 118. The tip rail 122 can extend radially outward from the floor 126 to the tip portion 118.

[0031] In many embodiments, the tip rail 122 can include a positive pressure side portion 128 and a negative pressure side portion 130. The positive pressure side portion 128 can extend radially outward from the positive pressure side wall 108, and the negative pressure side portion 130 can extend radially outward from the negative pressure side wall 110.

[0032] An internal cooling flow path 120 can be defined within the airfoil 104 (e.g., between the positive pressure side wall 108 and the negative pressure side wall 110). The cooling air supplied to the internal cooling flow path 120 can be taken out from the compressor section 12 by any conventional method. The interior of the airfoil 104 can have any structure (e.g., a serpentine flow path formed with various turbulators) to improve the effect of the cooling air. The cooling air from the internal cooling flow path 120 can flow through and be discharged from the film cooling holes 132 defined in the side walls 108, 110 and / or the trailing edge discharge holes 134 defined in the trailing edge 114. Further, one or more tip cooling passages 136 can be defined at least partially in the tip rail 122 (such as the positive pressure side portion 128 and / or the negative pressure side portion 130).

[0033] In many embodiments, as shown, the tip rail 122 can define a tip shelf 138, and the tip shelf 138 can include a floor 140. The tip shelf can be a recess defined in the positive pressure side portion 128 of the tip rail 122. The floor 140 can be generally perpendicular to the radial direction R. The floor 140 can define a plurality of shelf output portions 142, and the plurality of shelf output portions 142 can discharge the cooling air from the internal cooling flow path 120 in the radial direction R.

[0034] Next, referring to FIGS. 3 and 4, each figure shows an enlarged view of the airfoil 104 according to various aspects of the present disclosure. As shown, the tip cooling passage 136 can be defined in the tip rail 122 at the positive pressure side portion 128 and / or the negative pressure side portion 130. Further, the tip cooling passages 136 can be arranged at equal intervals. Each tip cooling passage 136 can be arranged at generally the same height (or span length) in the radial direction of the airfoil 104 such that each tip cooling passage 136 is arranged within a range of about 0% to about 5% of the common height (or span length) in the radial direction of the airfoil 104.

[0035] Further, as shown, each tip cooling passage 136 can be elongated in the radial direction R such that the longest dimension of each tip cooling passage 136 is generally parallel to the radial direction R. Specifically, each tip cooling passage 136 can be in an elliptical shape, but other shapes are also possible and other shapes are within the scope of the present disclosure.

[0036] In operation, the airfoil 104 including the tip rail 122 is exposed to high-temperature combustion gases and is subject to vibrations and mechanical forces due to operation, and thus the airfoil 104 may deviate from the design specification range. Specifically, the tip rail 122 may lose material over time and / or the material may be distorted over time due to the movement of the tip rail and exposure to combustion gases, whereby the tip rail 122 may deviate from the design specification range (this range is the range where peak efficiency appears). The lost material and / or the distorted material can be removed using an additive manufacturing process and remanufactured. As will be described in more detail later, this process includes machining the tip rail 122 to the machining stop line 158 such that a part of the tip cooling passage 136 is exposed, adding new material with an additive manufacturing system, and machining the new material such that the tip rail is within the design specification range.

[0037] Next, referring to FIGS. 5-8, each figure shows a schematic cross-sectional view of the airfoil 104 taken along line C-C shown in FIG. 3 according to an embodiment of the present disclosure. In particular, each of FIGS. 5-8 shows a cross-sectional view of the airfoil 104 at various steps of the repair process. As shown in FIGS. 5-8, the airfoil 104 can include a positive pressure sidewall 108 and a negative pressure sidewall 110. The airfoil 104 can include a tip rail 122, and the tip rail 122 can have a positive pressure side portion 128 extending from (e.g., radially) the positive pressure sidewall 108 and a negative pressure side portion 130 extending from (e.g., radially) the negative pressure sidewall 110. The tip rail 122 and the cap 125 (the cap 125 defines a floor 126) can define a tip cavity 124.

[0038] An internal cooling flow path 120 can be defined within the airfoil 104 (e.g., between the positive pressure sidewall 108, the negative pressure sidewall 110, and the cap 125). A tip cooling passage 136 can extend from the internal cooling flow path 120. In particular, the tip cooling passage 136 can include a counterbore 146 and a through hole 148. The counterbore 146 can be defined in the tip rail 122, and the through hole can be defined in the tip rail 122 and / or the positive pressure sidewall 108. The through hole 148 can extend from the internal cooling flow path 120 to the counterbore 146, and the counterbore 146 can extend from the through hole 148 to the outer surface 150 at the positive pressure sidewall 108 of the airfoil 104. Further, the counterbore 146 extends wider than the through hole 148 in the radial direction. The airfoil 104 can include a radially outermost surface 153, and the counterbore 146 is radially spaced apart from (e.g., before the repair process) the radially outermost surface 153. The counterbore 146 can have a diameter larger than that of the through hole 148. Although FIGS. 5-8 illustrate the tip cooling passage 136 defined on the positive pressure side, it should be understood that the tip cooling passage 136 can also be arranged on the negative pressure side.

[0039] FIG. 5 shows a cross-sectional view of the airfoil 104 of the turbine component 100 before being machined such that a worn / distorted tip portion 172 is removed. In this state, the airfoil 104 has undergone at least one operating cycle (such as the gas turbine 10 described above with reference to FIG. 1), and the tip portion 172 of the tip rail 122 is worn and / or distorted and may be out of the design specification range. The design specification range can correspond to the peak efficiency range of the airfoil 104. That is, the design specification range is the aerodynamic profile and / or contour that extracts the most energy from the combustion gas when implemented in the gas turbine 10. Thus, in the repair method disclosed herein, advantageously, the worn / distorted material is removed and new material is added by laser deposition and / or additive manufacturing to restore the tip portion 172 of the tip rail 122 of the airfoil 104 to the design specification range. As shown in FIG. 5, the counterbore 146 of the tip cooling passage 136 defines a radial height 152 before machining. The radial height 152 before machining can be defined at the opening 151 of the counterbore 146 on the outer surface 150 of the airfoil 104.

[0040] According to an exemplary implementation of the repair method, the method can include removing the tip portion 172 of the tip rail 122 (e.g., by a machining process or a subtractive process) such that a portion of the counterbore 146 is removed and a through-hole 148 remains (e.g., as it is and not machined). Specifically, the method can include removing the tip portion 172 of the tip rail 122 such that a machining surface 220 (or upper surface) is defined at the radially outer end of the airfoil 104. As shown in FIG. 6, after removing the tip portion 172, at least one tip cooling passage 136 of the plurality of tip cooling passages extends to an opening 170 on the machining surface 220 (the opening is at least partially defined by the machining surface 220, for example). More specifically, as shown, after removing the tip portion 172, the counterbore 146 is exposed and extends to the opening 170 of the machining surface 220.

[0041] As shown in FIG. 5, the machining stop line 158 can be set at approximately half of the radial height 152 before the machining of the counterbore 146. The machining stop line 158 is also shown in FIGS. 3 and 4. This line can represent the portion of the tip cooling passage 136 to be removed before implementing the repair method. Specifically, the outside in the radial direction of the machining stop line 158 can be removed. The machining stop line 158 can form a part of a machining stop surface perpendicular to the radial direction R.

[0042] The machining stop line 158 can be positioned between approximately 40% and 60% of the radial height 152 before machining. In other embodiments, the machining stop line 158 can be positioned between approximately 45% and 55% of the radial height 152 before machining. In a particular embodiment, the machining stop line 158 can be positioned at approximately 50% of the radial height 152 before machining.

[0043] In other words, when the tip portion 172 is removed (e.g., removed by machining), the remaining radial height 174 of the counterbore 146 remains. The remaining radial height 174 is the radial height of the counterbore 146 at the opening 151. When the tip portion 172 is removed, the remaining radial height 174 can be a height between approximately 40% and 60% of the radial height 152 before machining, between approximately 45% and 55% of the radial height 152 before machining, or a height of approximately 50%.

[0044] FIG. 6 shows the airfoil 104 after the tip portion 172 of the tip rail 122 (e.g., the portion of the tip rail 122 outside the radial direction of the machining stop line 158) has been removed. At this stage, the airfoil 104 can define a machining surface 220 (or upper surface). The machining surface 220 can define an opening 170 in 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 is removed, the remaining portion of the counterbore 146 extends radially outward to the opening 170 of the machining surface 220.

[0045] As shown in FIGS. 5 and 6, the counterbore can include an upper segment 176 (or radially outer segment) and a bottom segment 178. The upper segment 176 is radially outside the machining stop line 158, and the bottom segment 178 is radially inside the machining stop line 158. The repair method can include removing the tip portion 172 of the tip rail 122 such that the upper segment 176 of the counterbore 146 is removed and the bottom segment 178 of the counterbore extends radially to the opening 170 of the machining surface 220.

[0046] As shown in FIGS. 5-8, in some embodiments, the airfoil 104 may have one or more defects 180 (shown in FIG. 5), i.e., surface cracks, formed as a result of operation within the gas turbine. In such an implementation, the repair method can include welding the defect 180 (e.g., manual welding) to produce a welded defect 182 (FIGS. 6-8) and smoothing the welded defect to be flush with the tip rail 122 (e.g., flush with the outer surface of the tip rail 122).

[0047] FIG. 7 shows the airfoil 104 after additive manufacturing and / or laser deposition has been performed, and new material 160 in the form of an extension segment 162 has been added to this airfoil 104. The extension segment 162 can extend beyond the opening 170. The extension segment 162 can be roughly adapted to the original contour of the airfoil 104 (e.g., the contour when the airfoil 104 was first manufactured before being used in a gas turbine), but the extension segment 162 may require additional post-processing so that the tip rail 122 returns to the design specification range. The extension segment 162 can be added to the machining surface 220 of the airfoil 104 by an additive manufacturing system 200 described below with reference to FIG. 9. After additive manufacturing (or printing), the counterbore 146 can define a post-print height 186, and the post-print height 186 is approximately equal to the remaining height 174 in the radial direction. Post-processing (such as drilling, boring, or using an electrical discharge machine) may be required to reopen the upper segment of the counterbore 146.

[0048] FIG. 8 shows the airfoil 104 after post-processing has been performed so that a replacement tip portion 184 within the design specification range is formed. The replacement tip portion 184 generally conforms to the contour of the tip portion 172, but there is no wear / distortion, and the replacement tip portion 184 is within the design specification range. During post-processing, the new material 160 has a portion of the new material 160 removed and / or the counterbore 146 is reopened so that the airfoil 104 returns to the design specification range. In particular, the repair method includes reopening the counterbore 146 (e.g., the upper segment of the counterbore) by removing a portion of the extension segment 162. The removed portion can be made to match the size / shape of the upper segment 176, and a new upper segment 179 of the counterbore 146 is formed in the extension segment 162.

[0049] Referring to FIG. 9, an exemplary additive manufacturing system 200 according to an exemplary aspect of the present disclosure is shown. As illustrated, the additive manufacturing system 200 includes a vision system 202, an additive welder 204, and a control system 206 operably configured to control the vision system 202 and / or the additive welder 204. The vision system 202 and the additive welder 204 may be provided as a single integrated unit or as separate stand-alone units. The vision system 202 and the additive welder 204 can be operably coupled to each other through a communication interface utilizing a wired or wireless communication link, thereby enabling a direct connection between the vision system 202 and the additive welder 204. The control system 206 can 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 welder 204, or separate control systems 206 may be operably configured to control the vision system 202 and the additive welder 204, respectively. The control system 206 can be implemented as part of the vision system 202, as part of the additive welder 204, and / or as an independent unit provided separately from the vision system 202 and / or the additive welder 204. The control system 206 can be operably coupled to the vision system 202 and / or the additive welder 204 through a communication interface utilizing a wired or wireless communication link, thereby enabling a direct connection between the control system 206 and the vision system 202 and / or between the control system 206 and the additive welder 204. The exemplary additive manufacturing system 200 can optionally include a user interface 208 and / or a management system 210.

[0050] In some embodiments, the control system 206 can determine a CAD model of an extension segment, generate one or more print commands based at least in part on the CAD model of the extension segment, and / or transmit the one or more print commands to cause the additive welder 204 to additively print the extension segment based at least in part on the print commands.

[0051] The vision system 202 can include one or more suitable cameras 212 or other machine vision devices that can be operably configured to obtain image data including a digital representation of one or more fields of view 214. Such digital representations may be referred to as digital images or images, although it is understood that the present disclosure can be implemented without rendering such digital representations in a form visible to humans. However, in some embodiments, a visible image corresponding to the field of view 214 can be displayed on the user interface 208, at least partially based on the digital representation of the one or more fields of view 214.

[0052] The additive manufacturing system 200 can obtain information related to one or more workpieces 216 on which one or more extension segments are each additively printed by the vision system 202. In particular, the vision system 202 can identify and define one or more workpieces 216 and instruct the additive welder 204 to appropriately print one or more extension segments onto the corresponding one or more workpieces 216 with high precision. The one or more workpieces 216 can be fixed to the shaping plate 218 with the machined surface (e.g., the upper surface) 220 of each workpiece 216 aligned with the shaping surface 222.

[0053] One or more cameras 212 of the vision system 202 can be configured to acquire two-dimensional or three-dimensional image data (including a two-dimensional digital representation of the field of view 214 and / or a three-dimensional digital representation of the field of view 214). By aligning the machined surface 220 and the shaped surface 222, one or more cameras 212 can obtain high-quality images. For example, one or more cameras 212 can have a focal length adjusted or adjustable to the shaped surface 222. With the machined surface 220 of one or more workpieces 216 aligned with the shaped surface 222, one or more cameras can obtain a digital image of the machined surface 220. One or more cameras 212 can have a field of view 214 that encompasses all or part of one or more workpieces 216 fixed to the shaping plate 218.

[0054] The image data obtained by the vision system 202 (including the digital representation of one or more workpieces 216) can be transmitted to the control system 206. The control system 206 can be configured to determine the machined surface 220 of each workpiece of the plurality of workpieces 216 from one or more digital representations of one or more fields of view 214 acquired by the vision system 202, and then to determine one or more coordinates of the machined surface 220 of each workpiece of the plurality of workpieces 216. Based on the one or more digital representations, the control system 206 can generate one or more printing commands, which are transmitted to the additive welding machine 204, and the additive welding machine 204 can additively print a plurality of extension segments to each workpiece of the plurality of workpieces 216. One or more printing commands can be configured such that a plurality of extension segments are additively printed and each extension segment of the plurality of extension segments is disposed on the machined surface 220 of the corresponding workpiece 216.

[0055] The additive welder 204 can utilize a desired additive manufacturing technique. In an exemplary embodiment, the additive welder can utilize a powder bed fusion (PBF) technique (such as direct metal laser melting (DMLM), electron beam melting (EBM), selective laser melting (SLM), direct metal laser sintering (DMLS), or selective laser sintering (SLS)). In some embodiments, the additive welder 204 can use a wire feed rod instead of, or in addition to, a powder bed. Further, in other embodiments, the extension segment can be manufactured completely manually using a welding torch and a wire rod, and thus, the additive manufacturing machine 204 may not be required.

[0056] Referring to FIG. 9, an exemplary additive welder 204 includes a powder supply chamber 224 including a source of powder 226 and a build chamber 228. A build plate 218 having one or more workpieces 216 secured thereto is disposed in the build chamber 228, and in the build chamber 228, the workpiece 216 can be laminated and printed layer by layer. The powder supply chamber 224 includes a powder piston 230 that raises a powder floor 232 while the system 200 is operating. As the powder floor 232 rises, a portion of the powder 226 is extruded from the powder supply chamber 224.

[0057] The recoater 234 (such as a roller or blade) traverses the working surface 236 and extrudes a portion of the powder 226 onto the shaping platform 238. The shaping plate 218 is fixed to the shaping platform 238 by a chuck system 240 and can be positioned with sufficient accuracy on the shaping platform 238 and / or within the shaping chamber 228. Before fixing the shaping plate 218 to the shaping platform 238, the workpiece 216 can be fixed to the shaping plate 218. The recoater 234 fills the shaping chamber 228 with the powder 226 and then sequentially distributes a thin layer of the powder 226 across the entire shaping surface 222 near the top of the workpiece 216 to additionally print successive layers of the workpiece 216. For example, the thin layer of the powder 226 can have a thickness of about 10 microns to about 100 microns (e.g., a thickness of about 20 μm to about 80 μm, a thickness of about 40 μm to about 60 μm, a thickness of about 20 μm to about 50 μm, a thickness of about 10 μm to about 30 μm). The shaping surface 222 represents a plane corresponding to the next layer of the workpiece 216 formed from the powder 226.

[0058] To form a layer of the extension segment (e.g., an interface layer or a subsequent layer) on the workpiece 216, the energy source 242 irradiates a thin layer of the powder 226 along the shaping surface 222 with an energy beam 244 (such as a laser or an electron beam), melting or fusing the powder 226 on top of the workpiece 216 (e.g., melting or fusing the layer to the machining surface 220 and / or melting or fusing the subsequent layer to that layer). The scanner 246 controls the path of the beam so as to melt or fuse only the portion of the layer of the powder 226 that is to be melted or fused to the workpiece 216. Typically, in a DMLM, EBM, or SLM system, the powder 226 is completely melted and each layer is melted or remelted by the passage of the energy beam 244. Conversely, in a DMLS or SLS system, the layer of the powder 226 is sintered and the particles of the powder 226 generally fuse to each other without reaching the melting point of the powder 226. After the layer of the powder 226 is melted or fused to the workpiece 216, the shaping piston 248 lowers the shaping platform 238 by a certain amount, defining the next shaping surface 222 for the next layer of the powder 226, and the recoater 234 distributes the next layer of the powder 226 over the entire shaping surface 222. Successive layers of the powder 226 can be melted or fused to the workpiece 216 in the above-described manner until the additive printing process is completed.

[0059] FIG. 10 shows a digital representation 300 of the field of view 214 including the machining surface 220 of the workpiece 216. Specifically, FIG. 10 shows the digital representation 300 of the field of view 214, within which the workpiece 216 is part of the tip rail 122 of the airfoil 104. The digital representation 300 of the tip rail 122 is captured by the vision system 202 after removing the worn material from the tip rail 122 to expose the tip cooling passage 136, and a plurality of tip cooling passages 136 can be seen on the machining surface 220 of the digital representation 300. For example, when the airfoil is in the state shown in FIG. 6, the digital representation 300 of the airfoil 104 can be captured, and in this case, the opening 170 can be seen on the machining surface 220.

[0060] The vision system 202 can supply the control system 206 with a digital representation 300 of the machined surface 220, and the control system 206 can generate and / or position a plurality of digital markers 302 on the digital representation 300 along the outer edge of the tip rail 122 of the machined surface 220. The digital markers 302 may be generated and positioned by the control system 206 or manually positioned by the user using the user interface 208. Connecting each digital marker 302 with a smooth line can create a digital profile 304 of the airfoil 104. The digital markers 302 can supply the control system 206 and / or the additive welder 204 with the profile 304 of the airfoil 104 at the machined surface 220. Thereafter, the control system 206 can instruct the additive welder 204 so that material is added to the tip rail 122 by the powder deposition and / or the laser following the profile 304 (e.g., the path of the line connecting the digital markers 302). The digital markers 302 may be disposed on the outer surface 150 of the airfoil 104 at the machined surface 220. Specifically, the digital markers 302 can be positioned between a plurality of openings 170 (i.e., the end clearance holes 146 of the tip cooling passage 136. Since the tip rail 122 has been removed at the initial stage of the repair procedure, the end clearance holes 146 are exposed on the machined surface 220). The digital markers 302 can be positioned between two adjacent tip cooling passages 136. Positioning the digital markers 302 in this way is advantageous because a more accurate profile 304 of the airfoil 104 can be generated than, for example, a profile assuming that the tip cooling passages 136 are not visible (e.g., assuming that the tip cooling passages are closed by welding and not visible, the digital markers 302 cannot be positioned relative to the tip cooling passages).

[0061] Referring now to FIG. 11, there is shown a flow diagram of an embodiment of a method 1100 for repairing an airfoil of a turbine component, according to an embodiment of the present subject matter. Generally, in this specification, method 1100 will be described with reference to the turbine component 100, the airfoil 104, and the additive manufacturing system 200 described above with reference to FIGS. 1 - 10. However, one of ordinary skill in the art will understand that the disclosed method 1100 can generally be used with any turbine component and / or with an additive manufacturing system having any other suitable system configuration. Additionally, FIG. 11 shows steps that are performed in a particular order for purposes of illustration and description, but the methods described herein are not limited to a particular order or arrangement unless otherwise specified in the claims. One of ordinary skill in the art will understand that, using the disclosure provided herein, various steps of the methods disclosed herein can be omitted, rearranged, combined, and / or adapted in various ways without departing from the scope of the present disclosure. The dashed boxes indicate optional steps of method 1100.

[0062] As shown in FIG. 11, a method for repairing an airfoil can include, at (1102), performing a pre - welding heat treatment on the airfoil of the turbine component. This can include heating the airfoil to a set temperature to relieve stress or remove hydrogen in order to ensure better weld quality prior to welding a crack or defect. In many implementations, method 1100 can include, at (1104), performing a pre - welding fluorescent penetrant inspection (FPI) on the airfoil. The pre - welding FPI can reveal defects that are not visible to the naked eye. This process can include cleaning the surface, applying a fluorescent penetrant, allowing the penetrant to penetrate for a certain period of time, removing excess penetrant, and ultraviolet inspection. The part is inspected with a UV light, which reveals cracks into which the penetrant has flowed, making the defects visible.

[0063] In an exemplary embodiment, method 1100 can include removing a tip portion of the airfoil at (1106). This forms a machined surface to which an exchange tip portion can be additively manufactured. The removal at (1106) can be performed using a conventional machining process (such as turning, milling, drilling, grinding, boring, broaching, electrical discharge machining (EDM), electron beam machining (EBM), laser cutting, waterjet cutting, chemical mechanical machining, ultrasonic machining, or other machining processes).

[0064] Before or after step 1106, method 1100 can include, at (1108), manually welding and blending flush a local crack (or defect) in the airfoil to make it flush. This can include filling the local defect in the airfoil with a welding material and finishing it smoothly (e.g., grinding, sanding, or other smooth finishing techniques). By finishing the welded defect flush, it is possible to ensure that there are no protrusions between the surface of the airfoil and the welded defect.

[0065] In many embodiments, method 1100 can include, at (1110), additively manufacturing an extension segment onto the machined surface of the airfoil. This can be performed by an additive manufacturing system (such as additive manufacturing system 200 described above with reference to FIG. 9). The extension segment substantially matches the contour of the removed portion of the airfoil, but some final machining / smoothing (blending) is required to bring the airfoil back within the design specifications. Thus, method 1100 can include, at (1112), machining the extension segment to form a replacement tip portion. The machining at (1112) can be performed using conventional machining processes (such as turning, milling, drilling, grinding, boring, broaching, electrical discharge machining (EDM), electron beam machining (EBM), laser cutting, waterjet cutting, chemical mechanical machining, ultrasonic machining, or other machining processes). Further, method 1100 can include, at (1114), smoothly finishing the replacement tip portion to be flush with the airfoil 104, thereby making it possible to ensure that there are no protrusions at the contacting portion between the replacement tip portion and the airfoil. Smoothly finishing can include sanding or other techniques.

[0066] In various embodiments, method 1100 can include, at (1116), reopening the tip cooling holes. For example, during the removal step, the tip cooling holes may have been partially removed, such that during the additive manufacturing step, the tip cooling holes are covered by the extension segments. Thus, the tip cooling holes can be reopened by removing a portion of the extension segments. Removing a portion of the extension segments can include machining (such as drilling or boring) the tip cooling holes. In some implementations, removing a portion of the extension segments to reopen the tip cooling holes can include using an EDM process. Thereafter, the method can include, at (1118), checking the diameter of the cooling holes using a reference pin. For example, this can include inserting a reference pin into the cooling holes such that the diameter of the cooling holes is reliably within the desired range. If the diameter of the cooling holes is not reliably within the desired range, the cooling holes require additional machining. In many implementations, method 1100 can include, at (1120), post-weld heat treatment. This can include heating the airfoil to a set temperature to relieve stress. Finally, method 1100 can include, at (1122), performing a post-weld fluorescent penetrant inspection (FPI) on the airfoil using a similar process as described above with respect to step 1104.

[0067] Referring to FIG. 12, a flowchart of an embodiment of a method 1200 for repairing an airfoil of a turbine component is shown in accordance with an embodiment of the present subject matter. Generally, in this specification, the method 1200 will be described with reference to the turbine component 100, the airfoil 104, and the additive manufacturing system 200 described above with reference to FIGS. 1 - 10. However, those skilled in the art will understand that the disclosed method 1200 can generally be used in any turbine component and / or with respect to an additive manufacturing system having other suitable system configurations. Additionally, in FIG. 12, steps are shown being performed in a particular order for purposes of illustration and description, but the methods described herein are not limited to a particular order or sequence unless otherwise specified in the claims. Those skilled in the art will understand that, using the disclosure herein, various steps of the methods disclosed herein can be omitted, rearranged, combined, and / or adapted in various ways without departing from the scope of the present disclosure. The dashed boxes indicate optional steps of the method 1200.

[0068] The method 1200 can be a method for repairing 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 the tip portion of the tip rail may be out of the design specification range. For example, in operation, the airfoil including the tip rail is exposed to high-temperature combustion gases, subjected to vibration due to operation, and mechanical forces, and thus the tip portion may be out of the design specification range. Specifically, the tip portion may lose material over time and / or distort over time due to its operation and exposure to combustion gases, whereby the tip portion of the tip rail may be out of the design specification range (which is the range where peak efficiency occurs).

[0069] Method 1200 can include, at (1202), removing a tip portion of the tip rail such that a machined surface is defined at a radially outer end of the airfoil. As a result, after removing the tip portion, at least one of the plurality of tip cooling passages extends to an opening of the machined surface (e.g., in some implementations all of the tip cooling passages extend to the opening of the machined surface, and in other embodiments a portion of the tip cooling passages extend to the opening of the machined surface). In many implementations, prior to the removing step being performed at (1202), each of the plurality of tip cooling passages includes a through-hole and a counterbore extending from the through-hole, the counterbore being wider than the through-hole in the radial direction. In such an implementation, method 1200 can include removing the tip portion of the tip rail such that the counterbore extends radially to the opening of the machined surface. In various implementations, method 1200 can include removing the tip portion of the tip rail such that an upper segment of the counterbore is removed and a lower segment of the counterbore extends radially to the opening of the machined surface.

[0070] More specifically, prior to the removing step being performed, the counterbore has a radial height prior to machining. In such an embodiment, the method can include removing the tip portion of the tip rail such that the remaining radial height of the counterbore is a height between about 40% and about 60% of the radial height prior to machining, a height between about 45% and about 55% of the radial height prior to machining, or a height of about 50%, etc.

[0071] In an exemplary implementation, method 1200 may include, at (1206), additively manufacturing an extension segment across the machined surface and the openings (or across all openings in an embodiment where each tip cooling hole is exposed after removing the tip portion). In many implementations, the additive manufacturing at (1206) is performed using an additive manufacturing system. The additive manufacturing system can include a vision system, a control system, and a user interface operably connected to an additive welder. In such an embodiment, method 1200 may include, at (1204), after the removing step, positioning a digital marker between two adjacent openings in the digital representation of the machined surface. The digital representation is obtained by the vision system. The positioning at (1204) may be performed manually by a user using the user interface or automatically by the control system. The positioning at (1204) can be performed after the removal at (1202) and before the additive manufacturing at (1206). For example, the digital marker can be positioned after the removal step because the openings are exposed and thus the vision system can recognize the openings. This is advantageous because it can improve the accuracy and precision of the additive manufacturing step, and as a result, reduce defects in the printed extension segment.

[0072] In various embodiments, method 1200 may include, at (1208), machining the extension segment to form a replacement tip portion within the design specification range of the tip rail. Further, method 1200 may include, at (1210), reopening at least one of the plurality of tip cooling passages (e.g., by removing a portion of the extension segment).

[0073] Importantly, in an exemplary embodiment, prior to removal at (1202) and prior to additive manufacturing at (1206), ensure that the welding material is not placed in the tip cooling passages (e.g., counterbore holes and / or through holes). This is advantageous because the openings become visible on the machined surface, allowing the digital marker to be positioned relative to the openings, and as a result, the extension segments can be additively manufactured more efficiently.

[0074] FIG. 13 shows a block diagram of an exemplary computing system 600. The computing system 600 can be used to implement the aspects disclosed herein. The computing system 600 can include one or more computing devices 602. The control system 206 described above with reference to FIG. 9 can be constructed and operate in the same or a similar manner as one of the one or more computing devices 602, for example.

[0075] As shown in FIG. 13, each of the one or more computing devices 602 can include one or more processors 604 and one or more memory devices 606. The one or more processors 604 can include any suitable processing device (such as a microprocessor, a microcontroller, an integrated circuit, a logic device, or other suitable processing device). The one or more memory devices 606 can include one or more computer-readable media (one or more non-transitory computer-readable media, RAM, ROM, hard drives, flash drives, and other memory devices (such as one or more buffer devices), but are not limited thereto).

[0076] One or more memory devices 606 can store information accessible by one or more processors 604 (including computer-readable instructions or computer-executable instructions 608 executable by one or more processors 604). The instructions 608 can be a set of instructions or control logic that, when executed by one or more processors 604, can cause one or more processors 604 to perform operations. The instructions 608 can be software written in any suitable programming language or can be implemented in hardware. In some embodiments, the instructions 608 are executed by one or more processors 604 and can cause one or more processors 604 to perform operations.

[0077] The memory device 606 can store data 610 accessible by the processor 604. For example, the data 610 can include sensor data such as engine parameters, model data, logic data, etc., as described herein. The data 610 can include one or more tables, functions, algorithms, models, equations, etc., according to exemplary embodiments of the present disclosure.

[0078] One or more computing devices 602 can also include, for example, a communication interface 612 used to communicate with other components of the additive manufacturing system. The communication interface 612 can include any suitable components (e.g., a transmitter, a receiver, a port, a controller, an antenna, or other suitable components, etc.) for connecting to one or more networks.

[0079] The technology described in this specification refers to computer-based systems, actions performed by computer-based systems, and information sent to and from computer-based systems. One of ordinary skill in the art can understand that due to the inherent flexibility of computer-based systems, a wide variety of configurations, combinations, and divisions of tasks and functions among components are possible. For example, the processes described in this specification can be implemented using a single computing device or multiple computing devices operating in combination. Databases, memories, instructions, and applications can be implemented in a single system or distributed across multiple systems.

[0080] The specific features of various embodiments may be shown in some drawings and not in others, but this is for convenience only. In accordance with the principles of the present invention, any feature of one drawing can be referred to in combination with and / or recited in the claims in combination with any feature of another drawing.

[0081] The description provided herein discloses the present invention (including the best mode) using examples, and also enables one of ordinary skill in the art to practice the present invention (including manufacturing and using any device or system and performing any method incorporated therein). The patentable scope of the present invention is defined by the claims and can include other embodiments that occur to one of ordinary skill in the art. Such other embodiments are intended to be within the scope of the claims if they include structural elements that are not different from the literal language of the claims or equivalent structural elements that are not substantially different from the literal language of the claims.

[0082] Further aspects of the present invention are provided by the following embodiments. [Embodiment 1] A method for repairing an airfoil of a turbine component, wherein the airfoil includes a tip rail that at least partially defines a plurality of tip cooling passages, the turbine component has undergone at least one operating cycle, a tip portion of the tip rail is outside a design specification range, and the method includes removing the tip portion of the tip rail such that a machined surface is defined at a radially outer end of the airfoil, after the tip portion is removed, at least one of the plurality of tip cooling passages extends to an opening of the machined surface, removing the tip portion of the tip rail, adding a build segment to the machined surface, and machining the build segment to form a replacement tip portion within the design specification range of the tip rail. [Embodiment 2] Before the removing step is performed, each of the plurality of tip cooling passages includes a through hole and a counterbore extending from the through hole and radially wider than the through hole, and the removing step further includes removing the tip portion of the tip rail such that the counterbore extends radially to an opening of the machined surface. The method according to Embodiment 1. [Embodiment 3] Before the removing step is performed, the counterbore defines a pre-machining radial height, and the removing step includes removing the tip portion of the tip rail to set the remaining radial height of the counterbore to a height between about 40% and about 60% of the pre-machining radial height. The method according to Embodiment 1 or 2. [Embodiment 4] Before the step of removing is performed, each of the plurality of tip cooling passages includes a through hole and a counterbore hole extending from the through hole and wider than the through hole in the radial direction. The method further includes removing a tip portion of the tip rail such that an upper segment of the counterbore hole is removed and a lower segment of the counterbore hole extends radially to an opening of the machining surface, adding manufacturing the extension segment across the machining surface and the opening, and removing a portion of the extension segment corresponding to the upper segment of the counterbore hole to restore the counterbore hole, according to the method described in any of Embodiments 1 to 3. [Embodiment 5] Each of the plurality of tip cooling passages includes a through hole and a counterbore hole extending from the through hole and wider than the through hole in the radial direction. The method further includes, after the step of adding manufacturing, opening the counterbore hole again by removing a part of the extension segment, according to the method described in any of Embodiments 1 to 4. [Embodiment 6] Before the step of removing is performed and before the step of adding manufacturing is performed, no welding material is disposed in the plurality of tip cooling passages, according to the method described in any of Embodiments 1 to 5. [Embodiment 7] The method further includes welding a defect of the tip rail to generate a welded defect and smoothly finishing the welded defect to be flush with the tip rail, according to the method described in any of Embodiments 1 to 6. [Embodiment 8] The adding manufacturing is performed using an adding manufacturing system. The adding manufacturing system includes an additive welder and a vision system operably connected to a control system. The method further includes positioning a digital marker between two adjacent openings in a digital representation of the machining surface after the step of removing, according to the method described in any of Embodiments 1 to 7. [Embodiment 9] The step of positioning is after the step of removing and before the step of additive manufacturing, and is the method according to any one of Embodiments 1 to 8. [Embodiment 10] A method for repairing an airfoil of a turbine component, the airfoil including a tip rail that at least partially defines a plurality of tip cooling passages, the turbine component having undergone at least one operating cycle, a tip portion of the tip rail being outside a design specification range, the method comprising removing a tip portion of the tip rail such that a machined surface is defined at a radially outer end of the airfoil, after the tip portion has been removed, at least one of the plurality of tip cooling passages extending to an opening of the machined surface, removing the tip portion of the tip rail, additive manufacturing an extension segment across the machined surface and the opening, machining the extension segment to form a replacement tip portion within the design specification range of the tip rail, and reopening at least one of the plurality of tip cooling passages. [Embodiment 11] Before the removing step is performed, each of the plurality of tip cooling passages includes a through hole and a counterbore extending from the through hole and spreading radially wider than the through hole, and the removing step further includes removing the tip portion of the tip rail such that the counterbore extends radially to the opening of the machined surface, and is the method according to any one of Embodiments 1 to 10. [Embodiment 12] Before the removing step is performed, the counterbore defines a pre-machining radial height, and the removing step further includes removing the tip portion of the tip rail to set the remaining radial height of the counterbore to a height between about 40% and about 60% of the pre-machining radial height, and is the method according to any one of Embodiments 1 to 11. [Embodiment 13] Before the step of removing is performed, each of the plurality of tip cooling passages includes a through hole and a counterbore hole that extends from the through hole and extends radially wider than the through hole. The method further includes removing a tip portion of the tip rail such that an upper segment of the counterbore hole is removed and a lower segment of the counterbore hole extends radially to an opening of the machining surface, adding manufacturing the extension segment across the machining surface and the opening, and removing a portion of the extension segment corresponding to the upper segment of the counterbore hole to restore the counterbore hole, the method according to any one of Embodiments 1 to 12. [Embodiment 14] Each of the plurality of tip cooling passages includes a through hole and a counterbore hole that extends from the through hole and extends radially wider than the through hole. The method further includes, after the step of adding manufacturing, opening the counterbore hole again by removing a part of the extension segment, the method according to any one of Embodiments 1 to 13. [Embodiment 15] Before the removing step is performed and before the step of adding manufacturing, no welding material is disposed in the plurality of tip cooling passages, the method according to any one of Embodiments 1 to 14. [Embodiment 16] The method further includes welding a defect of the tip rail to generate a welded defect, and smoothly finishing the welded defect to be flush with the tip rail, the method according to any one of Embodiments 1 to 15. [Embodiment 17] The adding manufacturing is performed using an additive manufacturing system, the additive manufacturing system includes an additive welder and a vision system operably connected to a control system. The method further includes, after the step of removing, positioning a digital marker between two adjacent openings in a digital representation of the machining surface, the method according to any one of Embodiments 1 to 16. [Embodiment 18] The step of positioning is the method according to any one of Embodiments 1 to 17, which is performed after the step of removing and before the step of additive manufacturing.

Explanation of Reference Numerals

[0083] 12 Compressor section 14 Compressor 16 Inlet section 18 Combustion section 20 Combustor 21 Rotor disk 22 Turbine section 23 Rotor blade 24 Shaft 26 Stationary nozzle 27 Rotor disk 28 Rotor blade 30 Axial center line 32 Outer casing 34 Exhaust diffuser 36 Ambient air 38 Compressed air 40 Combustion chamber 42 Combustion gas 44 Support column 100 Turbine component 102 Platform 104 Airfoil 106 Doubletail 110 Pressure side wall 112 Leading edge 116 Root section 118 Tip 124 Tip cavity 125 Cap 126 Floor 128 Pressure side part 130 Pressure side part 132 Film cooling hole 134 Trailing edge discharge hole 136 Tip cooling passage 138 Tip shelf 140 Floor 142 Shelf output section 146 End milling hole 148 Through-hole 150 Outer surface 151 Opening 152 Height 153 Outer surface 158 Processing stop line 160 New material 162 Extension segment 170 Opening 172 Tip portion 174 Height 176 Upper segment 178 Bottom segment 179 New upper segment 180 Defect 182 Defect 184 Replacement tip portion 186 Height 202 Visual system 206 Control system 208 User interface 210 Management system 212 Camera 214 Field of view 216 Workpiece 218 Shaping plate 222 Shaping surface 224 Powder supply chamber 226 Powder 228 Shaping chamber 230 Powder piston 232 Powder floor 234 Recoater 236 Working surface 238 Shaping platform 240 Chuck system 242 Energy source 244 Energy beam 246 Scanner 248 Shaping piston 300 Digital representation 302 Digital marker 600 Computing system 602 Computing device 604 Processor 608 Instruction 610 Data 612 Communication Interface 1100 Method 1104 Step 1106 Step 1200 Method

Claims

1. 1. A method of repairing an airfoil of a turbine component, the airfoil including a tip rail at least partially defining a plurality of tip cooling passages, the turbine component having undergone at least one operating cycle and a tip portion of the tip rail being outside of design specifications, the method comprising: removing a tip portion of the tip rail to define a work face at a radially outer end of the airfoil, wherein after the tip portion is removed, at least one tip cooling passage of the plurality of tip cooling passages extends to an opening in the work face; Additively manufacturing an extension segment on the work surface; and machining the extension segment to form a replacement tip portion within the design specifications of the tip rail. A method comprising:

2. Before the removing step is performed, each tip cooling passage of the plurality of tip cooling passages includes a through hole and a counterbore extending from the through hole and radially wider than the through hole, and the removing step further comprises: removing a tip portion of the tip rail such that the counterbore extends radially to an opening in the work surface. The method of claim 1 , comprising:

3. Before the removing step is performed, the counterbore defines a pre-machined radial height, and the removing step includes:

3. The method of claim 2 including removing a tip portion of the tip rail to provide a remaining radial height of the counterbore that is between about 40% and about 60% of its pre-machined radial height.

4. Before the removing step is performed, each tip cooling passage of the plurality of tip cooling passages includes a through hole and a counterbore extending from the through hole and radially larger than the through hole, the method further comprising: removing a tip portion of the tip rail such that an upper segment of the counterbore is removed and a lower segment of the counterbore extends radially to an opening in the work surface; additively manufacturing the extension segment across the work surface and the opening; and removing a portion of the extension segment corresponding to an upper segment of the counterbore to restore the counterbore. The method of claim 1 , comprising:

5. Each tip cooling passage of the plurality of tip cooling passages includes a through hole and a counterbore extending from the through hole and radially larger than the through hole, the method further comprising: Re-opening the counterbore by removing a portion of the extension segment after the additive manufacturing step. The method of claim 1 , comprising:

6. The method of claim 1 , wherein no weld material is disposed in the plurality of tip cooling passages before the removing step is performed and before the additively manufacturing step is performed.

7. The method further comprises: welding the defect in the tip rail to create a welded defect; and smoothing the welded defect flush with the tip rail. The method of claim 1 , comprising:

8. The additive manufacturing is performed using an additive manufacturing system, the additive manufacturing system including an additive welder and a vision system operably connected to a control system, the method further comprising: After the removing step, positioning a digital marker between two adjacent openings in the digital representation of the work surface. The method of claim 1 , comprising:

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

10. 1. A method of repairing an airfoil of a turbine component, the airfoil including a tip rail at least partially defining a plurality of tip cooling passages, the turbine component having undergone at least one operating cycle and a tip portion of the tip rail being outside of design specifications, the method comprising: removing a tip portion of the tip rail to define a work face at a radially outer end of the airfoil, wherein after the tip portion is removed, at least one tip cooling passage of the plurality of tip cooling passages extends to an opening in the work face; additively manufacturing an extension segment across the work surface and the opening; machining the extension segment to form a replacement tip portion within the design specifications of the tip rail; and reopening at least one tip cooling passage of the plurality of tip cooling passages. A method comprising:

11. Before the removing step is performed, each tip cooling passage of the plurality of tip cooling passages includes a through hole and a counterbore extending from the through hole and radially wider than the through hole, and the removing step further comprises: removing a tip portion of the tip rail such that the counterbore extends radially to an opening in the work surface. The method of claim 10, comprising:

12. Before the removing step is performed, the counterbore defines a pre-machined radial height, and the removing step further comprises:

12. The method of claim 11 including removing a tip portion of the tip rail to provide a remaining radial height of the counterbore that is between about 40% and about 60% of its pre-machined radial height.

13. Before the removing step is performed, each tip cooling passage of the plurality of tip cooling passages includes a through hole and a counterbore extending from the through hole and radially larger than the through hole, the method further comprising: removing a tip portion of the tip rail such that an upper segment of the counterbore is removed and a lower segment of the counterbore extends radially to an opening in the work surface; additively manufacturing the extension segment across the work surface and the opening; and removing a portion of the extension segment corresponding to an upper segment of the counterbore to restore the counterbore. The method of claim 10, comprising:

14. Each tip cooling passage of the plurality of tip cooling passages includes a through hole and a counterbore extending from the through hole and radially larger than the through hole, the method further comprising: Re-opening the counterbore by removing a portion of the extension segment after the additive manufacturing step. The method of claim 10, comprising:

15. The method of claim 10 , wherein no weld material is disposed in the plurality of tip cooling passages before the removing step is performed and before the additive manufacturing step is performed.

Images