Brazed Joint for a Component and Method of Forming the Same

Abstract

The present invention is titled "Brazed Joints for Components and Methods of Forming the Same". The present invention discloses a system (200, 300, 400, 500) for forming a brazed joint (202). The system includes an environment (206) that is operable to reach a brazing temperature sufficient to melt at least a portion of a brazing material (218). The system further includes a component (204) within the environment (206), the component (204) including a base (210) having a base surface (212), a recess (214) that extends from the base surface (212) and droops into an inner edge (224) of the base (210), and the brazing material (218) that forms a lid (220) within the recess (214) and above the base surface (212). The brazing material (218) fills the recess (214) from the lid (220) to the inner edge (224). The lid (220) has an exposed brazing surface (222). The system further includes an insulating layer (302) that at least partially covers the exposed brazing surface (222).

Description

BACKGROUND OF THE DISCLOSURE

[0001] The field of the present disclosure generally relates to brazed joints for metal alloys and more particularly to thermal control of brazing processes.

[0002] For at least some known components that are made entirely or partially of metal alloys, cracks or defects may occur in the alloys during normal use of the components. For example, at least some known rotating machinery uses stainless steels and nickel-based, cobalt-based, and iron-based superalloys in components used in the heat flow path of the rotating machinery during operation. The heat flow path subjects the components to thermal and / or mechanical stresses and strains. Thus, when cracks or defects occur in the alloys of these components, the repaired cracks or defects must be able to similarly withstand the high temperatures, stresses, and strains of the heat flow path.

[0003] One known method of repairing cracks or defects in alloys is to form a brazed joint using a brazing process. For some known nickel-based superalloys, such as Rene’ N5, Rene’ 108, and (registered trademarks of Cannon Muskegon Corporation), using brazing is a typical technique for salvaging damaged parts. In a conventional brazing process, a brazing material is used to repair a defect in an existing component by filling a gap with a liquid or partially liquid brazing material and then allowing the brazing material to solidify. At least one known brazing method includes cleaning the defective surface to be joined, placing the component having the defect in a vacuum brazing furnace, and heating the furnace to a target temperature such that the brazing material becomes molten or partially molten, thereby allowing the brazing material to flow into the space forming the defect. The brazing process can be used to fill a gap between two components to join them together, or the brazing material can be used to form a new component.

[0004] In at least some of the known brazing processes for forming a brazed joint, as the brazing material begins to cool after filling a defect in a component, solidification shrinkage occurs within the joint. In addition, in at least some known brazed joints, as the brazing material cools, the brazing material closer to the surface of the metal alloy cools faster than the brazing material deeper within the defect. When combined with solidification shrinkage, this differential cooling can cause solidification defects such as a brazed joint with high porosity and / or hot cracks. In at least some known brazing processes, porosity may form when the gap filled with the brazing material is greater than 0.1 mm and the brazing material is a blend of superalloy powder and a much lower melting point brazing filler. In at least some known brazing processes, hot cracks may occur when the gap filled with the brazing material is less than 0.1 mm and the brazing material is a pure brazing filler. These defects in the brazed joint can reduce the tensile strength and shorten the creep life and fatigue life of the brazed joint, resulting in increased wear of the alloy-containing component, which can cause forced shutdown of the turbine or additional wear of other internal components. These problems associated with defects in the brazed joint can be particularly problematic for components designed for high stress regions such as within the hot flow path of a rotating engine. SUMMARY OF THE INVENTION

[0005] In one aspect, a system for forming a brazed joint is provided. The system includes an environment capable of operating to reach a brazing temperature sufficient to melt at least a portion of a brazing material. The system also includes a component within the environment, the component including a base having a base surface, a recess that droops from the base surface into the base to an inner edge, and a brazing material within the recess and forming a cap above the base surface. The brazing material fills the recess from the cap to the inner edge. The cap has an exposed brazing surface. The system also includes an insulating layer at least partially covering the exposed brazing surface.

[0006] In another aspect, a method for brazing a recess defined within a base is provided. The recess droops from a surface of the base to an inner edge within the base. The method includes forming a cap of brazing material above the recess. The cap has an exposed brazing surface. The method also includes positioning a thermal insulating layer above the exposed brazing surface. The method also includes heating the brazing material within the environment to form at least a partially molten brazing material. The method also includes cooling the at least partially molten brazing material to form a solid state brazed joint within the recess.

[0007] In another aspect, a method for brazing a recess defined within a base is provided. The recess droops from a base surface of the base to an inner edge within the base. The method includes supplying at least a partially molten brazing material from the cap to the inner edge within the recess. The method also includes extracting heat from a location on the base that is closer to the inner edge of the recess than to the cap. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] These and other features, aspects, and advantages of the present disclosure will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters represent like parts throughout the drawings, wherein:

[0009] Figure 1 is a schematic view of an exemplary rotating machine;

[0010] Figure 2 is a cross-sectional view of an exemplary system for forming a brazed joint within a component;

[0011] Figure 3 is a cross-sectional view of another exemplary system for forming a brazed joint within a component;

[0012] Figure 4 is a cross-sectional view of another exemplary system for forming a brazed joint within a component;

[0013] Figure 5 is a cross-sectional view of another exemplary system for forming a brazed joint within a component;

[0014] Figure 6 is a flow chart of an exemplary method for forming a brazed joint; and

[0015] Figure 7 is a flow chart of another exemplary method for forming a brazed joint.

[0016] Unless otherwise specified, the drawings provided herein are intended to illustrate the features of embodiments of the present disclosure. It is believed that these features are applicable to a variety of systems including one or more embodiments of the present disclosure. Accordingly, the drawings are not intended to include all conventional features known to those of ordinary skill in the art that are required to practice the embodiments disclosed herein. DETAILED DESCRIPTION

[0017] In the following specification and claims, a number of terms will be used, and these terms should be defined to have the following meanings.

[0018] Unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" include plural references.

[0019] Unless otherwise indicated, approximate language, such as "substantially", "essentially", and "about", as used herein, indicates that the term so modified can vary only within a degree of approximation that would be recognized by one of ordinary skill in the art, rather than an absolute or perfect degree. Thus, values modified by one or more terms, such as "about", "approximately", and "substantially", are not limited to the precise values specified. In at least some instances, the approximate language may correspond to the precision of the instrument used to measure the value. Throughout this specification and the claims, range limitations may be identified. Unless the context or language indicates otherwise, these ranges may be combined and / or interchanged and include all sub-ranges subsumed therein. In addition, unless otherwise indicated, the terms "first", "second", etc. are used herein only as labels and are not intended to impose an order, position, or ranking requirement on the items to which these terms refer. Moreover, for example, a reference to a "second" item does not require or preclude the existence of a "first" or lower-numbered item or a "third" or higher-numbered item, for instance.

[0020] The systems and methods described herein relate to forming a brazed joint within a component. Specifically, in an exemplary embodiment, the system includes an environment capable of operating to reach a brazing temperature sufficient to melt at least a portion of a brazing material. The system further includes a component within the environment, the component including a base having a base surface, a recess that extends from the base surface and droops into the base to an inner edge, and a brazing material that forms a lid within the recess and above the base surface. The brazing material fills the recess from the lid to the inner edge. The lid has an exposed brazing surface. In some embodiments, the system further includes an insulating layer that at least partially covers the exposed brazing surface of the lid. After the environment is heated to the brazing temperature, the system promotes less rapid heat dissipation from the exposed brazing surface of the lid compared to a system without the insulating layer. In addition or alternatively, the system includes a cooling system capable of operating to extract heat from the base at a location closer to the inner edge of the recess than to the lid, which facilitates more rapid cooling of the brazed joint compared to the exposed brazing surface of the lid. Thus, during the brazing process, the system facilitates the formation of a brazed joint within the recess with fewer or no solidification defects relative to the lid extending above the base surface.

[0021] Figure 1For an exemplary rotary machine 100 (i.e., a turbine), and more specifically a schematic diagram of a turbine engine. In an exemplary embodiment, the rotary machine 100 is a gas turbine engine. Alternatively, the rotary machine can be any other turbine engine and / or rotary machine, including but not limited to steam turbine engines, gas turbine fan aircraft engines, other aircraft engines, wind turbines, compressors, and pumps. In an exemplary embodiment, the turbine engine 100 includes an intake section 102, a compressor section 104 coupled downstream of the intake section 102, a burner section 106 coupled downstream of the compressor section 104, a turbine section 108 coupled downstream of the burner section 106, and an exhaust section 110 coupled downstream of the turbine section 108. The turbine section 108 is coupled to the compressor section 104 via a rotor shaft 112. It should be noted that as used herein, the term "coupled" is not limited to a direct mechanical, thermal, electrical, and / or fluid communication connection between components, and can also include an indirect mechanical, thermal, electrical, and / or fluid communication connection between multiple components. In an exemplary embodiment, the burner section 106 includes a plurality of burners 114. The burner section 106 is coupled to the compressor section 104 such that each burner 114 is in fluid communication with the compressor section 104. The rotor shaft 112 is also coupled to a load 116, such as but not limited to a generator and / or a mechanical drive application. In an exemplary embodiment, each of the compressor section 104 and the turbine section 108 includes at least one rotor assembly 118 coupled to the rotor shaft 112. Each rotor assembly 118 of the turbine section 108 includes a plurality of circumferentially extending, radially extending turbine blades 119.

[0022] In operation, the intake section 102 conveys air 120 towards the compressor section 104. The compressor section 104 compresses the inlet air 120 to a higher pressure and then discharges the compressed air 122 towards the burner section 106. The compressed air 122 is conveyed to the burner section 106 where it is mixed with fuel (not shown) and burned to produce high-temperature combustion gases 124. The combustion gases 124 are conveyed downstream towards the turbine section 108 and impinge on the turbine blades 119, converting the thermal energy into mechanical rotational energy for driving the rotor assembly 118 to rotate about a longitudinal axis 126. Generally, the burner section 106 and the turbine section 108 are referred to as the hot gas section 109 of the turbine engine 100. The exhaust gas 128 is then discharged to the ambient atmosphere via the exhaust section 110.

[0023] In some embodiments, during operation of the turbine engine 100, components 204 of the hot gas section 109 (such as but not limited to turbine blades 119, which may include stator blades (not shown) and shrouds (not shown)) can be exposed to temperatures up to, for example, 1250 degrees Celsius, thereby generating thermal stresses. In the turbine section 108, components 204 are also subjected to mechanical stresses during operation, such as stresses from high-speed rotation and the high-speed hot gas propulsion from the burner 106. Such extreme operating conditions can cause cracks to form within components 204 of the hot gas section 109 due to creep and / or fatigue and other defects, requiring repair.

[0024] Figure 2 is a cross-sectional view of a system 200 for forming a brazed joint 202 within one or more of the components 204. Although, for illustrative purposes, the component 204 is described as a component of the rotating machine 100, it should be understood that the system 200 is also contemplated for forming brazed joints within any suitable component 204 in a variety of applications and is not limited to use with the components of the rotating machine 100 described herein.

[0025] In some embodiments, the component 204 is formed from a metal alloy used within the hot gas section 109 or the burner 106 of the turbine engine 100. In some such embodiments, the component 204 is made from a cobalt-based or nickel-based superalloy. For example, the component 204 can be made from a single-crystal nickel-based superalloy such as made. In alternative embodiments, the component 204 is formed from any alloy that can be brazed using the systems and methods described herein.

[0026] The system 200 includes an environment 206 for forming the brazed joint 202. In some embodiments, the environment 206 is a chamber defined within a heating compartment 208. In an exemplary embodiment, the heating compartment 208 is a vacuum furnace that is configured to supply both heat and a vacuum to the chamber during the brazing process. For example, the heating compartment 208 is configured to supply a uniform temperature within the environment 206 and to draw a sufficient vacuum within the environment 206 to remove at least some of the gases present within the environment 206. In one embodiment, such gases include oxygen, nitrogen, carbon dioxide, water vapor, and methane. In alternative embodiments, the environment 206 is any suitable environment that allows for the formation of a brazed joint within the component 204 as described herein.

[0027] Component 204 includes a base 210 having a base surface 212 and a recess 214 that extends inwardly from the base surface 212 by a recess depth 216 to an inner edge 224. In an exemplary embodiment, the recess 214 represents a defect in the base 210 that may occur during normal use of the component 204, such as a crack. The inner edge 224 represents the innermost or deepest extent of the crack starting from the base surface 212. For example, in an embodiment where the component 204 is formed of a metal alloy used within the hot gas section 109 of a turbine engine 100, the recess 214 may be formed due to a combination of rotational stress, forces from rapidly flowing hot gas streams, and / or cyclic thermo-mechanical strain on the component 204. In an alternative embodiment, the recess 214 may be formed by another process, such as intentionally or inadvertently during the casting or machining process of the component 204, or by a joint that joins two separately formed components 204 together.

[0028] The brazed joint 202 is formed by a brazing material 218. In one embodiment, the brazing material 218 includes a pure brazing filler alloy, such as a DF-4B diffusion brazing alloy. The brazing filler alloy may include one or more of aluminum, silicon, copper, silver, germanium, gold, nickel, cobalt, and boron. In an exemplary embodiment, the brazing alloy is a multi-component eutectic that has a relatively low melting point compared to the component 204. For example, brazing alloys for components 204 formed of cobalt-based superalloys and nickel-based superalloys typically have a melting temperature of less than 1120 degrees Celsius, and more specifically between 900 degrees Celsius and 1100 degrees Celsius. In another embodiment, the brazing material 218 includes a blend of brazing powder and brazing filler alloy. The brazing powder is typically a superalloy for the component 204 and has a higher strength and a higher melting point compared to the brazing filler alloy. Thus, at certain temperatures, the brazing alloy is molten while the brazing powder is solid, thereby forming a partially molten brazing material 218. In an alternative embodiment, the brazing material 218 may consist entirely or substantially of the brazing filler alloy, or may include other materials that allow the brazed joint 202 to be formed as described herein.

[0029] In one embodiment, the brazing material 218 includes a brazing filler alloy and brazing powder that are mixed with a binder to produce a brazing paste. By way of example and not limitation, the brazing filler alloy and brazing powder are mixed with 8% binder. The brazing paste is semi-solid, which in some embodiments allows the brazing material 218 to be poured or injected into the recess 214. Such filling techniques are particularly suitable for recesses 214 wider than 0.1 mm. In an alternative embodiment, the brazing paste or pure brazing filler alloy may be placed over the recess 214 to form a cap 220 and allow the brazing material 218 to flow into the recess by capillary action. Such filling techniques are particularly suitable for recesses 214 equal to or narrower than 0.1 mm.

[0030] In some embodiments, during the brazing process, the environment 206 is heated to the brazing temperature. In some embodiments, the environment 206 is maintained at the brazing temperature for 10 minutes to 120 minutes. In some such embodiments, the environment 206 is maintained at the brazing temperature for 20 minutes to 40 minutes, and in some such embodiments, for 30 minutes. Alternatively, the environment 206 is maintained at the brazing temperature for any suitable length of time. The brazing temperature is below the melting temperature of the component 204 and high enough to cause the brazing material 218 to become molten or partially molten, as described above. In an exemplary embodiment where the brazing material 218 comprises a brazing paste, at the brazing temperature, the brazing alloy melts while the brazing powder remains solid, resulting in a partially molten brazing material 218. In some such embodiments, before heating the environment 206 to the brazing temperature, the solid or paste brazing material 218 is placed into the recess 214 to fill the recess from the inner edge 224 to the base surface 212. In some such embodiments, additional brazing material 218 is placed above the base surface 212 to form a cap 220. The cap 220 is in fluid communication with the brazing material 218 in the recess 214. The brazing material 218 is then heated to the brazing temperature, burning off most or all of the binder present and causing the brazing material 218 to become at least partially molten.

[0031] As described above, in an alternative embodiment, a solder paste or a pure solder alloy may be placed over the recess 214 to form a lid 220, and the solder material 218 is allowed to flow into the recess 214 by capillary action. Loading of the recess 214 may be carried out at room temperature or may be carried out by heating the environment 206 to the soldering temperature. In an exemplary embodiment, the solder material 218 is heated to the soldering temperature to form an exposed solder surface 222 on the at least partially molten lid 220, and a contact angle 219 is formed between the partially molten solder material 218 and the recess 214. In some such embodiments, the pure solder filler wets the base surface 212, the inner edge 224, and the other surfaces of the recess 214 and forms a contact angle 219 of less than 90 degrees. In additional embodiments, the contact angle 219 is less than or equal to 30 degrees, allowing the solder material to spread over the inner edge 224 and the other surfaces of the recess 214 and drawing the solder material 218 into the recess 214 by capillary action. In an alternative embodiment, the solder material 218 is completely molten at the soldering temperature. In an alternative or additional embodiment, the solder material 218 is placed in its partially molten state on the base surface 212 over the recess 214 and is allowed to feed into the recess 214 by capillary action. In additional embodiments, the solder material 218 may only fill a portion of the recess 214 such that once the solder material is heated to the soldering temperature in the environment 206, the lid 220 is drawn into the recess 214.

[0032] In some embodiments, after the solder material 218 reaches the soldering temperature, becomes at least partially molten, and completely fills the recess, the temperature in the environment 206 is reduced and the solder material 218 is allowed to cool to solidify the solder material 218, thereby forming a solder joint 202 within the recess 214. In some embodiments, the solidification of the solder material 218 causes the solder material 218 to shrink, which may result in solidification defects 228 in the solder joint 202. Some such solidification defects 228 include high porosity (in quantity and size) in the solid-state solder joint 202, such as Figure 2as shown by the hole 227 in. Other solidification defects 228 include linear indications or cracks, as shown by the linear indication 229. In some embodiments, when the base 210 and the brazing material 218 begin to cool, the temperature of the first portion 230 of the brazing material 218 located at or near the exposed brazing surface 222 decreases more rapidly than the temperature of the second portion 232 of the brazing material 218 located at or near the inner edge 224. When a portion of the brazing material 218 cools faster than another portion, such as the first portion 230 cooling faster than the second portion 232 in the environment 206, solidification shrinkage can cause the defect 228 to form. In this exemplary embodiment, since the first portion 230 cools faster than the second portion 232, the solidification defect 228 forms near the second portion 232 within the solidified brazing material 218. When the component 204 including the brazed joint 202 is put back into use, at least some of such known solidification defects 228 cause a reduction in the tensile strength of the brazed joint 202 and a shortening of the creep life and fatigue life.

[0033] In some embodiments, the size of the lid 220 compared to the size of the brazed joint 202 can affect the ability of the lid 220 to feed the shrinkage of the brazing material 218 within the recess 214 during cooling. In some such embodiments, the ratio of the modulus of the lid 220 to the modulus of the brazed joint 202 can be used to characterize how effectively the lid 220 feeds the brazed joint 202, where the modulus is defined as the volume of the geometry divided by the heat dissipation area of the geometry. For example, if the modulus ratio is less than 1.0, the brazing material 218 in the lid 220 starts and finishes solidifying earlier than the brazing material 218 in the recess 214 when cooled in the environment 206. In one embodiment, a ratio of the modulus of the lid 220 to the modulus of the brazed joint 202 greater than 1.0 effectively feeds the brazing material 218 into the recess 214 to at least partially compensate for shrinkage during cooling. In some embodiments, a ratio of the modulus of the lid 220 to the modulus of the brazed joint 202 greater than 1.1 effectively feeds the brazing material 218 into the recess 214 during cooling to at least partially compensate for shrinkage and reduce solidification defects 228. In additional embodiments, a ratio of the modulus of the lid 220 to the modulus of the brazed joint 202 greater than 1.5 is particularly effective at feeding the brazing material 218 into the recess 214 during cooling to at least partially compensate for shrinkage and reduce solidification defects 228. In an alternative embodiment, a ratio of the modulus of the lid 220 to the modulus of the brazed joint 202 greater than 1.5 feeds the brazing material 218 into the recess 214 during cooling to fully compensate for shrinkage and eliminate solidification defects 228 in the brazed joint 202. In addition or alternatively, increasing the contact angle 219 at the base surface 212 effectively increases the modulus of the lid 220, thereby increasing the feed of the brazing material 218 from the lid 220 to the recess 214 during cooling to at least partially compensate for shrinkage. In various embodiments, the size and contact angle 219 of the lid 220 vary to increase the feeding ability of the lid 220 into the recess 214 during cooling.

[0034] Figure 3A cross-sectional view of another exemplary embodiment of a system (designated as system 300) for forming a brazed joint 202 within a component 204. System 300 is similar to system 200, and thus, like components are labeled the same as those of system 200. System 300 differs from system 200 in that system 300 includes a thermal insulation layer 302 that at least partially covers the exposed brazing surface 222 of a cover 220 of a brazing material 218. In an exemplary embodiment, the thermal insulation layer 302 completely covers the cover 220 and a portion of the base surface 212. Similar to system 200, in system 300, the brazed joint 202 is formed by heating the brazing material 218 to a brazing temperature such that the brazing material 218 becomes at least partially molten and allows the brazing material 218 to enter the recess 214. In some embodiments of system 300, the thermal insulation layer 302 is placed over the exposed brazing surface 222 before the brazing material 218 is heated to the brazing temperature or after the brazing material 218 has been made at least partially molten such that the thermal insulation layer 302 at least partially covers the exposed brazing surface 222.

[0035] The thermal insulation layer 302 can include any material that allows the thermal insulation layer 302 to function as described herein. In some embodiments, the thermal insulation layer 302 is formed of one or more of ceramic materials, ceramic fibers, mineral wool, polycrystalline fibers, silica cloth, and any combination thereof.

[0036] Similar to system 200, in an exemplary embodiment of system 300, once component 204 has been heated in environment 206 for a sufficient time to form at least partially molten brazing material 218, environment 206 is allowed to cool from the brazing temperature. As environment 206 cools, base 210 and brazing material 218 also begin to cool, allowing brazing material 218 to solidify to form brazed joint 202. Different from system 200, in some embodiments, thermal insulation layer 302 causes the first portion 230 near cover 220 and brazing surface 222 to cool more slowly than the second portion 232 near inner edge 224. Due to the temperature difference between the first portion 230 and the second portion 232, the solidification of brazing material 218 starts and finishes earlier near the second portion 232 than near the first portion 230. Thus, when shrinkage occurs in brazing material 218 during solidification, any solidification defects 228 formed in brazing material 218 occur closer to the first portion 230 than to the second portion 232. More specifically, in the exemplary embodiment, thermal insulation layer 302 causes solidification defects 228 to mainly form near brazing surface 222 exposed in cover 220. Before component 204 is put back into use, cover 220 is removed or otherwise not designed to contribute to the strength of brazed joint 202. Thus, in some embodiments, solidification defects 228 in the first portion 230 of brazing material 218 do not significantly affect the performance of brazed joint 202.

[0037] As with system 200, in system 300, changing the size of cover 220 compared to the size of brazed joint 202, in combination with applying thermal insulation layer 302, can affect the ability of cover 220 to feed brazing material 218 into recess 214 to at least partially compensate for shrinkage during cooling. In some such embodiments, the ratio of the modulus of cover 220 to the modulus of brazed joint 202 can be used to characterize how effectively cover 220 feeds brazed joint 202. In some additional embodiments, thermal insulation layer 302 increases the modulus of cover 220 and thus increases its ratio to the modulus of brazed joint 202 when compared to the corresponding ratio of cover 220 without an insulation layer (such as cover 220 shown in system 200). In some such embodiments, thermal insulation layer 302 allows a cover 220 with a smaller width to provide the same feed of brazed joint 202 as a cover 220 with a larger width but without an insulation layer.

[0038] Figure 4A cross-sectional view of another exemplary embodiment of a system (designated as system 400) for forming a brazed joint 202 within a component 204. System 400 is similar to system 200, and thus, like components are labeled the same as in system 200. System 400 differs from system 200 in that system 400 includes a cooling device 401 that is operable to extract heat from a location 403 on a base 210. More specifically, location 403 is closer to the inner edge 224 of the recess 214 than to the cover 220.

[0039] In an exemplary embodiment, the cooling device 401 includes a thermally conductive element 402 that is in contact with location 403. Also in the exemplary embodiment, location 403 is a second base surface 404 of the base 210 that is positioned opposite the base surface 212. However, it should be understood that location 403 can be any location that is closer to the inner edge 224 of the recess 214 than to the cover 220. In other words, location 403 is selected such that the cooling device 401 enhances heat extraction from the second portion 232 of the brazing material 218 while having a lesser effect on the first portion 230 of the brazing material 218.

[0040] Similar to system 200, in an exemplary embodiment of system 400, after the component 204 has been heated in the environment 206 for a sufficient time to form at least a partially molten brazing material 218, the environment 206 is allowed to cool from the brazing temperature. In the exemplary embodiment, the thermally conductive element 402 is configured to extract heat from location 403 on the base 210 as the environment 206 cools. In an alternative embodiment, the thermally conductive element 402 is configured to extract heat from location 403 on the base 210 while the environment 206 is actively heating the environment 206 and then as the environment 206 cools. Because the thermally conductive element 402 is closer to the second portion 232 than to the first portion 230, the brazing material 218 cools more quickly near the second portion 232 than near the first portion 230. Due to the temperature difference between the first portion 230 and the second portion 232, solidification of the brazing material 218 occurs more quickly near the second portion 232 than near the first portion 230. Thus, when shrinkage occurs in the brazing material 218 during solidification, solidification defects 228 formed in the brazing material 218 occur closer to the first portion 230 than to the second portion 232. In the exemplary embodiment, the solidification defects 228 primarily form in the cover 220 near the exposed brazing surface 222. The cover 220 is removed or otherwise not designed to contribute to the strength of the brazed joint 202 before the component 204 is returned to service. Thus, the solidification defects 228 in the first portion 230 of the brazing material 218 do not significantly affect the performance of the brazed joint 202.

[0041] The heat conducting element 402 includes any heat conducting material and / or system that allows the heat conducting element to function as described herein. In some embodiments, the heat conducting element 402 includes a heat exchanger. The heat conducting element 402 can be, for example, a plate fin heat exchanger, a plate heat exchanger, or a tube heat exchanger. In additional embodiments, the heat conducting element 402 includes a graphite plate having embedded cooling channels connected to a cooling medium. In an alternative embodiment, the cooling device 401 includes any suitable structure that enables the system 400 to function as described herein.

[0042] Figure 5 FIG. is a cross-sectional view of another exemplary system (designated system 500) for forming a brazed joint 202 within the component 204. System 500 is similar to system 400, and thus, like components are labeled the same as those of system 400. System 500 differs from system 400 in that the cooling device 401 is implemented as an impingement manifold 502 that is configured to direct a fluid 504 to impinge on the base 210 at a location 403. As described above, the location 403 is selected such that the fluid 504 impinges on a portion of the base 210, bringing the fluid closer to the inner edge 224 of the recess 214 and the second portion 232 than to the cover 220, the exposed brazing surface 222, and the first portion 230. In the illustrated embodiment, the location 403 is also the second base surface 404 of the base 210 that is oppositely positioned from the base surface 212. Alternatively, the location 403 can be any location that is closer to the inner edge 224 of the recess 214 than to the cover 220.

[0043] Similar to system 200, in an exemplary embodiment of system 500, after component 204 has been heated in environment 206 for a sufficient time to form at least partially molten brazing material 218, environment 206 is allowed to cool from the brazing temperature. Impingement manifold 502 is configured to direct fluid 504 to extract heat from location 403 of base 210 while environment 206 is cooling. Since fluid 504 impinges on base 210 at location 403 closer to second portion 232 than to first portion 230, brazing material 218 cools faster near second portion 232 than near first portion 230. Due to the temperature difference between first portion 230 and second portion 232, solidification of brazing material 218 occurs faster near second portion 232 than near first portion 230. Thus, when shrinkage occurs in brazing material 218 during solidification, solidification defect 228 formed in brazing material 218 occurs closer to first portion 230 than to second portion 232. In an exemplary embodiment, solidification defect 228 forms primarily in cover 220 near exposed brazing surface 222. Before component 204 is returned to service, cover 220 is removed or otherwise not designed to contribute to the strength of brazed joint 202. Thus, solidification defect 228 in first portion 230 of brazing material 218 does not significantly affect the performance of brazed joint 202.

[0044] Impingement manifold 502 and the fluid 504 directed thereby include any thermal convection system and / or process that allows cooling device 401 to function as described herein. In some embodiments, impingement manifold 502 includes an injection nozzle connected to a source of fluid 504 (such as, a pressurized gas). In some such embodiments, fluid 504 includes one or more of argon, helium, hydrogen, and / or nitrogen.

[0045] Although insulation layer 302 ( Figure 3 shown) and cooling device 401 ( Figure 4 and Figure 5 shown) are shown above as being implemented separately, in some embodiments, additional advantages of reducing or eliminating solidification defect 228 of brazed joint 202 are obtained by implementing insulation layer 302 and cooling device 401 simultaneously. In other words, during the cooling phase after environment 206 has been heated to the brazing temperature, insulation layer 302 at least partially covers exposed brazing surface 222 of cover 220 while cooling device 401 (e.g., heat conduction element 402 or impingement manifold 502) operates to extract heat from location 403 of base 210, thereby further promoting faster solidification of brazing material 218 near second portion 232 than near first portion 230.

[0046] Figure 6is a flowchart of an exemplary method 600 of brazing a recess defined within a base, such as recess 214 defined within base 210 ( Figures 2 to 5 as shown). The recess extends from a base surface, such as base surface 212, to an inner edge within the base, such as inner edge 224. Method 600 includes forming 602 a cover of brazing material, such as brazing material 218, such as cover 220, over the recess. The cover has an exposed brazing surface, such as exposed brazing surface 222. Method 600 also includes positioning 604 a thermal insulation layer, such as thermal insulation layer 302, above the exposed brazing surface. Method 600 also includes heating 606 the brazing material within an environment, such as environment 206, to form at least partially molten brazing material. Method 600 also includes cooling 608 the at least partially molten brazing material to form a solid-state brazed joint, such as brazed joint 202.

[0047] In some embodiments in which the brazing material is a brazing paste that includes a brazing filler alloy, brazing powder, and a binder, forming 602 a cover of brazing material over the recess also includes filling the recess from the surface to the inner edge with the brazing paste such that the cover and the brazing paste within the recess are in fluid communication. In additional embodiments, heating 606 the brazing material within an environment to form at least partially molten brazing material also includes filling the recess to the inner edge with at least partially molten brazing material from the cover via capillary action. In certain embodiments, cooling 608 the at least partially molten brazing material to form a brazed joint also includes passively allowing the environment to cool.

[0048] In some embodiments, cooling 608 the at least partially molten brazing material includes cooling a location on the base that is closer to the inner edge than to the cover. In a particular embodiment, cooling 608 the at least partially molten brazing material also includes solidifying the cover. In some such embodiments, the solid-state cover has a greater porosity than the solid-state brazed joint.

[0049] Figure 7 is a flowchart of another exemplary method 700 of brazing a recess defined within a base, such as recess 214 within base 210 ( Figures 2 to 5 as shown). The recess extends from a base surface, such as base surface 212, to an inner edge within the base, such as inner edge 224. Method 700 includes supplying 702 at least partially molten brazing material, such as brazing material 218, from a cover, such as cover 220, to the inner edge within the recess. Method 700 also includes extracting 704 heat from the base at a location on the base that is closer to the inner edge of the base than to the base surface.

[0050] In some embodiments, extracting heat 704 from the base includes conduction cooling at that location using a heat exchanger. In other embodiments, extracting heat 704 from the base includes convective cooling at that location using impingement cooling.

[0051] In some embodiments, method 700 further includes positioning at least a partially solid brazing material above a recess within an environment such as environment 206. In some such embodiments, supplying the at least partially molten brazing material from the lid supply 602 to the recess further includes heating the environment to a brazing temperature to form the at least partially molten brazing material.

[0052] In certain embodiments, method 700 further includes positioning a thermal insulation layer, such as thermal insulation layer 302, above an exposed brazing surface on the lid, such as exposed brazing surface 222, before supplying the at least partially molten brazing material and extracting heat from the base.

[0053] The above-described systems and methods for forming a brazed joint within a component facilitate forming a brazed joint within a component with fewer or no defects within the joint during the brazing process, thereby reducing the need to replace the brazed joint and extending the life of the component having the brazed joint. These systems and methods result in a high degree of metallurgical integrity, which imparts excellent and reliable mechanical capabilities to the brazed joint. These systems and methods may be particularly advantageous for components used in extremely hot and high mechanical stress environments, such as components that are subjected to high temperatures and rotational stresses in the hot gas section of a gas turbine.

[0054] In addition to this, exemplary technical effects of the systems and methods described herein include at least one of the following: (a) reducing defects within the brazed joint due to curing shrinkage; (b) reducing the amount of brazing material required to supply the recess when forming a brazed joint within a component; and (c) extending the life of the brazed joint.

[0055] Exemplary embodiments of systems and methods for brazing joints within a component have been described in detail above. The systems and methods are not limited to the specific embodiments described herein, but rather the components of the system and / or steps of the method can be used independently and separately from other components and / or steps described herein. For example, these systems and methods can also be used in conjunction with many types of components and are not limited to being practiced only with a gas turbine engine as described herein. Rather, the exemplary embodiments can be implemented and used in conjunction with many other joint brazing applications.

[0056] Although specific features of various embodiments of the present disclosure may be shown in some figures and not in others, this is for convenience only. Any feature of a figure can be referenced and / or claimed in combination with any feature of any other figure in accordance with the principles of the embodiments of the present disclosure.

[0057] This written description uses examples to disclose embodiments of the present disclosure, including the best mode, and also enables any person skilled in the art to practice the embodiments of the present disclosure, including making and using any device or system and performing any combined method. The patentable scope of the embodiments described herein is defined by the claims, and may include other examples that occur to those skilled in the art. If such other examples have structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements that are not materially different from the literal language of the claims, then such other examples are intended to be within the scope of the claims.

Claims

1. A system (200, 300, 400, 500) for forming a brazed joint (202), the system (200, 300, 400, 500) comprising: An environment (206) that can be operated to reach a soldering temperature sufficient to melt at least a portion of a soldering material (218); A component (204) within the environment (206), the component (204) comprising: A base (210) including a base surface (212); A recess (214) that droops from the base surface (212) to an inner edge (224) in the base (210); and The soldering material (218) that forms a cover (220) within the recess (214) and above the base surface (212), the soldering material (218) filling the recess (214) from the cover (220) to the inner edge (224), The cover (220) having an exposed soldering surface (222); An insulating layer (302) that at least partially covers the exposed soldering surface (222), wherein the insulating layer (302) causes solidification defects to mainly form near the exposed soldering surface in the cover (220); and A cooling device (401) that can be operated to extract heat from a location (403) on the base (210), the location (403) being closer to the inner edge (224) of the recess (214) than to the cover (220), wherein the location is a second base surface of the base that is oppositely positioned to the base surface.

2. The system (200, 300, 400, 500) according to claim 1, wherein the brazing material (218) comprises a brazing filler alloy.

3. The system (200, 300, 400, 500) according to claim 2, wherein the brazing material (218) comprises a brazing paste containing the brazing alloy and brazing powder, the brazing powder having a melting point higher than that of the brazing filler alloy.

4. The system (200, 300, 400, 500) according to claim 1, wherein the insulating layer (302) comprises at least one of ceramic, ceramic fiber, mineral wool, polycrystalline fiber, and silica cloth, and wherein the insulating layer (302) completely covers the lid (220) and at least partially covers the base surface (212).

5. The system (200, 300, 400, 500) according to claim 1, wherein the ratio of the modulus of the lid (220) to the modulus of the brazed joint (202) is greater than or equal to 1.1, where the modulus is defined as the volume of the geometric body divided by the heat dissipation area of the geometric body.

6. A method (600) of brazing a recess (214) defined within a base (210), the recess (214) drooping from a base surface (212) of the base (210) to an inner edge (224) within the base (210), the method comprising: Forming (602) a cover (220) of soldering material (218) above the recess (214), the cover (220) having an exposed soldering surface (222); Positioning (604) a thermal insulating layer (302) above the exposed soldering surface (222), wherein the thermal insulating layer (302) causes solidification defects to mainly form near the exposed soldering surface in the cover (220); Heating (606) the soldering material (218) within the environment (206) to form at least partially molten soldering material (218); and Cooling (608) the at least partially molten soldering material (218) to form a solid-state solder joint (202) within the recess (214); Wherein cooling (608) the at least partially molten soldering material (218) includes cooling a location (403) on the base (210) that is closer to the inner edge (224) than to the cover (220), wherein the location is a second base surface of the base that is oppositely positioned to the base surface.

7. The method according to claim 6, wherein the brazing material (218) is a brazing paste comprising a brazing filler alloy, brazing powder, and a binder, and wherein forming (602) a cover (220) of the brazing material (218) over the recess (214) further comprises filling the recess (214) from the surface to the inner edge (224) with the brazing paste such that the cover (220) and the brazing paste in the recess (214) are in fluid communication.

8. The method according to claim 6, wherein heating (606) the brazing material (218) within the environment (206) to form at least partially molten brazing material (218) further comprises filling the recess (214) to the inner edge (224) with at least partially molten brazing material (218) from the cover (220) via capillary action.

9. The method according to claim 6, wherein cooling (608) the at least partially molten brazing material (218) further comprises solidifying the cover (220), wherein the solid cover (220) has a greater porosity than the solid brazed joint (202).

10. A method (700) of brazing a recess (214) defined within a base (210), the recess (214) depending from a base surface (212) of the base (210) to an inner edge (224) within the base (210), the method comprising: Supplying (702) at least partially molten soldering material (218) from the cover (220) to the inner edge (224) in the recess (214), wherein the cover (220) has an exposed soldering surface (222); Positioning (604) a thermal insulating layer (302) above the exposed soldering surface (222), wherein the thermal insulating layer (302) causes solidification defects to mainly form near the exposed soldering surface in the cover; Extract heat (704) from a location (403) on the base (210), the location (403) being closer to the inner edge (224) of the recess (214) than to the lid (220), wherein the location is a second base surface of the base that is positioned opposite the base surface.

11. The method according to claim 10, wherein extracting heat (704) further comprises conducting cooling at the location (403) using a heat exchanger (402).

12. The method according to claim 10, wherein extracting heat (704) further comprises impingement cooling at the location (403).

13. The method according to claim 10, further comprising positioning at least partially solid brazing material (218) over the recess (214) within the environment (206), wherein supplying the at least partially molten brazing material (218) from the cover (220) to the recess (214) further comprises heating the environment (206) to a brazing temperature to form the at least partially molten brazing material (218).

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