Active brazed joint and processing method

Abstract

A method of treating a joint, comprising forming an active braze joint in a vacuum furnace, the active braze joint being formed from at least two components joined together by a volume of a joining metal alloy having a solidus temperature and a liquidus temperature, the joining metal alloy being heated in the vacuum furnace to a first temperature above the liquidus temperature, the method further comprising cooling the active braze joint to a second temperature below the solidus temperature and maintaining the second temperature in the vacuum furnace for a predetermined duration to form at least one region of segregation crystallization within the volume of the joining metal alloy, the at least one region of segregation crystallization being configured to elevate the liquidus temperature of a layer of braze metal formed from the joining metal alloy between the at least two components.

Description

Technical Field

[0001] The present disclosure relates generally to active brazing, and more specifically to a method of treating an active brazed joint to increase its usable temperature.

Background Art

[0002] Active brazing is a method that can be used to join ceramic and metal components or to join ceramic components to each other. The alloys used to form active brazed joints are unique from other known brazing alloys in at least some respects. Specifically, for example, active brazing alloys based on silver, gold, or copper typically contain a specific content of "active" elements (such as titanium) that allow these elements to react with the ceramic surface under high vacuum to form a reaction layer and the reaction layer spreads between the ceramic component and the molten brazing alloy and acts as a connection between the ceramic component and the brazing alloy. However, active brazing alloys generally feature a relatively low melting point temperature. Therefore, due to the low melting point, the use of active brazed joints in high-temperature environments such as the high-temperature gas path in gas turbine applications may be inconveniently limited.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] In one embodiment, a method for processing a joint is provided. The method comprises forming an activated brazed joint in a vacuum furnace, the activated brazed joint being formed of at least two components bonded together by a certain volume of a joining metal alloy having a solidus temperature and a liquidus temperature, the joining metal alloy being heated in the vacuum furnace to a first temperature higher than the liquidus temperature. The method further comprises cooling the activated brazed joint to a second temperature lower than the solidus temperature, and maintaining the second temperature in the vacuum furnace for a predetermined duration to form at least one region of segregation crystallization within the volume of the joining metal alloy, the at least one region of segregation crystallization being configured to increase the liquidus temperature of the brazed metal layer formed from the joining metal alloy between the at least two components.

[0005] In another embodiment, a method for processing a brazed joint is provided. This method comprises heating an active brazed joint to a certain temperature, the active brazed joint being formed of at least two components bonded together by a certain volume of joining metal alloy having a solidus temperature and a liquidus temperature, and the active brazed joint being heated to a temperature lower than the solidus temperature. This method further comprises defining heating and cooling cycles by cooling the active brazed joint from the temperature, and performing a plurality of heating and cooling cycles over the active brazed joint to form at least one region of segregation crystallization within the volume of the joining metal alloy, the at least one region of segregation crystallization being configured to raise the liquidus temperature of the layer of brazed metal formed from the joining metal alloy between the at least two components.

[0006] In yet another embodiment, an activated brazed joint is provided. The activated brazed joint comprises a first component, a second component, and a layer of brazing metal bonded between the first and second components. The brazing metal comprises several elements, each having a weight percentage that determines the overall composition of the brazing metal. The layer of brazing metal comprises at least one region of segregated crystallization, wherein the weight percentage of at least one of the elements is greater than the overall composition in at least one region. [Brief explanation of the drawing]

[0007] [Figure 1] This is a side view of an exemplary activated brazed joint. [Figure 2] This is an enlarged cross-sectional view of a portion of the activated brazed joint enclosed by region 2 in Figure 1. [Figure 3] This is an enlarged cross-sectional view of a portion of the activated brazed joint enclosed by region 3 in Figure 2. [Figure 4] This is a flowchart illustrating an example method for processing joints. [Modes for carrying out the invention]

[0008] Embodiments described herein relate to methods for treating activated brazed joints to increase their usable temperature. The methods described herein include forming an activated brazed joint in a vacuum furnace by heating a joining metal alloy located between two components to a first temperature higher than the liquidus temperature of the alloy. After a predetermined residence time (typically about 10 to 30 minutes), the brazed joint is cooled to a second temperature lower than the solidus temperature of the alloy but still higher than room temperature. The temperature in the vacuum furnace is maintained at the second temperature for a predetermined duration. While not bound by any particular theory, it is believed that maintaining the vacuum furnace at a higher second temperature for a predetermined duration promotes the initiation of a diffusion phenomenon within the volume of the alloy. This diffusion phenomenon promotes the formation of regions of segregated crystallization within the volume of the alloy. These regions of segregated crystallization involve an increase in the concentration of individual elements contained in the alloy. For example, it has been shown that after this treatment, the brazed metal layer formed from the joining metal alloy between two components has a higher liquidus temperature compared to the joining metal alloy in its pre-treated state. Therefore, the resulting activated brazed joint can be used in environments with higher maximum operating temperatures.

[0009] Unless otherwise specified, the approximation terms used herein, such as “generally,” “substantially,” and “about,” indicate that the terms thus modified may apply only to an approximate degree as recognized by those skilled in the art, and not to an absolute or complete degree. Therefore, values ​​modified with terms such as “about,” “approximately,” and “substantially” are not limited to the exact values ​​specified. In at least some cases, the approximation terms may correspond to the precision of the instrument used to measure the value. Furthermore, unless otherwise indicated, terms such as “first,” “second,” etc., are used herein solely as labels and do not impose any order, position, or hierarchical requirements on the items referred to by these terms. Moreover, for example, a reference to a “second” item does not require or exclude the existence of, for example, a “first” item or a lesser-numbered item, or a “third” item or a more-numbered item. Where used herein, the term “upstream” refers to the front or inlet end of a rotating machine, and the term “downstream” refers to the downstream or exhaust end of a rotating machine.

[0010] Figure 1 is a side view of an exemplary activated brazed joint 100. In an exemplary embodiment, the activated brazed joint 100 includes a first component 102, a second component 104, and a volume 106 of the joined metal alloy. The first component 102 and the second component 104 can be manufactured from any material that enables the activated brazed joint 100 to function as described herein. In one embodiment, the first component 102 is manufactured from either a ceramic or metallic material, and the second component 104 is manufactured from a ceramic material. For example, the metallic material may be, but is not limited to, a nickel-based superalloy material. Thus, in one embodiment, the first component 102 is a high-temperature gas path component, such as a rotating or stationary component of a gas turbine engine, and the second component 104 is a sensor used to monitor process conditions within the gas turbine engine.

[0011] Prior to processing according to the method described herein, the joining metal alloy is placed between the first component 102 and the second component 104. In the pre-treated state, the volume 106 of the joining metal alloy may have a thickness T defined in the range of about 50 microns to about 200 microns and may be in the form of a brazed foil. The joining metal alloy is positioned to join the first component 102 to the second component 104. The joining metal alloy may contain any combination of elements that enable the activated brazed joint 100 to function as described herein. For example, in one embodiment, the joining metal alloy includes, but is not limited to, silver, copper, indium, and at least one active element. Exemplary active elements include, but are not limited to, titanium, hafnium, zirconium, and / or niobium. Therefore, in exemplary embodiments, the joined metal alloy comprises silver in an amount ranging from about 55% to about 65% by weight, copper in an amount ranging from about 20% to about 30% by weight, indium in an amount ranging from about 5% to about 30% by weight, and less than about 10% by weight of titanium.

[0012] Figure 2 is an enlarged cross-sectional view of a portion of the activated brazed joint 100 shown in Figure 1, and Figure 3 is an enlarged cross-sectional view of a portion of the activated brazed joint 100 shown in Figure 2. In an exemplary embodiment, the volume 106 of the joined metal alloy contains several elements, each having a weight percentage that determines the overall composition of the joined metal alloy. By treating the activated brazed joint 100 according to a method described in more detail below, the brazed metal layer 107 formed from the volume 106 of the joined metal alloy contains at least one region 108 of segregated crystallization. The weight percentage of at least one of the elements of the joined metal alloy is greater in at least one region 108 than its weight percentage in the overall composition. Although not bound by any particular theory, the heat treatment method described herein is thought to promote the segregation of phases (elements) in the volume 106, and at least one of the individual phases, or each individual phase, is thought to have a higher melting point than the joined metal alloy as a whole. Thus, by performing the heat treatment described herein on the activated brazed joint 100, it becomes easier to increase the operating temperature of the brazed metal.

[0013] Referring to Figure 3, at least one region 108 includes, for example, a first region 110, a second region 112, and a third region 114, each having different segregation crystallization. In an exemplary embodiment, in the first region 110, the weight percentage of the first element (e.g., silver) is greater than the weight percentage of the first element in the second region 112, the third region 114, and the overall composition of the joined metal alloy. Similarly, in the second region 112, the weight percentage of the second element (e.g., copper) is greater than the weight percentage of the second element in the first region 110, the third region 114, and the overall composition of the joined metal alloy, and in the third region 114, the weight percentage of the third element (e.g., titanium) is greater than the weight percentage of the third element in the first region 110, the second region 112, and the overall composition of the joined metal alloy. In some embodiments, the first, second, and third elements are dominant elements in each of the respective regions 110, 112, and 114, such that each element has a larger weight percentage than any other element contained in each of the respective regions 110, 112, and 114. The dominant elements in each of the respective regions 110, 112, and 114 may constitute less than about 50% by weight, more than about 25% by weight, more than about 50% by weight, or more than about 75% by weight of the composition of each of the respective regions 110, 112, and 114.

[0014] Figure 4 is a flowchart illustrating an exemplary method 200 for processing a joint. In an exemplary embodiment, method 200 includes a step 202 of forming a brazed joint, such as an activated brazed joint 100 (shown in Figure 1), in a vacuum furnace. As described above, the joining metal alloy of the brazed joint has a solidus temperature and a liquidus temperature. In forming step 202, the joining metal alloy is heated in the furnace to a first temperature higher than the liquidus temperature to facilitate the joining of the first component 102 and the second component 104 (both shown in Figure 1) to each other. After joining the first component 102 and the second component 104, a heat treatment process may be performed.

[0015] For example, Method 200 further includes the steps of cooling the brazed joint to a second temperature lower than the solidus temperature of the joined metal alloy, and maintaining the second temperature in a vacuum furnace for a predetermined duration. Maintaining the second temperature of the joined metal alloy in a vacuum furnace in step 206 is considered to facilitate the initiation of phase segregation within the joined metal alloy. The second temperature may be higher than about 90%, about 95%, or about 98% of the solidus temperature of the joined metal alloy in its pre-treated state. The second temperature is maintained for a predetermined duration between about 20 and 120 minutes (step 206). The vacuum furnace and the brazed joint are then cooled and heated again to determine heating and cooling cycles. In one embodiment, Method 200 further includes the step of performing a plurality of heating and cooling cycles for the brazed joint.

[0016] In exemplary embodiments, each heating and cooling cycle includes heating the brazed joint to a third temperature below the solidus temperature and cooling the brazed joint from the third temperature. The third temperature may be equal to, higher than, or lower than the second temperature. The heating step in the cycle includes heating the brazed joint in a vacuum furnace set to a temperature such as the third temperature below the solidus temperature for a duration specified in the range of about 20 to about 30 minutes. The cooling step in the cycle includes cooling the brazed joint to ambient temperature for a duration of less than about 10 minutes or less than about 5 minutes after the heating duration has elapsed. For example, the cooling of the brazed joint can be accelerated by directing a flow of compressed air towards the brazed joint. The heating step of the next heating and cooling cycle can then be started within 1 minute after the brazed joint has cooled to ambient temperature by setting the vacuum furnace to a certain temperature. In this way, the thermal cycle is thought to accelerate and strengthen the segregation of layers within the joined metal alloy. In another embodiment, the cooling step in the cycle includes cooling the brazed joint to ambient temperature over a period of about 2.5 hours after the heating period has elapsed.

[0017] As used herein, “ambient temperature” refers to a temperature range with a lower limit of approximately 15 degrees Celsius and an upper limit of approximately 30 degrees Celsius.

[0018] Any number of heating and cooling cycles can be performed on the brazed joint to enable Method 200 to function as described herein (step 208). For example, the heat treatment process of the brazed joint may include performing a predetermined number of heating and cooling cycles, such as at least two heating and cooling cycles, at least three heating and cooling cycles, or at least seven heating and cooling cycles.

[0019] After a predetermined number of heating and cooling cycles, the brazed joint can be subjected to non-destructive testing and / or incorporated into an assembly, such as within the high-temperature gas path of a gas turbine engine. Non-destructive testing is used to verify the extent, and therefore the strength, of the joint between the first component 102 and the second component 104. Exemplary non-destructive testing techniques include, but are not limited to, ultrasonic testing. In some embodiments, the temperature within the high-temperature gas path of a gas turbine engine can reach a predetermined temperature, such as about 600 degrees Celsius. In exemplary embodiments, the brazed joint treated according to Method 200 is configured to operate in an environment having a temperature higher than the predetermined temperature. For example, the brazed joint treated according to Method 200 has a liquidus temperature higher than the predetermined temperature.

[0020] Embodiments described herein relate to activated brazed joints and methods for treating the same. Methods described herein facilitate increasing the liquidus temperature of the joined metal alloy used in activated brazed joints. For example, a treatment step facilitates the formation of segregated crystallization regions having a certain volume of the joined metal alloy, each region being formed from an increase in the concentration of individual elements of the alloy. Individual elements may have a higher liquidus temperature than the alloy as a whole. Thus, it becomes easier to increase the operating temperature of the activated brazed joint.

[0021] The above description is intended only as an example, and those skilled in the art will recognize that modifications can be made to the described embodiments without departing from the scope of the disclosed invention. For example, the process steps described herein may be modified, for example, in terms of duration, temperature, or time between cycles. Other modifications within the scope of the present invention will be apparent to those skilled in the art upon consideration of this disclosure, and such modifications are intended to be within the scope of the appended claims.

[0022] Exemplary embodiments of an active brazed joint and a method of treating the same have been described in detail above. The method is not limited to the specific embodiments described herein. Rather, the steps of the method can be utilized separately and independently of the other steps described herein. For example, the method described herein is not limited to implementation only in joints used in the hot gas path of the gas turbine engine described herein. Rather, the exemplary embodiments can be implemented and utilized in relation to many other applications.

[0023] Certain features of various embodiments of the present invention may be shown in some drawings and not in others, but this is merely for convenience. Further, references to "one embodiment" in the above description are not intended to be construed as excluding the existence of additional embodiments that also incorporate the described features. According to the principles of the present invention, any feature in any drawing can be referenced and / or claimed in combination with any feature in any other drawing.

[0024] Although the present invention has been described with respect to various specific embodiments, those skilled in the art will recognize that the present invention can be practiced with modifications within the spirit and scope of the claims.

Description of Reference Numerals

[0025] 100 Brazed joint 102 First component 104 Second component 106 Volume of joined metal alloys 107 Layers of brazed metal 108 At least one region of segregation crystallization 110 First Domain 112 Second Domain 114 The Third Domain 200 ways

Claims

1. A method for treating a joint (100), comprising the steps of: forming an active braze joint (100) in a vacuum furnace, the active braze joint (100) being formed from at least two components (102, 104) joined together by a volume (106) of a joining metal alloy having a solidus temperature and a liquidus temperature, the joining metal alloy being heated in the vacuum furnace to a first temperature greater than the liquidus temperature; cooling the active braze joint (100) to a second temperature below the solidus temperature; maintaining the second temperature in the vacuum furnace for a predetermined duration to form at least one region of segregation crystallization (108) within the volume (106) of the joining metal alloy, the at least one region of segregation crystallization (108) configured to increase the liquidus temperature of a layer (107) of braze metal formed from the joining metal alloy between the at least two components (102, 104); A method comprising:

2. Further comprising the step of performing a plurality of heating and cooling cycles on the active braze joint (100), each heating and cooling cycle comprising: heating the active braze joint (100) to a third temperature below the solidus temperature; cooling the active braze joint (100) from the third temperature; The method of claim 1 , comprising:

3. Each heating and cooling cycle is performed heating the active braze joint (100) in the vacuum furnace set at a temperature below the solidus temperature for a duration determined within a range of between about 20 minutes and about 120 minutes; cooling the active braze joint (100) to ambient temperature within a duration of less than about 10 minutes; The method of claim 2 , comprising:

4. 2. The method of claim 1, wherein the step of forming an active braze joint (100) comprises forming the active braze joint (100) from a joining metal alloy including silver, copper, indium, and at least one active element.

5. 5. The method of claim 4, wherein forming the active braze joint (100) comprises forming the active braze joint (100) from a joining metal alloy including the at least one active element comprising titanium, hafnium, zirconium, or niobium.

6. 5. The method of claim 4, wherein the step of forming the active braze joint (100) comprises forming the active braze joint (100) from a joining metal alloy including silver defined within a range between about 55% and about 65% by weight, copper defined within a range between about 20% and about 30% by weight, indium defined within a range between about 5% and about 30% by weight, and less than about 10% by weight of the at least one active element.

7. A method for treating a brazed joint (100), comprising: heating an active braze joint (100) to a temperature, the active braze joint (100) being formed from at least two components (102, 104) bonded together by a volume (106) of a joining metal alloy having a solidus temperature and a liquidus temperature, the active braze joint (100) being heated to a temperature that is less than the solidus temperature; cooling the active braze joint (100) from said temperature to define a heating and cooling cycle; performing a plurality of heating and cooling cycles on the active braze joint (100) to form at least one region of segregation crystallization (108) within a volume (106) of the joining metal alloy, the at least one region of segregation crystallization (108) configured to increase the liquidus temperature of a layer (107) of braze metal formed from the joining metal alloy between the at least two components (102, 104); A method comprising:

8. The method of claim 7, further comprising forming the active braze joint (100) from a joining metal alloy comprising silver, copper, indium, and at least one active element.

9. 9. The method of claim 8, wherein forming the active braze joint (100) comprises forming the active braze joint (100) from a joining metal alloy including the at least one active element comprising titanium, hafnium, zirconium, or niobium.

10. 9. The method of claim 8, wherein the step of forming the active braze joint (100) comprises forming the active braze joint (100) from a joining metal alloy including silver defined within a range between about 55% and about 65% by weight, copper defined within a range between about 20% and about 30% by weight, indium defined within a range between about 5% and about 30% by weight, and less than about 10% by weight titanium.

11. 8. The method of claim 7, wherein the step of heating the active braze joint comprises heating the active braze joint in a vacuum furnace set at a temperature below the solidus temperature, and the active braze joint is heated for a duration within a range between about 20 minutes and about 120 minutes.

12. 8. The method of claim 7, wherein cooling the active braze joint (100) comprises cooling the active braze joint (100) to ambient temperature within a duration of less than about 5 minutes.

13. 13. The method of claim 12, wherein performing several heating and cooling cycles includes reheating the active braze joint (100) within one minute after the active braze joint (100) has cooled to the ambient temperature.

14. The method of claim 7, wherein cooling the active braze joint (100) comprises cooling the active braze joint (100) to ambient temperature for a duration of about 2.5 hours.

15. An active braze joint (100), comprising: a first component (102); a second component (104); and a layer of braze metal (107) bonded between said first component (102) and said second component (104); wherein the braze metal includes a plurality of elements each having a weight percentage that defines an overall composition of the braze metal, and wherein the layer of braze metal includes at least one region of segregated crystallization, and wherein the weight percentage of at least one of the elements is greater than the overall composition in the at least one region.

16. 16. The active braze joint (100) of claim 15, wherein the first component (102) is fabricated from one of a ceramic material or a metallic material including a nickel-based superalloy material, and the second component (104) is fabricated from a ceramic material.

17. 16. The active braze joint (100) of claim 15, wherein the braze metal comprises silver, copper, indium, and at least one active element.

18. The active braze joint (100) of claim 17, wherein the at least one active element comprises titanium, hafnium, zirconium, or niobium.

19. The active braze joint (100) of claim 15, wherein the weight percentage of at least one of silver or copper is greater than the overall composition in the at least one region (108).

20. 16. The active braze joint (100) of claim 15, wherein the at least one region of segregated crystallization (108) comprises a first region of segregated crystallization (110) and a second region of segregated crystallization (112), the first region (110) being different from the second region (112).

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