Solder for welding nickel-based single crystal superalloys, its application, solder product and welding method

Abstract

This application relates to the field of welding technology, and discloses a solder for welding nickel-based single crystal superalloys, its application, a solder product and a welding method. The solder described in this application includes Al: 2.5% - 3.5%, Cr: 8.0% - 14.0%, Co: 6.0% - 8.0%, Hf: 0 - 0.2%, Re: 0.5% - 1.5%, Ta: 6.0% - 7.0%, W: 3.0% - 4.0%, C: 0 - 0.07%, B: 1.0% - 2.0%, Si: 0.5% - 1.5%, and the balance is Ni. The solder described in this application has high wetting performance and solid-liquidus temperature, is suitable for welding high-strength joints serving in high-temperature environments, ensures that the weld center of the nickel-based single crystal superalloy does not undergo primary melting or melting during service in high-temperature environments, and the composition and microstructure at the weld after TLP welding are close to those of the base material, improving the high-temperature strength after welding.

Description

Technical Field

[0001] The present application relates to the field of welding technology, and particularly to a solder for welding nickel-based single crystal superalloys, its application, a solder product, and a welding method. Background Art

[0002] Nickel-based single crystal superalloys have excellent high-temperature strength, creep resistance, and fatigue resistance in high-temperature environments, and are key materials for manufacturing hot-end components of aeroengines. However, during actual service, aeroengines are usually affected by factors such as vibration, wear, thermal fatigue, and hot corrosion, and are prone to forming defects such as cracks, wear, and corrosion pits, which seriously endanger the safety of aeroengines and reduce their service life. At the same time, hot-end components such as turbine blades are complex in design and expensive in cost. If they are directly scrapped, it will cause great waste of resources and increase the maintenance cost of aeroengines. If welding technology is used to repair the defects of defective components and increase their service life, the cost can be reduced and resources can be saved.

[0003] Transient Liquid Phase Bonding (TLP) is a new welding technology invented by D.S. Duvall, W.A. Owczarski, D.F. Paulonis, etc. in the 1970s. This technology mainly includes two stages: the isothermal solidification stage and the composition homogenization stage. In the isothermal solidification stage, a low-melting-point solder is placed between the materials to be welded, heated to the bonding temperature in a vacuum or inert gas environment, and then kept warm for a long time. During this process, the low-melting-point solder melts to form a liquid film. As the holding time prolongs, the melting-point-lowering elements in the solder continuously diffuse into the base metal matrix, resulting in an increase in the melting point, and the liquid phase gradually shrinks and solidifies from both sides to the middle. The composition homogenization stage refers to the process in which after the liquid phase solidifies, the welded joint is kept warm for a long time, and each element continuously diffuses, and the joint composition gradually becomes uniform. After the heat preservation ends, the microstructure and structure of the weld zone are basically the same as those of the base metal.

[0004] In order to obtain high-strength welded joints, a welding process with high temperature and long-time heat preservation is usually required. However, existing commercial solders for TLP, such as BNi-1, BNi-2, etc., have simple compositions and low solid-liquidus temperatures. During welding repair at the working temperature of nickel-based single crystal superalloy blades, primary melting or even melting is likely to occur, and it is difficult to form high-strength joints after welding. Summary of the Invention

[0005] In view of this, the purpose of the present application is to provide a solder for welding nickel-based single crystal superalloys, which has high wetting performance and solid-liquidus temperature, is suitable for welding high-strength joints serving in high-temperature environments, ensures that the center of the weld does not undergo primary melting or melting when the nickel-based single crystal superalloy serves in a high-temperature environment, and the composition and microstructure at the weld are close to those of the base metal after TLP welding, thereby improving the high-temperature strength after welding;

[0006] Another purpose of the present application is to provide the application of the solder in the preparation of solder products for welding nickel-based single crystal superalloys and in welding nickel-based single crystal superalloy joints;

[0007] Another purpose of the present application is to provide a product and a welding method based on the solder, which are suitable for welding nickel-based single crystal superalloys, especially TLP welding.

[0008] To solve the above technical problems / achieve the above purposes or at least partially solve the above technical problems / achieve the above purposes, as the first aspect of the present application, a solder for welding nickel-based single crystal superalloys is provided. By mass percentage, it includes:

[0009] Al: 2.5% - 3.5%, Cr: 8.0% - 14.0%, Co: 6.0% - 8.0%, Hf: 0 - 0.2%, Re: 0.5% - 1.5%, Ta: 6.0% - 7.0%, W: 3.0% - 4.0%, C: 0 - 0.07%, B: 1.0% - 2.0%, Si: 0.5% - 1.5%, and the balance is Ni.

[0010] Optionally, by mass percentage, the solder includes:

[0011] Al: 2.8% - 3.5%, Cr: 12.0% - 14.0%, Co: 7.0% - 7.5%, Re: 0.8% - 1.2%, Hf: 0.10% - 0.15%, Ta: 6.5% - 6.8%, W: 3.5% - 3.8%, C: 0.05% - 0.07%, B: 1.5% - 2.0%, Si: 0.5% - 1.0%, and the balance is Ni.

[0012] Further optionally, by mass percentage, the solder includes:

[0013] Al: 2.86% - 3.46%, Cr: 12.06% - 13.5%, Co: 7.40% - 7.43%, Re: 0.83% - 1.01%, Hf: 0.13% - 0.15%, Ta: 6.50% - 6.56%, W: 3.50% - 3.58%, C: 0.062% - 0.069%, B: 1.67% - 1.99%, Si: 0.57% - 0.80%, and the balance is Ni.

[0014] Optionally, the solder has a particle size range of 20 μm to 80 μm, an oxygen content of less than 150 ppm, and a nitrogen content of less than 20 ppm.

[0015] As a second aspect of the present application, based on the excellent properties of the solder of the present application in terms of wettability, solid-liquid phase transition temperature, high-temperature strength after welding, etc., there is provided an application of the solder in preparing a solder product for welding nickel-based single-crystal superalloys or in welding nickel-based single-crystal superalloy joints.

[0016] As a third aspect of the present application, there is provided a solder product for welding nickel-based single-crystal superalloys, comprising the solder and a binder described in the present application.

[0017] As a fourth aspect of the present application, there is provided a welding method for nickel-based single-crystal superalloy joints, using the solder described in the present application as a filler metal and performing welding through the TLP process.

[0018] Optionally, the welding method includes:

[0019] Removing impurities from the surface of the joint to be welded of the nickel-based single-crystal superalloy;

[0020] Formulating the solder and the binder described in the present application into a paste mixture, uniformly coating the paste mixture on the surface to be welded of the joint, fixing and drying;

[0021] Then, brazing the nickel-based single-crystal superalloy joint through the TLP process.

[0022] Optionally, the TLP process includes:

[0023] Heating to 500 - 600 °C, then holding for 20 - 40 min; then heating to 1000 - 1050 °C, holding for 10 - 30 min; heating to the welding temperature of 1250 °C - 1290 °C, holding for 8 - 16 h; after the holding is completed, cooling in vacuum to prevent oxidation, and the vacuum degree during the welding process is not less than 5×10 -2 Pa.

[0024] Further optionally, the heating rate is 5 - 10 °C / min from room temperature to 500 - 600 °C, and 15 - 25 °C / min from 500 - 600 °C to the welding temperature.

[0025] Compared with the prior art, the beneficial effects of the present application at least include:

[0026] ①The solder in this application reduces the contents of both B and Si elements, greatly reducing the precipitation amount of brittle borides and silicides. Meanwhile, an appropriate amount of Re element that is not contained in traditional commercial TLP solder is added. The dual effects of reducing B and Si and adding Re element can significantly improve the high-temperature mechanical properties of the welded joint;

[0027] ②The solidus temperature (≥1102°C) of the solder in this application is much higher than that of general commercial TLP solder, which can effectively prevent the primary melting or melting phenomenon from occurring in the weld of nickel-based single-crystal superalloy blades during high-temperature service after welding or repair. The liquidus temperature (≤1220°C) is lower than the solution temperature of the single-crystal blade, enabling TLP welding to have a wide enough process temperature window;

[0028] ③The solder in this application has high wettability, with uniform solder powder particle size, high sphericity, and low oxygen and nitrogen contents. Description of the Drawings

[0029] Figure 1 The figure shows the morphology of the solder powder in this application;

[0030] Figure 2 The figure shows the DSC test results of the solder in Example 1;

[0031] Figure 3 The figure shows the microstructure of the TLP welded joint in Example 1;

[0032] Figure 4 The figure shows the DSC test results of the solder in Example 2;

[0033] Figure 5 The figure shows the microstructure of the TLP welded joint in Example 2;

[0034] Figure 6 The figure shows the DSC test results of the solder in Comparative Example 1;

[0035] Figure 7 The figure shows the microstructure of the TLP welded joint in Comparative Example 1;

[0036] Figure 8 The figure shows the DSC test results of the solder in Comparative Example 2;

[0037] Figure 9 The figure shows the microstructure of the TLP welded joint in Comparative Example 2;

[0038] Figure 10 The figure shows the comparison of the high-temperature tensile strengths of the examples, comparative examples, and DD5 single-crystal base material. Detailed Embodiments

[0039] The present application discloses a solder for welding nickel-based single crystal superalloys, its applications, solder products and welding methods. Those skilled in the art can draw on the content of this article and appropriately modify the process parameters to achieve the same. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are all considered to be included in the present application. The methods described in the present application have been described through preferred embodiments. Relevant personnel can obviously make changes or appropriate alterations and combinations to the methods described herein without departing from the content, spirit and scope of the present application to implement and apply the technology of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts belong to the scope protected by the present application.

[0040] It should be noted that in this article, relational terms such as "first" and "second", "step 1" and "step 2", and "(1)" and "(2)" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the said element. At the same time, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0041] In the solder, boron and silicon are necessary components for reducing the solid-liquid phase lines of the filler metal. They can ensure that the filler metal melts while the parts do not melt, and can also improve the applicable range of the filler metal. However, through research, the present application has found that the current commercial filler metals of this type will cause a decrease in the strength of nickel-based single crystal superalloys after TLP.

[0042] In order to enable the joint after TLP diffusion welding to obtain high-strength properties close to those of the base material, the TLP process needs to be held at a high temperature for a long time. This requires the solder to have a higher melting point and contain a certain amount of solid-solution strengthening elements and precipitation strengthening elements. The solder composition of this application is based on the base material to be welded (nickel-based single-crystal superalloy). By adding a small amount of B (≤2%) and Si (≤1.5%) element content, the melting point of the solder is reduced and the wetting performance is improved. While meeting the requirements of the solder process attributes for the TLP process, a large amount of brittle borides and silicides are not formed. At the same time, elements with faster diffusion rates during the TLP process (such as Al, Ti, etc.) are reduced to lower the liquidus line; a certain amount of solid-solution strengthening elements with slower diffusion rates during the TLP process (such as W, Ta, Hf, etc.) are retained; Re element, which is not present in general commercial TLP solders, is added. After adding Re, the coarsening rate of the γ' phase can be slowed down and the absolute value of the γ / γ' lattice misfit degree can be reduced, thereby enhancing the elastic strain field caused by γ', forming a higher coherent strain strengthening effect, and improving the high-temperature strength of the alloy; but at the same time, it also results in a high solid-liquidus line of the solder, close to the solution temperature, and the content of other elements needs to be reasonably adjusted to achieve balance and ensure that the joint after TLP has high strength and high temperature-bearing capacity.

[0043] Based on the above discoveries and design principles of this application, in the first aspect of this application, a solder for welding nickel-based single-crystal superalloys is provided. By mass percentage, it includes:

[0044] Al: 2.5% - 3.5%, Cr: 8.0% - 14.0%, Co: 6.0% - 8.0%, Hf: 0 - 0.2%, Re: 0.5% - 1.5%, Ta: 6.0% - 7.0%, W: 3.0% - 4.0%, C: 0 - 0.07%, B: 1.0% - 2.0%, Si: 0.5% - 1.5%, and the balance is Ni.

[0045] The solid-liquidus range of the content described in this application is between 1102°C and 1220°C. Its solidus temperature is much higher than that of general commercial TLP solders. After TLP welding (after composition homogenization), the melting point of the weld zone can be increased to 1250 - 1280°C, ensuring that the welded joint does not undergo primary melting during use and is suitable for welding high-temperature-bearing components (such as single-crystal turbine blades); there is a wide TLP welding temperature range between the liquidus temperature and the solution temperature of the part, ensuring that the microstructure of the part to be welded is not affected by the TLP welding process.

[0046] In some embodiments of this application, by mass percentage, the solder includes:

[0047] Al: 2.8% - 3.5%, Cr: 12.0% - 14.0%, Co: 7.0% - 7.5%, Re: 0.8% - 1.2%, Hf: 0.10% - 0.15%, Ta: 6.5% - 6.8%, W: 3.5% - 3.8%, C: 0.05% - 0.07%, B: 1.5% - 2.0%, Si: 0.5% - 1.0%, the balance being Ni.

[0048] In some other embodiments of the present application, by mass percentage, the solder comprises:

[0049] Al: 2.86% - 3.46%, Cr: 12.06% - 13.5%, Co: 7.40% - 7.43%, Re: 0.83% - 1.01%, Hf: 0.13% - 0.15%, Ta: 6.50% - 6.56%, W: 3.50% - 3.58%, C: 0.062% - 0.069%, B: 1.67% - 1.99%, Si: 0.57% - 0.80%, the balance being Ni.

[0050] In some other embodiments of the present application, by mass percentage, the solder can select any one of the following compositions:

[0051] (1) Al: 3.46%, Cr: 12.06%, Co: 7.43%, Re: 1.01%, Hf: 0.15%, Ta: 6.56%, W: 3.58%, C: 0.069%, B: 1.99%, Si: 0.57%, the rest being Ni;

[0052] (2) Al: 2.86%, Cr: 13.5%, Co: 7.40%, Re: 0.83%, Hf: 0.13%, Ta: 6.50%, W: 3.5%, C: 0.062%, B: 1.67%, Si: 0.80%, the rest being Ni.

[0053] The solder for welding nickel - based single - crystal superalloys in the present application can use raw materials with a purity greater than 99.99% to proportionally prepare the melting charge of the solder, then use a vacuum melting furnace to melt it into a master alloy ingot, and use the plasma rotating electrode atomization process to prepare the master alloy ingot into a powder state, and perform screening to obtain the desired solder. The particle size range of the solder is 20μm - 80μm, the oxygen content is less than 150ppm, the nitrogen content is less than 20ppm, and the morphology is shown in Figure 1 .

[0054] In the second aspect of the present application, performance tests were carried out by adjusting the composition and content composition of the elements to form a comparative ratio. The results showed that when the solder described in the present application was used for TLP welding of DD5 single crystal alloy, the microstructure of the welded joint of the specimen after TLP welding was observed by SEM. The degree of combination of γ' phase at the weld joint of the specimen was good, and no obvious boride or silicide precipitation phase was found at the weld. The high-temperature tensile strength of the welded joint reached more than 80% of the base material DD5 single crystal alloy. However, there were certain differences in the morphology of γ' phase at the weld joint of the specimen in the comparative ratio and the matrix of DD5 single crystal base material, and the high-temperature tensile strength of the welded joint was significantly lower than that of the solder of the present application. Based on this, the present application provides the application of the solder in the preparation of solder products for welding nickel-based single crystal superalloys or in welding nickel-based single crystal superalloy joints.

[0055] In the third aspect of the present application, a solder product for welding nickel-based single crystal superalloys is provided, which includes the solder described in the present application and a binder.

[0056] In some embodiments of the present application, the mass percentage of the binder is 10-20%, and a water-based or oil-based binder can be selected, such as Nicrobraz's'Binder, etc.

[0057] In the fourth aspect of the present application, a welding method for nickel-based single crystal superalloy joints is provided, using the solder described in the present application as a filler metal and performing welding through the TLP process.

[0058] In some embodiments of the present application, the welding method includes:

[0059] Removing impurities on the surface of the joint to be welded of the nickel-based single crystal superalloy;

[0060] Formulating the solder and the binder described in the present application into a paste mixture, uniformly coating it on the surface to be welded of the joint, fixing and drying;

[0061] Then performing brazing on the nickel-based single crystal superalloy joint through the TLP process.

[0062] Among them, the removal of impurities on the joint surface includes removing impurities such as oil stains and oxide films on the surface of the joint to be welded by chemical or mechanical polishing methods to avoid affecting the welding quality;

[0063] The TLP process includes:

[0064] Heating to 500-600°C, then holding for 20-40 min; then heating to 1000-1050°C, holding for 10-30 min; heating to the welding temperature of 1250°C - 1290°C, holding for 8-16 h; after the holding is completed, cooling in vacuum to prevent oxidation, and the vacuum degree during the welding process is not less than 5×10 -2Pa.

[0065] In some other embodiments of the present application, the TLP process includes:

[0066] Heat to 550℃, then keep warm for 30min; then heat to 1000℃, keep warm for 20min; heat to welding temperature 1250℃~1290℃, keep warm for 8~16h; after the end of the insulation, vacuum cooling is performed to prevent oxidation. The vacuum degree during welding should not be less than 5×10 -2 Pa, the welding process may require no pressure or a certain amount of pressure.

[0067] In certain embodiments of the present application, the heating rate is 5-10°C / min from room temperature to 500-600°C, and 15-25°C / min from 500-600°C to the welding temperature, for example 5°C / min, 10°C / min, 15°C / min, 20°C / min or 25°C / min.

[0068] In certain embodiments of the present application, the welding method comprises:

[0069] Step 1: Use chemical or mechanical grinding to remove impurities such as oil, oxide film, etc. on the surface of the joint to be welded;

[0070] Step 2: Use an oily or water-based binder to mix the prepared solder powder into a paste (where the binder accounts for 10% to 20%), and evenly apply the paste powder on the surface of the nickel-based single crystal high-temperature alloy sample to be welded, and use a customized ceramic mold to fix the sample and place it in a constant temperature drying oven for drying;

[0071] Step 3: Place the dried sample in a vacuum brazing furnace. The welding process is as follows: heat to 550°C at a heating rate of 10°C / min, and then keep warm for 30 minutes; then heat to 1000°C at a heating rate of 10°C / min, and keep warm for 20 minutes; heat to the welding temperature of 1250°C~1290°C at a heating rate of 15°C / min, and keep warm for 8~16 hours; after the insulation, the sample is vacuum cooled with the furnace to prevent oxidation. The vacuum degree during the welding process is not less than 5×10 -2 Pa, no pressure or a certain pressure is applied during welding.

[0072] In each group of comparative experiments provided in this application, unless otherwise specified, except for the differences indicated in each group, other experimental conditions, materials, etc. are kept consistent to ensure comparability.

[0073] The following is a further description of a nickel-based single crystal high-temperature alloy welding solder provided in this application, its application, solder products and welding methods.

[0074] Embodiment 1:

[0075] 1. Solder Preparation

[0076] The raw materials with a purity greater than 99.99% are used to proportionally prepare the solder for smelting, and then melted into a master alloy ingot using a vacuum melting furnace. The master alloy ingot is prepared into a powder state using the plasma rotating electrode atomization process and screened to obtain a solder with a powder particle size of 20μm - 80μm. The chemical composition is as follows:

[0077] Al: 3.46%, Cr: 12.06%, Co: 7.43%, Re: 1.01%, Hf: 0.15%, Ta: 6.56%, W: 3.58%, C: 0.069%, B: 1.99%, Si: 0.57%, and the rest is Ni.

[0078] 2. Performance Testing

[0079] The DSC test is carried out on the solder for TLP welding prepared in this example. The results are as Figure 2 shown. Its solidus temperature is 1103°C and its liquidus temperature is 1209°C.

[0080] The wettability test is carried out on the solder for TLP welding prepared in this example. The wetting angle on the surface of the nickel-based single crystal superalloy plate is only 11.4°, showing excellent wetting performance.

[0081] 3. Welding Testing

[0082] Taking DD5 single crystal alloy as the welding base material (working temperature 1100°C - 1150°C, melting point 1340°C), a TLP high-strength welded joint is carried out. The method includes:

[0083] Step 1: Use 200#, 400#, 600#, and 800# sandpapers to gradually grind off the oxide film on the surface of the joint to be welded, and use ultrasonic cleaning in acetone solvent to remove the oil stain on the surface of the joint to be welded.

[0084] Step 2: The prepared powder solder is mixed with an oily or aqueous binder in a ratio of 85:15 to form a paste. The paste powder is evenly coated on the surface of the specimen to be welded, and the specimen is fixed using a customized ceramic mold and placed in a constant temperature drying oven for drying. The drying temperature is 140 ± 5°C and the drying time is not less than 60 min.

[0085] Step 3: Put the dried specimen into a vacuum brazing furnace, and the welding process specifications are as follows: Heat it to 550°C at a heating rate of 10°C / min, then hold for 30 min; then heat it to 1000°C at a heating rate of 10°C / min and hold for 20 min; heat it to the welding temperature of 1280°C at a heating rate of 15°C / min and hold for 12 h; after the holding is completed, the specimen is cooled in vacuum with the furnace to prevent oxidation. The vacuum degree during the welding process is not less than 5×10 -2 Pa. Apply a pressure of 0.01 MPa to the specimen during the test.

[0086] Use SEM to observe the microstructure of the welded joint of the specimen after TLP welding. The results are as Figure 3 shown. It can be found that the γ'-phase combination degree at the weld joint of the specimen in Example 1 is better, and no obvious boride and silicide precipitation phases are found at the weld.

[0087] Example 2:

[0088] 1. Solder preparation

[0089] Prepared by referring to the method of Example 1, and the chemical composition is as follows:

[0090] Al: 2.86%, Cr: 13.5%, Co: 7.40%, Re: 0.83%, Hf: 0.13%, Ta: 6.50%, W: 3.5%, C: 0.062%, B: 1.67%, Si: 0.80%, and the rest is Ni.

[0091] 2. Performance test

[0092] Perform DSC test on the TLP welding solder prepared in this example. The results are as Figure 4 shown. Its solidus temperature is 1102°C and its liquidus temperature is 1219°C.

[0093] Perform wettability test on the TLP welding solder prepared in this example. The wetting angle on the surface of the nickel-based single crystal superalloy plate is only 13.7°, showing excellent wetting performance.

[0094] 3. Welding test

[0095] Test by referring to the method of Example 1. Use SEM to observe the microstructure of the welded joint of the specimen after TLP welding. The results are as Figure 5 shown. It can be found that the γ'-phase combination degree at the weld joint of the specimen in Example 2 is better, and no obvious boride and silicide precipitation phases are found at the weld.

[0096] Comparative Example 1:

[0097] 1. Solder preparation

[0098] Prepared according to the method of Example 1, the chemical composition is as follows:

[0099] Al: 2.92%, Cr: 10.5%, Co: 7.05%, Hf: 0.11%, Ta: 6.20%, W: 3.34%, C: 0.053%, B: 1.83%, Si: 0.73%, the balance being Ni.

[0100] 2. Performance testing

[0101] The DSC test was carried out on the solder for TLP welding prepared in this comparative example, as shown in Figure 6 , its solidus temperature is 1086 °C and its liquidus temperature is 1220 °C.

[0102] The wettability test was carried out on the solder for TLP welding prepared in this comparative example, and the wetting angle on the surface of the nickel-based single crystal superalloy plate is 14.3°.

[0103] 3. Welding test

[0104] Tested according to the method of Example 1, the microstructure of the welded joint of the specimen after TLP welding was observed by SEM, and the results are as shown in Figure 7 . It can be found that although no obvious boride and silicide precipitation phases are found at the weld joint of the specimen in Comparative Example 1, there are certain differences in the γ' phase morphology and the DD5 single crystal base metal matrix, which will affect the high-temperature strength during actual service.

[0105] Comparative Example 2:

[0106] 1. Solder preparation

[0107] Prepared according to the method of Example 1, the chemical composition is as follows:

[0108] Al: 3.20%, Cr: 12.5%, Co: 7.38%, Re: 1.05%, Hf: 0.12%, Ta: 6.37%, W: 3.51%, C: 0.062%, B: 2.87%, Si: 1.80%, the balance being Ni.

[0109] 2. Performance testing

[0110] The DSC test was carried out on the solder for TLP welding prepared in this comparative example, as shown in Figure 8 , its solidus temperature is 1073 °C and its liquidus temperature is 1176 °C.

[0111] The wettability test was carried out on the solder for TLP welding prepared in this comparative example, and the wetting angle on the surface of the nickel-based single crystal superalloy plate is 12.2°.

[0112] 3. Welding test

[0113] Tested according to the method of Example 1, the microstructure of the welded joint of the specimen after TLP welding was observed by SEM, and the results are as Figure 9 shown. It can be found that a large amount of boride and silicide precipitation phases are found at the weld of the specimen of Comparative Example 2.

[0114] Experimental Example:

[0115] The high-temperature tensile properties of the specimens of the examples, the specimens of the comparative examples and the single-crystal base material DD5 alloy were tested according to the standard of GB / T 228.2-2015, and the results are as Figure 10 shown. The high-temperature tensile strength of the welded joint reaches more than 80% of that of the base material DD5 single-crystal alloy, and the high-temperature tensile strength of the welded joints of Comparative Examples 1 and 2 is only about 70% of that of the base material DD5 single-crystal.

[0116] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A solder for welding nickel-based single crystal superalloys, characterized in that, by mass percentage, it includes: Al: 2.5% - 3.5%, Cr: 8.0% - 14.0%, Co: 6.0% - 8.0%, Hf: 0 - 0.2%, Re: 0.5% - 1.5%, Ta: 6.0% - 7.0%, W: 3.0% - 4.0%, C: 0 - 0.07%, B: 1.0% - 2.0%, Si: 0.5% - 1.5%, the balance is Ni; the particle size range of the solder is 20μm - 80μm, the oxygen content is less than 150ppm, and the nitrogen content is less than 20ppm; wherein, the solidus temperature of the solder for welding nickel-based single crystal superalloys ≥ 1102°C, and the liquidus temperature of the solder for welding nickel-based single crystal superalloys ≤ 1220°C; wherein, after the solder for welding nickel-based single crystal superalloys is subjected to TLP welding, the melting point of the weld zone can be increased to 1250 - 1280°C.

2. The solder according to claim 1, characterized in that, by mass percentage, it includes: Al: 2.8% - 3.5%, Cr: 12.0% - 14.0%, Co: 7.0% - 7.5%, Re: 0.8% - 1.2%, Hf: 0.10% - 0.15%, Ta: 6.5% - 6.8%, W: 3.5% - 3.8%, C: 0.05% - 0.07%, B: 1.5% - 2.0%, Si: 0.5% - 1.0%, the balance is Ni.

3. The solder according to claim 2, characterized in that, by mass percentage, it includes: Al: 2.86% - 3.46%, Cr: 12.06% - 13.5%, Co: 7.40% - 7.43%, Re: 0.83% - 1.01%, Hf: 0.13% - 0.15%, Ta: 6.50% - 6.56%, W: 3.50% - 3.58%, C: 0.062% - 0.069%, B: 1.67% - 1.99%, Si: 0.57% - 0.80%, the balance is Ni.

4. The application of the solder according to any one of claims 1 - 3 in the preparation of a solder product for welding nickel-based single crystal superalloys or in the welding of nickel-based single crystal superalloy joints.

5. A solder product for welding nickel-based single crystal superalloys, characterized in that, it includes the solder according to any one of claims 1 - 3 and a binder.

6. A welding method for nickel-based single crystal superalloy joints, characterized in that, using the solder according to any one of claims 1 - 3 as a filler metal and performing welding by the TLP process.

7. The welding method according to claim 6, characterized in that, it includes: removing impurities on the surface of the joint to be welded of the nickel-based single crystal superalloy; mixing the solder according to any one of claims 1 - 3 and a binder into a paste-like mixture, uniformly coating it on the surface to be welded of the joint, fixing and drying; then performing brazing on the nickel-based single crystal superalloy joint by the TLP process.

8. The welding method according to claim 6 or 7, characterized in that, the TLP process includes: Heat to 500~600 °C, then hold for 20~40 min; then heat to 1000~1050 °C and hold for 10~30 min; heat to the welding temperature of 1250 °C~1290 °C and hold for 8~16 h; after the holding is completed, cool in vacuum to prevent oxidation, and the vacuum degree during the welding process is not less than 5×10 -2 Pa.

9. The welding method according to claim 8, characterized in that, the heating rate is 5 - 10 °C / min from room temperature to 500 - 600 °C, and 15 - 25 °C / min from 500 - 600 °C to the welding temperature.

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