High-entropy composite brazing filler metal and preparation method and application thereof

Abstract

The invention belongs to the technical field of brazing materials, and discloses high-entropy composite brazing filler metal and a preparation method and application thereof. The high-entropy composite brazing filler metal comprises a nickel-based brazing filler metal matrix and high-entropy alloy powder, and the high-entropy alloy powder comprises, by atomic percent, 15%-25% of Co, 15%-25% of Cr, 15%-25% of Fe and 25%-45% of Ni. According to the high-entropy composite brazing filler metal, the low melting temperature is kept, the high-entropy alloy particles can adjust joint residual stress caused by the large difference of thermal expansion coefficients of dissimilar materials, the interface regulation and control effect is achieved, generation and distribution of joint brittle phases are affected, a special core-shell structure is formed around the high-entropy particles, and therefore the high-entropy composite brazing filler metal can be obtained. A continuous brittle phase formed by a joint can be broken, crack propagation is prevented, the mechanical property of the joint is remarkably improved, the brazing filler metal preparation method is simple and easy to implement, and the high-entropy composite brazing filler metal adopts an instantaneous liquid diffusion brazing mode, so that weld joint structure components are homogenized.

Description

Technical Field

[0001] The invention belongs to the technical field of brazing materials and relates to a high-entropy composite brazing material, a preparation method and application thereof. Background Art

[0002] TiAl alloy has low density, high specific strength, good high-temperature oxidation resistance and creep resistance. It is a very promising lightweight and high-temperature resistant structural material. It can serve at high temperatures of 750℃ to 860℃. It is recognized as an alternative material to titanium alloys and high-temperature alloys, and has good application prospects in aviation, aerospace, nuclear industry, weapons, automobiles and other fields.

[0003] For example, in the tank field, TiAl alloy can reduce the weight of the turbocharger turbine rotor by more than 50%, improve the transient response of the engine, and reduce the engine's power loss. However, the high-temperature mechanical and physical properties of TiAl alloy and the 42CrMo medium-carbon tempered steel used in the turbocharger shaft are quite different, resulting in poor weldability.

[0004] Currently, the common method for welding complex and precise dual-alloy structures is brazing. The main principle is that the base metal and the brazing filler metal are heated as a whole, and the brazing temperature is higher than the melting range of the brazing filler metal and lower than the melting point of the base metal, so that the brazing filler metal melts while the base metal does not melt. Among them, nickel-based brazing filler metals are widely used in heterogeneous alloy connections because of their low melting temperature and good wettability. The brazed joints formed have good high-temperature strength and excellent oxidation resistance and corrosion resistance. However, the elements Ti and Al in the TiAl alloy form brittle compounds such as Ti-Ni and Al-Ti-Ni with the Ni in the nickel-based brazing filler metal. In addition, the brazing filler metal contains the melting-reducing element B, which is also easy to combine with the metal elements to form a brittle phase, which can easily induce cracks in the connection area, resulting in a reduction in the strength of the brazed joint and failing to meet the application requirements. Summary of the Invention

[0005] The main purpose of the present invention is to provide a high-entropy composite brazing filler metal, a preparation method and an application thereof. The high-entropy composite brazing filler metal has a low melting temperature and the shear strength of the brazed joint after the TiAl alloy is welded to other metals is high, thereby solving the problem of large residual stress at the joint due to the large difference in thermal expansion coefficient between the TiAl alloy and other metals, which leads to cracks.

[0006] To achieve the above-mentioned purpose of the invention, the first aspect of the present invention provides a high-entropy composite solder, comprising a nickel-based solder matrix and a high-entropy alloy powder, wherein the high-entropy alloy powder includes Co, Cr, Fe, and Ni, and the composition in atomic percentage is Co: 15%-25%, Cr: 15%-25%, Fe: 15%-25%, and Ni: 25%-45%.

[0007] The second aspect of the present invention provides a method for preparing the high-entropy composite solder as described in the first aspect, the preparation method comprising: step a), weighing a nickel-based solder matrix and a high-entropy alloy powder according to weight percentage; step b), grinding and uniformly mixing the raw materials weighed in step a) to obtain a high-entropy composite solder.

[0008] The third aspect of the present invention provides a welding method, which comprises applying the high entropy composite solder described in the first aspect or the high entropy composite solder prepared by the preparation method described in the second aspect to a part to be welded and then performing vacuum brazing.

[0009] Compared with the prior art, the present invention has at least the following advantages: (1) The high entropy composite brazing material provided by the present invention maintains the advantage of the low melting temperature of the nickel-based brazing material. At the same time, an intermediate layer of mixed powder of high entropy alloy powder with a higher melting point and fusible nickel-based brazing material is formed during the welding process of TiAl alloy and other metals, which not only promotes the compatibility of the brazing material and the base material, but also partially dissolves the high entropy alloy particles. During the brazing process, the solid-liquid interface of the brazing material moves, and the base material extends and grows, thereby promoting the formation of a stable solid solution or intermetallic compound, and improving the shear strength of the brazed joint after the TiAl alloy and other metals are welded. In addition, the high entropy alloy particles can also play a role in regulating the thermal stress caused by the different linear expansion coefficients of the base material during the cooling process of the brazing joint, thereby solving the problem of large residual stress at the joint due to the large difference in thermal expansion coefficients between TiAl alloy and other metals, which leads to cracks. At the same time, the high entropy particles can also play a role in interface regulation, affecting the generation and distribution of the brittle phase of the joint, forming a core-shell structure around the high entropy particles, which can break up the continuous brittle phase formed in the joint and prevent the expansion of cracks.

[0010] (2) In the preparation method of the high-entropy composite solder provided by the present invention, it is only necessary to grind and mix the nickel-based solder matrix and the high-entropy alloy powder uniformly, and the operation process is simple and easy.

[0011] (3) The welding method provided by the present invention only requires applying high-entropy composite brazing material to the part to be welded and then performing vacuum brazing. The brazing process is simple. It adopts the method of instantaneous liquid diffusion brazing to homogenize the composition of the weld structure, ensure the close bonding of the connection interface, and realize low-temperature welding and high-temperature service. At the same time, welding is performed in a vacuum brazing environment, which can avoid the formation of oxides at the joint and obtain a brazed joint with excellent performance.

[0012] The technical solutions of the present invention will be explained in more detail below. However, it should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features described in detail below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described here one by one. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The morphology of the high entropy composite solder powder and the distribution of Al, Cr, Fe, Ni, and Si elements in Example 1 of the present invention are shown; Figure 2 1 is the morphology of the brazed joint and the distribution of Al, Ti, Ni, Fe, C, Cr, and Si elements in Example 1 of the present invention; Figure 3 1. The morphology of the brazed joint of Example 2 of the present invention and the distribution diagram of Al, Ti, Ni, Fe, C, Cr, and Si elements; Figure 4 1. The morphology of the brazed joint and the distribution of Al, Ti, Ni, Fe, Si, Cr, and Mo elements of Example 3 of the present invention; Figure 5 This is the morphology of the brazing joint of comparative example 1 of the present invention and the distribution diagram of Al, Ti, Ni, Fe, C, Cr, and Si elements; DETAILED DESCRIPTION

[0014] As mentioned above, the inventor of this case was able to propose the technical solution of the present invention after long-term and in-depth research and extensive practice, which is detailed below.

[0015] One aspect of the present invention provides a high-entropy composite solder, comprising a nickel-based solder matrix and high-entropy alloy powder, wherein the high-entropy alloy powder includes Co, Cr, Fe, and Ni, and the composition in atomic percentage is Co: 15%-25%, Cr: 15%-25%, Fe: 15%-25%, and Ni: 25%-45%.

[0016] The high-entropy composite solder of the present invention uses a nickel-based solder as a matrix, maintains the advantage of the low melting temperature of the nickel-based solder, and simultaneously adds an appropriate amount of high-entropy alloy powder. Since the high-entropy alloy powder has a high melting temperature, the high-entropy composite solder will form an intermediate layer of mixed powder of the high-entropy alloy powder with a relatively high melting point and the fusible nickel-based solder during the welding process of the TiAl alloy with other metals, wherein the intermediate layer is in a solid-liquid state, the nickel-based solder is in a molten liquid state, and the high-entropy alloy particles are partially dissolved. In this way, during the brazing process, the nickel-based solder penetrates into the base material, promotes the compatibility of the solder and the base material, moves the solid-liquid interface of the solder, and extends and grows the base material, thereby promoting the formation of a stable solid solution, ensuring that the solder has a microstructure dominated by the solid solution, controlling the reaction of the high-entropy alloy solder with the base material, reducing the formation of brittle compounds during the welding process, obtaining a weld structure dominated by the solid solution, and improving the shear strength of the brazed joint after the TiAl alloy is welded to the other metal. In addition, high-entropy alloy particles can also play a role in regulating the thermal stress caused by the different linear expansion coefficients of the parent materials during the cooling process of the brazed joint, thereby solving the problem of large residual stresses in the joint caused by the large difference in thermal expansion coefficients between TiAl alloys and other metals, which leads to cracks. At the same time, high-entropy particles can also play a role in interface regulation, affecting the formation and distribution of brittle phases in the joint. Forming a core-shell structure around the high-entropy particles can also break up the continuous brittle phase formed in the joint and prevent the propagation of cracks.

[0017] The high-entropy alloy powder added to the high-entropy composite solder of the present invention includes Co, Cr, Fe, and Ni, and the composition in atomic percentage is Co: 15%-25%, Cr: 15%-25%, Fe: 15%-25%, and Ni: 25%-45%. The addition of high-entropy alloy powder mainly composed of Ni, Cr, Co, and Fe can ensure good compatibility between the high-entropy composite solder and the high-temperature alloy. At the same time, the design of similar ratios of various elements in the high-entropy alloy powder can increase the mixing entropy of the high-entropy alloy powder. The larger the entropy value, the more stable the high-entropy phase, which is conducive to the formation of a solid solution phase or a two-phase eutectic structure, thereby improving the shear strength of the brazed joint after the TiAl alloy is welded to the other metal.

[0018] In some embodiments, the nickel-based solder matrix accounts for 87.5%-97.5% by weight, and the high-entropy alloy powder accounts for 2.5%-12.5% ​​by weight. In this embodiment, the nickel-based solder matrix accounts for 87.5wt%-97.5wt%, ensuring that the nickel-based solder serves as the matrix of the high-entropy composite solder, thereby controlling the melting temperature of the high-entropy composite solder to be at a low level.

[0019] In some specific embodiments, the nickel-based solder matrix is ​​90wt%-95wt%, and the high-entropy alloy powder is 5wt%-10wt%. The above preferred embodiment is conducive to better reducing the melting temperature of the high-entropy composite solder and reducing the cost of the high-entropy composite solder.

[0020] In some embodiments, the nickel-based solder matrix includes Ni and B, wherein the nickel-based solder matrix has a composition of Ni ≥ 70% and B ≥ 1.5% by atomic percentage. In this embodiment, the nickel-based solder matrix is ​​controlled to have a Ni ≥ 70% and a B ≥ 1.5% to ensure that the Ni in the solder is fully soluble in the high-temperature alloy and that the solder is compatible with the base material. Furthermore, B, as a melting point-depressing element in the nickel-based solder, can undergo a eutectic reaction with Ni, Cr, Fe, and Co, effectively lowering the solder's melting point.

[0021] In some specific embodiments, the nickel-based brazing filler metal matrix is ​​a FeCrSiB brazing filler metal, wherein the atomic percentage composition of the FeCrSiB brazing filler metal is as follows: Ni: ≥80%, B: 2.75%-3.5%, Si: 4%-5%, Cr: 6%-8%, and Fe: 2.5%-3.5%. Adopting this preferred embodiment further improves the compatibility between the brazing filler metal and the parent material, further lowering the melting temperature of the high-entropy composite brazing filler metal. Furthermore, as a widely used nickel-based brazing filler metal, the FeCrSiB brazing filler metal can reduce the raw material cost of the high-entropy composite brazing filler metal.

[0022] In some embodiments, the atomic ratio of Co, Cr, and Fe in the high-entropy alloy powder is 1:(0.9-1.1):(0.9-1.1). In this embodiment, the elements in the high-entropy alloy powder are designed to be approximately equiatomic, which can further increase the mixing entropy of the high-entropy alloy powder and further facilitate the formation of a solid solution phase or a two-phase eutectic structure.

[0023] In some specific embodiments, the atomic ratio of Co, Cr, and Fe in the high entropy alloy powder is 1:1:1. By adopting the above preferred embodiment, the atomic ratio of Co, Cr, and Fe in the high entropy alloy powder is designed to be equal, which can maximize the mixing entropy of the high entropy alloy powder and is more conducive to the formation of a solid solution phase or a two-phase eutectic structure.

[0024] In some embodiments, the metal element in the high-entropy alloy powder further includes X, where X is a metal element that forms a high-entropy alloy with CoCrFeNi, wherein the atomic ratio of X to Ni in the high-entropy alloy powder is (0-1.1):(0.9-2.2); in terms of atomic percentage, X: 0-30%; in this embodiment, adding X to the high-entropy alloy powder can improve the compatibility of the high-entropy alloy particles with the base material (TiAl alloy).

[0025] In some specific embodiments, X is one of Al, Mo, and Ti. Adding one of Al, Mo, and Ti to the high entropy alloy powder can further improve the compatibility with TiAl alloy and 42CrMo alloy.

[0026] In some specific embodiments, if X is Al, the atomic ratio of X to Ni in the high entropy alloy powder is 1:2.1. Because the atomic ratio of Al to Ni in the high entropy alloy powder is 1:2.1, which is a non-equiatomic ratio, it is more conducive to the formation of a two-phase or multi-phase complex solid solution alloy, and the melting point of Al is 660°C, which can reduce the melting temperature of the high entropy composite solder, further facilitating the formation of a solid solution phase.

[0027] In some specific embodiments, if X is Mo, the atomic ratio of X to Ni in the high entropy alloy powder is 1:1. The design according to the atomic ratio of Mo and Ni can further maximize the mixing entropy of the high entropy alloy powder, which is more conducive to the formation of a solid solution phase or a two-phase eutectic structure, and is more conducive to mutual melting with the 42CrMo alloy.

[0028] In some specific embodiments, if X is Ti, the atomic ratio of X to Ni in the high entropy alloy powder is 1:1. The design according to the atomic ratio of Ti and Ni can further maximize the mixing entropy of the high entropy alloy powder, which is more conducive to the formation of a solid solution phase or a two-phase eutectic structure, and is more conducive to mutual melting with TiAl alloy.

[0029] A second aspect of the present invention provides a method for preparing the high-entropy composite solder described above, comprising: step a) weighing a nickel-based solder matrix and a high-entropy alloy powder according to weight percentage; and step b) grinding and mixing the raw materials weighed in step a) to obtain the high-entropy composite solder. The high-entropy composite solder preparation method provided by the present invention requires only grinding and mixing the nickel-based solder matrix and the high-entropy alloy powder, resulting in a simple and easy operation.

[0030] In some embodiments, the grinding in step b) is performed using a ball mill for 3-8 hours at a grinding ratio of 2-5. In this embodiment, the use of a ball mill can make the solder powder primarily spherical and have a uniform particle size. The particle size can be controlled to 100 mesh, 200 mesh, 250 mesh, 300 mesh, and 325 mesh, depending on the grinding time.

[0031] In some embodiments, the preparation method further comprises step c) using a binder to prepare the solder powder from step b) into a paste. To facilitate application of the high-entropy composite solder during soldering, the solder powder is typically prepared into a paste. This process involves slowly pouring the binder into the solder powder, stirring while pouring, until the desired consistency is achieved. Generally, the binder is a liquid or gel at room temperature, dries rapidly below 85°C, and maintains its activity at the brazing temperature, serving to bind the solder powder. The binder content and properties affect the fluidity of the paste. An appropriate binder content ensures easy control during application and prevents violent spattering during heating. Generally, the mass ratio of binder to solder powder is approximately 1:5.

[0032] The third aspect of the present invention provides a welding method, comprising applying the high-entropy composite brazing material described in the first aspect or the high-entropy composite brazing material obtained by the method described in the second aspect to the part to be welded and then performing vacuum brazing. The welding method provided by the present invention only requires applying the high-entropy composite brazing material to the part to be welded and then performing vacuum brazing. The brazing process is simple. It adopts the method of instantaneous liquid diffusion brazing to homogenize the weld microstructure and ensure the close bonding of the connection interface, realize low-temperature welding and high-temperature service, and at the same time, the use of a vacuum brazing environment to weld can avoid the formation of oxides at the joint, thereby obtaining a brazed joint with excellent performance.

[0033] In some embodiments, the vacuum brazing is performed in a vacuum brazing furnace, which includes maintaining the vacuum brazing furnace in a vacuum state, heating to the eutectic temperature of the nickel-based brazing material substrate at a certain heating rate and keeping it warm for 15-30 minutes, then heating to the melting temperature of the nickel-based brazing material substrate at a certain heating rate and keeping it warm for 10-20 minutes, then heating to 950-1150°C at a certain heating rate and keeping it warm for 30-120 minutes, and then cooling.

[0034] In this embodiment, welding is performed under a vacuum brazing environment to avoid the formation of oxides at the joints and obtain a brazed joint with excellent performance. When the welding temperature reaches the eutectic temperature of the nickel-based brazing material matrix, the nickel-based brazing material melts to form a liquid phase. When the temperature is higher than the melting temperature of the nickel-based brazing material and enters the insulation stage, the elements in the nickel-based brazing material diffuse into the parent material, and the high-entropy alloy particles partially dissolve, thereby causing the solid-liquid interface to move and the parent material to extend and grow. Due to the diffusion of the melting-reducing elements B and Si in the nickel-based brazing material, the melting point of the liquid brazing material is increased, and isothermal solidification occurs, wherein the solid solution or alloy phase preferentially nucleates and grows around the high-entropy alloy particles. After the insulation is completed, the middle layer gradually cools and the remaining liquid phase solidifies. Since the linear expansion coefficients of TiAl and other metal alloys differ greatly, during the cooling process, the connecting joint will produce large stresses, resulting in the generation of microcracks in the joint. The high-entropy alloy particles can play a role in regulating thermal stress, thereby reducing the generation of cracks in the brazed joint and improving the shear strength of the brazed joint after the TiAl alloy is welded to other metals.

[0035] In some specific embodiments, the heating rate is generally selected to be 8-15°C / min, preferably 10°C / min. This can avoid the heating rate being too fast, which will lead to uneven heating of the solder and incomplete melting of the nickel-based solder, which will affect the diffusion of elements in the solder. If the heating rate is too slow, the brazing time will be extended and the brazing process efficiency will be reduced.

[0036] In order to make the present invention easier to understand, the technical solution of the present invention will be further explained in conjunction with several embodiments below. It should be pointed out that these embodiments are only exemplary descriptions of the present invention, and the various reaction participants and process conditions used therein are relatively typical examples. However, after a large number of experiments and verifications by the inventors of this case, other types of reaction participants and other process conditions listed above are also applicable and can also achieve the technical effects claimed in the present invention.

[0037] The nickel-based solder matrix in the following embodiments and comparative examples is illustrated by taking FeCrSiB solder (the atomic percentage composition of FeCrSiB powder solder is C: 0.06%; B: 3%; Si: 4.5%; Cr: 7%; Fe: 3%; Ni: 82.44%) as an example to verify the welding effect of the solder of the embodiments and comparative examples, among which the data of brazing TiAl alloy and 42CrMo alloy are used for illustration.

[0038] Example 1 Weigh FeCrSiB solder and AlCoCrFeNi in the proportion of 95wt% and 5wt% respectively. 2.1 The high entropy alloy powder was placed in a ball mill and ground (ball milling parameters were 300 r / min, ball milling for 5 hours, grinding ratio was 3.5) to obtain high entropy composite solder powder. The morphology of the high entropy composite solder powder is shown in FIG. Figure 1 shown.

[0039] Remove the solder powder from the ball mill and place it in a container. Slowly pour the binder into the solder powder (the mass ratio of binder to solder powder is 1:5) while stirring to obtain a paste-like solder.

[0040] The surfaces of the TiAl alloy and 42CrMo alloy to be welded were polished with fine sandpaper to remove surface oil and oxides, and then placed in ethanol and ultrasonically cleaned for 10 minutes. The paste solder was evenly applied to the parts of the TiAl alloy and 42CrMo alloy to be welded. The TiAl alloy and 42CrMo alloy coated with the paste solder were placed in a vacuum brazing furnace, and the vacuum degree of the vacuum brazing furnace was controlled to 10 -3 Pa, heated to 400 °C at a rate of 10 °C / min and kept warm for 20 min, then heated to 800 °C at a rate of 10 °C / min and kept warm for 15 min, then heated to 1050 °C at a rate of 10 °C / min and kept warm for 90 min, then cooled with the furnace, took out the workpiece, and completed the welding. The morphology of the brazed joint is as follows Figure 2 shown.

[0041] Example 2 The preparation process and brazing conditions of the high-entropy composite solder powder and paste solder of Example 2 are the same as those of Example 1, except that the high-entropy composite solder consists of 10wt% CoCrFeNi high-entropy alloy powder and 90wt% FeCrSiB solder.

[0042] The morphology of the brazed joint is as follows Figure 3 shown.

[0043] Example 3 The preparation process and brazing conditions of the high-entropy composite solder powder and paste solder of Example 3 are the same as those of Example 1, except that the high-entropy composite solder consists of 12.5wt% CoCrFeNiMo high-entropy alloy powder and 87.5wt% FeCrSiB solder.

[0044] The morphology of the brazed joint is as follows Figure 4 shown.

[0045] Example 4 The preparation process of the high-entropy composite solder powder and the paste solder and the brazing conditions of Example 4 are the same as those of Example 1, except that the high-entropy composite solder consists of 7.5wt% CoCrFeNiTi high-entropy alloy powder and 92.5wt% FeCrSiB solder.

[0046] Example 5 The preparation process and brazing conditions of the high entropy composite solder powder and paste solder of Example 5 are the same as those of Example 1, except that the high entropy composite solder is composed of 2.5wt% AlCoCrFeNi 2.1 It is composed of high entropy alloy powder and 97.5wt% FeCrSiB solder.

[0047] Comparative Example 1 The preparation process of the solder powder and the paste solder and the brazing conditions of Comparative Example 1 are the same as those of Example 1, except that the solder is 100 wt % FeCrSiB solder.

[0048] The morphology of the brazed joint is as follows Figure 5 shown.

[0049] from Figure 1-4 From the perspective of the changes in the solder morphology, the composite solder with high entropy alloy powder melts from a uniform spherical shape during the brazing process and penetrates into the base material. Finally, the composite solder makes the alloy weld structure uniform, ensuring the close bonding of the connection interface and achieving low-temperature welding and high-temperature service. The incompletely dissolved high-entropy particles break the brittle phase into a discontinuous state, which can effectively prevent the expansion of cracks and form a special core-shell structure around the high-entropy particles. Figure 5 Relative to Figure 2-4 The microstructure of the alloy weld after brazing is obviously uneven, and no core-shell structure is found.

[0050] Shear Strength Analysis of Brazed Joints The shear strength of the brazed joints of Examples 1-5 and Comparative Example 1 was tested according to GB / T 11363. The results are shown in Table 1.

[0051] Table 1 Average shear strength of the brazed joints of Examples 1-5 and Comparative Example 1 The average shear strength of the brazed joint of Example 1 reaches 310 MPa, and can reach a maximum of 370 MPa; the average shear strength of the brazed joint of Example 2 reaches 314 MPa, and can reach a maximum of 346 MPa; the average shear strength of the brazed joint of Example 3 reaches 294 MPa, and can reach a maximum of 369 MPa; the average shear strength of the brazed joint of Example 4 is 262 MPa, and the average shear strength of the brazed joint of Example 5 is 257 MPa, which are all significantly higher than the average shear strength of the brazing of Comparative Example 1 of 244 MPa. The average shear strength of the brazed joint of Example 1 is increased by about 27% compared with that of Comparative Example 1, the average shear strength of the brazed joint of Example 2 is increased by about 24% compared with that of Comparative Example 1, and the average shear strength of the brazed joint of Example 3 is increased by about 20% compared with the joint of Comparative Example 1. Therefore, the use of the high-entropy composite solder of the present invention can greatly improve the shear strength of the brazed joint.

[0052] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high entropy composite solder, characterized in that: The invention comprises a nickel-based solder matrix and a high-entropy alloy powder, wherein the high-entropy alloy powder comprises Co, Cr, Fe, and Ni. Calculated by atomic percentage, the high-entropy alloy powder comprises: Co: 15%-25%, Cr: 15%-25%, Fe: 15%-25%, and Ni: 25%-45%.

2. The high entropy composite solder according to claim 1, characterized in that In terms of mass percentage, the nickel-based solder matrix is ​​87.5%-97.5%, and the high entropy alloy powder is 2.5%-12.5%; Preferably, the nickel-based solder matrix is ​​90%-95%, and the high entropy alloy powder is 5%-10%.

3. The high entropy composite solder according to claim 1, characterized in that The nickel-based solder matrix comprises Ni and B, wherein the nickel-based solder matrix has a composition of Ni≥70% and B≥1.5% in terms of atomic percentage.

4. The high entropy composite solder according to claim 3, characterized in that The nickel-based solder matrix is ​​FeCrSiB solder, wherein the composition of the FeCrSiB solder in atomic percentage is Ni: ≥80%, B: 2.75%-3.5%; Si: 4%-5%; Cr: 6%-8%; Fe: 2.5%-3.5%.

5. The high entropy composite solder according to claim 1, characterized in that The atomic ratio of Co, Cr and Fe in the high entropy alloy powder is 1: (0.9-1.1): (0.9-1.1); Preferably, the atomic ratio of Co, Cr and Fe in the high entropy alloy powder is 1:1:

1.

6. The high entropy composite solder according to claim 1, characterized in that The high entropy alloy powder further includes X, wherein X is a metal element that forms a high entropy alloy with CoCrFeNi, and the atomic ratio of X to Ni is (0-1.1):(0.9-2.2). In terms of atomic percentage, the high entropy alloy powder contains X: 0-30%; Preferably, X is one of Al, Mo, and Ti; Further preferably, if the X is Al, the atomic ratio of X to Ni in the high entropy alloy powder is 1:2.1; if the X is Mo, the atomic ratio of X to Ni in the high entropy alloy powder is 1:1; if the X is Ti, the atomic ratio of X to Ni in the high entropy alloy powder is 1:

1.

7. The method for preparing a high entropy composite solder according to any one of claims 1 to 6, wherein: The preparation method comprises: step a), weighing a nickel-based solder matrix and a high-entropy alloy powder according to weight percentage; and step b), grinding and uniformly mixing the raw materials weighed in step a) to obtain a high-entropy composite solder.

8. The method for preparing a high entropy composite solder according to claim 7, wherein: The preparation method further comprises the step c) of mixing the solder powder in the step b) into a paste using a binder.

9. A welding method, characterized in that: The high entropy composite solder according to any one of claims 1 to 6 or the high entropy composite solder prepared by the method according to claims 7 to 8 is applied to the part to be welded and then vacuum brazing is performed.

10. The welding method according to claim 9, wherein The vacuum brazing is performed in a vacuum brazing furnace, wherein the vacuum brazing furnace is kept in a vacuum state, and the process is heated to the eutectic temperature of the nickel-based brazing material substrate at a certain heating rate and kept at that temperature for 15-30 minutes, and then heated to the melting temperature of the nickel-based brazing material substrate at a certain heating rate and kept at that temperature for 10-20 minutes, and then heated to 950-1150° C. at a certain heating rate and kept at that temperature for 30-120 minutes, and then cooled; Preferably, the heating rate is 8-15°C / min.

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