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

Abstract

The application belongs to the technical field of brazing materials, and discloses a high-entropy composite filler metal, a preparation method and application thereof.The high-entropy composite filler metal comprises a nickel-based filler metal matrix and a high-entropy alloy powder, wherein the high-entropy alloy powder comprises Co: 15-25%, Cr: 15-25%, Fe: 15-25% and Ni: 25-45% in terms of atomic percentage.The high-entropy composite filler metal provided by the application maintains a low melting temperature, the high-entropy alloy particles can adjust the joint residual stress caused by the large difference in thermal expansion coefficients of dissimilar materials, play an interface regulation role, affect the generation and distribution of joint brittle phases, and form a special core-shell structure around the high-entropy particles, can break the continuous brittle phase formed by the joint, prevent the crack from expanding, significantly improve the mechanical properties of the joint, and the preparation method of the filler metal is simple and easy to implement, the high-entropy composite filler metal adopts a transient liquid diffusion brazing mode, and the weld structure composition is homogenized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of brazing materials, and relates to a high-entropy composite filler metal, a preparation method and application thereof. BACKGROUND

[0002] TiAl alloy has low density, high specific strength, good high-temperature oxidation resistance and creep resistance, is a very promising lightweight high-temperature structural material, can serve at a high temperature of 750 DEG C to 860 DEG C, is recognized as a substitute material for titanium alloy and high-temperature alloy, and has good application prospects in the fields of aviation, aerospace, nuclear industry, weapons, automobiles and the like.

[0003] In the field of tanks, TiAl alloy can make the turbocharged turbine rotor reduce weight by more than 50%, improve the transient response of the engine, and reduce the power loss of the engine, but the high-temperature mechanical properties and physical properties of TiAl alloy and the 42CrMo medium-carbon quenched and tempered steel used for the turbine supercharger shaft are quite different, resulting in poor weldability.

[0004] At present, the commonly used method for solving the welding of double-alloy complex precision structures is brazing, the main principle of which is that the welded base material and the filler metal are heated as a whole, the brazing temperature is higher than the melting interval of the filler metal and lower than the melting point of the base material, so that the filler metal is melted, and the base material is not melted. Among them, nickel-based filler metal is widely used in the connection of heterogeneous alloys because of its low melting temperature, good wettability, and the brazed joint formed has good high-temperature strength and excellent oxidation resistance and corrosion resistance. However, the elements Ti and Al in TiAl alloy form Ti-Ni, Al-Ti-Ni and other brittle compounds with Ni in the nickel-based filler metal, and the filler metal contains a reducing element B, which is also easy to combine with metal elements to form brittle phases, which is easy to induce cracks in the connection area, resulting in a decrease in the strength of the brazed joint and failing to meet the application requirements. SUMMARY

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

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

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

[0008] The third aspect of the present application provides a welding method, which comprises applying the high-entropy composite filler as described in the first aspect or prepared by the preparation method as described in the second aspect to a welding site and then performing vacuum brazing.

[0009] Compared with the prior art, the present application has at least the following advantages:

[0010] (1) The high-entropy composite filler provided by the present application maintains the advantage of low melting temperature of the nickel-based filler, and forms an intermediate layer of mixed powder of the high-entropy alloy powder with high melting point and the easy-melting nickel-based filler during the welding process of the TiAl alloy and other metals, which promotes the compatibility of the filler and the base material, and the partial dissolution of the high-entropy alloy particles, and the solid-liquid interface of the filler moves during the brazing process, and the base material grows, thereby promoting the formation of stable solid solution or intermetallic compound and improving the shear strength of the brazed joint after the welding of the TiAl alloy and other metals. In addition, the high-entropy alloy particles can also play a role in adjusting the thermal stress caused by the difference in the linear expansion coefficient of the base material during the cooling process of the brazed joint, thereby solving the problem of crack generation caused by the large residual stress at the joint due to the large difference in the thermal expansion coefficient of the TiAl alloy and other metals. At the same time, the high-entropy particles can also play a role in interface regulation, affecting the generation and distribution of brittle phases in the joint, forming a kind of core-shell structure around the high-entropy particles, breaking the continuous brittle phase formed in the joint, and preventing the propagation of cracks.

[0011] (2) In the preparation method of the high-entropy composite filler provided by the present application, only the nickel-based filler matrix and the high-entropy alloy powder need to be ground and uniformly mixed, and the operation process is simple and easy to implement.

[0012] (3) The welding method provided by the present application only needs to apply the high-entropy composite filler to the welding site and then perform vacuum brazing, and the brazing process is simple, which adopts the mode of transient liquid diffusion brazing to homogenize the weld structure composition, ensures the close combination of the connection interface, realizes low-temperature welding and high-temperature service, and at the same time, the welding is performed in a vacuum brazing environment, which can avoid the generation of oxides at the joint and obtain a brazed joint with excellent performance.

[0013] The technical solutions of the present application will be explained and described in more detail below. However, it should be understood that the above-mentioned technical features of the present application and the technical features specifically described in the following (such as the examples) can be combined with each other to form new or preferred technical solutions within the scope of the present application. Due to the limited space, they will not be listed one by one here. Attached Figure Description

[0014] Figure 1 This is the morphology of the high-entropy composite solder powder and the elemental distribution diagram of Al, Cr, Fe, Ni and Si in Embodiment 1 of the present invention;

[0015] Figure 2 This is the morphology of the brazed joint in Embodiment 1 of the present invention and the elemental distribution diagram of Al, Ti, Ni, Fe, C, Cr and Si;

[0016] Figure 3 This is the morphology of the brazed joint in Embodiment 2 of the present invention and the elemental distribution diagram of Al, Ti, Ni, Fe, C, Cr and Si;

[0017] Figure 4 This is the morphology of the brazed joint in Embodiment 3 of the present invention and the elemental distribution diagrams of Al, Ti, Ni, Fe, Si, Cr and Mo;

[0018] Figure 5 This is a diagram showing the morphology of the brazed joint in Comparative Example 1 of the present invention, as well as the elemental distribution of Al, Ti, Ni, Fe, C, Cr, and Si. Detailed Implementation

[0019] As mentioned above, the inventors of this invention have developed the technical solution through long-term and in-depth research and extensive practice, as detailed below.

[0020] 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 comprises Co, Cr, Fe, and Ni, and the composition by atomic percentage is Co: 15%-25%, Cr: 15%-25%, Fe: 15%-25%, and Ni: 25%-45%.

[0021] The high-entropy composite filler material of the present application takes nickel-based filler material as the matrix, maintains the advantage of low melting temperature of the nickel-based filler material, and adds appropriate high-entropy alloy powder. Since the melting temperature of the high-entropy alloy powder is high, the high-entropy composite filler material will form an intermediate layer of mixed powder of the high-entropy alloy powder with high melting point and the fusible nickel-based filler material during the welding of the TiAl alloy and other metals. The intermediate layer is in a solid-liquid state, the nickel-based filler material is in a molten liquid state, and the high-entropy alloy particles are partially dissolved. Thus, the nickel-based filler material penetrates into the base material during the brazing process, promotes the compatibility of the filler material and the base material, the filler material solid-liquid interface moves, and the base material grows, thereby promoting the formation of stable solid solution, ensuring that the filler material has a microstructure mainly composed of solid solution, controlling the reaction between the high-entropy alloy filler material and the base material, reducing the formation of brittle compounds during the welding process, obtaining a weld structure mainly composed of solid solution, and improving the shear strength of the brazed joint after the welding of the TiAl alloy and other metals. In addition, the high-entropy alloy particles can also play a role in adjusting the thermal stress caused by the different linear expansion coefficients of the base material during the cooling process of the brazed joint, thereby solving the problem of crack generation caused by the large residual stress at the joint due to the large difference in thermal expansion coefficient between the TiAl alloy and other metals. At the same time, the high-entropy particles can also play a role in interface regulation, affecting the generation and distribution of brittle phases in the joint, forming a kind of core-shell structure around the high-entropy particles, and also breaking the continuous brittle phase formed in the joint to prevent crack propagation.

[0022] The high-entropy alloy powder added in the high-entropy composite filler material of the present application includes Co, Cr, Fe, and Ni, and the composition by atomic percentage is Co: 15%-25%, Cr: 15%-25%, Fe: 15%-25%, and Ni: 25%-45%. The addition of the high-entropy alloy powder mainly composed of Ni, Cr, Co, and Fe can ensure good compatibility of the high-entropy composite filler material with the high-temperature alloy, and the similar proportion of each element in the high-entropy alloy powder can improve the mixing entropy of the high-entropy alloy powder. The greater the entropy value, the more stable the high-entropy phase, which is beneficial to the formation of solid solution phase or two-phase eutectic structure, thereby improving the shear strength of the brazed joint after the welding of the TiAl alloy and other metals.

[0023] In some embodiments, the nickel-based filler material matrix is 87.5%-97.5% by mass, and the high-entropy alloy powder is 2.5%-12.5% by mass. In this embodiment, the nickel-based filler material matrix accounts for 87.5wt%-97.5wt%, which ensures that the high-entropy composite filler material takes the nickel-based filler material as the matrix, thereby being able to control the melting temperature of the high-entropy composite filler material to be in a relatively low state.

[0024] In some specific embodiments, the nickel-based filler material matrix is 90wt%-95wt%, and the high-entropy alloy powder is 5wt%-10wt%. The use of the above preferred embodiment is beneficial to better reducing the melting temperature of the high-entropy composite filler material and reducing the cost of the high-entropy composite filler material.

[0025] In some embodiments, the nickel-based filler metal base body comprises Ni, B, wherein the nickel-based filler metal base body has a composition of Ni≥70%, B≥1.5% in atomic percentage. In the present embodiment, the Ni≥70%, B≥1.5% of the nickel-based filler metal base body is controlled to ensure that the Ni in the filler metal is fully miscible with the superalloy, the compatibility of the filler metal with the base material, and B as a melting element in the nickel-based filler metal can have a eutectic reaction with Ni, Cr, Fe, Co elements, which can effectively reduce the melting point of the filler metal.

[0026] In some specific embodiments, the nickel-based filler metal base body is FeCrSiB filler metal, wherein the FeCrSiB filler metal has a composition of Ni:≥80%, B: 2.75%-3.5%, Si: 4%-5%, Cr: 6%-8%, Fe: 2.5%-3.5% in atomic percentage. The use of the above preferred embodiment is beneficial to further improve the compatibility of the filler metal with the base material, further reduce the melting temperature of the high-entropy composite filler metal, and at the same time, the FeCrSiB filler metal as a widely used nickel-based filler metal can reduce the raw material cost of the high-entropy composite filler metal.

[0027] 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 the present embodiment, the elements in the high-entropy alloy powder are designed according to the approximate equal atomic ratio, which can further improve the mixing entropy of the high-entropy alloy powder and is further beneficial to form a solid solution phase or a two-phase eutectic structure.

[0028] In some specific embodiments, the atomic ratio of Co, Cr, and Fe in the high-entropy alloy powder is 1:1:1. The use of the above preferred embodiment can maximize the mixing entropy of the high-entropy alloy powder by designing Co, Cr, and Fe in the high-entropy alloy powder according to the equal atomic ratio, which is more beneficial to form a solid solution phase or a two-phase eutectic structure.

[0029] In some embodiments, the metal elements in the high-entropy alloy powder further include X, the 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), and X accounts for 0-30% in atomic percentage. In the present embodiment, the addition of X in the high-entropy alloy powder can improve the compatibility of the high-entropy alloy particles with the base material (TiAl alloy).

[0030] In some specific embodiments, the X is one of Al, Mo, and Ti, and the addition of one of Al, Mo, and Ti in the high-entropy alloy powder can further improve the compatibility with the TiAl alloy and the 42CrMo alloy.

[0031] In some embodiments, if the X is Al, the atomic ratio of X to Ni in the high-entropy alloy powder is 1:2.1. Since the atomic ratio of Al to Ni in the high-entropy alloy powder is 1:2.1, which is a non-equivalent atomic ratio, it is more conducive to form a dual-phase or multi-phase complex solid solution alloy. In addition, the melting point of Al is 660℃, which can reduce the melting temperature of the high-entropy composite filler, and further facilitate the formation of a solid solution phase.

[0032] In some embodiments, if the X is Mo, the atomic ratio of X to Ni in the high-entropy alloy powder is 1:1. By designing the atomic ratio of Mo to Ni to be equivalent, the mixing entropy of the high-entropy alloy powder can be maximized, which is more conducive to the formation of a solid solution phase or a two-phase eutectic structure, and is also more conducive to intermelting with the 42CrMo alloy.

[0033] In some embodiments, if the X is Ti, the atomic ratio of X to Ni in the high-entropy alloy powder is 1:1. By designing the atomic ratio of Ti to Ni to be equivalent, the mixing entropy of the high-entropy alloy powder can be maximized, which is more conducive to the formation of a solid solution phase or a two-phase eutectic structure, and is also more conducive to intermelting with the TiAl alloy.

[0034] The second aspect of the present application provides a preparation method of the high-entropy composite filler described above, which comprises the following steps: step a), weighing the nickel-based filler matrix and the high-entropy alloy powder according to the weight percentage; and step b), grinding and uniformly mixing the raw materials weighed in step a) to obtain the high-entropy composite filler. The preparation method of the high-entropy composite filler provided by the present application only needs to grind and uniformly mix the nickel-based filler matrix and the high-entropy alloy powder, which is simple and easy to operate.

[0035] In some embodiments, the grinding in step b) is performed by using a ball mill, and the grinding time is 3-8h and the abrasive ratio is 2-5. In this embodiment, the use of a ball mill for grinding can make the filler powder mainly spherical, and the particle size of the powder is uniform. The particle size can be controlled to be 100 mesh, 200 mesh, 250 mesh, 300 mesh, and 325 mesh, etc. according to the grinding time.

[0036] In some embodiments, the preparation method further comprises step c) of using a binder to prepare the brazing filler powder in step b) into a paste. In order to make the high-entropy composite brazing filler more convenient to apply during welding, the brazing filler powder is generally prepared into a paste by slowly pouring the binder into the brazing filler powder while stirring until the consistency is appropriate. Generally, the binder is a liquid or gel at room temperature, rapidly dries below 85°C, and maintains its activity at the brazing temperature to play a role in binding the brazing filler powder. The content and properties of the binder affect the flowability of the paste brazing filler, and a suitable binder content allows the paste brazing filler to be easily controlled during application and not to splash violently during heating. Generally, the mass ratio of the binder to the brazing filler powder is about 1:5.

[0037] The third aspect of the present application provides a welding method, which comprises the high-entropy composite brazing filler of the first aspect or the high-entropy composite brazing filler prepared by the method of the second aspect, and then performing vacuum brazing. The welding method provided by the present application only needs to apply the high-entropy composite brazing filler to the welding site and then perform vacuum brazing, and the brazing process is simple. The welding method adopts the mode of transient liquid phase diffusion brazing, homogenizes the composition of the weld, ensures the close combination of the connection interface, realizes low-temperature welding and high-temperature service, and at the same time, the welding is performed in a vacuum brazing environment, which can avoid the generation of oxides at the joint, and obtain a brazed joint with excellent performance.

[0038] In some embodiments, the vacuum brazing is performed in a vacuum brazing furnace, and the vacuum brazing comprises maintaining the vacuum brazing furnace in a vacuum state, heating to the eutectic temperature point of the nickel-based brazing filler base at a certain heating rate and maintaining for 15-30 min, then heating to the melting temperature of the nickel-based brazing filler base at a certain heating rate and maintaining for 10-20 min, then heating to 950-1150°C at a certain heating rate and maintaining for 30-120 min, and then cooling.

[0039] In this embodiment, welding is carried out in a vacuum brazing environment, which can avoid the generation of oxides at the joint and obtain a brazing joint with excellent performance. When the welding temperature reaches the eutectic temperature point of the nickel-based filler metal matrix, the nickel-based filler metal melts to form a liquid phase. When the temperature is higher than the melting temperature of the nickel-based filler metal and enters the holding stage, the elements in the nickel-based filler metal diffuse into the base material, and part of the high-entropy alloy particles dissolves, thereby causing the solid-liquid interface to move and the base material to extend and grow. Due to the diffusion of the reducing elements B and Si in the nickel-based filler metal, the melting point of the liquid filler metal is increased, and then isothermal solidification occurs, in which the solid solution or alloy phase preferentially nucleates and grows around the high-entropy alloy particles. After the holding ends, the intermediate layer gradually cools, and the remaining liquid phase solidifies. Because the linear expansion coefficients of TiAl and other metal alloys differ greatly, during the cooling process, the connection joint generates a large stress, which causes the generation of microcracks in the joint. The high-entropy alloy particles can play a role in adjusting the thermal stress, thereby reducing the generation of cracks in the brazing joint and improving the shear strength of the brazing joint after the welding of TiAl alloy and other metals.

[0040] In some specific embodiments, the heating rate is generally selected to be 8-15℃ / min, preferably 10℃ / min, so as to avoid too fast heating rate, which leads to uneven heating of the filler metal and incomplete melting of the nickel-based filler metal, thereby affecting the element diffusion in the filler metal; if the heating rate is too slow, the brazing time is prolonged, and the brazing processing efficiency is reduced.

[0041] In order to make the present application easier to understand, the technical solutions of the present application will be further described and explained below in conjunction with several embodiments. It should be pointed out that these embodiments are only exemplary descriptions of the present application, and the various reaction participants and process conditions used are typical examples. However, through a large number of experimental verifications by the inventors, other types of reaction participants and other process conditions listed in the foregoing are also applicable and can also achieve the technical effects claimed by the present application.

[0042] The following examples and comparative examples use FeCrSiB filler metal (FeCrSiB powder filler metal with an atomic percentage composition of C: 0.06%; B: 3%; Si: 4.5%; Cr: 7%; Fe: 3%; Ni: 82.44%) as an example to illustrate the welding effect of the filler metal of the examples and comparative examples, wherein the data of brazing TiAl alloy and 42CrMo alloy are used for illustration.

[0043] Example 1

[0044] FeCrSiB filler metal and AlCoCrFeNi 2.1The high-entropy alloy powder is placed in a ball mill for grinding (ball milling parameters: 300 r / min, ball milling for 5 h, and a milling ratio of 3.5) to mix uniformly to obtain a high-entropy composite filler powder. The morphology of the high-entropy composite filler powder is as shown in Figure 1 .

[0045] The filler powder is removed from the ball mill and placed in a vessel. The binder is slowly poured into the filler powder (the mass ratio of the binder to the filler powder is 1:5), and stirring is performed while pouring to obtain a paste-like filler.

[0046] The surfaces to be welded of the TiAl alloy and the 42CrMo alloy are polished with fine sandpaper to remove surface oil stains and oxides, and then placed in ethanol for ultrasonic cleaning for 10 min. The paste-like filler is uniformly coated on the welding positions of the TiAl alloy and the 42CrMo alloy. The TiAl alloy and the 42CrMo alloy coated with the paste-like filler are placed in a vacuum brazing furnace, the vacuum degree of the vacuum brazing furnace is controlled to be 10 -3 Pa, heated to 400 ℃ at a speed of 10 ℃ / min and kept for 20 min, then heated to 800 ℃ at a speed of 10 ℃ / min and kept for 15 min, then heated to 1050 ℃ at a speed of 10 ℃ / min and kept for 90 min, and then cooled with the furnace. The workpiece is taken out, the welding is completed, and the morphology of the brazed joint is as shown in Figure 2 .

[0047] Example 2

[0048] The preparation process and brazing conditions of the high-entropy composite filler powder and the paste-like filler of Example 2 are the same as those of Example 1, except that the high-entropy composite filler is composed of 10wt% CoCrFeNi high-entropy alloy powder and 90wt% FeCrSiB filler.

[0049] The morphology of the brazed joint is as shown in Figure 3 .

[0050] Example 3

[0051] The preparation process and brazing conditions of the high-entropy composite filler powder and the paste-like filler of Example 3 are the same as those of Example 1, except that the high-entropy composite filler is composed of 12.5wt% CoCrFeNiMo high-entropy alloy powder and 87.5wt% FeCrSiB filler.

[0052] The morphology of the brazed joint is as shown in Figure 4 .

[0053] Example 4

[0054] The high-entropy composite filler powder of Example 4 and the paste filler preparation process and brazing conditions are the same as those of Example 1, except that the high-entropy composite filler is composed of 7.5wt% CoCrFeNi high-entropy alloy powder and 92.5wt% FeCrSiB filler.

[0055] Example 5

[0056] The high-entropy composite filler powder of Example 5 and the paste filler preparation process and brazing conditions are the same as those of Example 1, except that the high-entropy composite filler is composed of 2.5wt% AlCoCrFeNi 2.1 high-entropy alloy powder and 97.5wt% FeCrSiB filler.

[0057] Comparative Example 1

[0058] The filler powder and the paste filler preparation process and brazing conditions of Comparative Example 1 are the same as those of Example 1, except that the filler is 100wt% FeCrSiB filler.

[0059] The morphology of the brazed joint is shown in Figure 5 .

[0060] From the change of the filler morphology of Figures 1-4 , it can be seen that the composite filler with the addition of high-entropy alloy powder melts from uniform spherical shape during brazing and penetrates into the base material. Finally, the composite filler makes the alloy weld joint composition uniform, ensuring the close combination of the connection interface, realizing low-temperature welding and high-temperature service, and the undissolved high-entropy particles will break the brittle phase into discontinuous form, which can effectively prevent the crack propagation, and a special core-shell structure is formed around the high-entropy particles. In contrast, Figure 5 , the alloy weld joint composition after brazing is obviously not uniform, and no core-shell structure is found. Figures 2-4

[0061] Analysis of Shear Strength of Brazed Joints

[0062] The shear strength of the brazed joints of Examples 1-5 and Comparative Example 1 was tested according to GB / T 11363 standard, and the results are shown in Table 1.

[0063] Table 1 Average Shear Strength of Brazed Joints of Examples 1-5 and Comparative Example 1

[0064]

[0065] ​The average shear strength of the brazing joint of Example 1 reaches 310 MPa, and the maximum can reach 370 MPa; the average shear strength of the brazing joint of Example 2 reaches 314 MPa, and the maximum can reach 346 MPa, the average shear strength of the brazing joint of Example 3 reaches 294 MPa, and the maximum can reach 369 MPa, the average shear strength of the brazing joint of Example 4 is 262 MPa, the average shear strength of the brazing joint of Example 5 is 257 MPa, all of which significantly exceed the average shear strength of 244 MPa of the brazing joint of Comparative Example 1, wherein the average shear strength of the brazing joint of Example 1 is increased by about 27% compared with Comparative Example 1, the average shear strength of the brazing joint of Example 2 is increased by about 24% compared with Comparative Example 1, and the average shear strength of the brazing joint of Example 3 is increased by about 20% compared with the joint of Comparative Example 1, so that the high-entropy composite filler of the present application can greatly improve the shear strength of the brazing joint.

[0066] The above-described embodiments of the present application are described in detail, and it should be understood that the above-described only the specific embodiments of the present application, and not for limiting the present application, any modification, supplement or similar way of replacement, etc. made within the scope of the principles of the present application, should be included in the scope of protection of the present application.

Claims

1. A high-entropy composite filler metal for brazing TiAl alloy to 42CrMo steel, characterized in that, The nickel-based filler metal base and high-entropy alloy powder, wherein the high-entropy alloy powder comprises Co, Cr, Fe, and Ni, and the atomic percentage composition of the high-entropy alloy powder is Co: 15%-25%, Cr: 15%-25%, Fe: 15%-25%, and Ni: 20%-45%; The nickel-based filler metal base is 87.5%-97.5% and the high-entropy alloy powder is 2.5%-12.5% by mass percentage. The nickel-based filler metal base comprises Ni and B, and the atomic percentage composition of the nickel-based filler metal base is Ni≥70% and B≥1.5%.

2. The high-entropy composite filler metal for brazing TiAl alloy to 42CrMo steel according to claim 1, characterized in that, The nickel-based filler metal base is 90%-95% and the high-entropy alloy powder is 5%-10% by mass percentage.

3. The high-entropy composite filler metal for brazing TiAl alloy to 42CrMo steel according to claim 1, characterized in that, The nickel-based filler metal base is FeCrSiB filler metal, and the atomic percentage composition of the FeCrSiB filler metal is Ni:≥80%, B: 2.75%-3.5%, Si: 4%-5%, Cr: 6%-8%, and Fe: 2.5%-3.5%.

4. The high-entropy composite filler metal for brazing TiAl alloy to 42CrMo steel 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).

5. The high-entropy composite filler metal for brazing TiAl alloy to 42CrMo steel according to claim 1, characterized in that, The atomic ratio of Co, Cr, and Fe in the high-entropy alloy powder is 1:1:

1.

6. The high-entropy composite filler metal for brazing TiAl alloy to 42CrMo steel according to claim 1, characterized in that, The metal element X in the high-entropy alloy powder is one of Al, Mo, and Ti. If the X is Al, the atomic ratio of X and Ni in the high-entropy alloy powder is 1:2.1; if the X is Mo, the atomic ratio of X and Ni in the high-entropy alloy powder is 1:1; and if the X is Ti, the atomic ratio of X and Ni in the high-entropy alloy powder is 1:

1.

7. The preparation method of the high-entropy composite filler for brazing TiAl alloy and 42CrMo steel according to any one of claims 1-6, characterized in that, The preparation method comprises the following steps: a) weighing the nickel-based filler metal base and the high-entropy alloy powder according to the weight percentage; and b) grinding and uniformly mixing the raw materials weighed in step a) to obtain the high-entropy composite filler metal.

8. The preparation method of the high-entropy composite filler for brazing TiAl alloy and 42CrMo steel according to claim 7, characterized in that, The preparation method further comprises step c) of dispensing the filler metal powder in step b) into a paste form by using a binder.

9. A method of welding, characterized by The high-entropy composite filler metal prepared by the preparation method of any one of claims 7-8 is applied to the welding site, and then vacuum brazing is performed.

10. The welding method of claim 9, wherein, The vacuum brazing is performed in a vacuum brazing furnace, and the vacuum brazing comprises maintaining the vacuum brazing furnace in a vacuum state, heating to the eutectic temperature point of the nickel-based filler metal base at a certain heating rate and holding for 15-30 min, then heating to the melting temperature of the nickel-based filler metal base at a certain heating rate and holding for 10-20 min, then heating to 950-1150℃ at a certain heating rate and holding for 30-120 min, and then cooling, wherein the heating rate is 8-15℃ / min.

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