A high-entropy alloy filler metal for high-temperature alloy and carbon material dissimilar brazing connection, a preparation method and application thereof

Abstract

The application discloses a high-entropy alloy filler for heterogenous brazing connection of high-temperature alloy and carbon material and a preparation method and application thereof, the high-entropy alloy filler is composed of Ti, Co, Cr, Fe and Ni; the atomic percentage of Ti, Co, Cr, Fe and Ni is (0.6-0.65):(0.9-1.1):(0.9-1.1):(0.9-1.1):(2.0-2.1). The non-equal-atomic-ratio TiCoCrFeNi high-entropy alloy filler provided by the application is a eutectic high-entropy alloy filler with excellent plasticity and strength, after brazing by using the high-entropy alloy filler, through high-temperature metallurgical reaction and element diffusion, part of high-entropy solid solution phases are reserved in the center position of the brazing joint, the high mixing entropy inhibits the generation of brittle carbides in the joint, and the mechanical properties of the joint are significantly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of brazing, in particular to a high-entropy alloy filler metal for hetero-brazing connection of high-temperature alloy and carbon material, and a preparation method and application thereof. BACKGROUND

[0002] Carbon materials such as graphite and C / C composites have many ideal properties, such as high-temperature stability, high thermal ablation resistance, excellent thermal conductivity and good mechanical properties. Therefore, they have attracted widespread attention as light-weight thermal structural materials in the aerospace field, such as rocket engines and solid rocket nozzles. However, C / C composites have the characteristics of high brittleness and poor machinability, which means that they are difficult to be manufactured into complex C / C structural parts. High-temperature carbon materials usually need to be combined with themselves or other materials to form composite components for industrial applications. Therefore, high-temperature-resistant and high-toughness connecting joints are the key to expanding the application range of C / C composites.

[0003] Active metal brazing is the most commonly used method for connecting carbon materials at present, which has the advantages of simple process and reliable connecting joints in a short time. Currently, Ti-based and Ag-based traditional filler metals are often used for brazing connection of carbon materials. However, the active metal elements Ti and Cr contained in the traditional filler metals are easy to generate a large amount of brittle carbides at the interface and inside the joint, which greatly weakens the mechanical properties of the joint, especially the high-temperature service performance, and seriously limits the application of carbon materials. Therefore, in view of the problem of low joint bonding performance of existing filler metals, it is urgent to develop new alloy filler metals to realize reliable connection of carbon materials with high strength.

[0004] High-entropy alloys are alloys formed by 5 or more elements, with the content of each element being about 5at.% to 35at.%. Unlike traditional alloys, high-entropy alloys have high mixing entropy, random atomic and chemical composition, which promotes the formation of simple single-phase solid solution and produces strong solid solution strengthening effect, and enhances the resistance to deformation and fracture. The diffusion of atoms in the alloy is extremely difficult due to the slow diffusion effect, which can inhibit the formation of brittle phases at the ceramic-metal interface during brazing, reduce the deformation and residual stress in the joint, and significantly improve the mechanical properties such as strength and hardness of the alloy, thereby improving the performance of the joint. The lattice distortion effect affects the mechanical properties of the alloy by adjusting the lattice structure, changing the dislocation density and grain boundary energy of the alloy. Severe lattice distortion effect can lead to local strengthening of the alloy, and the alloy has stronger resistance to dislocation than traditional alloys, which improves the hardness and deformation resistance of the alloy, and is beneficial to the improvement of the mechanical properties of the joint. The "cocktail" effect increases the complexity and diversity of the joint, improves the stability and deformation resistance of the material, and ensures the long-term stability and reliability of the joint, thereby expanding the range and application value of the brazed joint. The "cocktail" effect of high-entropy alloys provides higher performance material selection and application guarantee for interface connection. During solidification, the long-range diffusion of randomly arranged atoms of each element is slow, the nucleation and growth of solute redistribution process is delayed, and nanophase is easily formed. Some high-entropy alloys also have amorphous tendency, high strength and toughness, low melting point effect, and narrow solid-liquid phase range, which makes it possible to use high-entropy alloys as brazing filler metal.

[0005] Fu et al. used eutectic high-entropy alloy Nb0.74CoCrFeNi2 as brazing filler metal, and successfully brazed C / C composite material, but due to the good reactivity of Nb and Cr elements with carbon, a brittle Nb(s,s) layer was generated on the C / C base material side, and the thickness of the brittle layer increased with temperature. When the connection temperature was 1260℃, the shear strength of the joint was only 32.3MPa, and the fracture mainly occurred at the interface, showing a brittle fracture mode. The existing process methods have not fundamentally improved the brittleness of the interface metal compound, therefore, how to effectively reduce the intrinsic brittleness of the interface metal compound is a key problem to be solved for improving the strength and reliability of the brazed joint and obtaining brazed joints that meet the requirements of practical applications. SUMMARY

[0006] The present application aims to overcome the above-mentioned defects existing in the prior art, and provides a high-entropy alloy filler for hetero-brazing connection of high-temperature alloy and carbon material, and a preparation method and application thereof.The non-equiatomic ratio TiCoCrFeNi high-entropy alloy filler provided by the present application is a eutectic high-entropy alloy filler with excellent plasticity and strength, and after brazing by using the same, part of high-entropy solid solution phase is reserved in the center position of the brazed joint through high-temperature metallurgical reaction and element diffusion, the high mixing entropy inhibits the generation of brittle carbide in the joint, and the mechanical property of the joint is significantly improved.The present application can effectively control the interdiffusion of the base material and the filler element in the brazing connection process by means of the sluggish diffusion effect of the high-entropy alloy, so as to inhibit the thickness of the interface reaction layer and improve the bonding strength.

[0007] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0008] A high-entropy alloy filler for hetero-brazing connection of high-temperature alloy and carbon material, the high-entropy alloy filler is composed of Ti, Co, Cr, Fe and Ni; the atomic percentage of Ti, Co, Cr, Fe and Ni is (0.6-0.65):(0.9-1.1):(0.9-1.1):(0.9-1.1):(2.0-2.1).

[0009] The present application also discloses a preparation method of the high-entropy alloy filler for hetero-brazing connection of high-temperature alloy and carbon material as described above, comprising the following steps:

[0010] The Ti, Co, Cr, Fe and Ni are mixed according to the atomic percentage of (0.6-0.65):(0.9-1.1):(0.9-1.1):(0.9-1.1):(2.0-2.1) to obtain a metal raw material;

[0011] The metal raw material is subjected to high-energy ball milling by using a mechanical alloying method to obtain the high-entropy alloy filler.

[0012] The present application also discloses a brazing method of the high-entropy alloy filler for hetero-brazing connection of high-temperature alloy and carbon material as described above, or the high-entropy alloy filler for hetero-brazing connection of high-temperature alloy and carbon material prepared by the preparation method as described above, comprising the following steps:

[0013] (1) the base material to be welded is polished and cleaned by using SiC sandpaper to obtain a pretreated base material;

[0014] (2) the high-entropy alloy powder and anhydrous ethanol are mixed to obtain a paste-like filler;

[0015] (3) coating the paste brazing filler metal on the surface of the pretreated base material to form a welding assembly in a sandwich structure of carbon material / brazing filler metal interlayer / high-temperature alloy;

[0016] (4) placing the welding assembly into a graphite mold, applying a pressure of 0.5 MPa to 5 MPa, heating to 1150℃ to 1200℃ at a heating rate of 15℃ / min to 20℃ / min in a vacuum furnace, holding for 10 min to 20 min, then heating to a brazing temperature at a heating rate of 5℃ / min to 10℃ / min, holding for 10 min to 30 min, then cooling to 400℃ to 600℃ at a rate of 5℃ / min to 10℃ / min, and then cooling to room temperature in the furnace to complete brazing.

[0017] The embodiment of the present application has the following advantages:

[0018] (1) The non-equiatomic ratio TiCoCrFeNi high-entropy alloy brazing filler metal has a high mixing entropy, and the Ti element has a relatively negative binary mixing enthalpy with other metal elements, so that in the alloy structure, in addition to the FCC phase with good plasticity, there is also an IMC second phase with excellent high-temperature performance, which is a eutectic high-entropy alloy brazing filler metal with excellent plasticity and strength, compared with a single solid solution phase high-entropy alloy. After brazing, a part of the high-entropy solid solution phase is reserved in the center of the brazed joint through metallurgical reaction and element diffusion at high temperature, the high mixing entropy suppresses the generation of brittle carbides in the joint, and the mechanical properties of the joint are significantly improved.

[0019] (2) The present application can effectively control the interdiffusion of the base material and the brazing filler metal elements in the brazing process by means of the sluggish diffusion effect of the high-entropy alloy, so as to suppress the thickness of the interface reaction layer and improve the bonding strength.

[0020] (3) The high-entropy alloy brazing filler metal disclosed in the present application adds a high content of Co, Cr and other solid solution strengthening elements commonly used in nickel-based high-temperature alloys, and these elements are similar in Ni crystal structure and are easy to form a solid solution phase. At the same time, the high content of Ni elements makes the high-entropy brazing filler metal have good compatibility with nickel-based high-temperature alloys.

[0021] (4) The high-entropy alloy brazing filler metal disclosed in the present application adds an appropriate amount of Ti element as an active element, which can significantly improve the wettability of the brazing filler metal on the surface of the carbon matrix. At the brazing temperature, the molten alloy brazing filler metal penetrates into the pores of the matrix under the action of capillary force and reactive wetting, forming a mechanical locking structure, which can significantly improve the interfacial bonding strength.

[0022] (5) The high-entropy alloy filler disclosed in the application combines the high-entropy alloy theory and the design method of eutectic high-entropy alloy, and obtains a reasonable Ti-Co-Cr-Fe-Ni component ratio, so that one-time welding can be ensured, and defects such as corrosion, unmelting, micro-cracks and the like in the welding seam are avoided.

[0023] (6) The high-entropy alloy filler disclosed in the application mainly comprises an FCC phase, has good plasticity, can be processed into powder, block and various different solder forms, and can be used for assembling the solder under different welding shapes. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a schematic diagram of the base material and the solder size.

[0025] Figure 2 It is a brazing process heat cycle curve diagram.

[0026] Figure 3 It is a graphite / TiCoCrFeNi / GH4169 brazed joint interface microstructure diagram.

[0027] Figure 4 It is a C / C-GH4169 connecting piece macrograph.

[0028] Figure 5 It is a C / SiC-GH4169 connecting piece macrograph. DETAILED DESCRIPTION

[0029] The application will be further described below in combination with specific embodiments, but the application is not limited in any way by the embodiments.

[0030] The application discloses a high-entropy alloy filler for heterogenous brazing connection of high-temperature alloy and carbon material, which is composed of Ti, Co, Cr, Fe and Ni; the atomic percentage of Ti, Co, Cr, Fe and Ni is (0.6-0.65):(0.9-1.1):(0.9-1.1):(0.9-1.1):(2.0-2.1).

[0031] In a specific embodiment, the atomic percentage of Ti, Co, Cr, Fe and Ni is 0.63:1:1:1:2.1.

[0032] In a specific embodiment, Ti, Co, Cr, Fe and Ni are pure metal powders with a purity of greater than or equal to 99.5%;

[0033] In a specific embodiment, the particle size of the pure metal powder is 260-390 mesh.

[0034] The application also discloses a preparation method of the high-entropy alloy filler for heterogenous brazing connection of high-temperature alloys and carbon materials.

[0035] S1, Ti, Co, Cr, Fe and Ni are mixed according to atomic percentages of (0.6-0.65):(0.9-1.1):(0.9-1.1):(0.9-1.1):(2.0-2.1) to obtain a metal raw material.

[0036] S2, the metal raw material is subjected to high-energy ball milling by a mechanical alloying method to obtain a high-entropy alloy filler.

[0037] In a specific embodiment, the high-energy ball milling is mechanical alloying of the metal raw material by a planetary ball mill in two stages, and specifically includes the following steps:

[0038] (1) In a protective gas, the metal raw material is subjected to high-energy ball milling by a mechanical alloying method to obtain a dry-milling product.

[0039] (2) The dry-milling product is added with a liquid medium for wet milling, and vacuum drying is performed to obtain a high-entropy alloy filler.

[0040] In a specific embodiment, in step (1), the ball-to-material ratio is (10-15):1, the ball milling speed is 300 r / min-400 r / min, the ball milling time is 36 h-48 h, and the protective gas is high-purity argon.

[0041] In a specific embodiment, in step (2), the liquid medium is alcohol, the mass ratio of the liquid medium to the dry-milling product is 1-1.5:1, and the ball milling time is 10 h-20 h.

[0042] In a specific embodiment, the preparation method further includes: vacuum drying the product after wet milling at 30℃-40℃ for 12 h.

[0043] In a specific embodiment, the grinding balls used in the high-energy ball milling include grinding balls with a diameter of 8 mm-10 mm and grinding balls with a diameter of 5 mm-6 mm, and the mass ratio of the grinding balls with a diameter of 8 mm-10 mm to the grinding balls with a diameter of 5 mm-6 mm is 3.5:6.5.

[0044] In a specific embodiment, the material of the ball milling tank and the grinding balls is stainless steel.

[0045] The application also discloses a brazing method using the high-entropy alloy filler for heterogenous brazing connection of high-temperature alloys and carbon materials according to any of the embodiments or the high-entropy alloy filler for heterogenous brazing connection of high-temperature alloys and carbon materials prepared by the preparation method according to any of the embodiments, and the brazing method includes the following steps:

[0046] (1) The base material to be welded is polished and cleaned using SiC sandpaper to obtain a pretreated base material.

[0047] In a specific embodiment, step (1) specifically comprises: polishing the surface of the base material to be welded in turn using 120-mesh, 300-mesh, 600-mesh, 1200-mesh and 1500-mesh SiC sandpaper to remove surface cutting scratches, oxide films, burrs and other various defects, and placing the polished base material to be welded in anhydrous ethanol for ultrasonic oscillation cleaning for 5-15 min to remove surface grease and stains.

[0048] (2) The high-entropy alloy powder and anhydrous ethanol are mixed to obtain a paste-shaped filler metal.

[0049] (3) The paste-shaped filler metal is coated on the surface of the pretreated base material to form a welding assembly in a sandwich structure of carbon material / filler metal interlayer / high-temperature alloy.

[0050] (4) The welding assembly is placed in a graphite mold and a pressure of 0.5-5 MPa is applied, and the temperature is raised to 1150-1200°C at a heating rate of 15-20°C / min in a vacuum furnace, and then the temperature is raised to the brazing temperature at a heating rate of 5-10°C / min, and after holding for 10-30 min, the temperature is lowered to 400-600°C at a rate of 5-10°C / min, and then the furnace is cooled to room temperature, and the brazing is completed.

[0051] In a specific embodiment, in step (3), the thickness of the filler metal interlayer is 0.2-0.4 mm.

[0052] In a specific embodiment, in step (4), the vacuum degree in the vacuum furnace is kept <5x10 -3 Pa.

[0053] The following are specific embodiments

[0054] In this embodiment, pure metal powder is used as the raw material, and the high-entropy alloy powder is prepared by mechanical alloying method according to the corresponding ingredient ratio, and after the preparation of the filler metal alloy powder with qualified composition, it is used for high-temperature brazing connection of carbon materials.

[0055] Example 1

[0056] The preparation method of the high-entropy alloy filler metal in this embodiment is carried out according to the following steps:

[0057] Step 1: According to the ingredient ratio of the high-entropy alloy filler metal Ti:Co:Cr:Fe:Ni = 0.63:1:1:1:2.1, pure metal powder raw materials are weighed. Among them, the raw materials are all pure metal powder with a purity of 99.5%.

[0058] Step two: prepare high-entropy filler metal by mechanical alloying method. Put the raw materials weighed in step one into a stainless steel ball mill jar and high-energy ball mill for 48 h, then wet mill for 10 h by adding anhydrous ethanol, the ball milling speed is 350 r / min, the ball-to-material ratio is 10:1, and argon gas is filled into the ball mill jar as the protective gas during the ball milling process.

[0059] Step three: put the ball mill jar after wet milling in step two into a vacuum drying oven and vacuum dry for 12 h to obtain high-entropy filler metal powder.

[0060] Use high-entropy filler metal powder to braze graphite and GH4169 high-temperature alloy: polish the surfaces to be welded of graphite and GH4169 high-temperature alloy flat with fine sandpaper, remove surface oil stains and defects, then put the graphite and GH4169 high-temperature alloy into anhydrous ethanol and ultrasonic clean for 5 min. Weigh a small amount of high-entropy alloy powder, add an appropriate amount of anhydrous ethanol as solvent, and prepare the filler metal slurry by ultrasonic oscillation. Coat the slurry evenly on the surface of the high-temperature alloy with a thickness of about 0.2 mm. After the slurry is dried, assemble the sample in the order of graphite / high-entropy filler metal interlayer / GH4169 high-temperature alloy from top to bottom as shown in Figure 1 , and apply a pressure of 0.5-5 MPa to make the parts in contact during the connection process. Then put the sample into a vacuum furnace, first heat at a rate of 15 ℃ / min to 1150 ℃ and keep for 10 min to ensure that the temperature of each part of the connected sample is uniform. Then heat at a rate of 15 ℃ / min to the target temperature, and keep at this temperature for 10-20 min. After the holding period, cool at a rate of 5 ℃ / min to 450 ℃, and then cool to room temperature with the furnace, complete the brazing connection of graphite and GH4169 high-temperature alloy, and the heating curve is shown in Figure 2 . Keep the vacuum in the vacuum furnace (vacuum degree <5×10 -3 Pa).

[0061] The microstructure and element distribution of the graphite / TiCoCrFeNi / GH4169 high-temperature alloy brazed joint obtained in this example are shown in Figure 3 . As can be seen from the figure, the high-entropy alloy is well connected with the graphite and high-temperature alloy, and the interface layer is uniform and continuous. The energy spectrum analysis results show that Cr element is mainly concentrated on the interface on the side of graphite, which reacts with C in the graphite matrix to form an interface layer, indicating that the high-entropy alloy has good reactivity with the carbon material matrix. Ti element is slightly aggregated near the interface layer, and the unreacted high-entropy alloy layer has high and uniform distribution of Ni, Fe and Co elements, which is due to the different carbonide formation energies of different elements.

[0062] Example 2

[0063] The difference between the present embodiment and embodiment 1 is that the base material used is C / C composite material.

[0064] Figure 4 It is a macroscopic photo of the connecting piece after connection. Overall, the high-entropy alloy wets well on the surface of the C / C composite material at the brazing temperature, and the superalloy does not dissolve or deform.

[0065] Embodiment 3

[0066] The difference between the present embodiment and embodiment 1 is that the base material used is C / SiC composite material.

[0067] Figure 5 It is a macroscopic photo of the connecting piece after connection. Overall, the high-entropy alloy wets well on the surface of the C / SiC composite material at the brazing temperature, and the superalloy does not dissolve or deform.

[0068] Embodiment 4

[0069] The difference between the present embodiment and embodiment 1 is that the base material used is C / SiC composite material.

[0070] The preparation method of the high-entropy alloy filler material of the present embodiment is carried out according to the following steps:

[0071] Step one: according to the component ratio of the high-entropy alloy filler material Ti:Co:Cr:Fe:Ni = 0.65:1:1:1:2.1, the pure metal powder raw materials are weighed. Among them, the raw materials are all pure metal powder, and the purity is 99.5%.

[0072] Step two: the high-entropy filler material is prepared by mechanical alloying method. The raw materials weighed in step one are high-energy ball milled in a stainless steel ball mill jar for 48h, and then wet milled with anhydrous ethanol for 10h, the ball milling speed is 350r / min, the ball to material ratio is 10:1, and argon gas is filled in the ball mill jar as the protective gas during ball milling.

[0073] Step three: the ball mill jar after wet milling in step two is put into a vacuum drying box and vacuum dried for 12h to obtain the high-entropy filler material powder.

[0074] Brazing graphite and GH4169 high-temperature alloy with high-entropy filler powder: The surfaces of the graphite and GH4169 high-temperature alloy to be welded are polished flat with fine sandpaper to remove surface oil stains and defects, and then the graphite and GH4169 high-temperature alloy are placed in anhydrous ethanol and ultrasonically cleaned for 5 min. A small amount of high-entropy alloy powder is weighed, and an appropriate amount of anhydrous ethanol is added as a solvent to prepare a filler slurry by ultrasonic oscillation. The slurry is uniformly coated on the surface of the high-temperature alloy with a thickness of about 0.2 mm. After the slurry is dried, the components are assembled in the order of graphite / high-entropy filler middle layer / GH4169 high-temperature alloy from top to bottom, and a pressure of 0.5-5 MPa is applied to ensure that the components are in close contact during the welding process. Then the sample is placed in a vacuum furnace, first heated to 1150°C at a rate of 15°C / min and held for 10 min to ensure that the temperature of each part of the joint is uniform. Then, the temperature is raised to the target temperature at a rate of 15°C / min, and held at this temperature for 10-20 min. After the holding period, the temperature is lowered to 450°C at a rate of 5°C / min, and then the furnace is cooled to room temperature. The brazing connection of graphite and GH4169 high-temperature alloy is completed. The vacuum in the vacuum furnace is maintained (vacuum degree < 5 x 10 - 3 Pa).

[0075] In the graphite / TiCoCrFeNi / GH4169 high-temperature alloy brazed joint obtained in this example, the melting point of the filler metal is slightly increased, the fluidity of the liquid filler metal is poor, the interfacial reaction layer is thinned, and there are obvious cracks or holes in the weld.

[0076] Example 5

[0077] The difference between this example and Example 1 is that the composition ratio of the high-entropy alloy filler is Ti:Co:Cr:Fe:Ni = 0.6:0.9:0.9:0.9:2, and the pure metal powder raw materials are weighed according to the composition ratio.

[0078] The preparation method of the high-entropy alloy filler in this example is carried out according to the following steps:

[0079] Step one: The pure metal powder raw materials are weighed according to the composition ratio of the high-entropy alloy filler Ti:Co:Cr:Fe:Ni = 0.6:0.9:0.9:0.9:2. The raw materials are all pure metal powders with a purity of 99.5%.

[0080] Step two: The high-entropy filler is prepared by mechanical alloying. The raw materials weighed in step one are high-energy ball milled in a stainless steel ball mill jar for 48 h, and then anhydrous ethanol is added for wet milling for 10 h. The ball milling speed is 350 r / min, the ball-to-material ratio is 10:1, and argon gas is filled into the ball mill jar as a protective gas during the ball milling process.

[0081] Step three: Put the ball mill tank after wet grinding in step two into a vacuum drying oven and vacuum dry for 12 h to obtain the high-entropy filler metal powder.

[0082] Brazing of graphite and GH4169 superalloy using high-entropy filler metal powder: The surfaces of the graphite and GH4169 superalloy to be welded were polished flat using fine sandpaper to remove surface dirt and defects. Then the graphite and GH4169 superalloy were placed in anhydrous ethanol and ultrasonically cleaned for 5 min. A small amount of high-entropy alloy powder was weighed and added to an appropriate amount of anhydrous ethanol as a solvent, and an ultrasonic vibration was used to prepare the filler metal slurry. The slurry was uniformly coated on the surface of the superalloy with a thickness of about 0.2 mm. After the slurry was dried, the samples were assembled in the order of graphite / high-entropy filler metal interlayer / GH4169 superalloy from top to bottom, and a pressure of 0.5-5 MPa was applied to ensure that the parts were in close contact during the connection process. Then the samples were placed in a vacuum furnace, first heated to 1150℃ at a rate of 15℃ / min and held for 10 min to ensure that the temperature of each part of the connected sample was uniform. Then the temperature was raised to the target temperature at a rate of 15℃ / min, and the temperature was held for 10-20 min. After the holding period, the temperature was lowered to 450℃ at a rate of 5℃ / min, and then the furnace was cooled to room temperature. The brazing connection of graphite and GH4169 superalloy was completed. The vacuum in the vacuum furnace was maintained (vacuum degree < 5 x 10 - 3 Pa).

[0083] In the graphite / TiCoCrFeNi / GH4169 superalloy brazed joint obtained in this example, the interface reaction was not sufficient due to the low content of active metal elements in the filler metal, and the interface bonding strength was low.

[0084] Example 6

[0085] The difference between this example and Example 1 is that the composition ratio of the high-entropy alloy filler metal is Ti:Co:Cr:Fe:Ni = 0.5:1:1:1:2.1, and the pure metal powder raw materials are weighed according to the composition ratio.

[0086] The preparation method of the high-entropy alloy filler metal in this example is carried out according to the following steps:

[0087] Step one: The pure metal powder raw materials are weighed according to the composition ratio of the high-entropy alloy filler metal Ti:Co:Cr:Fe:Ni = 0.5:1:1:1:2. The raw materials are all pure metal powders with a purity of 99.5%.

[0088] Step two: The high-entropy filler metal is prepared by mechanical alloying. The raw materials weighed in step one are high-energy ball milled in a stainless steel ball mill tank for 48 h, and then wet milled with anhydrous ethanol for 10 h. The ball milling speed is 350 r / min, the ball-to-material ratio is 10:1, and argon gas is filled into the ball mill tank as a protective gas during the ball milling process.

[0089] Step three: Put the ball mill tank after wet grinding in step two into a vacuum drying oven and vacuum dry for 12 h to obtain high-entropy solder powder.

[0090] Brazing of graphite and GH4169 high-temperature alloy using high-entropy solder powder: The surfaces of the graphite and GH4169 high-temperature alloy to be welded were polished flat with fine sandpaper, and the surface oil stains and defects were removed. Then the graphite and GH4169 high-temperature alloy were placed in anhydrous ethanol and ultrasonically cleaned for 5 min. A small amount of high-entropy alloy powder was weighed and added to an appropriate amount of anhydrous ethanol as a solvent, and the solder slurry was prepared by ultrasonic oscillation. The slurry was uniformly coated on the surface of the high-temperature alloy with a thickness of about 0.2 mm. After the slurry was dried, the samples were assembled in the order of graphite / high-entropy solder interlayer / GH4169 high-temperature alloy from top to bottom, and a pressure of 0.5-5 MPa was applied to ensure that the parts were in close contact during the connection process. Then the samples were placed in a vacuum furnace, first heated to 1150℃ at a rate of 15℃ / min and held for 10 min to ensure that the temperature of each part of the connected sample was uniform. Then the temperature was raised to the target temperature at a rate of 15℃ / min, and the temperature was held for 10-20 min. After the holding period, the temperature was lowered to 450℃ at a rate of 5℃ / min, and then the furnace was cooled to room temperature. The brazing connection of graphite and GH4169 high-temperature alloy was completed. The vacuum in the vacuum furnace was maintained (vacuum degree < 5 x 10 - 3 Pa).

[0091] The alloy obtained in this example failed to form a stable solid solution structure, and a large amount of brittle intermetallic compounds were present in the joint after brazing connection.

[0092] Comparative Example 1

[0093] The difference between this comparative example and Example 1 is that the high-energy ball milling step is replaced by ordinary ball milling, and the specific steps are as follows:

[0094] Step one: The raw materials were weighed according to the composition ratio of the high-entropy alloy solder Ti:Co:Cr:Fe:Ni = 0.63:1:1:1:2.1. The raw materials were all pure metal powders with a purity of 99.5%.

[0095] Step two: The solder was prepared by mechanical alloying. The raw materials weighed in step one were ball milled in a stainless steel ball mill tank for 48 h, and then anhydrous ethanol was added for wet milling for 10 h. The ball milling speed was 200 r / min, the ball-to-material ratio was 10:1, and argon gas was filled into the ball mill tank as a protective gas during the ball milling process.

[0096] Step three: Put the ball mill tank after wet grinding in step two into a vacuum drying oven and vacuum dry for 12 h to obtain the solder powder.

[0097] The alloy powder obtained according to the ball milling process was found to be not completely alloyed by XRD analysis.

[0098] Comparative Example 2

[0099] The present comparative example is compared with Example 1, the only difference being that the present comparative example only uses wet milling. The specific steps are as follows:

[0100] Step one: according to the component ratio of high-entropy alloy solder Ti:Co:Cr:Fe:Ni = 0.63:1:1:1:2.1, pure metal powder raw materials were weighed. Among them, the raw materials are all pure metal powder with a purity of 99.5%.

[0101] Step two: the solder was prepared by mechanical alloying method. The raw materials weighed in step one were put in a stainless steel ball milling tank, and ethanol was added for ball milling for 48 h, the ball milling speed was 350 r / min, the ball to material ratio was 10:1, and argon was filled in the ball milling tank as a protective gas during the ball milling process.

[0102] Step three: the ball milling tank after step two was put into a vacuum drying box and vacuum dried for 12 h to obtain the solder powder.

[0103] The alloy powder obtained according to the ball milling process was found to be not completely alloyed by XRD analysis.

[0104] Comparative Example 3

[0105] The present comparative example is compared with Example 1, the only difference being that the present comparative example only uses dry milling. The specific steps are as follows:

[0106] Step one: according to the component ratio of high-entropy alloy solder Ti:Co:Cr:Fe:Ni = 0.63:1:1:1:2.1, pure metal powder raw materials were weighed. Among them, the raw materials are all pure metal powder with a purity of 99.5%.

[0107] Step two: the solder was prepared by mechanical alloying method. The raw materials weighed in step one were put in a stainless steel ball milling tank and ball milled for 48 h, the ball milling speed was 350 r / min, the ball to material ratio was 10:1, and argon was filled in the ball milling tank as a protective gas during the ball milling process.

[0108] After the completion of the ball milling process, most of the alloy solder was cold-welded on the milling balls and the inner wall of the tank, and the average particle size of the alloy particles was about 30-40 μm, which was much larger than the particle size of the powder obtained by the dry and wet milling mixed process (about 5 μm). XRD analysis of the alloy particles found that alloying was achieved, but obvious cracks existed in the weld after welding due to the poor flowability of the large particle solder.

[0109] Table 1 Shear strength of brazed joints of Examples 1-6 and Comparative Examples 1-3

[0110]

[0111] In summary, the composition and the addition ratio of the high-entropy alloy brazing filler metal are reasonably improved through multiple tests, and the preparation process is optimized, after brazing by the non-equiatomic ratio TiCoCrFeNi high-entropy alloy brazing filler metal of the application, part of the high-entropy solid solution phase is reserved at the center position of the brazed joint, the high mixing entropy inhibits the generation of brittle carbide in the joint, and the mechanical properties of the joint are significantly improved. With the help of the high-entropy alloy's delay diffusion effect, the interdiffusion of the base material and the brazing filler metal elements in the brazing connection process can be effectively controlled, thereby inhibiting the thickness of the interface reaction layer and improving the bonding strength.

[0112] The above-mentioned examples only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A brazing method using a high-entropy alloy filler metal for dissimilar brazing connections between high-temperature alloys and carbon materials, characterized in that, Includes the following steps: (1) The base material to be welded is polished and cleaned with SiC sandpaper to obtain the pretreated base material; (2) Mix high-entropy alloy powder and anhydrous ethanol to obtain a paste-like brazing filler metal; (3) The paste-like brazing filler metal is coated on the surface of the pretreated base material to form a welded assembly with a sandwich structure consisting of carbon material / brazing filler metal intermediate layer / high temperature alloy in sequence; (4) Place the welded assembly into a graphite mold and apply a pressure of 0.5MPa~5MPa. In a vacuum furnace, heat the assembly to 1150℃~1200℃ at a heating rate of 15℃ / min~20℃ / min, hold for 10min~20min, then heat the assembly to the brazing temperature at a heating rate of 5℃ / min~10℃ / min, hold for 10min~30min, then cool the assembly to 400℃~600℃ at a heating rate of 5℃ / min~10℃ / min, and then cool the assembly to room temperature in the furnace to complete the brazing. The high-entropy alloy brazing filler metal is composed of Ti, Co, Cr, Fe and Ni; the atomic percentages of Ti, Co, Cr, Fe and Ni are (0.6~0.65):(0.9~1.1):(0.9~1.1):(0.9~1.1):(2.0~2.1).

2. The brazing method according to claim 1, characterized in that, The atomic percentages of Ti, Co, Cr, Fe and Ni are 0.63:1:1:1:2.

1.

3. The brazing method according to claim 1, characterized in that, The Ti, Co, Cr, Fe and Ni are pure metal powders with a purity of ≥99.5%; The particle size of the pure metal powder is 260 mesh to 390 mesh.

4. The brazing method according to claim 1, characterized in that, The preparation method of the high-entropy alloy solder includes the following steps: Ti, Co, Cr, Fe and Ni are mixed in an atomic percentage ratio of (0.6~0.65):(0.9~1.1):(0.9~1.1):(0.9~1.1):(2.0~2.1) to obtain a metallic raw material; The metal raw material is subjected to high-energy ball milling using a mechanical alloying method to obtain the high-entropy alloy brazing filler metal.

5. The brazing method according to claim 4, characterized in that, The high-energy ball milling involves mechanically alloying the metal raw material in two stages using a planetary ball mill, specifically including the following steps: (1) In a protective gas environment, the metal raw material is subjected to high-energy ball milling using a mechanical alloying method to obtain a dry-milled product; (2) Add liquid medium to the dry grinding product for wet grinding and vacuum drying to obtain the high entropy alloy brazing filler metal.

6. The brazing method according to claim 5, characterized in that, In step (1), the ball-to-material ratio is (10~15):1; the ball milling speed is 300r / min~400r / min; the ball milling time is 36h~48h; and the protective gas is high-purity argon. In step (2), the liquid medium is alcohol; the mass ratio of the liquid medium to the dry-milled product is 1~1.5:1, and the ball milling time is 10h~20h.

7. The brazing method according to claim 4, characterized in that, The grinding balls used in the high-energy ball mill include grinding balls with a diameter of 8mm to 10mm and grinding balls with a diameter of 5mm to 6mm; The mass ratio of the grinding balls with a diameter of 8mm to 10mm to the grinding balls with a diameter of 5mm to 6mm is 3.5:6.5; The grinding ball is made of stainless steel.

8. The brazing method according to claim 1, characterized in that, In step (3), the thickness of the brazing filler intermediate layer is 0.2mm~0.4mm.

9. The brazing method according to claim 1, characterized in that, In step (4), the vacuum level inside the vacuum furnace is maintained at <5×10⁻⁶. -3 Pa.

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