High entropy carbide ceramic diffusion bonding method of high-nb content alloyed interlayer

Abstract

This invention discloses a diffusion bonding method for high-entropy carbide ceramics with a high Nb content alloyed interlayer. The method involves stacking Ni foil-Nb foil-Ni foil sequentially to form a composite interlayer, where the Nb atom content is 65-85 at.%. The composite interlayer is placed between the welding surfaces of two high-entropy carbide ceramic blocks, and pre-pressure and diffusion bonding pressure are applied simultaneously to diffusely bond the two blocks. The bonding is then maintained at a diffusion bonding temperature of 1200-1250°C for 30-90 minutes to form a high-entropy carbide ceramic joint. A high-Nb content transition layer is formed by in-situ alloying the Nb layer with a small amount of Ni atoms. This high-Nb content transition layer contacts the high-entropy carbide ceramic and bonds at the interface through atomic diffusion. This effectively reduces the diffusion bonding temperature between the refractory metal interlayer and the high-entropy carbide ceramic. The resulting joint exhibits good mechanical properties at both room temperature and high temperature and maintains interface structural stability under extreme corrosive environments.

Description

Technical Field

[0001] This invention belongs to the field of high-entropy carbide ceramic diffusion welding technology, and in particular relates to a high-entropy carbide ceramic diffusion bonding method for alloyed intermediate layers with high Nb content. Background Technology

[0002] High-entropy ceramics are single-phase solid solutions with a system mixing entropy greater than 1.5R (where R is the gas constant). They are generally composed of four or more metallic elements and one or two non-metallic elements, exhibiting thermodynamic high-entropy effects, structural lattice distortion effects, kinetic hysteresis diffusion effects, and performance cocktail effects. High-entropy carbide ceramics (HECs) are a typical class of high-entropy ceramic structural materials. They not only retain the advantages of traditional single-carbide ceramics, such as high melting point, high hardness, and good corrosion resistance, but also exhibit higher flexural strength and superior high-temperature stability, showing great application potential in engine combustion chamber components and thermal protection structures in the aerospace field. In addition, the multi-component nature leads to high vacancy migration potential and strong local lattice distortion, giving HECs outstanding radiation resistance, thus extending their potential applications to the nuclear industry, such as fourth-generation nuclear reactors. Currently, HECs prepared solely by various sintering methods cannot meet the requirements for forming large-size and complex-shaped components, necessitating reliable joining technologies for HECs to achieve further engineering applications.

[0003] In order to prepare HECs joints with both excellent high-temperature mechanical properties and good corrosion resistance, the design of a suitable diffusion-bonded interlayer and high-temperature vacuum diffusion welding is an effective way to prepare HECs joints. At present, there are very limited reports on the process of preparing HECs diffusion-bonded joints. Among them, Ni interlayer has been proven to be able to be used for diffusion bonding of (HfZrTiTaNb)C ceramics[1], but the corrosion resistance of pure metal Ni is poor, and the joints made cannot be used in corrosive environments. Refractory metal Nb as an interlayer can make ceramic joints have excellent high-temperature resistance and corrosion resistance, but Nb has a high melting point and a large atomic radius. The process temperature for diffusion bonding with ceramics is high, and it is often necessary to form a heterogeneous interface between Nb interlayer and traditional ceramics by direct high-temperature sintering[2]. The retarded diffusion effect of high-entropy ceramics makes it more difficult to achieve bonding with Nb through interface diffusion. In traditional ceramic homogeneous joints or heterogeneous joints with metals having Nb interlayers, the connection between the Nb interlayer and the ceramic depends on a pre-placed metal layer (Ni, Cu, etc.) or a low-melting-point solder. For example, the invention patent with application date of April 22, 2013 and authorization announcement number CN 103214260B uses an Nb / Ni interlayer to prepare a DD3 high-temperature alloy Ti3AlC2 ceramic joint for aerospace components by high-temperature heating. The connection of the joint depends on the structure of Nb layer / Ni layer / Ti3AlC2 ceramic. Single carbides (HfC, TaC and ZrC) achieve instantaneous liquid phase connection through Ni / Nb / Ni composite interlayer at process parameters of 1400℃ / 30min [3]. However, in the above joints, the presence of residual Ni layer makes the joint corrosion resistance extremely poor, and the presence of complex intermetallic compounds easily causes interface failure of the joint during high-temperature service.

[0004] In addition, the eutectic liquid phase formed by Nb and Ni is often used for brazing various metals or alloys. For example, the invention application with the application date of 2021.10.09 and publication number CN 115533237A discloses a brazing process for HECs based on Nb and Ni. Both TiNi-Nb eutectic brazing filler metal[4] and high-entropy alloy brazing filler metal[5] can be used to obtain joints with excellent mechanical and high-temperature properties. However, the microstructure of the joint interface of HECs is formed by the solid-liquid interface reaction between high-entropy carbide ceramics and liquid brazing filler metal, which solidifies after cooling. In this process, the complex metal compound interface formed in the joint is easily corroded and destroyed due to the large potential difference. The ceramic matrix inevitably dissolves along the grain boundaries. The increase in the number of heterogeneous interfaces will also significantly reduce the corrosion resistance of the joint.

[0005] In summary, based on the corrosion resistance and mechanical properties of HECs joints, this invention proposes a high-entropy carbide ceramic diffusion bonding method with a high-Nb content alloyed intermediate layer. A small amount of Ni is introduced to alloy the Nb layer, forming a high-Nb content transition layer in situ. This transition layer retains the characteristics of refractory metal Nb and can achieve high-quality diffusion bonding with HECs at lower temperatures, thus improving the corrosion resistance of the joint while ensuring its excellent mechanical properties.

[0006] The sources for each document in the background section are as follows:

[0007] [1]Mu RJ, Yang ZW, Niu SY, Sun KB, Wang Y., Wang DP, Diffusionbonding of (Hf 0.2 Zr 0.2 Ti 0.2 Ta 0.2 Nb 0.2 )C high-entropy ceramic with metallic Ni foil[J].Journal of European Ceramic Society.2021,41(15):7478-7487.

[0008] [2]Bai YH, Sun MY, Cheng LF, Fan SW, Developing high toughnesslaminated HfB2-SiC ceramics with ductile Nb interlayer[J].CeramicsInternational.2019,45:20977-20982.

[0009] [3]Silvestroni L.,Sciti D.,Esposito L.,Glaeser AM,Joining of ultra-refractory carbides[J].Journal of European Ceramic Society.2012,32(16):4469-4479.

[0010] [4]Sun KB, Yang ZW, Mu RJ, Niu SY, Wang Y., Wang DP, High-temperature stability of microstructure and mechanical properties of eutectic-reinforced high-entropy ceramic joint[J]. Journal of European CeramicSociety.2022,42(11):4436-4445.

[0011] [5]Mu RJ, Wang Y., Niu SY, Sun KB, Yang ZW, Enhanced interfacialstructure of (HfZrTiTaNb)C high-entropy ceramic joint brazed usingFeCoCrNiTi 0.2 alloy filler[J].Journal of Materials Processing Technology.2024,97:118253. Summary of the Invention

[0012] To address the shortcomings of existing technologies, the technical problem this invention aims to solve is to provide a high-entropy carbide ceramic diffusion bonding method for alloyed intermediate layers with high Nb content.

[0013] The technical solution adopted by the present invention to solve the aforementioned technical problem is as follows:

[0014] A method for high-entropy carbide ceramic diffusion bonding of a high-Nb content alloyed interlayer, characterized in that the method includes the following steps:

[0015] Step 1: Grind the surfaces of the two high-entropy carbide ceramic blocks to be welded until smooth, and at the same time grind the Ni foil and Nb foil on both sides until the metal luster is exposed; put the ground Ni foil, Nb foil and high-entropy carbide ceramic blocks into acetone for ultrasonic cleaning.

[0016] Step 2: Stack Ni foil-Nb foil-Ni foil in sequence to form a composite intermediate layer, with Nb atoms accounting for 65-85 at.% in the composite intermediate layer; place the composite intermediate layer between the welding surfaces of two high-entropy carbide ceramic blocks to form an assembly joint; apply pre-pressure to the assembly joint to form a diffusion-connected assembly; place the diffusion-connected assembly in a high-temperature vacuum diffusion furnace and apply diffusion-connected pressure coaxial with the pre-pressure to the diffusion-connected assembly;

[0017] Step 3: Wait for the vacuum level inside the high-temperature vacuum diffusion furnace to drop to 1.3 × 10⁻⁶. -3 When the temperature is below Pa, the high-temperature vacuum diffusion furnace is heated to 800℃ at a heating rate of 10℃ / min and held for 20min. Then, the temperature is further increased to a diffusion bonding temperature of 1200-1250℃ at a heating rate of 10℃ / min. Ni and Nb in the composite intermediate layer undergo a eutectic reaction to produce a eutectic liquid phase. Under the action of diffusion bonding pressure, some of the eutectic liquid phase is squeezed out, and the unsqueezed Ni atoms diffuse fully into the Nb layer, causing some or all of the Nb layer to undergo in-situ alloying to form a transition layer with high Nb content. The high Nb content transition layer and the high-entropy carbide ceramic block are fully diffused at the interface to form a metallurgical connection, forming a high-entropy carbide ceramic joint.

[0018] Step 4: After the heat preservation is completed, the temperature of the high-temperature vacuum diffusion furnace is reduced to 400℃ at a cooling rate of 5℃ / min and the diffusion connection pressure is removed. The high-entropy carbide ceramic joint is allowed to cool naturally to room temperature with the furnace, thus completing the diffusion connection of the high-entropy carbide ceramic.

[0019] Furthermore, the diffusion connection pressure is 10–20 MPa.

[0020] Furthermore, at the diffusion bonding temperature, the vacuum level inside the high-temperature vacuum diffusion furnace does not exceed 5.5 × 10⁻⁶. -3 Pa.

[0021] Furthermore, the Ni foil has a thickness of 5–10 μm, and the Nb foil has a thickness of 60–100 μm.

[0022] Furthermore, the high-entropy carbide ceramic bulk can be made of high-entropy carbide ceramics such as (HfZrTiTaNb)C or (WMoVNbTa)C.

[0023] Furthermore, the density of the high-entropy carbide ceramic bulk is above 99%, and it contains equimolar or near-equimolar amounts of transition metal elements, including four or six of the following: hafnium, zirconium, titanium, tantalum, niobium, vanadium, molybdenum, tungsten, and chromium.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. This invention proposes a diffusion bonding method for high-entropy carbide ceramics with a high Nb content alloyed interlayer, targeting the high-temperature service environment and extreme corrosion environment of high-entropy carbide ceramic materials. This method is implemented at a diffusion bonding temperature of 1200-1250℃, which effectively reduces the diffusion bonding temperature between the refractory metal interlayer and the high-entropy carbide ceramic. At the same time, the joint exhibits good mechanical properties at both room temperature and high temperature of 600℃, and maintains the stability of the interface structure under extreme corrosion environment.

[0026] 2. This method utilizes a small amount of Ni atoms to in-situ alloy the Nb layer, forming a high-Nb-content transition layer for diffusion bonding in high-entropy carbide ceramics. Specifically, during heating, Ni and Nb undergo a eutectic reaction at approximately 1175°C to form a Ni-Nb eutectic liquid phase. This eutectic liquid phase is squeezed out of the joint gap under diffusion bonding pressure, without participating in the formation of the joint interface structure. This promotes the rapid and sufficient diffusion of unextruded Ni atoms into the Nb layer, causing in-situ alloying of part or all of the Nb layer near the ceramic side, transforming it into a high-Nb-content transition layer. This solves the problem of traditional metallurgical methods struggling to alloy refractory metal Nb and prepare alloyed intermediate layers. The alloyed intermediate layer process is simple, the alloying composition is largely controllable, and it is convenient for transfer to the design and diffusion bonding of other refractory metal intermediate layers, such as Ta alloyed intermediate layers.

[0027] 3. In this method, the interfacial metallurgical bonding of the high-entropy carbide ceramic joint is achieved through atomic interdiffusion between the high-Nb content transition layer and the high-entropy carbide ceramic. This transition layer inherits the mechanical properties and corrosion resistance advantages of the refractory metal Nb intermediate layer. Moreover, there are no residual Ni layers, complex Ni-Nb metal compounds, or binary Nb carbides in the welded joint. The shear strength of the joint at 600℃ is higher than 140MPa. After 10 days of corrosion in simulated nuclear industry reprocessing liquid (hot nitric acid solution containing strong oxidizing ions), the interfacial structure and chemical composition remain unchanged. This method is suitable for the actual production of high-entropy carbide ceramic components under high temperature and extreme corrosion conditions. Attached Figure Description

[0028] Figure 1 The graph shows the temperature and pressure changes over time in the high-temperature vacuum diffusion furnace during the diffusion bonding process.

[0029] Figure 2 This is a scanning electron microscope image of the interface of the high-entropy carbide ceramic joint prepared in Example 1;

[0030] Figure 3 The elemental distribution diagram of the interface of the high-entropy carbide ceramic joint prepared in Example 1 is shown.

[0031] Figure 4 Transmission electron microscopy image of the interface of the high-entropy carbide ceramic joint prepared in Example 1;

[0032] Figure 5 Selected area electron diffraction pattern of the Nb2Ni phase at the interface of the high-entropy carbide ceramic joint prepared in Example 1;

[0033] Figure 6 This is a comparison of the shear strength of the high-entropy carbide ceramic joint prepared in Example 1 at room temperature and high temperature.

[0034] Figure 7 This is a scanning electron microscope image of the interface of the high-entropy carbide ceramic joint prepared in Example 1 after etching.

[0035] Figure 8 This is a scanning electron microscope image of the interface of the high-entropy carbide ceramic joint prepared in Example 2;

[0036] Figure 9 The image shows a scanning electron microscope (SEM) image of the interface of the high-entropy carbide ceramic joint prepared in Comparative Example 1. Detailed Implementation

[0037] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but this is not intended to limit the scope of protection of this application.

[0038] This invention relates to a method for diffusion bonding of high-entropy carbide ceramics in a high-Nb content alloyed interlayer (hereinafter referred to as the method), comprising the following steps:

[0039] Step 1: Grind the surfaces of the two high-entropy carbide ceramic blocks to be welded using a #3000 diamond abrasive pad to ensure that the upper and lower surfaces of the high-entropy carbide ceramic blocks are parallel; Grind two Ni foils with a thickness of 5-10 μm and one Nb foil with a thickness of 60-100 μm on both sides with #2000 sandpaper until a metallic luster is exposed; Place the ground Ni foil, Nb foil and high-entropy carbide ceramic blocks in acetone and ultrasonically clean for 10-20 minutes to remove surface contaminants;

[0040] The purity of both the Ni foil and Nb foil is greater than 99.6%. The Ni foil and Nb foil have the same area, which is larger than the area of ​​the high-entropy carbide ceramic block to be welded. After polishing, the Ni foil and Nb foil should be kept flat, without waves or creases.

[0041] Step 2: Stack Ni foil-Nb foil-Ni foil in sequence to form a composite intermediate layer, with Nb atoms accounting for 65-85 at.% in the composite intermediate layer; place the composite intermediate layer between the solderable surfaces of two high-entropy carbide ceramic blocks to form an assembly joint; place the assembly joint between two graphite disks, the weight of the graphite disks can apply a pre-pressure of about 0.01 MPa to the assembly joint to form a diffusion connection assembly; place the diffusion connection assembly on a horizontal sample stage in a high-temperature vacuum diffusion furnace, and apply a diffusion connection pressure coaxial with the pre-pressure through a pressure head that can move up and down in the high-temperature vacuum diffusion furnace, the diffusion connection pressure being 10-20 MPa, so that the solderable surfaces of the high-entropy carbide ceramic blocks are in close contact with the composite intermediate layer;

[0042] Step 3: Wait for the vacuum level inside the high-temperature vacuum diffusion furnace to drop to 1.3 × 10⁻⁶. -3 When the pressure is below Pa, the high-temperature vacuum diffusion furnace is heated to 800℃ at a heating rate of 10℃ / min and held for 20min. Then, the temperature is further increased to the diffusion bonding temperature of 1200-1250℃ at a heating rate of 10℃ / min. At the diffusion bonding temperature, the vacuum degree inside the high-temperature vacuum diffusion furnace does not exceed 5.5×10⁻⁶. -3 Pa; Ni and Nb in the composite intermediate layer undergo a eutectic reaction at approximately 1175 °C to produce Ni 59.5 Nb 40.5 The eutectic liquid phase, part of which is squeezed out of the joint gap under the diffusion bonding pressure, causes the Ni layer in the composite intermediate layer to be completely consumed. The unsqueezed Ni atoms diffuse rapidly and fully into the high-melting-point Nb layer, causing part (or all) of the Nb layer to undergo in-situ alloying, forming a high-Nb content transition layer. The high-Nb content transition layer and the remaining Nb layer constitute the alloyed intermediate layer. After holding at the diffusion bonding temperature for 30-90 minutes, the high-Nb content transition layer and the two high-entropy carbide ceramic blocks are metallurgically connected at the interface through full diffusion, forming a high-entropy carbide ceramic joint.

[0043] The high-Nb content transition layer is mainly formed by in-situ alloying of the Nb2Ni phase. With the assistance of the eutectic liquid phase, the unextruded Ni atoms rapidly diffuse into the high-melting-point Nb layer. In the Nb layer, the part of the Nb layer near the Ni side undergoes in-situ alloying and transforms into a high-Nb content transition layer, while the central position far from Ni retains the original pure metallic Nb layer. The high-Nb content transition layer contacts the high-entropy carbide ceramic and achieves connection at the interface through atomic diffusion. This can effectively reduce the diffusion connection temperature between the high-melting-point metallic Nb and the ceramic, and solve the problem that the Ni-Nb alloy always preferentially precipitates primary Ni3Nb and eutectic structure during brazing, and the difficulty of preparing a high-Nb content alloyed intermediate layer by traditional smelting methods.

[0044] Step 4: After the heat preservation is completed, the temperature of the high-temperature vacuum diffusion furnace is reduced to 400℃ at a cooling rate of 5℃ / min and the diffusion connection pressure is removed. Finally, the high-entropy carbide ceramic joint is allowed to cool naturally to room temperature with the furnace, thus completing the diffusion connection of the high-entropy carbide ceramic. The high-entropy carbide ceramic joint maintains a good vacuum degree throughout the cooling process in the furnace.

[0045] The high-entropy carbide ceramic joints obtained above exhibit good interfacial bonding, free from defects such as cracks and pores. The typical interfacial microstructure, from left to right, consists of high-entropy carbide ceramic, a transition layer, an Nb layer, another transition layer, and another high-entropy carbide ceramic. The interface does not contain residual pure metallic Ni, complex Ni-Nb intermetallic compounds, or binary Nb carbides. The high-entropy carbide ceramic joints demonstrate excellent mechanical and corrosion resistance properties. Their high-temperature (600℃) shear strength exceeds 140 MPa. After 10 days of corrosion in simulated nuclear industry reprocessing solutions (hot nitric acid solution containing strong oxidizing ions), the interfacial structure and chemical composition of the high-entropy carbide ceramic joints remain unchanged. Therefore, this method is suitable for the preparation of high-entropy carbide ceramic components under high-temperature and extreme corrosion conditions.

[0046] The density of the high-entropy carbide ceramic bulk is above 99%, and it can be high-entropy carbide ceramics such as (HfZrTiTaNb)C and (WMoVNbTa)C. The high-entropy carbide ceramic contains equimolar or near equimolar transition metal elements, including four or six of the following: hafnium, zirconium, titanium, tantalum, niobium, vanadium, molybdenum, tungsten, and chromium.

[0047] Example 1

[0048] This embodiment uses (HfZrTiTaNb)C high-entropy carbide ceramic as an example to illustrate the diffusion bonding method of high-entropy carbide ceramic with high Nb content alloyed interlayer, including the following steps:

[0049] Step 1: The hot-pressed sintered (HfZrTiTaNb)C high-entropy carbide ceramics are processed into 10×10×5mm pieces using an EDM (Electrical Discharge Machining) wire cutting machine. 3 and 5×5×5mm 3 The two blocks have a welding surface area of ​​5×5mm. 2The surfaces of the two high-entropy carbide ceramic blocks to be welded were polished smooth using 1000# and 3000# diamond grinding discs, ensuring that the upper and lower surfaces of the high-entropy carbide ceramic blocks were parallel. Two 10μm thick Ni foils and one 60μm thick Nb foil were polished on both sides with #2000 sandpaper until a metallic luster was exposed. At this point, the proportion of Nb atoms in the composite intermediate layer was approximately 65 at.%. The polished Ni foil and Nb foil maintained a smooth surface without waves or creases. The polished Ni foil, Nb foil and high-entropy carbide ceramic blocks were then ultrasonically cleaned in acetone for 10-20 minutes to remove surface contaminants.

[0050] Step 2: Stack Ni foil-Nb foil-Ni foil in sequence to form a composite intermediate layer. Cut the composite intermediate layer into a near square with a side length of 6mm and place it between the solderable surfaces of the two high-entropy carbide ceramic blocks to form an assembly joint. Place the assembly joint between two graphite disks. The weight of the graphite disks can apply a pre-pressure of about 0.01MPa to the assembly joint to form a diffusion connection assembly. Place the diffusion connection assembly on the sample stage of the high-temperature vacuum diffusion furnace. Apply a diffusion connection pressure of 10MPa to the diffusion connection assembly through a pressure head that can move up and down in the furnace. The diffusion connection pressure and the pre-pressure are coaxial, so that the solderable surfaces of the high-entropy carbide ceramic blocks are in close contact with the composite intermediate layer.

[0051] Step 3: Wait for the vacuum level inside the high-temperature vacuum diffusion furnace to decrease to 1.3 × 10⁻⁶. -3 When the pressure is below Pa, start the heating program and heat the high-temperature vacuum diffusion furnace to 800℃ at a heating rate of 10℃ / min. Hold at this temperature for 20 minutes, then continue heating the high-temperature vacuum diffusion furnace to the diffusion bonding temperature of 1200℃ at a heating rate of 10℃ / min. At the diffusion bonding temperature, the vacuum degree inside the high-temperature vacuum diffusion furnace shall not exceed 5.5 × 10⁻⁶. -3 Pa; Ni and Nb in the composite intermediate layer undergo a eutectic reaction at approximately 1175℃ to produce some Ni. 59.5 Nb 40.5 The eutectic liquid phase, partially squeezed out of the joint gap under diffusion bonding pressure, causes the Ni layer in the composite intermediate layer to be completely consumed. The unsqueezed Ni atoms diffuse rapidly and fully into the high-melting-point Nb layer, causing in-situ alloying of part of the Nb layer, forming a high-Nb content transition layer mainly composed of Nb2Ni phase. At the same time, the presence of the eutectic liquid phase improves the interfacial contact between the Nb2Ni layer and the high-entropy carbide ceramic. After holding at the diffusion bonding temperature for 60 min, Nb2Ni and the high-entropy carbide ceramic form a good metallurgical bond through sufficient interdiffusion, forming a high-entropy carbide ceramic joint with an alloyed intermediate layer of high Nb content.

[0052] Step 4: After the heat preservation is completed, the temperature inside the high-temperature vacuum diffusion furnace is reduced to 400℃ at a cooling rate of 5℃ / min, and the diffusion connection pressure is removed. Finally, the high-entropy carbide ceramic joint is allowed to cool naturally to room temperature with the furnace, thus completing the diffusion connection of the high-entropy carbide ceramic.

[0053] Figure 1 The curves show the temperature and pressure changes over time in the high-temperature vacuum diffusion furnace during the diffusion bonding process.

[0054] Figure 2 The image shows a scanning electron microscope (SEM) image of the high-entropy carbide ceramic joint interface prepared in this embodiment under backscattered electron mode. As can be seen from the image, the interface of the high-entropy carbide ceramic joint is well bonded and has no obvious defects. The high-entropy carbide ceramic joint has a symmetrical interface structure, consisting of high-entropy carbide ceramic, transition layer, Nb layer, transition layer and high-entropy carbide ceramic from left to right. There are no residual pure metallic Ni, complex Ni-Nb intermetallic compounds or binary Nb carbides at the interface.

[0055] Figure 3 This is an elemental distribution diagram of the interface of a high-entropy carbide ceramic joint. From the diagram, it can be observed that the high-Nb content alloyed intermediate layer includes a high-Nb content transition layer and a central Nb layer. There are slight chemical composition fluctuations in the transition layer, mainly consisting of the Nb2Ni phase. The ratio of Nb atoms to Ni atoms in the Nb2Ni phase is close to 2:1. Nb2Ni and the high-entropy carbide ceramic are connected at the interface and there is a significant elemental concentration gradient, confirming the interdiffusion of various metal atoms at the interface.

[0056] Figure 4 This is a transmission electron microscope (TEM) image of the interface between the high-entropy carbide ceramic joint, which confirms the good bonding between the high-entropy carbide ceramic and the Nb2Ni interface at the nanoscale.

[0057] Figure 5 This is a selected area electron diffraction pattern of the Nb₂Ni phase at the interface of a high-entropy carbide ceramic joint. As can be seen from the pattern, the diffraction spots are neatly arranged. Comparison with standard diffraction patterns shows that the Nb₂Ni at the high-entropy carbide ceramic joint interface conforms to PDF#21-0587. The lattice parameter 'a' calculated from the interplanar spacing is... The crystal structure is consistent with the novel Nb2Ni compound discovered by Zhao JF et al. in a binary alloy system in 2022 [Journal of Materials Science & Technology, 2022, 100: 246-253].

[0058] Figure 6This is a comparison chart of the shear strength of high-entropy carbide ceramic joints at room temperature and high temperature. The shear strength test method refers to the "Test Method for Strength of Brazed Joints", standard number: GB / T 11363-2008, and the testing equipment is an MTS Model E45.106 electronic universal testing machine. For the high-temperature shear strength test, the insulation chamber is first heated to 400℃. The high-entropy carbide ceramic joint and the shear clamp are placed between the upper and lower pressure heads in the insulation chamber, and a preload of 4MPa pressure is applied. The temperature of the insulation chamber is increased to 600℃ at a rate of 10℃ / min and held for 10min. The high-entropy carbide ceramic joint is then loaded at a rate of 0.2mm / min until the joint fails. The shear strength of high-entropy carbide ceramic joints is calculated by the maximum force and connection area that cause joint failure. High-entropy carbide ceramic joints obtained when the diffusion bonding process is 1200℃ / 60min / 10MPa have a high room temperature shear strength of 133MPa and a shear strength of 142MPa at high temperature (600℃). The slight increase in shear strength at high temperature (600℃) compared to the room temperature shear strength is due to the release of residual stress in the joint caused by the test temperature being closer to the diffusion bonding temperature.

[0059] Figure 7 This is a scanning electron microscope (SEM) image of the high-entropy carbide ceramic joint interface after etching in backscattered electron mode. The joint interface was polished with a #3000 diamond grinding wheel and #7000 sandpaper, and then immersed in a simulated nuclear industry reprocessing solution (containing Ru). 3 + Ce 3+ F - After being corroded in a hot nitric acid solution with strong oxidizing ions for 10 days, the joint interface showed no cracks, no obvious corrosion marks, and no change in microstructure. Therefore, the high-entropy carbide ceramic joint prepared in this embodiment has the potential to be used in extreme corrosive environments.

[0060] Example 2

[0061] The difference between this embodiment and Embodiment 1 is that the diffusion connection temperature in step 3 is 1250℃ and the temperature is maintained for 60 minutes. Figure 8 This is a scanning electron microscope (SEM) image of the high-entropy carbide ceramic joint interface obtained in this embodiment under backscattered electron mode. The image shows that the high-entropy carbide ceramic joint is free of defects such as cracks and pores. The high-entropy carbide ceramic joint consists of high-entropy carbide ceramic and an Nb₂Ni interlayer. At the diffusion bonding temperature of 1250℃, the interdiffusion of Ni atoms into the Nb layer intensifies, and the Nb interlayer is completely transformed into a high-Nb content transition layer during in-situ alloying. The high-entropy carbide ceramic joint obtained in this embodiment has a shear strength of 171 MPa at room temperature.

[0062] Example 3

[0063] The difference between this embodiment and Embodiment 1 is that the thickness of the Ni foil in step 1 is 5 μm, and the thickness of the Nb foil is 100 μm. At this time, the proportion of Nb atoms in the composite intermediate layer is approximately 85 at.%. The high-entropy carbide ceramic joint interface obtained in this embodiment is free of defects such as cracks and pores. The high-entropy carbide ceramic joint interface consists of high-entropy carbide ceramic, a transition layer, and an Nb intermediate layer.

[0064] Comparative Example 1

[0065] The difference between this embodiment and Embodiment 1 is that in step 1, the thickness of the Ni foil is 20 μm and the thickness of the Nb foil is 60 μm, at which point the proportion of Nb atoms in the composite interlayer is approximately 45 at.%. Figure 9 As shown, the high-entropy carbide ceramic joint interface obtained in this comparative example has no defects such as cracks or pores. Due to the introduction of excessive Ni, the high-Nb content transition layer in the high-entropy carbide ceramic joint interface is dissolved, and granular Nb2Ni phase is observed at the center of the interface. A large number of complex Ni-Nb compounds (including Ni3Nb, NiNb and Nb2Ni phase) are generated at the joint interface.

[0066] Any aspects not described in this invention are applicable to the prior art.

Claims

1. A method for high-entropy carbide ceramic diffusion bonding of a high-Nb content alloyed interlayer, characterized in that, The method includes the following steps: Step 1: Grind the surfaces of the two high-entropy carbide ceramic blocks to be welded until smooth, and at the same time grind the Ni foil and Nb foil on both sides until the metal luster is exposed; put the ground Ni foil, Nb foil and high-entropy carbide ceramic blocks into acetone for ultrasonic cleaning. Step 2: Stack Ni foil-Nb foil-Ni foil in sequence to form a composite intermediate layer. The proportion of Nb atoms in the composite intermediate layer is 65-85 at.%. Place the composite intermediate layer between the two high-entropy carbide ceramic blocks to be welded to form an assembly joint. Apply pre-pressure to the assembly joint to form a diffusion connection assembly; place the diffusion connection assembly in a high-temperature vacuum diffusion furnace and apply a diffusion connection pressure coaxial with the pre-pressure to the diffusion connection assembly; Step 3: Wait for the vacuum level inside the high-temperature vacuum diffusion furnace to drop to 1.3 × 10⁻⁶. -3 When the temperature is below Pa, the high-temperature vacuum diffusion furnace is heated to 800℃ at a heating rate of 10℃ / min and held for 20min. Then, the temperature is further increased to the diffusion connection temperature of 1200~1250℃ at a heating rate of 10℃ / min. Ni and Nb in the composite intermediate layer undergo a eutectic reaction to generate a eutectic liquid phase. Under the action of diffusion connection pressure, part of the eutectic liquid phase is squeezed out, and the unsqueezed Ni atoms diffuse fully into the Nb layer, so that part or all of the Nb layer undergoes in-situ alloying to form a transition layer with high Nb content. After holding at the diffusion bonding temperature for 30–90 min, the high Nb content transition layer and the high entropy carbide ceramic block are metallurgically bonded at the interface through sufficient diffusion, forming a high entropy carbide ceramic joint. Step 4: After the heat preservation is completed, the temperature of the high-temperature vacuum diffusion furnace is reduced to 400℃ at a cooling rate of 5℃ / min and the diffusion connection pressure is removed. The high-entropy carbide ceramic joint is allowed to cool naturally to room temperature with the furnace, thus completing the diffusion connection of the high-entropy carbide ceramic.

2. The high-entropy carbide ceramic diffusion bonding method of a high-Nb-content alloyed interlayer according to claim 1, characterized in that, The diffusion connection pressure is 10-20 MPa.

3. The high-entropy carbide ceramic diffusion bonding method of a high-Nb-content alloyed interlayer according to claim 1 or 2, characterized in that, At the diffusion bonding temperature, the vacuum level inside the high-temperature vacuum diffusion furnace does not exceed 5.5 × 10⁻⁶. -3 Pa.

4. The high-entropy carbide ceramic diffusion bonding method for high-Nb content alloyed intermediate layers according to claim 1, characterized in that, The thickness of the Ni foil is 5–10 μm, and the thickness of the Nb foil is 60–100 μm.

5. The high-entropy carbide ceramic diffusion bonding method for high-Nb content alloyed intermediate layers according to claim 1 or 4, characterized in that, The high-entropy carbide ceramic bulk has a density of over 99% and contains equimolar or near-equimolar amounts of transition metal elements, including four or six of the following: hafnium, zirconium, titanium, tantalum, niobium, vanadium, molybdenum, tungsten, and chromium.

6. The high-entropy carbide ceramic diffusion bonding method of a high-Nb-content alloyed interlayer according to claim 5, characterized in that, The high-entropy carbide ceramic bulk material is (HfZrTiTaNb)C or (WMoVNbTa)C high-entropy carbide ceramic.

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