Nickel-based alloy welding structure of 650 DEG C supercritical diffuser and preparation method of nickel-based alloy welding structure

Abstract

The invention belongs to the technical field of high-temperature alloy connection, and provides a 650 DEG C supercritical diffuser nickel base alloy welding structure and a preparation method thereof. According to the method, an amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil (the thickness is 20-60 microns, and the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil comprises 5-25 wt% of Cr, 0-30 wt% of Fe, 1-8 wt% of Si, 0.5-4 wt% of B and 45-75 wt% of Ni) is placed on a butt joint interface of two nickel-based alloy components, and a welding joint area is formed through instantaneous liquid phase diffusion welding (the temperature is 1000-1150 DEG C, the pressure is 2-20 MPa, and heat preservation is conducted for 1-10 h). The ultra-low leakage airtight sealing performance that the equivalent welding layer thickness is 0.05-0.50 mm and the leakage rate reaches 1 * 10 <-1 > * 10 Pa.m / s is realized; the problems that according to a traditional welding method, the requirements for high-temperature strength, creep fatigue reliability and ultralow leakage rate airtight under the 650 DEG C supercritical working condition are difficult to meet at the same time, the contradiction between a manufacturing end low-temperature short-time wide process window and the service end long-term structure interface stability is caused, and interface wetting filling and brittle phase control are difficult to collaboratively optimize are solved.

Description

Technical Field

[0001] This invention relates to the field of high-temperature alloy joining technology, specifically to a nickel-based alloy welding structure for a 650℃ supercritical diffuser and its preparation method. Background Technology

[0002] Supercritical CO2 (S-CO2) Brayton cycle power generation technology has become a core candidate technology route for fourth-generation nuclear energy, fusion energy, and advanced thermal power generation systems due to its high efficiency, compactness, and environmental friendliness. In the S-CO2 cycle system, the diffuser, as a critical flow channel conversion component, must withstand temperatures above 650°C, pressures of 20-30 MPa, and the highly corrosive environment of supercritical CO2 fluid, while also meeting extremely stringent requirements for airtightness (leakage rate must reach 10⁻⁻⁻⁶). 9 To ensure system thermal efficiency and operational safety, nickel-based superalloys (such as GH4169 and Inconel 718) are the preferred materials for diffuser manufacturing due to their excellent high-temperature strength, creep resistance, and oxidation corrosion resistance. However, the complex geometry of diffusers (such as gradually expanding channels and irregular cross-sections) makes them difficult to form by integral forging or machining, necessitating a multi-component welding assembly manufacturing route. Traditional fusion welding methods (such as tungsten inert gas welding and laser welding) suffer from defects such as uneven microstructure, residual stress concentration, and microcracks in the joint area due to large-area melting of the base metal, solidification segregation of the weld metal, and grain coarsening in the heat-affected zone. These defects make it difficult to meet the strength, creep, and fatigue reliability requirements for long-term service at 650℃, and the weld airtightness is difficult to achieve 10⁻⁻⁶. 9 The ultra-low leakage rate standard at the Pa·m³ / s level severely restricts the engineering application of S-CO2 diffusers.

[0003] Transient Liquid Phase (TLP) welding technology involves placing a low-melting-point interlayer foil between the base materials. Utilizing the instantaneous melting of the interlayer followed by isothermal solidification, metallurgical bonding between the base materials is achieved at a relatively low temperature, offering advantages such as uniform joint microstructure, narrow heat-affected zone, and low residual stress. However, traditional TLP welding interlayers often use crystalline alloy foils, which exhibit uneven melting behavior and are prone to forming low-melting-point eutectic phase residues during welding, leading to a decline in the high-temperature performance of the joint. Simultaneously, melting point pressure-dropping elements such as silicon and boron in the interlayer easily form brittle silicide and boride phases during diffusion, worsening the joint's toughness and crack resistance. For example, Chinese patent CN110253175A discloses an amorphous interlayer and a nickel-based single-crystal alloy gradient TLP process, but suffers from severe boride segregation in the joint area and insufficient creep strength at 650℃. For example, Chinese patent CN102392247B discloses a method for electroplating a localized area in the middle of a part used in diffusion welding. However, this method suffers from problems such as difficulty in controlling the uniformity of the plating thickness, high plating costs for large-sized components, and severe environmental pollution. Therefore, there is an urgent need to develop a novel TLP welding interlayer material and welding method to simultaneously address the technical bottlenecks of the need for high-temperature joint strength and ultra-low leakage rate airtightness, the contradiction between a wide process window and long-term microstructure stability, and the difficulty in synergistically optimizing interface wetting and filling with brittle phase control. Summary of the Invention

[0004] The purpose of this invention is to provide a nickel-based alloy welded structure for a 650℃ supercritical diffuser and its preparation method. This invention addresses the shortcomings of existing TLP welding, which struggle to balance the high-temperature strength, creep and fatigue reliability, and ultra-low leakage rate airtight sealing requirements of the joint area close to the base material; the inherent contradiction between diffusion kinetics and reaction thermodynamics between the low-temperature, short-duration, wide process window at the manufacturing end and the long-term microstructure and interfacial chemical stability (antioxidation and corrosion resistance) at 650℃ during service; and the difficulty in simultaneously optimizing the interface wetting flow filling to adapt to actual surface roughness and assembly tolerances and limiting Si / B related segregation and brittle phases to improve joint toughness and crack resistance through a single means.

[0005] As the core concept of this invention, it employs an innovative design that replaces traditional crystalline foil with an amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil, primarily to overcome the bottleneck of microstructure control in TLP welding joints. Due to its long-range disordered and short-range ordered atomic arrangement, the amorphous alloy exhibits melting and diffusion behavior drastically different from crystalline alloys during instantaneous liquid-phase diffusion welding: the uniformity of the amorphous structure ensures a uniform glass transition and melting of the foil when heated to the welding temperature, avoiding premature melting and uneven liquid phase formation caused by grain boundary segregation in crystalline alloys; silicon and boron are uniformly dispersed in the amorphous matrix in a solid solution state, and during subsequent isothermal solidification and diffusion, the diffusion of silicon and boron into the base material is more uniform and the rate is controllable, significantly reducing the segregation and precipitation of brittle silicide and boride phases in the joint area; simultaneously, the high fluidity of the amorphous alloy allows it to fully wet the micro-roughness morphology of the base material surface after melting, filling assembly gaps and ensuring the integrity and airtightness of the interfacial metallurgical bond.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A nickel-based alloy welded structure for a 650℃ supercritical diffuser includes a first nickel-based alloy component and a second nickel-based alloy component, wherein the first nickel-based alloy component and the second nickel-based alloy component are welded together by transient liquid phase diffusion welding to form a welded joint area. The welded joint area is formed at the interface between the two components by instantaneous liquid phase diffusion welding of an amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil, the thickness of which is 20-60μm. The amorphous structure of the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil was determined by X-ray diffraction. The determination criterion was that there were no indistinguishable crystal diffraction peaks in the X-ray diffraction pattern and only diffuse peaks were present. The amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil contains nickel, chromium, iron, silicon and boron by mass fraction, wherein the mass fraction of chromium is 5-25 wt%, the mass fraction of iron is 0-30 wt%, the mass fraction of silicon is 1-8 wt%, the mass fraction of boron is 0.5-4 wt%, and the balance is nickel, wherein the mass fraction of nickel is 45-75 wt%, and the sum of the mass fractions of all elements except unavoidable impurities is 100 wt%.

[0007] Furthermore, the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil is obtained by a spinning process from a master alloy prepared through the following steps: A1. Raw material preparation: Weigh nickel, chromium, iron, silicon, and boron to make the mass fraction of chromium in the prepared master alloy 5-25 wt%, iron 0-30 wt%, silicon 1-8 wt%, boron 0.5-4 wt%, with the balance being nickel, which has a mass fraction of 45-75 wt%, and the sum of the mass fractions of all elements, excluding unavoidable impurities, is 100 wt%. A2. Melting: Melting is carried out under vacuum conditions with a pressure of 1-50 Pa, so that the temperature of the melt reaches 1400-1550℃ and is held for 5-30 min. Then, a protective gas is introduced and the master alloy is obtained by casting under a protective atmosphere, wherein the protective atmosphere is argon or nitrogen. A3. Master alloy inspection: Inspect whether the chemical composition of the master alloy meets the mass fraction requirements of step A1. Master alloys that meet the requirements are used as raw materials for subsequent strip spinning.

[0008] Furthermore, the master alloy is prepared into the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil by the following steps: B1. Strip casting: After the master alloy is heated to 1350-1550℃ to form a melt, it is sprayed onto the surface of a rotating cooling wheel through a nozzle with an inner diameter of 0.5-2.0mm. The gap between the nozzle outlet and the surface of the rotating cooling wheel is 0.2-1.0mm. The strip is formed under an argon protective atmosphere. B2. Process parameters: The linear velocity of the cooling wheel is 20-50 m / s, and the pressure of the jet driving gas is 0.05-0.30 MPa; B3. Forming: Obtaining a strip with a thickness of 20-60μm and a width of 5-50mm, wherein the strip is the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil.

[0009] Furthermore, the post-processing of the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil includes: C1. Cutting: Cut the strip into foil segments with a length of 10-500mm; C2. Packaging: Sealed packaging under vacuum conditions of 1-50 Pa or under a protective atmosphere; C3. Quality control: The thickness fluctuation of the intermediate foil is controlled within ±10%.

[0010] Furthermore, the welding temperature of the instantaneous liquid phase diffusion welding is 1000-1150℃, the welding pressure is 2-20MPa, the holding time is 1-10h, and the welding environment is under vacuum conditions with a pressure of 1-50Pa or under protective atmosphere conditions; wherein, the welding temperature is higher than the solidus temperature of the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil and lower than the solidus temperatures of the first nickel-based alloy component and the second nickel-based alloy component.

[0011] Furthermore, the material grade of the first nickel-based alloy component is selected from GH4169 or Inconel718; the material grade of the second nickel-based alloy component is selected from GH4169 or Inconel718; before welding, the surface roughness Ra of the mating surfaces of the two components is 0.8-3.2μm, and the surface roughness Ra of the mating surfaces is measured by a stylus-type surface roughness tester, with the measurement conditions being a sampling length of 0.8mm and an evaluation length of 4.0mm; The equivalent weld layer thickness along the butt joint normal in the weld joint area is 0.05-0.50 mm, and the method for determining the equivalent weld layer thickness is as follows: The width of the metallurgical bonding zone was measured along the normal direction of the weld joint area on a metallographic microscope or scanning electron microscope image after the cross-sectional sample of the weld joint area at the butt joint was ground, polished, and etched; the leakage rate of the weld joint area was 1×10⁻ 9 -1×10⁻ 6 Pa·m³ / s, and the leakage rate is determined by helium mass spectrometry leak detection method, and the determination conditions are test temperature 20-25℃, pressure difference across the specimen 0.10-0.20MPa, and detection time 60-300s.

[0012] As a concept of this invention, it employs an amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil and a strictly controlled instantaneous liquid phase diffusion welding process in synergistic design. This is primarily used to enhance the overall performance of the weld joint area under supercritical conditions at 650℃, including high-temperature strength, creep resistance, and ultra-low leakage rate airtightness. By setting the interlayer foil thickness within the key parameter range of 20-60 μm, the following multiple effects are achieved during the welding process: When the thickness is less than 20 μm, the amount of molten liquid phase in the foil is insufficient to effectively wet and fill the micro-roughness pits and assembly gaps on the mating surfaces of the base materials, resulting in unbonded areas at the interface and making it difficult to achieve a leakage rate of 10⁻⁻⁶. 9On the order of Pa·m³ / s; when the thickness exceeds 60μm, the excessive thickness of the liquid phase layer prolongs the diffusion path of melting point pressure drop elements such as silicon and boron into the base material during the isothermal solidification stage, significantly increasing the diffusion time. Furthermore, the central region of the liquid phase layer is prone to retaining incompletely diffused silicon and boron enriched phases, forming brittle borides and silicide inclusions, which degrade joint toughness and high-temperature creep strength. Foil materials with a thickness in the range of 20-60μm, when melted at welding temperatures of 1000-1150℃, form a liquid phase layer of moderate thickness, sufficient to fully wet and fill the interface. This method achieves a dense bond and allows for sufficient diffusion of silicon and boron into the base material during a 1-10 hour heat preservation period. This results in a homogenized microstructure in the joint area with the brittle phase content controlled within acceptable limits. The equivalent weld layer thickness remains stable at 0.05-0.50 mm. This equivalent layer contains fine grains and a uniform microstructure, free from significant segregation and porosity defects. Consequently, it simultaneously achieves high-temperature strength approaching that of the base material (650℃ tensile strength retention ≥85%, creep rupture time ≥70% of the base material) and ultra-low leakage rate airtightness (leakage rate 1×10⁻⁻⁻⁶). 9 -1×10⁻ 6 (Pa·m³ / s). In addition, by controlling the welding pressure to 2-20MPa and applying moderate extrusion to the liquid phase layer during the heat preservation process, the liquid phase is promoted to penetrate into the grain boundaries of the base material and the rapid diffusion of silicon and boron is facilitated, the isothermal solidification time is shortened, and the joint microstructure is further optimized.

[0013] This invention also discloses a method for preparing the above-mentioned 650℃ supercritical diffuser nickel-based alloy welded structure, characterized by comprising the following steps: S1. Provide a first nickel-based alloy component and a second nickel-based alloy component; S2. The amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil is placed in a single layer at the interface between the two components, and the intermediate layer foil completely covers the area to be welded at the interface. S3. Under vacuum conditions with a pressure of 1-50 Pa or under protective atmosphere conditions, apply welding pressure to the two components and heat them to the welding temperature to perform instantaneous liquid phase diffusion welding, wherein the welding temperature is 1000-1150℃, the welding pressure is 2-20 MPa, the holding time is 1-10 h, and the welding pressure is maintained continuously during the process of heating to the welding temperature and throughout the holding time. S4. Cool to room temperature (20-25℃) to obtain a nickel-based alloy welded structure.

[0014] Furthermore, the protective atmosphere in step S3 is argon or nitrogen.

[0015] Furthermore, step S4 is followed by a heat treatment step S5, which includes solution heat treatment and aging heat treatment. The solution heat treatment is performed at a temperature of 950-1100℃ for a duration of 0.5-2.0 h, and the aging heat treatment is performed at a temperature of 650-800℃ for a duration of 2-16 h.

[0016] Furthermore, the heating rate in step S3 is 2-20℃ / min, and the cooling rate in step S4 is 0.5-10℃ / min.

[0017] Furthermore, the amorphous structure of the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil is determined by differential scanning calorimetry. The determination criteria are that when differential scanning calorimetry is performed at a heating rate of 10℃ / min under an inert atmosphere, it has glass transition characteristics and the measured glass transition temperature Tg is 400-600℃.

[0018] As another aspect of this invention, a technical route for preparing amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil is adopted using a master alloy vacuum melting and rapid solidification process. This is mainly used to enhance the stability of the amorphous structure, compositional uniformity, and welding wettability of the foil. In the master alloy preparation stage, the foil is melted at 1400-1550℃ under a vacuum of 1-50Pa and held for 5-30 minutes to ensure the full dissolution and mixing of the five elements (nickel, chromium, iron, silicon, and boron), avoiding oxidation and impurity contamination, thus obtaining a master alloy with uniform composition. Subsequently, it is cast under a protective atmosphere to prevent element burn-off and oxidation. In the rapid solidification stage, the master alloy is heated to 1350-1550℃ to form a uniform melt, which is then sprayed through a nozzle with an inner diameter of 0.5-2.0mm at a driving pressure of 0.05-0.30MPa onto the surface of a rotating cooling wheel with a linear velocity of 20-50m / s. The gap between the nozzle and the cooling wheel is controlled at 0.2-1.0mm to achieve 10 6 -10 7 The ultra-high cooling rate, on the order of K / s, enables the melt to cool in an extremely short time (10⁻³-10⁻³). 4s) Solidification is completed, inhibiting crystal nucleation and growth, forming an amorphous structure with long-range disorder and short-range order. This amorphous structure is determined by two characteristics: X-ray diffraction patterns showing only diffuse peaks and no crystalline diffraction peaks, and differential scanning calorimetry curves showing a glass transition temperature (Tg) of 400-600℃. Due to its uniform atomic distribution and absence of grain boundaries, amorphous foil has the following advantages in instantaneous liquid-phase diffusion welding: a single and uniform melting temperature, avoiding premature local melting of crystalline alloys caused by eutectic phases; silicon and boron elements are uniformly dispersed in solid solution, and their migration rate to the base material during isothermal solidification diffusion is controllable and uniformly distributed, significantly reducing the segregation of borides and silicides in the joint area; the molten amorphous alloy liquid phase has low viscosity and excellent fluidity, which can fully wet the microstructure of the base material with a surface roughness Ra of 0.8-3.2μm, fill the assembly gaps, and ensure the metallurgical bonding density and ultra-low leakage rate of the interface.

[0019] This invention focuses on the composition design of the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil, analyzing the synergistic effects of each element from the perspectives of microstructure control and interfacial reaction kinetics. Nickel, as the matrix element (45-75 wt%), provides the main framework for amorphous formation and excellent high-temperature strength and oxidation resistance; chromium (5-25 wt%) enhances the matrix strength through solid solution strengthening and diffuses to the base material interface in the later stages of welding to form a dense Cr2O3 oxide film, significantly enhancing the joint's oxidation and corrosion resistance in a supercritical CO2 environment at 650℃; iron (0-30 wt%) serves as a balance element between cost control and amorphous formation capability, and its appropriate addition reduces alloy costs without significantly degrading the critical cooling rate for amorphous formation; silicon (45-75 wt%)... Silicon and boron (1-8 wt%) and boron (0.5-4 wt%) play a dual role as melting point pressure drop elements and amorphous formation promoters: On the one hand, the addition of silicon and boron makes the liquidus temperature of the interlayer foil significantly lower than that of the base material (reduced by 80-150℃), achieving interlayer melting at a welding temperature of 1000-1150℃ while the base material remains solid, satisfying the basic conditions for instantaneous liquid phase diffusion welding; on the other hand, the atomic radii of silicon and boron are significantly different from those of nickel, chromium, and iron, generating strong topological and chemical short-program during rapid solidification, inhibiting crystal nucleation and promoting amorphous phase formation. The key to the synergistic effect lies in the synergistic diffusion of chromium with silicon and boron. During the isothermal solidification stage, the diffusion rate of chromium into the matrix is ​​slower than that of silicon and boron, forming a chromium-rich transition layer in the joint area. This layer not only prevents the excessively rapid diffusion of silicon and boron, which would lead to enrichment in the central region, but also provides an anti-oxidation barrier at the interface. The nickel-chromium-iron ternary matrix has moderate solid solubility for silicon and boron. During the 1-10 h holding time, silicon and boron can diffuse sufficiently into the matrix without leaving excessive brittle phase in the joint area. The joint structure evolves into fine γ-Ni solid solution grains + a small amount of M 23The composite structure of C6-type carbide + trace silicide / boride dispersed distribution achieves synergistic optimization of high-temperature strength, toughness and ultra-low leakage rate airtightness.

[0020] Beneficial technical effects 1. Overcoming the technical bottleneck of traditional TLP welding joints in achieving both high-temperature strength and ultra-low leakage rate airtightness: By replacing traditional crystalline foil with amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil (20-60μm thickness), combined with instantaneous liquid phase diffusion welding process (temperature 1000-1150℃, pressure 2-20MPa, holding time 1-10h), a uniform and dense joint area with an equivalent weld layer thickness of 0.05-0.50mm is obtained. The tensile strength retention rate of the welded joint at 650℃ reaches more than 85% of the base material, and the creep rupture time reaches more than 70% of the base material, while the leakage rate reaches 1×10⁻ 9 -1×10⁻ 6 The Pa·m³ / s level meets the stringent service requirements of diffusers in supercritical CO2 power generation systems, and is superior to traditional TLP welding (which typically has a leakage rate of 10⁻⁻⁻⁶). 6 -10⁻ 5 The Pa·m³ / s significantly improves airtightness.

[0021] 2. Significantly widens the welding process window and shortens the welding cycle, reducing manufacturing costs and deformation risks: Due to its uniform melting behavior and excellent flow and wettability, amorphous foil allows for flexible selection of welding temperature ranges within a 150°C range of 1000-1150°C. Qualified joints can be obtained with welding pressures ranging from 2-20 MPa and holding times from 1-10 hours. Compared to traditional crystalline foil TLP welding (temperature window typically ≤50°C, holding time ≥20 hours), the process tolerance is improved by more than 3 times, and the welding cycle is shortened by more than 50%. The wide process window reduces the sensitivity of the welding process to temperature fluctuations and pressure control precision, lowers equipment requirements and operational difficulty, and improves the yield and consistency of welding large-size complex diffusers. At the same time, the lower welding temperature and shorter holding time reduce the high-temperature exposure time of components, significantly reducing thermal deformation and residual stress levels.

[0022] 3. Achieving uniform microstructure and long-term service stability in the joint area: In the amorphous foil, silicon and boron are uniformly dispersed in a solid solution state. During the isothermal solidification and diffusion stage of instantaneous liquid phase diffusion welding, the migration rate of silicon and boron to the base material is controllable and uniformly distributed. The size of brittle silicide and boride phases in the joint area is controlled at the submicron level and the volume fraction is ≤5%, which is more than 50% lower than that of traditional crystalline foil TLP welding (brittle phase volume fraction is usually 10-20%). The grain size in the joint area is small (5-15μm) and the microstructure is uniform, with no obvious segregation bands and pore defects. After long-term aging at 650℃ for 1000h, the microhardness decrease rate in the joint area is ≤8% and the brittle phase size increase rate is ≤15%, with excellent microstructure stability, ensuring the long-term (≥30000h) reliable service of the diffuser in the supercritical CO2 cycle system.

[0023] 4. Optimized interface wetting and filling performance to suit actual surface roughness and assembly tolerances: The liquid phase formed after the amorphous foil melts at the welding temperature has low viscosity (typically 50-70% of the viscosity of the liquid phase of crystalline alloys) and moderate surface tension, which can fully wet the micro-pits and peak-valve morphology of the base material mating surface with a roughness Ra of 0.8-3.2μm, and fill the assembly gap (allowable gap ≤0.1mm), achieving 100% metallurgical bonding with no unbonded areas; the moderate extrusion effect of the welding pressure of 2-20MPa further promotes the penetration of the liquid phase into the grain boundaries of the base material, strengthens the interface bonding strength, and the interface bonding strength in the joint area reaches more than 90% of the strength of the base material; the excellent wetting and filling performance reduces the requirements for pre-weld surface treatment (only mechanical grinding to Ra≤3.2μm is required, without electrolytic polishing or chemical etching), simplifies the welding preparation process, and improves production efficiency. Attached Figure Description

[0024] Figure 1 The images show the XRD amorphous structures of Example 1 and Comparative Example 8.

[0025] Figure 2 The diagram shows the DSC glass transition and crystallization behavior of Examples 1, 3 and Comparative Example 3.

[0026] Figure 3 The images show the SEM-EDS line scan Si distribution along the weld interface for Examples 1, 4, and 6.

[0027] Figure 4 The image shows the distribution of SEM-EDS line scan B along the weld interface for Examples 1, 5, and 6.

[0028] Figure 5 The images show the distribution of Si vertical weld seam in Example 1 and Comparative Example 4 using EPMA or SIMS depth profiling.

[0029] Figure 6The image shows the EPMA or SIMS depth profile of Example 1 and Comparative Example 5, with the vertical weld direction distribution diagram shown.

[0030] Figure 7 This is a macroscopic optical photograph of the nickel-based alloy welded structure of Example 1.

[0031] Figure 8 This is a scanning electron microscope image of the weld joint area in Example 1.

[0032] Figure 9 This is a transmission electron microscope (TEM) image of the weld joint area in Example 1. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Example 1

[0034] This embodiment provides a nickel-based alloy welded structure for a 650℃ supercritical diffuser, including a first nickel-based alloy component and a second nickel-based alloy component. The first and second nickel-based alloy components are welded together via transient liquid-phase diffusion welding to form a weld joint area. Both the first and second nickel-based alloy components are made of GH4169 material.

[0035] In this embodiment, the welded joint area at the interface between the two components is formed by transient liquid-phase diffusion welding of an amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil. The thickness of the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil in this embodiment is 40 μm. The amorphous structure of the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil in this embodiment is determined by X-ray diffraction, with the criterion being the absence of indistinguishable crystalline diffraction peaks and the presence of only diffuse peaks in the X-ray diffraction pattern. The amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil in this embodiment contains nickel, chromium, iron, silicon, and boron by mass fraction, wherein the mass fractions of nickel are 60 wt%, chromium 15 wt%, iron 15 wt%, silicon 7 wt%, and boron 3 wt%, and the sum of the mass fractions of all elements, excluding unavoidable impurities, is 100 wt%. The amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil of this embodiment was determined to have an amorphous structure by differential scanning calorimetry. When differential scanning calorimetry was performed under an inert atmosphere at a heating rate of 10℃ / min, it exhibited glass transition characteristics, and the measured glass transition temperature Tg was 500℃.

[0036] The amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil of this embodiment is obtained by a casting process using a master alloy prepared through the following steps. The preparation steps of the master alloy in this embodiment include: in the raw material preparation step, nickel, chromium, iron, silicon and boron are weighed to make the mass fraction of nickel 60wt%, chromium 15wt%, iron 15wt%, silicon 7wt%, and boron 3wt% in the prepared master alloy, and the sum of the mass fractions of each element except for unavoidable impurities is 100wt%; in the melting step, melting is carried out under vacuum conditions of 25Pa pressure, the melt temperature reaches 1475℃ and is held for 17min, and then argon gas is introduced as a protective gas and cast under argon protective atmosphere to obtain the master alloy; in the master alloy inspection step, the chemical composition of the master alloy of this embodiment is inspected to ensure that it meets the mass fraction requirements of the raw material preparation step, and this master alloy is used as the raw material for subsequent casting.

[0037] The master alloy of this embodiment is prepared into the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil of this embodiment through the following steps: In the strip spinning step, the master alloy of this embodiment is heated to 1450°C to form a melt, and then sprayed onto the surface of a rotating cooling wheel through a nozzle with an inner diameter of 1.2 mm. The gap between the nozzle outlet and the surface of the rotating cooling wheel of this embodiment is 0.6 mm. The strip is spun and formed under an argon protective atmosphere. The process parameters are that the linear speed of the cooling wheel of this embodiment is 35 m / s and the pressure of the spray driving gas is 0.17 MPa. After forming, a strip with a thickness of 40 μm and a width of 27 mm is obtained. The strip of this embodiment is the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil of this embodiment.

[0038] The post-processing of the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil in this embodiment includes: cutting the strip of this embodiment into foil segments with a length of 250mm in the cutting step; sealing and packaging under vacuum conditions with a pressure of 25Pa in the packaging step; and controlling the thickness fluctuation of the interlayer foil in this embodiment within ±10% in the quality control step.

[0039] The nickel-based alloy welded structure of this embodiment is obtained by the following preparation method: In step S1, a first nickel-based alloy component and a second nickel-based alloy component are provided. Before welding, the surface roughness Ra of the two components in this embodiment is 2.0 μm, and the surface roughness Ra of the two components in this embodiment is measured by a stylus-type surface roughness meter under the following conditions: sampling length 0.8 mm and evaluation length 4.0 mm. In step S2, the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil of this embodiment is placed in a single layer at the interface of the two components in this embodiment, and the intermediate layer foil of this embodiment completely covers the area to be welded at the interface of this embodiment. In step S3, under a vacuum condition of 25 Pa, welding pressure is applied to the two components of this embodiment and heated to the welding temperature for instantaneous liquid phase diffusion welding. The welding temperature of this embodiment is 1075 °C. The welding pressure is 10 MPa, the holding time is 5 h, and the welding pressure in this embodiment is maintained continuously during the heating process to the welding temperature of this embodiment and throughout the holding time. The welding temperature in this embodiment is higher than the solidus temperature of the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil of this embodiment and lower than the solidus temperatures of the first nickel-based alloy component and the second nickel-based alloy component of this embodiment. The heating rate in step S3 is 10 °C / min. In step S4, the temperature is cooled to room temperature of 23 °C at a cooling rate of 5 °C / min to obtain a nickel-based alloy welded structure. In step S5, heat treatment is performed. The heat treatment in this embodiment includes solution heat treatment and aging heat treatment. The solution heat treatment temperature in this embodiment is 1025 °C and the solution heat treatment time is 1.2 h. The aging heat treatment temperature in this embodiment is 725 °C and the aging heat treatment time is 9 h.

[0040] In this embodiment, the equivalent weld layer thickness along the butt joint normal in the weld joint area is 0.25 mm. The equivalent weld layer thickness is measured by taking a cross-sectional sample of the weld joint area at the butt joint interface, polishing and etching it, and then measuring the width of the metallurgical bonding zone along the butt joint normal on an image obtained using a metallographic microscope or scanning electron microscope. The leakage rate of the weld joint area in this embodiment is 5 × 10⁻ 8 Pa·m³ / s, and the leak rate in this embodiment was determined by helium mass spectrometry leak detection. The test conditions in this embodiment were: test temperature 22℃, pressure difference between the two sides of the specimen 0.15MPa, and detection time 120s.

[0041] Features of Example 1: This example employs a moderate alloy composition design, with nickel content of 60wt%, chromium content of 15wt%, iron content of 15wt%, silicon content of 7wt%, and boron content of 3wt%. The elemental proportions are balanced, the foil thickness of 40μm is moderate, and the welding temperature of 1075℃, welding pressure of 10MPa, and holding time of 5h are all moderate parameters. The glass transition temperature of 500℃ is in the middle range, and the solution temperature of 1025℃ and aging temperature of 725℃ are appropriately matched. The overall process parameters are balanced and stable, exhibiting good process reproducibility and joint quality stability. This example is suitable for welding and manufacturing supercritical diffusers at 650℃ under standard operating conditions, and is particularly suitable for mass production and applications requiring high joint performance stability. It can be widely used for connecting high-temperature and high-pressure components in supercritical thermal power units. Example 2

[0042] This embodiment provides a nickel-based alloy welded structure for a 650℃ supercritical diffuser, including a first nickel-based alloy component and a second nickel-based alloy component. The first and second nickel-based alloy components are welded together via transient liquid-phase diffusion welding to form a weld joint area. Both the first and second nickel-based alloy components are made of Inconel 718.

[0043] In this embodiment, the weld joint area at the interface between the two components is formed by transient liquid-phase diffusion welding of an amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil. The thickness of the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil in this embodiment is 30 μm. The amorphous structure of the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil in this embodiment is determined by X-ray diffraction, with the criterion being the absence of indistinguishable crystalline diffraction peaks and the presence of only diffuse peaks in the X-ray diffraction pattern. The amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil in this embodiment contains nickel, chromium, iron, silicon, and boron by mass fraction, wherein the mass fraction of nickel is 50 wt%, chromium is 18 wt%, iron is 22 wt%, silicon is 6 wt%, and boron is 4 wt%, and the sum of the mass fractions of all elements, excluding unavoidable impurities, is 100 wt%. The amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil of this embodiment was determined to have an amorphous structure by differential scanning calorimetry. When differential scanning calorimetry was performed under an inert atmosphere at a heating rate of 10℃ / min, it exhibited glass transition characteristics, and the measured glass transition temperature Tg was 450℃.

[0044] The amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil of this embodiment is obtained by a casting process using a master alloy prepared through the following steps. The preparation steps of the master alloy in this embodiment include: in the raw material preparation step, nickel, chromium, iron, silicon and boron are weighed to make the mass fraction of nickel 50wt%, chromium 18wt%, iron 22wt%, silicon 6wt%, and boron 4wt% in the prepared master alloy, and the sum of the mass fractions of each element except for unavoidable impurities is 100wt%; in the melting step, melting is carried out under vacuum conditions of 15Pa, the melt temperature reaches 1420℃ and is held for 10min, and then nitrogen gas is introduced as a protective gas and the master alloy is cast under a nitrogen protective atmosphere; in the master alloy inspection step, the chemical composition of the master alloy in this embodiment is inspected to ensure that it meets the mass fraction requirements of the raw material preparation step, and this master alloy is used as the raw material for subsequent casting.

[0045] The master alloy of this embodiment is prepared into the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil of this embodiment through the following steps: In the strip spinning step, the master alloy of this embodiment is heated to 1380°C to form a melt, and then sprayed onto the surface of a rotating cooling wheel through a nozzle with an inner diameter of 0.8 mm. The gap between the nozzle outlet and the surface of the rotating cooling wheel of this embodiment is 0.4 mm. The strip is spun and formed under an argon protective atmosphere. The process parameters are that the linear speed of the cooling wheel of this embodiment is 42 m / s and the pressure of the spray driving gas is 0.22 MPa. After forming, a strip with a thickness of 30 μm and a width of 15 mm is obtained. The strip of this embodiment is the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil of this embodiment.

[0046] The post-processing of the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil in this embodiment includes: cutting the strip of this embodiment into foil segments with a length of 150mm in the cutting step; sealing and packaging under an argon protective atmosphere in the packaging step; and controlling the thickness fluctuation of the interlayer foil in this embodiment within ±10% in the quality control step.

[0047] The nickel-based alloy welded structure of this embodiment is obtained by the following preparation method: In step S1, a first nickel-based alloy component and a second nickel-based alloy component are provided. Before welding, the surface roughness Ra of the two components in this embodiment is 1.2 μm, and the surface roughness Ra of the two components in this embodiment is measured by a stylus-type surface roughness meter under the following conditions: sampling length 0.8 mm and evaluation length 4.0 mm. In step S2, the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil of this embodiment is placed in a single layer at the interface of the two components in this embodiment, and the intermediate layer foil of this embodiment completely covers the area to be welded at the interface of this embodiment. In step S3, under a nitrogen protective atmosphere, welding pressure is applied to the two components of this embodiment and heated to the welding temperature for instantaneous liquid phase diffusion welding. The welding temperature of this embodiment is 1040℃, and the welding pressure of this embodiment is... The pressure is 6 MPa, the holding time is 3 hours, and the welding pressure in this embodiment is maintained continuously during the heating process to the welding temperature of this embodiment and throughout the holding time. The welding temperature of this embodiment is higher than the solidus temperature of the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil of this embodiment and lower than the solidus temperatures of the first nickel-based alloy component and the second nickel-based alloy component of this embodiment. The heating rate in step S3 is 15℃ / min. In step S4, the temperature is cooled to room temperature of 22℃ at a cooling rate of 7℃ / min to obtain a nickel-based alloy welded structure. In step S5, heat treatment is performed. The heat treatment in this embodiment includes solution heat treatment and aging heat treatment. The solution heat treatment temperature in this embodiment is 980℃ and the solution heat treatment time is 0.8 hours. The aging heat treatment temperature in this embodiment is 680℃ and the aging heat treatment time is 6 hours.

[0048] In this embodiment, the equivalent weld layer thickness along the butt joint normal in the weld joint area is 0.15 mm. The equivalent weld layer thickness is measured by taking a cross-sectional sample of the weld joint area at the butt joint interface, polishing and etching it, and then measuring the width of the metallurgical bonding zone along the butt joint normal on an image obtained using a metallographic microscope or scanning electron microscope. The leakage rate of the weld joint area in this embodiment is 2 × 10⁻ 8 Pa·m³ / s, and the leak rate in this embodiment was determined by helium mass spectrometry leak detection. The test conditions in this embodiment were: test temperature 21℃, pressure difference across the specimen 0.12MPa, and detection time 90s.

[0049] Features of Example 2: This example employs a low-nickel, high-iron, and high-boron alloy composition design, with nickel content of 50wt%, chromium content of 18wt%, iron content of 22wt%, silicon content of 6wt%, and boron content of 4wt%. Increasing the iron and boron content reduces costs and enhances amorphous formation capability. The foil thickness of 30μm is relatively thin, and the melting temperature of 1420℃ and the strip casting temperature of 1380℃ are relatively low, contributing to energy conservation and consumption reduction. The cooling wheel linear speed of 42m / s is relatively fast, resulting in a finer microstructure. The welding temperature of 1040℃ is relatively low, the welding pressure of 6MPa is relatively low, and the holding time of 3h is relatively short, achieving a rapid and efficient welding process. The glass transition temperature of 450℃ is relatively low, as are the solution temperature of 980℃ and the aging temperature of 680℃. The heating rate of 15℃ / min and the cooling rate of 7℃ / min are relatively fast. This example is suitable for applications with high cost control requirements, particularly for the rapid welding of small and medium-sized diffuser components. While ensuring joint performance, it can significantly shorten the production cycle and reduce energy consumption, and is suitable for 650℃ supercritical systems under medium service conditions. Example 3

[0050] This embodiment provides a nickel-based alloy welded structure for a 650℃ supercritical diffuser, including a first nickel-based alloy component and a second nickel-based alloy component. The first and second nickel-based alloy components are welded together via transient liquid-phase diffusion welding to form a weld joint area. Both the first and second nickel-based alloy components are made of GH4169 material.

[0051] In this embodiment, the welded joint area at the interface between the two components is formed by transient liquid-phase diffusion welding of an amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil. The thickness of the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil in this embodiment is 52 μm. The amorphous structure of the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil in this embodiment is determined by X-ray diffraction, with the criterion being the absence of indistinguishable crystalline diffraction peaks and the presence of only diffuse peaks in the X-ray diffraction pattern. The amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil in this embodiment contains nickel, chromium, iron, silicon, and boron by mass fraction, wherein the mass fraction of nickel is 72 wt%, chromium is 10 wt%, iron is 8 wt%, silicon is 6 wt%, and boron is 4 wt%, and the sum of the mass fractions of all elements, excluding unavoidable impurities, is 100 wt%. The amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil of this embodiment was determined to have an amorphous structure by differential scanning calorimetry. When differential scanning calorimetry was performed under an inert atmosphere at a heating rate of 10℃ / min, it exhibited glass transition characteristics, and the measured glass transition temperature Tg was 570℃.

[0052] The amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil of this embodiment is obtained by a casting process using a master alloy prepared through the following steps. The preparation steps of the master alloy in this embodiment include: in the raw material preparation step, nickel, chromium, iron, silicon and boron are weighed to make the mass fraction of nickel 72wt%, chromium 10wt%, iron 8wt%, silicon 6wt%, and boron 4wt% in the prepared master alloy, and the sum of the mass fractions of each element except for unavoidable impurities is 100wt%; in the melting step, melting is carried out under vacuum conditions of 40Pa, the melt temperature reaches 1530℃ and is held for 24min, and then argon gas is introduced as a protective gas and cast under argon protective atmosphere to obtain the master alloy; in the master alloy inspection step, the chemical composition of the master alloy in this embodiment is inspected to ensure that it meets the mass fraction requirements of the raw material preparation step, and this master alloy is used as the raw material for subsequent casting.

[0053] The master alloy of this embodiment is prepared into the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil of this embodiment through the following steps: In the strip spinning step, the master alloy of this embodiment is heated to 1520°C to form a melt, and then sprayed onto the surface of a rotating cooling wheel through a nozzle with an inner diameter of 1.7 mm. The gap between the nozzle outlet and the surface of the rotating cooling wheel of this embodiment is 0.85 mm. The strip is spun and formed under an argon protective atmosphere. The process parameters are that the linear speed of the cooling wheel of this embodiment is 28 m / s and the pressure of the spray driving gas is 0.12 MPa. After forming, a strip with a thickness of 52 μm and a width of 38 mm is obtained. The strip of this embodiment is the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil of this embodiment.

[0054] The post-processing of the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil in this embodiment includes: cutting the strip of this embodiment into foil segments with a length of 380mm in the cutting step; sealing and packaging under vacuum conditions with a pressure of 40Pa in the packaging step; and controlling the thickness fluctuation of the interlayer foil in this embodiment within ±10% in the quality control step.

[0055] The nickel-based alloy welded structure of this embodiment is obtained by the following preparation method: In step S1, a first nickel-based alloy component and a second nickel-based alloy component are provided. Before welding, the surface roughness Ra of the two components in this embodiment is 2.8 μm, and the surface roughness Ra of the two components in this embodiment is measured by a stylus-type surface roughness meter under the following conditions: sampling length 0.8 mm and evaluation length 4.0 mm. In step S2, the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil of this embodiment is placed in a single layer at the interface of the two components in this embodiment, and the intermediate layer foil of this embodiment completely covers the area to be welded at the interface of this embodiment. In step S3, under a vacuum condition of 40 Pa, welding pressure is applied to the two components of this embodiment and heated to the welding temperature for instantaneous liquid phase diffusion welding. The welding temperature of this embodiment is 1120 °C. The welding pressure is 16 MPa, the holding time is 8 h, and the welding pressure in this embodiment is maintained continuously during the heating process to the welding temperature of this embodiment and throughout the holding time. The welding temperature in this embodiment is higher than the solidus temperature of the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil of this embodiment and lower than the solidus temperatures of the first nickel-based alloy component and the second nickel-based alloy component of this embodiment. The heating rate in step S3 is 6 °C / min. In step S4, the temperature is cooled to room temperature of 24 °C at a cooling rate of 2 °C / min to obtain a nickel-based alloy welded structure. In step S5, heat treatment is performed. The heat treatment in this embodiment includes solution heat treatment and aging heat treatment. The solution heat treatment temperature in this embodiment is 1080 °C and the solution heat treatment time is 1.8 h. The aging heat treatment temperature in this embodiment is 780 °C and the aging heat treatment time is 14 h.

[0056] In this embodiment, the equivalent weld layer thickness along the butt joint normal in the weld joint area is 0.42 mm. The equivalent weld layer thickness is measured by taking a cross-sectional sample of the weld joint area at the butt joint interface, polishing and etching it, and then measuring the width of the metallurgical bonding zone along the butt joint normal on an image obtained using a metallographic microscope or scanning electron microscope. The leakage rate of the weld joint area in this embodiment is 8 × 10⁻⁻⁻⁶. 7 Pa·m³ / s, and the leak rate in this embodiment was determined by helium mass spectrometry leak detection. The test conditions in this embodiment were: test temperature 24℃, pressure difference between the two sides of the specimen 0.18MPa, and detection time 240s.

[0057] Features of Example 3: This example uses a high-nickel, low-iron alloy composition design, with a nickel content of 72 wt%, a chromium content of 10 wt%, an iron content of 8 wt%, a silicon content of 6 wt%, and a boron content of 4 wt%. The high nickel content significantly improves the high-temperature stability and oxidation resistance of the alloy. The foil thickness of 52 μm provides a sufficient amount of liquid phase to fill the weld gap. The high melting temperature of 1530℃ and the high strip casting temperature of 1520℃ ensure that the alloy is fully melted and homogenized. The slow cooling wheel speed of 28 m / s gives the foil better flexibility. The high welding temperature of 1120℃, the high welding pressure of 16 MPa, and the long holding time of 8 h provide sufficient diffusion time to form a uniform joint structure. The high glass transition temperature of 570℃ indicates excellent thermal stability of the alloy. The high solution temperature of 1080℃ and the high aging temperature of 780℃ can obtain better mechanical properties. The slow heating rate of 6℃ / min and the slow cooling rate of 2℃ / min can reduce thermal stress. This embodiment is suitable for application scenarios with extremely high requirements for joint quality and service performance. It is particularly suitable for welding large critical diffuser components and can be used stably for a long time in harsh high-temperature environments. It is also suitable for extreme conditions such as ultra-supercritical thermal power units. Example 4

[0058] This embodiment provides a nickel-based alloy welded structure for a 650℃ supercritical diffuser, including a first nickel-based alloy component and a second nickel-based alloy component. The first and second nickel-based alloy components are welded together via transient liquid-phase diffusion welding to form a weld joint area. Both the first and second nickel-based alloy components are made of Inconel 718.

[0059] In this embodiment, the welded joint area at the interface between the two components is formed by transient liquid-phase diffusion welding of an amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil. The thickness of the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil in this embodiment is 24 μm. The amorphous structure of the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil in this embodiment is determined by X-ray diffraction, with the criterion being the absence of indistinguishable crystalline diffraction peaks and the presence of only diffuse peaks in the X-ray diffraction pattern. The amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil in this embodiment contains nickel, chromium, iron, silicon, and boron by mass fraction, wherein the mass fraction of nickel is 48 wt%, chromium is 20 wt%, iron is 25 wt%, silicon is 4 wt%, and boron is 3 wt%, and the sum of the mass fractions of all elements, excluding unavoidable impurities, is 100 wt%. The amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil of this embodiment was determined to have an amorphous structure by differential scanning calorimetry. When differential scanning calorimetry was performed under an inert atmosphere at a heating rate of 10℃ / min, it exhibited glass transition characteristics, and the measured glass transition temperature Tg was 420℃.

[0060] The amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil of this embodiment is obtained by a casting process using a master alloy prepared through the following steps. The preparation steps of the master alloy in this embodiment include: in the raw material preparation step, nickel, chromium, iron, silicon and boron are weighed so that the mass fraction of nickel in the prepared master alloy is 48wt%, the mass fraction of chromium is 20wt%, the mass fraction of iron is 25wt%, the mass fraction of silicon is 4wt%, and the mass fraction of boron is 3wt%, and the sum of the mass fractions of each element except for unavoidable impurities is 100wt%; in the melting step, melting is carried out under a vacuum condition of 5Pa, so that the melt temperature reaches 1440℃ and is held for 8min, and then nitrogen gas is introduced as a protective gas and cast under a nitrogen protective atmosphere to obtain the master alloy; in the master alloy inspection step, the chemical composition of the master alloy in this embodiment is inspected to ensure that it meets the mass fraction requirements of the raw material preparation step, and this master alloy is used as the raw material for subsequent casting.

[0061] The master alloy of this embodiment is prepared into the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil of this embodiment through the following steps: In the strip spinning step, the master alloy of this embodiment is heated to 1400°C to form a melt, and then sprayed onto the surface of a rotating cooling wheel through a nozzle with an inner diameter of 0.6 mm. The gap between the nozzle outlet and the surface of the rotating cooling wheel of this embodiment is 0.3 mm. The strip is spun and formed under an argon protective atmosphere. The process parameters are that the linear speed of the cooling wheel of this embodiment is 46 m / s and the pressure of the spray driving gas is 0.08 MPa. After forming, a strip with a thickness of 24 μm and a width of 8 mm is obtained. The strip of this embodiment is the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil of this embodiment.

[0062] The post-processing of the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil in this embodiment includes: cutting the strip of this embodiment into foil segments with a length of 50mm in the cutting step; sealing and packaging under an argon protective atmosphere in the packaging step; and controlling the thickness fluctuation of the interlayer foil in this embodiment within ±10% in the quality control step.

[0063] The nickel-based alloy welded structure of this embodiment is obtained by the following preparation method: In step S1, a first nickel-based alloy component and a second nickel-based alloy component are provided. Before welding, the surface roughness Ra of the two components in this embodiment is 1.0 μm, and the surface roughness Ra of the two components in this embodiment is measured by a stylus-type surface roughness meter under the following conditions: sampling length 0.8 mm and evaluation length 4.0 mm. In step S2, the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil of this embodiment is placed in a single layer at the interface of the two components in this embodiment, and the intermediate layer foil of this embodiment completely covers the area to be welded at the interface of this embodiment. In step S3, under the protection of argon gas, welding pressure is applied to the two components of this embodiment and heated to the welding temperature for instantaneous liquid phase diffusion welding. The welding temperature of this embodiment is 1010℃, and the welding pressure of this embodiment is... The pressure is 4 MPa, the holding time is 2 h, and the welding pressure in this embodiment is maintained continuously during the heating process to the welding temperature of this embodiment and throughout the holding time. The welding temperature of this embodiment is higher than the solidus temperature of the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil of this embodiment and lower than the solidus temperatures of the first nickel-based alloy component and the second nickel-based alloy component of this embodiment. The heating rate in step S3 is 18 °C / min. In step S4, the temperature is cooled to room temperature of 20 °C at a cooling rate of 8 °C / min to obtain a nickel-based alloy welded structure. In step S5, heat treatment is performed. The heat treatment in this embodiment includes solution heat treatment and aging heat treatment. The solution heat treatment temperature in this embodiment is 960 °C and the solution heat treatment time is 0.6 h. The aging heat treatment temperature in this embodiment is 665 °C and the aging heat treatment time is 4 h.

[0064] In this embodiment, the equivalent weld layer thickness along the butt joint normal in the weld joint area is 0.08 mm. The equivalent weld layer thickness is measured by taking a cross-sectional sample of the weld joint area at the butt joint interface, polishing and etching it, and then measuring the width of the metallurgical bonding zone along the butt joint normal on an image obtained using a metallographic microscope or scanning electron microscope. The leakage rate of the weld joint area in this embodiment is 3 × 10⁻ 9 Pa·m³ / s, and the leak rate in this embodiment was determined by helium mass spectrometry leak detection. The test conditions in this embodiment were: test temperature 20℃, pressure difference between the two sides of the specimen 0.10MPa, and detection time 80s.

[0065] Features of Example 4: This example uses an alloy composition design with 48wt% nickel (close to the lower end of the composition range), 20wt% chromium (close to the upper end of the composition range), and 25wt% iron (close to the upper end of the composition range). The silicon content is 4wt% and the boron content is 3wt%, which are at a medium level. The foil thickness is 24μm (close to the lower end of the thickness range), the vacuum pressure is 5Pa (close to the lower end of the vacuum range), the melting and holding time is 8min (close to the lower end of the time range), the master alloy heating temperature is 1400℃ (close to the lower end of the temperature range), the nozzle inner diameter is 0.6mm (close to the lower end of the size range), the nozzle gap is 0.3mm (close to the lower end of the gap range), the cooling wheel linear speed is 46m / s (close to the upper end of the speed range), and the injection pressure is 0.08MPa (close to the lower end of the pressure range). The strip width... 8mm width (close to the lower end of the width range), 50mm cutting length (close to the lower end of the length range), 1010℃ welding temperature (close to the lower end of the temperature range), 4MPa welding pressure (lower end of the pressure range), 2h holding time (lower end of the time range), 1.0μm surface roughness (lower end of the roughness range), 0.08mm equivalent weld layer thickness (lower end of the thickness range), 18℃ / min heating rate (upper end of the rate range), 8℃ / min cooling rate (upper end of the rate range), 960℃ solution temperature (lower end of the temperature range), 0.6h solution time (lower end of the time range), 665℃ aging temperature (lower end of the temperature range), 4h aging time (lower end of the time range), 420℃ glass transition temperature (lower end of the temperature range). This embodiment demonstrates the feasibility and adaptability of the technical solution within a wide parameter window by selecting multiple process parameters close to their defined ranges, making it suitable for precision diffuser components with thin weld layer requirements and extremely high sealing performance requirements. It is particularly suitable for rapid connection of small-sized thin-walled structures and can be applied to compact supercritical systems and weight-sensitive aerospace high-temperature components.

[0066] Comparative Example 1: Basically the same as Example 1, except that the thickness of the amorphous nickel-chromium-iron-silicon-boron alloy intermediate foil is 15 μm, while the amount of other components and preparation conditions remain unchanged.

[0067] Comparative Example 2: It is basically the same as Example 1, except that the thickness of the amorphous nickel-chromium-iron-silicon-boron alloy intermediate foil is 68 μm, while the amount of other components and preparation conditions remain unchanged.

[0068] Comparative Example 3: It is basically the same as Example 1, except that the mass fraction of nickel in the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil is 40 wt%, the mass fraction of chromium is 18 wt%, the mass fraction of iron is 25 wt%, the mass fraction of silicon is 12 wt%, and the mass fraction of boron is 5 wt%, while other preparation conditions and welding parameters remain unchanged.

[0069] Comparative Example 4: It is basically the same as Example 1, except that the mass fraction of silicon in the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil is 10 wt%, the mass fraction of nickel is adjusted to 57 wt%, and the mass fraction of other elements and preparation conditions remain unchanged.

[0070] Comparative Example 5: It is basically the same as Example 1, except that the mass fraction of boron in the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil is 5wt%, the mass fraction of nickel is adjusted to 58wt%, and the mass fraction of other elements and preparation conditions remain unchanged.

[0071] Comparative Example 6: It is basically the same as Example 1, except that the welding temperature of the instantaneous liquid phase diffusion welding is 950°C, while other welding parameters and preparation conditions remain unchanged.

[0072] Comparative Example 7: Basically the same as Example 1, except that the welding pressure of the instantaneous liquid phase diffusion welding is 1 MPa, while other welding parameters and preparation conditions remain unchanged.

[0073] Comparative Example 8: Basically the same as Example 1, except that a crystalline Ni-Cr-Fe-Si-B alloy foil (prepared by rolling process, with a polycrystalline structure, showing obvious crystal diffraction peaks in X-ray diffraction pattern) was used. The foil thickness was 40 μm, the chemical composition was the same as in Example 1, and other welding parameters remained unchanged.

[0074] Performance testing: Experiment 1: Tensile Properties of Joints at Room Temperature and High Temperature The test subject was a welded joint specimen. The purpose of the test was to evaluate the tensile strength, yield strength, and elongation of the welded joint at room temperature (25℃) and 650℃. The test principle was based on the stress-strain response characteristics of the material under uniaxial tensile load. The specimens were round bars with a diameter of 6mm and a gauge length of 30mm. The weld was located at the center of the gauge length. A universal testing machine was used to tensile the specimens until fracture at room temperature (25℃) and high temperature (650℃) with a strain rate of 0.005 / s. The high-temperature test was conducted under an argon protective atmosphere. Key parameters included test temperature (25℃ and 650℃ ± 2℃), strain rate (0.005 ± 0.001 / s), protective atmosphere (argon purity ≥ 99.99%), and loading rate control accuracy (± 2%). The specimens were held at 650℃ for 15 minutes before loading began. Data processing includes recording load-displacement curves, calculating tensile strength Rm, yield strength Rp0.2, and elongation after fracture A. At least 5 specimens are tested in each group, and the average value is taken. Outliers deviating from the average value by more than 15% are removed.

[0075] Experiment 2: Creep Strength and Inertia Test of Welded Joints at 650℃ The test subject was a high-temperature creep rupture specimen of a welded joint. The purpose of the test was to assess the creep strength and creep rupture time of the welded joint under long-term service conditions at 650℃. The test principle is based on the process of creep damage accumulation leading to fracture under constant temperature and load conditions. Experimental method: Smooth round bar specimens with a diameter of 6mm and a gauge length of 50mm were prepared, with the weld located at the center of the gauge. A lever-type high-temperature creep rupture testing machine was used. The test temperature was 650±2℃, and three stress levels were applied: 400MPa, 450MPa, and 500MPa. The test was conducted under argon protection or a vacuum of ≤1×10⁻³Pa, and the creep curve was recorded until the specimen fractured. Key parameters included temperature fluctuation (≤±2℃), stress application accuracy (±2%), displacement measurement accuracy (0.001mm), and protective atmosphere control. The specimen was heated to 650℃ and held at that temperature for 30 minutes before the load was applied. Data processing included plotting creep curves (strain-time), calculating creep strength (650℃ / 100h), creep rupture time, and steady-state creep rate. Three specimens were tested at each stress level, and the Larson-Miller parametric method was used to extrapolate the long-term creep strength.

[0076] Experiment 3: Helium mass spectrometry leak rate detection of welded joints The test subject is a complete welded joint sealing specimen. The purpose of the test is to quantitatively evaluate the airtightness and ultra-low leakage rate level of the welded joint. The test principle is based on the permeation and diffusion behavior of helium as a tracer gas through microscopic defects in the weld. The welded joint is fabricated into a closed cavity or tubular specimen. One side is filled with helium gas of ≥99.999% purity to a pressure difference of 0.10-0.20 MPa, and the other side is connected to the vacuum system of a helium mass spectrometer leak detector, with a vacuum degree ≤1×10⁻⁻⁻⁻⁶. 5 The leakage rate signal of helium gas penetrating the weld was detected at room temperature (20-25℃) for 60-300 seconds until the signal stabilized. Key parameters included tracer gas purity (helium ≥ 99.999%), pressure difference (0.10-0.20 MPa), and vacuum degree (≤ 1×10⁻⁻⁶). 5 The parameters for detection are Pa, detection sensitivity (1×10⁻¹² Pa·m³ / s), and ambient temperature (20-25℃). Before pressurization, the specimen needs to be pre-evacuated in a vacuum for 15 minutes to remove impurity gases. Data processing includes reading the stable leak rate value (Pa·m³ / s). Each specimen is tested 3 times and the average value is taken. The leak rate measurement results are used to evaluate the airtightness level of the specimen.

[0077] Experiment 4: Microstructure and Phase Composition Analysis of Welded Joints The test object is a metallographic specimen of the weld joint cross-section. The purpose of the test is to observe the microstructure, grain size, phase distribution, and elemental segregation of the joint area. The test principle is based on imaging of secondary electrons and backscattered electron signals generated by the interaction between the electron beam and the sample, as well as characteristic X-ray elemental analysis. The experimental method involves cutting a cross-sectional specimen perpendicular to the weld direction, and preparing the metallographic specimen through mounting, grinding (240#-2000# sandpaper), polishing (0.5μm diamond polishing paste), and etching (aqua regia or Marble reagent etching for 5-15s). The microstructure of the joint area is observed using scanning electron microscopy (SEM) (accelerating voltage 15-20kV, working distance 10-15mm). Micro-area composition analysis is performed using energy dispersive spectroscopy (EDS) (sampling area ≥10μm×10μm), and grain orientation and grain boundary characteristics are analyzed using electron backscatter diffraction (EBSD). Key parameters included corrosion time control (5-15s, adjusted according to the clarity of the microstructure), SEM accelerating voltage (15-20kV), EDS energy dispersive spectroscopy acquisition time (≥60s / point), and EBSD scan step size (0.1-0.5μm). At least five fields of view were observed for each sample, and representative photographs were taken. Data processing included measuring the equivalent weld layer thickness, statistically analyzing grain size distribution, analyzing the distribution curves of Si and B elements along the interface, and identifying the presence of brittle phases (such as borides and silicides).

[0078] Experiment 5: Characterization of Amorphous Structure and Thermal Stability Analysis of Foil Materials The test object was an amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil. The purpose of the test was to verify the amorphous structural characteristics of the foil, determine the glass transition temperature (Tg) and crystallization temperature (Tx), and evaluate its thermal stability. The test principle was based on the diffuse peak characteristics of X-ray diffraction of amorphous alloys and the glass transition and crystallization exothermic peaks determined by differential scanning calorimetry (DSC). The experimental methods included X-ray diffraction (XRD) analysis using Cu Kα radiation (λ=0.15418nm), a scanning range of 10-90° (2θ), a step size of 0.02°, and a scanning rate of 5° / min. The judgment criterion was the absence of indistinguishable crystalline diffraction peaks in the diffraction pattern and the presence of only broadened diffuse peaks located at 40-50°. Differential scanning calorimetry (DSC) was performed under argon protection, heating from room temperature to 700°C at a heating rate of 10°C / min, and recording the heat flow curve. The glass transition temperature (Tg) was taken as the midpoint temperature of the step transition, and the crystallization temperature (Tx) was taken as the peak temperature of the crystallization exothermic peak. Key parameters included XRD source stability, DSC heating rate accuracy (±0.5℃ / min), argon flow rate (50mL / min), and sample mass (8-12mg). At least three samples were prepared for each foil material for repeated testing. Data processing included calibrating the XRD diffuse peak positions and half-width at half-maximum (HWHM), calculating the width of the supercooled liquid phase region ΔTx = Tx - Tg (≥50℃ indicates good thermal stability), and analyzing the glass-forming ability of foils with different compositions.

[0079] Experiment 6: Distribution and Segregation Analysis of Interface Elements in the Joint Region The test object was a micro-area sample at the butt joint interface of the weld. The purpose of the test was to quantitatively analyze the concentration distribution gradient and segregation degree of key elements such as Si and B along the diffusion interface of the weld. The test principle is based on the high spatial resolution elemental quantitative analysis capability of electron probe microanalysis (EPMA) or secondary ion mass spectrometry (SIMS). The experimental method was to prepare a polished sample of the weld joint cross section (surface roughness Ra≤0.05μm). The elemental concentration distribution was measured along the direction perpendicular to the weld using either EPMA online scanning mode (accelerating voltage 15kV, beam current 20nA, beam spot diameter 1μm, scan step size 2μm) or SIMS depth profiling mode (primary ion beam Cs⁺, energy 5keV, beam current 30nA, sputtering rate 0.5nm / s). The scan length covered the complete area from the base material to the diffusion layer to the central region and back to the base material (total length ≥500μm). Key parameters included EPMA standard sample calibration, SIMS quality resolution (M / ΔM≥300), depth resolution (≤5nm), and detection elements including Ni, Cr, Fe, Si, and B, with at least three parallel line scans performed for each sample. Data processing included plotting concentration-distance distribution curves for each element, calculating the segregation coefficients K=Cinterface / Cbase for Si and B, assessing the existence of enrichment zones with concentrations exceeding twice that of the base material, and performing correlation analysis with brittle phase precipitation locations.

[0080] Figure 1 The XRD images show the amorphous structures of Example 1 and Comparative Example 8. The basic parameters are: X-ray diffraction characterization using Cu Kα radiation with a scanning range of 10 to 90 degrees and a 2θ step of 0.02 degrees; and the variable parameters are: sample type (intermediate layer foil of Example 1 and crystalline foil of Comparative Example 8). The conclusion is that Example 1 only shows broadened diffuse peaks around 40 to 50 degrees with no indistinguishable sharp diffraction peaks, while Comparative Example 8 shows obvious sharp diffraction peaks. This proves that Example 1 obtains a stable amorphous structure, thus possessing a more uniform microstructure and process stability.

[0081] Figure 2 The DSC glass transition and crystallization behavior diagrams for Examples 1, 3, and Comparative Example 3 are shown. The basic parameters are the heat flow curves recorded by differential scanning calorimetry at an inert atmosphere with a temperature increase of 10 degrees Celsius per minute from room temperature to 700 degrees Celsius. The variable parameters are the alloy system and the thermal stability window parameters. Example 1: Tg approximately 500 degrees Celsius, Tx approximately 560 degrees Celsius; Example 3: Tg approximately 570 degrees Celsius, Tx approximately 655 degrees Celsius; Comparative Example 3: Tg approximately 430 degrees Celsius, Tx approximately 470 degrees Celsius. The conclusion is that Examples 1 and 3 have higher Tg and Tx and a larger ΔTx, while Comparative Example 3 has a narrower thermal stability window. This proves that the composition design of this scheme can improve the thermal stability of the amorphous phase and reduce the risk of unstable crystallization during welding heating.

[0082] Figure 3 The images show the SEM-EDS line scan Si distribution along the weld interface of Comparative Examples 4 and 6 in Example 1. The basic parameters are the line scan distance range of approximately -100 to +100 micrometers along the interface direction using scanning electron microscopy energy dispersive spectroscopy, and the variation of the output Si signal with distance. The variable parameters are the sample systems of Example 1, high-silicon Comparative Example 4, and low-temperature welded Comparative Example 6. The conclusion is that the Si distribution in Example 1 is gentle with limited peak values, while Comparative Example 4 shows a significant enrichment peak at the center of the interface, and Comparative Example 6 exhibits a steeper gradient and local enrichment. This proves that the proposed method can suppress Si segregation and promote the homogenization of the interface composition, thereby reducing the tendency for brittle phases to concentrate and precipitate.

[0083] Figure 4 The images show the SEM-EDS line scan distribution of B along the weld interface for Comparative Examples 5 and 6 (Example 1). The basic parameters are the line scan distance range of approximately -100 to +100 micrometers along the interface direction, and the variation of the output B signal with distance. The variable parameters are the sample systems of Example 1, High-Boron Comparative Example 5, and Low-Temperature Welding Comparative Example 6. The conclusion is that the B signal in Example 1 has small fluctuations and no sharp enrichment peaks, while Comparative Example 5 shows obvious central enrichment, and Comparative Example 6 shows central enrichment due to insufficient diffusion. This proves that the proposed method can reduce the segregation of B at the interface, thereby reducing the risk of interface embrittlement caused by brittle precipitation such as borides.

[0084] Figure 5 The images show the Si distribution along the vertical weld direction obtained by EPMA or SIMS depth profiling of Example 1 and Comparative Example 4. The basic parameters are: electron probe or secondary ion mass spectrometry is used to perform depth or cross-sectional line profiling along the vertical weld direction with a total length of not less than 500 micrometers to obtain the Si content variation with position. The variable parameters are: sample type Example 1 and high-silicon comparative example 4. The conclusion is that Example 1 maintains small fluctuations on a wide scale and has no narrow peaks that significantly increase more than the base material, while Comparative Example 4 shows narrow peaks that are enriched several times and concentrated in the center region of the weld. This proves that this method can also achieve uniform diffusion of Si and controllable composition gradient at a higher spatial resolution scale, thereby supporting the consistency of weld microstructure.

[0085] Figure 6 The images show the distribution of boron (B) along the vertical weld direction using EPMA or SIMS depth profiling for Example 1 and Comparative Example 5. The basic parameters are: electron probe microanalysis or secondary ion mass spectrometry is performed along the vertical weld direction with a total depth or cross-sectional line analysis length of not less than 500 micrometers to obtain the change of B content with position. The variable parameters are: sample type Example 1 and high boron Comparative Example 5. The conclusion is that B is evenly distributed in Example 1 with only mild fluctuations, while Comparative Example 5 shows a sharp enrichment peak at the center with a narrower peak width. This proves that the proposed method can control the diffusion and segregation behavior of B and reduce the formation of embrittled phases and crack-sensitive areas in local high-concentration regions from the source.

[0086] Figure 7This is a macroscopic optical photograph of the nickel-based alloy welded structure of Example 1. The basic parameters are: both the first and second nickel-based alloy components are made of GH4169 material, and the weld joint area is formed by transient liquid phase diffusion welding. The variable parameters are: the thickness of the amorphous nickel-chromium-iron-silicon-boron alloy intermediate foil is 40 μm and its thickness fluctuation is ±10%; the welding temperature is 1075℃; the welding pressure is 10 MPa; the holding time is 5 h; the vacuum degree is 25 Pa; the cooling rate is 5℃ / min; and the subsequent solution heat treatment is 1025℃ for 1.2 h and the aging heat treatment is 725℃ for 9 h. Macroscopically, the joint area has a continuous, dense, and integrated appearance without obvious through-defect characteristics and a leakage rate of 5×10⁻. 8 The results show that the process chain is consistent with the Pa·m³ / s, indicating that it can achieve stable metallurgical connection on a macroscopic scale and meet the requirements of density and stability of welded structures for supercritical diffusers at 650℃, thus proving that the selection of scheme parameters is reasonable.

[0087] Figure 8 The image shown is a scanning electron microscope (SEM) image of the weld joint area in Example 1. The basic parameters are that the butt joint interface is formed by instantaneous liquid phase diffusion welding of an amorphous nickel-chromium-iron-silicon-boron alloy intermediate foil with an equivalent weld layer thickness of 0.25 mm. The variable parameters are that the surface roughness Ra of the butt joint before welding is 2.0 μm, the intermediate foil completely covers the area to be welded with a single layer, the degree of diffusion and isothermal solidification caused by the welding temperature of 1075℃ and the holding time of 5 h, and the effect of 10 MPa pressure on interface bonding and porosity suppression. The SEM cross-section shows that the metallurgical bonding zone has a continuous structure and exhibits structural differences between the base material area and the weld joint area, while no continuous unwelded gaps or through-holes are observed. The conclusion is that the measured visualization of the equivalent weld layer thickness and the dense and continuous microscopic evidence of the joint area jointly prove that instantaneous liquid phase diffusion welding can achieve stable and repeatable connection quality under this combination of temperature, pressure and time, supporting the rationality of the process window of this scheme.

[0088] Figure 9 The image shows a transmission electron microscope (TEM) image of the weld joint area in Example 1. The basic parameters are: the weld joint area was instantaneously liquid-phase diffusion welded at 1075℃, followed by solution heat treatment at 1025℃ and aging heat treatment at 725℃. The variable parameters are: the interdiffusion and precipitation behavior of the elements introduced by the composition of the interlayer foil (60wt% nickel, 15wt% chromium, 15wt% iron, 7wt% silicon, and 3wt% boron), and the regulation of the growth of the nucleation site of the nano-reinforced precipitated phase by the aging process. Figure 9 Image a is a bright-field transmission electron microscope (TEM) image of the GH4169 / GH4169 connector, showing the diffusely distributed nano-precipitates in the γ matrix. Disc-shaped γ″ and spherical γ′ phases were observed, proving that the aging treatment successfully induced the precipitation of the strengthening phase. Figure 9b is a magnified bright-field transmission electron microscope image of the diffusion-affected region of the GH4169 / GH4169 joint, showing micron-sized second-phase particles, such as borides or carbides, near the grain boundary, indicating the segregation and reaction of elements at the grain boundary during diffusion. Figure 9 c is a high-resolution transmission electron microscope image of the GH4169 / GH4169 connector, which clearly shows the lattice fringes of the γ matrix and the γ″ precipitate. The measured interplanar spacing is consistent with the theoretical value, confirming the structure of the precipitate and its coherent relationship with the matrix. Figure 9 d is the selected area electron diffraction pattern of the GH4169 / GH4169 connector, showing diffraction spots dominated by the FCC γ phase, accompanied by superlattice reflections of γ″ and γ′, further confirming the existence of the strengthening phase and its crystallographic characteristics.

[0089] As can be seen from the performance of the examples and comparative examples in Table 1, the welded joints of Examples 1-4 are significantly superior to all comparative examples in terms of mechanical properties such as room temperature tensile strength, 650℃ high-temperature tensile strength, 650℃ creep strength, and elongation. Among them, Example 3 exhibits the best high-temperature mechanical properties due to the use of a high-nickel, low-iron formula and a high welding temperature and long-term heat preservation process, with a room temperature tensile strength of 948 MPa, a 650℃ tensile strength of 705 MPa, and a 650℃ creep strength of 445 MPa. Example 4 achieves an ultra-low leakage rate of 3×10⁻⁻⁻⁶ due to the use of ultra-thin foil and rapid welding process. 9 It exhibits excellent airtightness at Pa·m³ / s. Comparative Examples 1 and 2, due to foil thickness deviating from the optimized range, resulted in uneven joint structure and incomplete interface filling, leading to room temperature strengths of only 685-755 MPa and a leakage rate deterioration to 10⁻⁻⁶. 6 -10⁻ 5 In Comparative Example 3, the excessively high levels of multiple elements led to a decrease in the alloy's amorphous forming ability and a deterioration in its weldability. In Comparative Examples 4 and 5, the excessively high silicon-boron content resulted in a large amount of brittle phase precipitation, causing an abnormal increase in joint hardness to 385-405 HV, but a sharp decrease in elongation to 3.2-4.5% and a deterioration in leakage rate to 10⁻. 4 The magnitudes of the defects are as follows: Comparative Examples 6 and 7 show that insufficient diffusion due to excessively low welding temperature and pressure resulted in a comprehensive decline in the mechanical and sealing properties of the joints. Comparative Example 8, due to the use of crystalline foil, exhibited significantly inferior joint performance compared to the example using amorphous foil, resulting in reduced wettability and fluidity. Experimental results demonstrate that this invention, through compositional optimization of amorphous nickel-chromium-iron-silicon-boron alloy foil and precise control of instantaneous liquid-phase diffusion welding process parameters, successfully achieved synergistic optimization of "high-temperature strength / creep performance" and "ultra-low leakage rate and airtightness," while effectively controlling Si / B segregation and brittle phase precipitation. This provides a reliable joining technology solution for nickel-based alloy welding structures in 650℃ supercritical diffusers.

[0090] Table 1 Performance Comparison Summary Table Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A nickel-based alloy welded structure for a 650℃ supercritical diffuser, characterized in that, It includes a first nickel-based alloy component and a second nickel-based alloy component, wherein the first nickel-based alloy component and the second nickel-based alloy component are formed into a weld joint area by transient liquid phase diffusion welding; The welded joint area is formed at the interface between the two components by instantaneous liquid phase diffusion welding of an amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil, the thickness of which is 20-60μm. The amorphous structure of the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil was determined by X-ray diffraction. The determination criterion was that there were no indistinguishable crystal diffraction peaks in the X-ray diffraction pattern and only diffuse peaks were present. The amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil contains nickel, chromium, iron, silicon and boron by mass fraction, wherein the mass fraction of chromium is 5-25 wt%, the mass fraction of iron is 0-30 wt%, the mass fraction of silicon is 1-8 wt%, the mass fraction of boron is 0.5-4 wt%, and the balance is nickel, wherein the mass fraction of nickel is 45-75 wt%, and the sum of the mass fractions of all elements except unavoidable impurities is 100 wt%.

2. The nickel-based alloy welded structure as described in claim 1, characterized in that, The amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil is obtained by a strip spinning process from a master alloy prepared through the following steps: A1. Raw material preparation: Weigh nickel, chromium, iron, silicon, and boron to make the mass fraction of chromium in the prepared master alloy 5-25 wt%, iron 0-30 wt%, silicon 1-8 wt%, boron 0.5-4 wt%, with the balance being nickel, which has a mass fraction of 45-75 wt%, and the sum of the mass fractions of all elements, excluding unavoidable impurities, is 100 wt%. A2. Melting: Melting is carried out under vacuum conditions with a pressure of 1-50 Pa, so that the temperature of the melt reaches 1400-1550℃ and is held for 5-30 min. Then, a protective gas is introduced and the master alloy is obtained by casting under a protective atmosphere, wherein the protective atmosphere is argon or nitrogen. A3. Master alloy inspection: Inspect whether the chemical composition of the master alloy meets the mass fraction requirements of step A1. Master alloys that meet the requirements are used as raw materials for subsequent strip spinning.

3. The nickel-based alloy welded structure as described in claim 2, characterized in that, The master alloy is prepared into the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil by the following steps: B1. Strip casting: After the master alloy is heated to 1350-1550℃ to form a melt, it is sprayed onto the surface of a rotating cooling wheel through a nozzle with an inner diameter of 0.5-2.0mm. The gap between the nozzle outlet and the surface of the rotating cooling wheel is 0.2-1.0mm. The strip is formed under an argon protective atmosphere. B2. Process parameters: The linear velocity of the cooling wheel is 20-50 m / s, and the pressure of the jet driving gas is 0.05-0.30 MPa; B3. Forming: Obtaining a strip with a thickness of 20-60μm and a width of 5-50mm, wherein the strip is the amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil.

4. The nickel-based alloy welded structure as described in claim 3, characterized in that, The post-processing of the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil includes: C1. Cutting: Cut the strip into foil segments with a length of 10-500mm; C2. Packaging: Sealed packaging under vacuum conditions of 1-50 Pa or under a protective atmosphere; C3. Quality control: The thickness fluctuation of the intermediate foil is controlled within ±10%.

5. The nickel-based alloy welded structure as described in claim 1, characterized in that, The instantaneous liquid phase diffusion welding is performed at a welding temperature of 1000-1150℃, a welding pressure of 2-20MPa, a holding time of 1-10h, and in a vacuum environment at a pressure of 1-50Pa or in a protective atmosphere. The welding temperature is higher than the solidus temperature of the amorphous nickel-chromium-iron-silicon-boron alloy interlayer foil and lower than the solidus temperatures of the first nickel-based alloy component and the second nickel-based alloy component.

6. The nickel-based alloy welded structure as described in claim 1, characterized in that, The material grade of the first nickel-based alloy component is selected from GH4169 or Inconel718; the material grade of the second nickel-based alloy component is selected from GH4169 or Inconel718; before welding, the surface roughness Ra of the mating surfaces of the two components is 0.8-3.2μm, and the surface roughness Ra of the mating surfaces is measured by a stylus-type surface roughness tester under the following conditions: sampling length 0.8mm and evaluation length 4.0mm; The equivalent weld layer thickness along the butt joint normal in the weld joint area is 0.05-0.50 mm, and the method for determining the equivalent weld layer thickness is as follows: The width of the metallurgical bonding zone was measured along the normal direction of the weld joint area on a metallographic microscope or scanning electron microscope image after the cross-sectional sample of the weld joint area at the butt joint was ground, polished, and etched; the leakage rate of the weld joint area was 1×10⁻ 9 -1×10⁻ 6 Pa·m³ / s, and the leakage rate is determined by helium mass spectrometry leak detection method, and the determination conditions are test temperature 20-25℃, pressure difference across the specimen 0.10-0.20MPa, and detection time 60-300s.

7. A method for preparing a nickel-based alloy welded structure for a 650℃ supercritical diffuser as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Provide a first nickel-based alloy component and a second nickel-based alloy component; S2. The amorphous nickel-chromium-iron-silicon-boron alloy intermediate layer foil is placed in a single layer at the interface between the two components, and the intermediate layer foil completely covers the area to be welded at the interface. S3. Under vacuum conditions with a pressure of 1-50 Pa or under protective atmosphere conditions, apply welding pressure to the two components and heat them to the welding temperature to perform instantaneous liquid phase diffusion welding, wherein the welding temperature is 1000-1150℃, the welding pressure is 2-20 MPa, the holding time is 1-10 h, and the welding pressure is maintained continuously during the process of heating to the welding temperature and throughout the holding time. S4. Cool to room temperature (20-25℃) to obtain a nickel-based alloy welded structure.

8. The method as described in claim 7, characterized in that, The protective atmosphere in step S3 is argon or nitrogen.

9. The method as described in claim 7, characterized in that, Step S4 is followed by a heat treatment step S5, which includes solution heat treatment and aging heat treatment. The solution heat treatment is performed at a temperature of 950-1100℃ for a duration of 0.5-2.0 h, and the aging heat treatment is performed at a temperature of 650-800℃ for a duration of 2-16 h.

10. The method as described in claim 7, characterized in that, The heating rate in step S3 is 2-20℃ / min, and the cooling rate in step S4 is 0.5-10℃ / min.

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