An accident tolerant nuclear fuel cladding coating and its preparation method and application

Abstract

The application discloses an accident-tolerant nuclear fuel cladding coating and a preparation method and application thereof, and belongs to the technical field of nuclear fuel cladding coating. The coating is a Cr-based binary alloy coating deposited on the surface of a zirconium alloy base, and is selected from Cr-Fe, Cr-V or Cr-Mo alloy coatings, wherein the content of Fe is 3-10 wt%, the content of V is 3-20 wt%, and the content of Mo is 1-5 wt%. The preparation method adopts a magnetron sputtering process, and is realized by controlling parameters such as vacuum degree, temperature, gas pressure, bias voltage and power. Through alloying, the application effectively inhibits the element interdiffusion between the coating and the zirconium alloy base at high temperature, reduces the formation of brittle intermetallic compounds and Kirkendall holes, significantly improves the thermal stability and service life of the coating under accident conditions, meanwhile, the process is mature, the coating quality is high, and the coating is suitable for surface protection of zirconium alloy fuel cladding of nuclear power stations.

Description

Technical Field

[0001] This invention relates to the field of nuclear fuel cladding coating technology, specifically to a chromium-based binary alloy coating for improving the safety of zirconium alloy cladding under accident conditions, a method for preparing the coating, and its application in nuclear reactor fuel cladding protection. Background Technology

[0002] Zirconium alloys (such as Zr-4 and Zr-2) are widely used as fuel cladding materials for water-cooled nuclear reactors due to their excellent neutron economy and good corrosion resistance. However, under extreme high-temperature steam conditions such as loss-of-coolant accidents (LOCA), exposed zirconium alloys can undergo violent zirconium-water reactions with steam, producing large amounts of hydrogen gas and exothermic reactions, posing a serious risk of hydrogen explosion and radioactive material leakage. To improve the inherent safety of reactors, accident-resistant fuel (ATF) systems have become an important research direction in the international nuclear energy field. Among these, applying a high-performance protective coating to the surface of existing mature zirconium alloy cladding is recognized as a promising and rapidly deployable technology.

[0003] Among numerous candidate coating materials, metallic chromium (Cr) stands out as one of the most promising ATF coating materials due to its high melting point, excellent high-temperature oxidation resistance, good corrosion resistance, and a thermal expansion coefficient similar to that of zirconium alloys. Extensive off-pile performance studies and preliminary in-pile tests have been conducted. However, pure Cr coatings still face two key technical bottlenecks in practical applications: First, under high-temperature service or accident conditions (especially above 860°C when zirconium alloys undergo α→β phase transformation), intense interdiffusion occurs between Cr and Zr atoms. This not only leads to the formation of brittle intermetallic compounds (mainly the ZrCr2Laves phase) at the interface but also triggers a significant Kirkendall effect due to the different diffusion rates of Cr and Zr, generating numerous voids in the interface region. These brittle phases and voids severely compromise the metallurgical bond integrity between the coating and the substrate, causing the coating to easily crack and peel off under thermal or mechanical stress, thus losing its protective function. Secondly, under the intense irradiation environment of a reactor, pure Cr tends to undergo irradiation swelling, generating vacancy-type defect clusters, while the zirconium alloy matrix exhibits different irradiation deformation behavior. This mismatch in irradiation response introduces additional internal stress at the coating / substrate interface, potentially exacerbating interfacial instability.

[0004] To address these issues, researchers have explored various methods, with microalloying considered an effective strategy. However, existing research largely focuses on the effects of single alloying elements under specific conditions, lacking systematic studies on alloy composition design, screening, and optimization aimed at the synergistic goals of "suppressing high-temperature interdiffusion" and "enhancing radiation resistance potential." Furthermore, the development of a precise, dense alloy coating with good bonding to the zirconium alloy matrix using an efficient, stable, and engineerable fabrication process remains crucial. Therefore, developing a chromium-based alloy coating with well-defined composition, reliable fabrication process, and the ability to comprehensively improve interfacial stability and service performance is of great significance for promoting the practical application of accident-resistant fuel cladding technology. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing pure chromium coatings, such as severe interdiffusion with zirconium alloy substrates at high temperatures, easy formation of brittle phases and pores at the interface, and the need to improve radiation resistance. It provides a novel accident-resistant nuclear fuel cladding coating, its preparation method, and its application.

[0006] To solve the above-mentioned technical problems, the technical solution proposed in this application is as follows:

[0007] This invention provides an accident-resistant nuclear fuel cladding coating, wherein the coating is a Cr-based binary alloy coating deposited on the surface of a zirconium alloy substrate. The binary alloy coating is selected from Cr-Fe alloy coating, Cr-V alloy coating, or Cr-Mo alloy coating. In the Cr-Fe alloy coating, the mass percentage of iron is 3wt% to 10wt%, with the balance being chromium; in the Cr-V alloy coating, the mass percentage of vanadium is 3wt% to 20wt%, with the balance being chromium; and in the Cr-Mo alloy coating, the mass percentage of molybdenum is 1wt% to 5wt%, with the balance being chromium.

[0008] Furthermore, the Cr-Fe alloy coating contains 7 wt% iron by mass; the Cr-V alloy coating contains 7 wt% vanadium by mass; and the Cr-Mo alloy coating contains 3 wt% molybdenum by mass.

[0009] On the other hand, this application also claims protection for a method for preparing an accident-resistant nuclear fuel cladding coating, which is used to prepare the above-mentioned coating and employs a magnetron sputtering process, including the following steps: Step A: Pre-treat the surface of the zirconium alloy substrate and fix it on the sample stage; Step B: Evacuate the vacuum chamber to a high vacuum, heat it to 150℃~250℃ and maintain the temperature, continue evacuating to achieve a background vacuum of 3×10⁻⁶. - Below ³ Pa; Step C: Introduce argon gas into the vacuum chamber until the working pressure is 0.3 Pa ~ 1.5 Pa, turn on the power to ignite, and then adjust the argon gas flow rate to stabilize the working pressure at 0.3 Pa ~ 0.8 Pa; Step D: Under the conditions of applying a bias voltage to the substrate and applying sputtering power, sputtering deposition is performed to form the Cr-based binary alloy coating on the surface of the zirconium alloy substrate.

[0010] Furthermore, in step B, the high vacuum degree is 4 × 10⁻⁶. - The heating temperature is 200°C when the pressure is below 3 Pa.

[0011] Furthermore, in step C, argon gas is introduced during ignition to bring the pressure to 1.0 Pa, and after ignition, the argon gas flow rate is adjusted to stabilize the deposition working pressure at 0.5 Pa.

[0012] Furthermore, in step D, the substrate bias voltage is -50V and the sputtering power is 300W.

[0013] Furthermore, the power supply used for the sputtering deposition is a DC power supply or a radio frequency power supply.

[0014] Furthermore, after the sputtering deposition step, a vacuum annealing step is included for the coated zirconium alloy substrate, the vacuum annealing including holding at a temperature of 700°C to 860°C, or holding at a temperature of 860°C to 1200°C.

[0015] On the other hand, this application also claims protection for a zirconium alloy component having the aforementioned accident-resistant nuclear fuel cladding coating on at least one of its surfaces.

[0016] Furthermore, the zirconium alloy component is a nuclear reactor fuel cladding tube or core structural component.

[0017] Compared with the prior art, the present invention achieves the following beneficial technical effects: This application utilizes a specific chromium-based binary alloy coating prepared on the surface of a zirconium alloy. This effectively suppresses the interdiffusion of harmful elements between the coating and the substrate at high temperatures, significantly reduces the formation of brittle intermetallic compounds and Kirkendal voids, thereby greatly improving the thermal stability and service life of the coating under normal and accident conditions. Furthermore, the employed preparation process is mature and yields a high-quality coating with strong adhesion, density, and uniformity, exhibiting significantly superior overall performance compared to traditional pure chromium coatings. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The images show the cross-sectional backscattered electron (BSE) morphology of the original coatings prepared in Examples 1, 4, and 7.

[0020] Figure 2 The image shows the cross-sectional backscattered electron (BSE) morphology of the original coating prepared for Comparative Example 1.

[0021] Figure 3 Comparison of cross-sectional BSE morphology and EDS surface and line scan data of the coating samples of Comparative Example 1, Example 4, and Example 7 after vacuum annealing at 800°C for 6 hours.

[0022] Figure 4 The image shows the cross-sectional BSE morphology and EDS surface scan and line scan element distribution of the coating samples of Comparative Example 1, Example 1, Example 4 and Example 7 after vacuum annealing at 1200℃ for 0.5 hours. Detailed Implementation

[0023] 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. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention protects a Cr-based binary alloy coating deposited on the surface of a zirconium alloy substrate, which is selected from Cr-Fe, Cr-V, or Cr-Mo alloy coatings. The composition ranges of the three binary alloy coatings, Cr-Fe, Cr-V, and Cr-Mo, are as follows: Cr-Fe coating (Fe: 3wt%-10wt%): When the Fe content reaches about 3wt%, it can be effectively dissolved in Cr and begins to significantly participate in the interfacial reaction, improving the structure and stability of the interfacial products. The upper limit of the content is set at 10wt% to ensure excellent diffusion inhibition while avoiding adverse effects on the coating's basic properties such as corrosion resistance due to excessive Fe content.

[0025] Cr-V coating (V: 3wt%-20wt%): When the V content is 3wt% or higher, it can effectively pin grain boundaries and hinder atomic diffusion channels through solid solution strengthening effect; V and Cr are infinitely miscible, but excessively high V content (>20wt%) will significantly change the physical and chemical properties of the material, so 20wt% is taken as a reasonable upper limit.

[0026] Cr-Mo coating (Mo: 1wt%-5wt%): Mo atoms are relatively large, and adding a small amount (≥1wt%) can cause significant lattice distortion, thereby effectively hindering atomic diffusion; setting the upper limit of content to 5wt% is to control the brittleness risk that may be caused by the increase of Mo content while obtaining good interfacial stability.

[0027] The following examples will demonstrate that implementing the present invention within the above-described scope can achieve technical effects superior to those of pure Cr coatings.

[0028] (I) Examples of Cr-Fe alloy coatings Example 1: Cr-7Fe (meaning Fe content is 7wt%, the same below) coating The steps for preparing a Cr-7Fe coating on the surface of Zr4 alloy are as follows: 1. A Zr4 alloy target (10mm × 5mm × 2mm) was selected as the substrate. The surface was successively polished with 600, 1000, 1500, 2000, and 3000 grit sandpaper. Mechanical polishing was performed using W3.5 water-based diamond polishing paste. The substrate was then ultrasonically cleaned twice with anhydrous ethanol for 10 minutes each time. After drying, conductive adhesive was used to fix it to the sample plate. A Cr-7Fe alloy target (Ø76.2mm × 5mm) was installed on the target mounting station, and the sample plate was placed 10cm away from the target.

[0029] 2. Turn on the mechanical pump to evacuate to a low vacuum level of 5 Pa in the chamber, then turn on the molecular pump to perform high vacuum evacuation until the vacuum level reaches 4 × 10⁻⁶ Pa. - After reaching 3Pa, the heating system is turned on, and the vacuum chamber is heated to 200℃ and then held at that temperature. After the gas expands due to heat, the vacuum is continuously evacuated until the vacuum level is less than 3×10. - ³Pa.

[0030] 3. Maintain the operating temperature at 200℃, introduce argon gas into the vacuum chamber until the vacuum level reaches 1.0 Pa, set the substrate bias voltage to -50V, and set the RF power supply to 300W for ignition. After successful ignition, reduce the argon gas flow rate to the operating pressure of 0.5 Pa. The deposition time is 13 hours. After deposition, turn off the bias power supply, stop the argon gas supply, and shut down the heating system. Allow the vacuum chamber to cool to below 80℃, then open the furnace and remove the sample. A Cr-7Fe coating with a thickness of 8.9 μm is obtained. See [link to relevant documentation]. Figure 1 .

[0031] Example 2: Cr-3Fe coating The steps for preparing a Cr-3Fe coating on the surface of Zr4 alloy are as follows: The only difference between this embodiment and Example 1 is that a Cr-3Fe alloy target (Fe content of 3wt%) is used, the deposition time is adjusted to 12 hours, and a Cr-3Fe coating with a thickness of approximately 8.5 μm is obtained.

[0032] Example 3: Cr-10Fe coating The steps for preparing a Cr-10Fe coating on the surface of Zr4 alloy are as follows: The only difference between this embodiment and Example 1 is that a Cr-10Fe alloy target (Fe content of 10wt%) is used, the deposition time is adjusted to 13.5 hours, and a Cr-10Fe coating with a thickness of approximately 9.1 μm is obtained.

[0033] (II) Examples of Cr-V alloy coating Example 4: Cr-7V coating The steps for preparing a Cr-7V coating on the surface of Zr4 alloy are as follows: 1. A Zr4 alloy target (10mm × 5mm × 2mm) was selected as the substrate. The surface was successively polished with 600, 1000, 1500, 2000, and 3000 grit sandpaper. Mechanical polishing was then performed using W3.5 water-based diamond polishing paste. The substrate was ultrasonically cleaned twice with anhydrous ethanol for 10 minutes each time. After drying, conductive adhesive was used to fix it to the sample plate. A Cr-7V alloy target (Ø76.2mm × 5mm) was installed on the target mounting station, with the sample plate placed 10cm away from the target.

[0034] 2. Turn on the mechanical pump to evacuate to a low vacuum level of 5 Pa in the chamber, then turn on the molecular pump to perform high vacuum evacuation until the vacuum level reaches 4 × 10⁻⁶ Pa. - After reaching 3Pa, the heating system is turned on, and the vacuum chamber is heated to 200℃ and then held at that temperature. After the gas expands due to heat, the vacuum is continuously evacuated until the vacuum level is less than 3×10. - ³Pa.

[0035] 3. Maintain the operating temperature at 200℃, introduce argon gas into the vacuum chamber until the vacuum level reaches 1.0 Pa, set the substrate bias voltage to -50V, and set the RF power supply to 300W for ignition. After successful ignition, reduce the argon gas flow rate to the operating pressure of 0.5 Pa. The deposition time is 8 hours and 40 minutes. After deposition, turn off the bias power supply, stop the argon gas supply, and shut down the heating system. Allow the vacuum chamber to cool to below 80℃, then open the furnace and remove the sample. A Cr-7V coating with a thickness of 8.9 μm is obtained. See [link to relevant documentation]. Figure 1 .

[0036] Example 5: Cr-3V coating The steps for preparing a Cr-3V coating on the surface of Zr4 alloy are as follows: The only difference between this embodiment and Example 4 is that a Cr-3V alloy target (V content of 3wt%) is used, and the deposition time is adjusted to 8 hours to obtain a Cr-3V coating with a thickness of approximately 8.0 μm.

[0037] Example 6: Cr-20V coating The steps for preparing a Cr-20V coating on the surface of Zr4 alloy are as follows: The only difference between this embodiment and Example 4 is that a Cr-20V alloy target (V content of 20wt%) is used, the deposition time is adjusted to 9.5 hours, and a Cr-20V coating with a thickness of approximately 9.3μm is obtained.

[0038] (III) Examples of Cr-Mo alloy coatings Example 7: Cr-3Mo coating The steps for preparing a Cr-3Mo coating on the surface of Zr4 alloy are as follows: 1. A Zr4 alloy target (10mm × 5mm × 2mm) was selected as the substrate. The surface was successively polished with 600, 1000, 1500, 2000, and 3000 grit sandpaper. Mechanical polishing was then performed using W3.5 water-based diamond polishing paste. The substrate was ultrasonically cleaned twice with anhydrous ethanol for 10 minutes each time. After drying, conductive adhesive was used to fix it to the sample plate. A Cr-3Mo alloy target (Ø76.2mm × 5mm) was installed in the target mounting position, with the sample plate placed 10cm away from the target.

[0039] 2. Turn on the mechanical pump to evacuate to a low vacuum level of 5 Pa in the chamber, then turn on the molecular pump to perform high vacuum evacuation until the vacuum level reaches 4 × 10⁻⁶ Pa. - After reaching 3Pa, the heating system is turned on, and the vacuum chamber is heated to 200℃ and then held at that temperature. After the gas expands due to heat, the vacuum is continuously evacuated until the vacuum level is less than 3×10. - ³Pa.

[0040] 3. Maintain the operating temperature at 200℃, introduce argon gas into the vacuum chamber until the vacuum level reaches 1.0 Pa, set the substrate bias voltage to -50V, and set the RF power supply to 300W for ignition. After successful ignition, reduce the argon gas flow rate to the operating pressure of 0.5 Pa. The deposition time is 8 hours and 40 minutes. After deposition, turn off the bias power supply, stop the argon gas supply, and shut down the heating system. Allow the vacuum chamber to cool to below 80℃, then open the furnace and remove the sample. A Cr-3Mo coating with a thickness of 7.8 μm is obtained. See [link to relevant documentation]. Figure 1 .

[0041] Example 8: Cr-1Mo coating The steps for preparing a Cr-1Mo coating on the surface of Zr4 alloy are as follows: The only difference between this embodiment and Example 7 is that a Cr-1Mo alloy target (Mo content of 1wt%) is used, the deposition time is adjusted to 8 hours, and a Cr-1Mo coating with a thickness of approximately 7.3 μm is obtained.

[0042] Example 9: Cr-5Mo coating The steps for preparing a Cr-5Mo coating on the surface of Zr4 alloy are as follows: The only difference between this embodiment and Embodiment 7 is that a Cr-5Mo alloy target (Mo content of 5wt%) is used, and the deposition time is adjusted to 9 hours to obtain a Cr-5Mo coating with a thickness of approximately 8.2μm.

[0043] (iv) Comparative Example Comparative Example 1: Pure Cr Coating Compared to the examples, the magnetron sputtering conditions in this comparative example are similar, except that a Cr target with a purity of 99.95% is selected as the sputtering target material. The operation steps for preparing the Cr coating are as follows: 1. A Zr4 alloy was selected as the substrate, with dimensions of 10mm × 5mm × 2mm. The substrate surface was successively polished with 600-grit, 1000-grit, 1500-grit, 2000-grit, and 3000-grit sandpaper. Mechanical polishing was then performed using W3.5 water-based diamond polishing paste. The substrate was ultrasonically cleaned twice with anhydrous ethanol for 10 minutes each time. After drying, conductive adhesive was used to fix it to the sample plate. A Cr target (Ø76.2mm × 5mm) was installed on the target mounting station, and the sample plate was placed 10cm away from the target.

[0044] 2. Turn on the mechanical pump to evacuate to a low vacuum level of 5 Pa in the chamber, then turn on the molecular pump to perform high vacuum evacuation until the vacuum level reaches 4 × 10⁻⁶ Pa. - After reaching 3Pa, the heating system is turned on, and the vacuum chamber is heated to 200℃ and then held at that temperature. After the gas expands due to heat, the vacuum is continuously evacuated until the vacuum level is less than 3×10. - ³Pa.

[0045] 3. Maintain the operating temperature at 200℃, introduce argon gas into the vacuum chamber until the vacuum level reaches 1.0 Pa, set the substrate bias voltage to -50V, and set the RF power supply to 300W for ignition. After successful ignition, reduce the argon gas flow rate to the operating pressure of 0.5 Pa. The deposition time is 8 hours and 40 minutes. After deposition, turn off the bias power supply, stop the argon gas supply, and shut down the heating system. After the vacuum chamber cools to below 80℃, open the furnace and remove the sample to obtain a Cr coating with a thickness of 11.8 μm.

[0046] (V) Coating performance characterization and effect verification The coating samples prepared in Examples 1-9 and Comparative Example 1 were systematically characterized, and all test results strongly demonstrated the excellent performance of the coating of the present invention.

[0047] 1. Characterization of the original coating The cross-sectional morphology of the original coating was observed using a scanning electron microscope (SEM), such as... Figure 1 and Figure 2 As shown, the coatings prepared in Examples 1, 4, and 7, as well as Comparative Example 1, are all dense and uniform, exhibiting good adhesion to the Zr4 alloy substrate without significant defects. The coating thickness matches the design target. Energy dispersive spectroscopy (EDS) analysis confirmed that the coating composition is consistent with the respective target material composition, with no significant segregation.

[0048] 2. Performance after heat treatment at simulated service temperature (α-Zr phase region) The sample was subjected to vacuum annealing at 800℃ for 6 hours to simulate the long-term thermal stability of the coating at higher service temperatures. The cross-sectional morphology after heat treatment is as follows. Figure 3 As shown.

[0049] Comparative Example 1 (pure Cr): A distinct and relatively thick continuous intermetallic compound layer (mainly ZrCr2) was formed at the interface.

[0050] Embodiments 4 and 7 of the present invention: as shown in the corresponding elemental surface distribution / line scan diagram ( Figure 3 As shown in the figure (Fe represents the element contained in the Zr alloy matrix), the width of the intermetallic compound layer at the interface between all alloy coatings and the substrate is significantly thinner than that of the pure Cr coating. This indicates that in the α-Zr phase region, the alloy coating of the present invention can effectively suppress the interdiffusion of Cr and Zr. Quantitative measurements show that the width of the intermetallic compound layer of the alloy coating is reduced by approximately 30%-50% compared to the pure Cr coating.

[0051] 3. Performance after heat treatment under simulated accident conditions (β-Zr phase region) The sample was subjected to vacuum annealing at 1200℃ for 30 minutes to simulate the extreme high-temperature conditions under a LOCA accident. The cross-sectional morphology after heat treatment is as follows. Figure 4 As shown, the results are highly significant.

[0052] Comparative Example 1 (pure Cr): The coating was completely consumed, leaving only a thick, brittle intermetallic compound layer filled with numerous Kirkendal pores at the interface, which had completely lost its protective function.

[0053] Example 1 (Cr-7Fe): Some coating remains, and the number and size of interface pores are smaller than those of pure Cr coating, but the pores are still quite noticeable.

[0054] Example 4 (Cr-7V): Performed the best. For example... Figure 4As shown, after a harsh heat treatment at 1200℃, the Cr-7V coating still retains a dense coating with a thickness of approximately 4.0 μm. The interfacial diffusion layer is very thin, with only a few tiny pores, and no large-scale diffusion of Zr to the outer side of the coating was observed. This indicates that the Cr-V coating possesses extremely excellent high-temperature phase stability and resistance to interdiffusion.

[0055] Example 7 (Cr-3Mo): It also exhibits excellent performance, with the coating remaining intact and very few interface pores, second only to the Cr-V coating.

[0056] 4. Analysis of Element Diffusion Behavior Elemental distribution analysis of the interface region of the heat-treated sample was performed using EDS line scanning. Figure 3 For the Cr-Fe coating, Fe enrichment was observed at the interface, forming a Zr(Cr, Fe)2 phase with Zr and Cr, consistent with the improvement mechanism of existing technologies. For the Cr-V coating, the gradient distribution of V near the interface indicates that it effectively hinders the interdiffusion channels of Cr and Zr atoms. These microscopic compositional analysis results provide mechanistic support for the improved coating performance of this invention.

[0057] Results Summary The experimental characterization of the above system fully demonstrates that: The Cr-Fe (3-10wt% Fe), Cr-V (3-20wt% V), and Cr-Mo (1-5wt% Mo) binary alloy coatings of the present invention can significantly suppress the harmful interdiffusion between the coating and the zirconium alloy substrate at high temperatures throughout the entire composition range, and their performance is significantly better than that of traditional pure Cr coatings.

[0058] Among them, the Cr-V coating system (especially 7wt% V) exhibits the best high-temperature stability, maintaining an intact coating structure and good interfacial bonding even after simulated accident conditions (1200℃), making it an outstanding preferred option.

[0059] The magnetron sputtering preparation method provided by this invention has stable process and good repeatability, and can controllably prepare high-quality alloy coatings that meet performance requirements.

[0060] The coating of this invention can be directly applied to the surface of components such as zirconium alloy fuel cladding tubes in nuclear reactors, providing them with reliable accident resistance protection far exceeding that of existing pure Cr coatings.

[0061] The Cr-Fe, Cr-V, and Cr-Mo binary alloy coatings provided by this invention can significantly inhibit harmful interdiffusion between the coating and the zirconium alloy substrate at high temperatures and improve interfacial stability. The core principle lies in the comprehensive optimization of the coating system from thermodynamic, kinetic, and microstructural levels through the addition of alloying elements. 1. Solid solution strengthening and diffusion channel blocking: The added Fe, V, and Mo elements form substitutional solid solutions in the Cr matrix. Due to differences in atomic size and modulus between these solute atoms and the matrix Cr atoms, lattice distortion occurs, generating an elastic stress field. This stress field effectively pins grain boundaries, hinders dislocation movement, and acts as an energy barrier for the migration of point defects such as vacancies and interstitial atoms. At high temperatures, atomic diffusion (especially Cr diffusion into the Zr matrix and Zr diffusion into the coating) is the essence of the interdiffusion process. The lattice distortion and stress field induced by the alloying elements significantly increase the activation energy of Cr and Zr atomic diffusion and decrease their diffusion coefficients, thereby kinetically slowing down the entire interdiffusion process.

[0062] 2. Regulation of interfacial reactions and suppression of brittle phases: At the Cr / Zr interface, pure Cr coatings tend to rapidly form a continuous intermetallic compound layer dominated by the brittle Laves phase ZrCr2. In this invention, the addition of alloying elements alters the local chemical environment and thermodynamic equilibrium of the interfacial reaction. For example, Fe atoms can partially replace Cr atoms in the ZrCr2 phase, forming the Zr(Cr,Fe)2 phase. V and Mo elements may also dissolve in the formed compound or alter its formation sequence. These fine-tuning of composition and structure helps reduce the intrinsic brittleness of the interfacial reaction products and may refine the compound layer, making it less likely to become a pathway for crack initiation and propagation. Simultaneously, the "dragging" effect of alloying elements on the interfacial reaction kinetics also controls the growth rate of the compound layer, preventing the rapid formation of an excessively thick, brittle layer.

[0063] 3. Mitigation of the Kirkendall effect: One of the key reasons for the failure of pure Cr coatings at high temperatures is the significant Kirkendal effect caused by the mismatch in the interdiffusion rates of Cr and Zr, resulting in voids at the interface (usually on the side with faster diffusion). This invention aims to modulate the atomic diffusion behavior on the coating side (Cr matrix) through alloying. The solid-solution alloying elements, through the aforementioned diffusion-impeding mechanism, can relatively more effectively "hold back" Cr atoms, slowing their outflow rate into the Zr matrix. Simultaneously, some alloying elements may also affect the diffusion of Zr atoms into the coating. This comprehensive modulation of the bidirectional diffusion rates helps to balance the interdiffusion process, thereby significantly reducing the number and size of Kirkendal voids caused by net mass flow imbalance, and maintaining the density and integrity of the interface structure.

[0064] In summary, this invention does not simply involve the mechanical mixing of different metallic elements. Instead, it systematically regulates the solid solution structure, interfacial reactions, and interdiffusion kinetics of the coating at the atomic scale through the careful selection of elements (Fe, V, Mo) and their addition within specific composition ranges. This synergistically achieves the technical effects of suppressing brittle phase growth, reducing diffusion porosity, and enhancing interfacial bonding. The excellent interfacial morphology and elemental distribution results after annealing at 800℃ and 1200℃ shown in Examples 1-9 are a direct manifestation of the above principles being verified in specific material systems.

[0065] 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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An accident-resistant nuclear fuel cladding coating, characterized in that, The coating is a Cr-based binary alloy coating deposited on the surface of a zirconium alloy substrate. The binary alloy coating is selected from Cr-Fe alloy coating, Cr-V alloy coating, or Cr-Mo alloy coating. In the Cr-Fe alloy coating, the mass percentage of iron is 3 wt% to 10 wt%, with the balance being chromium. In the Cr-V alloy coating, the mass percentage of vanadium is 3 wt% to 20 wt%, with the balance being chromium. In the Cr-Mo alloy coating, the mass percentage of molybdenum is 1 wt% to 5 wt%, with the balance being chromium.

2. The accident-resistant nuclear fuel cladding coating according to claim 1, characterized in that, The Cr-Fe alloy coating contains 7 wt% iron by mass; the Cr-V alloy coating contains 7 wt% vanadium by mass; and the Cr-Mo alloy coating contains 3 wt% molybdenum by mass.

3. A method for preparing an accident-resistant nuclear fuel cladding coating, used to prepare the coating as described in claim 1 or 2, characterized in that, The magnetron sputtering process includes the following steps: Step A: Pre-treat the surface of the zirconium alloy substrate and fix it on the sample stage; Step B: Evacuate the vacuum chamber to a high vacuum, heat it to 150℃~250℃ and maintain the temperature, continue evacuating to achieve a background vacuum of 3×10⁻⁶. - Below ³ Pa; Step C: Introduce argon gas into the vacuum chamber until the working pressure is 0.3 Pa ~ 1.5 Pa, turn on the power to ignite, and then adjust the argon gas flow rate to stabilize the working pressure at 0.3 Pa ~ 0.8 Pa; Step D: Under the conditions of applying a bias voltage to the substrate and applying sputtering power, sputtering deposition is performed to form the Cr-based binary alloy coating on the surface of the zirconium alloy substrate.

4. The preparation method according to claim 3, characterized in that, In step B, the high vacuum degree is 4 × 10⁻⁶. - The heating temperature is 200°C when the pressure is below 3 Pa.

5. The preparation method according to claim 3, characterized in that, In step C, argon gas is introduced during ignition to bring the pressure to 1.0 Pa, and after ignition, the argon gas flow rate is adjusted to stabilize the deposition working pressure at 0.5 Pa.

6. The preparation method according to claim 3, characterized in that, In step D, the substrate bias voltage is -50V and the sputtering power is 300W.

7. The preparation method according to claim 3, characterized in that, The power supply used for sputtering deposition is either a DC power supply or a radio frequency power supply.

8. The preparation method according to any one of claims 3-7, characterized in that, Following the sputtering deposition step, a vacuum annealing step is also included on the coated zirconium alloy substrate, the vacuum annealing process comprising holding at a temperature of 700°C to 860°C, or holding at a temperature of 860°C to 1200°C.

9. A zirconium alloy component, characterized in that, An accident-resistant nuclear fuel cladding coating as claimed in claim 1 or 2 is provided on at least one of its surfaces.

10. The zirconium alloy component according to claim 9, characterized in that, The zirconium alloy components are nuclear reactor fuel cladding tubes or core structural components.

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