In-situ self-strengthening double-phase coating based on multi-element amorphous precursor as well as preparation method and application of in-situ self-strengthening double-phase coating

Abstract

The invention belongs to the field of protective coatings, and relates to an in-situ self-strengthening double-phase coating based on a multi-element amorphous precursor and a preparation method and application of the in-situ self-strengthening double-phase coating. Multi-component refractory alloy targets, graphite targets and Si-Al composite targets are co-sputtered through high-power pulse magnetron sputtering and radio frequency magnetron sputtering technologies, and the prepared coating is smooth and compact in surface and shows an amorphous structure. Elements such as C, Si and Al are introduced into refractory high-entropy alloy elements, in the high-temperature service process, a high-entropy M3SiC2 and Cr3Si double-phase nano structure is formed in the coating in situ, and meanwhile a Al2O3 and (Cr, Al) 2O3 multi-layer oxidation layer is formed on the surface. According to the in-situ transformation structural characteristic, the Zr alloy can be effectively prevented from being oxidized in a 1200 DEG C water vapor environment for 2 h and a 1300 DEG C water vapor environment for 60 min, excellent corrosion resistance and abrasion resistance are achieved, and a theoretical basis is provided for prolonging the service life of the fuel cladding zirconium alloy in a nuclear reactor.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of protective coatings, and relates to a multi-component composite coating with high-temperature oxidation resistance and structural stability, a preparation method and application. BACKGROUND

[0002] Improving the safety margin, service life and structural integrity of nuclear fuel elements under normal and accident conditions has become a key task for the development of nuclear energy technology. Zirconium alloys are widely used as fuel cladding materials due to their good neutron economy and mechanical properties. However, in a high-temperature steam environment exceeding 1200°C, zirconium alloys will undergo severe oxidation, generating brittle ZrO2 and releasing a large amount of hydrogen, which leads to a sharp decline in the mechanical properties of the cladding and even rupture, seriously threatening reactor safety. To address this challenge, surface protective coating technology is considered an effective way to improve the performance of zirconium alloy cladding under high-temperature steam, corrosion and wear coupling conditions. Existing research shows that metal coatings (such as Cr) and new MAX phase coatings have potential in reducing oxidation rates, promoting the formation of dense protective films and improving high-temperature stability, but also have obvious shortcomings: in Cr coatings, Zr diffuses along the grain boundaries at high temperatures to form ZrO2, weakening the interfacial bonding and accelerating oxidation; under ultra-high temperature conditions, interfacial ZrCr2 undergoes eutectic melting, causing the coating to fail. MAX phase coatings face the problem of structural loosening due to the migration and escape of C and N elements in the oxidation environment, and single hard phases often have brittleness or diffusion instability. Therefore, in recent years, research has focused on developing multi-phase composite coatings with excellent oxidation resistance, wear resistance and interfacial bonding force through material combination and microstructure design. An ideal high-performance coating should maintain structural integrity in a high-temperature steam environment of 1200-1300°C for a long time, effectively block oxygen diffusion, and have good mechanical stability, thereby significantly improving the accident tolerance capability of the fuel cladding. Our group previously strengthened the surface of zirconium alloy to form a M5Si3-SiC dual-phase coherent structure to prevent oxidation of Zr alloy, but there are still problems such as thick coating and short service time in a high-temperature steam environment of 1200-1300°C. To further solve this problem, our group explores the coating phase structure.

[0003] Multi-component refractory metal systems and high-entropy alloys have attracted extensive attention due to high mixing entropy, grain stability and excellent high-temperature performance. For example, Li et al. prepared an amorphous FeCrAlMoSiY coating on the surface of a zirconium alloy by magnetron sputtering. During high-temperature oxidation, silicon preferentially diffuses to the interface, forming a continuous and dense Zr2Si diffusion barrier layer in situ, effectively inhibiting element interdiffusion and promoting the formation of an outer alpha-Al2O3 protective film, thereby significantly improving the protective performance of the substrate (Corrosion Science 189 (2021) 109566). Another study prepared an amorphous / nanocrystalline composite MoAlB coating by direct current magnetron sputtering and annealing process, which showed excellent oxidation resistance in air at 1200℃. The mechanism is due to the synergistic effect of the amorphous phase barrier to oxygen diffusion and the rapid diffusion channel of Al in the nanocrystalline phase, which promotes the rapid formation and stability of the alpha-Al2O3 film (Acta Materialia 290 (2025) 120986). However, the thermal stress mismatch between the existing coating and the substrate at high temperatures is still a technical difficulty, and the existing oxidation-resistant coating is prone to oxidation instability, cracking and delamination, discontinuous protective layer, and structural degradation in water vapor environments at 1200-1300℃. SUMMARY

[0004] To solve the above technical problems, the present application proposes a kind of in-situ self-strengthening dual-phase coating based on multi-component amorphous precursor and its preparation method and application, a kind of multi-component composite coating system capable of forming stable multilayer oxidation film and strengthening phase structure in-situ at high temperature, long-term oxygen diffusion barrier and structural integrity The technical scheme of the present application is as follows: Based on the viscous flow and gradual crystallization characteristics of the multi-component amorphous system, the present application proposes an in-situ strengthening strategy for the coating using multi-component amorphous as precursor. Under high-temperature service conditions, through the thermodynamically driven sequential phase transition (Amorphous→MC→MSi→MAX), a nanometer "hard-soft" coupled structure composed of Cr3Si and high-entropy M3SiC2 phases is constructed. This structure is not simply a mixture of phases, but forms a self-organized interface of "high-entropy M3SiC2 phase wrapping Cr3Si", which significantly improves the oxidation resistance, wear resistance and high-temperature stability of the coating compared to single Cr coating or traditional MAX phase coating, showing a "1+1>2" composite strengthening effect.

[0005] Adaptive amorphous coating represents an emerging design strategy: during service, its amorphous precursor structure can spontaneously transform into a more stable composite structure in response to external environment (such as friction, high-temperature oxidation), endowing the material with the ability of "self-evolution". The structure coordinates deformation and inhibits crack propagation through in-situ strengthening, thereby simultaneously improving strength, toughness and oxidation resistance, breaking through the traditional performance "inverted" relationship. In multi-component systems, the difference in element diffusion ability and complex interaction help to form a stable multi-phase structure, and the in-situ generated heterogeneous interface (such as nanocrystalline / amorphous interface) can effectively hinder dislocation movement, becoming the key strengthening mechanism.

[0006] Based on the above principle, in one aspect, the application provides an in-situ self-strengthening dual-phase coating based on a multi-element amorphous precursor, the in-situ self-strengthening dual-phase coating is an amorphous structure, has a high-entropy M3SiC2 phase and a Cr3Si dual-phase nanocrystalline layer, and Cr, Ta, Nb, Ti, V, Al, Zr, Si and C are uniformly distributed in the coating. The coating is tightly combined with a Zry-4 alloy substrate (zirconium alloy substrate).

[0007] The atomic percentage content of each element in the in-situ self-strengthening dual-phase coating is as follows: Cr 19.1% to 22.2%, Ta 4.9% to 6.3%, Nb 4.9% to 6.5%, Ti 5.2% to 5.4%, V 4.8% to 7.3%, Al 5.1% to 5.4%, Zr 4.6% to 6.7%, Si 18.5% to 20.6%, and C 22.3% to 30.4%.

[0008] In a second aspect, the application provides a preparation method of the above-mentioned in-situ self-strengthening dual-phase coating, comprising the following steps: (1) polishing the surface of the zirconium alloy substrate, then ultrasonic cleaning the polished zirconium alloy substrate in acetone for 15 min, after cleaning, blowing dry with nitrogen, and fixing the zirconium alloy substrate on a sample disc; (2) installing the zirconium alloy substrate sample disc in the chamber of a multi-target magnetron sputtering instrument, closing the chamber door and sequentially performing high vacuum pumping, substrate heating, inert gas inlet, adjusting the deposition gas pressure, opening the substrate shutter, turning on the power and performing coating deposition, using a multi-component refractory alloy target, a graphite target and a Si-Al composite target as target materials, using a zirconium alloy as the substrate, and using a magnetron sputtering technology to co-sputter deposit an amorphous structure coating. After the temperature cools down, the coating sample is taken out and stored in a vacuum environment to obtain a zirconium alloy surface coating. The multi-component refractory alloy target is composed of six elements selected from Cr, Ta, Nb, Ti, Zr and V.

[0009] The surface of the zirconium alloy base in step (1) is cleaned by polishing one side of the zirconium alloy base with 600#-2000# sandpaper, and then the polished zirconium alloy base is cleaned with deionized water and anhydrous ethanol for 20-30 min.

[0010] Preferably, the polishing operation is as follows: the zirconium alloy base is polished with 600#, 1200# and 2000# sandpaper in sequence.

[0011] The conditions for coating deposition in step (2) are as follows: the distance between the multi-component refractory alloy target, the graphite target and the Si-Al composite target and the base is 6 mm, the background vacuum degree is 6.4*10 -4 ~ 7.5*10 -4 Pa, the heating temperature is 100℃, the deposition time is 15-20 h, the bias power is -50 to -180 V, the sputtering current of the multi-component refractory alloy target is controlled to be 300 ma, the sputtering current of the graphite target is 200-420 ma, the sputtering power of the Si-Al composite target is 180-360 W, the argon flow rate is 20 sccm, the argon gas purity is ≥99.999%, and after sputtering, the temperature is cooled to 50-60℃.

[0012] Preferably, the deposition power source of the multi-component refractory alloy target and the graphite target is a high-power pulsed direct current power source (HZ101), and the deposition power source of the Si-Al composite target is a radio frequency power source.

[0013] In a third aspect, the in-situ self-strengthening dual-phase coating is applied to the protection of nuclear fuel cladding materials and other oxidation-resistant fields.

[0014] The in-situ self-strengthening dual-phase coating has the advantages that after high-temperature oxidation at 1200℃, the structure of the coating evolves into a continuous multi-layer oxide layer in the outermost layer, a ZrC layer formed in-situ at the coating / base interface, and a high-entropy M3SiC2 phase and a Cr3Si dual-phase nanocrystalline layer in the residual coating, so that the coating exhibits excellent oxidation resistance and comprehensive mechanical properties, and can prevent the zirconium alloy base from being oxidized in a water vapor environment at 1200℃ for 2 h and in a water vapor environment at 1300℃ for 60 min.

[0015] The in-situ self-strengthening dual-phase coating has the following advantages: 1. The application establishes a design window that can predict high-temperature structural evolution, ensures that the system preferentially forms Cr3Si phase and high-entropy M3SiC2 phase, avoids the generation of harmful phases, and thus accurately regulates the amorphous to dual-phase nanocrystalline transformation process at the design stage. Among them, the Cr3Si phase provides a high-strength and wear-resistant skeleton, the high-entropy M3SiC2 phase contributes to toughness, thermal shock resistance and high-temperature stability brought by slow diffusion, and the two achieve optimal matching in terms of interface structure, thermal expansion coefficient and oxidation film composition. Through the trinity of "composition-diffusion-phase change", the controllability of the coating structure and the performance synergy that traditional processes cannot achieve are realized, providing an innovative concept and technical path for the development of a new generation of nuclear fuel cladding high-temperature protective coating.

[0016] 2. The application utilizes multi-target high-power pulsed magnetron sputtering and radio frequency sputtering to co-deposit multi-component refractory metals, C, Si and Al elements, so that the coating forms a uniform and dense amorphous structure in the deposited state, effectively reduces grain boundary defects and diffusion channels, greatly improves the oxidation resistance at the initial stage, and significantly improves the bonding performance and interface stability of the coating and the zirconium alloy substrate.

[0017] 3. The coating of the application can in-situ form a continuous Al2O3 and (Cr, Al)2O3 composite oxide layer during high-temperature oxidation above 1200℃, and at the same time, high-entropy M3SiC2 phase and Cr3Si dual-phase nanocrystalline structure are generated inside the coating, and a dense ZrC layer is formed at the interface, forming a multi-protection system of outer oxygen barrier, middle strengthening and inner passivation, greatly improving the high-temperature structural stability. The coating of the application can stably serve in a 1200℃ water vapor environment for 2 hours and be not oxidized for 60 minutes in a 1300℃ environment, which is significantly better than the metal or ceramic coating system in the prior art, greatly improving the oxidation resistance, corrosion resistance and service reliability of zirconium alloy under severe accident conditions, and providing a new material solution for improving the safety of nuclear fuel cladding. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creating any inventive labor.

[0019] Figure 1 SEM images of the coatings prepared in Examples 1-4; wherein (a) is the original surface morphology of the coating prepared in Example 1, (b) is the original surface morphology of the coating prepared in Example 2, (c) is the original surface morphology of the coating prepared in Example 3, and (d) is the original surface morphology of the coating prepared in Example 4.

[0020] Figure 2 XRD patterns of the coatings prepared in Examples 1-4 of the present application; wherein a is Example 1, b is Example 2, c is Example 3, d is Example 4.

[0021] Figure 3 Hardness and Young's modulus of the coatings prepared in Examples 1-4 of the present application; wherein a is Example 1, b is Example 2, c is Example 3, d is Example 4.

[0022] Figure 4 Optical microscope cross-sectional morphology of the coatings prepared in Examples 1-4 of the present application; wherein (a) is Example 1, (b) is Example 2, (c) is Example 3, (d) is Example 4.

[0023] Figure 5 Oxidation weight gain versus time curves of the coatings prepared in Examples 1-4 of the present application under working environment of Zr substrate; wherein a is Example 1, b is Example 2, c is Example 3, d is Example 4.

[0024] Figure 6 Bonding strength variation patterns of the coatings prepared in Examples 1-4 of the present application; wherein a is Example 1, b is Example 2, c is Example 3, d is Example 4.

[0025] Figure 7 Cross-sectional oxidation morphology of the coating prepared in Example 3 of the present application after oxidation at 1200℃; wherein (a) is the overall cross-sectional morphology, (b) is the surface oxidation layer, (b1) is the upper oxidation layer α-Al2O3, (b2) is the lower oxidation layer (Cr, Al)2O3, (c) is the morphology of the oxidation layer and the oxidation transition layer and the corresponding face scanning distribution map.

[0026] Figure 8 Morphology and phase of the oxidation layer and the oxidation transition layer of the coating prepared in Example 3 of the present application after oxidation at 1200℃; wherein (a) is the overall cross-sectional morphology, (b) is the phase in the oxidation transition layer, (c) is ZrO2, (d) is high-entropy oxide (HEO), (d) is Al2O3, (e) is amorphous SiO2.

[0027] Figure 9 Structure of high-entropy M3SiC2 and Cr3Si in the residual coating of the coating prepared in Example 3 of the present application after oxidation at 1200℃; wherein (a) is the overall morphology of the residual coating, (b) is the typical enlarged morphology, (b1) is the diffraction of the polycrystal in the residual coating, mainly high-entropy M3SiC2 and Cr3Si, (c-d)-(c1-d1) are the high-resolution and diffraction stripes of the phase in the residual coating, and the corresponding phases are Cr3Si and M3SiC2, respectively, (e) is the morphology of the residual coating and the corresponding element face scanning distribution map.

[0028] Figure 10 The ZrC structure in-situ formed between the coating and the substrate after oxidation at 1200 DEG C for the coating prepared in Example 3 of the present application; wherein (a) is the overall morphology of the residual coating and the substrate, (b) is the diffraction stripe of the ZrC formed in-situ, and (c) is the elemental mapping of the residual coating and the substrate.

[0029] Figure 11 The structure of the residual coating after high-temperature oxidation at different temperatures for the amorphous coating prepared in Example 3 of the present application; wherein a is 1200 DEG C, and b is 1300 DEG C.

[0030] Figure 12 The stress condition and indentation morphology of the coating prepared in Examples 2-4 of the present application during high-temperature oxidation; (a) in the figure, a is Example 2, b is Example 3, and c is Example 4. Indentation morphology: (b) is Example 2, (c) is Example 3, and (d) is Example 4.

[0031] Figure 13 The surface cross-section structure and residual stress analysis of the coating (4-a-c1, 3-d-d1) prepared in Examples 3 and 4 of the present application during high-temperature oxidation; wherein a-c1 is the surface cross-section structure of Example 4, d-d1 is the surface cross-section structure of Example 3, g is the Raman stress result of Example 4, and h is the Raman stress result of Example 3.

[0032] Figure 14 The XRD result of the coating prepared in Examples 1-4 of the present application after high-temperature oxidation; wherein a is Example 1, b is Example 2, c is Example 3, and d is Example 4. DETAILED DESCRIPTION

[0033] The technical solutions of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0034] In the following experimental examples, the experimental methods used are conventional methods unless otherwise specified; and the materials, reagents, etc. used are reagents and materials available through commercial channels unless otherwise specified.

[0035] The purity of the multi-component refractory alloy target used in the present application is >99.999%, and the multi-component refractory alloy target is composed of Cr, Ta, Ti, Nb, Zr and V; the purity of the graphite target is >99.99%, and the purity of the Si-Al composite target is >99.9%.

[0036] Embodiment 1 The preparation method of the in-situ self-strengthening dual-phase coating based on a multi-element amorphous precursor of the present embodiment comprises the following steps: (1) The surface of the zirconium alloy substrate is polished and then the polished zirconium alloy substrate is ultrasonically cleaned. Specifically, the zirconium alloy substrate is polished with 600#, 1200# and 2000# sandpaper in sequence, and the polished zirconium alloy substrate is ultrasonically cleaned with deionized water and anhydrous ethanol for 20 minutes in sequence. After cleaning, the zirconium alloy substrate is dried with nitrogen and fixed on a sample disc.

[0037] (2) The zirconium alloy substrate sample disc is installed in the chamber of a multi-target magnetron sputtering instrument. The chamber door is closed and high vacuum is pumped. The substrate is heated, inert gas is introduced, and the deposition pressure is adjusted. The substrate shutter is opened, the power is turned on, and the coating is deposited. A multi-element refractory alloy target, a graphite target and a Si-Al composite target are used as target materials, and a zirconium alloy is used as the substrate. The coating is obtained by magnetron sputtering deposition technology. After the temperature cools down, the coating sample is taken out and stored in a vacuum environment. An in-situ self-strengthening dual-phase coating is obtained. The multi-element refractory alloy target contains Cr, Ta, Ti, Nb, Zr and V.

[0038] The conditions for coating deposition are as follows: the distance between the multi-element refractory alloy target, the graphite target and the Si-Al composite target and the substrate is 5 mm, the background vacuum degree is 7.9 x 10 4 Pa, the heating temperature is 100°C, the deposition time is 18 h, the bias voltage power is -60 V, the sputtering current of the multi-element refractory alloy target is controlled at 300 mA, the sputtering current of the graphite target is 300 mA, the sputtering power of the Si target is 160 W, the argon gas flow rate is 20 sccm, the argon gas purity is ≥ 99.999%, and after sputtering, the temperature is cooled to 60-80°C.

[0039] The detection results of the in-situ self-strengthening dual-phase coating prepared in the present embodiment show that the content of Cr is 19.9%, the content of Ti is 5.3%, the content of Nb is 6.7%, the content of Ta is 8.3%, the content of Zr is 6.4%, the content of V is 7.4%, the content of Al is 4.7%, the content of Si is 18.5%, and the content of C is 22.3%. The phase structure of the coating is shown in Figure 2 (a) and exhibits an amorphous structure. The thickness of the coating is 3.6 µm. The hardness of the coating is 18 GPa, and the Young's modulus is 198 Gpa (a). Figure 3

[0040] Embodiment 2 The preparation method of the in-situ self-strengthening dual-phase coating based on a multi-element amorphous precursor of the present embodiment comprises the following steps: ​(1) The surface of the zirconium alloy substrate is polished and then the polished zirconium alloy substrate is ultrasonically cleaned. Specifically, the zirconium alloy substrate is polished with 600#, 1200# and 2000# sandpaper in sequence, and the polished zirconium alloy substrate is ultrasonically cleaned with deionized water and anhydrous ethanol for 25 minutes in sequence. After cleaning, the zirconium alloy substrate is dried with nitrogen and fixed on a sample disc.

[0041] (2) The zirconium alloy substrate sample disc is installed in the chamber of a multi-target magnetron sputtering instrument, the chamber door is closed, and high vacuum is pumped. The substrate is heated, inert gas is introduced, and the deposition pressure is adjusted. The substrate shutter is opened, the power is turned on, and coating deposition is performed. A multi-element refractory alloy target, a graphite target and a Si-Al composite target are used as target materials, zirconium alloy is used as the substrate, and a coating is obtained by magnetron sputtering deposition. After the temperature cools down, the coating sample is taken out and stored in a vacuum environment to obtain an in-situ self-reinforced dual-phase coating. The multi-element refractory alloy target contains Cr, Ta, Ti, Nb, Zr and V.

[0042] The coating deposition conditions are as follows: the distance between the multi-element refractory alloy target, the graphite target and the Si-Al composite target and the substrate is 5 mm, the background vacuum is 5.4 x 10 -4 Pa, the deposition temperature is set to 150°C, the deposition bias power is -100 V, the flow rate of the inert gas argon is set to 20 sccm, the deposition pressure of the coating is 0.5 Pa, the sputtering current of the multi-element refractory alloy target is 500 ma, the sputtering current of the graphite target is 380 ma, the sputtering power of the Si-Al composite target is 230 W, the coating deposition time is 12 h, and the sample is taken out after cooling to 60°C.

[0043] The detection results of the embodiment show that the content of Cr is 21.3%, the content of Ti is 6.5%, the content of Nb is 6.2%, the content of Ta is 5.6%, the content of Al is 5.3%, the content of Zr is 5.2%, the content of V is 5.2%, the content of Si is 20.5%, and the content of C is 24.2%. The phase structure of the coating is shown in (b) and exhibits an amorphous structure. Compared with (a), the diffraction peak is shifted to the right, indicating that the coating structure gradually becomes dense. The thickness of the coating is 4.3 µm. The hardness of the coating is 23 GPa, and the Young's modulus is 235 Gpa (b). Figure 2 Figure 3

[0044] Example 3 The preparation method of the in-situ self-reinforced dual-phase coating based on a multi-element amorphous precursor of the embodiment comprises the following steps: ​​(1) The surface of the zirconium alloy substrate is polished and then the polished zirconium alloy substrate is ultrasonically cleaned. Specifically, the zirconium alloy substrate is polished with 600#, 1200# and 2000# sandpaper in sequence, and the polished zirconium alloy substrate is ultrasonically cleaned with deionized water and anhydrous ethanol for 20 minutes in sequence. After cleaning, the zirconium alloy substrate is dried with nitrogen and fixed on a sample disc.

[0045] (2) The zirconium alloy substrate sample disc is installed in the chamber of a multi-target magnetron sputtering instrument, the chamber door is closed, and high vacuum is pumped. The substrate is heated, inert gas is introduced, and the deposition pressure is adjusted. The substrate shutter is opened, the power is turned on, and coating deposition is performed. A multi-element refractory alloy target, a graphite target and a Si-Al composite target are used as target materials, zirconium alloy is used as the substrate, and a coating is obtained by magnetron sputtering deposition. After cooling, the coating sample is taken out and stored in a vacuum environment to obtain an in-situ self-reinforced dual-phase coating. The multi-element refractory alloy target contains Cr, Ta, Ti, Nb, Zr and V.

[0046] The coating deposition conditions are as follows: the distance between the multi-element refractory alloy target, the graphite target and the Si-Al composite target and the substrate is 5 mm, the background vacuum is 6x10 -4 Pa, the deposition temperature is set to 120°C, the deposition bias power is -100V, the flow rate of inert gas argon is set to 20 sccm, the deposition pressure of the coating is 0.5 Pa, the sputtering current of the multi-element refractory alloy target is 500 ma, the sputtering current of the graphite target is 240 ma, the sputtering power of the Si-Al composite target is 220 W, the coating deposition time is 15 h, and the sample is taken out after cooling to 60°C.

[0047] The detection results of the embodiment show that the content of Cr is 20.2%, the content of Ti is 4.9%, the content of Nb is 4.8%, the content of Ta is 5.8%, the content of Zr is 5.7%, the content of Al is 4.6%, the content of V is 5.3%, the content of Si is 20.6%, and the content of C is 28.3%.

[0048] The phase structure of the coating is shown in Figure 2 (c), which exhibits an amorphous structure. The thickness of the coating is 4.5 µm. The hardness of the coating is 28 GPa, and the Young's modulus is 269 Gpa (c). Figure 3

[0049] Example 4 The preparation method of the in-situ self-reinforced dual-phase coating based on a multi-element amorphous precursor of the embodiment comprises the following steps: ​(1) The surface of the zirconium alloy substrate is polished and then the polished zirconium alloy substrate is ultrasonically cleaned. Specifically, the zirconium alloy substrate is polished with 600#, 1200# and 2000# sandpaper in sequence, and the polished zirconium alloy substrate is ultrasonically cleaned with deionized water and anhydrous ethanol for 28 min in sequence. After cleaning, the zirconium alloy substrate is dried with nitrogen and fixed on a sample disc.

[0050] (2) The zirconium alloy substrate sample disc is installed in the chamber of a multi-target magnetron sputtering instrument, the chamber door is closed, and high vacuum is extracted, the substrate is heated, inert gas is introduced, and the deposition pressure is adjusted in sequence. The substrate shutter is opened, the power is turned on, and coating deposition is performed. A multi-element refractory alloy target, a graphite target and a Si-Al composite target are used as target materials, zirconium alloy is used as the substrate, and a coating is obtained by magnetron sputtering technology. After cooling, the coating sample is taken out and stored in a vacuum environment to obtain an in-situ self-reinforced dual-phase coating. The multi-element refractory alloy target contains Cr, Ta, Ti, Nb, Zr and V.

[0051] The coating deposition conditions are as follows: the distance between the multi-element refractory alloy target, the graphite target and the Si-Al composite target and the substrate is 5 mm, the background vacuum is 8.6 x 10 -4 Pa, the deposition temperature is set to 100°C, the deposition bias power is -160 V, the flow rate of inert gas argon is set to 20 sccm, the deposition pressure of the coating is 0.5 Pa, the sputtering current of the multi-element refractory alloy target is 600 ma, the sputtering current of the graphite target is 450 ma, the sputtering power of the Si-Al composite target is 200 W, the coating deposition time is 10 h, and the sample is taken out after cooling to 60°C.

[0052] The detection results of the embodiment show that the content of Cr is 19.1%, the content of Ti is 5.8%, the content of Nb is 4.5%, the content of Ta is 4.9%, the content of Zr is 4.8%, the content of Al is 6.7%, the content of V is 4.8%, and the content of Si is 19.6%, and the content of C is 30.4%.

[0053] The phase structure of the coating is shown in Figure 2 (d), which exhibits an amorphous structure. The thickness of the coating is 3.9 µm. The hardness of the coating is 36 GPa, and the Young's modulus is 310 Gpa (d). Figure 3

[0054] Effect example The coatings prepared in Examples 1-4 are detected: 1. The coating sample is prepared into a TEM cross-section sample using FIB, and the structure of the coating sample is analyzed by a transmission electron microscope (TEM, FEI Tecnai G2F20) and a field emission scanning electron microscope (SEM, Sigma 300). The results show that the coating is a dual-phase coating with a self-reinforced structure, and the coating is composed of a self-reinforced phase and a non-self-reinforced phase. Figure 1 ​It can be seen that the surface morphology of the coating prepared in embodiments 1-4 is smooth and flat.

[0055] 2. The structure change of the coating under different components was analyzed by X-ray diffractometer (XRD, XRO-6100). The results are shown in Figure 2 It can be seen from the XRD spectrum of the amorphous coating prepared in embodiments 1-4 that the coating presents an amorphous structure. Figure 2 3. Refer to ISO 14577-1:2015 standard. The test is carried out at room temperature using Berkovich diamond indenter. The maximum load is set to 10 mN, so that the indentation depth is strictly controlled within 10% of the coating thickness (about ≤400 nm). At least 5 effective indentations are completed at different positions for each sample, and the average value is taken. When analyzing the data, the Poisson ratio of the coating material is taken as 0.25; the change trajectory (a<b<c) of hardness and Young's modulus intuitively reflects that the intrinsic mechanical strength of the coating can be effectively improved by increasing the deposition energy (bias voltage, temperature) and increasing the content of hard elements (such as C). The results are shown in Figure 3 It can be seen from the hardness and Young's modulus of the amorphous coating prepared in embodiments 1-4 that the hardness and Young's modulus of the coating are obviously improved, which is beneficial to improve the service life of the coating. Figure 3

[0056] However, in view of the performance of embodiment 3, simply pursuing the highest hardness and modulus of the deposited state is not the optimal strategy. Embodiment 3 obtains an amorphous precursor structure that can occur beneficial in-situ phase change and realize stress self-adaptation during high-temperature service by precisely controlling the relative ratio of C to Si / Al under the premise of ensuring sufficient densification. This makes it exhibit more excellent comprehensive performance (high bonding strength, low mismatch stress, excellent oxidation resistance) in the service state (after high-temperature oxidation), which embodies the core advantage of the "in-situ self-strengthening" design.

[0057] 4. Figure 4 The optical microscope cross-sectional morphology of the coating prepared in embodiments 1-4 after high-temperature oxidation. The coating in embodiment 3 (c) has the most excellent oxidation resistance.

[0058] ​​5. The isothermal oxidation kinetics of the coatings were tested on a custom-built high-temperature water vapor oxidation setup, following the basic procedure of ASTM G54-07 (2020) and the rigorous gravimetric method of ASTM C1179-13. The coating samples with a size of 10 mm x 10 mm were placed in a corundum crucible and put into the constant temperature zone of a tube furnace equipped with a high-sensitivity (0.1 pg) balance. Before the test, the system was purged with high-purity argon (99.999%). After heating to the target temperature (1200 °C or 1300 °C), a 50 vol.% water vapor mixed gas carried by high-purity argon was introduced, and the total flow rate was controlled at 100 seem. From the introduction of steam, the system automatically and continuously recorded the change of sample mass with time until the preset time (2 h for 1200 °C) or the mass increased dramatically. Each test condition was repeated at least three times, and the oxidation weight gain data were reported as the mass change per unit area (mg / cm2). The results are shown in FIG. 1, which shows that the oxidation kinetics curve of the amorphous coating prepared in Example 1-4 presents a trend of first increasing and then decreasing in the oxidation resistance of the coating at 1200 °C. Figure 5 Figure 5 It can be seen from the oxidation kinetics curves shown in FIG. 1 that the oxidation resistance of the coating prepared in Example 1-4 presents a trend of first increasing and then decreasing at 1200 °C. Figure 5 The oxidation kinetics curves shown in FIG. 1 clearly reveal the significant performance differences of the four examples, and the root cause lies in that different deposition process parameters dominate the phase transformation behavior and failure mode of the coating at high temperature by regulating the composition (especially the relative proportion of carbon and silicon / aluminum) and microstructure of the coating. Specifically, Example 1-(a) has a general oxidation resistance because the low deposition energy and carbon content lead to insufficient coating density and lack of element reserves for forming a stable oxidation film; Example 2-(b) enhances the density by increasing the deposition energy and carbon content, but the excessive carbon may cause microstructure instability in long-term oxidation, limiting the further improvement of its protection potential; the best-performing Example 3-(c) adopts the key composition design of “high C and high Si”, combined with appropriate deposition energy, so that it can form a complete protection system in situ at high temperature, consisting of a dense a-Al2O3 / (Cr, Al)2O3 outer layer, an internal high-entropy M3SiC2 / Cr3Si nanophase reinforced layer, and an interface ZrC barrier layer, while having the lowest thermal mismatch stress (92.5 MPa), thus realizing the rapid formation and long-term stability of the protective oxidation; in sharp contrast, Example 4-(d) has the highest as-deposited hardness by using an extremely high bias voltage and carbon content, but also introduces a huge internal stress and metastable structure, which rapidly cracks and fails at high temperature due to stress release and carbon escape, resulting in poor oxidation resistance.

[0059] ​6. Coating bond strength was tested by scratch test according to ISO 20502:2019 standard after coating experienced 1200℃ steam oxidation. The test was performed on the oxidized coating surface using a scratch tester equipped with acoustic emission sensors and a conical diamond indenter, using a progressive loading mode (0-50 N, loading rate 100 N / min). By monitoring the acoustic emission signal mutation, friction coefficient change and combining SEM microscopic observation of scratch track, the critical load of coating failure (such as cracking or peeling) was determined. The results are shown in Figure 6 .

[0060] From Figure 7 it can be seen that the bond strength of the amorphous coating prepared in Examples 1-4 changes after oxidation at 1200℃, the bond strength of the coating is significantly improved, which can effectively prevent the peeling of the coating in the working environment. The method quantitatively shows that the bond strength of the coating of each example is significantly improved after high temperature oxidation, especially the critical load of Example 3 with optimized composition is the highest, which directly verifies the excellent interface stability achieved by forming a dense ZrC interface layer and a complete coating structure, which effectively supports the long-term service reliability of the "in-situ self-strengthening" coating.

[0061] From Figure 7 it can be seen that the cross-section oxidation morphology of the coating prepared in Example 3 of the present application after oxidation at 1200℃; wherein (a) is the overall cross-section morphology (b) is the surface oxidation layer (b1) is the upper oxidation layer α-Al2O3, (b2) is the lower oxidation layer (Cr, Al)2O3, (c) is the morphology and corresponding face scanning distribution of the oxidation layer and the diffusion layer. Because the Al element introduced in the coating has a higher outward diffusion and oxidation tendency at 1200-1300℃, a dense, stable and long-term effective α-Al2O3 outer layer can be generated on the surface of the coating, which together with the (Cr, Al)2O3 inner layer forms a gradient-matched Al2O3 / (Cr, Al)2O3 double-layer oxidation film, which has excellent oxygen resistance, volatility resistance and thermal shock stability, and the thermal expansion matching between the double-layer oxidation layer and the residual coating is good, so that the oxidation film is not easy to peel off and crack.

[0062] Figure 8 The morphology and phase of the oxidation layer and the oxidation transition layer of the coating prepared in Example 3 of the present application after oxidation at 1200℃; wherein (a) is the overall cross-section morphology, (b) is the phase in the oxidation transition layer, (c) is ZrO2, (d) is HEO (e) is amorphous SiO2, from Figure 8 it can be seen that the structure of the oxidation transition layer exhibits its significant design advantages. On the one hand, the amorphous SiO2 phase ( Figure 8(e) As a stress buffer medium, it can effectively relax the interfacial residual stress caused by the mismatch of thermal expansion coefficient between the oxide layer and the substrate, inhibit the initiation and propagation of microcracks, and thus improve the thermal shock resistance and the adhesion of the coating. On the other hand, the ZrO2 in the transition layer can Figure 8 (c) The HEO (high entropy oxide) can Figure 8 (d) The amorphous SiO2 can Figure 8 e) Form a composite structure, and the multiphase mixed oxide system has high stability of the crystal phase and dense diffusion resistance characteristics of the amorphous phase, which not only further slows down the rate of inward diffusion of oxygen ions, but also enhances the structural toughness and high-temperature stability of the transition layer through interphase synergy. The long-term protection capability of the coating in an extreme environment of 1200 DEG C is significantly improved.

[0063] As can be seen from Figure 9 It can be seen from the drawings that the coating prepared in Example 3 has a dual-phase structure of high-entropy M3SiC2 and Cr3Si after oxidation at 1200 DEG C, wherein the high-entropy M3SiC2 phase has the toughness characteristics of layering, slippage and passivation of cracks, and the Cr3Si phase provides a stable skeleton with high modulus and high hardness, so that the two phases realize synergistic bearing and stress dispersion on the nanoscale.

[0064] As can be seen from Figure 10 It can be seen from the drawings that the ZrC structure formed in situ between the coating and the substrate in the amorphous coating prepared in Example 3 after oxidation at 1200 DEG C, and a continuous and dense ZrC diffusion barrier layer is formed in situ at the interface between the coating and the zirconium alloy substrate after the coating is oxidized at 1200 DEG C. This key structure fundamentally stabilizes the interface and prevents the formation of low-melting-point eutectic phases by blocking the interdiffusion between Zr and coating elements. Among them, Example 3 has an optimized composition design of "high C and high Si", which provides a carbon source to form a high-quality ZrC layer while avoiding excessive internal stress-induced structural instability, so that the interface layer, the double-layer oxide film above, and the internal nanoduplex structure form a complete and thermomechanically matched multiple protection system, perfectly interpreting the core mechanism of the "in-situ self-strengthening" design in realizing the reliability of service at an ultra-high temperature.

[0065] As can be seen from Figure 11It can be known that the structure of the residual coating of the amorphous coating prepared in embodiment 3 after high-temperature oxidation at different temperatures (1200 DEG C-a, 1300 DEG C-b) can be significantly inhibited due to the high-entropy effect of the multi-component amorphous precursor, the competitive growth is slowed down, the biphase can still maintain a fine and uniform structure at a higher temperature for a long time, and therefore more durable mechanical stability and oxidation resistance can be realized.

[0066] Figure 7 、 8 , 9, 10, 11 constitute a complete "structure evolution analysis chain", they all come from the same key processing condition: the coating sample of embodiment 3 is subjected to isothermal oxidation in a 1200 DEG C water vapor environment (50 vol.% H2O) for 120 min. The disclosure of these structures depends on the advanced "FIB-TEM" combined technology: first, a cross-section thin slice is accurately prepared by FIB, and then the high spatial resolution and diffraction ability of TEM are used to analyze the nanoscale phase composition and crystal structure. The selection of the drawings (mainly embodiment 3) has a clear purpose: embodiment 3 is proved to be the most optimal embodiment of composition and performance, and it is used as a representative to show the "triple protection system of double-layer oxidation film (Al2O3 / (Cr, Al)2O3) - nano-biphase strengthening layer (high-entropy M3SiC2 / Cr3Si) - interface ZrC barrier layer", which most strongly supports the technical effect and core of the application "in-situ self-strengthening".

[0067] Figure 12 (a) is the stress condition of the coating prepared in embodiments 2, 3 and 4 (2-a, 3-b, 4-c) in the high-temperature oxidation process, and the thermal mismatch stress generated by the difference in the thermal expansion coefficient of the three coatings and the oxidation layer is 307.4 MPa, 92.5 MPa and 922.4 MPa, respectively. According to the stress calculation results, the b coating shows the lowest level on the two stress items, indicating that the oxidation layer / coating system has better thermal-mechanical compatibility and stronger high-temperature stress dissipation ability: on the one hand, the formation of the high-entropy M3SiC2 phase and the Cr3Si phase regulates the equivalent thermal expansion response of the coating, reducing the mismatch driving force; on the other hand, the multiphase refinement and phase boundary structure provide a channel for strain redistribution and relaxation at high temperature, weaken the stress peak and gradient in the oxidation layer, thereby reducing the driving force of crack initiation and penetration and being conducive to maintaining the integrity and protection of the oxidation film. Through the indentation results (b)-(c)-(d) (corresponding to examples 2, 3 and 4), for embodiment 3, the surface flatness is optimal, and there is no large crack and falling phenomenon.

[0068] Figure 13The surface cross-section structure and residual stress analysis of the coating (3-a-c1, 4-d-d1) prepared in Examples 3 and 4 at different times during high-temperature oxidation. The coating in Example 4 had excessive internal stress during high-temperature oxidation, and as time went on, the coating was severely oxidized. The surface oxide increased, and the internal stress of the coating gradually increased. As the coating was oxidized and cracked, the internal stress of the coating was released. The coating in Example 3 was structurally complete at different times during high-temperature oxidation. The internal stress of the coating did not change significantly, as shown by Raman analysis (h).

[0069] Figure 14 The XRD results of the coating (1-a, 2-b, 3-c, 4-d) prepared in Examples 1, 2, 3 and 4 after high-temperature oxidation. Example 1 (a) had ZrO2 and Cr2O3 diffraction peaks, accompanied by a small amount of silicide / carbide peaks. Example 2 (b) still detected significant Cr2O3 and ZrO2, as well as Cr3Si and some carbide-related peaks. Example 3 (c) had Al2O3 and (Cr, Al)2O3 as the main surface oxidation products, and M3SiC2 (high-entropy M3SiC2 phase) and Cr3Si characteristic peaks were observed in the residual coating, accompanied by interface ZrC signals. Example 4 (d) showed stronger carbide (such as MC, ZrC, TiC) related peaks, and still had ZrO2 and other oxidation product peaks, indicating that the phase composition after oxidation was more complex.

[0070] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An in-situ self-reinforced dual-phase coating based on a multi-element amorphous precursor, characterized in that: The in-situ self-reinforcing dual-phase coating has an amorphous structure with a high-entropy M3SiC2 phase and a Cr3Si dual-phase nanocrystalline layer. Cr, Ta, Nb, Ti, V, Al, Zr, Si and C are uniformly distributed in the coating, and the coating is tightly bonded to the zirconium alloy substrate.

2. The in-situ self-reinforced dual-phase coating based on a multi-element amorphous precursor according to claim 1, characterized in that, The atomic percentage content of each element in the in-situ self-reinforcing dual-phase coating is as follows: Cr 19.1%~22.2%, Ta 4.9%~6.3%, Nb 4.9%~6.5%, Ti 5.2%~5.4%, V 4.8%~7.3%, Al 5.1%~5.4%, Zr 4.6%~6.7%, Si 18.5%~20.6% and C 22.3%~30.4%.

3. The method for preparing an in-situ self-reinforced dual-phase coating based on a multi-element amorphous precursor as described in claim 1 or 2, characterized in that, The steps are as follows: (1) After the zirconium alloy substrate is polished, it is ultrasonically cleaned in acetone and then dried with nitrogen to obtain a pretreated zirconium alloy substrate. (2) The pretreated zirconium alloy substrate is co-sputtered in an argon atmosphere to obtain an amorphous coating, and after cooling, a zirconium alloy surface coating is obtained. The multi-target magnetron sputtering technology uses multi-component refractory alloy targets, graphite targets, and Si-Al composite targets as target materials; among them, the multi-component refractory alloy targets use six elements from Cr, Ta, Nb, Ti, Zr, and V.

4. The method for preparing an in-situ self-reinforced dual-phase coating based on a multi-element amorphous precursor according to claim 3, characterized in that: In step (1), the grinding and polishing is carried out by using 600#-2000# sandpaper for single-sided grinding and polishing. After grinding and polishing, the surface is ultrasonically cleaned with deionized water and anhydrous ethanol for 20~30 minutes.

5. The method for preparing an in-situ self-reinforced dual-phase coating based on a multi-element amorphous precursor according to claim 4, characterized in that: The back vacuum level in step (2) is 5.4 × 10⁻⁶. -4 ~ 8.6×10 -4 Pa, heating temperature is 100℃, deposition time is 10 ~ 18h, bias power supply power is -60 ~ -160V, argon flow rate is 20 sccm, and argon gas purity is ≥99.999%.

6. The method for preparing an in-situ self-reinforced dual-phase coating based on a multi-element amorphous precursor according to claim 5, characterized in that: The distance between the target and the pretreated zirconium alloy substrate is 5 mm. The sputtering current of the multi-component refractory alloy target is 300 ma, the sputtering current of the graphite target is 300~600 ma, and the sputtering power of the Si-Al composite target is 160~230 W.

7. The method for preparing an in-situ self-reinforced dual-phase coating based on a multi-element amorphous precursor according to claim 6, characterized in that: The temperature after cooling is 50 ~ 60℃.

8. The method for preparing an in-situ self-reinforced dual-phase coating based on a multi-element amorphous precursor according to claim 7, characterized in that: The deposition power supply for the multi-component refractory alloy target and the graphite target is a pulsed DC power supply, while the deposition power supply for the Si-Al composite target is a radio frequency power supply.

9. The application of the in-situ self-reinforcing dual-phase coating as described in claim 1 or 2 as an antioxidant material in a high-temperature environment of 1200~1300℃.

10. The application of the in-situ self-reinforcing dual-phase coating as described in claim 1 or 2 in the protection of nuclear fuel cladding materials.

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