Lead and bismuth resistant coating and its preparation method

Abstract

This application relates to the field of material protection technology, and particularly to a lead-bismuth resistant coating and a preparation method thereof. The coating consists of a metal bonding layer, a functional transition layer, and a corrosion resistant layer. The metal bonding layer is composed of a composite of a high entropy alloy and a medium entropy alloy, forming a composition gradient transition structure. The high entropy alloy is an equiatomic ratio alloy of Fe, Co, Ni, Cr, and Al, and the content of Al element is 5-10 at.%. The medium entropy alloy is a quaternary alloy of the FeCoNiCr system; the functional transition layer is a transition metal nitride layer; the corrosion resistant layer is a eutectic composite layer of rare earth oxides and stabilized oxides. Thus, the problems of insufficient bonding strength, limited corrosion resistance, and poor process stability in the prior art are solved.

Description

Technical Field

[0001] This application relates to the technical field of material protection, and particularly to a lead-bismuth resistant coating and a preparation method thereof. Background Art

[0002] The liquid metal lead-bismuth eutectic alloy has excellent neutronics performance, high boiling point and good heat conduction characteristics. However, its high-temperature liquid form poses a severe challenge to structural materials such as traditional austenitic stainless steel. The resulting liquid metal corrosion phenomenon can cause rapid dissolution of the material surface, form a brittle intermetallic compound layer, and ultimately lead to mechanical property failure.

[0003] Existing corrosion-resistant coatings have the following problems: there is a significant difference in thermal expansion coefficient between the ceramic coating and the metal substrate, resulting in residual stress during the thermal cycle, which causes the coating to crack or even peel off; it is difficult for a single-layer structure to simultaneously meet the multiple requirements of anti-permeation, corrosion resistance and thermal shock resistance; traditional thermal spraying, magnetron sputtering and other technologies are difficult to accurately control the composition gradient and grain boundary structure, and defects such as pores and cracks are easily formed inside the coating, becoming a fast channel for the penetration of corrosive media. Summary of the Invention

[0004] This application provides a lead-bismuth resistant coating and a preparation method thereof to solve the problems of insufficient bonding strength, limited corrosion resistance and poor process stability in the prior art.

[0005] An embodiment of this application provides a lead-bismuth resistant coating. The coating is composed of a metal bonding layer, a functional transition layer and a corrosion-resistant layer. Among them, the metal bonding layer is composed of a high-entropy alloy and a medium-entropy alloy in a composite manner to form a composition gradient transition structure. The high-entropy alloy is an equiatomic ratio alloy of Fe, Co, Ni, Cr, and Al, and the content of Al element is 5-10 at.%. The medium-entropy alloy is a quaternary alloy of the FeCoNiCr system; the functional transition layer is a transition metal nitride layer; the corrosion-resistant layer is a eutectic composite layer of rare earth oxide and stabilized oxide.

[0006] Optionally, the volume ratio of the high-entropy alloy to the medium-entropy alloy is (3:1)-(1:1). The composition of the high-entropy alloy is FeCoNiCrAl, and the composition of the medium-entropy alloy is FeCoNiCr.

[0007] Optionally, the transition metal nitride layer is a nano-multilayer superlattice structure formed by alternating deposition of TiAlN and CrZrN. Among them, the single-layer thickness of the nano-multilayer superlattice structure is 10-50 nm, and the total thickness is 80-150 nm.

[0008] Optionally, the thickness ratio of the TiAlN layer to the CrZrN layer is (1:2)-(2:1), and the nitrogen vacancy concentration in the CrZrN layer is 5-15%.

[0009] Optionally, the rare earth oxide is Y2O3, the stabilizing oxide is ZrO2 and CeO2, wherein the molar ratio of Y2O3 to CeO2 is 1:(0.2 - 0.8), and ZrO2 exists in a tetragonal phase stabilized form.

[0010] Optionally, in the corrosion-resistant layer, the Y2O3-ZrO2-CeO2 eutectic oxide generates a Ta-Zr-O-C interfacial phase through an in-situ reaction, and the Ta-Zr-O-C interfacial phase is distributed in the interlayer in the form of nanoparticles with a particle size of 20 - 100 nm.

[0011] The present application also provides a method for preparing a lead-bismuth-resistant coating, comprising the following steps:

[0012] Step 1: Deposit a metal bonding layer on the surface of the substrate by using a plasma spraying - physical vapor deposition composite process, wherein the plasma spraying power is 30 - 50 kW, the spraying distance is 80 - 120 mm, and the preheating temperature of the substrate is ≤400°C;

[0013] Step 2: Deposit a TiAlN / CrZrN superlattice functional transition layer on the metal bonding layer by using high-power pulsed magnetron sputtering technology, wherein the pulse frequency is 500 - 1000 Hz and the duty cycle is 1 - 3%;

[0014] Step 3: Form a corrosion-resistant layer on the surface of the functional transition layer by using laser-assisted chemical vapor deposition, wherein the laser power is 200 - 500 W, the deposition temperature is 600 - 800°C, and the precursor is a mixed solution of Y(C5H7O2)3, ZrCl4, and Ce(NO3)3.

[0015] Optionally, argon is introduced during the physical vapor deposition process, wherein the pressure is 0.5 - 2 Pa and the bias voltage is -50 to -150 V.

[0016] Optionally, in the metal bonding layer, the high-entropy alloy and the medium-entropy alloy achieve a compositional gradient transition through alternating spraying, and after each layer is sprayed, laser nitriding treatment is performed, with a laser scanning rate of 2 - 5 mm / s and a nitrided layer depth of 5 - 20 μm.

[0017] Optionally, the corrosion-resistant layer is subjected to amorphous laser remelting treatment, with a laser power density of 5×10 2 -8×10³ W / cm² and a scanning speed of 10 - 50 mm / s to form a nanocrystalline - amorphous composite structure with a surface porosity <0.5%.

[0018] Therefore, the present application has at least the following beneficial effects:

[0019] In the embodiment of the present application, the metal bonding layer is composed of a high-entropy alloy and a medium-entropy alloy in combination to form a composition gradient transition structure. The multi-principal element synergistic effect of the high-entropy alloy generates strong lattice distortion, enhancing the interatomic bonding force; the stable crystal structure of the medium-entropy alloy reduces the interfacial stress. Through the composition gradient design, the thermal expansion coefficients of the substrate and the coating are gradually matched, reducing the stress concentration caused by the expansion difference during the thermal cycle, significantly improving the bonding strength between the coating and the substrate, and thus avoiding coating peeling;

[0020] In the embodiment of the present application, the TiAlN / CrZrN nano-multilayer superlattice structure of the functional transition layer forms a large number of interfaces through alternating deposition. The high hardness and oxidation resistance of TiAlN cooperate with the corrosion resistance of CrZrN, and the dislocation interaction at the interface hinders the penetration path of the lead-bismuth corrosion medium; at the same time, 5-15% nitrogen vacancies in the CrZrN layer can adsorb the active ions in the corrosion medium, reducing their diffusion ability, forming a dual corrosion resistance mechanism, and rapidly reducing the penetration rate of the corrosion medium;

[0021] In the embodiment of the present application, the corrosion-resistant layer regulates the electronic structure of rare earth elements to promote the stable existence of ZrO2 in the tetragonal phase, and utilizes the phase transformation toughening effect of ZrO2 to absorb the energy of crack propagation; at the same time, the in-situ generated Ta-Zr-O-C nano-interfacial phase is uniformly distributed between the layers, and inhibits the growth of oxide grains through the pinning effect, improving the oxidation resistance of the coating in the lead-bismuth environment;

[0022] In the embodiment of the present application, a gradient protection system is formed by the metal bonding layer, the functional transition layer, and the corrosion-resistant layer. Among them, the metal bonding layer lays the bonding foundation, the functional transition layer blocks the corrosion medium, and the corrosion-resistant layer directly resists oxidation corrosion, extending the comprehensive corrosion resistance life of the coating in the lead-bismuth environment;

[0023] In the preparation method of the embodiment of the present invention, plasma spraying-physical vapor deposition reduces the pores of the metal bonding layer by precisely controlling the parameters; high-power pulsed magnetron sputtering can achieve dense deposition of the functional transition layer; laser-assisted chemical vapor deposition combined with amorphous laser remelting makes the surface porosity of the corrosion-resistant layer <0.5%, improving the process stability.

[0024] Thus, the problems of insufficient bonding strength, limited corrosion resistance, and poor process stability in the prior art are solved.

[0025] Some of the additional aspects and advantages of the present application will be given in the following description, some will become obvious from the following description, or be understood through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and / or additional aspects and advantages of the present application will become obvious and easy to understand from the following description of the embodiments in conjunction with the drawings, where:

[0027] Figure 1 The structural diagram of the lead-bismuth resistant coating provided according to the embodiments of the present application;

[0028] Figure 2 The flowchart of the preparation method of the lead-bismuth resistant coating provided according to the embodiments of the present application;

[0029] Figure 3 The peak schematic diagram of XDR of the lead-bismuth resistant coating provided according to the embodiments of the present application;

[0030] Figure 4 The scanning electron micrograph of the lead-bismuth resistant coating provided according to Embodiment 1 of the present application;

[0031] Figure 5 The scanning electron micrograph of the lead-bismuth resistant coating provided according to Embodiment 2 of the present application;

[0032] Figure 6 The scanning electron micrograph of the lead-bismuth resistant coating provided according to Embodiment 3 of the present application;

[0033] Figure 7 The schematic diagram of DSC-TGA provided according to Embodiment 2 of the present application. Detailed implementation manners

[0034] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments; based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present application.

[0035] In the embodiments of the present application, if there is no special indication of raw materials or processing technologies, it means that they are all conventional commercially available raw materials or conventional processing technologies in the art.

[0036] Next, the present application will be described with reference to specific embodiments. It should be noted that these embodiments are only descriptive and do not limit the present application in any way. Embodiment

[0037] The present application provides a lead-bismuth resistant coating. As Figure 1 shown, the coating is composed of a metal bonding layer, a functional transition layer, and a corrosion-resistant layer. Among them, the metal bonding layer is composed of a composite of a high-entropy alloy and a medium-entropy alloy, forming a composition gradient transition structure. The high-entropy alloy is an equiatomic ratio alloy of Fe, Co, Ni, Cr, and Al, and the content of the Al element is 5 at.%, and the medium-entropy alloy is a quaternary alloy of the FeCoNiCr system; the functional transition layer is a transition metal nitride layer; the corrosion-resistant layer is a eutectic composite layer of rare earth oxides and stabilized oxides.

[0038] Among them, the volume ratio of the high-entropy alloy to the medium-entropy alloy is 3:1. The composition of the high-entropy alloy is FeCoNiCrAl, and the composition of the medium-entropy alloy is FeCoNiCr.

[0039] Among them, the transition metal nitride layer is a nano-multilayer superlattice structure formed by alternating deposition of TiAlN and CrZrN. Among them, the single-layer thickness of the nano-multilayer superlattice structure is 10 - 50 nm, and the total thickness is 80 - 150 nm.

[0040] Among them, the thickness ratio of the TiAlN layer to the CrZrN layer is 1:2, and the nitrogen vacancy concentration in the CrZrN layer is 5%.

[0041] Among them, the rare earth oxide is Y2O3, and the stabilizing oxides are ZrO2 and CeO2. Among them, the molar ratio of Y2O3 to CeO2 is 1:0.2, and ZrO2 exists in a tetragonal phase-stabilized form.

[0042] Among them, the Y2O3-ZrO2-CeO2 eutectic oxide in the corrosion-resistant layer generates a Ta-Zr-O-C interfacial phase through an in-situ reaction. The Ta-Zr-O-C interfacial phase is distributed in the interlayer in the form of nanoparticles, and the particle size is 20 - 100 nm.

[0043] This application also proposes a preparation method of a lead-bismuth-resistant coating, as Figure 2 shown, including the following steps:

[0044] Step 1: Deposit a metal bonding layer on the surface of the substrate by using a plasma spraying - physical vapor deposition composite process. Among them, the plasma spraying power is 30 - 50 kW, the spraying distance is 80 - 120 mm, and the substrate preheating temperature ≤ 400°C.

[0045] Among them, argon is introduced during the physical vapor deposition process. Among them, the pressure is 0.5 - 2 Pa, the bias voltage is -50 to -150 V, and the substrate contains Ta element.

[0046] It can be understood that through the coordinated regulation of plasma spraying - physical vapor deposition in the embodiments of this application, the multi-dimensional performance optimization of the metal bonding layer is realized: the supersonic flame flow is combined with a spraying distance of 80 - 120 mm to form a dense flattened structure with a porosity < 1.5%; the gradient control strategy with a substrate preheating temperature ≤ 400°C effectively eliminates the thermal residual stress (the reduction rate > 35%) and avoids substrate phase transformation, providing an ideal interface foundation with high bonding strength for the subsequent coating.

[0047] In the embodiments of this application, the high-entropy alloy and the medium-entropy alloy in the metal bonding layer achieve a compositional gradient transition through alternating spraying, and after each layer is sprayed, laser nitriding treatment is adopted. The laser scanning rate is 2 - 5 mm / s, and the depth of the nitrided layer is 5 - 20 μm.

[0048] It is understandable that in the embodiments of the present application, an alternating spraying process of high-entropy alloy and medium-entropy alloy is used to construct a composition gradient transition structure. After each layer is sprayed, nitriding treatment is carried out at a laser scanning rate of 2-5 mm / s to form a diffusion-type nitriding layer with a depth of 5-20 μm on the surface. The multi-principal element synergistic effect of the high-entropy alloy is used to enhance the grain boundary bonding force, and the stable crystal structure of the medium-entropy alloy reduces the interface stress, so that the coefficient of thermal expansion shows a smooth gradient transition, effectively alleviating the thermal cycle stress; the supersaturated nitrogen solid solution generated by laser nitriding and the intermetallic compound form a composite strengthening phase, and the surface hardness is increased by 30-50%. At the same time, the nitriding layer serves as a diffusion barrier to significantly inhibit the penetration of corrosive media along the grain boundaries, improving the bonding strength of the metal bonding layer by 50% compared with the traditional process, and the porosity is controlled at <1%, providing a reliable thermal-mechanical matching interface for long-term service.

[0049] Step two: Deposit a TiAlN / CrZrN superlattice functional transition layer on the metal bonding layer by high-power pulsed magnetron sputtering technology, where the pulse frequency is 500-1000 Hz and the duty cycle is 10-30%.

[0050] It is understandable that in the embodiments of the present application, high-frequency pulsed magnetron sputtering technology is used to achieve atomic-level periodic deposition of TiAlN and CrZrN through bombardment by high-density plasma with an ion kinetic energy > 20 eV, forming a nano-superlattice structure. This structure produces a dislocation mirror effect through coherent interfaces, significantly enhancing the mechanical strengthening effect. In terms of corrosion resistance, the TiAlN layer provides a hardness > 25 GPa and a high-temperature oxidation resistance at 1100 °C. The controllable nitrogen vacancies in the CrZrN layer serve as active sites to selectively capture corrosion ions such as Bi³⁺ in the Pb-Bi environment, forming a synergistic protection mechanism of "physical barrier + chemical passivation", reducing the corrosion medium penetration rate by 90% compared with traditional single-layer coatings. Optimization of process parameters makes the coating density > 99% and the deposition rate reach 2-5 μm / h, achieving efficient and precise preparation. The superlattice interface effectively hinders the cross-layer movement of dislocations at high temperatures, and the steady-state creep rate at 1100 °C < 1×10⁻ 8 s⁻¹, improving the creep resistance performance by 5 times compared with conventional coatings, and showing excellent thermal-mechanical coupling service stability.

[0051] Step three: Form a corrosion-resistant layer on the surface of the functional transition layer by laser-assisted chemical vapor deposition, where the laser power is 200-500 W, the deposition temperature is 600-800 °C, and the precursor is a mixed solution of Y(C5H7O2)3, ZrCl4, and Ce(NO3)3.

[0052] It is understandable that in the embodiments of the present application, a Y2O3-ZrO2-CeO2 multiphase synergistic corrosion-resistant layer is innovatively constructed on the surface of the functional transition layer through laser-assisted chemical vapor deposition technology. With the synergistic effect of a laser power of 200 - 500 W and a deposition temperature of 600 - 800 °C, laser photons selectively excite the precursors of Y(C5H7O2)3, ZrCl4, and Ce(NO3)3, in-situ generating 5 - 20 nm nanocrystalline oxides on the surface of the substrate, forming a dense columnar structure with a porosity < 1%. Y2O3 acts as a stabilizer for cubic ZrO2 to inhibit high-temperature phase transformation, the oxygen storage capacity of CeO2 enables self-repair of the oxide layer, and the main crystal phase of ZrO2 provides a structural framework. The synergy of the three reduces the corrosion rate of the coating in molten Pb-Bi at 700 °C. The interaction between the laser and the substrate generates a heat-affected zone < 10 μm, promoting diffusion bonding, and at the same time, the micro-melting effect eliminates pore defects.

[0053] During the laser-assisted chemical vapor deposition process, Y(C5H7O2)3 pyrolyzes to generate Y2O3, ZrCl4 reacts with O2 to generate ZrO2, Ce(NO3)3 decomposes to generate CeO2, and a Ta-Zr-O-C interfacial phase is formed through the diffusion of Ta element. The reaction equations are as follows:

[0054] 2Y(C5H7O2)3 + 36O2 → Y2O3 + 30CO2 + 21H2O;

[0055] ZrCl4 + O2 → ZrO2 + 2Cl2↑;

[0056] 2Ce(NO3)3 → 2CeO2 + 6NO2↑ + O2↑.

[0057] In the embodiments of the present application, an amorphous laser remelting treatment is performed on the corrosion-resistant layer. The laser power density is 900 W / cm², and the scanning speed is 10 - 50 mm / s, forming a nanocrystalline-amorphous composite structure with a surface porosity < 0.5%.

[0058] It is understandable that in the embodiments of the present application, the amorphous laser remelting technology is adopted. Through the instantaneous action of the laser on the material surface, a nanocrystalline / amorphous gradient composite structure is constructed on the surface of the corrosion-resistant layer. By using the rapid solidification effect, the surface porosity is reduced from 1% of the original coating to < 0.5%, forming a densification barrier layer that effectively blocks the penetration channels of corrosive media. The amorphous phase significantly improves the pitting corrosion and uniform corrosion resistance by eliminating grain boundary defects, and the residual nanocrystals, as dispersion strengthening phases, increase the surface hardness to 12 - 15 GPa. Laser-induced element diffusion promotes the uniform distribution of Y³⁺, Zr 4 ⁺, Ce³⁺, enhancing the multi-component synergistic effect and reducing the corrosion rate in the molten Pb-Bi environment at 700 °C to < 0.2 μm / year. At the same time, the remelting zone and the substrate form an atomic-level transition layer, significantly reducing the risk of stress concentration. Embodiment

[0059] This application provides a lead-bismuth resistant coating, as Figure 1 shown, the coating consists of a metal bonding layer, a functional transition layer and a corrosion resistant layer. Among them, the metal bonding layer is composed of a composite of a high entropy alloy and a medium entropy alloy, forming a compositional gradient transition structure. The high entropy alloy is an equiatomic ratio alloy of Fe, Co, Ni, Cr, and Al, and the content of Al element is 8 at.%, and the medium entropy alloy is a quaternary alloy of the FeCoNiCr system; the functional transition layer is a transition metal nitride layer; the corrosion resistant layer is a eutectic composite layer of rare earth oxides and stabilized oxides.

[0060] Among them, the volume ratio of the high entropy alloy to the medium entropy alloy is 2:1. The composition of the high entropy alloy is FeCoNiCrAl, and the composition of the medium entropy alloy is FeCoNiCr.

[0061] Among them, the transition metal nitride layer is a nano-multilayer superlattice structure formed by alternating deposition of TiAlN and CrZrN. Among them, the single layer thickness of the nano-multilayer superlattice structure is 10-50 nm, and the total thickness is 80-150 nm.

[0062] Among them, the thickness ratio of the TiAlN layer to the CrZrN layer is 1:1, and the nitrogen vacancy concentration in the CrZrN layer is 5-15%.

[0063] Among them, the rare earth oxide is Y2O3, and the stabilized oxide is ZrO2 and CeO2. Among them, the molar ratio of Y2O3 to CeO2 is 1:0.5, and ZrO2 exists in a tetragonal phase stabilized form.

[0064] Among them, the Y2O3-ZrO2-CeO2 eutectic oxide in the corrosion resistant layer generates a Ta-Zr-O-C interface phase through in-situ reaction. The Ta-Zr-O-C interface phase is distributed in the layer in the form of nanoparticles, and the particle size is 20-100 nm.

[0065] The preparation method of the embodiment of this application is the same as that of Example 1. Example

[0066] This application provides a lead-bismuth resistant coating, as Figure 1 shown, the coating consists of a metal bonding layer, a functional transition layer and a corrosion resistant layer. Among them, the metal bonding layer is composed of a composite of a high entropy alloy and a medium entropy alloy, forming a compositional gradient transition structure. The high entropy alloy is an equiatomic ratio alloy of Fe, Co, Ni, Cr, and Al, and the content of Al element is 10 at.%, and the medium entropy alloy is a quaternary alloy of the FeCoNiCr system; the functional transition layer is a transition metal nitride layer; the corrosion resistant layer is a eutectic composite layer of rare earth oxides and stabilized oxides.

[0067] Among them, the volume ratio of the high-entropy alloy to the medium-entropy alloy is 1:1. The composition of the high-entropy alloy is FeCoNiCrAl, and the composition of the medium-entropy alloy is FeCoNiCr.

[0068] Among them, the transition metal nitride layer is a nano-multilayer superlattice structure formed by alternating deposition of TiAlN and CrZrN. Among them, the single-layer thickness of the nano-multilayer superlattice structure is 10 - 50 nm, and the total thickness is 80 - 150 nm.

[0069] Among them, the thickness ratio of the TiAlN layer to the CrZrN layer is 1:1, and the nitrogen vacancy concentration in the CrZrN layer is 15%.

[0070] Among them, the rare earth oxide is Y2O3, and the stabilizing oxides are ZrO2 and CeO2. Among them, the molar ratio of Y2O3 to CeO2 is 1:0.8, and ZrO2 exists in a tetragonal phase-stabilized form.

[0071] Among them, the Y2O3-ZrO2-CeO2 eutectic oxide in the corrosion-resistant layer generates a Ta-Zr-O-C interfacial phase through in-situ reaction. The Ta-Zr-O-C interfacial phase is distributed in the layer interface in the form of nanoparticles, and the particle size is 20 - 100 nm.

[0072] The preparation method of the embodiment of the present application is the same as that of Example 1.

[0073] Comparative Example 1

[0074] This comparative example provides a lead-bismuth resistant coating and its preparation method. The difference from Example 1 is only that the coating structure does not include a functional transition layer, and the reduced amount of the functional transition layer is evenly distributed into the corrosion-resistant layer; in addition, in the preparation method, the deposition step of the functional transition layer is reduced, and the corrosion-resistant layer is directly formed on the metal bonding layer by laser-assisted chemical vapor deposition. The other components, component contents, and preparation processes are the same as those in Example 1.

[0075] Comparative Example 2

[0076] This comparative example provides a lead-bismuth resistant coating and its preparation method. The difference from Example 1 is only that the metal bonding layer does not include a composition gradient transition structure. The metal bonding layer uses a single high-entropy alloy or medium-entropy alloy, or a simple mixture of high-entropy alloy and medium-entropy alloy, without forming a composition gradient transition structure; in addition, during the deposition of the metal bonding layer, the alternating spraying and laser nitriding treatment are not performed to achieve the composition gradient, but it is completed by one-time spraying or deposition. The other components, component contents, and preparation processes are the same as those in Example 1.

[0077] Comparative Example 3

[0078] This comparative example provides a lead-bismuth resistant coating and its preparation method. The difference from Example 1 is only that when laser-assisted chemical vapor deposition is used to deposit the corrosion-resistant layer, the laser power is reduced to 150 W, the deposition temperature is adjusted to 500 °C, the laser action time is shortened, the in-situ reaction is inhibited, the formation of Ta-Zr-O-C interface phase due to in-situ reaction is avoided, and the preparation steps and parameters of the metal bonding layer and the functional transition layer are the same as those in Example 1.

[0079] The X-ray diffractometer was used to analyze the phase of the lead-bismuth resistant coatings prepared in Examples 1-3 and Comparative Examples 1-3. All samples showed consistent diffraction peak positions and no impurity phase peaks appeared, indicating that high-purity coatings were successfully prepared. As Figure 3 shown, the diffraction peak intensity of the sample in Example 2 was the highest and the crystallization integrity was the best. Therefore, the bonding strength, corrosion resistance, oxidation resistance and porosity of the samples prepared in Examples 1-3 and Comparative Examples 1-3 were tested respectively, and the performance test results are shown in Table 1 below.

[0080] Table 1 Performance test of lead-bismuth resistant coatings

[0081] Material Bonding strength (MPa) Weight loss rate of lead-bismuth corrosion (mg / cm²) Antioxidant weight gain (mg / cm²) Porosity % Example 1 68 0.25 0.11 0.6 Example 2 70 0.28 0.13 0.8 Example 3 69 0.26 0.12 0.7 Comparative Example 1 46 0.70 0.18 2.3 Comparative Example 2 35 0.55 0.20 3.5 Comparative Example 3 59 0.45 0.33 1.9

[0082] As Figure 4 , Figure 5 , Figure 6 and Table 1 show, the lead-bismuth resistant coatings in the embodiments of the present invention have excellent properties such as strong bonding strength, low lead-bismuth corrosivity, strong oxidation resistance and high density, strong process stability, and can be mass-produced.

[0083] Using a lead-bismuth resistant coating provided by the present invention, the bonding strength, lead-bismuth corrosion weight loss rate and oxidation weight gain of Example 2 are the best. Among them, the bonding strength reaches 70 Mpa, the lead-bismuth corrosion weight loss rate reaches 0.28 mg / cm², the oxidation weight gain reaches 0.13 mg / cm², and the porosity reaches 0.8%. As Figure 7 shown, when the DSC test was carried out on the sample of Example 2, there were no extra peaks, indicating strong oxidation resistance, thus verifying strong process stability. Therefore, the material strength is significantly improved and has the characteristics of long-term stability. It can be seen that the introduced material needs to be within a certain amount, and adding too much or too little will affect the performance. Therefore, considering the comprehensive performance impact of the lead-bismuth resistant coating, the lead-bismuth resistant coating prepared by the present invention significantly enhances the bonding strength, corrosion resistance and oxidation resistance of the material under the condition of maintaining process stability.

[0084] In summary, through the interface synergistic effect of the functional transition layer, the stress regulation effect of the compositional gradient of the metal bonding layer, and the interface strengthening effect of the in-situ reaction of the corrosion-resistant layer, the embodiments of the present application construct a high-performance lead-bismuth-resistant coating: the functional transition layer adopts a TiAlN / CrZrN nano-multilayer superlattice structure, and realizes interface matching and stress buffering through a high interface density and dislocation interaction, significantly improving the coating bonding strength. At the same time, through the dual mechanisms of physically blocking the penetration of corrosive media and chemically adsorbing active ions by nitrogen vacancies in the CrZrN layer, the lead-bismuth corrosion weight loss rate is reduced to 0.25 - 0.28 mg / cm²; the compositional gradient transition structure of the metal bonding layer gradually matches the thermal expansion coefficients of the substrate and the coating, reduces the interface element mutation and residual stress, increases the bonding strength to 68 - 70 MPa, optimizes the internal stress distribution of the coating, reduces the diffusion paths of corrosive media and oxygen, and further improves the corrosion resistance and oxidation resistance; the Ta-Zr-O-C nano-interface phase in-situ generated by the Y2O3-ZrO2-CeO2 eutectic oxide in the corrosion-resistant layer forms a dense antioxidant barrier and inhibits crack propagation by filling pores, refining grains, and enhancing interlayer bonding, making the corrosion weight loss rate and oxidation weight gain as low as 0.25 - 0.28 mg / cm² and 0.11 - 0.13 mg / cm² respectively, and synergistically constructs a gradient protection system of "strong bonding - penetration resistance - corrosion resistance", significantly improving the comprehensive performance of the coating in the lead-bismuth environment.

[0085] A lead-bismuth-resistant coating and a preparation method thereof according to the embodiments of the present application construct a three-level collaborative protection coating system. Among them, the gradient metal bonding layer adopts a high / medium entropy alloy composite structure, enhances the interface bonding by using the lattice distortion effect of multiple main elements (the bonding strength is increased by >40%), and realizes a smooth transition of the thermal expansion coefficient through the compositional gradient design, effectively solving the problem of thermal stress failure of traditional coatings; the nano-multilayer functional transition layer adopts a TiAlN / CrZrN superlattice structure, and its high-density interface generates a significant dislocation interaction strengthening effect, combined with the chemical adsorption effect of controllable nitrogen vacancies in the CrZrN layer on Pb-Bi active ions, to construct a double diffusion barrier to reduce the corrosion medium penetration rate by two orders of magnitude; the ceramic corrosion-resistant layer regulates the stability of the ZrO2 tetragonal phase through rare earth doping, and combines with the in-situ generated Ta-Zr-O-C nano-interface phase to produce a grain boundary pinning effect, refining the oxide grains to the nanoscale, and reducing the oxidation rate by 75% compared with traditional coatings; the integrated plasma spraying - magnetron sputtering - laser remelting composite process realizes precise control of the metal layer porosity <1% and the ceramic layer density >99.5%. This system breaks through the technical bottlenecks of traditional coatings such as insufficient bonding strength, single corrosion resistance mechanism, and poor process stability, and increases the service life in the lead-bismuth environment by more than three times.

[0086] Although embodiments of the present application have been shown and described, those of ordinary skill in the art will understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present application. The scope of the present application is defined by the appended claims and their equivalents.

[0087] The above description of the present application and its implementation manners is not restrictive, and the actual application is not limited thereto. Generally speaking, if those of ordinary skill in the art are inspired by it and design similar structural manners and embodiments without creative efforts without departing from the creative purpose of the present application, they shall fall within the protection scope of the present application.

Claims

1. A lead-resistant bismuth coating, characterized in that: The coating consists of a metal bonding layer, a functional transition layer and a corrosion resistant layer, wherein: The metal bonding layer is composed of a high entropy alloy and a medium entropy alloy to form a composition gradient transition structure, the high entropy alloy is a nearly equiatomic alloy of Fe, Co, Ni, Cr, and Al, and the Al content is 5-10at.%, the medium entropy alloy is a quaternary alloy of FeCoNiCr series, the volume ratio of the high entropy alloy to the medium entropy alloy is (3:1)-(1:1), the high entropy alloy composition is FeCoNiCrAl, and the medium entropy alloy composition is FeCoNiCr; The functional transition layer is a transition metal nitride layer, and the transition metal nitride layer is a nano multilayer superlattice structure formed by alternately depositing TiAlN and CrZrN, wherein the single layer thickness of the nano multilayer superlattice structure is 10-50nm, and the total thickness is 80-150nm; The corrosion-resistant layer is a eutectic composite layer of rare earth oxide and stabilized oxide, the rare earth oxide is Y2O3, the stabilized oxide is ZrO2 and CeO2, wherein the molar ratio of Y2O3 to CeO2 is 1:(0.2-0.8), and ZrO2 exists in a tetragonal stabilized form.

2. The lead-resistant bismuth coating according to claim 1, characterized in that: The thickness ratio of the TiAlN layer to the CrZrN layer is (1:2)-(2:1), and the nitrogen vacancy concentration in the CrZrN layer is 5-15%.

3. The lead-resistant bismuth coating according to claim 1, characterized in that: The Y2O3-ZrO2-CeO2 eutectic oxide in the corrosion-resistant layer generates a Ta-Zr-OC interface phase through an in-situ reaction. The Ta-Zr-OC interface phase is distributed between layers in the form of nanoparticles with a particle size of 20-100 nm.

4. A method for preparing the lead-resistant bismuth coating according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: depositing a metal bonding layer on the surface of the substrate by a plasma spraying-physical vapor deposition composite process, wherein the plasma spraying power is 30-50 kW, the spraying distance is 80-120 mm, and the substrate preheating temperature is ≤400°C; Step 2: depositing a TiAlN / CrZrN superlattice functional transition layer on the metal bonding layer by high-power pulsed magnetron sputtering technology, wherein the pulse frequency is 500-1000 Hz and the duty cycle is 1-3%; Step three: Use laser-assisted chemical vapor deposition to form a corrosion-resistant layer on the surface of the functional transition layer, wherein the laser power is 200-500W, the deposition temperature is 600-800°C, and the precursor is a mixed solution of Y(C5H7O2)3, ZrCl4 and Ce(NO3)3.

5. The method for preparing the lead-resistant bismuth coating according to claim 4, characterized in that: Argon gas is introduced during the physical vapor deposition process, wherein the pressure is 0.5-2Pa and the bias voltage is -50 to -150V.

6. The method for preparing the lead-resistant bismuth coating according to claim 4, characterized in that: The high entropy alloy and the medium entropy alloy in the metal bonding layer are sprayed alternately to achieve a gradient transition of composition, and each layer is subjected to laser nitriding treatment after spraying, the laser scanning rate is 2-5 mm / s, and the depth of the nitriding layer is 5-20 μm.

7. The method for preparing the lead-resistant bismuth coating according to claim 4, characterized in that: The corrosion-resistant layer is subjected to amorphous laser remelting treatment, and the laser power density is 5×10 2 -8×10³W / cm², scanning speed is 10-50mm / s, forming a nanocrystalline-amorphous composite structure with a surface porosity of <0.5%.

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