High-entropy alloy coating resistant to high-temperature lead and bismuth corrosion under oxygen-deficient condition and preparation method of high-entropy alloy coating

Abstract

The invention provides a high-entropy alloy coating resistant to high-temperature lead and bismuth corrosion under the oxygen-deficient condition and a preparation method of the high-entropy alloy coating, and belongs to the technical field of coatings. The high-entropy alloy coating comprises the following elements in percentage by weight: 15 to 30 percent of Al, 15 to 30 percent of Fe, 15 to 30 percent of Cr and 15 to 30 percent of Mo. The preparation method of the high-entropy alloy coating comprises the following steps: pre-treating a large-curvature pipe; an AlFeCrMo high-entropy alloy target material is obtained through a powder metallurgy method; and the high-entropy alloy coating is prepared on the surface of the pretreated large-curvature pipe through the single-target radio frequency magnetron sputtering technology. According to the preparation method of the high-entropy alloy coating resistant to high-temperature lead and bismuth corrosion under the oxygen-deficient condition, provided by the invention, the prepared high-entropy alloy coating has relatively high corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a high-entropy alloy coating resistant to high-temperature lead-bismuth corrosion under oxygen-deficient conditions and its preparation method. Background Technology

[0002] Lead-bismuth reactors have attracted attention and importance due to their unique advantages in neutron economy, thermal-hydraulic properties, chemical stability, safety, and multi-environment applications, making them a key focus of advanced nuclear energy system research. As a critical material within the reactor, the fuel element cladding is subjected to extreme environments such as corrosion from high-temperature liquid lead-bismuth (Pb-Bi) coolant and intense radiation. Its material properties directly affect the reactor's economy, safety, and stability. Ferritic / martensitic steels (F / M T91, HT9, EP823, etc.) have become the primary cladding material promoted both domestically and internationally due to their good high-temperature strength, radiation stability, fuel compatibility, ease of welding, and ease of manufacturing.

[0003] Lead-bismuth reactor cladding materials operate in harsh, high-temperature liquid Pb-Bi environments, and their corrosion resistance is a critical factor limiting their application. During prolonged contact between ferritic / martensitic steel and high-temperature liquid Pb-Bi, oxidative corrosion, dissolution corrosion, and Pb-Bi coolant erosion lead to severe liquid metal corrosion and embrittlement problems in the cladding materials.

[0004] Currently, the main strategies for reducing lead-bismuth corrosion are structural material composition modification, oxygen concentration control, and surface coating technology. Among these, surface coating technology can improve the surface properties of structural materials without sacrificing other properties of the steel structure. Furthermore, coating material systems can be designed and prepared relatively independently, without significantly affecting the processing and structural performance of existing fuel element cladding or core structural materials. Therefore, surface coating technology is considered internationally to be one of the most promising methods for solving the corrosion problem of lead-bismuth alloys on steel structures. Combined with existing dynamic oxygen content control technology, it is the easiest method to achieve engineering application in the short to medium term, making it highly competitive.

[0005] The corrosion behavior of iron-steel in lead-bismuth alloys is extremely sensitive to dissolved oxygen content. Due to its inherent self-healing ability, the metallic elements dissolved in the lead-bismuth alloy can combine with oxygen to form an in-situ protective oxide film, inhibiting subsequent oxidation and dissolution processes and achieving corrosion protection. However, when the corrosion temperature exceeds 550℃, the oxides will grow too rapidly and peel off under growth stress and high temperature, failing to maintain stable corrosion resistance. Furthermore, in oxygen-deficient environments, when the oxygen concentration is insufficient to support the formation of an in-situ oxide film, metallic elements such as Fe and Cr in the steel will continuously dissolve, causing material consumption. Simultaneously, material embrittlement occurs during direct contact with lead-bismuth, jeopardizing the safe service life of structural components.

[0006] High-entropy alloys are a material system based on a novel design concept, in which each major element has a high atomic percentage, with each component ranging from 5 at.% to 35 at.%. Due to their multiple components, high-entropy alloys exhibit "collective characteristics." The thermodynamic high-entropy effect of multiple principal elements, the lattice distortion effect in the structure, the hysteresis diffusion effect in the kinetics, and the cocktail effect in performance make high-entropy alloys superior to traditional alloys in terms of mechanical properties, corrosion resistance, oxidation resistance, and radiation resistance. They have been listed by the U.S. National Academy of Sciences as one of the most cutting-edge materials for research, showing potential as novel cladding materials and cladding surface coating materials, which has attracted great attention from many researchers in the nuclear field.

[0007] By combining the flexible design features of high-entropy alloy composition with the application environment of lead-bismuth, and supplementing it with adaptive coating preparation technology, this method can specifically suppress the dissolution and corrosion problems of ferritic / martensitic steel in high-temperature liquid lead-bismuth under high temperature and oxygen-deficient conditions. It has solid technical feasibility and scientifically advanced applicability. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a high-entropy alloy coating with strong corrosion resistance under low oxygen conditions and high temperature lead-bismuth corrosion resistance, and the preparation method thereof.

[0009] To solve the above technical problems, the present invention provides a high-entropy alloy coating resistant to high-temperature lead-bismuth corrosion under oxygen-deficient conditions. The elements and contents of the high-entropy alloy coating are: Al 15-30 at.%, Fe 15-30 at.%, Cr 15-30 at.%, and Mo 15-30 at.%.

[0010] This invention also provides a method for preparing a high-entropy alloy coating resistant to high-temperature lead-bismuth corrosion under oxygen-deficient conditions, comprising the following steps: Pre-treatment of pipes with large curvature; AlFeCrMo high-entropy alloy targets were obtained using powder metallurgy. High-entropy alloy coatings were prepared on the surface of pretreated high-curvature pipes using single-target radio frequency magnetron sputtering technology.

[0011] Furthermore, the high-curvature pipe is a ferritic / martensitic steel pipe.

[0012] Furthermore, the diameter of the ferritic / martensitic steel pipe is 9 mm, with a tolerance range of ±0.03 mm.

[0013] Furthermore, the pretreatment of the large-curvature pipe includes: first performing ultrasonic cleaning on the large-curvature pipe 2 to 4 times, and then drying the cleaned large-curvature pipe.

[0014] Furthermore, the ultrasonic cleaning of the large-curvature pipe is performed using an ultrasonic cleaning device, with anhydrous ethanol as the cleaning solution and a cleaning time of 10-15 minutes.

[0015] Furthermore, the large curvature pipe is dried in a drying oven at a temperature of 50–70°C.

[0016] Furthermore, the preparation of the AlFeCrMo high-entropy alloy target includes sequentially mixing 15-30 at.% Al, 15-30 at.% Fe, 15-30 at.% Cr, and 15-30 at.% Mo, followed by hot pressing sintering, composition testing, and machining processes to obtain the AlFeCrMo high-entropy alloy target.

[0017] Furthermore, during the single-target RF magnetron sputtering process, the rotation speed of the large-curvature tube in the sputtering coating chamber is controlled at 10–25 r / min, the vacuum degree is controlled at 3–6 × 10⁻⁴ Pa, Ar with a purity of 99.999% is introduced to control the sputtering gas pressure at 0.5–0.6 Pa, the sputtering power is controlled at 500–700 W, the temperature of the large-curvature tube is controlled at room temperature at the beginning of sputtering, and the temperature of the large-curvature tube is controlled below 150°C during the sputtering process.

[0018] Furthermore, the high-entropy alloy coating prepared on the surface of the large-curvature pipe has a thickness of 4-6 μm.

[0019] This invention provides a high-entropy alloy coating resistant to high-temperature lead-bismuth corrosion under oxygen-deficient conditions and its preparation method. The high-entropy alloy coating is prepared on the surface of a large-curvature pipe using single-target radio frequency magnetron sputtering technology. The process parameters such as power, sputtering gas pressure, bias voltage, and sample rotation speed can be easily controlled, and the preparation process is flexible, energy-saving and efficient.

[0020] Furthermore, this invention provides a high-entropy alloy coating resistant to high-temperature lead-bismuth corrosion under oxygen-deficient conditions and its preparation method. By controlling the process parameters of single-target radio frequency magnetron sputtering and combining it with a homogeneous multilayer process route, stress release is achieved during the deposition of the AlFeCrMo high-entropy alloy system on the surface of pipes with large curvature radii. This effectively improves the compatibility between ferritic / martensitic steel and liquid lead-bismuth alloy under high-temperature, oxygen-deficient conditions, thereby depositing a highly dense AlFeCrMo high-entropy alloy coating on the surface of the ferritic / martensitic steel pipe substrate. Compared with traditional planar materials, this invention solves the technical problems of cracking and peeling of coatings on the surface of pipes with large curvature. Attached Figure Description

[0021] Figure 1 This invention provides a method for preparing a high-entropy alloy coating resistant to high-temperature lead-bismuth corrosion under oxygen-deficient conditions. Figure 2 This is a cross-sectional SEM image of the AlFeCrMo high-entropy alloy coating sample obtained in Example 4 of this invention after corrosion. Figure 3 The SEM image shows the cross-sectional morphology of an uncoated ferritic / martensitic steel pipe sample after corrosion, provided by this invention. Detailed Implementation

[0022] See Figure 1 The present invention provides a method for preparing a high-entropy alloy coating resistant to high-temperature lead-bismuth corrosion under oxygen-deficient conditions, comprising the following steps: Step 1) Pre-treat the pipe with large curvature.

[0023] The high-curvature pipe is a ferritic / martensitic steel pipe.

[0024] The diameter of the ferritic / martensitic steel pipe is 9 mm, with a tolerance range of ±0.03 mm.

[0025] The pretreatment of the large-curvature pipe includes: first, ultrasonic cleaning the large-curvature pipe 2 to 4 times, and then drying the cleaned large-curvature pipe.

[0026] Specifically, the ultrasonic cleaning of the large-curvature pipe is performed using an ultrasonic cleaning device, with anhydrous ethanol as the cleaning solution and a cleaning time of 10-15 minutes.

[0027] Specifically, the large curvature pipe is dried in a drying oven at a temperature of 50–70°C.

[0028] Step 2) Obtain AlFeCrMo high-entropy alloy target material using powder metallurgy.

[0029] The preparation of the AlFeCrMo high-entropy alloy target includes sequentially mixing 15-30 at.% Al, 15-30 at.% Fe, 15-30 at.% Cr, and 15-30 at.% Mo, followed by hot pressing sintering, composition testing, and machining processes to obtain the AlFeCrMo high-entropy alloy target.

[0030] Step 3) Use single-target radio frequency magnetron sputtering technology to prepare a high-entropy alloy coating on the surface of the pretreated large-curvature pipe.

[0031] In the single-target RF magnetron sputtering process, the rotation speed of the large-curvature tube in the sputtering coating chamber is controlled at 10-25 r / min, the vacuum degree is controlled at 3-6×10-4 Pa, Ar with a purity of 99.999% is introduced to control the sputtering gas pressure at 0.5-0.6 Pa, the sputtering power is controlled at 500-700 W, the temperature of the large-curvature tube is controlled at room temperature at the beginning of sputtering, and the temperature of the large-curvature tube is controlled below 150℃ during sputtering.

[0032] The high-entropy alloy coating prepared on the surface of the large-curvature pipe has a thickness of 4-6 μm.

[0033] The elements and their contents in the high-entropy alloy coating are as follows: Al 15-30 at.%, Fe 15-30 at.%, Cr 15-30 at.%, and Mo 15-30 at.%.

[0034] Under high temperature and low oxygen conditions, the Fe, Cr and other elements dissolved in lead and bismuth in ferritic / martensitic steel cannot combine with enough oxygen to form a protective oxide layer. Therefore, ferritic / martensitic steel is easily dissolved and consumed during long-term corrosion. Lead and bismuth erode into the interior of the ferritic / martensitic steel along the failure area, eventually leading to material failure.

[0035] This invention provides a method for preparing a high-entropy alloy coating resistant to high-temperature lead-bismuth corrosion under oxygen-deficient conditions. In the prepared AlFeCrMo high-entropy alloy coating, Fe and Cr elements are added. Fe and Cr elements are the same as the matrix elements of ferritic / martensitic steel, and their affinity effectively enhances the adhesion between the coating and the matrix. Furthermore, Fe and Cr elements prevent the diffusion of Fe and Cr elements from the matrix into the coating during lead-bismuth corrosion due to excessive elemental differences. The addition of Al element, as a strong oxide-forming element, is beneficial for the formation of a protective Al₂O₃ film and also promotes the formation of a Cr₂O₃ oxide film. The addition of Mo element helps increase the lattice distortion effect of the system, thereby promoting the formation of a dense, disordered structure or an amorphous encapsulated nanocrystalline structure, improving the corrosion resistance of the system.

[0036] Therefore, this invention provides a method for preparing a high-entropy alloy coating resistant to high-temperature lead-bismuth corrosion under oxygen-deficient conditions. An AlFeCrMo high-entropy alloy coating is formed on the surface of ferritic / martensitic steel. Firstly, it prevents direct contact between lead-bismuth and the ferritic / martensitic steel. Secondly, because the elements in this high-entropy alloy system have relatively low solubility in the high-temperature liquid lead-bismuth environment, and because the high-entropy alloy exhibits significant lattice distortion, it suppresses the elemental composition and microstructure of the alloy elements, resulting in low solubility in lead-bismuth. Furthermore, its inherent hysteresis diffusion effect inhibits the interdiffusion process, allowing the coating to exist stably in lead-bismuth. Moreover, a continuously distributed Cr2O3 protective oxide layer is generated during corrosion, continuously protecting the ferritic / martensitic steel and thus inhibiting failure caused by dissolution corrosion in oxygen-deficient conditions.

[0037] The following examples illustrate the high-entropy alloy coating resistant to high-temperature lead-bismuth corrosion under oxygen-deficient conditions and its preparation method provided by the present invention.

[0038] Example 1 1. Matrix preparation: The pipe used is ferritic / martensitic steel pipe, which is ultrasonically cleaned and then dried for later use.

[0039] The cleaning process uses ultrasonic cleaning equipment, and the cleaning solution is anhydrous ethanol. The cleaning time is 10 minutes. After cleaning twice, the product is dried in a 50℃ drying oven.

[0040] 2. Preparation of high-entropy alloy coatings: A high-entropy AlFeCrMo alloy target was obtained, and a coating was prepared using single-target radio frequency magnetron sputtering. The tubular sample was mounted in the sputtering chamber, with its rotation speed set to 10 r / min and a vacuum level of 0.3 × 10⁻⁶. -3 After Pa, high-purity Ar gas is introduced to maintain the sputtering pressure at 0.5 Pa, and the sputtering power is set to 500 W.

[0041] The AlFeCrMo high-entropy alloy coating contains 30 at.% Al, 25 at.% Fe, 25 at.% Cr, and 30 at.% Mo.

[0042] Example 2 1. Matrix preparation: The pipe used is ferritic / martensitic steel pipe, which is ultrasonically cleaned and then dried for later use.

[0043] The cleaning process uses ultrasonic cleaning equipment, anhydrous ethanol as the cleaning solution, and the cleaning time is 15 minutes. After cleaning three times, the product is dried in a drying oven at 70℃.

[0044] 2. Preparation of high-entropy alloy coatings: A high-entropy AlFeCrMo alloy target was obtained, and a coating was prepared using single-target radio frequency magnetron sputtering. The tubular sample was mounted in the sputtering chamber, with its rotation speed set to 10 r / min and a vacuum level of 0.6 × 10⁻⁶. -3 After Pa, high-purity Ar gas is introduced to maintain the sputtering pressure at 0.6 Pa, and the sputtering power is set to 700 W.

[0045] The AlFeCrMo high-entropy alloy coating contains 30 at.% Al, 25 at.% Fe, 30 at.% Cr, and 15 at.% Mo.

[0046] Example 3 1. Matrix preparation: The pipe used is ferritic / martensitic steel pipe, which is ultrasonically cleaned and then dried for later use.

[0047] The cleaning process uses ultrasonic cleaning equipment, anhydrous ethanol as the cleaning solution, and the cleaning time is 12 minutes. After cleaning four times, the product is dried in a 60℃ drying oven.

[0048] 2. Preparation of high-entropy alloy coatings: A high-entropy AlFeCrMo alloy target was obtained, and a coating was prepared using single-target radio frequency magnetron sputtering. The tubular sample was mounted in the sputtering chamber, with its rotation speed set to 25 r / min and a vacuum level of 0.5 × 10⁻⁶. -3 After Pa, high-purity Ar gas is introduced to maintain the sputtering pressure at 0.55 Pa, and the sputtering power is set to 700 W.

[0049] The AlFeCrMo high-entropy alloy coating contains 25 at.% Al, 25 at.% Fe, 25 at.% Cr, and 25 at.% Mo.

[0050] Example 4 1. Matrix preparation: The pipe used is ferritic / martensitic steel pipe, which is ultrasonically cleaned and then dried for later use.

[0051] The cleaning process uses ultrasonic cleaning equipment, anhydrous ethanol as the cleaning solution, and the cleaning time is 15 minutes. After cleaning three times, the product is dried in a 60℃ drying oven.

[0052] 2. Preparation of high-entropy alloy coatings: A high-entropy AlFeCrMo alloy target was obtained, and a coating was prepared using single-target radio frequency magnetron sputtering. The tubular sample was mounted in the sputtering chamber, with its rotation speed set to 25 r / min and a vacuum level of 0.6 × 10⁻⁶. -3 After Pa, high-purity Ar gas is introduced to maintain the sputtering pressure at 0.6 Pa, and the sputtering power is set to 600 W.

[0053] The AlFeCrMo high-entropy alloy coating contains 30 at.% Al, 30 at.% Fe, 20 at.% Cr, and 20 at.% Mo.

[0054] Example 5 1. Matrix preparation: The pipe used is ferritic / martensitic steel pipe, which is ultrasonically cleaned and then dried for later use.

[0055] The cleaning process uses ultrasonic cleaning equipment, and the cleaning solution is anhydrous ethanol. The cleaning time is 10 minutes. After cleaning twice, the product is dried in a drying oven at 70℃.

[0056] 2. Preparation of high-entropy alloy coatings: AlFeCrMo high-entropy alloy target material was obtained, and coating preparation was carried out using single-target radio frequency magnetron sputtering. The tubular sample was installed in the sputtering chamber, and its rotation speed was set to 18 r / min. After the vacuum degree reached 0.6×10-3 Pa, high-purity Ar gas was introduced to maintain the sputtering gas pressure at 0.6 Pa, and the sputtering power was set to 600 W.

[0057] The AlFeCrMo high-entropy alloy coating contains 15 at.% Al, 30 at.% Fe, 25 at.% Cr, and 30 at.% Mo.

[0058] Example 5 The AlFeCrMo high-entropy alloy coating sample obtained in Example 4 was subjected to a lead-bismuth corrosion test at 550°C for 2000 hours, with the dissolved oxygen content controlled between 1 and 5 × 10⁻⁶. -7 wt.%, and simultaneously, an uncoated ferritic / martensitic steel pipe sample was added as a reference sample for corrosion testing under the same conditions. After corrosion, the cross-sectional SEM morphology of the AlFeCrMo high-entropy alloy coating sample obtained in Example 4 of this invention is as follows: Figure 2 As shown, the SEM morphology of the cross-section of the uncoated ferrite / martensitic steel pipe sample after corrosion is as follows: Figure 3 As shown.

[0059] from Figure 2 As can be seen, the AlFeCrMo high-entropy alloy coating obtained in Example 4 of this invention still maintains a tight bond with the substrate after 2000 hours of lead-bismuth corrosion under oxygen-deficient conditions, effectively protecting the substrate from failure caused by dissolution and oxidation.

[0060] from Figure 3 It can be seen that the interface integrity between the matrix and lead-bismuth in the uncoated ferritic / martensitic steel pipe sample was damaged. The ferritic / martensitic steel failed to form an effective protective oxide film in the oxygen-deficient environment, resulting in a serrated cross-section caused by dissolution and consumption. Furthermore, lead-bismuth penetrated into the matrix, compromising the reliability of the material.

[0061] Therefore, through the above comparison, it is shown that the AlFeCrMo high-entropy alloy coating obtained in Example 4 of the present invention has a very strong ability to resist lead-bismuth corrosion at high temperatures under oxygen-deficient conditions and has strong corrosion resistance.

[0062] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-entropy alloy coating resistant to high-temperature lead bismuth corrosion under oxygen-poor conditions, characterized in that, The high-entropy alloy coating contains Al 15-30 at.%, Fe 15-30 at.%, Cr 15-30 at.%, and Mo 15-30 at.%.

2. A method for preparing the high-entropy alloy coating layer resistant to high-temperature lead-bismuth corrosion under the oxygen-poor condition according to claim 1, characterized in that, The method comprises the following steps: pretreating the large-curvature pipe; obtaining an AlFeCrMo high-entropy alloy target material by adopting a powder metallurgy method; preparing a high-entropy alloy coating on the surface of the pretreated large-curvature pipe by using a single-target radio frequency magnetron sputtering technology.

3. The method of claim 2, wherein the method further comprises: depositing a high-entropy alloy layer on the substrate; and annealing the high-entropy alloy layer at a temperature of 300-600 °C for 1-10 hours. The large-curvature pipe is a ferrite / martensite steel pipe.

4. The method of claim 3, wherein the method further comprises: depositing a high-entropy alloy layer on the substrate; and annealing the high-entropy alloy layer at a temperature of 300-600 °C for 1-10 hours. The ferrite / martensite steel pipe has a diameter of 9 mm and a tolerance range of ±0.03 mm.

5. The method of claim 2, wherein the method further comprises: depositing a high-entropy alloy layer on the substrate; and annealing the high-entropy alloy layer at a temperature of 300-600 °C for 1-10 hours. The pretreatment of the large-curvature pipe comprises the following steps: first, ultrasonic cleaning the large-curvature pipe for 2-4 times, and then drying the cleaned large-curvature pipe.

6. The method of claim 5, wherein the method further comprises: depositing a high-entropy alloy layer on the substrate. The ultrasonic cleaning of the large-curvature pipe is performed by using an ultrasonic cleaning device, the cleaning liquid is anhydrous ethanol, and the cleaning time is 10-15 min.

7. The method of claim 5, wherein the method further comprises: depositing a high-entropy alloy layer on the substrate; and annealing the high-entropy alloy layer at a temperature of 300-600 °C for 1-10 hours. The drying of the large-curvature pipe is performed in a drying box, and the drying temperature is 50-70 °C.

8. The method of claim 2, wherein the method further comprises: depositing a high-entropy alloy layer on the substrate; and annealing the high-entropy alloy layer at a temperature of 300-600 °C for 1-10 hours. The preparation of the AlFeCrMo high-entropy alloy target material comprises the following steps: sequentially mixing 15-30 at.% of Al, 15-30 at.% of Fe, 15-30 at.% of Cr, and 15-30 at.% of Mo, hot-pressing sintering, component testing, and machining to obtain the AlFeCrMo high-entropy alloy target material.

9. The method of claim 2, wherein the method further comprises: depositing a high-entropy alloy coating on the substrate. The self-rotation speed of the large curvature pipe material in the sputtering film chamber is controlled at 10-25 r / min, and the vacuum degree is controlled at 3-6*10 -4 Pa, and the sputtering gas pressure is controlled at 0.5-0.6 Pa by introducing Ar with a purity of 99.999%, the sputtering power is controlled at 500-700 W, the temperature of the large curvature pipe material is controlled at room temperature when the sputtering starts, and the temperature of the large curvature pipe material is controlled below 150 DEG C during the sputtering process.

10. The method of claim 9, wherein the method further comprises: depositing a high-entropy alloy layer on the substrate; and annealing the high-entropy alloy layer at a temperature of 300-600 °C for 1-10 hours. The high-entropy alloy coating prepared on the surface of the large-curvature pipe has a thickness of 4-6 μm.

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