A method for preparing a self-reactive pre-oxidized multi-principal-element alloy composite coating suitable for high-temperature and high-pressure environments.

Abstract

A method for preparing a self-reactive pre-oxidizing multi-principal alloy composite coating suitable for high-temperature and high-pressure environments is disclosed. This invention addresses the problem of insufficient performance and susceptibility to damage and failure of existing coatings on the surfaces of key components of nuclear equipment under high-temperature and high-pressure conditions. The self-reactive pre-oxidizing high-entropy alloy composite coating of this invention consists of a dilution control layer, a high-entropy protective layer, and a pre-oxidizing layer. The preparation method of the composite coating is as follows: 1. Pre-treating the substrate material; 2. Preparing a substrate with a dilution control layer; 3. Preparing a multi-element alloy protective layer using a laser cladding process with multi-element alloy protective layer powder as the cladding powder; 4. Performing self-reactive pre-oxidation on the prepared coating at a specific temperature and holding time to obtain a high-entropy alloy composite coating with a dense pre-oxidizing layer. This invention's high-entropy alloy composite protective coating significantly improves the protective capability of the coating under high-temperature and high-pressure service environments by forming a pre-oxidizing layer through in-situ surface self-oxidation.

Description

Technical Field

[0001] This invention belongs to the field of surface modification technology for key components under high temperature and high pressure environments, and specifically relates to a method for preparing a multi-principal-element alloy composite coating that can form an oxide layer in situ. Background Technology

[0002] The continuous development of nuclear power plants has placed higher demands on the safety and reliability of key components of nuclear systems. However, under the operating conditions of pressurized water reactors, key components, such as fuel cladding tubes, are subjected to the coupled effects of high-temperature, high-pressure water corrosion and stress, which can easily lead to material failure and operational safety risks. Under extreme conditions of high temperature and pressure, the excellent oxidation resistance and thermal stability of materials are crucial to ensuring that components do not suffer damage or failure during long-term service. Meanwhile, scouring and vibration from fluids such as coolants, and pressure differences between the inner and outer walls of components are also key factors affecting the structural stability of materials. Due to the high solubility of corrosive media at high temperatures, the chemical corrosion process under high temperature and high pressure is more rapid and intense. Therefore, improving the service performance of nuclear components under high temperature and high pressure environments is a critical challenge that urgently needs to be addressed in the field of nuclear safety.

[0003] Surface coating technology can significantly improve the service safety of equipment without affecting the original performance of the substrate. Developing coating systems suitable for nuclear component materials has become one of the most ideal solutions. Multi-principal element alloys, a new type of high-performance alloy material developed under the guidance of high-entropy strengthening design, have significant application value and broad application prospects in surface engineering protection due to their excellent comprehensive service performance and design control potential. However, single coatings still exhibit difficulties in achieving comprehensive performance under harsh environments, especially in high-entropy alloy coatings which may peel off due to the formation of multiple types of oxides under high temperature and high pressure. Based on the easily oxidizable elements in multi-principal element alloys, post-treatment before coating service can effectively improve the service performance of composite coatings by enabling the surface to self-react and form a protective oxide layer. By increasing the self-reaction oxidation temperature and reducing the holding time, the formation of multiple types of oxides due to long-term oxidation reactions on the surface of multi-principal element alloy coatings can be avoided, thereby quickly obtaining a dense pre-oxidized layer with a single thermodynamically stable oxide. This significantly reduces surface corrosion and hydride precipitation under high temperature and high pressure, altering its performance at a lower cost, allowing key components to significantly improve their safety performance in a short period without major modifications.

[0004] The elemental design of multi-principal element alloy coatings must adhere to the principle of matching the strong thermophysical properties with the matrix elements to ensure that the matrix elements can also be well dissolved in the coating phase after flotation. Simultaneously, elements with excellent performance must be added according to the coating's operating conditions. High-temperature and high-pressure environments mainly involve high-temperature oxidation and corrosion processes, placing high demands on the high-temperature and corrosion performance of materials used in such environments. Selecting elements with strong oxidation competition and oxide stability can improve the serviceability of multi-principal element alloys under high temperature and high pressure. Furthermore, complex oxides with strong oxidation resistance can be designed based on the reaction processes of simple oxides. The chemical composition of the pre-oxidized layer is determined based on the standard reaction free energy of elements at the pre-oxidation temperature, resulting in a composite synergistic protective oxidation-resistant layer consisting of a highly oxidation-resistant pre-oxidized layer and a multi-type complex dense oxide multi-principal element alloy surface. The multi-element alloy coating system is then optimized based on the oxidation kinetic curves under high-temperature and high-pressure environments. Summary of the Invention

[0005] The purpose of this invention is to address the problem of insufficient overall service performance of nuclear components under high temperature and high pressure coupling conditions. It provides a method for preparing a multi-principal alloy coating with an in-situ pre-oxidation layer on the surface under high temperature and high pressure service conditions. The aim is to develop a high-performance multi-element alloy coating that can form a pre-oxidation layer in situ to meet the protection requirements of the substrate material, and to promote the synergistic improvement of the high temperature and high pressure resistance and environmental adaptability of the multi-element alloy composite protective coating on the surface of the substrate material.

[0006] This invention relates to a method for preparing a self-reactive pre-oxidized multi-principal-element alloy composite coating under high temperature and high pressure conditions, which is implemented according to the following steps:

[0007] 1. The substrate material is subjected to grinding, polishing and cleaning in sequence to obtain the pretreated substrate material;

[0008] 2. Using laser cladding technology and synchronous powder feeding, NbZrXY alloy powder is used as the cladding powder to perform laser cladding, resulting in a matrix with a dilution control layer.

[0009] 3. Using laser cladding technology with synchronous powder feeding, multi-element alloy protective layer powder is used as the cladding powder. The laser power is controlled at 1800-2000W, the scanning speed at 20-25mm / s, the spot diameter at 1.5-3mm, the overlap rate at 35-40%, the powder feeding rate at 0.15-0.25g / s, and the carrier gas flow rate at 20-30L / min for laser cladding. A multi-element alloy protective layer is formed on the dilution control layer, resulting in a substrate with a dilution control layer and a multi-element alloy protective layer.

[0010] IV. The substrate with the dilution control layer-multi-element alloy protective layer is placed in a muffle furnace and pre-oxidized at a temperature of 500-700℃ to obtain a multi-principal alloy composite coating that can be self-reactively pre-oxidized under high temperature and high pressure environment.

[0011] In step two, X in the NbZrXY alloy is Ti, Al, or Sn, and Y is one or more mixed elements selected from Cr, Cu, V, W, and Co.

[0012] In step three, the multi-element alloy protective layer powder is formed by ball milling and mixing 10% to 20% of the reinforcing phase powder and 80% to 90% of the NbTiZrA alloy powder according to the mass percentage. The A in the NbTiZrA alloy is one or more mixed elements selected from Al, Sn, Gd, Cr, Cu, Co, and Mo. The reinforcing phase is one or more mixed powders selected from TiC, WC, LaB6, and ZrO2.

[0013] This invention relates to a self-reactive pre-oxidizing multi-principal-element alloy composite coating suitable for high-temperature and high-pressure environments. This self-reactive oxide-forming multi-element alloy composite coating consists of three parts: a dilution-regulating layer, a multi-element alloy protective layer, and an in-situ oxide layer. The invention prepares NbZrXY alloy powder at an atomic percentage of 10%–25% for each element, and ball-mills and mixes the metal powders to obtain the dilution-regulating coating cladding material. The protective coating material is obtained by mixing 10%–20% by weight of the reinforcing phase powder and 80%–90% by weight of the NbTiZrA alloy powder.

[0014] The self-reactive pre-oxidizing multi-element alloy composite coating provided by this invention exhibits good thermophysical property matching with the substrate, high adhesion to the substrate, and high forming quality with no defects such as cracks or pores. Furthermore, during the preparation process, due to the presence of the dilution control layer, less elemental components from the substrate rise to the surface, minimizing the impact on the target elemental composition of the multi-element alloy protective layer.

[0015] This invention utilizes laser cladding technology to prepare a dilution control layer and a multi-element alloy protective layer on the surface of a substrate material, and then induces an in-situ self-reaction at a specific temperature to form a dense pre-oxidized layer on the surface of the multi-element alloy protective layer. This invention leverages the strong high-temperature oxidation resistance of the multi-element alloy composite coating and the functional characteristics of the dilution control layer, while also utilizing the rapid in-situ self-oxidation reaction characteristics of easily oxidized elements in the multi-element alloy coating system. Because the elements are distributed in different phases, the oxidation competition tendency is smaller compared to single-solid-phase high-entropy alloys. Easily oxidized elements can rapidly form an oxide layer protecting the coating and substrate through oxygen diffusion channels provided by the multiphase interface. This enables flexible customization of the protective coating on the substrate material surface, solving the technical problem of easy peeling and failure of traditional protective coatings on the surface of substrate materials in high-temperature and high-pressure environments. Furthermore, the functionality of different high-temperature and corrosion-resistant multi-element alloy coatings can be customized according to specific service conditions, providing a new solution for the flexible design of specific high-performance coatings on the substrate material surface. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the self-reactive pre-oxidizing multi-element alloy composite coating prepared according to the present invention.

[0017] Figure 2 The cross-sectional morphology of the self-reactive pre-oxidized multi-principal alloy composite coating obtained in the example is shown.

[0018] Figure 3 The microstructure of the self-reactive pre-oxidized multi-principal alloy composite coating obtained in the example is shown in the figures: (a) multi-element alloy protective layer, (b) pre-oxidized layer.

[0019] Figure 4 The images show the surface morphology of the multi-principal element alloy composite coating after the high temperature and high pressure steam test obtained in the example, where (a) is the coating before pre-oxidation and (b) is the coating after pre-oxidation.

[0020] Figure 5 The oxidation kinetics curves of the multi-principal-element alloy composite coating and substrate after the high-temperature and high-pressure steam test obtained in the example are shown. Detailed Implementation

[0021] Specific Implementation Method 1: This implementation method is applicable to the preparation method of multi-principal element alloy composite coatings that can undergo self-reactive pre-oxidation under high temperature and high pressure environments, and is carried out according to the following steps:

[0022] 1. The substrate material is subjected to grinding, polishing and cleaning in sequence to obtain the pretreated substrate material;

[0023] 2. Using laser cladding technology and synchronous powder feeding, NbZrXY alloy powder is used as the cladding powder to perform laser cladding, resulting in a matrix with a dilution control layer.

[0024] 3. Using laser cladding technology with synchronous powder feeding, multi-element alloy protective layer powder is used as the cladding powder. The laser power is controlled at 1800-2000W, the scanning speed at 20-25mm / s, the spot diameter at 1.5-3mm, the overlap rate at 35-40%, the powder feeding rate at 0.15-0.25g / s, and the carrier gas flow rate at 20-30L / min for laser cladding. A multi-element alloy protective layer is formed on the dilution control layer, resulting in a substrate with a dilution control layer and a multi-element alloy protective layer.

[0025] IV. The substrate with the dilution control layer-multi-element alloy protective layer is placed in a muffle furnace and pre-oxidized at a temperature of 500-700℃ to obtain a multi-principal alloy composite coating that can be self-reactively pre-oxidized under high temperature and high pressure environment.

[0026] In step two, X in the NbZrXY alloy is Ti, Al, or Sn, and Y is one or more mixed elements selected from Cr, Cu, V, W, and Co.

[0027] In step three, the multi-element alloy protective layer powder is formed by ball milling and mixing 10% to 20% of the reinforcing phase powder and 80% to 90% of the NbTiZrA alloy powder according to the mass percentage. The A in the NbTiZrA alloy is one or more mixed elements selected from Al, Sn, Gd, Cr, Cu, Co, and Mo. The reinforcing phase is one or more mixed powders selected from TiC, WC, LaB6, and ZrO2.

[0028] This embodiment features a multi-element alloy composite coating capable of forming a pre-oxidized layer in situ through self-reaction. The coating consists of a dilution control layer and a multi-element alloy protective layer sequentially deposited on the surface of a substrate material, and a pre-oxidized layer formed in situ through self-reaction on the surface of the multi-element alloy protective layer at a specific temperature.

[0029] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the base material mentioned in step one is alloy steel or zirconium alloy.

[0030] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that in step 1, the base material is polished sequentially using sandpaper of 150#, 600#, 1000#, and 2000#.

[0031] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the preparation method of NbZrXY alloy powder in step two is as follows:

[0032] Nb, Zr, X, and Y metal powders were mixed in a planetary ball mill according to an equiatomic ratio. The ball milling media were GCr15 steel balls. The ball-to-material mass ratio was controlled at 3:1, the rotation speed was 300-350 r / min, and the ball milling time was 3-6 h. After drying, NbZrXY alloy powder was obtained.

[0033] Specific Implementation Method 5: This implementation method differs from one of the specific implementation methods one to four in that X in the NbZrXY alloy powder described in step two is Ti or Al, and Y is Cr or Cu.

[0034] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that in step two, the laser power is controlled at 1500-1800W, the scanning speed at 15-20mm / s, the spot diameter at 1.5-3mm, the overlap rate at 35-40%, the powder feeding rate at 0.15-0.25g / s, and the carrier gas flow rate at 20-30L / min for laser cladding.

[0035] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that the preparation method of the multi-element alloy protective layer powder in step three is as follows:

[0036] According to the mass percentage, 10%–20% of the reinforcing phase powder and 80%–90% of the NbTiZrA alloy powder were placed in a planetary ball mill for mixing. The ball milling media were GCr15 steel balls, the ball-to-material mass ratio was controlled at 3:1, the rotation speed was 300–350 r / min, and the ball milling time was 3–6 h. After drying, the multi-element alloy protective layer powder was obtained.

[0037] The drying temperature in this embodiment is 120–180°C.

[0038] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that, in step three, the laser power is controlled at 1800–1900W, the scanning speed at 20–22 mm / s, the spot diameter at 2–3 mm, the overlap rate at 38–40%, the powder feeding rate at 0.15–0.2 g / s, and the carrier gas flow rate at 20–25 L / min for laser cladding.

[0039] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the pre-oxidation treatment time in step four is 8 to 12 hours.

[0040] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 1 to 9 in that the thickness of the dilution control layer in the multi-principal alloy composite coating that can be self-reactively pre-oxidized under high temperature and high pressure is 200-250 μm, and the thickness of the multi-principal alloy composite coating is 300-350 μm.

[0041] This embodiment is applicable to multi-principal alloy composite coatings that can undergo self-reactive pre-oxidation under high temperature and high pressure environments, where the thickness of the self-reactive pre-oxidized layer is optimized to 100-150 μm.

[0042] Example: This example describes a method for preparing a self-reactive pre-oxidized multi-principal-element alloy composite coating under high temperature and high pressure conditions, implemented according to the following steps:

[0043] 1. The Zr702 alloy substrate material was polished with 150#, 600#, 1000# and 2000# sandpaper in sequence. After polishing, it was ultrasonically cleaned with acetone and anhydrous ethanol in sequence to obtain the pretreated substrate material.

[0044] 2. Using laser cladding technology with synchronous powder feeding, NbZrTiCr alloy powder (equal atomic ratio of each element) was used as the cladding powder. The laser power was controlled at 1600W, the scanning speed at 15mm / s, the spot diameter at 3mm, the overlap rate at 40%, the powder feeding rate at 0.15g / s, and the carrier gas flow rate at 20L / min to obtain a substrate with a dilution control layer.

[0045] 3. Using laser cladding process with synchronous powder feeding, multi-element alloy protective layer powder is used as cladding powder. The laser power is controlled at 1800W, the scanning speed is 20mm / s, the spot diameter is 3mm, the overlap rate is 40%, the powder feeding rate is 0.15g / s, and the carrier gas flow rate is 20L / min to carry out laser cladding, forming a multi-element alloy protective layer on the dilution control layer, thus obtaining a substrate with a dilution control layer and a multi-element alloy protective layer.

[0046] 4. The substrate with the dilution control layer-multi-element alloy protective layer is placed in a muffle furnace, the heating rate is controlled at 10℃ / min, and the pre-oxidation treatment is carried out at 600℃ for 10h in air atmosphere to obtain a multi-principal alloy composite coating that can be self-reactively pre-oxidized under high temperature and high pressure environment.

[0047] In step three, the multi-element alloy protective layer powder is formed by ball milling and mixing 4% of the reinforcing phase powder and 96% of the NbTiZrAl alloy powder (each element is in equiatomic ratio) according to the mass percentage. The reinforcing phase is TiC powder.

[0048] The composite coating obtained in this embodiment consists of three layers: the first layer is a high-entropy NbZrXY alloy layer with dilution control function; the second layer is a multi-element alloy layer with protective function; and the third layer is a pre-oxidized layer formed in situ by self-reaction.

[0049] The multi-element alloy coating samples obtained in the examples were cut, ground, and polished. The cross-sectional morphology of the multi-layer coating was characterized using scanning electron microscopy. The test results are as follows: Figure 2As shown; the microstructure of the multi-element alloy protective layer and the in-situ pre-oxidation layer was characterized using scanning electron microscopy, and the test results are as follows. Figure 3 As shown; the surface morphology of the coating before and after pre-oxidation following the high-temperature and high-pressure steam test was characterized using scanning electron microscopy, and the test results are as follows. Figure 4 As shown; the sample was placed in a high-temperature and high-pressure reactor for performance testing under high-temperature and high-pressure steam environment. The test temperature and pressure were 360℃ / 18.5MPa, and the oxidation time was 100h. The oxidation kinetic curves obtained from the test are shown in the figure. Figure 5 As shown in the figure, the experimental results show that the multi-element alloy composite coating has a three-layer structure: a dilution control layer, a multi-element alloy protective layer, and an in-situ pre-oxidation layer. After pre-oxidation, a dense pre-oxidation layer is formed on the surface of the coating through self-reaction. After high-temperature and high-pressure steam testing, the surface of the coating before pre-oxidation showed fragmented oxides, while the surface of the pre-oxidized coating was smooth and showed no obvious oxidation peeling. The multi-element alloy coating can effectively improve the service performance of the substrate material under high-temperature and high-pressure environments, and the multi-element alloy composite coating after self-reaction pre-oxidation has better oxidation resistance and a denser surface oxide layer. In summary, the self-reaction pre-oxidized multi-element alloy coating prepared by this invention can effectively improve the service life of key components under high-temperature and high-pressure steam environments.

[0050] This embodiment utilizes the strong high-temperature oxidation resistance of the multi-element alloy composite coating and the functional characteristics of the dilution control layer, while taking advantage of the rapid in-situ self-oxidation reaction characteristics of easily oxidized elements in the multi-element alloy coating system, to obtain a composite protective coating that combines excellent comprehensive service performance such as dilution control, high temperature and high pressure resistance, and corrosion resistance.

[0051] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the concept of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a multi-principal element alloy composite coating suitable for self-reactive pre-oxidation under high temperature and high pressure environment, characterized in that The preparation method is realized according to the following steps: I. The base material is sequentially polished, polished and cleaned to obtain a pretreated base material; II. Laser cladding process is used, and NbZrXY alloy powder is used as the cladding powder to form a dilution control layer on the base material; III. Laser cladding process is used, and multi-element alloy protective layer powder is used as the cladding powder to form a multi-element alloy protective layer on the dilution control layer, thereby obtaining a base material with a dilution control layer-multi-element alloy protective layer; IV. The base material with a dilution control layer-multi-element alloy protective layer is placed in a muffle furnace and pre-oxidized at a temperature of 500-700 DEG C to obtain a multi-main element alloy composite coating suitable for self-reaction pre-oxidation in a high temperature and high pressure environment; In step II, X in the NbZrXY alloy is Ti, Al or Sn, and Y is one or more mixed elements selected from Cr, Cu, V, W and Co; In step III, the multi-element alloy protective layer powder is mixed by 10-20% of the strengthening phase powder and 80-90% of the NbTiZrA alloy powder, and A in the NbTiZrA alloy is one or more mixed elements selected from Al, Sn, Gd, Cr, Cu, Co and Mo, and the strengthening phase is one or more mixed powders selected from TiC, WC, LaB6 and ZrO2.

2. The method of claim 1, wherein the method is characterized by In step I, the base material is an alloy steel or a zirconium alloy.

3. The method of claim 1, wherein the method is characterized by In step I, the base material is sequentially polished with 150#, 600#, 1000# and 2000# sandpaper.

4. The method of claim 1, wherein the method of preparing the multi-principal element alloy composite coating that is self-reactive pre-oxidizable under high temperature and high pressure environments is characterized by In step II, the NbZrXY alloy powder is prepared as follows: According to the equal atomic ratio, the Nb, Zr, X and Y metal powders are mixed in a planetary ball mill, the ball milling medium is GCr15 steel ball, the ball-to-material mass ratio is controlled to be 3:1, the rotation speed is 300-350 r / min, the ball milling time is 3-6 h, and the NbZrXY alloy powder is obtained after drying.

5. The method of claim 1, wherein the method of preparing the multi-principal element alloy coating composite suitable for self-reactive pre-oxidation under high temperature and high pressure environment is characterized by In step II, X in the NbZrXY alloy powder is Ti or Al, and Y is Cr or Cu.

6. The method of claim 1, wherein the method of preparing the multi-principal element alloy coating composite suitable for self-reactive pre-oxidation under high temperature and high pressure environment is characterized by In step II, the laser power is controlled to be 1500-1800 W, the scanning speed is 15-20 mm / s, the spot diameter is 1.5-3 mm, the overlap rate is 35-40%, the powder feeding rate is 0.15-0.25 g / s, and the carrier gas flow is 20-30 L / min.

7. The method of claim 1, wherein the method is characterized by In step III, the multi-element alloy protective layer powder is prepared as follows: According to the mass percentage, 10%-20% of the reinforcing phase powder and 80%-90% of the NbTiZrA alloy powder are placed in a planetary ball mill for mixing, the ball milling medium is GCr15 steel ball, the ball-to-charge mass ratio is controlled to be 3:1, the rotating speed is 300-350 r / min, the ball milling time is 3-6 h, and after drying, the multi-element alloy protective layer powder is obtained.

8. The method of claim 1, wherein the method of preparing the multi-principal element alloy coating composite suitable for self-reactive pre-oxidation under high temperature and high pressure environment is characterized by In step three, the laser power is controlled to be 1800-1900 W, the scanning speed is 20-22 mm / s, the spot diameter is 2-3 mm, the overlap rate is 38-40%, the powder feeding rate is 0.15-0.2 g / s, and the carrier gas flow rate is 20-25 L / min for laser cladding.

9. The method of claim 1, wherein the method of preparing the multi-principal element alloy coating composite suitable for self-reactive pre-oxidation under high temperature and high pressure environment is characterized by In step four, the pre-oxidation treatment time is 8-12 h.

10. The method of claim 1, wherein the method of preparing the multi-principal element alloy coating composite suitable for self-reactive pre-oxidation under high temperature and high pressure environment is characterized by In the multi-principal element alloy composite coating which is suitable for self-reaction pre-oxidation in a high temperature and high pressure environment, the thickness of the dilution control layer is 200-250 μm, and the thickness of the multi-principal element alloy composite coating is 300-350 μm.

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