FeCrAl composite coating for zirconium alloy surface and preparation method and application thereof

Abstract

The application discloses a FeCrAl composite coating for a zirconium alloy surface and a preparation method and application thereof. The FeCrAl composite coating comprises a metallurgical bonding layer and a FeCrAl cladding layer formed on the surface of a substrate in sequence, and the FeCrAl composite coating is formed by cladding FeCrAl alloy on the surface of a zirconium alloy substrate by using a super-speed laser cladding technology; wherein, in the direction away from the surface of the substrate, the content of Fe, Cr and Al elements in the metallurgical bonding layer gradually increases, and the metallurgical bonding layer is mainly composed of Fe-Zr solid solution and Cr-Zr solid solution. The FeCrAl composite coating in the application can form a metallurgical bonding with the substrate, the coating organization is uniform and small, the reaction speed of the cladding material with water vapor at high temperature can be reduced, the core degradation process is delayed, and the zirconium alloy pipe has better high-temperature oxidation resistance and good mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of accident-tolerant fuel coating technology, specifically relating to a FeCrAl composite coating for zirconium alloy surfaces, its preparation method, and its application. Background Technology

[0002] Nuclear energy is a clean, low-carbon, safe, and efficient strategic energy source, occupying a crucial position in the future energy market. Zirconium (Zr) and its alloys possess outstanding nuclear properties, such as a small thermal neutron absorption cross section, excellent radiation resistance, high thermal conductivity, and good mechanical properties, thus leading to the concept of accident-tolerant fuel (ATF). Developing zirconium alloy surface coatings with high resistance to water vapor oxidation, corrosion and wear, hydrogen absorption, and radiation is the mainstream international direction for developing ATF surface-reinforced zirconium alloy cladding materials. FeCrAl alloys have attracted considerable attention among accident-tolerant fuel candidate materials due to their high thermal conductivity and excellent high-temperature oxidation resistance.

[0003] Traditional coating techniques, such as spraying, produce thin coatings with poor uniformity. Physical vapor deposition (PVD) presents technical challenges in achieving uniform deposition on the curved surfaces of fuel cladding tubes, and importantly, the coating and substrate are physically bonded interfaces, posing a risk of coating peeling during long-term service in harsh environments, thus failing to meet production requirements. Therefore, addressing the limitations of existing FeCrAl coating structures and preparation processes, providing a high-resistance coating for fuel cladding surfaces and its preparation method is an urgent problem to be solved. Summary of the Invention

[0004] The main objective of this invention is to provide a FeCrAl composite coating for zirconium alloy surfaces, its preparation method, and its application. The prepared FeCrAl composite coating has good adhesion to zirconium alloys, low dilution rate, fine coating structure, and uniform coating thickness, which gives the coating good resistance to high-temperature water vapor oxidation and can reduce the risk of damage to the zirconium alloy cladding in accident environments.

[0005] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0006] This invention provides a FeCrAl composite coating for zirconium alloy surfaces. The FeCrAl composite coating comprises a metallurgical bonding layer and a FeCrAl cladding layer sequentially formed on the substrate surface. The FeCrAl composite coating is formed by cladding a FeCrAl alloy onto the zirconium alloy substrate surface using ultra-high-speed laser cladding technology. In the direction away from the substrate surface, the content of Fe, Cr, and Al elements in the metallurgical bonding layer gradually increases. The metallurgical bonding layer is mainly composed of Fe-Zr solid solutions and Cr-Zr solid solutions. The main phase of the FeCrAl cladding layer includes an α-Fe-based solid solution alloy with a body-centered cubic structure. The grain size of the FeCrAl cladding layer is 10–30 μm.

[0007] This invention also provides a method for preparing the aforementioned FeCrAl composite coating for zirconium alloy surfaces, comprising:

[0008] Provide zirconium alloy substrate;

[0009] The zirconium alloy substrate is preheated to 200–500°C;

[0010] Furthermore, the FeCrAl alloy is clad onto the surface of a zirconium alloy substrate using ultra-high-speed laser cladding technology to obtain a FeCrAl composite coating for the zirconium alloy surface.

[0011] The embodiments of the present invention also provide the application of the aforementioned FeCrAl composite coating in the protection of curved surface parts.

[0012] The present invention also provides a fuel cladding device, which includes a zirconium alloy tube and a FeCrAl composite coating prepared by the aforementioned preparation method.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] (1) In this invention, FeCrAl composite coating was prepared on the surface of zirconium alloy tube by ultra-high speed laser cladding. The coating forms a metallurgical bond with the substrate. Compared with traditional cladding, the thickness of the dilution layer between the coating and the substrate is smaller, with a thickness of 20-80 μm. At the same time, the zirconium alloy tube after treatment has better high temperature oxidation resistance, lower surface roughness and higher hardness.

[0015] (2) Before preparing the coating, the zirconium alloy tube is preheated to reduce cracks caused by excessive solidification speed, avoid the phenomenon of increased corrosion during high-temperature oxidation caused by cracks, and reduce the size of unmelted particles.

[0016] (3) The FeCrAl composite coating prepared by the present invention can be oxidized by water vapor at 1200℃ for 60 min and maintain the integrity of the coating structure without large-area peeling. The good adhesion improves the anti-oxidation performance of the coating in the steam environment and avoids peeling off in the high temperature water vapor environment. At the same time, the Cr and Al oxide film formed on the surface of the coating during the oxidation process can effectively block oxygen from diffusing from the external environment to the coating and the substrate, effectively protecting the substrate. The oxidation weight gain is low, showing good resistance to high temperature oxidation corrosion. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figures 1a-1b This is a cross-sectional SEM image of the FeCrAl composite coating obtained in Example 1 of this invention;

[0019] Figure 2 This is a grain size diagram of the FeCrAl composite coating obtained in Example 1 of the present invention;

[0020] Figure 3 This is the X-ray diffraction pattern of the FeCrAl composite coating prepared in Example 1 of this invention;

[0021] Figure 4 This is a scratch surface diagram of the FeCrAl composite coating obtained in Example 1 of the present invention;

[0022] Figures 5a-5b These are the surface profile and roughness curves of the FeCrAl coatings obtained in Example 1 and Comparative Example 2 of this invention.

[0023] Figure 6 This is a graph showing the weight gain curve of the FeCrAl composite coating prepared in Example 1 of this invention under high temperature water vapor at 1200℃.

[0024] Figure 7 These are cross-sectional SEM and EDS images of the FeCrAl composite coating prepared in Example 1 of this invention after oxidation at 1200℃ high-temperature water vapor for 60 min;

[0025] Figure 8 This is the X-ray diffraction pattern of the FeCrAl composite coating obtained in Example 1 of this invention after oxidation for 60 min;

[0026] Figure 9This is a cross-sectional SEM image of the FeCrAl composite coating obtained in Example 2 of this invention;

[0027] Figure 10 This is a cross-sectional SEM image of the FeCrAl composite coating obtained in Example 3 of this invention;

[0028] Figure 11 This is a cross-sectional SEM image of the FeCrAl coating prepared in Comparative Example 1 of this invention.

[0029] Figure 12 This is a cross-sectional SEM image of the FeCrAl coating prepared in Comparative Example 1 of this invention after oxidation at 1200℃ high temperature water vapor for 60 min.

[0030] Figures 13a-13b This is a cross-sectional SEM image of the FeCrAl coating prepared in Comparative Example 2 of the present invention;

[0031] Figure 14 This is a cross-sectional SEM image of the FeCrAl coating prepared in Comparative Example 2 of this invention after oxidation at 1200℃ high temperature water vapor for 60 min;

[0032] Figure 15 This is a cross-sectional SEM image of the FeCrAl coating prepared in Comparative Example 3 of the present invention.

[0033] Figure 16 This is a digital image of the surface of the FeCrAl coating prepared in Comparative Example 4 of this invention;

[0034] Figure 17 This is an oxidation weight gain curve of the FeCrAl coating prepared in Comparative Example 5 of the present invention.

[0035] Figure 18 This is a hardness diagram of the FeCrAl coating obtained in Comparative Example 5 of the present invention. Detailed Implementation

[0036] In view of the deficiencies of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention, which mainly uses ultra-high-speed laser cladding technology to prepare metal anti-oxidation coatings. The adhesion of the coating is greatly improved compared with coatings prepared by traditional methods, and at the same time, the mechanical properties are superior.

[0037] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Specifically, as one aspect of the technical solution of this invention, a FeCrAl composite coating for a zirconium alloy surface includes a metallurgical bonding layer and a FeCrAl cladding layer sequentially formed on the substrate surface. The FeCrAl composite coating is formed by cladding a FeCrAl alloy onto the zirconium alloy substrate surface using ultra-high-speed laser cladding technology. In the direction away from the substrate surface, the content of Fe, Cr, and Al elements in the metallurgical bonding layer gradually increases. The metallurgical bonding layer is mainly composed of Fe-Zr solid solution and Cr-Zr solid solution. The main phase of the FeCrAl cladding layer includes an α-Fe-based solid solution alloy with a body-centered cubic structure. The grain size of the FeCrAl cladding layer is 10–30 μm.

[0039] The FeCrAl composite coating in this invention can form a metallurgical bond with the substrate. The coating has a uniform and fine structure, excellent adhesion and high strength. It can reduce the reaction rate of the cladding material with water vapor at high temperature, reduce the heat generated by cladding oxidation, delay the core degradation process, and enable the zirconium alloy tube to have better high-temperature oxidation resistance and mechanical properties.

[0040] In some preferred embodiments, the FeCrAl cladding layer comprises the following components by mass percentage: 68 wt% Fe, 25 wt% Cr and 7 wt% Al.

[0041] In some preferred embodiments, the thickness of the metallurgical bonding layer is 0–60 μm.

[0042] In some preferred embodiments, the thickness of the FeCrAl cladding layer is 20–50 μm.

[0043] In some preferred embodiments, the α-Fe-based solid solution alloy comprises an Fe-Cr solid solution.

[0044] Furthermore, the Fe-Cr solid solution content in the FeCrAl coating is 74–88 wt%.

[0045] In some preferred embodiments, the zirconium alloy substrate includes, but is not limited to, a Zr-4 alloy tube.

[0046] Furthermore, the length of the Zr-4 alloy tube is 300–400 mm.

[0047] Another aspect of the present invention provides a method for preparing the aforementioned FeCrAl composite coating for zirconium alloy surfaces, comprising:

[0048] Provide zirconium alloy substrate;

[0049] The zirconium alloy substrate is preheated to 200–500°C;

[0050] Furthermore, the FeCrAl alloy is clad onto the surface of a zirconium alloy substrate using ultra-high-speed laser cladding technology to obtain a FeCrAl composite coating for the zirconium alloy surface.

[0051] In some preferred embodiments, the average particle size of the FeCrAl alloy is 10–30 μm.

[0052] In some preferred embodiments, the FeCrAl alloy has a purity of 99.9 wt% or higher.

[0053] In some preferred embodiments, the FeCrAl alloy comprises the following components by mass percentage: 68 wt% Fe, 25 wt% Cr and 7 wt% Al.

[0054] In some preferred embodiments, the preparation method specifically includes: using ultra-high-speed laser cladding technology to clad the FeCrAl alloy onto the surface of a zirconium alloy substrate to obtain a FeCrAl composite coating; wherein, in the ultra-high-speed laser cladding technology, the flow rate of the powder feeding gas is 14-15 L / min, the laser power is 250-300 W, the laser moving speed is 5-7 m / min, the cladding linear speed is 20-40 m / min, the powder feeding amount is 3.9250 g / min, the single-pass transverse movement is 0.6-0.8 mm, and the distance between the laser head and the zirconium alloy substrate is 17.5-19 mm.

[0055] Furthermore, the powder feeding gas includes an inert gas, such as argon.

[0056] In some preferred embodiments, the preparation method further includes: before performing the cladding treatment, grinding and cleaning the zirconium alloy substrate; wherein the cleaning treatment includes: cleaning the surface of the zirconium alloy substrate obtained by grinding with ethanol and acetone, at least to remove grease.

[0057] This invention employs a method of preheating the substrate. A handheld butane gas spray gun is used to rotate the machine tool fixture, and the substrate alloy tube is uniformly heated at 200–500°C to reduce the possibility of crack formation in the coating and to reduce the size of unmelted particles.

[0058] This invention provides a method for preparing a FeCrAl composite coating, at a density of 10×10⁻⁶. 4 Under conditions of a high cooling rate of K / s and a high overlap rate of 60%–90%, the coating microstructure is controlled to achieve a uniform and fine texture, improving oxidation resistance. Simultaneously, it effectively avoids performance "contamination" of the coating by the substrate components, resulting in a low dilution rate. Furthermore, due to its metallurgical bonding characteristics, the coating also possesses high bonding strength. The preparation method of this invention includes the following steps:

[0059] a. Pretreatment of the base material: The Zr-4 alloy tube was polished with sandpaper of different grits; then it was ultrasonically cleaned with alcohol and acetone for 20 minutes in sequence; after cleaning, it was placed in a drying oven to dry.

[0060] b. Substrate installation: The Zr-4 alloy tube is clamped in the fixture of the ultra-high speed laser cladding machine tool, and the length of the zirconium alloy tube is 300mm;

[0061] c. Preheating of the substrate: Rotate the machine tool fixture and hold the butane gas torch to heat the Zr-4 alloy tube evenly until the tube turns red-hot;

[0062] d. Cladding Coating: The defocusing amount in the ultra-high-speed laser cladding equipment is set to +0mm, that is, the working distance of the cladding head is 20.6mm. FeCrAl powder is blown into the melting zone of the substrate surface using powder feeding gas. The flow rate of the powder feeder gas used in the cladding technology is 14L / min, the laser power is 250-300W, the cladding linear speed is 20-40m / min, the powder feeder disk rotation speed is 10%, and the single-pass transverse movement is 0.6-0.8mm. FeCrA composite coating is obtained. The cladding is stopped and the surface is allowed to cool naturally to room temperature.

[0063] Furthermore, the powder-feeding gas is argon.

[0064] Furthermore, the purity of FeCrAl powder is above 99.9%.

[0065] Furthermore, during the cladding process, the fixture maintains a high-speed rotation of 20–40 m / min, and the laser moving speed is 5–7 m / min; an ultra-high-speed laser cladding process is used to clad the coating.

[0066] Furthermore, at a laser power of 250W, the coating prepared by cladding has a uniform structure, fine grains, and almost no cracks, which can effectively protect the substrate from high-temperature water vapor corrosion.

[0067] The FeCrAl composite coating of this invention can form a metallurgical bond with the substrate, and the coating structure is uniform and fine. It can reduce the reaction rate of the cladding material with water vapor at high temperatures, delay the core degradation process, and at the same time has an excellent adhesion of 90N and a coating strength of up to 800Hv. 0.05 This gives zirconium alloy tubes superior resistance to high-temperature oxidation and good mechanical properties.

[0068] Another aspect of the present invention provides the use of the aforementioned FeCrAl composite coating in the protection of curved surface parts.

[0069] Another aspect of the present invention provides a fuel cladding device, which includes a zirconium alloy tube and an FeCrAl composite coating prepared by the aforementioned preparation method.

[0070] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0071] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0072] In this invention, to ensure the accuracy and reliability of the oxidation weight gain data, the sample is weighed three times before and after each oxidation, and the average value is taken as the final data.

[0073] Example 1

[0074] a. Pretreatment of the substrate material: First, prepare Zr-4 alloy tubing with an outer diameter of 9.5mm, an inner diameter of 8.36mm, and a length of 300mm. Grind the zirconium alloy substrate material sequentially with 100#, 200#, 400#, and 800# sandpaper. Then, ultrasonically clean it with alcohol and acetone for 20 minutes each time. After cleaning, place it in a drying oven to dry.

[0075] b. Substrate installation: The Zr-4 alloy tube after the above treatment is clamped in the fixture of the ultra-high speed laser cladding machine and its rotation process is kept stable;

[0076] c. Preheating the substrate: Rotate the machine tool fixture, hold the butane gas spray gun, and uniformly heat the Zr-4 alloy tube at 400℃ until the tube turns red-hot;

[0077] d. Cladding Coating: The ultra-high-speed laser cladding defocusing distance is set to +0mm, i.e., the working distance of the cladding head is 20.6mm, and the waiting time is set to 15s. During this process, the FeCrAl powder in the powder feeding cylinder is stirred and enters the powder feeding tray, and the powder discharge status is checked. High-purity argon gas (argon purity >99.9%) is used to blow the FeCrAl powder into the melting zone of the substrate surface. The flow rate of the powder feeder gas used in the ultra-high-speed cladding technology is 14L / min, the laser power is 250W, the cladding linear speed is 40m / min, the powder feeder tray rotation speed is 10%, and the single-pass transverse movement is 0.6mm. After obtaining the FeCrAl composite coating, the cladding is stopped, and the sample is taken out after natural cooling to room temperature.

[0078] e. Structural and compositional testing: such as Figures 1a-1b As shown, the coating is metallurgically bonded to the Zr-4 alloy tube. The coating has a uniform and fine structure, the thickness of the diluted layer is 20-40 μm, and there are no unmelted powder particles. Figure 2 This is a diagram showing the grain distribution and size of the coating. The grain size is between 10 and 30 μm. Figure 3The X-ray diffraction pattern shows that the main phase of the FeCrAl composite coating is a body-centered cubic Fe-Cr solid solution.

[0079] f. Mechanical property testing:

[0080] The coating-substrate bond strength was measured using the Revetest scratch test system. A load of 150 N was applied, and scratches on the coating surface were measured as follows: Figure 4 As shown, the coating completely fractured at approximately 90 N, therefore the coating adhesion is approximately 90 N. The surface roughness of the coating was measured using a VK-X1000 laser confocal microscope. Figures 5a-5b As shown, the surface roughness Ra of the coating prepared by ultra-high-speed laser cladding is 6.5 μm, while the surface roughness Ra of the coating prepared by traditional laser cladding is 44.1 μm. The roughness of the coating prepared by ultra-high-speed laser cladding technology is reduced by 37.6 μm, which greatly reduces the surface roughness. The microhardness of the coating was measured using an HV1000IS microhardness tester, with the loading load and time set to 0.05 kg and 10 s, respectively. To ensure the accuracy and representativeness of the data, 10 test points were selected for each sample measurement, and the average value of the 10 points was calculated as the final microhardness data of the coating. Figure 18 As shown, the hardness of the ultra-high-speed laser cladding coating is approximately 800 Hv. 0.05 Traditional laser cladding coatings have a hardness of approximately 450 Hv. 0.05 The hardness increased by 78%.

[0081] g. Antioxidant Performance Test: A high-temperature isothermal steam testing system (consisting of a peristaltic pump, steam generator, flow meter, and BTF-1400C series tubular furnace) was used to test the high-temperature steam oxidation performance of the prepared coating under a simulated LOCA environment. Samples were weighed before oxidation. The holding temperature was set at 1200℃, and the holding times were 10, 30, 45, 60, and 120 min. After oxidation, the samples were cooled to room temperature in the furnace and then weighed. The sample oxidation weight gain curve is shown in the figure. Figure 6 As shown, the sample growth curve is stable from 0 to 120 minutes. Figure 7 The images show SEM and EDS images of the cross-section of the FeCrAl composite coating after oxidation at 1200℃ for 60 min under high-temperature steam, indicating that the coating structure is intact. Figure 8 The image shows the X-ray diffraction pattern of the surface after oxidation. The coating surface forms a CrO2 and Al2O3 oxide film to protect the substrate, indicating that the coating can effectively protect the substrate from corrosion in a high-temperature water vapor environment of 1200℃ for 60 minutes.

[0082] Example 2

[0083] a. Pretreatment of the substrate material: First, prepare Zr-4 alloy tubing with an outer diameter of 9.5mm, an inner diameter of 8.36mm, and a length of 300mm. Grind the zirconium alloy substrate material sequentially with 100#, 200#, 400#, and 800# sandpaper. Then, ultrasonically clean it with alcohol and acetone for 20 minutes each time. After cleaning, place it in a drying oven to dry.

[0084] b. Substrate installation: The Zr-4 alloy tube after the above treatment is clamped in the fixture of the ultra-high speed laser cladding machine and its rotation process is kept stable;

[0085] c. Preheating the substrate: Rotate the machine tool fixture, hold the butane gas spray gun, and uniformly heat the Zr-4 alloy tube at 400℃ until the tube turns red-hot;

[0086] d. Cladding Coating: The ultra-high-speed laser cladding defocusing distance is set to +0mm, i.e., the working distance of the cladding head is 20.6mm, and the waiting time is set to 15s. During this process, the FeCrAl powder in the powder feeding cylinder is fed into the powder feeding tray. High-purity argon gas (argon purity >99.9%) is used to blow the FeCrAl powder into the melting zone of the substrate surface. The flow rate of the powder feeder gas used in the ultra-high-speed cladding technology is 14L / min, the laser power is 275W, the cladding linear speed is 40m / min, the powder feeder tray rotation speed is 10%, and the single-pass transverse movement is 0.6mm. After obtaining the FeCrAl composite coating, the cladding is stopped, and the sample is taken out after natural cooling to room temperature.

[0087] Example 3

[0088] a. Pretreatment of the substrate material: First, prepare Zr-4 alloy tubing with an outer diameter of 9.5mm, an inner diameter of 8.36mm, and a length of 300mm. Grind the zirconium alloy substrate material sequentially with 100#, 200#, 400#, and 800# sandpaper. Then, ultrasonically clean it with alcohol and acetone for 20 minutes each time. After cleaning, place it in a drying oven to dry.

[0089] b. Substrate installation: The Zr-4 alloy tube after the above treatment is clamped in the fixture of the ultra-high speed laser cladding machine and its rotation process is kept stable;

[0090] c. Preheating the substrate: Rotate the machine tool fixture, hold the butane gas spray gun, and uniformly heat the Zr-4 alloy tube at 400℃ until the tube turns red-hot;

[0091] d. Cladding Coating: The ultra-high-speed laser cladding defocusing distance is set to +0mm, i.e., the working distance of the cladding head is 20.6mm, and the waiting time is set to 15s. During this process, the FeCrAl powder in the powder feeding cylinder is fed into the powder feeding tray. High-purity argon gas (argon purity >99.9%) is used to blow the FeCrAl powder into the melting zone of the substrate surface. The flow rate of the powder feeder gas used in the ultra-high-speed cladding technology is 14L / min, the laser power is 300W, the cladding linear speed is 40m / min, the powder feeder tray rotation speed is 10%, and the single-pass transverse movement is 0.6mm. After obtaining the FeCrAl composite coating, the cladding is stopped, and the sample is taken out after natural cooling to room temperature.

[0092] Comparative Example 1

[0093] a. Pretreatment of the substrate material: First, prepare Zr-4 alloy tubing with an outer diameter of 9.5mm, an inner diameter of 8.36mm, and a length of 300mm. Grind the zirconium alloy substrate material sequentially with 100#, 200#, 400#, and 800# sandpaper. Then, ultrasonically clean it with alcohol and acetone for 20 minutes each time. After cleaning, place it in a drying oven to dry.

[0094] b. Substrate installation: The Zr-4 alloy tube after the above treatment is clamped in the fixture of the ultra-high speed laser cladding machine and its rotation process is kept stable;

[0095] c. Cladding Coating: The ultra-high-speed laser cladding defocusing distance is set to +0mm, i.e., the working distance of the cladding head is 20.6mm, and the waiting time is set to 15s. During this process, the FeCrAl powder in the powder feeding cylinder is fed into the powder feeding tray. High-purity argon gas (argon purity >99.9%) is used to blow the FeCrAl powder into the melting zone of the substrate surface. The flow rate of the powder feeder gas used in the ultra-high-speed cladding technology is 14L / min, the laser power is 275W, the cladding linear speed is 40m / min, the powder feeder tray rotation speed is 10%, and the single-pass transverse movement is 0.8mm. After obtaining the FeCrAl coating, the cladding is stopped, and the sample is taken out after naturally cooling to room temperature.

[0096] d. Structural and compositional testing: The coating exhibits a metallurgical bond with the substrate. The SEM image of the coating cross-section is shown below. Figure 11 As shown, the coating thickness is 15-20 μm, which is relatively thin. The coating has crack defects and the unmelted powder particles are relatively large.

[0097] e. Antioxidant Performance Test: The high-temperature isothermal steam testing system was used to test the high-temperature water vapor oxidation performance of the prepared coating under simulated LOCA environment. The sample was weighed before oxidation, and the holding temperature was set at 1200℃ for 60 min. After oxidation, the sample was cooled to room temperature in the furnace and then weighed. The oxidation weight gain was 3.183251 mg / cm³. 2The sample obtained by cladding with a preheated substrate had a weight gain of 3.017462 mg / cm³. 2 Compared to the previous method, the weight gain was significantly greater, and the cross-section of the sample after corrosion was as follows: Figure 12 As shown, the substrate has a large number of pores, which not only prevents the coating from providing protection, but also causes the substrate to fail due to the initiation of cracks.

[0098] Comparative Example 2

[0099] Due to the characteristics of traditional laser cladding, coatings cannot be clad onto pipes. Therefore, Zr-4 alloy plates are used for traditional laser cladding.

[0100] a. Pretreatment of the matrix material: First, prepare a Zr-4 alloy plate with a size of 10×15mm. Grind the zirconium alloy matrix material with 100#, 200#, 400# and 800# sandpaper in sequence. Then, use alcohol and acetone to ultrasonically clean it for 20 minutes in sequence. After cleaning, put it in a drying oven to dry.

[0101] b. Preheating of substrate installation: Place the Zr-4 alloy plate after the above treatment on the heating table, set the heating table to 300℃, and focus the laser red dot on the cladding start point on the sample.

[0102] c. Cladding Coating: The laser cladding defocusing distance is set to +0mm, i.e., the working distance of the cladding head is 20.6mm, and the waiting time is set to 20s. During this process, the FeCrAl powder in the powder feeding cylinder is fed into the powder feeding tray. High-purity argon gas (argon purity >99.9%) is used to blow the FeCrAl powder into the melting zone of the substrate surface. The flow rate of the powder feeder gas used in the cladding technology is 15L / min, the laser power is 300W, the laser speed is 8mm / s, the return speed is 15mm / s, the powder feeder tray rotation speed is 5%, the single-pass lateral movement is 1mm, and the single-pass length is 25mm. After obtaining the FeCrAl coating, the cladding is stopped, and the sample is taken out after naturally cooling to room temperature.

[0103] d. Structural and compositional testing: The coating exhibits a metallurgical bond with the substrate. The SEM image of the coating cross-section is shown below. Figure 13a * Figure 13b As shown, the coating thickness is about 1 mm, and there is a clear dilution layer with a thickness of 140–370 μm.

[0104] e. Antioxidant Performance Test: The high-temperature isothermal steam testing system was used to test the high-temperature water vapor oxidation performance of the prepared coating under simulated LOCA environment. The sample was weighed before oxidation, and the holding temperature was set at 1200℃ for 60 min. After oxidation, the sample was cooled to room temperature in the furnace and then weighed. The sample weight gain was 9.451597 mg / cm³. 2The sample obtained by ultra-high-speed laser cladding had a weight gain of 2.722357428 mg / cm³. 2 Compared to the previous method, the weight gain was significant, and the cross-section of the sample after corrosion was as follows: Figure 14 As shown, the coating contains a large amount of Zr element from the substrate tube, which dilutes the composition of the FeCrAl coating, causing changes in the alloy composition and relative content of elements in the FeCrAl coating. This alters the phase structure of the FeCrAl alloy, destroys the FeCrAl alloy's resistance to high-temperature steam oxidation, and thus reduces the high-temperature oxidation resistance of the FeCrAl coating.

[0105] Comparative Example 3

[0106] a. Pretreatment of the substrate material: First, prepare Zr-4 alloy tubing with an outer diameter of 9.5mm, an inner diameter of 8.36mm, and a length of 300mm. Grind the zirconium alloy substrate material sequentially with 100#, 200#, 400#, and 800# sandpaper. Then, ultrasonically clean it with alcohol and acetone for 20 minutes each time. After cleaning, place it in a drying oven to dry.

[0107] b. Substrate installation: The Zr-4 alloy tube after the above treatment is clamped in the fixture of the ultra-high speed laser cladding machine and its rotation process is kept stable;

[0108] c. Preheating the substrate: Rotate the machine tool fixture, hold the butane gas spray gun, and uniformly heat the Zr-4 alloy tube at 400℃ until the tube turns red-hot;

[0109] d. Cladding Coating: The ultra-high-speed laser cladding defocusing distance is set to +0mm, i.e., the working distance of the cladding head is 20.6mm, and the waiting time is set to 15s. During this process, the FeCrAl powder in the powder feeding cylinder is fed into the powder feeding tray. High-purity argon gas (argon purity >99.9%) is used to blow the FeCrAl powder into the melting zone of the substrate surface. The flow rate of the powder feeder gas used in the ultra-high-speed cladding technology is 14L / min, the laser power is 200W, the cladding linear speed is 40m / min, the powder feeder tray rotation speed is 10%, and the single-pass transverse movement is 0.6mm. After obtaining the FeCrAl coating, the cladding is stopped, and the sample is taken out after naturally cooling to room temperature.

[0110] e. Structural and compositional testing: SEM images of the coating cross-section are shown below. Figure 15 As shown, this process has relatively low power, the unmelted powder particles are large, and the coating cannot be completely formed.

[0111] Comparative Example 4

[0112] a. Pretreatment of the substrate material: First, prepare Zr-4 alloy tubing with an outer diameter of 9.5mm, an inner diameter of 8.36mm, and a length of 300mm. Grind the zirconium alloy substrate material sequentially with 100#, 200#, 400#, and 800# sandpaper. Then, ultrasonically clean it with alcohol and acetone for 20 minutes each time. After cleaning, place it in a drying oven to dry.

[0113] b. Substrate installation: The Zr-4 alloy tube after the above treatment is clamped in the fixture of the ultra-high speed laser cladding machine and its rotation process is kept stable;

[0114] c. Preheating the substrate: Rotate the machine tool fixture, hold the butane gas spray gun, and uniformly heat the Zr-4 alloy tube at 400℃ until the tube turns red-hot;

[0115] d. Cladding Coating: The ultra-high-speed laser cladding defocusing distance is set to +0mm, i.e., the working distance of the cladding head is 20.6mm, and the waiting time is set to 15s. During this process, the FeCrAl powder in the powder feeding cylinder is fed into the powder feeding tray. High-purity argon gas (argon purity >99.9%) is used to blow the FeCrAl powder into the melting zone of the substrate surface. The flow rate of the powder feeder gas used in the ultra-high-speed cladding technology is 14L / min, the laser power is 400W, the cladding linear speed is 40m / min, the powder feeder tray rotation speed is 10%, and the single-pass transverse movement is 0.6mm. After obtaining the FeCrAl coating, the cladding is stopped, and the sample is taken out after naturally cooling to room temperature.

[0116] e. Structural and compositional testing: Coating surface, such as... Figure 16 As shown, the coating cladding is uneven in a single pass, with obvious wrinkling. Excessive power leads to structural changes.

[0117] Comparative Example 5

[0118] a. Pretreatment of the substrate material: First, prepare Zr-4 alloy tubing with an outer diameter of 9.5mm, an inner diameter of 8.36mm, and a length of 300mm. Grind the zirconium alloy substrate material sequentially with 100#, 200#, 400#, and 800# sandpaper. Then, ultrasonically clean it with alcohol and acetone for 20 minutes each time. After cleaning, place it in a drying oven to dry.

[0119] b. Coating material preparation: Weigh 100g of each of the four different element ratios of coating powder using a precision balance. The element ratios are shown in Table 1.

[0120] Table 1. Composition of FeCrAl powder with different element ratios

[0121]

[0122] c. Substrate mounting: The Zr-4 alloy tube after the above treatment is clamped in the fixture of the ultra-high speed laser cladding machine and its rotation process is kept stable;

[0123] d. Preheating of the substrate: Rotate the machine tool fixture, hold the butane gas spray gun, and heat the Zr-4 alloy tube evenly at 400℃ until the tube turns red-hot;

[0124] e. Cladding Coating: The ultra-high-speed laser cladding defocusing distance is set to +0mm, i.e., the working distance of the cladding head is 20.6mm, and the waiting time is set to 15s. During this process, the FeCrAl powder in the powder feeding cylinder is fed into the powder feeding tray. High-purity argon gas (argon purity >99.9%) is used to blow the FeCrAl powder into the melting zone of the substrate surface. The flow rate of the powder feeder gas used in the ultra-high-speed cladding technology is 14L / min, the laser power is 250W, the cladding linear speed is 40m / min, the powder feeder tray rotation speed is 10%, and the single-pass transverse movement is 0.6mm. Four types of FeCrAl coatings are obtained. The cladding is stopped, and the samples are taken out after natural cooling to room temperature.

[0125] f. Coating Performance Testing: A high-temperature isothermal steam testing system (consisting of a peristaltic pump, steam generator, flow meter, and BTF-1400C series tubular furnace) was used to test the high-temperature steam oxidation performance of the prepared coating under a simulated LOCA environment. Samples were weighed before oxidation. The holding temperature was set at 1200℃, and the holding times were 10, 30, 45, 60, and 120 min. After oxidation, the samples were cooled to room temperature in the furnace and then weighed. The sample oxidation weight gain curve is shown in the figure. Figure 17 As shown, the coating with a powder element ratio of 68wt% Fe, 25wt% Cr, and 7wt% Al exhibits the lowest oxidation weight gain and the best resistance to water vapor oxidation. The microhardness of the coating was measured using an HV1000IS microhardness tester. Figure 18 It can be seen that the coating with the powder element ratio of 68wt%Fe, 25wt%Cr, and 7wt%Al has the highest hardness.

[0126] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0127] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. An FeCrAl composite coating for a zirconium alloy surface, characterized by: The FeCrAl composite coating comprises a metallurgical bonding layer and an FeCrAl cladding layer sequentially formed on the surface of a substrate. The FeCrAl composite coating is formed by cladding a FeCrAl alloy onto the surface of a zirconium alloy substrate using ultra-high-speed laser cladding technology. In the direction away from the substrate surface, the content of Fe, Cr, and Al elements in the metallurgical bonding layer gradually increases. The metallurgical bonding layer is mainly composed of Fe-Zr solid solutions and Cr-Zr solid solutions. The main phase of the FeCrAl cladding layer includes an α-Fe-based solid solution alloy with a body-centered cubic structure. The grain size of the FeCrAl cladding layer is 10~30 μm. The thickness of the FeCrAl cladding layer is 20~50 μm. The zirconium alloy substrate includes a Zr-4 alloy tube. The FeCrAl cladding layer comprises the following components by mass percentage: 68 wt% Fe, 25 wt% Cr, and 7 wt% Al. The method for preparing the FeCrAl composite coating for zirconium alloy surfaces includes: Provide zirconium alloy substrate; The zirconium alloy substrate is preheated to 200~500℃; A FeCrAl composite coating is obtained by cladding FeCrAl alloy onto the surface of a zirconium alloy substrate using ultra-high-speed laser cladding technology. The ultra-high-speed laser cladding technology employs a powder feeding gas flow rate of 14-15 L / min, a laser power of 250-300 W, a laser moving speed of 5-7 m / min, a cladding linear velocity of 20-40 m / min, a powder feeding rate of 3.9250 g / min, a single-pass lateral movement of 0.6-0.8 mm, and a distance of 17.5-19 mm between the laser head and the zirconium alloy substrate.

2. The FeCrAl composite coating according to claim 1, characterized in that: The thickness t of the metallurgical bonding layer is: 0 < t ≤ 60 μm.

3. The FeCrAl composite coating according to claim 1, characterized in that: The α-Fe-based solid solution alloy includes Fe-Cr solid solution; the Fe-Cr solid solution content in the FeCrAl composite coating is 74~88wt%.

4. The FeCrAl composite coating according to claim 1, characterized in that: The length of the Zr-4 alloy tube is 300~400mm.

5. The FeCrAl composite coating according to claim 1, characterized in that: The average particle size of the FeCrAl alloy is 10~30μm.

6. The FeCrAl composite coating according to claim 1, characterized in that: The FeCrAl alloy has a purity of 99.9 wt% or higher.

7. The FeCrAl composite coating according to claim 1, characterized in that: The FeCrAl alloy comprises the following components by mass percentage: 68wt% Fe, 25wt% Cr and 7wt% Al.

8. The FeCrAl composite coating according to claim 1, characterized in that: The powder feeding gas includes an inert gas.

9. The FeCrAl composite coating according to claim 1, characterized in that, The method for preparing the FeCrAl composite coating on the surface of zirconium alloy further includes: before performing the cladding process, grinding and cleaning the zirconium alloy substrate; wherein, the cleaning process includes: cleaning the surface of the zirconium alloy substrate obtained by grinding with ethanol and acetone in sequence, at least to remove grease.

10. Use of the FeCrAl composite coating according to any one of claims 1-9 in the protection of curved surface parts.

11. A fuel cladding device, characterized in that, It includes a zirconium alloy tube and a FeCrAl composite coating as described in any one of claims 1-9.

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