Cr-si alloy coating for zirconium alloy surface and its preparation method and application

Abstract

The application discloses a Cr-Si alloy coating for a zirconium alloy surface and a preparation method and application thereof. The Cr-Si alloy coating comprises an in-situ diffusion barrier layer and a Cr-Si cladding layer formed on the surface of a zirconium alloy substrate in sequence, and the Cr-Si alloy coating is formed by high-temperature vacuum annealing after super-high-speed laser cladding; the content of Si elements gradually increases in the direction from the outer surface to the surface of the zirconium alloy substrate; the main phase of the Cr-Si cladding layer comprises a Cr3Si compound with a cubic system of A15 type, and the in-situ diffusion barrier layer comprises a Zr2Si intermetallic compound. The Cr-Si alloy coating can reduce the mutual diffusion between Cr and Zr atoms, slow down the reaction speed of the cladding material with water vapor at high temperature, delay the core degradation process, and make the zirconium alloy substrate have excellent high-temperature oxidation resistance and mechanical properties.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of accident tolerant fuel coating, and particularly relates to a Cr-Si alloy coating for a zirconium alloy surface and a preparation method and application thereof. BACKGROUND

[0002] People pay great attention to the safety and reliability of nuclear power plants. Generally, the main reason for nuclear accidents is that the zirconium alloy cladding is rapidly oxidized in high-temperature water vapor under the condition of loss-of-coolant accidents (LOCA), which causes the cladding material to fail and release high-concentration hydrogen gas, and when the cladding is hydrogen embrittlement cracking, a serious explosion occurs. Therefore, the nuclear industry proposes the concept of accident tolerant fuel system, which aims to prevent the zirconium alloy from causing a nuclear accident due to temperature transients under the condition of LOCA.

[0003] At present, the Cr coating has good prospects and advantages, but the mechanical bonding and atomic diffusion between the coatings are a great challenge to the practicability of the coating. Compared with the coating prepared by cold spraying / magnetic sputtering technology, the ultra-high-speed laser cladding technology has superior technical advantages in the zirconium alloy coating, including improving the processing speed, reducing the dilution rate, minimizing thermal deformation, and good metallurgical bonding. However, at high temperatures, Zr can migrate through the grain boundary into the Cr coating, and react with Cr2O3 in the coating to cause coating failure, so that the Zr alloy substrate is oxidized. At the same time, the ZrO2 formed by the reaction can also significantly accumulate at the grain boundary, providing a short circuit channel for the inward diffusion of oxygen, further accelerating the oxidation of the substrate. SUMMARY

[0004] The main purpose of the present application is to provide a Cr-Si alloy coating for a zirconium alloy surface and a preparation method thereof, so as to overcome the deficiencies in the prior art.

[0005] Another purpose of the present application is to provide the application of the Cr-Si alloy coating for a zirconium alloy surface.

[0006] To achieve the foregoing purposes of the application, the technical solutions adopted by the present application include:

[0007] The first aspect of this invention provides a Cr-Si alloy coating for a zirconium alloy surface, comprising an in-situ diffusion barrier layer and a Cr-Si cladding layer sequentially formed on the surface of a zirconium alloy substrate. The Cr-Si alloy coating is formed by ultra-high-speed laser cladding on the zirconium alloy substrate surface followed by high-temperature vacuum annealing. The Si content in the Cr-Si alloy coating is 10 at% to 40 at%, and the Si content gradually increases from the outer surface of the Cr-Si alloy coating to the surface of the zirconium alloy substrate.

[0008] The main phase of the Cr-Si cladding layer includes Cr3Si compounds with an A15 cubic system, and the in-situ diffusion barrier layer includes Zr2Si intermetallic compounds.

[0009] A second aspect of this invention provides a method for preparing a Cr-Si alloy coating on a zirconium alloy surface, comprising:

[0010] Provide zirconium alloy matrix;

[0011] Cr-Si alloy powder is clad onto the surface of a zirconium alloy substrate using ultra-high-speed laser cladding technology, followed by high-temperature vacuum annealing to obtain a Cr-Si alloy coating for the zirconium alloy surface. The Cr-Si alloy powder comprises the following components by percentage: 10 at%~40 at% Si and 60 at%~90 at% Cr.

[0012] A third aspect of the present invention provides a Cr-Si alloy coating for zirconium alloy surfaces prepared by the above-described preparation method.

[0013] A fourth aspect of the present invention provides the use of the Cr-Si alloy coating for zirconium alloy surfaces in the protection of zirconium alloy parts.

[0014] Accordingly, a fifth aspect of the present invention provides a fuel cladding device comprising a zirconium alloy tube having the aforementioned Cr-Si alloy coating for the zirconium alloy surface disposed thereon.

[0015] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0016] 1) The present invention prepares a Cr-Si alloy coating on the surface of a zirconium alloy substrate by ultra-high speed laser cladding. The coating forms a metallurgical bond with the substrate. Compared with traditional cladding, the treated zirconium alloy tube has better resistance to high temperature oxidation.

[0017] 2) This invention performs vacuum annealing after ultra-high-speed laser cladding to improve the dimensional stability of the material and reduce internal stress concentration, thereby avoiding potential risks such as deformation and cracking caused by stress release during subsequent service.

[0018] 3) The Cr-Si alloy coating prepared by this invention can be oxidized by water vapor at 1100℃ for 60 min and maintain the integrity of the coating structure without peeling. The good adhesion improves the coating's anti-oxidation performance in the steam environment and prevents it from falling off in the high-temperature water vapor environment. At the same time, it reduces the interdiffusion of Cr-Zr atoms under high-temperature conditions, and the Cr and Si mixed oxide film formed on the coating surface 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, and it exhibits excellent high-temperature oxidation corrosion resistance and mechanical properties. Attached Figure Description

[0019] 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.

[0020] Figure 1 This is a cross-sectional schematic diagram of a Cr-Si alloy coating used on a zirconium alloy surface in a typical embodiment of the present invention;

[0021] Figure 2 This is a CrSi obtained in Example 1 of the present invention. 10 SEM image of the coating section;

[0022] Figure 3 This is a CrSi obtained in Example 2 of the present invention. 20 SEM image of the coating section;

[0023] Figure 4 This is a CrSi obtained in Example 3 of the present invention. 40 SEM image of the coating section;

[0024] Figure 5 This is a cross-sectional SEM image of a Cr coating prepared in Comparative Example 1 of the present invention;

[0025] Figure 6 These are the X-ray diffraction patterns of the coatings obtained in Examples 1-3 and Comparative Example 1 of this invention;

[0026] Figure 7 These are the coating hardness distribution diagrams obtained in Examples 1-3 and Comparative Example 1 of the present invention;

[0027] Figure 8 This is a graph showing the weight gain per unit area of ​​the coatings obtained in Examples 1-3 and Comparative Example 1 under water vapor at 1100°C.

[0028] Figure 9 These are X-ray diffraction patterns of the oxidized coatings obtained in Examples 1-3 and Comparative Example 1 of this invention;

[0029] Figure 10 This is a CrSi obtained in Example 1 of the present invention. 10 SEM image of the cross section after coating oxidation;

[0030] Figure 11 This is a CrSi obtained in Example 2 of the present invention. 20 SEM image of the cross section after coating oxidation;

[0031] Figure 12 This is a CrSi obtained in Example 3 of the present invention. 40 SEM image of the cross section after coating oxidation;

[0032] Figure 13 This is a cross-sectional SEM image of a Cr coating obtained in Comparative Example 1 of this invention after oxidation. Detailed Implementation

[0033] Currently, the most common method to address atomic interdiffusion at the Cr coating / Zr substrate interface is to introduce a diffusion barrier layer at the interface, thereby reducing the diffusion rate by increasing the atomic diffusion activation energy. Considering the similarity between the atomic radii of Si and Cr, Si can rapidly diffuse to the interface at high temperatures and react with Zr atoms. The resulting Zr2Si phase exhibits better stability than the ZrCr2 phase, and the diffusion activation energy of Zr atoms through the Zr2Si phase is also higher than that through the ZrCr2 phase. Therefore, through long-term research and extensive practice, the inventors of this invention have proposed the technical solution of this invention, which mainly employs ultra-high-speed laser cladding technology to prepare a Cr-Si metal anti-oxidation coating on the surface of a zirconium alloy substrate. This coating demonstrates superior performance in suppressing the interdiffusion of Cr and Zr atoms.

[0034] The following will further explain the technical solution, its implementation process, and its principles. However, it should be understood that within the scope of this invention, the above-mentioned technical features of this invention and the technical features specifically described below (in embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here.

[0035] As one aspect of the technical solution of the present invention, a Cr-Si alloy coating for the surface of a zirconium alloy includes an in-situ diffusion barrier layer and a Cr-Si cladding layer sequentially formed on the surface of a zirconium alloy substrate. The Cr-Si alloy coating is formed by cladding Cr-Si alloy powder onto the surface of the zirconium alloy substrate using ultra-high speed laser cladding followed by high-temperature vacuum annealing. The Si content in the Cr-Si alloy coating is 10 at% to 40 at%, and the Si content gradually increases from the outer surface of the Cr-Si alloy coating to the surface of the zirconium alloy substrate. Its formation mechanism depends on the synergistic effect of ultra-high speed laser cladding and high-temperature vacuum annealing.

[0036] In some embodiments, the Cr-Si alloy coating of the present invention can form a metallurgical bond with the zirconium alloy substrate, and the coating structure is uniform and fine, which can reduce the interdiffusion between Cr-Zr atoms. The main phase of the Cr-Si cladding layer includes Cr3Si compounds with an A15 type cubic system.

[0037] Furthermore, the Cr3Si compound includes a Cr-Si solid solution, and the content of the Cr-Si solid solution in the Cr-Si cladding layer is greater than 80 at.

[0038] In some embodiments, the grain size of the Cr-Si cladding layer is ≤5μm.

[0039] In some preferred embodiments, the thickness of the Cr-Si cladding layer is 10 μm to 40 μm.

[0040] In some embodiments, the in-situ diffusion barrier layer comprises a Zr₂Si intermetallic compound. Further, after high-temperature steam oxidation, the in-situ diffusion barrier layer is mainly composed of a Zr₂Si intermetallic compound and a ZrCrSi intermetallic compound.

[0041] In some preferred embodiments, the thickness of the in-situ diffusion barrier layer is 10 μm to 40 μm.

[0042] In some preferred embodiments, the zirconium alloy matrix includes, but is not limited to, a Zr-4 alloy tube.

[0043] Furthermore, the length of the Zr-4 alloy tube is 100 mm to 400 mm.

[0044] In summary, the Cr-Si alloy coating of this invention can maintain the integrity of the coating structure without peeling during oxidation at 1100℃ for 60 minutes using steam. The good adhesion improves the coating's oxidation resistance in a steam environment, preventing it from peeling off under high-temperature steam conditions. At the same time, it reduces the interdiffusion of Cr-Zr atoms under high-temperature conditions, and the mixed oxide film of Cr and Si formed on the coating surface during oxidation effectively blocks oxygen from diffusing from the external environment to the coating and substrate, effectively protecting the substrate. It also exhibits low oxidation weight gain and good resistance to high-temperature oxidation corrosion.

[0045] The Cr-Si alloy coating of this invention can slow down the reaction rate of the cladding material with water vapor at high temperatures, delay the core degradation process, and enable the zirconium alloy tube to have better high-temperature oxidation resistance and good mechanical properties, thereby reducing the risk of damage to the zirconium alloy cladding in accident environments.

[0046] As another aspect of the technical solution of the present invention, it relates to a method for preparing a Cr-Si alloy coating for a zirconium alloy surface, comprising:

[0047] Provide zirconium alloy matrix;

[0048] Cr-Si alloy powder was fused onto the surface of a zirconium alloy substrate using ultra-high-speed laser cladding technology, followed by high-temperature vacuum annealing to obtain a Cr-Si alloy coating for use on the zirconium alloy surface.

[0049] In some embodiments, the average particle size of the Cr-Si alloy powder is ≤5 μm.

[0050] In some embodiments, the purity of the Cr-Si alloy powder is above 99.9 at%.

[0051] In some embodiments, the Cr-Si alloy powder comprises the following components by percentage: 10 at% to 40 at% Si and 60 at% to 90 at% Cr.

[0052] In some embodiments, the preparation method specifically includes: using ultra-high-speed laser cladding technology to clad the Cr-Si alloy powder onto the surface of a zirconium alloy substrate to obtain a Cr-Si alloy coating; wherein the ultra-high-speed laser cladding technology uses a powder feeding gas flow rate of 5~15L / min, a laser power of 300~500W, a cladding linear velocity of 10~20m / min, a powder feeding amount of 3~4g / min, a single-pass lateral movement of 0.4~0.6mm, and a defocusing amount of +2~3mm, where "+" indicates that the focal point where the laser and powder converge is above the workpiece.

[0053] The main mechanism of the ultra-high-speed laser cladding technology in this invention lies in the following: When preparing alloy coatings using ultra-high-speed laser cladding, the non-equilibrium rapid solidification of the molten pool intensifies the thermal stress within the coating. This increases the risk of coating cracking and peeling due to stress concentration under high-temperature steam oxidation conditions. Therefore, high-temperature vacuum annealing is used to eliminate residual stress within the coating, thereby ensuring the long-term stability of the coating's protective performance. Furthermore, although Si elements in the coating accumulate near the interface between the coating and the zirconium alloy substrate during laser cladding, this accumulation effect is not significant due to the rapid solidification of the molten pool. However, the subsequent high-temperature vacuum annealing process further enriches Si elements at the interface. Thus, the synergistic effect of ultra-high-speed laser cladding and high-temperature vacuum annealing enhances Si enrichment at the interface.

[0054] Furthermore, the powder feeding gas includes, but is not limited to, inert gases such as argon.

[0055] In some embodiments, the preparation method specifically includes: after cladding treatment, subjecting the obtained Cr-Si alloy coating to high-temperature vacuum annealing treatment within a temperature range of 900℃ to 1100℃; wherein the vacuum degree of the vacuum annealing treatment is as low as 10. -3 The Pa and the holding time are set to 1~2h, and the furnace is cooled to room temperature after annealing.

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

[0057] In some more specific embodiments, the present invention provides a method for preparing a Cr-Si alloy coating for a zirconium alloy surface, at a density of 10 × 10⁻⁶. 6 Under a high cooling rate of K / s and a 50% overlap, the coating microstructure is controlled to achieve a uniform and fine texture, improving oxidation resistance. Simultaneously, it effectively avoids performance "contamination" caused by 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:

[0058] 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.

[0059] 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;

[0060] c. Cladding coating: Cr-Si alloy powder is blown into the melting zone on the surface of the substrate using a powder feeding gas; wherein, the flow rate of the powder feeding gas used in the cladding technology is 5~15L / min, the laser power is 300~500W, the cladding linear speed is 10~20m / min, the powder feeding amount is 3~4g / min, the single-pass transverse movement is 0.4~0.6mm, and the defocusing amount is +2~3mm, to obtain a Cr-Si alloy coating, the cladding is stopped, and the substrate is allowed to cool naturally to room temperature.

[0061] d. Post-coating treatment: The prepared Cr-Si alloy coating was subjected to vacuum annealing in the temperature range of 900℃~1100℃, with a holding time of 1~2h, and then cooled in the furnace.

[0062] Furthermore, the powder-feeding gas is argon.

[0063] Furthermore, the purity of the Cr-Si alloy powder is above 99.9%.

[0064] Furthermore, during the cladding process, the fixture maintains a high-speed rotation of 20 m / min, and the coating is clad using an ultra-high-speed laser cladding process.

[0065] Furthermore, at a laser power of 400W, 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.

[0066] Furthermore, annealing is performed in a vacuum environment at 900℃~1100℃ to eliminate the risk of cracking due to stress concentration inside the coating, while promoting the formation of Zr2Si and ZrCrSi barrier layers (i.e., in-situ diffusion barrier layers) near the interface.

[0067] The Cr-Si alloy coating of this invention can form a metallurgical bond with the substrate, and the coating microstructure is uniform and fine. This can reduce the reaction rate of the cladding material with water vapor at high temperatures, delay the core degradation process, and the coating strength is as high as 10¹⁶ HV. 0.1 This gives zirconium alloy tubes superior resistance to high-temperature oxidation and good mechanical properties.

[0068] As another aspect of the technical solution of the present invention, it also relates to a Cr-Si alloy coating for zirconium alloy surface prepared by the aforementioned preparation method.

[0069] As another aspect of the technical solution of the present invention, it also relates to the use of the Cr-Si alloy coating for zirconium alloy surfaces in the protection of zirconium alloy parts with curved surfaces.

[0070] Another aspect of the present invention provides a fuel cladding device, which includes a zirconium alloy tube, the surface of which is provided with a Cr-Si alloy coating for the zirconium alloy surface prepared by the aforementioned preparation method.

[0071] 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.

[0072] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0073] In this invention, each sample was tested three times to ensure the authenticity and reliability of the oxidative weight gain data.

[0074] Example 1

[0075] 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 400#, 800#, 1200#, and 2000# sandpaper. Then, ultrasonically clean it with alcohol and acetone for 20 minutes each time. After cleaning, place it in a drying oven to dry.

[0076] 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;

[0077] c. Cladding Coating: The ultra-high-speed laser cladding defocusing distance is set to +2~3mm, and the waiting time is set to 15s. During this process, the Cr-Si 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 90at%Cr + 10at%Si mixed powder into the melting zone of the substrate surface. The ultra-high-speed cladding technology uses a powder feeder gas flow rate of 10L / min, a laser power of 400W, a cladding linear velocity of 20m / min, a powder feeding rate of 3.5g / min, and a single-pass lateral movement of 0.5mm to obtain CrSi. 10 After the alloy coating is applied, the melting and cladding process is stopped, and the sample is removed after it has cooled naturally to room temperature.

[0078] d. Post-coating treatment: The prepared alloy coating is annealed in a vacuum tube at 1100℃, where the vacuum level is as low as 10. -3 Pa, held at that temperature for 1 hour, then cooled in the furnace to obtain a Cr-Si alloy coating (hereinafter referred to as "CrSi") for use on the surface of the zirconium alloy. 10coating").

[0079] e. Structural and compositional testing: Figure 1 and Figure 2 For the obtained CrSi 10 SEM image of the coating section, as shown Figure 2 As shown, the microstructure is uniform and fine, the coating is dense and free of defects such as cracks, and the coating is metallurgically bonded to the Zr-4 alloy tube. The thickness of the in-situ diffusion barrier layer and the Cr-Si cladding layer is 10~40μm, and there are no unmelted powder particles. Figure 6 The X-ray diffraction pattern shows that the main phase of the Cr-Si cladding layer is a cubic Cr phase. The in-situ diffusion barrier layer is a Zr₂Si intermetallic compound, and within the CrSi... 10 The Si content gradually increases from the outer surface of the coating to the surface of the zirconium alloy substrate.

[0080] f. Mechanical property testing:

[0081] The microhardness of the coating was measured using an HV1000IS microhardness tester, with the loading load and time set to 0.1 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 7 As shown, CrSi 10 The coating has a hardness exceeding 796 HV. 0.1 The hardness of the matrix is ​​approximately 230 HV. 0.1 The hardness is increased by at least 71%.

[0082] g. Antioxidant Performance Test: The high-temperature isothermal steam testing system (thermogravimetric analyzer) was used to test the high-temperature steam oxidation performance of the prepared coating under simulated LOCA environment. The samples were weighed before oxidation, and the holding temperature was set at 1100℃ for 60 min. After oxidation, the samples were cooled to room temperature in the furnace. The oxidation weight gain curve of the samples was obtained from... Figure 8 As shown, the sample growth curve is stable from 0 to 60 minutes. Figure 9 The image shows the X-ray diffraction pattern of the surface after oxidation. A Cr2O3-SiO2 oxide film is formed on the coating surface to protect the substrate, indicating that the coating can effectively protect the substrate from corrosion in a high-temperature water vapor environment of 1100℃ for 60 minutes. Figure 10 CrSi 10 The cross-sectional phase diagram of the coating after oxidation under high temperature water vapor at 1100℃ shows that it was not fully oxidized after 60 min of oxidation. An obvious in-situ diffusion barrier layer was formed at the interface, which was mainly composed of Zr2Si intermetallic compounds and ZrCrSi intermetallic compounds. A small amount of diffusion phenomenon occurred in the coating.

[0083] Example 2

[0084] 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 400#, 800#, 1200#, and 2000# sandpaper. Then, ultrasonically clean it with alcohol and acetone for 20 minutes each time. After cleaning, place it in a drying oven to dry.

[0085] 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;

[0086] c. Cladding Coating: The ultra-high-speed laser cladding defocusing distance is set to +2~3mm, and the waiting time is set to 15s. During this process, the Cr-Si 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 80at%Cr + 20at%Si mixed powder into the melting zone of the substrate surface. The ultra-high-speed cladding technology uses a powder feeder gas flow rate of 10L / min, a laser power of 400W, a cladding linear velocity of 20m / min, a powder feeding rate of 3.5g / min, and a single-pass lateral movement of 0.5mm to obtain CrSi. 20 After the alloy coating is applied, the melting and cladding process is stopped, and the sample is removed after it has cooled naturally to room temperature.

[0087] d. Post-coating treatment: The prepared alloy coating is annealed in a vacuum tube at 1100℃, where the vacuum level is as low as 10. -3 Pa, held at that temperature for 1 hour, then cooled in the furnace to obtain a Cr-Si alloy coating (hereinafter referred to as "CrSi") for use on the surface of the zirconium alloy. 20 coating").

[0088] e. Structural and component testing: such as Figure 3 As shown, the microstructure is uniform and fine, CrSi 20 The coating is dense and free of cracks and other defects. It exhibits a metallurgical bond with the Zr-4 alloy tube. The thickness of the in-situ diffusion barrier layer and the Cr-Si cladding layer ranges from 10 to 40 μm, and no unmelted powder particles are present. Figure 6 The X-ray diffraction pattern shows that the main phase of the Cr-Si cladding layer is the A15 cubic Cr3Si phase. The in-situ diffusion barrier layer is a Zr2Si intermetallic compound, and the CrSi... 20 The Si content gradually increases from the outer surface of the coating to the surface of the zirconium alloy substrate.

[0089] f. Mechanical property testing:

[0090] The microhardness of the coating was measured using an HV1000IS microhardness tester, with the loading load and time set to 0.1 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 7 As shown, CrSi 20 The coating has a hardness exceeding 912 HV. 0.1 The hardness of the matrix is ​​approximately 230 HV. 0.1 The hardness is increased by at least 74%.

[0091] g. Antioxidant Performance Test: The high-temperature isothermal steam testing system (thermogravimetric analyzer) was used to test the high-temperature steam oxidation performance of the prepared coating under simulated LOCA environment. The samples were weighed before oxidation, and the holding temperature was set at 1100℃ for 60 min. After oxidation, the samples were cooled to room temperature in the furnace. The oxidation weight gain curve of the samples was obtained from... Figure 8 As shown, the sample growth curve is stable from 0 to 60 minutes. Figure 9 The image shows the X-ray diffraction pattern of the surface after oxidation. A Cr2O3-SiO2 oxide film is formed on the coating surface to protect the substrate, indicating that the coating can effectively protect the substrate from corrosion in a high-temperature water vapor environment of 1100℃ for 60 minutes. Figure 11 CrSi 20 The cross-sectional phase diagram of the coating after oxidation under high temperature water vapor at 1100℃ shows that it was not fully oxidized after 60 min of oxidation. An obvious in-situ diffusion barrier layer was formed at the interface, which was mainly composed of Zr2Si intermetallic compounds and ZrCrSi intermetallic compounds. No obvious diffusion phenomenon occurred in the coating.

[0092] Example 3

[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 400#, 800#, 1200#, and 2000# 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 +2~3mm, and the waiting time is set to 15s. During this process, the Cr-Si 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 60at%Cr + 40at%Si mixed powder into the melting zone of the substrate surface. The ultra-high-speed cladding technology uses a powder feeder gas flow rate of 10L / min, a laser power of 400W, a cladding linear velocity of 20m / min, a powder feeding rate of 3.5g / min, and a single-pass lateral movement of 0.5mm to obtain CrSi. 40 After the alloy coating is applied, the melting and cladding process is stopped, and the sample is removed after it has cooled naturally to room temperature.

[0096] d. Post-coating treatment: The prepared alloy coating is annealed in a vacuum tube at 1100℃, where the vacuum level is as low as 10. -3 Pa, held at that temperature for 1 hour, then cooled in the furnace to obtain a Cr-Si alloy coating (hereinafter referred to as "CrSi") for use on the surface of the zirconium alloy. 40 coating").

[0097] e. Structural and component testing: such as Figure 4 As shown, the microstructure is uniform and fine, CrSi 40 The coating is dense and free of cracks and other defects. It exhibits a metallurgical bond with the Zr-4 alloy tube. The thickness of the in-situ diffusion barrier layer and the Cr-Si cladding layer ranges from 10 to 40 μm, and no unmelted powder particles are present. Figure 6 The X-ray diffraction pattern shows that the main phase of the Cr-Si cladding layer is the A15 cubic Cr3Si phase. The in-situ diffusion barrier layer is a Zr2Si intermetallic compound, and the CrSi... 40 The Si content gradually increases from the outer surface of the coating to the surface of the zirconium alloy substrate.

[0098] f. Mechanical property testing:

[0099] The microhardness of the coating was measured using an HV1000IS microhardness tester, with the loading load and time set to 0.1 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 7 As shown, CrSi 40 The coating has a hardness exceeding 1016 HV. 0.1 The hardness of the matrix is ​​approximately 230 HV. 0.1 The hardness is increased by at least 77%.

[0100] g. Antioxidant Performance Test: The high-temperature isothermal steam testing system (thermogravimetric analyzer) was used to test the high-temperature steam oxidation performance of the prepared coating under simulated LOCA environment. The samples were weighed before oxidation, and the holding temperature was set at 1100℃ for 60 min. After oxidation, the samples were cooled to room temperature in the furnace. The oxidation weight gain curve of the samples was obtained from... Figure 8 As shown, the sample growth curve is stable from 0 to 60 minutes. Figure 9 The image shows the X-ray diffraction pattern of the surface after oxidation. A Cr2O3-SiO2 oxide film is formed on the coating surface to protect the substrate, indicating that the coating can effectively protect the substrate from corrosion in a high-temperature water vapor environment of 1100℃ for 60 minutes. Figure 12 CrSi 40 The cross-sectional phase diagram of the coating after oxidation under high temperature water vapor at 1100℃ shows that it was not fully oxidized after 60 min. There is obvious Si enrichment in the entire coating. The in-situ diffusion barrier layer is mainly composed of Zr2Si intermetallic compound and ZrCrSi intermetallic compound.

[0101] Example 4

[0102] 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 400#, 800#, 1200#, and 2000# sandpaper. Then, ultrasonically clean it with alcohol and acetone for 20 minutes each time. After cleaning, place it in a drying oven to dry.

[0103] 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;

[0104] c. Cladding Coating: The ultra-high-speed laser cladding defocusing distance is set to +2~3mm, and the waiting time is set to 15s. During this process, the Cr-Si 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 80at%Cr + 20at%Si mixed powder into the melting zone of the substrate surface. The ultra-high-speed cladding technology uses a powder feeder gas flow rate of 5 L / min, a laser power of 300W, a cladding linear velocity of 10m / min, a powder feeding rate of 3 g / min, and a single-pass lateral movement of 0.4mm to obtain CrSi. 20 After the alloy coating is applied, the melting and cladding process is stopped, and the sample is removed after it has cooled naturally to room temperature.

[0105] d. Post-coating treatment: The prepared alloy coating is annealed in a vacuum tube at 1000℃, where the vacuum level is as low as 10. -3 Pa, the holding time is 1.5 hours, and then it is cooled with the furnace.

[0106] e. Structure and composition testing: The results are basically consistent with those in Example 2.

[0107] f. Mechanical performance test: The results are basically consistent with those in Example 2.

[0108] g. Antioxidant performance test: The results are basically consistent with those in Example 2.

[0109] Example 5

[0110] 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 400#, 800#, 1200#, and 2000# sandpaper. Then, ultrasonically clean it with alcohol and acetone for 20 minutes each time. After cleaning, place it in a drying oven to dry.

[0111] 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;

[0112] c. Cladding Coating: The ultra-high-speed laser cladding defocusing distance is set to +2~3mm, and the waiting time is set to 15s. During this process, the Cr-Si 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 80at%Cr + 20at%Si mixed powder into the melting zone of the substrate surface. Specifically, the ultra-high-speed cladding technology uses a powder feeder gas flow rate of 15 L / min, a laser power of 500W, a cladding linear velocity of 20m / min, a powder feeding rate of 4g / min, and a single-pass lateral movement of 0.6mm to obtain CrSi. 20 After the alloy coating is applied, the melting and cladding process is stopped, and the sample is removed after it has cooled naturally to room temperature.

[0113] d. Post-coating treatment: The prepared alloy coating is annealed in a vacuum tube at 900℃, with a vacuum level as low as 10. -3 Pa, the holding time is 2 hours, and then it is cooled with the furnace.

[0114] e. Structure and composition testing: The results are basically consistent with those in Example 2.

[0115] f. Mechanical performance test: The results are basically consistent with those in Example 2.

[0116] g. Antioxidant performance test: The results are basically consistent with those in Example 2.

[0117] Comparative Example 1

[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 400#, 800#, 1200#, and 2000# 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. 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;

[0120] c. Cladding Coating: The ultra-high-speed laser cladding defocusing distance is set to +2~3mm, and the waiting time is set to 15s. During this process, the Cr 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 Cr powder into the melting zone of the substrate surface. The ultra-high-speed cladding technology uses a powder feeder gas flow rate of 10L / min, a laser power of 400W, a cladding linear speed of 20m / min, a powder feeding amount of 3.5g / min, and a single-pass transverse movement of 0.5mm to obtain a metallic Cr coating. The cladding is then stopped, and the sample is taken out after natural cooling to room temperature.

[0121] d. Post-coating treatment: The prepared alloy coating is annealed in a vacuum tube at 1100℃, where the vacuum level is as low as 10. -3 Pa, heat preservation time is 1 hour, then cooled with the furnace.

[0122] e. Structural and component testing: such as Figure 5 As shown, the microstructure is uniform and fine, the coating is dense and free of defects such as cracks, and the coating is metallurgically bonded to the Zr-4 alloy tube. The thickness is 10~40μm, and there are no unmelted powder particles. Figure 6 The X-ray diffraction pattern shows that the main phase of the Cr coating is a cubic Cr phase.

[0123] f. Mechanical property testing:

[0124] The microhardness of the coating was measured using an HV1000IS microhardness tester, with the loading load and time set to 0.1 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 7 As shown, the hardness of the ultra-high-speed laser cladding coating (Cr coating) exceeds 775 HV. 0.1 The hardness of the matrix is ​​approximately 230 HV. 0.1 The hardness is increased by at least 70%.

[0125] g. Antioxidant Performance Test: The high-temperature isothermal steam testing system (thermogravimetric analyzer) was used to test the high-temperature steam oxidation performance of the prepared coating under simulated LOCA environment. The samples were weighed before oxidation, and the holding temperature was set at 1100℃ for 60 min. After oxidation, the samples were cooled to room temperature in the furnace. The oxidation weight gain curve of the samples was obtained from... Figure 8 As shown, the sample growth curve is stable from 0 to 60 minutes. Figure 9 The image shows the X-ray diffraction pattern of the surface after oxidation. A Cr2O3 oxide film is formed on the coating surface to protect the substrate. Although the coating can also effectively protect the substrate from corrosion in a high-temperature water vapor environment of 1100℃ for 60 minutes. Figure 13 The image shows the cross-sectional phase of a Cr coating oxidized under 1100℃ high-temperature steam, but significant diffusion occurs in the coating. This indicates that adding an appropriate amount of Si can effectively alleviate the accelerated coating failure caused by Zr diffusion into the coating during high-temperature steam oxidation. Therefore, compared to pure Cr coatings, adding an appropriate amount of Si can reduce the oxidation weight gain per unit area, the oxidation depth, and extend the effective protection time of the coating.

[0126] Comparative Example 2

[0127] The difference between this comparative example and Example 2 is that the high-temperature vacuum annealing treatment in step d was not performed.

[0128] The obtained coating structure and composition were tested, and the results are as follows: the microstructure is uniform and fine, and the CrSi... 20 The coating is dense and free of defects such as cracks, and it is metallurgically bonded to the Zr-4 alloy tube. The thickness of the in-situ diffusion barrier layer and the Cr-Si cladding layer is 10~40μm, and there are no unmelted powder particles. However, the concentration gradient of Si element content is not significant in the direction from the outer surface of the coating to the surface of the zirconium alloy substrate.

[0129] Antioxidant performance test: The high-temperature isothermal steam test system (thermogravimetric analyzer) was used to test the high-temperature steam oxidation performance of the prepared coating under simulated LOCA environment. The sample was weighed before oxidation, the holding temperature was set at 1100℃ and the holding time was 60min. After oxidation, the sample was cooled to room temperature in the furnace. The surface of the coating was found to have obvious cracks and obvious diffusion phenomena inside the coating.

[0130] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A Cr-Si alloy coating for zirconium alloy surfaces, characterized in that, include: An in-situ diffusion barrier layer and a Cr-Si cladding layer are sequentially formed on the surface of a zirconium alloy substrate. The Cr-Si alloy coating is formed by ultra-high-speed laser cladding on the surface of the zirconium alloy substrate followed by high-temperature vacuum annealing. The Si content in the Cr-Si alloy coating is 10 at% to 40 at%, and the Si content gradually increases from the outer surface of the Cr-Si alloy coating to the surface of the zirconium alloy substrate. The main phase of the Cr-Si cladding layer includes Cr3Si compounds with an A15 cubic system, and the in-situ diffusion barrier layer includes Zr2Si intermetallic compounds.

2. The Cr-Si alloy coating for zirconium alloy surfaces according to claim 1, characterized in that: The grain size of the Cr-Si cladding layer is ≤5μm; And / or, the thickness of the Cr-Si cladding layer is 10 μm to 40 μm; And / or, the Cr3Si compound includes a Cr-Si solid solution, and the Cr-Si solid solution content in the Cr-Si cladding layer is greater than 80 at.

3. The Cr-Si alloy coating for zirconium alloy surfaces according to claim 1, characterized in that: The thickness of the in-situ diffusion barrier layer is 10μm~40μm; And / or, after high-temperature steam oxidation, the in-situ diffusion barrier layer is mainly composed of Zr2Si intermetallic compounds and ZrCrSi intermetallic compounds; And / or, the zirconium alloy matrix includes a Zr-4 alloy tube; the length of the Zr-4 alloy tube is 100 mm to 400 mm.

4. A method for preparing a Cr-Si alloy coating for zirconium alloy surfaces, characterized in that, include: Provide zirconium alloy matrix; Cr-Si alloy powder is clad onto the surface of a zirconium alloy substrate using ultra-high-speed laser cladding technology, followed by high-temperature vacuum annealing to obtain a Cr-Si alloy coating for the zirconium alloy surface. The Cr-Si alloy powder comprises the following components by percentage: 10 at%~40 at% Si and 60 at%~90 at% Cr.

5. The preparation method according to claim 4, characterized in that: The average particle size of the Cr-Si alloy powder is ≤5μm; And / or, the purity of the Cr-Si alloy powder is above 99.9 at%.

6. The preparation method according to claim 4, characterized in that: The ultra-high-speed laser cladding technology uses a powder feeding gas flow rate of 5~15L / min, a laser power of 300~500W, a cladding linear speed of 10~20m / min, a powder feeding amount of 3~4g / min, a single-pass lateral movement of 0.4~0.6mm, and a defocusing amount of +2~3mm.

7. The preparation method according to claim 6, characterized in that: The high-temperature vacuum annealing process is performed at temperatures ranging from 900℃ to 1100℃, with a vacuum level as low as 10. -3 Pa, heat preservation time is 1~2 hours; And / or, the powder feeding gas includes an inert gas; And / or, the preparation method further includes: grinding and cleaning the zirconium alloy substrate before cladding the Cr-Si alloy powder; wherein the cleaning process includes: cleaning the surface of the polished zirconium alloy substrate with ethanol and / or acetone.

8. The use of the Cr-Si alloy coating for zirconium alloy surfaces as described in any one of claims 1 to 3 in the protection of zirconium alloy parts.

9. A fuel cladding device, characterized in that, The invention includes a zirconium alloy tube, the surface of which is provided with a Cr-Si alloy coating for the zirconium alloy surface as described in any one of claims 1 to 3.

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