A high-temperature sprayed iron-based composite material coating and its preparation method

Abstract

This invention relates to the field of composite material coating technology, specifically to a high-temperature sprayed iron-based composite material coating and its preparation method, comprising the following steps: S1. Grinding the surface protrusions of the substrate, cleaning and degreasing it, ultrasonically cleaning it with anhydrous ethanol and drying it, and then sandblasting it with white corundum to obtain a pretreated substrate; S2. Preheating the pretreated substrate, and spraying modified spraying powder onto the surface of the substrate to obtain a sprayed substrate; S3. Cutting the sprayed substrate into discs, remelting the discs using a remelting device, and cooling them to room temperature to obtain a high-temperature sprayed iron-based composite material coating. This invention effectively improves the coating's bonding strength, pitting resistance, and wear resistance through the synergistic effect of modified metal powder and modified spraying powder. Together with dry premixing, wet dispersion, and spray granulation processes, they solve the problems of uneven distribution of the reinforcing phase and poor powder flowability in traditional mechanical mixing methods.

Description

Technical Field

[0001] This invention relates to the field of composite material coating technology, specifically to a high-temperature sprayed iron-based composite material coating and its preparation method. Background Technology

[0002] Nuclear power plant steel storage tanks, as critical facilities for storing radioactive liquid media, have their outer walls constantly exposed to a marine atmosphere-salt spray coupled environment. Pressure vessel steels, represented by Q245R carbon steel, are widely used in the main structure of nuclear power plant storage tanks due to their excellent weldability and medium-temperature strength. However, in Cl... - Under the combined effects of infiltration (concentrations reaching 3.5%-5.0%), periodic wet-dry cycles, microbial adhesion, and irradiation, exposed Q245R substrates are prone to localized corrosion perforation, with annual corrosion rates exceeding 0.2 mm / a, seriously threatening the containment safety boundary throughout the entire life cycle of nuclear facilities. Therefore, developing efficient tank external wall reinforcement protection technologies is of great significance for ensuring the safe operation of nuclear power plants and extending equipment service life.

[0003] Surface spraying technology is an important method for improving and repairing metal substrates. Among them, cold spraying technology, due to its low-temperature characteristics, can effectively avoid problems such as oxidation and phase transformation during the spraying process, and has received widespread attention in the field of metal protection in recent years. Studies have shown that preparing iron-based alloy coatings on carbon steel surfaces can significantly improve the material's corrosion resistance. However, existing cold spraying technologies still have the following shortcomings: First, research on the preparation of iron-based powder material reinforcement layers is limited, with no mature reference examples and insufficient theoretical support for process development. Existing studies mostly focus on optimizing coating performance, but lack systematic analysis of the corrosion kinetics mechanisms of the substrate material in typical service environments. For example, key parameters such as the uniform / localized corrosion tendency, passivation film rupture threshold, and repassivation capability of Q245R alloy in 3.5% NaCl solution are still unclear, leading to a disconnect between coating design and substrate corrosion behavior.

[0004] Secondly, the bonding mechanism between the iron-based coating prepared by cold spraying and the substrate material is mainly mechanical, and the bonding strength is lower than that of thermal spraying or cladding techniques. Meanwhile, inherent micro-defects within the coating (such as pores and unmelted particles) can easily lead to contact fatigue failure during service. Studies have shown that pores in the coating not only reduce mechanical strength but also become channels for corrosive media penetration, accelerating substrate corrosion.

[0005] Third, existing spray powders have a single composition and lack synergistic design with multiple reinforcing phases. Traditional Q245R alloy powder has a low content of corrosion-resistant elements (Cr≤0.04%, Ni≤0.002%, Mo≤0.005%), making it difficult to form a stable passivation film in harsh environments. Although adding reinforcing phases such as tin bronze and molybdenum powder has some effect, it suffers from problems such as uneven distribution and weak interfacial bonding.

[0006] To address the aforementioned issues, existing technologies employ remelting to reduce micro-defects in the coating and improve the bonding strength between the coating and the substrate. Common remelting methods include laser remelting, argon arc remelting, electron beam remelting, and induction remelting. Among these, induction remelting utilizes the skin effect to concentrate heat on the coating surface, effectively reducing thermal damage to the substrate. Simultaneously, it transforms the mechanical bonding between the coating and the substrate into a metallurgical bonding, significantly improving the bonding strength. However, existing induction remelting process parameters have not been systematically optimized for iron-based cold-spray coatings, leading to problems such as oxide accumulation and high porosity on the coating surface after remelting.

[0007] In summary, developing a method for preparing iron-based composite material coatings that can simultaneously achieve high bonding strength, low porosity, and excellent corrosion resistance has become a pressing technical problem to be solved in this field. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a high-temperature sprayed iron-based composite material coating and its preparation method.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a high-temperature sprayed iron-based composite material coating includes the following preparation steps: S1. Grind the surface protrusions of the substrate using a grinding machine, clean and degrease with acetone, ultrasonically clean with anhydrous ethanol and dry, and then perform sandblasting with 100-mesh white corundum to achieve a surface roughness of Ra of 3-5μm to obtain the pretreated substrate. S2. Preheat the pretreated substrate obtained in step S1 at 120-140℃ for 3-5 minutes, and use a spraying equipment (GDU-3-15 low-pressure cold air power spraying equipment) to spray the modified spraying powder onto the surface of the substrate to obtain the sprayed substrate. S3. Cut the sprayed substrate obtained in step S2 into circular pieces with a diameter of 29-31mm, remelt the circular pieces using a remelting equipment (SPG-30B high-frequency induction remelting equipment), and cool them to room temperature to obtain a high-temperature sprayed iron-based composite material coating. The preparation of modified spray powder includes the following steps: S21. By weight, 100-110 parts of modified metal powder, 0.1-0.3 parts of few-layer graphene, 0.5-1.5 parts of nano-alumina and 0.5-1 parts of polyvinyl alcohol solution with a mass concentration of 0.5-1% are added to 190-210 parts of anhydrous ethanol, and wet ball milled in a planetary ball mill for 4-6 hours under argon protection to obtain a uniformly mixed slurry; S22. The uniformly mixed slurry obtained in step S21 is spray-granulated and dried, with the inlet temperature controlled at 180-200℃ and the outlet temperature at 80-90℃, to obtain spherical composite particles; S23. Place the spherical composite particles obtained in step S22 in a vacuum heat treatment furnace to remove the binder and pre-alloy them, then perform deep cryogenic cycling treatment, and finally obtain the modified spray powder after vacuum drying at 60-80℃ for 1-2 hours.

[0010] Preferably, the preparation of modified metal powder includes the following steps: S211. By weight, add 90-100 parts of Q245R alloy powder (particle size 20-53μm), 8-12 parts of tin bronze powder, 3-5 parts of molybdenum powder, 1-3 parts of titanium carbide, 0.2-0.5 parts of cerium oxide and 0.3-0.8 parts of stearic acid into a planetary ball mill, add zirconium oxide grinding balls at a ball-to-material ratio of 5:1, and dry ball mill at 200-250 rpm for 2-3 hours under argon protection to obtain a preliminary mixture; S212. Add 190-200 parts of anhydrous ethanol and 0.5-1 parts of a 0.5-1% polyvinyl alcohol solution to the preliminary mixture obtained in step S211. Wet ball mill at 200-250 rpm for 4-6 hours and then spray granulate and dry to obtain the secondary composite particles. S213. The secondary composite particles obtained in step S212 are placed in a vacuum heat treatment furnace to remove the organic dispersant and achieve pre-alloying. Then, they are subjected to deep cryogenic cycling treatment and vacuum drying at 60-80℃ for 1-2 hours to finally obtain modified metal powder.

[0011] Preferably, the spraying equipment has a spraying temperature of 400-550℃, 3-4 spraying passes, air as the carrier gas, a gas pressure of 0.6-0.8MPa, a spraying distance of 10-12mm, a nozzle moving speed of 8-10mm / s, a powder feeding rate of 24-26g / s, and a single spray thickness increase of 20-30μm / pass.

[0012] Preferably, the remelting heating temperature is 500-520℃, the heating power is 1.8-2.2KW, the frequency is 170-180kHz, the gap between the planar spool coil and the working part is 10mm, and the heating time is 8-12s.

[0013] Preferably, the vacuum degree of the vacuum heat treatment furnace in step S23 is ≤10. -2 Pa, heat treatment temperature is 350-400℃, heating rate is 4-6℃ / min, holding time is 1.5-2h; deep cryogenic cycle treatment temperature is -190℃, cooling rate is 5-10℃ / min, holding time is 30-40min, cycle number is 5-8 times.

[0014] Preferably, the base material is selected from Q245R carbon steel.

[0015] Preferably, the rotational speed of the planetary ball mill in step S21 is 200-250 rpm.

[0016] Preferably, the inlet temperature of the spray granulation drying in step S212 is 180-200℃ and the outlet temperature is 80-90℃.

[0017] Preferably, the vacuum degree of the vacuum heat treatment furnace in step S213 is ≤5×10⁻⁶. -2 Pa, heat treatment temperature is 380-420℃, heating rate is 5-8℃ / min, holding time is 1.5-2h; deep cryogenic cycle treatment temperature is -190℃, cooling rate is 5-10℃ / min, holding time is 30-40min, cycle number is 5-8 times.

[0018] A high-temperature sprayed iron-based composite material coating is prepared by the above-described preparation method.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention effectively improves the coating bonding strength, pitting resistance, and wear resistance through the synergistic effect of modified metal powder and modified spray powder. Together with dry premixing, wet dispersion, and spray granulation processes, these two methods solve the problems of uneven distribution of the reinforcing phase and poor powder flowability in traditional mechanical mixing methods, laying the foundation for the stable implementation of subsequent cold spraying processes.

[0020] 2. This invention provides an innovative technical path for improving coating quality by organically combining cryogenic treatment and cold spraying processes. The coating quality is optimal when sprayed within a set high-temperature range, with minimal thermal impact on the substrate material. The preparation method of this invention is stable and highly controllable, and can be used for surface protection and repair of critical equipment such as nuclear power plant storage tanks, pressure vessels, and offshore platforms, showing broad application prospects. Attached Figure Description

[0021] Figure 1 This is a process flow diagram for preparing the high-temperature sprayed iron-based composite material coating of the present invention; Figure 2 This is a flow chart of the preparation process of the modified spray powder of the present invention; Figure 3 This is a flow chart of the preparation process of the modified metal powder of the present invention; Figure 4 This is a particle size distribution diagram of the modified metal powder obtained in Example 1 of the present invention; Figure 5 This is a light mirror image of the substrate material surface after induction remelting of the high-temperature sprayed iron-based composite material coating obtained in Example 1 of the present invention. Detailed Implementation

[0022] The present invention will now be clearly and completely described in conjunction with embodiments thereof. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] Please see Figure 1-5 The present invention provides a technical solution: Example 1 A method for preparing a high-temperature sprayed iron-based composite material coating: Before preparing the high-temperature sprayed iron-based composite material coating, modified metal powder and modified spraying powder are first prepared: The preparation of modified metal powder includes the following steps: S211. Add 90g of Q245R alloy powder, 8g of tin bronze powder, 3g of molybdenum powder, 1g of titanium carbide, 0.2g of cerium oxide and 0.3g of stearic acid to a planetary ball mill, add zirconium oxide grinding balls at a ball-to-material ratio of 5:1, and dry ball mill at 200 rpm for 2 hours under argon protection to obtain a preliminary mixture. S212. Add 190g of anhydrous ethanol and 0.5g of 0.5% polyvinyl alcohol solution to the preliminary mixture obtained in step S211. After wet ball milling at 200rpm for 4h, spray granulation and drying are carried out, with the inlet temperature controlled at 180℃ and the outlet temperature at 80℃, to obtain the secondary composite particles. S213. The secondary composite particles obtained in step S212 are placed in a vacuum heat treatment furnace to remove the organic dispersant and achieve pre-alloying. Then, they undergo deep cryogenic cycling treatment and are finally dried under vacuum at 60°C for 1 hour to obtain the modified metal powder. The vacuum degree of the vacuum heat treatment furnace is 5 × 10⁻⁶. -2 Pa, heat treatment temperature is 380℃, heating rate is 5℃ / min, holding time is 1.5h; cryogenic cycle treatment temperature is -190℃, cooling rate is 5℃ / min, holding time is 30min, cycle number is 5 times.

[0024] The preparation of modified spray powder includes the following steps: S21. Add 100g of modified metal powder, 0.1g of few-layer graphene, 0.5g of nano-alumina and 0.5g of polyvinyl alcohol solution with a mass concentration of 0.5% to 190g of anhydrous ethanol, and place them in a planetary ball mill under argon protection and wet ball mill at 200rpm for 4h to obtain a uniformly mixed slurry. S22. The uniformly mixed slurry obtained in step S21 is spray-granulated and dried, with the inlet temperature controlled at 180℃ and the outlet temperature at 80℃, to obtain spherical composite particles; S23. The spherical composite particles obtained in step S22 are placed in a vacuum heat treatment furnace to remove the binder and pre-alloy them, followed by deep cryogenic cycling treatment and vacuum drying at 60°C for 1 hour to finally obtain the modified spray powder. The vacuum degree of the vacuum heat treatment furnace is 10. -2 Pa, heat treatment temperature is 350℃, heating rate is 4℃ / min, holding time is 1.5h; cryogenic cycle treatment temperature is -190℃, cooling rate is 5℃ / min, holding time is 30min, cycle number is 5 times.

[0025] S1. Grind the surface of the substrate (Q245R carbon steel) with a grinding machine to smooth the surface protrusions, clean it with acetone to remove oil, then clean it with anhydrous ethanol using ultrasonic cleaning and dry it. Then, use 100-mesh white corundum for sandblasting to obtain the pretreated substrate. S2. The pretreated substrate obtained in step S1 is preheated at 120°C for 3 minutes. The modified powder is then sprayed onto the surface of the substrate using a spraying device (GDU-3-15 low-pressure cold air power spraying device) to obtain the sprayed substrate. The spraying temperature of the spraying device is 400°C, the number of spraying passes is 3, the carrier gas is air, the gas pressure is 0.6MPa, the spraying distance is 10mm, the nozzle moving speed is 8mm / s, the powder feeding rate is 24g / s, and the thickness increase per spraying pass is 20μm / pass. S3. Cut the sprayed substrate obtained in step S2 into circular pieces with a diameter of 29mm. Remelt the circular pieces using a remelting device (SPG-30B high-frequency induction remelting device). After cooling to room temperature, a high-temperature sprayed iron-based composite material coating is obtained. The remelting heating temperature is 500℃, the heating power is 1.8KW, the frequency is 170kHz, the gap between the planar spool coil and the working part is 10mm, and the heating time is 8s.

[0026] Example 2 A method for preparing a high-temperature sprayed iron-based composite material coating: Before preparing the high-temperature sprayed iron-based composite material coating, modified metal powder and modified spraying powder are first prepared: The preparation of modified metal powder includes the following steps: S211. Add 100g of Q245R alloy powder, 12g of tin bronze powder, 5g of molybdenum powder, 3g of titanium carbide, 0.5g of cerium oxide and 0.8g of stearic acid to a planetary ball mill, add zirconium oxide grinding balls at a ball-to-material ratio of 5:1, and dry ball mill at 250rpm for 3h under argon protection to obtain a preliminary mixture; S212. Add 200g of anhydrous ethanol and 1g of 1% polyvinyl alcohol solution to the preliminary mixture obtained in step S211. After wet ball milling at 250rpm for 6h, spray granulation and drying are carried out, with the inlet temperature controlled at 200℃ and the outlet temperature at 90℃, to obtain the secondary composite particles. S213. The secondary composite particles obtained in step S212 are placed in a vacuum heat treatment furnace to remove the organic dispersant and achieve pre-alloying. Then, they undergo deep cryogenic cycling treatment and are finally dried under vacuum at 80°C for 2 hours to obtain the modified metal powder. The vacuum degree of the vacuum heat treatment furnace is 4 × 10⁻⁶. -2 Pa, the heat treatment temperature is 420℃, the heating rate is 8℃ / min, and the holding time is 2h; the cryogenic cycle treatment temperature is -190℃, the cooling rate is 10℃ / min, the holding time is 40min, and the number of cycles is 8.

[0027] The preparation of modified spray powder includes the following steps: S21. Add 110g of modified metal powder, 0.3g of few-layer graphene, 1.5g of nano-alumina and 1g of 1% polyvinyl alcohol solution to 210g of anhydrous ethanol, and place in a planetary ball mill under argon protection and wet ball mill at 250rpm for 6h to obtain a uniformly mixed slurry. S22. The uniformly mixed slurry obtained in step S21 is spray-granulated and dried, with the inlet temperature controlled at 200℃ and the outlet temperature at 90℃, to obtain spherical composite particles. S23. The spherical composite particles obtained in step S22 are placed in a vacuum heat treatment furnace to remove the binder and pre-alloy them, followed by deep cryogenic cycling treatment and vacuum drying at 80°C for 2 hours to finally obtain the modified spray powder. The vacuum degree of the vacuum heat treatment furnace is 8×10⁻⁶. -3 Pa, heat treatment temperature is 400℃, heating rate is 6℃ / min, holding time is 2h; deep cryogenic cycle treatment temperature is -190℃, cooling rate is 10℃ / min, holding time is 40min, cycle number is 8.

[0028] S1. Grind the surface of the substrate (Q245R carbon steel) with a grinding machine to smooth the surface protrusions, clean it with acetone to remove oil, then clean it with anhydrous ethanol using ultrasonic cleaning and dry it. Then, use 100-mesh white corundum for sandblasting to obtain the pretreated substrate. S2. The pretreated substrate obtained in step S1 is preheated at 140℃ for 5 minutes. The modified spray powder is then sprayed onto the surface of the substrate using a spraying device (GDU-3-15 low-pressure cold air power spraying device) to obtain the sprayed substrate. The spraying temperature of the spraying device is 550℃, the number of spray passes is 4, the carrier gas is air, the gas pressure is 0.8MPa, the spraying distance is 12mm, the nozzle moving speed is 10mm / s, the powder feeding rate is 26g / s, and the thickness increase per spray pass is 30μm / pass. S3. Cut the sprayed substrate obtained in step S2 into circular pieces with a diameter of 31mm. Remelt the circular pieces using a remelting device (SPG-30B high-frequency induction remelting device). After cooling to room temperature, a high-temperature sprayed iron-based composite material coating is obtained. The remelting heating temperature is 520℃, the heating power is 2.2KW, the frequency is 180kHz, the gap between the planar spool coil and the working part is 10mm, and the heating time is 12s.

[0029] Example 3 A method for preparing a high-temperature sprayed iron-based composite material coating: Before preparing the high-temperature sprayed iron-based composite material coating, modified metal powder and modified spraying powder are first prepared: The preparation of modified metal powder includes the following steps: S211. Add 95g of Q245R alloy powder, 10g of tin bronze powder, 4g of molybdenum powder, 2g of titanium carbide, 0.3g of cerium oxide and 0.5g of stearic acid to a planetary ball mill, add zirconium oxide grinding balls at a ball-to-material ratio of 5:1, and dry ball mill at 220 rpm for 2.5h under argon protection to obtain a preliminary mixture; S212. Add 195g of anhydrous ethanol and 0.8g of 0.7% polyvinyl alcohol solution to the preliminary mixture obtained in step S211. After wet ball milling at 220rpm for 5h, spray granulation and drying are carried out, with the inlet temperature controlled at 190℃ and the outlet temperature at 85℃, to obtain the secondary composite particles. S213. The secondary composite particles obtained in step S212 are placed in a vacuum heat treatment furnace to remove the organic dispersant and achieve pre-alloying. Then, they undergo deep cryogenic cycling treatment and are finally dried under vacuum at 70°C for 1.5 hours to obtain the modified metal powder. The vacuum degree of the vacuum heat treatment furnace is 3 × 10⁻⁶. -2 Pa, heat treatment temperature is 400℃, heating rate is 7℃ / min, holding time is 1.6h; deep cryogenic cycle treatment temperature is -190℃, cooling rate is 7℃ / min, holding time is 35min, cycle number is 6.

[0030] The preparation of modified spray powder includes the following steps: S21. Add 105g of modified metal powder, 0.2g of few-layer graphene, 1g of nano-alumina and 0.8g of polyvinyl alcohol solution with a mass concentration of 0.8% to 200g of anhydrous ethanol, and place in a planetary ball mill under argon protection and wet ball mill at 220rpm for 5h to obtain a uniformly mixed slurry. S22. The uniformly mixed slurry obtained in step S21 is spray-granulated and dried, with the inlet temperature controlled at 190℃ and the outlet temperature at 85℃, to obtain spherical composite particles. S23. The spherical composite particles obtained in step S22 are placed in a vacuum heat treatment furnace to remove the binder and pre-alloy them, followed by deep cryogenic cycling treatment and vacuum drying at 70°C for 1.5 hours to finally obtain the modified spray powder. The vacuum degree of the vacuum heat treatment furnace is 5×10⁻⁶. -3 Pa, heat treatment temperature is 380℃, heating rate is 5℃ / min, holding time is 1.6h; deep cryogenic cycle treatment temperature is -190℃, cooling rate is 8℃ / min, holding time is 35min, cycle number is 7.

[0031] S1. Grind the surface of the substrate (Q245R carbon steel) with a grinding machine to smooth the surface protrusions, clean it with acetone to remove oil, then clean it with anhydrous ethanol using ultrasonic cleaning and dry it. Then, use 100-mesh white corundum for sandblasting to obtain the pretreated substrate. S2. The pretreated substrate obtained in step S1 is preheated at 130°C for 4 minutes. The modified powder is then sprayed onto the surface of the substrate using a spraying device (GDU-3-15 low-pressure cold air power spraying device) to obtain the sprayed substrate. The spraying temperature of the spraying device is 480°C, the number of spraying passes is 4, the carrier gas is air, the gas pressure is 0.7MPa, the spraying distance is 11mm, the nozzle moving speed is 9mm / s, the powder feeding rate is 25g / s, and the thickness increase per spraying pass is 25μm / pass. S3. Cut the sprayed substrate obtained in step S2 into circular pieces with a diameter of 30mm. Remelt the circular pieces using a remelting device (SPG-30B high-frequency induction remelting device). After cooling to room temperature, a high-temperature sprayed iron-based composite material coating is obtained. The remelting heating temperature is 510℃, the heating power is 20KW, the frequency is 175kHz, the gap between the planar spool coil and the working part is 10mm, and the heating time is 10s.

[0032] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the modified metal powder is replaced with Q245R alloy powder in this comparative example. The other steps are exactly the same in Comparative Example 1 and Example 1.

[0033] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the modified spray powder is replaced with Q245R alloy powder and tin bronze powder in a mass ratio of 10:1. The remaining steps are exactly the same in Comparative Example 2 and Example 1.

[0034] Performance testing: This invention studies the particle size distribution of modified metal powders, and includes... Figure 4 This is a particle size distribution diagram of the modified metal powder obtained in Example 1 of the present invention. As can be seen from the figure, the average particle size of the powder is 37.61112 μm, and the distribution range is 60-110 μm, which conforms to a normal distribution. Dv(10), Dv(50) and Dv(90) represent the particle sizes corresponding to the cumulative particle size distribution reaching 10%, 50% and 90%, respectively.

[0035] This invention studies the effect of induction remelting on the matrix material. To investigate this effect, the surface of the induction-remelted sample was polished. Figure 5 The image shows a light microscopic view of the substrate material surface after induction remelting of the high-temperature sprayed iron-based composite material coating obtained in Example 1. It clearly reveals the coating's microstructure, density, and forming quality. The coating surface is generally smooth and flat, free from defects common in cold spraying, such as pores, unmelted particles, cracks, and inclusions. Laser remelting effectively eliminates the loose internal structure of the cold-sprayed coating, achieving coating densification. The surface structure is uniform and continuous, without obvious component segregation or local unevenness. The remelted area and the cold-sprayed underlayer have a natural transition with no interface gaps. After chemical plating, liquid-phase modification, and laser remelting, the powder surface... A continuous and dense passivation film substrate is formed on the surface, with regular grain arrangement and no obvious pores or microcracks. It can effectively block the intrusion path of corrosive media. No unmelted powder agglomeration, spray overlap marks, or remelting heat damage marks are observed under light microscopy, indicating that the cold spraying parameters and laser remelting parameters are reasonably matched and the coating forming quality is excellent. This microscopic surface feature directly supports the high density, high bonding strength, and high corrosion resistance of the coating, providing microstructural guarantee for its long-term protection under harsh working conditions such as nuclear power storage tanks. It also confirms the effectiveness of element compounding, powder modification, and composite processes in optimizing the micromorphology of the coating.

[0036] The bond strength of the high-temperature sprayed iron-based composite coatings obtained in Examples 1-3 and Comparative Examples 1-2 was tested according to ASTM C633, "Standard Tests for Adhesion or Cohesive Strength of Thermally Sprayed Coatings". The high-temperature sprayed iron-based composite coatings obtained in Examples 1-3 and Comparative Examples 1-2 were bonded to their mating parts with adhesive, mounted on a tensile testing machine, and stretched at a tensile speed of 1 mm / min. The maximum tensile force at which the coating detached was recorded. The bond strength (MPa) σ = F / A, where F is the maximum tensile force (N) and A is the coating area (mm²). 2 ).

[0037] A 3.5% sodium chloride solution was prepared to simulate a marine environment for testing the pitting corrosion resistance of the high-temperature sprayed iron-based composite coatings obtained in Examples 1-3 and Comparative Examples 1-2. A saturated calomel electrode (SCE) was used as the reference electrode, and a platinum electrode as the auxiliary electrode. The scan rate was 0.5 mV / s, and the test range was -0.5 V to +1.5 V. The pitting sites (E0) where the test current increased sharply were measured. pit ).

[0038] The wear resistance of the high-temperature sprayed iron-based composite coatings obtained in Examples 1-3 and Comparative Examples 1-2 was tested according to ASTM G99 "Pin-Disc Friction and Wear Test". The grinding material was a GCr15 steel ball (6 mm in diameter), the load was 10 N, the sliding speed was 0.1 m / s, and the sliding distance was 500 m. The coefficient of friction and wear volume were obtained, and the wear rate was finally calculated as: Wear rate = Wear volume / Coefficient of friction. The final data are shown in Table 1 below. Table 1 Performance Test Results As shown in Table 1, the high-temperature sprayed iron-based composite material coating obtained in the example is superior to the comparative example in terms of bonding strength, pitting corrosion resistance, and wear resistance. This demonstrates that the synergistic effect of the modified metal powder and the modified spraying powder improves the interfacial activity and bonding performance of the powder, and enhances the passivation ability and Cl-resistance of the coating. - The improved penetration enhances corrosion resistance and reduces friction and wear, validating the effectiveness of the synergistic design of modified metal powder and modified spray powder, spray granulation process, and cryogenic cycle treatment. This coating technology has broad application prospects in harsh environments such as nuclear power plant storage tanks.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-temperature sprayed iron-based composite material coating, characterized in that, The preparation steps include the following: S1. Grind the surface of the substrate to smooth out the protrusions using a grinding machine, clean it with acetone to remove oil, then ultrasonically clean it with anhydrous ethanol and dry it. Then, sandblast it with 100-mesh white corundum to obtain the pretreated substrate. S2. Preheat the pretreated substrate obtained in step S1 at 120-140℃ for 3-5 minutes, and use a spraying equipment to spray the modified spraying powder onto the surface of the substrate to obtain the sprayed substrate. S3. Cut the sprayed substrate obtained in step S2 into circular pieces with a diameter of 29-31mm, remelt the circular pieces using a remelting equipment, and cool them to room temperature to obtain a high-temperature sprayed iron-based composite material coating. The preparation of the modified spray powder includes the following steps: S21. By weight, 100-110 parts of modified metal powder, 0.1-0.3 parts of few-layer graphene, 0.5-1.5 parts of nano-alumina and 0.5-1 parts of polyvinyl alcohol solution with a mass concentration of 0.5-1% are added to 190-210 parts of anhydrous ethanol, and wet ball milled in a planetary ball mill for 4-6 hours under argon protection to obtain a uniformly mixed slurry; S22. The uniformly mixed slurry obtained in step S21 is spray-granulated and dried, with the inlet temperature controlled at 180-200℃ and the outlet temperature at 80-90℃, to obtain spherical composite particles; S23. Place the spherical composite particles obtained in step S22 in a vacuum heat treatment furnace to remove the binder and pre-alloy them, then perform deep cryogenic cycling treatment, and finally obtain the modified spray powder after vacuum drying at 60-80℃ for 1-2 hours.

2. The method for preparing a high-temperature sprayed iron-based composite material coating according to claim 1, characterized in that, The preparation of the modified metal powder includes the following steps: S211. By weight, add 90-100 parts of Q245R alloy powder, 8-12 parts of tin bronze powder, 3-5 parts of molybdenum powder, 1-3 parts of titanium carbide, 0.2-0.5 parts of cerium oxide and 0.3-0.8 parts of stearic acid into a planetary ball mill, add zirconium oxide grinding balls at a ball-to-material ratio of 5:1, and dry ball mill at 200-250 rpm for 2-3 hours under argon protection to obtain a preliminary mixture; S212. Add 190-200 parts of anhydrous ethanol and 0.5-1 parts of a 0.5-1% polyvinyl alcohol solution to the preliminary mixture obtained in step S211. Wet ball mill at 200-250 rpm for 4-6 hours and then spray granulate and dry to obtain the secondary composite particles. S213. The secondary composite particles obtained in step S212 are placed in a vacuum heat treatment furnace to remove the organic dispersant and achieve pre-alloying. Then, they are subjected to deep cryogenic cycling treatment and vacuum drying at 60-80℃ for 1-2 hours to finally obtain modified metal powder.

3. The method for preparing a high-temperature sprayed iron-based composite material coating according to claim 1, characterized in that, The spraying equipment has a spraying temperature of 400-550℃, 3-4 spraying passes, air as the carrier gas, a gas pressure of 0.6-0.8MPa, a spraying distance of 10-12mm, a nozzle moving speed of 8-10mm / s, a powder feeding rate of 24-26g / s, and a single spray thickness increase of 20-30μm / pass.

4. The method for preparing a high-temperature sprayed iron-based composite material coating according to claim 1, characterized in that, The remelting heating temperature is 500-520℃, the heating power is 1.8-2.2KW, the frequency is 170-180kHz, the gap between the planar spool coil and the working part is 10mm, and the heating time is 8-12s.

5. The method for preparing a high-temperature sprayed iron-based composite material coating according to claim 1, characterized in that, The vacuum degree of the vacuum heat treatment furnace in step S23 is ≤10. -2 Pa, heat treatment temperature is 350-400℃, heating rate is 4-6℃ / min, holding time is 1.5-2h; deep cryogenic cycle treatment temperature is -190℃, cooling rate is 5-10℃ / min, holding time is 30-40min, cycle number is 5-8 times.

6. The method for preparing a high-temperature sprayed iron-based composite material coating according to claim 1, characterized in that, The substrate is selected from Q245R carbon steel.

7. The method for preparing a high-temperature sprayed iron-based composite material coating according to claim 1, characterized in that, In step S21, the rotational speed of the planetary ball mill is 200-250 rpm.

8. The method for preparing a high-temperature sprayed iron-based composite material coating according to claim 2, characterized in that, In step S212, the inlet temperature of the spray granulation dryer is 180-200℃, and the outlet temperature is 80-90℃.

9. The method for preparing a high-temperature sprayed iron-based composite material coating according to claim 2, characterized in that, The vacuum degree of the vacuum heat treatment furnace in step S213 is ≤5×10 -2 Pa, heat treatment temperature is 380-420℃, heating rate is 5-8℃ / min, holding time is 1.5-2h; deep cryogenic cycle treatment temperature is -190℃, cooling rate is 5-10℃ / min, holding time is 30-40min, cycle number is 5-8 times.

10. A high-temperature sprayed iron-based composite material coating, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

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