Liquid lead bismuth erosion resistant composite coating and preparation method and application thereof

Abstract

The application discloses a liquid lead and bismuth erosion corrosion resistant composite coating and a preparation method and application thereof, and relates to the technical field of surface protection. The method comprises the following steps: spraying a FeCrAlY coating on the surface of a substrate, performing remelting treatment and light finishing treatment on the FeCrAlY coating, and pre-oxidizing the coating. The FeCrAlY coating is sprayed on the surface of the substrate, and then the FeCrAlY coating is subjected to remelting treatment, so that the interlayer interface between the particles in the FeCrAlY coating disappears, and the effect of hole sealing is achieved. The light finishing treatment can polish the coating on the surface of the substrate to be flat. When the liquid lead and bismuth eutectic alloy flows, circulates and cools, the erosion corrosion effect of the liquid lead and bismuth eutectic alloy on the coating is reduced, and the service life of the coating is prolonged. Finally, the pre-oxidation treatment is performed on the surface of the coating, a continuous and dense thermal growth oxide layer is generated in situ on the surface of the coating, the wettability of the liquid lead and bismuth alloy is effectively reduced, and the long-time service stability is improved.

Description

Technical Field

[0001] The present invention relates to the field of surface protection technology, and in particular to a liquid lead-bismuth erosion corrosion resistant composite coating and a preparation method and application thereof. Background Art

[0002] Lead-cooled fast neutron reactors (LFRs) offer unique advantages in nuclear fuel proliferation and nuclear waste disposal, and are expected to become the first advanced fourth-generation nuclear energy system to achieve engineering demonstration and commercial application. Liquid lead-bismuth eutectic alloy (LBE) has become the preferred coolant material for LFRs due to its excellent neutron economy, superior radiation resistance, heat transfer properties, and chemical inertness. The circulating pump, a Class I nuclear equipment, is the driving component of the LFR's cooling loop. Its primary function is to circulate the liquid heavy metal coolant within the primary loop at a constant flow rate during reactor startup and normal operation, promptly removing heat generated within the core and ensuring proper operation. In the event of an accident, the circulating pump relies on its own inertia to maintain a constant coolant flow rate within the primary loop from emergency shutdown to the completion of the reactor's residual heat removal system, preventing overheating in the core from leading to a meltdown. Key components of the circulating pump, such as the piping, storage tank, and main pump impeller and blades, are fully exposed to the liquid lead-bismuth eutectic alloy. Liquid lead-bismuth eutectic alloy is highly corrosive in high-temperature environments. When it comes into direct contact with structural materials, it will cause serious corrosion damage to components through a series of chemical and physical processes such as dissolution corrosion, coupled oxidation of dissolved oxygen, and erosion erosion. The chemical composition, microstructure and mechanical properties of structural components will undergo significant changes or degradation, which may endanger the safety and service life of the reactor in severe cases.

[0003] To improve the service life and operational reliability of circulating pump blades, the most effective methods are to modify and strengthen the blade surface or to apply a coating of a material resistant to liquid lead-bismuth erosion corrosion to the surface for protection. One approach involves directly placing the component in a liquid lead-bismuth eutectic alloy with an oxygen concentration controlled within an appropriate range to form an oxide film on its surface. However, practice has shown that the resulting oxide film is often relatively loose, and in actual operating conditions, in the flowing liquid lead-bismuth eutectic alloy, insoluble floating debris easily forms on the surface of the heavier liquid lead-bismuth eutectic alloy. Furthermore, if large amounts of Ni and Mo elements on the surface of the component dissolve into the liquid lead-bismuth eutectic alloy, resulting in the incorporation of impurities, this can further complicate subsequent waste disposal. Therefore, in addition to controlling the oxygen concentration in the coolant to form a dense oxide film on the component surface, developing anti-corrosion coating technology is also an important research direction for addressing the corrosion problem of liquid lead-bismuth eutectic coolants.

[0004] Currently, one method used to reduce the dissolution of Ni and Mo elements into liquid lead-bismuth eutectic alloys is to deposit a layer of corrosion-resistant material on the substrate surface using a non-melting inert gas tungsten arc welding (TIG welding). However, corrosion testing of the liquid lead-bismuth eutectic alloy has revealed that oxidative corrosion and element dissolution still occur on the surface of the deposited layer, and a double oxide layer with a loose outer layer and a dense inner layer forms on the surface. Cr-N coatings deposited on the substrate surface by cathodic arc ion plating exhibit good corrosion resistance in LBE at 450°C. However, when the temperature of the liquid lead-bismuth eutectic alloy rises to 550°C, the coating is severely damaged due to the difference in thermal expansion coefficients between the coating and the substrate, resulting in cracks and flaking, which in turn causes the substrate to be dissolved and corroded by the liquid lead-bismuth eutectic alloy. Therefore, it is urgent to develop a coating preparation technology that is resistant to liquid lead-bismuth erosion corrosion.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a liquid lead-bismuth erosion corrosion resistant composite coating and a preparation method and application thereof.

[0007] The present invention is achieved in that:

[0008] In a first aspect, the present invention provides a method for preparing a composite coating resistant to liquid lead-bismuth erosion corrosion, comprising spraying a FeCrAlY coating on a substrate surface, remelting and polishing the FeCrAlY coating, and then pre-oxidizing the coating.

[0009] In an optional embodiment, the remelting process includes any one of laser remelting and pulsed electron beam processing.

[0010] Preferably, the remelting process is laser remelting. Preferably, the laser remelting conditions include: a spot diameter of 3 to 5 mm, an overlap of 1 to 2.5 mm, a laser power of 250 to 650 W, and a moving speed of 10 to 20 mm / s.

[0011] In an optional embodiment, the spraying method of the FeCrAlY coating includes any one of low-pressure plasma spraying, atmospheric plasma spraying and supersonic velocity oxygen fuel spraying.

[0012] Preferably, the FeCrAlY coating is sprayed by low-pressure plasma spraying. Preferably, the conditions for low-pressure plasma spraying include: in an Ar protective atmosphere spray chamber at a pressure of 3.0 to 15.0 kPa, a plasma spray gun current of 600 to 850 A, an argon flow rate of 50 to 70 L / min, a hydrogen flow rate of 4 to 12 L / min, a helium flow rate of 0 to 10 L / min, a spray distance of 200 to 400 mm, and a powder feed rate of 5 to 20 g / min, to prepare a FeCrAlY coating with a thickness of 40 to 200 μm.

[0013] In an optional embodiment, the finishing process includes polishing the coating.

[0014] In an optional embodiment, the abrasive includes at least one of brown corundum, high-alumina porcelain, white corundum, zirconium beads, and high-frequency porcelain.

[0015] In an optional embodiment, the polishing frequency is 30 to 60 Hz, and the polishing time is 20 to 60 minutes.

[0016] In an optional embodiment, the pre-oxidation includes heating the substrate to 800-1000° C. by using a plasma jet in a chamber at a pressure of 50-500 Pa, introducing an oxygen flow rate of 1-4 L / min, and holding the substrate for 5-25 minutes.

[0017] In an optional embodiment, the substrate is further pretreated before spraying the FeCrAlY coating, and the pretreatment includes degreasing, sandblasting, transferred arc cleaning, and preheating the substrate in sequence.

[0018] Preferably, the preheating includes preheating the substrate using a plasma jet technology, and the preheating temperature is 600-1000°C.

[0019] In a second aspect, the present invention provides a composite coating resistant to liquid lead-bismuth erosion corrosion, which is prepared by the preparation method according to any one of the aforementioned embodiments.

[0020] In a third aspect, the present invention provides an application of the preparation method according to any one of the aforementioned embodiments in a nuclear energy system.

[0021] The present invention has the following beneficial effects:

[0022] The present invention provides a composite coating resistant to liquid lead-bismuth erosion and corrosion, as well as its preparation method and application. By spraying an FeCrAlY coating on the surface of a substrate, the substrate can be protected from corrosion by the liquid lead-bismuth eutectic alloy. The FeCrAlY coating is then remelted to eliminate the interlayer interfaces between particles within the coating, achieving a pore-sealing effect. A polishing treatment can smooth the coating on the substrate surface, improving its finish. When the liquid lead-bismuth eutectic alloy circulates and cools, its erosion effect on the coating surface is reduced, thereby increasing the coating's service life. Finally, the coating is pre-oxidized to generate a continuous and dense thermally grown oxide layer in situ on the coating surface, effectively reducing wettability with the liquid lead-bismuth alloy and improving long-term service stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is a scanning electron microscope image of the cross section of the liquid lead-bismuth erosion corrosion resistant composite coating provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0026] In a first aspect, the present invention provides a method for preparing a composite coating resistant to liquid lead-bismuth erosion corrosion, comprising spraying a FeCrAlY coating on a substrate surface, remelting and polishing the FeCrAlY coating, and then pre-oxidizing the coating.

[0027] In an optional embodiment, the substrate is pretreated before the FeCrAlY coating is sprayed. The pretreatment includes sequentially degreasing, sandblasting, transferring arc cleaning, and preheating. The degreasing, sandblasting, cleaning, and preheating steps are conventional techniques in the art, and the present invention does not limit the specific processing parameters. The substrate preheating temperature can be maintained between 600°C and 1000°C. Plasma jet technology can be used for preheating the substrate.

[0028] In an optional embodiment, the spraying method of the FeCrAlY coating includes any one of low-pressure plasma spraying, atmospheric plasma spraying and supersonic velocity oxygen fuel spraying.

[0029] Preferably, the FeCrAlY coating is sprayed by low-pressure plasma spraying. Preferably, the conditions for low-pressure plasma spraying include: in an Ar protective atmosphere spray chamber at a pressure of 3.0 to 15.0 kPa, a plasma spray gun current of 600 to 850 A, an argon flow rate of 50 to 70 L / min, a hydrogen flow rate of 4 to 12 L / min, a helium flow rate of 0 to 10 L / min, a spray distance of 200 to 400 mm, and a powder feed rate of 5 to 20 g / min, to prepare a FeCrAlY coating with a thickness of 40 to 200 μm.

[0030] During the spraying process, the deposition of individual powder particles serves as the basic building block of the coating. Their deposition on the substrate surface and the subsequent stacking process directly affect the microstructural construction of the coating. When the substrate temperature increases, the substrate surface morphology changes at the micro-nano scale. At the same time, the adsorbate on the substrate surface desorbs, resulting in more complete direct contact between the molten powder particles and the substrate. The heat conduction and wettability between the molten droplets and the substrate are improved, and the cooling rate of the powder particles decreases, allowing them to remain in the molten state for a relatively longer time and form a better bond with the substrate. On the other hand, although the change in the atmospheric pressure in the spray chamber will not lead to a significant change in the substrate surface morphology, it will cause changes in the plasma jet characteristics and the temperature and velocity of the powder particles fed into the jet. It will also change the state of the physical adsorption layer on the substrate surface and inhibit the formation of an oxide film on the surface of the molten powder particles. Under the coupling of substrate temperature and ambient pressure, the properties of the substrate and molten powder particles change significantly at the same time. The wettability of the molten powder particles at the moment of collision with the substrate or the deposited coating and the heat conduction during the subsequent spreading and solidification process will be affected, which will affect the deposition morphology of individual powder particles, ultimately promoting the improvement of coating density. Oxidation during the spraying process can also be effectively controlled.

[0031] Thermal spray coating is formed by the rapid spreading of molten or semi-molten powder particles after impacting the substrate or the surface of the deposited coating, and then the rapid quenching and solidification of the flattened particles to form a layer-by-layer stack. The spreading and solidification of a single molten particle is usually completed within tens of microseconds, and the molten droplet is not sufficient to fully wet the substrate and completely fill the gap between the deposited particles to form micropores in the coating, resulting in the coating having a much lower bonding strength and cohesive strength, corrosion resistance and oxidation resistance than the bulk material of the same composition. The flowing liquid lead-bismuth eutectic alloy will produce high-speed relative movement on the surface of the coating, and the coating surface will be continuously eroded and damaged. The liquid lead-bismuth eutectic alloy penetrates and diffuses along the interfacial gap between the particles, pores and defects in the coating, and forms intermetallic compounds with the metal elements in the coating. The composition and structure of the coating and the blade are significantly different, and the composition and structure of the coating and the interface will inevitably evolve during long-term service, which will affect the service life of the related components and even endanger the service safety of the entire reactor. Therefore, the density of the coating must be further improved to reduce the penetration of the liquid lead-bismuth eutectic alloy into the internal channels of the coating.

[0032] In optional embodiments, the remelting treatment includes any one of laser remelting and pulsed electron beam treatment.

[0033] Preferably, the remelting treatment includes laser remelting. Preferably, the conditions of the laser remelting include a spot diameter of 3-5 mm, an overlap of 1-2.5 mm, a laser power of 250-650 W, and a moving speed of 10-20 mm / s.

[0034] As an important method for surface melting and strengthening of materials, laser remelting technology can utilize a high-energy-density laser beam to rapidly scan a pre-prepared thermal spray coating, the surface of the coating absorbs the laser energy to increase the temperature and rapidly melt, and after the laser beam leaves, the melted coating rapidly solidifies to form a remelted layer on the surface with metallurgical bonding. During the remelting process, the interfacial gap between the particle layers in the coating disappears, thereby having a good sealing effect. By controlling the remelting parameters, the remelting depth can be effectively controlled, the thermal influence on the substrate during the remelting process can be reduced, and the composition of the coating can not be changed. During the laser melting process, impurities and gases can also be removed, and the microstructure obtained by rapid cooling and recrystallization has high hardness, wear resistance and corrosion resistance.

[0035] After the low-pressure plasma sprayed FeCrAlY coating is treated by laser remelting, the density of the coating is significantly improved, but the coating surface still inevitably has some surface unevenness, burrs, burrs and oxide skin. In the circulating pump of the lead-cooled fast reactor loop cooling system, the flowing liquid lead-bismuth eutectic alloy will produce high-speed relative movement on the surface of the coating, so that the coating surface will be continuously eroded and damaged. In order to reduce the influence of the coating on the flow characteristics of the liquid lead-bismuth eutectic alloy in the circulating pump and the erosion of the liquid lead-bismuth eutectic alloy on the coating surface when flowing, the coating should have high smoothness.

[0036] In an optional embodiment, the finishing process includes polishing the coating.

[0037] A finishing machine is used to perform finishing treatment on the laser remelted coating to further improve the surface condition of the coating. The friction of the abrasive and the lubricating effect of the abrasive adsorbed on the abrasive surface are used to grind and polish the remelted coating, thereby reducing the unevenness of the coating surface, removing burrs, burrs and oxide scale that may be generated under high temperature, and improving the parallelism and smoothness of the coating. The finished product will not be deformed after processing and will not affect the accuracy. It can effectively reduce the scouring effect of flowing liquid lead and bismuth on the coating surface.

[0038] In an optional embodiment, the abrasive includes at least one of brown corundum, high-aluminum porcelain, white corundum, zirconium beads, and high-frequency porcelain. The size of the abrasive may be uneven, and the shape may be triangular, spherical, cylindrical, or quadrilateral, etc. The strong grinding ability of the abrasive is used to remove burrs on the workpiece. When there are higher requirements for smoothness, it can also be divided into two stages of polishing: rough polishing and medium polishing. When rough polishing, a slightly larger abrasive is used. The larger the abrasive, the stronger its grinding force is, so as to remove larger burrs. When medium polishing, a slightly smaller abrasive is used to make the coating surface smoother. Abrasives of different coarseness, shapes, and sizes can also be mixed to achieve polishing at one time. At the same time, an appropriate amount of abrasive should be added during polishing to utilize its lubricating properties to protect against friction damage during the grinding process.

[0039] In an alternative embodiment, a fixture or electrical tape is used to protect non-coating deposited areas. The polishing material and the workpiece to be polished are placed in the finishing machine hopper. Abrasive and clean water are added, and polishing is performed at a frequency of 30-60 Hz for 20-60 minutes. After polishing, the workpiece is rinsed with clean water, the workpiece protective fixture or tape is removed, and ultrasonic cleaning is performed to clean surface residue. The workpiece is then placed in an oven at 60-100°C to dry for 10-30 minutes.

[0040] The laser-remelted and polished low-pressure plasma-sprayed FeCrAlY coating undergoes a further pre-oxidation treatment to create a continuous and dense thermally grown oxide layer in situ. This effectively reduces wettability with liquid lead-bismuth alloys and improves long-term service stability. All processes are performed within a vacuum chamber, effectively controlling dust, noise, and thermal pollution, minimizing environmental pollution and operator harm.

[0041] In an optional embodiment, the pre-oxidation includes heating the substrate to 800-1000° C. by using a plasma jet in a chamber at a pressure of 50-500 Pa, introducing an oxygen flow rate of 1-4 L / min, and holding the substrate for 5-25 minutes.

[0042] The Al in the coating has minimal free oxidation energy, and at low oxygen partial pressures, Al is preferentially oxidized, resulting in the in-situ formation of a dense, continuous, and uniform α-Al2O3 thermally grown oxide layer on the coating surface. Compared to NiCrAlY and CoCrAlY coatings, FeCrAlY coatings are more likely to form a dense Al2O3 film on their surface. This dense oxide film effectively isolates the liquid lead-bismuth alloy, improving its corrosion and erosion resistance.

[0043] In a second aspect, the present invention provides a composite coating resistant to liquid lead-bismuth erosion corrosion, which is prepared by the preparation method according to any one of the aforementioned embodiments.

[0044] In a third aspect, the present invention provides an application of the preparation method according to any one of the aforementioned embodiments in a nuclear energy system.

[0045] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0046] Example 1

[0047] This embodiment provides a method for preparing a composite coating resistant to liquid lead-bismuth erosion corrosion, comprising the following steps:

[0048] (1) After degreasing, sandblasting and transferred arc treatment, the substrate was preheated to 800 °C and a FeCrAlY coating with a thickness of 50 to 100 μm was prepared in a spray chamber filled with an Ar protective atmosphere and a pressure of 7.0 kPa. The plasma spray gun current was 720 A, the argon flow rate was 60 L / min, the hydrogen flow rate was 8 L / min, the spray distance was 280 mm, and the powder feeding rate was 15 g / min.

[0049] (2) A solid-state laser surface strengthening system was used to remelt the low-pressure plasma sprayed FeCrAlY coating. The spot diameter was 4 mm, the overlap was 1.5 mm, the laser power was 550 W, and the moving speed was 15 mm / s.

[0050] (3) Place the coarse and fine mixed brown corundum triangular stone abrasive and the coated workpiece to be polished in the hopper of the polishing machine, add abrasive and clean water, and polish at a frequency of 40 Hz for 40 minutes. After polishing, rinse the workpiece with clean water and ultrasonically clean it, then place the workpiece in an oven to dry.

[0051] (4) The coating was placed in a low-pressure plasma spraying chamber at a pressure of 100 Pa, oxygen was introduced at 2 L / min, and the substrate was heated to 900-950 °C by a plasma jet and kept warm for 20 min to generate an α-Al2O3 thermally grown oxide layer in situ on the coating surface.

[0052] The cross section of the liquid lead-bismuth erosion resistant composite coating prepared in this embodiment is observed under a scanning electron microscope to obtain the results as shown in Figure 1 The results show that the liquid lead-bismuth erosion resistant composite coating prepared in this embodiment has a compact structure and no defects such as large pores and cracks. Figure 1

[0053] Embodiment 2

[0054] The embodiment provides a preparation method of a liquid lead-bismuth erosion resistant composite coating, which comprises the following steps:

[0055] (1) After the substrate is degreased, sandblasted and transferred, the substrate is preheated to 700 DEG C. In a spraying chamber filled with an Ar protective atmosphere with a pressure of 4 kPa, a plasma spraying gun current is 700 A, an argon flow rate is 55 L / min, a hydrogen flow rate is 6 L / min, a helium flow rate is 4 L / min, a spraying distance is 350 mm, and a powder feeding rate is 18 g / min, so as to prepare a FeCrAlY coating with a thickness of 60-120 μm.

[0056] (2) The low-pressure plasma sprayed FeCrAlY coating is subjected to remelting treatment by using a solid laser surface strengthening system. The spot diameter is 5 mm, the overlap is 2 mm, the laser power is 550 W, and the moving speed is 15 mm / s.

[0057] (3) The coarse brown corundum abrasive and the coating workpiece to be polished are placed in the hopper of a polishing machine, abrasive and water are added, coarse polishing is performed at a frequency of 35 Hz for 30 min, the abrasive is replaced with finer brown corundum, and medium polishing is performed at a frequency of 33 Hz for 20 min. After polishing, the workpiece is cleaned with water and ultrasonic cleaning, and then the workpiece is placed in an oven for drying.

[0058] (4) The coating is placed in a low-pressure plasma spraying equipment chamber with a pressure of 200 Pa, 3 L / min of oxygen is introduced, the substrate is heated to 920-960 DEG C by using a plasma jet, and the substrate is kept at the temperature for 15 min, so as to generate an α-Al2O3 thermal growth oxide layer in situ on the surface of the coating.

[0059] Embodiment 3

[0060] The embodiment provides a preparation method of a liquid lead-bismuth erosion resistant composite coating, which comprises the following steps:

[0061] ​(1) After degreasing, sandblasting, and transferred arc treatment, the substrate was preheated to 850°C. In a spray chamber filled with Ar protective atmosphere and a pressure of 6 kPa, the plasma spray gun current was 750 A, the argon flow rate was 65 L / min, the hydrogen flow rate was 5 L / min, the spray distance was 320 mm, and the powder feed rate was 12 g / min to prepare a FeCrAlY coating with a thickness of 40 to 80 μm.

[0062] (2) A solid-state laser surface strengthening system was used to remelt the low-pressure plasma sprayed FeCrAlY coating. The spot diameter was 4 mm, the overlap was 2 mm, the laser power was 450 W, and the moving speed was 10 mm / s.

[0063] (3) Place the coarse and fine mixed brown corundum triangular stone abrasive and the coated workpiece to be polished in the hopper of the polishing machine, add abrasive and clean water, and polish at a frequency of 50 Hz for 30 minutes. After polishing, rinse the workpiece with clean water and ultrasonically clean it, then place the workpiece in an oven to dry.

[0064] (4) The coating was placed in a low-pressure plasma spraying chamber at a pressure of 300 Pa, oxygen was introduced at a flow rate of 2.5 l / min, and the substrate was heated to 880-920 °C by a plasma jet and kept warm for 18 minutes to generate an α-Al2O3 thermally grown oxide layer in situ on the coating surface.

[0065] Example 4

[0066] This embodiment provides a method for preparing a composite coating resistant to liquid lead-bismuth erosion corrosion, comprising the following steps:

[0067] (1) After degreasing, sandblasting, and transferred arc treatment, the substrate was preheated to 920°C. In a spray chamber filled with Ar protective atmosphere and a pressure of 12 kPa, the plasma spray gun current was 780 A, the argon flow rate was 52 L / min, the hydrogen flow rate was 6 L / min, the helium flow rate was 8 L / min, the spray distance was 220 mm, and the powder feed rate was 8 g / min to prepare FeCrAlY coatings with a thickness of 80 to 150 μm.

[0068] (2) A solid-state laser surface strengthening system was used to remelt the low-pressure plasma sprayed FeCrAlY coating. The spot diameter was 5 mm, the overlap was 2 mm, the laser power was 650 W, and the moving speed was 18 mm / s.

[0069] (3) Put the rough zirconia corundum abrasive and the workpiece to be polished and grinded into the hopper of the polishing machine, add the grinding agent and water, and coarsely polish for 25 min at a frequency of 45 Hz, then replace the abrasive with finer zircon beads and oblique triangular stones, and polish for 30 min at a frequency of 40 Hz, after polishing and grinding, clean the workpiece with water and ultrasonic cleaning, and then place the workpiece in an oven for drying.

[0070] (4) Put the coating into a chamber of a low-pressure plasma spraying device with a pressure of 250 Pa, input 3 l / min of oxygen, heat the substrate to 900-950 ℃ by using a plasma jet, and keep the temperature for 18 min, to generate an α-Al2O3 thermally grown oxide layer on the surface of the coating in situ.

[0071] Comparative Example 1

[0072] The present comparative example provides a method for preparing a liquid lead-bismuth scouring corrosion resistant composite coating, and the preparation method is the same as that of Example 1, except that the remelting and polishing treatment are not performed.

[0073] Comparative Example 2

[0074] The present comparative example provides a method for preparing a liquid lead-bismuth scouring corrosion resistant composite coating, and the preparation method is the same as that of Example 1, except that the polishing treatment is not performed.

[0075] Test Example 1

[0076] The liquid lead-bismuth scouring corrosion resistant composite coatings prepared in Examples 1-4 and Comparative Examples 1-2 are tested for surface roughness and internal porosity, and the results are shown in Table 1.

[0077] Table 1 Properties of the liquid lead-bismuth scouring corrosion resistant composite coatings

[0078] Surface roughness Ra, μm Porosity, % Example 1 2.5 0.2 Example 2 2.2 0.2 Example 3 2.6 0.4 Example 4 2.4 0.3 Comparative Example 1 5.6 0.8 Comparative Example 2 6.5 0.2

[0079] As shown in Table 1, the liquid lead-bismuth scouring corrosion resistant composite coating provided by the present application has a denser structure and a smoother surface, which can significantly improve the liquid lead-bismuth scouring corrosion resistance of the coating, and can significantly improve the service safety of the equipment and prolong the service life of the substrate.

[0080] The above is only a preferred embodiment of the present application, and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a composite coating resistant to liquid lead-bismuth erosion corrosion, characterized in that: The method comprises spraying a FeCrAlY coating on the surface of a substrate, remelting and finishing the FeCrAlY coating, and then pre-oxidizing the coating; The FeCrAlY coating is sprayed by low-pressure plasma spraying; The low-pressure plasma spraying conditions include: in an Ar protective atmosphere spray chamber with a pressure of 3.0-15.0 kPa, a plasma spray gun current of 600-850 A, an argon flow rate of 50-70 L / min, a hydrogen flow rate of 4-12 L / min, a helium flow rate of 0-10 L / min, a spray distance of 200-400 mm, and a powder feed rate of 5-20 g / min to prepare a FeCrAlY coating with a thickness of 40-200 μm.

2. The preparation method according to claim 1, characterized in that The remelting treatment includes any one of laser remelting and pulse electron beam treatment.

3. The preparation method according to claim 2, characterized in that The remelting process adopts laser remelting; the conditions of the laser remelting include: spot diameter of 3-5 mm, overlap of 1-2.5 mm, laser power of 250-650 W, and moving speed of 10-20 mm / s.

4. The preparation method according to claim 1, characterized in that The finishing treatment includes polishing the coating.

5. The preparation method according to claim 4, characterized in that The abrasive material includes at least one of brown corundum, high-aluminum porcelain, white corundum, zirconium beads, and high-frequency porcelain.

6. The preparation method according to claim 4, characterized in that The polishing frequency is 30~60Hz, and the polishing time is 20~60min.

7. The preparation method according to claim 1, characterized in that The pre-oxidation comprises heating the substrate to 800-1000° C. by using a plasma jet in a chamber at a pressure of 50-500 Pa, introducing an oxygen flow rate of 1-4 L / min, and holding the substrate for 5-25 minutes.

8. The preparation method according to any one of claims 2 to 7, characterized in that Before spraying the FeCrAlY coating, the substrate is pretreated, and the pretreatment includes degreasing, sandblasting, transferring arc cleaning and preheating the substrate in sequence; The preheating process includes preheating the substrate using plasma jet technology at a temperature of 600-1000°C.

9. A composite coating resistant to liquid lead-bismuth erosion corrosion, characterized in that: The method is as described in any one of claims 1 to 8.

10. Use of the preparation method according to any one of claims 1 to 8 in a nuclear energy system.

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