Pre-oxidized Al / FeCrAl / Al / Al2O3 coating resistant to high-temperature lead and bismuth corrosion and preparation method of pre-oxidized Al / FeCrAl / Al / Al2O3 coating

Abstract

The invention relates to the technical field of corrosion protection materials, and particularly discloses a pre-oxidized Al / FeCrAl / Al / Al2O3 coating resistant to high-temperature lead and bismuth corrosion and a preparation method of the pre-oxidized Al / FeCrAl / Al / Al2O3 coating aiming at the problems that in the process of coating the surface of an existing lead and bismuth pile material with an aluminum-containing coating, the direct bonding strength of a coating material and a base material is low, and the coating material and the base material are prone to cracking or falling off in a lead and bismuth pile service environment. The Al / FeCrAl / Al / Al2O3 coating comprises a FeCrAl layer and an Al2O3 layer, the FeCrAl layer and the Al2O3 layer are arranged on the surface of a base body in a covering mode, and an Al transition layer is arranged between the base body and the FeCrAl layer, and an Al transition layer is arranged between the FeCrAl layer and the Al2O3 layer. The composite coating can realize continuous interface enhancement in a simulated service environment, can keep excellent lead and bismuth corrosion resistance, has certain self-repairing capability through verification of prefabricated scratches, is simple in preparation process and low in cost, and has a good engineering application prospect.

Description

Technical Field

[0001] This invention relates to the field of corrosion protection materials technology, and more specifically, to a pre-oxidized Al / FeCrAl / Al / Al2O3 coating resistant to high-temperature lead-bismuth corrosion and its preparation method. Background Technology

[0002] With the accelerating pace of global technological and industrial iterations, particularly the rapid expansion of generative artificial intelligence, societal energy demand has soared to new heights. In the energy supply system, traditional fossil fuel-based energy utilization methods are facing increasingly prominent limitations due to severe problems such as climate change and environmental pollution. Nuclear energy, as a clean and efficient energy source, occupies an important position in my country's strategy of optimizing its energy structure and ensuring energy security, becoming a key option for addressing growing energy demand and environmental issues. Among the six advanced reactor types—gas-cooled fast reactors, lead-cooled fast reactors, molten salt reactors, sodium-cooled fast reactors, ultra-high-pressure gas-cooled reactors, and supercritical water-cooled reactors—lead-bismuth reactors demonstrate unique value in the energy supply field due to their outstanding advantages such as high output power, small core volume, inherent safety, and high uranium utilization rate. They possess irreplaceable application advantages, especially in scenarios such as powering remote areas, islands, ships, and constructing large nuclear power plants.

[0003] However, the engineering application of lead-bismuth reactors relies heavily on high-performance materials, among which structural materials with excellent comprehensive performance are crucial. The cladding tube, as the first safety barrier isolating radioactive materials from the external environment, directly determines the safety and economy of the nuclear energy system and is vital to the stable operation of the lead-bismuth reactor. Compared to the currently operational second- and third-generation reactors, the design and service conditions of fourth-generation nuclear energy systems are far more demanding. Taking lead-bismuth reactor cladding as an example, its service temperature must exceed 500°C, it must withstand neutron radiation doses greater than 100 dPa, and it must also resist severe liquid metal corrosion. This places extremely high demands on the comprehensive performance of the cladding material, including its mechanical properties, radiation resistance, and resistance to high-temperature lead-bismuth corrosion.

[0004] Based on the above, it has been proposed to coat the surface with an Al-containing coating or an Al-containing coating. l2 Methods such as O3 coating are used to solve the lead-bismuth corrosion problem. For example, patent CN115852326A proposes a method for preparing a FeCrAlYTi high-entropy alloy coating resistant to liquid lead / lead-bismuth corrosion. The FeCrAlYTi high-entropy alloy coating is prepared by a five-target co-sputtering magnetron sputtering method with Fe, Cr, Al, Y and Ti targets. The sputtering power of each target is controlled individually, with a sputtering power of 100~300W. By adjusting the sputtering power of each target, a near-equal molar ratio of FeCrAlYTi high-entropy alloy coating is obtained.

[0005] However, current methods of applying Al-containing coatings to the substrate surface have the following problems: directly applying Al-containing coatings to the substrate surface in the lead-bismuth stack service environment will cause the coating to crack or peel off due to sudden changes in the composition and properties of the interface material, affecting the normal operation and service life of the substrate material. Summary of the Invention

[0006] The purpose of this invention is to solve the problem that in existing lead-bismuth stack materials with aluminum-containing coatings, the bonding strength between the coating material and the substrate material is low, and cracking or peeling is likely to occur in the service environment of lead-bismuth stacks.

[0007] This invention is achieved through the following technical solution: The present invention provides a pre-oxidized Al / FeCrAl / Al / Al2O3 coating resistant to high-temperature lead-bismuth corrosion, comprising a FeCrAl layer and an Al2O3 layer coated on the surface of a substrate, wherein an Al transition layer is provided between the substrate and the FeCrAl layer, and between the FeCrAl layer and the Al2O3 layer.

[0008] The present invention also provides a method for preparing the pre-oxidized Al / FeCrAl / Al / Al2O3 coating resistant to high-temperature lead-bismuth corrosion as described above, comprising the following steps: S1 Matrix pretreatment; S2 uses magnetron sputtering to turn on the Al target and coat the substrate surface with an Al transition layer; S3 Turn on the FeCr target and Al target, and coat the surface of the Al transition layer obtained in S2 with a FeCrAl layer. S4 Turn on the Al target and coat the FeCrAl layer obtained in S3 with an Al transition layer. S5 Turn on the Al target and introduce oxygen to coat the surface of the Al transition layer obtained in S4 with an Al2O3 layer to form an initial composite coating. S6 The substrate on which the initial composite coating is formed is heated and kept at a constant temperature to remove stress; then it is heated and kept at a constant temperature to perform a pre-oxidation treatment, thereby obtaining the Al / FeCrAl / Al / Al2O3 coating.

[0009] Preferably, in steps S2 and S4, the parameters of the Al target are set as follows: power 1-3kW, frequency 220-260Hz, voltage 700-740V, current 230-270A, and pulse width 55-65μs.

[0010] Preferably, in steps S2 and S4, the deposition time is 5-8 minutes.

[0011] Preferably, in step S3, the parameters of the FeCr target are set as follows: power 3-8kW, frequency 280-320Hz, voltage 700-740V, and current 220-280A.

[0012] Preferably, in step S3, the deposition time is 10-15 min.

[0013] Preferably, in step S5, oxygen at 10-20 sccm is introduced, and argon at 75-85 sccm is also introduced; the parameters of the Al target are: power 5-6kW, frequency 825-830Hz, voltage 400-4410V, and current 255-265A.

[0014] Preferably, in step S5, the deposition time is 2 to 10 hours.

[0015] Preferably, in steps S2 to S5, the argon flow rate is adjusted to 80±5 sccm, the cavity pressure is 0.3-0.8 Pa, the matrix negative bias is 170-190 V, the frequency is 75-85 kHz, and the pulse width is 58-62 μs.

[0016] Preferably, in step S6, the temperature is first heated to 300~500℃ and held for 2~5 hours to remove stress; then heated to 400~600℃ and held for 1000~2000 hours for pre-oxidation treatment.

[0017] The technical solution of the present invention has the following beneficial effects: This invention employs a multi-layered metal-ceramic Al / FeCrAl / Al / Al2O3 composite layer material, which sequentially includes an Al transition layer, a FeCrAl layer, an Al transition layer, and an Al2O3 layer. This Al / FeCrAl / Al / Al2O3 coating exhibits superior chemical stability, excellent corrosion resistance and wear resistance, high hardness, and high strength, demonstrating good engineering application potential under environments of strong erosion, high temperature, strong corrosion, and high radiation.

[0018] High-power pulsed magnetron sputtering technology is used to deposit different materials layer by layer onto the substrate surface, forming a dense multilayer composite coating. The FeCrAl layer has a body-centered cubic structure, while the Al2O3 layer has an amorphous structure, resulting in interfacial strengthening during corrosion. Furthermore, through the process parameters and heat treatment processes defined in this invention, the coated product exhibits even better corrosion resistance after corrosion.

[0019] Using single Al and FeCr targets to simultaneously prepare FeCrAl coatings makes it very easy to adjust the elemental content of the coating, with low cost and convenient operation. By adjusting the target current and substrate bias voltage, FeCrAl coatings with different component contents can be obtained. By controlling the aluminum content in the FeCrAl layer, oxygen can be prevented from contacting the substrate, giving it a certain self-healing function in the high-temperature liquid lead-bismuth alloy corrosion environment. Furthermore, the specific component content of FeCrAl is determined according to the composition of the reactor structural materials to ensure slow changes in the composition of the substrate / Al / FeCrAl interface, thereby improving the bonding strength between the coating and the substrate during service.

[0020] In addition, after deposition, the coated substrate is placed in a vacuum chamber and kept in a high-temperature environment for heat preservation treatment. This can improve the bonding force between the coating and the structural material. On the one hand, the residual stress in the coating is released by heating and heat preservation, which avoids cracking and failure during corrosion. On the other hand, heating makes the coating composition more uniform, which provides a good foundation for strengthening the interface strength during corrosion. Attached Figure Description

[0021] Figure 1 This is a 500x magnified SEM image of the Al / FeCrAl / Al / Al2O3 coating in Example 1. Figure 2 These are comparative images of the morphology and energy dispersive spectroscopy of different transition layers of the composite coatings in Example 1, Comparative Example 1, and Comparative Example 3 after corrosion. Figure 3 The image shows the morphology and energy dispersive spectroscopy (EDS) of the Al / FeCrAl / Al / Al2O3 coating in Example 1 after pre-prepared scratch etching. Figure 4 This is a comparison diagram of the critical loads of different transition layers in the Al / FeCrAl / Al / Al2O3 coatings in Example 1 and Comparative Example 2; Figure 5 This is a TEM image of the Al / FeCrAl / Al / Al2O3 coating in Example 1.

[0022] Specific implementation details To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, they are performed according to conventional conditions or conditions recommended by the manufacturer; where the manufacturers of the instruments, equipment, reagents, or raw materials used are not specified, they are all conventional products that can be purchased commercially.

[0023] The present invention provides a pre-oxidized Al / FeCrAl / Al / Al2O3 coating resistant to high-temperature lead-bismuth corrosion, comprising a FeCrAl layer and an Al2O3 layer coated on the surface of a substrate, wherein an Al transition layer is provided between the substrate and the FeCrAl layer, and between the FeCrAl layer and the Al2O3 layer.

[0024] The present invention also provides a method for preparing the above-mentioned pre-oxidized Al / FeCrAl / Al / Al2O3 coating resistant to high-temperature lead-bismuth corrosion, comprising the following steps: (1) Sample preparation and pretreatment Take the internal structural material and polish it with 500~2000 grit sandpaper. Then polish its surface to a mirror state with 0.5μm SiO2 polishing liquid. Then ultrasonically clean it with anhydrous ethanol and acetone in sequence. Finally, place it in a drying oven to dry it to obtain the sample to be coated.

[0025] First, the sample surface is cleaned to prevent excessive surface roughness from causing surface undulations to exceed the film thickness. At the same time, surface contaminants are removed to ensure good adhesion of the coating.

[0026] In this context, in-core structural materials refer to materials used inside a nuclear reactor to support fuel assemblies, guide coolant flow, maintain core geometry, and withstand high-temperature, high-pressure, and radiation environments. Here, it refers to the substrate material to which the Al / FeCrAl / Al / Al2O3 coating is applied. By coating the surface of the in-core structural materials with an Al / FeCrAl / Al / Al2O3 coating, the materials acquire excellent resistance to high temperatures and lead-bismuth corrosion. Specifically, in-core structural materials are often iron-chromium-aluminum alloys, low-activation ferritic / martensitic steels, or austenitic steels.

[0027] The sample was placed on a fixed workpiece holder and then placed inside the vacuum chamber of a high-power pulsed magnetron sputtering equipment for pretreatment. Specifically, FeCr and Al targets were mounted on the inner wall of the vacuum chamber, and then the vacuum was evacuated to approximately 1 × 10⁻⁶. -3 Pa and below, heated to 400±20℃, when the vacuum degree is below 1×10 -3 After Pa, argon gas is introduced to about 2 Pa, and the negative bias voltage of the sample is set to 800~1000V. The sample surface is bombarded with Ar ions for 10~20 min to obtain the pretreated sample, which serves as the substrate for the coating material.

[0028] Ar ion bombardment further removes impurities from the surface of the in-pile structural materials, and under these treatment conditions and parameters, the bonding force between the subsequent Al / FeCrAl / Al / Al2O3 coating and the in-pile structural material matrix is ​​significantly enhanced.

[0029] (2) Preparation of Al / FeCrAl / Al / Al2O3 coating Inside the original vacuum furnace, the magnetron sputtering power supply was set to frequency control mode, and the Al target was turned on. The Al target parameters were set as follows: power 1-3kW, frequency 220-260Hz, voltage 700-740V, current 230-270A, and pulse width 55-65μs. The argon flow rate was adjusted to 80±5sccm, the cavity pressure to 0.3-0.8Pa, the substrate negative bias voltage to 170-190V, the frequency to 75-85kHz, the pulse width to 58-62μs, and the deposition time to 5-8min, thus forming an Al transition layer on the sample surface after pretreatment.

[0030] Keep the magnetron sputtering power supply set to frequency control mode, and simultaneously turn on the FeCr and Al targets. Set the FeCr target parameters as follows: power 3-8kW, frequency 280-320Hz, voltage 700-740V, current 220-280A; set the Al target parameters as follows: power 1-3kW, frequency 220-260Hz, voltage 700-740V, current 230-270A, pulse width 55-65μs; and adjust the argon flow rate to 80±5sccm, the gas pressure to 0.3-0.8Pa, the substrate negative bias voltage to 170-190V, the frequency to 75-85kHz, the pulse width to 58-62μs, and the deposition time to 10-15 min to form a FeCrAl layer on the Al transition layer surface.

[0031] Using a single Al and FeCr target to simultaneously prepare FeCrAl coatings makes it very easy to adjust the elemental content of the coating, with low cost and convenient operation. By adjusting the target current and substrate bias voltage, FeCrAl coatings with different component contents can be obtained. In the FeCrAl layer, the FeCr target is made of a material similar to that of the reactor structural material sample, and the composition of FeCrAl is determined according to the composition of the reactor structural material to ensure slow changes in the composition of the substrate / Al / FeCrAl interface, thereby improving the bonding strength between the coating and the substrate during service. For example, if the reactor structural material is 12Cr low-activation ferritic / martensitic steel, then Fe12Cr is used as the target. The aluminum content can be controlled by controlling the output power of the power supply, preferably 260W, and the Al content is controlled at 4~10wt%. Within this range, oxygen can be blocked from contacting the substrate, and a certain self-healing function is provided in the high-temperature liquid lead-bismuth alloy corrosion environment.

[0032] Keep the magnetron sputtering power supply set to frequency control mode, turn on the Al target, and set the Al target parameters as follows: power 1-3kW, frequency 220-260Hz, voltage 700-740V, current 230-270A, pulse width 55-65μs; and adjust the argon flow rate to 80±5sccm, the gas pressure to 0.3-0.8Pa, the substrate negative bias voltage to 170-190V, the frequency to 75-85kHz, the pulse width to 58-62μs, and the deposition time to 5-8min, so as to form an Al transition layer on the surface of the FeCrAl layer.

[0033] Then, argon gas at a rate of approximately 75-85 sccm and oxygen gas at a rate of approximately 10-20 sccm are introduced into the furnace until the gas pressure inside the furnace reaches approximately 0.5 Pa. The pumping speed baffle is set to 60°. The power supply parameters for the Al target are set as follows: power 5-6 kW, frequency 825-830 Hz, voltage 400-4410 V, current 255-265 A, substrate negative bias voltage 170-190 V, frequency 75-85 kHz, pulse width 58-62 μs, and deposition time 2-10 h. An Al2O3 layer is formed on the surface. Once the coating thickness reaches the set thickness, the coating process is stopped, and the initial composite coating is obtained.

[0034] Al transition layers are provided between the substrate sample and the FeCrAl layer, and between the FeCrAl layer and the Al2O3 layer. The Al transition layers can diffuse into the substrate through thermal diffusion, and at the same time, they can prevent oxygen in the environment from contacting the substrate sample by reacting with Al and oxygen.

[0035] (3) Stress relief treatment After the coating is completed, the sample with the initial composite coating on the surface is placed in a vacuum chamber and kept at 300~500℃ for 2~5 hours. Then it is cooled with the furnace to allow the coating to cool naturally to room temperature, thus obtaining a sample with a stress-relief composite coating on the surface.

[0036] (4) Pre-oxidation treatment The sample with the stress-relief composite coating on the surface was then placed at 400~600℃ and kept at that temperature for 1000~2000h to obtain a sample with an Al / FeCrAl / Al / Al2O3 coating on the surface.

[0037] This invention employs high-power pulsed magnetron sputtering to prepare an Al / FeCrAl / Al / Al2O3 coating on the surface of in-pile structural material samples. High-power pulsed magnetron sputtering has the advantages of high ionization rate, dense film structure, and high ion energy, thereby ensuring the uniformity and high bonding strength of the coating. Ultimately, a dense composite coating is formed, exhibiting excellent resistance to lead and bismuth corrosion. In particular, the interfacial bonding strength can be continuously strengthened during service, making it highly valuable for application in high-temperature lead and bismuth reactors. Furthermore, under the aforementioned high-power pulsed magnetron sputtering process parameters such as gas flow rate, pulse current, pulse voltage, frequency, power, and substrate bias, a dense amorphous Al / FeCrAl / Al / Al2O3 coating can be obtained at a relatively low temperature. During the high-temperature lead-bismuth corrosion pre-oxidation process, an intermetallic compound Fe2CrAl is formed at the interface between the substrate and the FeCrAl layer. Cr at the FeCrAl / Al / Al2O3 interface diffuses into Al2O3 and reacts with oxygen. The pinning effect on both sides of FeCrAl greatly enhances the bonding strength of the coating, thus ensuring that the coating does not peel off during service. At the same time, the results of lead-bismuth corrosion of the FeCrAl / Al / Al2O3 coating at approximately 550℃ show that Al2O3 can still maintain its amorphous structure, indicating that the coating has excellent corrosion resistance.

[0038] Example 1 In this embodiment, an Al / FeCrAl / Al / Al2O3 coating is prepared onto the substrate surface using high-power pulsed magnetron sputtering. The specific steps are as follows: Step 1: Take the 12Cr ferritic / martensitic steel, the structural material of the pile, and polish the surface of the 12Cr ferritic / martensitic steel with 500#, 1000# and 2000# silicon carbide sandpaper in sequence. Then polish it to a mirror finish with polishing liquid containing 0.5μm SiO2. Then ultrasonically clean it with anhydrous ethanol and acetone in sequence. After that, take it out and put it in a drying oven to dry for later use.

[0039] Step 2: Fix the substrate prepared in Step 1 onto the workpiece holder, and then place it into the vacuum chamber of a high-power pulsed magnetron sputtering equipment. The FeCr and Al targets are mounted on the inner wall of the vacuum chamber, and then the vacuum is evacuated to approximately 1 × 10⁻⁶. - 3 Pa, heated to 400℃, when the vacuum degree is less than 1×10 -3 After Pa, argon gas is introduced to about 2 Pa, the negative bias voltage of the sample is set to 1000V, and the sample surface is subjected to Ar ion bombardment treatment for 15 min to obtain the substrate to be coated.

[0040] Step 3: Continue in the vacuum furnace, set the magnetron sputtering power supply to frequency control mode, and turn on the Al target. Set the Al target parameters as follows: power 2kW, frequency 240Hz, voltage 720V, current 250A, pulse width 60μs; and adjust the argon flow rate to 80sccm, the cavity pressure to 0.5Pa, the substrate negative bias voltage to 180V, the frequency to 80kHz, the pulse width to 60μs, and the deposition time to 6min, to form an Al transition layer on the substrate surface.

[0041] Step 4: Keep the magnetron sputtering power supply set to frequency control mode, and simultaneously turn on the FeCr and Al targets. The FeCr target consists of 88wt% Fe and 12wt% Cr. Set the FeCr target parameters as follows: power 5kW, frequency 300Hz, voltage 720V, current 250A; set the Al target parameters as follows: power 2kW, frequency 240Hz, voltage 720V, current 250A, pulse width 60μs; and adjust the argon flow rate to 80sccm, the gas pressure to 0.5Pa, the substrate negative bias voltage to 180V, the frequency to 80kHz, the pulse width to 60μs, and the deposition time to 12 min. A FeCrAl layer is formed on the surface of the Al transition layer, with an Al content of 6.0wt%.

[0042] Step 5: Keep the magnetron sputtering power supply set to frequency control mode, turn on the Al target, and set the Al target parameters as follows: power 2kW, frequency 240Hz, voltage 720V, current 250A, pulse width 60μs; and adjust the argon flow rate to 80sccm, gas pressure to 0.5Pa, substrate negative bias voltage to 180V, frequency to 80kHz, pulse width to 60μs, and deposition time to 6min, so as to form another Al transition layer on the surface of the FeCrAl layer.

[0043] Step Six: Then, introduce approximately 79 sccm of argon and approximately 15 sccm of oxygen into the furnace until the pressure inside the furnace reaches approximately 0.5 Pa. Set the pumping speed baffle to 60° and set the power parameters for the Al target as follows: power 5.5 kW, frequency 828 Hz, voltage 406 V, current 259.3 A, substrate negative bias voltage 180 V, frequency 80 kHz, pulse width 60 μs, and deposition time 5 h. An Al2O3 layer is formed on the surface of the Al transition layer obtained in Step Five.

[0044] Step 7: Place the coating-substrate material after the coating in Step 6 into a vacuum chamber and keep it at 400℃ for 3 hours. Then cool it to room temperature with the furnace. Place it at 500℃ for pre-oxidation treatment and keep it at 500℃ for 1500 hours to obtain 12Cr ferritic / martensitic steel with an Al / FeCrAl / Al / Al2O3 coating on the surface.

[0045] Comparative Example 1 This comparative example uses high-power pulsed magnetron sputtering to prepare a FeCrAl / Al2O3 coating on the substrate surface. The specific steps are as follows: Step 1: Take the 12Cr ferritic / martensitic steel, the structural material of the pile, and polish the surface of the 12Cr ferritic / martensitic steel with 500#, 1000# and 2000# silicon carbide sandpaper in sequence. Then polish it to a mirror finish with polishing liquid containing 0.5μm SiO2. Then ultrasonically clean it with anhydrous ethanol and acetone in sequence. After that, take it out and put it in a drying oven to dry for later use.

[0046] Step 2: Fix the substrate prepared in Step 1 onto the workpiece holder, and then place it into the vacuum chamber of a high-power pulsed magnetron sputtering equipment. The FeCr and Al targets are mounted on the inner wall of the vacuum chamber, and then the vacuum is evacuated to approximately 1 × 10⁻⁶. - 3 Pa, heated to 400℃, when the vacuum degree is less than 1×10 -3 After Pa, argon gas is introduced to about 2 Pa, the negative bias voltage of the sample is set to 1000V, and the sample surface is subjected to Ar ion bombardment treatment for 15 min to obtain the substrate to be coated.

[0047] Step 3: Continue in the vacuum furnace, keeping the magnetron sputtering power supply set to frequency control mode, and simultaneously turn on the FeCr and Al targets. Set the FeCr target parameters as follows: power 5kW, frequency 300Hz, voltage 720V, current 250A; set the Al target parameters as follows: power 2kW, frequency 240Hz, voltage 720V, current 250A, pulse width 60μs; and adjust the argon flow rate to 80sccm, the gas pressure to 0.5Pa, the substrate negative bias voltage to 180V, the frequency to 80kHz, the pulse width to 60μs, and the deposition time to 12 min, forming a FeCrAl layer on the substrate surface.

[0048] Step 4: Then, introduce approximately 79 sccm of argon and approximately 15 sccm of oxygen into the furnace until the pressure inside the furnace reaches approximately 0.5 Pa. Set the pumping speed baffle to 60° and set the power parameters for the Al target as follows: power 5.5 kW, frequency 828 Hz, voltage 406 V, current 259.3 A, substrate negative bias voltage 180 V, frequency 80 kHz, pulse width 60 μs, and deposition time 5 h to form an Al2O3 layer on the FeCrAl layer surface.

[0049] Step 5: Place the coating-substrate material after the coating in Step 6 into a vacuum chamber and keep it at 400℃ for 3 hours. Then cool it to room temperature with the furnace to obtain 12Cr ferritic / martensitic steel with FeCrAl / Al2O3 coating on the surface.

[0050] Comparative Example 2 This comparative example uses high-power pulsed magnetron sputtering to prepare an Al / Al2O3 coating on the substrate surface. The specific steps are as follows: Step 1: Take the 12Cr ferritic / martensitic steel, the structural material of the pile, and polish the surface of the 12Cr ferritic / martensitic steel with 500#, 1000# and 2000# silicon carbide sandpaper in sequence. Then polish it to a mirror finish with polishing liquid containing 0.5μm SiO2. Then ultrasonically clean it with anhydrous ethanol and acetone in sequence. After that, take it out and put it in a drying oven to dry for later use.

[0051] Step 2: Fix the substrate prepared in Step 1 onto the workpiece holder, and then place it into the vacuum chamber of a high-power pulsed magnetron sputtering equipment. The FeCr and Al targets are mounted on the inner wall of the vacuum chamber, and then the vacuum is evacuated to approximately 1 × 10⁻⁶. - 3 Pa, heated to 400℃, when the vacuum degree is less than 1×10 -3 After Pa, argon gas is introduced to about 2 Pa, the negative bias voltage of the sample is set to 1000V, and the sample surface is subjected to Ar ion bombardment treatment for 15 min to obtain the substrate to be coated.

[0052] Step 3: Continue in the vacuum furnace, set the magnetron sputtering power supply to frequency control mode, and turn on the Al target. Set the Al target parameters as follows: power 2kW, frequency 240Hz, voltage 720V, current 250A, pulse width 60μs; and adjust the argon flow rate to 80sccm, the cavity pressure to 0.5Pa, the substrate negative bias voltage to 180V, the frequency to 80kHz, the pulse width to 60μs, and the deposition time to 12min to form an Al layer on the substrate surface.

[0053] Step 4: Then, introduce approximately 79 sccm of argon and approximately 15 sccm of oxygen into the furnace until the pressure inside the furnace reaches approximately 0.5 Pa. Set the pumping speed baffle to 60° and set the power parameters for the Al target as follows: power 5.5 kW, frequency 828 Hz, voltage 406 V, current 259.3 A, substrate negative bias voltage 180 V, frequency 80 kHz, pulse width 60 μs, and deposition time 5 h to form an Al2O3 layer on the Al surface.

[0054] Step 5: Place the coating-substrate material after the coating in Step 6 into a vacuum chamber and keep it at 400℃ for 3 hours. Then cool it to room temperature with the furnace to obtain 12Cr ferritic / martensitic steel with an Al / Al2O3 coating on the surface.

[0055] Comparative Example 3 In this comparative example, a Mo / Al2O3 coating was prepared on the substrate surface using high-power pulsed magnetron sputtering. The specific steps are as follows: Step 1: Take the 12Cr ferritic / martensitic steel, the structural material of the pile, and polish the surface of the 12Cr ferritic / martensitic steel with 500#, 1000# and 2000# silicon carbide sandpaper in sequence. Then polish it to a mirror finish with polishing liquid containing 0.5μm SiO2. Then ultrasonically clean it with anhydrous ethanol and acetone in sequence. After that, take it out and put it in a drying oven to dry for later use.

[0056] Step 2: Fix the substrate prepared in Step 1 onto the workpiece holder, and then place it into the vacuum chamber of a high-power pulsed magnetron sputtering equipment. The FeCr and Al targets are mounted on the inner wall of the vacuum chamber, and then the vacuum is evacuated to approximately 1 × 10⁻⁶. - 3 Pa, heated to 400℃, when the vacuum degree is less than 1×10 -3 After Pa, argon gas is introduced to about 2 Pa, the negative bias voltage of the sample is set to 1000V, and the sample surface is subjected to Ar ion bombardment treatment for 15 min to obtain the substrate to be coated.

[0057] Step 3: Continue in the vacuum furnace, set the magnetron sputtering power supply to frequency control mode, and turn on the Mo target. Set the Mo target parameters as follows: power 2kW, frequency 240Hz, voltage 720V, current 250A, pulse width 60μs; and adjust the argon flow rate to 80sccm, the cavity pressure to 0.5Pa, the substrate negative bias voltage to 180V, the frequency to 80kHz, the pulse width to 60μs, and the deposition time to 12min to form a Mo layer on the substrate surface.

[0058] Step 4: Then, introduce approximately 79 sccm of argon and approximately 15 sccm of oxygen into the furnace until the pressure inside the furnace reaches approximately 0.5 Pa. Set the pumping speed baffle to 60° and set the power parameters for the Al target as follows: power 5.5 kW, frequency 828 Hz, voltage 406 V, current 259.3 A, substrate negative bias voltage 180 V, frequency 80 kHz, pulse width 60 μs, and deposition time 5 h to form an Al2O3 layer on the surface of the Mo layer.

[0059] Step 5: Place the coating-substrate material after the coating in Step 6 into a vacuum chamber and keep it at 400℃ for 3 hours. Then cool it to room temperature with the furnace to obtain 12Cr ferritic / martensitic steel with a Mo / Al2O3 coating on the surface.

[0060] Test case Samples: Example 1, Comparative Examples 1-3 (1) such as Figure 1 The image shown is a scanning electron microscope (SEM) image of the Al / FeCrAl / Al / Al2O3 coating prepared in Example 1. As can be seen from the image, the surface of the composite coating is smooth and the texture is uniform.

[0061] (2) such as Figure 2 The figure shows a comparison of the morphology and energy dispersive spectroscopy (EDS) of different transition layers after corrosion in Example 1, Comparative Examples 1 and 3. The transition layers between the substrate and the alumina coating in the three examples are Al transition layer, FeCrAl transition layer, and Mo transition layer, respectively. As can be seen from the figure, the transition layer prepared using Example 1 has more obvious morphological stability and corrosion resistance.

[0062] (3) such as Figure 3 The figure shows the morphology and energy dispersive spectroscopy (EDS) of the Al / FeCrAl / Al / Al2O3 coating prepared in Example 1 after pre-existing scratch etching. As can be seen from the figure, the Al / FeCrAl / Al / Al2O3 coating exhibits a certain degree of self-repairing effect after etching to address existing scratches.

[0063] (4) such as Figure 4 The figure shows a comparison of the critical loads of different transition layers in the Al / FeCrAl / Al / Al2O3 coatings of Example 1 and Comparative Example 2. As can be seen from the figure, the multilayer composite coating proposed in this invention, which uses Al as the transition layer and incorporates a FeCrAl layer, has a dense structure and can exert a significant interface strengthening effect during corrosion. That is, this composite coating has more significant bonding strength and stability.

[0064] (5) such as Figure 5 The image shows a transmission electron microscope (TEM) image of the Al / FeCrAl / Al / Al2O3 coating prepared in Example 1. (a) is the TEM image of the lead-permeated region, (b) is the TEM image of the Al2O3 coating region, (c) is the TEM image of the FeCrAl coating region, and (d) is the TEM image of the substrate region. As can be seen from the image, the composite coating exhibits significant interfacial strengthening between itself and the substrate, and after corrosion, it also demonstrates superior corrosion resistance.

[0065] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pre-oxidized Al / FeCrAl / Al / Al2O3 coating resistant to high-temperature lead-bismuth corrosion, characterized in that, It includes a FeCrAl layer and an Al2O3 layer coated on the surface of a substrate, and an Al transition layer is provided between the substrate and the FeCrAl layer, and between the FeCrAl layer and the Al2O3 layer.

2. A method for preparing a pre-oxidized, high-temperature resistant lead-bismuth corrosion-resistant Al / FeCrAl / Al / Al2O3 coating as described in claim 1, characterized in that, Includes the following steps: S1 Matrix pretreatment; S2 uses magnetron sputtering to turn on the Al target and coat the substrate surface with an Al transition layer; S3 Turn on the FeCr target and Al target, and coat the surface of the Al transition layer obtained in S2 with a FeCrAl layer. S4 Turn on the Al target and coat the FeCrAl layer obtained in S3 with an Al transition layer. S5 Turn on the Al target and introduce oxygen to coat the surface of the Al transition layer obtained in S4 with an Al2O3 layer to form an initial composite coating. S6 Heat and heat the substrate on which the initial composite coating is applied to remove stress. The coating is then heated and kept at a constant temperature for pre-oxidation treatment to obtain the Al / FeCrAl / Al / Al2O3 coating.

3. The method for preparing the pre-oxidized, high-temperature resistant lead-bismuth corrosion-resistant Al / FeCrAl / Al / Al2O3 coating according to claim 2, characterized in that, In steps S2 and S4, the parameters for setting the Al target are: power 1-3kW, frequency 220-260Hz, voltage 700-740V, current 230-270A, and pulse width 55-65μs.

4. The method for preparing the pre-oxidized, high-temperature resistant lead-bismuth corrosion-resistant Al / FeCrAl / Al / Al2O3 coating according to claim 3, characterized in that, In steps S2 and S4, the deposition time is 5-8 minutes.

5. The method for preparing the pre-oxidized, high-temperature resistant lead-bismuth corrosion-resistant Al / FeCrAl / Al / Al2O3 coating according to claim 2, characterized in that, In step S3, the parameters for setting the FeCr target are: power 3-8kW, frequency 280-320Hz, voltage 700-740V, and current 220-280A.

6. The method for preparing the pre-oxidized, high-temperature resistant lead-bismuth corrosion-resistant Al / FeCrAl / Al / Al2O3 coating according to claim 5, characterized in that, In step S3, the deposition time is 10-15 min.

7. The method for preparing the pre-oxidized, high-temperature resistant lead-bismuth corrosion-resistant Al / FeCrAl / Al / Al2O3 coating according to claim 2, characterized in that, In step S5, oxygen gas at 10-20 sccm is introduced, and argon gas at 75-85 sccm is also introduced. The parameters of the Al target are: power 5-6 kW, frequency 825-830 Hz, voltage 400-4410 V, and current 255-265 A.

8. The method for preparing the pre-oxidized, high-temperature resistant lead-bismuth corrosion-resistant Al / FeCrAl / Al / Al2O3 coating according to claim 7, characterized in that, In step S5, the deposition time is 2~10h.

9. The method for preparing the pre-oxidized, high-temperature resistant lead-bismuth corrosion-resistant Al / FeCrAl / Al / Al2O3 coating according to claim 2, characterized in that, In steps S2 to S5, the argon flow rate is adjusted to 80±5 sccm, the cavity pressure is 0.3-0.8 Pa, the matrix negative bias is 170-190 V, the frequency is 75-85 kHz, and the pulse width is 58-62 μs.

10. The method for preparing the pre-oxidized, high-temperature resistant lead-bismuth corrosion-resistant Al / FeCrAl / Al / Al2O3 coating according to claim 2, characterized in that, In step S6, the temperature is first heated to 300~500℃ and held for 2~5 hours to remove stress; then heated to 400~600℃ and held for 1000~2000 hours for pre-oxidation treatment.

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