A high-temperature resistant and corrosion-resistant composite film for liquid metal environments and its preparation method

Abstract

This invention provides a high-temperature resistant and corrosion-resistant composite film for use in liquid metal environments and its preparation method. The high-temperature resistant and corrosion-resistant composite film comprises an inner passivation layer, an intermediate barrier layer, and an outer functional layer sequentially fixed to the surface of a metal substrate. The inner passivation layer is an oxide; the intermediate barrier layer is an amorphous material; and the outer functional layer is a ceramic material. This invention ensures adhesion through the oxide passivation layer, blocks diffusion through the amorphous barrier layer, and provides stability and self-healing properties through the ceramic material functional layer. Through the synergistic effect of these three layers, it protects structural materials in contact with liquid metals, extends equipment life, and improves system safety and economy, solving the problems of poor protection and performance degradation inherent in traditional single-coating systems.

Description

Technical Field

[0001] This invention relates to the field of materials surface engineering technology, specifically to a high-temperature resistant and corrosion-resistant composite film for liquid metal environments and its preparation method. Background Technology

[0002] With the development of fourth-generation nuclear energy systems, fusion reactor blankets, and new high-efficiency thermal management technologies, liquid metals (such as lead-bismuth eutectic alloys and metallic lithium) have become key working fluids due to their excellent thermophysical properties. However, liquid metal corrosion is one of the core bottlenecks limiting their large-scale application in high-tech fields. At high temperatures, liquid metals exhibit extremely strong corrosiveness to structural materials (such as steel and nickel-based alloys), leading to material failure and seriously threatening system safety and lifespan. High-temperature liquid metals can rapidly damage structural alloys through mechanisms such as dissolution, corrosion, and interdiffusion.

[0003] Traditional protection strategies mainly focus on material selection (such as using high-silicon steel or austenitic stainless steel) or surface formation of a single oxide film (such as generating Al2O3 or Cr2O3 films through oxygen control technology). However, material selection is often costly and its mechanical properties do not meet requirements. Single oxide films have the following inherent defects: 1) The film layer usually contains defects such as grain boundaries and dislocations, providing rapid diffusion channels for liquid metal atoms; 2) The thermal expansion coefficient does not match the substrate, making it prone to cracking and peeling during thermal cycling; 3) Once local damage occurs, it lacks self-repair capability, and corrosion will rapidly spread inward from the damaged point. In recent years, some studies have attempted to prepare ceramic coatings (such as TiN and CrN) using physical vapor deposition (PVD) or oxide coatings (such as Y2O3) using thermal spraying. However, the protective performance of these single coatings deteriorates during long-term service due to the presence of microscopic defects.

[0004] To address the aforementioned problems, this invention urgently requires a multi-layer composite film to enhance the comprehensive protective performance that a single coating cannot achieve. Summary of the Invention

[0005] Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a high-temperature resistant and corrosion-resistant composite material for liquid metal environments and its preparation method, thus solving the problems mentioned in the background section.

[0006] Technical solution To achieve the above objectives, the present invention provides the following technical solution: According to a first aspect of the present invention, a high-temperature resistant and corrosion-resistant composite film for use in liquid metal environments is provided, comprising an inner passivation layer, an intermediate barrier layer, and an outer functional layer sequentially fixed to the surface of a metal substrate. The inner passivation layer is an oxide; The intermediate barrier layer is an amorphous material; The outer functional layer is made of ceramic material.

[0007] The composite membrane provided by this invention has an inner passivation layer made of oxide, which mainly provides strong metallurgical and chemical bonding with the substrate and acts as the first physical barrier to prevent direct contact between liquid metal and the substrate. The intermediate barrier layer is made of amorphous material, which utilizes the characteristic of amorphous structure without grain boundaries to completely block the rapid diffusion path of liquid metal atoms (such as Pb, Bi, Li) along the grain boundaries, thereby improving the anti-permeability of the composite membrane. The outer functional layer is made of ceramic material that is in direct contact with the liquid metal. It has an extremely low dissolution rate and reactivity. When the membrane is partially damaged due to mechanical damage or other reasons, trace amounts of oxygen in the environment will preferentially react with the exposed intermediate or inner layer elements at the damaged site to generate new protective oxides, achieving self-healing and preventing corrosion from developing vertically.

[0008] Preferably, the oxide is selected from at least one of chromium oxide or aluminum oxide; The thickness of the inner passivation layer is 0.5~2μm.

[0009] Preferably, the amorphous material is selected from at least one of amorphous silicon nitride, amorphous carbon, or amorphous boron nitride; The thickness of the intermediate barrier layer is 0.2~1μm.

[0010] Preferably, the ceramic material is selected from at least one of yttrium oxide, erbium oxide, or zirconium oxide; The thickness of the outer functional layer is 1~5μm.

[0011] Preferably, the metal substrate is selected from austenitic steel, ferritic steel or martensitic steel.

[0012] According to a second aspect of the present invention, a high-temperature resistant and corrosion-resistant composite film layer for use in liquid metal environments is provided, comprising the following steps: Step 1: Pre-treat the surface of the metal substrate to obtain a clean metal substrate; Step 2: Form an inner passivation layer on the surface of the metal substrate using thermal oxidation or a deposition-combined oxidation method; Step 3: Deposit an intermediate barrier layer on the surface of the inner passivation layer using plasma-enhanced chemical vapor deposition or reactive magnetron sputtering. Step 4: Deposit an outer functional layer on the surface of the intermediate barrier layer using pulsed laser deposition or reactive magnetron sputtering techniques; Step 5: Perform low-temperature annealing under an inert atmosphere or vacuum to obtain the composite film layer.

[0013] Preferably, in step 1, the pretreatment includes polishing, ultrasonic cleaning, and degreasing.

[0014] Preferably, in step 2, the specific steps of the thermal oxidation method are as follows: under an inert atmosphere with controllable oxygen partial pressure, heat treatment is performed at 600~800℃ for 1~5h to obtain the inner passivation layer; The specific steps of the deposition-oxidation method are as follows: a pure chromium or pure aluminum film is deposited on the surface of the metal substrate using magnetron sputtering technology, and then oxidized at 500~700℃ to obtain the inner passivation layer.

[0015] The inner passivation layer is prepared by thermal oxidation or a combination of deposition and oxidation. In the thermal oxidation process, the controllable oxygen partial pressure parameter is 10. -20 ~10 -15 atm, thereby forming a Cr2O3 layer or Al2O3 layer on the surface of the metal substrate.

[0016] In the deposition-oxidation method, a pure Cr or pure Al film with a thickness of 1 μm is first deposited on the surface of the metal substrate. Then, the oxidation treatment temperature can be reduced to form a Cr2O3 layer or an Al2O3 layer.

[0017] Preferably, in step 3, the parameters of the plasma-enhanced chemical vapor deposition are: a SiH4 / NH3 mixed gas of 1:2 to 1:10, with a SiH4 flow rate of 10 to 40 sccm; or CH4 gas, with a CH4 flow rate of 10 to 40 sccm, a power density of 0.08 to 0.35 W / cm², a working pressure of 400 to 1000 mTorr, and a substrate temperature of 200 to 400 °C. The parameters for the reactive magnetron sputtering technology are: vacuum level of 1×10⁻⁶. -4 ~5×10 -4 Pa, Ar gas is introduced, sputtering pressure is 0.1~1.0 Pa, sputtering power is 100~500 W, and substrate temperature is 200~400℃.

[0018] This invention uses plasma-enhanced chemical vapor deposition or reactive magnetron sputtering to deposit an intermediate barrier layer on the surface of an inner passivation layer. By precisely controlling the condition parameters, an amorphous, dense film with controllable internal stress can be formed.

[0019] Preferably, in step 4, the parameters of the pulsed laser deposition are: oxygen partial pressure of 1~200mTorr, pulse frequency of 2~10Hz, target-substrate distance of 40~80mm, and substrate temperature of 200~400℃. The parameters of the reactive magnetron sputtering technology are: Ar / O2 flow ratio of 1:2~20, working pressure of 1~70mTorr, and substrate temperature of 200~400℃.

[0020] In this invention, an outer functional layer is deposited using pulsed laser deposition or reactive magnetron sputtering. By controlling the deposition rate and substrate temperature, a nanocrystalline structure and a functional layer with good adhesion can be obtained.

[0021] Preferably, in step 5, the low-temperature annealing treatment is performed at a temperature of 500~700℃ for 1~2 hours.

[0022] Finally, the invention employs low-temperature annealing to release internal stress in the film layer, enhance interlayer bonding, and thereby improve the overall density of the composite film layer. Beneficial effects

[0023] This invention provides a high-temperature resistant and corrosion-resistant composite film for liquid metal environments and its preparation method. It has the following beneficial effects: This solution provides a high-temperature resistant and corrosion-resistant composite film for liquid metal environments. It uses an oxide passivation layer to ensure adhesion, an amorphous barrier layer to block diffusion, and a ceramic material functional layer to provide stability and self-healing properties. Through the synergistic effect of the three layers, it protects structural materials that come into contact with liquid metal, extends equipment life, and improves system safety and economy. It solves the problems of poor protection and performance degradation that exist in traditional single coatings.

[0024] This solution provides a high-temperature resistant and corrosion-resistant composite film for liquid metal environments. The intermediate barrier layer is an amorphous material layer that can fundamentally eliminate rapid diffusion channels such as grain boundaries, greatly delaying the penetration and corrosion of liquid metal. Combined with the outer stable ceramic layer, it effectively resists the dissolution and erosion of liquid metal.

[0025] This solution provides a high-temperature resistant and corrosion-resistant composite membrane for liquid metal environments. The outer functional layer also has self-healing capabilities, enabling the composite membrane to repair localized damage and improving its long-term reliability and service life.

[0026] This solution provides a method for preparing a high-temperature resistant and corrosion-resistant composite film for liquid metal environments. It adopts mature processes such as PECVD, magnetron sputtering, and PLD. By controlling the process conditions and parameters, a composite film with suitable thickness, composition, and structure can be obtained, which is easy to achieve large-scale production. Detailed Implementation

[0027] To better illustrate the content of this invention, the following description is provided in conjunction with specific embodiments. Example

[0028] This invention uses 316 stainless steel as a substrate and grows a high-temperature resistant and corrosion-resistant composite film for liquid metal environments on its surface. The specific preparation method is as follows: Step 1: Use water-based SiC sandpaper to polish the surface of the 316 stainless steel substrate to remove the surface oxide film and make the substrate surface have a certain roughness. Then use water-based diamond polishing paste to polish the substrate surface. Then use an ultrasonic cleaner, add acetone, alcohol and deionized water in sequence to ultrasonically vibrate for 10 minutes to clean and degrease, and obtain a clean 316 stainless steel substrate. Step 2, with a controllable oxygen partial pressure of 10⁻¹ 5 In an Ar atmosphere at M, a 316 stainless steel substrate is heat-treated at 600℃ for 2 hours to generate a chromium oxide layer with a thickness of 0.5μm on the surface of the 316 stainless steel substrate, forming an inner passivation layer. Step 3: Using plasma-enhanced chemical vapor deposition (PECVD), the flow rate of SiH4 is controlled at 10 sccm, the flow rate of NH3 is controlled at 20 sccm, the power density is 0.08 W / cm², the working pressure is 400 mTorr, and the substrate temperature is 200℃. An amorphous silicon nitride layer with a thickness of 0.2~0.5 μm is deposited on the surface of the inner passivation layer to form an intermediate barrier layer. Step 4: Using pulsed laser deposition technology, the oxygen partial pressure is controlled at 20 mTorr, the pulse frequency is 2 Hz, yttrium oxide is used as the target, the target-substrate distance is 40 mm, the substrate temperature is 200 ℃, and a yttrium oxide layer with a thickness of 1 μm is deposited on the surface of the intermediate barrier layer to form the outer functional layer. Step 5: Under an inert atmosphere, the deposited composite film is annealed at 500℃ for 1 hour to obtain a dense high-temperature resistant and corrosion-resistant composite film. Example

[0029] The preparation method of this embodiment is the same as that of Example 1. The difference is that in step 2, a pure Cr layer with a thickness of 1 μm is first deposited on the surface of the metal substrate using magnetron sputtering technology, and then oxidized at 500°C to generate a chromium oxide layer with a thickness of 0.5 μm on the surface of the 316 stainless steel substrate, forming an inner passivation layer. Example

[0030] The preparation method of this embodiment is the same as that of Example 1. The difference is that in step 2, a pure Al layer with a thickness of 1 μm is first deposited on the surface of the metal substrate using magnetron sputtering technology, and then oxidized at 500°C to generate an aluminum oxide layer with a thickness of 0.5 μm on the surface of the 316 stainless steel substrate, forming an inner passivation layer. Example

[0031] The preparation method in this embodiment is the same as that in Example 1, except that in step 3, reactive magnetron sputtering technology is used to control the vacuum degree to 5×10⁻ 4Under conditions of Pa, Ar gas is introduced, sputtering pressure is 1:2, sputtering power is 200W, and substrate temperature is 200℃, an amorphous silicon nitride layer with a thickness of 0.5μm is deposited on the surface of the inner passivation layer to form an intermediate barrier layer. Example

[0032] The preparation method of this embodiment is the same as that of Example 1. The difference is that in step 4, reactive magnetron sputtering technology is used, the Ar / O2 flow ratio is 1:2, the working pressure is 20 mTorr, the substrate temperature is 200°C, and a yttrium oxide layer with a thickness of 1 micrometer is deposited on the surface of the intermediate barrier layer to form the outer functional layer.

[0033] Comparative Example 1 The preparation method of Comparative Example 1 is the same as that of Example 1, except that an amorphous silicon nitride layer is deposited directly on the clean surface of a 316 stainless steel substrate using plasma-enhanced chemical vapor deposition, omitting the preparation of the inner passivation layer.

[0034] Comparative Example 2 The preparation method of this comparative example is the same as that of Example 1, except that step 4 is prepared directly on the surface of the inner passivation layer prepared in step 2, and the preparation of the intermediate barrier layer is omitted.

[0035] Comparative Example 3 The preparation method of this comparative example is the same as that of Example 1, except that the step of depositing and preparing the outer functional layer in step 4 is omitted, and the outer functional layer is omitted.

[0036] The composite films prepared according to Examples 1 to 5 and Comparative Examples 1 to 3 were tested for resistance to liquid metal corrosion and long-term stability, as shown in Table 1.

[0037]

[0038] Based on the data in Table 1, the comprehensive analysis is as follows: 1. The necessity of a three-layer structure design As can be seen from the comparison between Comparative Examples 1-3 and Example 1, the synergistic effect of the three-layer structure (inner passivation layer + middle amorphous barrier layer + outer functional layer) is the key to achieving excellent protective performance.

[0039] Comparative Example 1 omitted the inner passivation layer, directly depositing an amorphous silicon nitride interlayer onto the stainless steel substrate surface. Due to the significant difference in thermal expansion coefficients between silicon nitride and the metal substrate, and the lack of a gradient transition in chemical composition, the film adhesion decreased significantly (<8 N). In liquid metal corrosion tests, the film exhibited large-area peeling, with a mass loss exceeding 5.0 mg / cm², demonstrating extremely poor long-term stability. This indicates that the inner passivation layer is crucial for achieving a strong bond between the film and the substrate.

[0040] Comparative Example 2 omitted the intermediate amorphous barrier layer, consisting only of an inner layer of chromium oxide and an outer layer of yttrium oxide. Although the adhesion was good (>32 N), the presence of numerous grain boundaries due to the polycrystalline structure of both chromium oxide and yttrium oxide led to severe intergranular corrosion as liquid metal atoms rapidly diffused inward along these boundaries, resulting in a mass loss exceeding 10.0 mg / cm². This demonstrates that the intermediate amorphous layer's function of completely blocking diffusion channels through its grain-bound structure is irreplaceable.

[0041] Comparative Example 3 omitted the outer functional layer and consisted of an inner chromium oxide layer and an intermediate silicon nitride layer. Although the adhesion was excellent (>33 N) and the intermediate layer effectively blocked grain boundary diffusion, the silicon nitride was directly exposed to the liquid metal environment, resulting in a chemical reaction that led to surface dissolution, thinning of the film thickness, surface roughening, and poor long-term stability. This indicates that the outer high chemical stability ceramic layer plays an important role in resisting direct corrosion from liquid metal.

[0042] 2. Comparison of the effects of different preparation processes Example 1 describes a three-layer structure prepared by thermal oxidation, consisting of an inner layer of chromium oxide, amorphous silicon nitride deposited by PECVD, and yttrium oxide deposited by PLD. The three layers are intact and the processes are well-matched. Test results show that this sample exhibits the best performance across all indicators: optimal resistance to liquid metal corrosion (mass loss <0.1 mg / cm²), highest adhesion (>35 N), and excellent long-term stability (film intact after 1000 h). This is attributed to the metallurgical bonding between the thermally oxidized inner layer and the substrate, the dense structure of the PECVD amorphous layer, and the precise stoichiometry and self-healing ability of the PLD outer layer.

[0043] Examples 2 and 3 employed a "deposition of pure metal + low-temperature oxidation" method to prepare the inner passivation layer (chromium oxide and aluminum oxide). This process, with its low temperature (500°C), has minimal thermal impact on the substrate, resulting in a dense oxide layer. Test results showed that both methods exhibited good corrosion resistance (approximately 0.2 mg / cm² mass loss). While their adhesion (26-28 N) was slightly inferior to the thermal oxidation method, it still met the application requirements and could serve as an alternative for scenarios sensitive to substrate thermal budgets.

[0044] Example 4 uses reactive magnetron sputtering to prepare an intermediate silicon nitride layer. The film has high density and good blocking effect. However, the high energy of the sputtered particles introduces certain internal stress, and the adhesion (27 N) is slightly lower than that of the sample prepared by PECVD. The long-term stability is still within the good range.

[0045] Example 5 uses reactive magnetron sputtering to prepare an outer yttrium oxide layer. The film has good density, but because the self-healing ability of the sputtered film is slightly inferior to that of the PLD film, the corrosion resistance (mass loss of 0.3 mg / cm²) is slightly lower than that of Example 1, but it is still significantly better than the comparative example without an outer layer.

[0046] In summary, the three-layer composite membrane structure of this invention is rationally designed, with each layer having a clearly defined function and synergistic effect. Example 1, as the preferred embodiment, exhibits the best overall performance in terms of resistance to liquid metal corrosion, adhesion, and long-term stability, fully verifying the advanced nature and feasibility of the technical solution of this invention. The failure modes of the comparative examples also demonstrate, from the opposite perspective, the technical necessity that the three-layer structure is indispensable.

[0047] 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 high temperature resistant corrosion protection composite film layer for liquid metal environment, characterized in that: It includes an inner passivation layer, an intermediate barrier layer, and an outer functional layer that are sequentially fixed to the surface of a metal substrate. The inner passivation layer is an oxide; The intermediate barrier layer is an amorphous material; The outer functional layer is made of ceramic material.

2. The high temperature resistant anti-corrosion composite film layer for liquid metal environment according to claim 1, characterized in that: The oxide is selected from at least one of chromium oxide or aluminum oxide; The thickness of the inner passivation layer is 0.5~2μm.

3. The high temperature resistant anti-corrosion composite film layer for liquid metal environment according to claim 1, characterized in that: The amorphous material is selected from at least one of amorphous silicon nitride, amorphous carbon, or amorphous boron nitride. The thickness of the intermediate barrier layer is 0.2~1μm.

4. The high-temperature resistant and corrosion-resistant composite film layer for liquid metal environments according to claim 1, characterized in that: The ceramic material is selected from at least one of yttrium oxide, erbium oxide, or zirconium oxide; The thickness of the outer functional layer is 1~5μm.

5. The high-temperature resistant and corrosion-resistant composite film layer for liquid metal environments according to claim 1, characterized in that: The metal substrate is selected from austenitic steel, ferritic steel or martensitic steel.

6. A method for preparing a high-temperature resistant and corrosion-resistant composite film for liquid metal environments as described in any one of claims 1 to 5, characterized in that: Includes the following steps: Step 1: Pre-treat the surface of the metal substrate to obtain a clean metal substrate; Step 2: Form an inner passivation layer on the surface of the metal substrate using thermal oxidation or a deposition-combined oxidation method; Step 3: Deposit an intermediate barrier layer on the surface of the inner passivation layer using plasma-enhanced chemical vapor deposition or reactive magnetron sputtering. Step 4: Deposit an outer functional layer on the surface of the intermediate barrier layer using pulsed laser deposition or reactive magnetron sputtering techniques; Step 5: Perform low-temperature annealing under an inert atmosphere or vacuum to obtain the composite film.

7. The method for preparing a high-temperature resistant and corrosion-resistant composite film for liquid metal environments according to claim 6, characterized in that: In step 2, the specific steps of the thermal oxidation method are as follows: under an inert atmosphere with controllable oxygen partial pressure, heat treatment is carried out at 600~800℃ for 1~5h to obtain the inner passivation layer; The specific steps of the deposition-oxidation method are as follows: a pure chromium or pure aluminum film is deposited on the surface of the metal substrate using magnetron sputtering technology, and then oxidized at 500~700℃ to obtain the inner passivation layer.

8. The method for preparing a high-temperature resistant and corrosion-resistant composite film for liquid metal environments according to claim 6, characterized in that: In step 3, the parameters for plasma-enhanced chemical vapor deposition are: a SiH4 / NH3 mixed gas of 1:2 to 1:10, with a SiH4 flow rate of 10 to 40 sccm; or CH4 gas, with a CH4 flow rate of 10 to 40 sccm, a power density of 0.08 to 0.35 W / cm², an operating pressure of 400 to 1000 mTorr, and a substrate temperature of 200 to 400 °C. The parameters of the reaction magnetron sputtering technology are as follows: vacuum degree is 1x10 -4 -4 Pa, Ar gas is introduced, sputtering pressure is 0.1~1.0 Pa, sputtering power is 100~500 W, and substrate temperature is 200~400℃.​ 9. The method for preparing a high-temperature resistant and corrosion-resistant composite film for liquid metal environments according to claim 6, characterized in that: In step 4, the parameters for pulsed laser deposition are: oxygen partial pressure of 1~200 mTorr, pulse frequency of 2~10 Hz, target-substrate distance of 40~80 mm, and substrate temperature of 200~400 °C. The parameters of the reactive magnetron sputtering technology are: Ar / O2 flow ratio of 1:2 to 1:20, working pressure of 1 to 70 mTorr, and substrate temperature of 200 to 400 °C.

10. The method for preparing a high-temperature resistant and corrosion-resistant composite film for liquid metal environments according to claim 6, characterized in that: In step 5, the low-temperature annealing treatment is performed at a temperature of 500~700℃ for 1~2 hours.

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