A corrosion-resistant hydrogen-resistant coating for an inner wall of a stainless steel armoured layer
By constructing a composite coating system consisting of a metal bonding layer, a transition layer, a MAX phase ceramic layer, an oxide interface barrier layer, and an amorphous or nanocrystalline dense shell layer on the inner wall of the stainless steel armor layer, the problems of weak bonding, insufficient density, and difficulty in uniform forming of existing coatings are solved, thus achieving coating applications with high-efficiency protection and long service life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANDONG PACIFIC POWER COMM EQUIP CO LTD
- Filing Date
- 2026-02-27
- Publication Date
- 2026-06-05
AI Technical Summary
Existing stainless steel armor layers are susceptible to hydrogen embrittlement and media corrosion in high-temperature, high-pressure, and corrosive environments. Existing coatings are not firmly bonded and lack density, making it difficult to form uniformly on complex curved surfaces. Furthermore, the interface matching problem has not been effectively solved.
A composite coating system consisting of a gradient transition-in-situ conversion-surface strengthening process chain is constructed, comprising a metal bonding layer, a transition layer, a MAX phase ceramic layer, an oxide interface barrier layer, and an amorphous or nanocrystalline dense shell. Through techniques such as magnetron sputtering, oxidation treatment, and low-energy ion implantation, uniform deposition and strong bonding of the coating on the inner wall of stainless steel are achieved.
It achieves stable bonding between the coating and the substrate, improves the density and hydrogen permeability resistance of the coating, extends the service life of the stainless steel armor layer, and is suitable for the preparation of high-quality coatings for complex curved inner walls, meeting the needs of hydrogen energy storage and transportation, nuclear power and optical cable manufacturing.
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to the field of metal surface protection technology, and in particular to a corrosion-resistant and hydrogen-resistant coating for the inner wall of a stainless steel armor layer. Background Technology
[0002] Currently, in the fields of hydrogen energy storage and transportation, nuclear power, chemical industry, and long-distance communication optical cables, stainless steel armor layers are core components that withstand pressure and transport critical media such as high-pressure hydrogen, high-temperature coolants, or protect core optical units. However, in long-term high-temperature, high-pressure, and corrosive environments, the metal substrate faces the dual threats of hydrogen embrittlement induced by hydrogen atom penetration and direct corrosion by the medium, seriously endangering equipment safety and lifespan. Surface coating technology is the main means to improve its durability, but existing technical solutions have significant bottlenecks in both protective effectiveness and engineering applicability.
[0003] Protective coatings widely used in industrial applications mainly fall into two categories. The first category is traditional ceramic coatings, such as alumina and silica coatings prepared by thermal spraying or sol-gel methods. Although these coatings have high hardness, their structure often contains micropores and cracks, resulting in insufficient density. More importantly, their coefficient of thermal expansion differs greatly from that of the stainless steel substrate. Under the thermal cycling or high-pressure fluctuations generated during equipment start-up and shutdown, high stress is easily generated inside the coating, leading to the propagation of macroscopic cracks and even large-area peeling. Once the integrity of the coating is lost, its protective function fails, the exposed substrate will corrode more rapidly, and the cracks will become rapid channels for corrosive media and hydrogen atoms to seep into the substrate.
[0004] To find better solutions, research has shifted its focus to ternary layered carbonitride (MAX) phase materials, such as Ti2AlC, which combine metallic and ceramic properties. However, existing technologies for preparing MAX phase coatings still face significant challenges. For example, patent CN114717516B describes the preparation of TiAl / Ti2AlC coatings using arc or thermal spraying techniques. While these high-energy beam processes can achieve rapid deposition, they struggle to achieve uniform thickness and composition coverage on complex curved surfaces such as pipe and sleeve inner walls. Furthermore, microscopic defects such as pores and oxide inclusions are inevitably introduced into the coating. These defects directly compromise the coating's density, becoming weak points in the protective system. In addition, the MAX phase ceramic layer and the metal substrate form a "hard bond" with vastly different physicochemical properties, lacking an effective transition and strong bonding mechanism. Existing technologies have failed to address this interface matching problem, leading to easy delamination of the coating at the interface under thermal or hydrogen-induced stress, resulting in overall failure.
[0005] Therefore, developing a MAX phase-based composite coating system that can be uniformly formed on the inner wall, achieve strong and tough interfacial bonding, and is dense and defect-free has become a technical challenge that urgently needs to be overcome in this field. Summary of the Invention
[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a corrosion-resistant and hydrogen-resistant coating for the inner wall of a stainless steel armor layer.
[0007] To achieve the above objectives, the present invention adopts the following technical solution: A corrosion-resistant and hydrogen-proof coating for the inner wall of a stainless steel armor layer, the coating comprising, from the inside to the outside, a metal bonding layer, a transition layer, a MAX phase ceramic layer, an oxide interface barrier layer, and an amorphous or nanocrystalline dense shell layer on the surface of the stainless steel armor layer substrate; the metal bonding layer is a Cr layer or a NiCr alloy layer with a thickness of 100~500nm; the transition layer is a Ti or Al transition layer with a thickness of 20~100nm; the MAX phase ceramic layer is a Ti2AlC or Ti2AlN layer with a thickness of 1.5~3.0μm; the oxide interface barrier layer is mainly composed of α-Al2O3 with a thickness of 50~300nm; and the amorphous or nanocrystalline dense shell layer has a thickness of 20~80nm.
[0008] Preferably, the MAX phase ceramic layer is deposited in situ on the surface of the transition layer using mid-frequency magnetron sputtering technology. During deposition, the substrate temperature is controlled at 700~800℃, pure argon is used as the working gas, and the background vacuum level of the vacuum chamber does not exceed 5.0×10⁻⁶. - ³Pa, working air pressure is 0.3~0.8Pa.
[0009] Preferably, the oxide interface barrier layer is generated in situ through a medium-temperature controlled oxidation treatment of the MAX phase ceramic layer; the atmosphere for the medium-temperature controlled oxidation treatment is flowing dry air or a nitrogen-oxygen mixture with an oxygen volume fraction of 10-50%, the oxidation treatment temperature is controlled at 680-720℃, and the holding time is 2-4 hours. The oxidation treatment temperature is selected within a window that is lower than the significant decomposition temperature of MAX phase materials such as Ti2AlC, but sufficient to promote the selective diffusion oxidation of Al.
[0010] Preferably, the amorphous or nanocrystalline dense shell is formed by low-energy ion implantation treatment of the oxide interface barrier layer surface, followed by low-temperature annealing at a temperature of 100-150°C and a holding time of 1-2 hours; the implanted ions in the low-energy ion implantation treatment are nitrogen ions, the implantation energy is 15-35 keV, and the implantation dose is 5×10¹ 6 ~1×10¹ 8 ions / cm².
[0011] Preferably, the substrate material of the stainless steel armor layer is 304 stainless steel, 316L stainless steel or duplex stainless steel, and the inner diameter of the armor layer is 5~100mm.
[0012] A method for preparing a corrosion-resistant and hydrogen-resistant coating includes the following steps: S1. Pretreatment: The inner wall of the stainless steel armor layer is sequentially cleaned and activated pretreatment; S2. Deposition of metal bonding layer, transition layer and MAX phase ceramic layer: The pretreated workpiece is placed in a magnetron sputtering equipment, and the vacuum chamber background vacuum level is evacuated to no higher than 5.0 × 10⁻⁶. - After ³Pa, the substrate is heated to 300~500℃, argon gas is introduced, and a Cr target or NiCr target is sputtered first to deposit a metal bonding layer with a thickness of 100~500nm on the inner wall of the stainless steel armor layer; then a Ti target or Al target is sputtered to deposit a transition layer with a thickness of 20~100nm on the metal bonding layer; then the substrate temperature is raised to 700~800℃, and a Ti-Al-C or Ti-Al-N composite target is sputtered using a medium frequency power supply to deposit a dense Ti2AlC or Ti2AlN ceramic layer on the transition layer. During the deposition process, the uniformity of the coating on the inner wall of the stainless steel armor layer must be ensured. S3. Oxidation treatment: The workpiece with the deposited MAX phase ceramic layer is placed in an oxidation furnace and kept at 680-720℃ for 2-4 hours in a flowing dry air or nitrogen-oxygen mixture atmosphere with oxygen volume fraction of 10-50%. Then it is cooled with the furnace to form a dense α-Al2O3 oxide interface barrier layer in situ. S4. Ion Implantation and Post-treatment: The oxidized workpiece is placed in an ion implantation device, and nitrogen ions with an energy of 15~35keV are implanted at a dose of 5×10¹. 6 ~1×10¹ 8 ions / cm²; After injection, the workpiece is subjected to low-temperature annealing treatment at a temperature of 100~150℃ for 1~2h, and then sealed in an oxygen-free environment to obtain the corrosion-resistant and hydrogen-proof coating.
[0013] Preferably, in step S1, the cleaning and activation pretreatment includes sequential alkaline washing for degreasing, acid washing for activation, ultrasonic cleaning, and finally vacuum drying.
[0014] Preferably, in step S2, the method for ensuring the uniformity of the coating on the inner wall of the stainless steel armor layer is workpiece rotation or planetary revolution.
[0015] The core principle of this invention lies in constructing a composite coating system with strong interfacial bonding, intrinsic density, and surface passivation through a synergistic process chain of "gradient transition - in-situ transformation - surface strengthening." First, in the deposition stage, a metal bonding layer (Cr / NiCr) and an active transition layer (Ti / Al) are sequentially constructed via magnetron sputtering. During the subsequent high-temperature deposition of the MAX phase, the transition layer undergoes interdiffusion and interfacial reactions with the sputtered atoms, forming a chemical diffusion transition zone with gradually changing composition and properties. This effectively alleviates the stress caused by the mismatch in thermal expansion coefficients, achieving a high-strength bond between the ceramic layer and the metal substrate. Second, in the oxidation treatment stage, the temperature is strictly controlled within a window of 680~720℃. This temperature utilizes the selective oxidation characteristics of Al in the MAX phase, promoting the preferential diffusion of Al atoms to the surface, resulting in the in-situ growth of a continuous, dense, and thermodynamically stable α-Al₂O₃ thin film. This layer not only seals the microscopic defects on the ceramic surface but also constructs a chemical barrier layer with an extremely high hydrogen diffusion barrier. Finally, in the surface strengthening stage, nitrogen atoms are introduced into the α-Al₂O₃ surface layer through low-energy nitrogen ion implantation, causing lattice distortion and amorphization, forming a nitrogen-doped strengthening layer rich in high dislocation density. This process also introduces a residual compressive stress field, which can effectively suppress the initiation of surface microcracks. The high-density grain boundaries and dislocations formed by implantation can act as effective hydrogen traps, fixing hydrogen atoms. Subsequent low-temperature annealing is used to optimize the defect structure and stabilize the compressive stress state, ultimately obtaining a dense shell layer on the outermost layer of the coating that combines high hardness, high density, and excellent resistance to hydrogen-induced cracking.
[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention employs a composite structure design that sequentially deposits a metal bonding layer, a transition layer, and a MAX phase ceramic layer, combined with an α-Al2O3 oxide interface barrier layer and an amorphous or nanocrystalline dense shell layer. By combining the synergistic mechanism of each layer, it solves the technical problems of weak bonding and easy peeling of existing coatings with stainless steel substrates, and achieves stable bonding between the coating and the substrate, providing a foundation for the coating to perform its protective function.
[0017] 2. This invention employs an in-situ deposition process for MAX phase ceramic layers, combined with a medium-temperature controlled oxidation treatment of the MAX phase ceramic layers to generate an α-Al2O3 oxide interface barrier layer. By utilizing the dense characteristics of the MAX phase ceramic layers and the hydrogen diffusion barrier mechanism of α-Al2O3, this invention solves the problems of insufficient density, poor hydrogen permeation resistance, and poor corrosion resistance of existing coatings. It can effectively block hydrogen atom penetration, improve corrosion resistance, and extend the service life of stainless steel armor layers.
[0018] 3. This invention employs low-energy ion implantation and low-temperature annealing of the oxide interface barrier layer, combined with the surface strengthening mechanism of the amorphous or nanocrystalline dense shell, to solve the problems of insufficient surface hardness, easy generation of microcracks, and surface porosity affecting the protective effect of existing coatings. It can effectively improve the surface hardness of the coating, seal the surface porosity, and further enhance the coating's corrosion resistance and hydrogen permeation prevention capabilities.
[0019] 4. This invention employs medium-frequency magnetron sputtering technology to deposit various functional layers, and uses workpiece rotation or planetary revolution to ensure coating uniformity. Combined with the synergistic process chain mechanism of gradient transition, in-situ transformation, and surface strengthening of each layer, it solves the engineering applicability problem of existing coatings being difficult to uniformly form on the inner wall of stainless steel armor layers (especially complex curved surfaces with different inner diameters). It successfully achieves high-quality coating preparation on the inner wall of slender stainless steel tubes (inner diameter 5~100mm) for optical cables, adapting to the actual application needs in the fields of hydrogen energy storage and transportation, nuclear power, chemical industry, and optical cable manufacturing. Detailed Implementation
[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.
[0021] Example 1: This example addresses the stainless steel armor layer for communication optical cables requiring high corrosion and hydrogen resistance. The corrosion-resistant and hydrogen-resistant coating, from the inside to the outside of the stainless steel armor layer substrate, consists of a metal bonding layer, a transition layer, a MAX phase ceramic layer, an oxide interface barrier layer, and an amorphous or nanocrystalline dense shell layer. Specific parameters for each layer are as follows: Metal bonding layer: Cr layer with a thickness of 100nm; Transition layer: A Ti transition layer with a thickness of 20nm is used; MAX phase ceramic layer: Ti2AlC layer with a thickness of 1.5μm; Oxide interface barrier layer: The main component is α-Al2O3, and the thickness is 50nm; Amorphous or nanocrystalline dense shell: 20 nm thick; Stainless steel armor layer substrate: made of 304 stainless steel, with an inner diameter of 5mm.
[0022] The method for preparing the above-mentioned corrosion-resistant and hydrogen-resistant coating includes the following steps: S1. Pretreatment: The inner wall of the 304 stainless steel armor layer is subjected to alkaline washing to remove oil, acid washing to activate, ultrasonic cleaning, and finally vacuum drying to complete the cleaning and activation pretreatment. S2. Deposition of metal bonding layer, transition layer and MAX phase ceramic layer: The pretreated workpiece is placed in a magnetron sputtering apparatus, and the vacuum chamber is evacuated to a background vacuum of 5.0 × 10⁻⁶. -The substrate was heated to 300°C, and then pure argon was introduced as the working gas. First, a Cr target was sputtered to deposit a 100 nm thick Cr metal bonding layer on the inner wall of the stainless steel armor layer. Then, a Ti target was sputtered to deposit a 20 nm thick Ti transition layer on the metal bonding layer. The substrate temperature was then raised to 700°C, and a Ti-Al-C composite target was sputtered using a medium-frequency power supply to deposit a dense Ti2AlC ceramic layer on the transition layer. During the deposition process, the uniformity of the coating on the inner wall of the stainless steel armor layer was ensured by rotating the workpiece. The deposition working gas pressure was 0.3 Pa. S3. Oxidation treatment: The workpiece with the deposited Ti2AlC ceramic layer is placed in an oxidation furnace and held at 680℃ for 2 hours in a nitrogen-oxygen mixed atmosphere with 10% oxygen volume fraction. Then it is cooled with the furnace to generate a dense α-Al2O3 oxide interface barrier layer in situ. S4. Ion Implantation and Post-treatment: The oxidized workpiece is placed in an ion implantation device, and nitrogen ions with an energy of 15 keV are implanted at a dose of 5 × 10¹. 6 ions / cm²; After injection, the workpiece is subjected to low-temperature annealing treatment. Under vacuum, the annealing temperature is 100℃ and the holding time is 1h. Then, it is sealed in an oxygen-free environment to obtain the corrosion-resistant and hydrogen-proof coating.
[0023] Example 2: This example addresses the stainless steel armor layer for communication optical cables requiring high corrosion and hydrogen resistance. The corrosion-resistant and hydrogen-resistant coating, from the inside to the outside of the stainless steel armor layer substrate, consists of a metal bonding layer, a transition layer, a MAX phase ceramic layer, an oxide interface barrier layer, and an amorphous or nanocrystalline dense shell layer. Specific parameters for each layer are as follows: Metal bonding layer: NiCr alloy layer with a thickness of 300nm; Transition layer: An Al transition layer with a thickness of 60 nm is used; MAX phase ceramic layer: Ti2AlN layer with a thickness of 2.2μm; Oxide interface barrier layer: The main component is α-Al2O3, and the thickness is 175nm; Amorphous or nanocrystalline dense shell: 50nm thick; Stainless steel armor layer substrate: Made of 316L stainless steel, with an inner diameter of 52mm.
[0024] The method for preparing the above-mentioned corrosion-resistant and hydrogen-resistant coating includes the following steps: S1. Pretreatment: The inner wall of the 316L stainless steel armor layer is subjected to alkaline washing for degreasing, acid washing for activation, ultrasonic cleaning, and finally vacuum drying to complete the cleaning and activation pretreatment. S2. Deposition of metal bonding layer, transition layer and MAX phase ceramic layer: The pretreated workpiece is placed in a magnetron sputtering apparatus, and the vacuum chamber is evacuated to a background vacuum of 3.0 × 10⁻⁶. - The substrate was heated to 400°C, and pure argon was introduced as the working gas. First, a NiCr target was sputtered to deposit a NiCr alloy metal bonding layer with a thickness of 300 nm on the inner wall of the stainless steel armor layer. Then, an Al target was sputtered to deposit an Al transition layer with a thickness of 60 nm on the metal bonding layer. The substrate temperature was then raised to 750°C, and a Ti-Al-N composite target was sputtered using a medium-frequency power supply to deposit a dense Ti2AlN ceramic layer on the transition layer. During the deposition process, planetary revolution was used to ensure the uniformity of the coating on the inner wall of the stainless steel armor layer. The deposition working gas pressure was 0.55 Pa. S3. Oxidation treatment: The workpiece with the deposited Ti2AlN ceramic layer is placed in an oxidation furnace and held at 700℃ for 3 hours in a nitrogen-oxygen mixed atmosphere with an oxygen volume fraction of 30%. Then it is cooled with the furnace to generate a dense α-Al2O3 oxide interface barrier layer in situ. S4. Ion Implantation and Post-treatment: The oxidized workpiece is placed in an ion implantation device, and nitrogen ions with an energy of 25 keV are implanted at a dose of 5.25 × 10¹. 7 ions / cm²; After injection, the workpiece is subjected to low-temperature annealing treatment. Under vacuum, the annealing temperature is 125℃ and the holding time is 1.5h. Then, it is sealed in an oxygen-free environment to obtain the corrosion-resistant and hydrogen-proof coating.
[0025] Example 3: This example addresses the stainless steel armor layer for communication optical cables requiring high corrosion and hydrogen resistance. The corrosion-resistant and hydrogen-resistant coating, from the inside to the outside of the stainless steel armor layer substrate, consists of a metal bonding layer, a transition layer, a MAX phase ceramic layer, an oxide interface barrier layer, and an amorphous or nanocrystalline dense shell layer. Specific parameters for each layer are as follows: Metal bonding layer: NiCr alloy layer with a thickness of 500nm; Transition layer: An Al transition layer with a thickness of 100 nm is used; MAX phase ceramic layer: Ti2AlN layer with a thickness of 3.0 μm; Oxide interface barrier layer: The main component is α-Al2O3, and the thickness is 300nm; Amorphous or nanocrystalline dense shell: 80nm thick; Stainless steel armor layer substrate: made of duplex stainless steel, with an inner diameter of 100mm.
[0026] The method for preparing the above-mentioned corrosion-resistant and hydrogen-resistant coating includes the following steps: S1. Pretreatment: The inner wall of the duplex stainless steel armor layer is sequentially subjected to alkaline washing for degreasing, acid washing for activation, ultrasonic cleaning, and finally vacuum drying to complete the cleaning and activation pretreatment. S2. Deposition of metal bonding layer, transition layer and MAX phase ceramic layer: The pretreated workpiece is placed in a magnetron sputtering apparatus, and the vacuum chamber is evacuated to a background vacuum of 2.0 × 10⁻⁶. - The substrate was heated to 500°C, and pure argon was introduced as the working gas. First, a NiCr target was sputtered to deposit a 500 nm thick NiCr alloy metal bonding layer on the inner wall of the stainless steel armor layer. Then, an Al target was sputtered to deposit a 100 nm thick Al transition layer on the metal bonding layer. The substrate temperature was then raised to 800°C, and a Ti-Al-N composite target was sputtered using a medium-frequency power supply to deposit a dense Ti2AlN ceramic layer on the transition layer. During the deposition process, planetary revolution was used to ensure the uniformity of the coating on the inner wall of the stainless steel armor layer. The deposition working gas pressure was 0.8 Pa. S3. Oxidation treatment: The workpiece with the deposited Ti2AlN ceramic layer is placed in an oxidation furnace and held at 720℃ for 4 hours in a nitrogen-oxygen mixed atmosphere with 50% oxygen volume fraction. Then it is cooled with the furnace to generate a dense α-Al2O3 oxide interface barrier layer in situ. S4. Ion Implantation and Post-treatment: The oxidized workpiece is placed in an ion implantation device, and nitrogen ions with an energy of 35 keV are implanted at a dose of 1 × 10¹. 8 ions / cm²; After injection, the workpiece is subjected to low-temperature annealing treatment. Under vacuum, the annealing temperature is 150℃ and the holding time is 2h. Then, it is sealed in an oxygen-free environment to obtain the corrosion-resistant and hydrogen-proof coating.
[0027] Comparative Example 1: Based on Example 2, the difference is that the step of depositing the metal bonding layer (NiCr alloy layer) in step S2 is omitted, and the rest is the same as Example 2.
[0028] Comparative Example 2: Based on Example 2, the difference is that the process of the Al transition layer in step S2 is omitted, and the rest is the same as Example 2.
[0029] Comparative Example 3: Based on Example 2, the difference is that the oxidation treatment in step S3 is omitted; after completing step S2, the deposited MAX phase ceramic layer (Ti2AlN layer) is directly subjected to ion implantation and post-treatment in step S4. Therefore, there is no α-Al2O3 oxide interface barrier layer in the final coating structure, and the rest is the same as in Example 2.
[0030] Comparative Example 4: Based on Example 2, the difference is that the ion implantation and low-temperature annealing post-treatment in step S4 are omitted; the preparation is completed after the oxidation treatment in step S3, so the final coating surface has no amorphous or nanocrystalline dense shell, and the rest is the same as Example 2.
[0031] Performance testing: The samples prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to the following performance tests, and the test methods are as follows: (1) Interface bonding strength: The scratch method (refer to standard ASTM C1624) was used, with a diamond indenter with a radius of 200 μm. The load was increased linearly from 0 N to 100 N, and the scratch length was 5 mm. The critical load (Lc1) corresponding to the first abrupt change in acoustic emission signal was used to evaluate the bonding strength between the coating and the substrate.
[0032] (2) Surface nanohardness and modulus: A nanoindenter was used, with the maximum indentation depth set at 200 nm, and the continuous stiffness method (CSM) was used for testing. The average value within the indentation depth range of 50-100 nm was taken as the surface nanohardness of the coating.
[0033] (3) Electrochemical corrosion performance: Potentiodynamic polarization tests were conducted in a 3.5 wt.% NaCl solution using a three-electrode electrochemical workstation. The working electrode was the sample to be tested, the reference electrode was a saturated calomel electrode (SCE), and the counter electrode was a platinum sheet. Before testing, the sample was stabilized at the open circuit potential for 30 min, and then scanned from -0.25 V (relative to the open circuit potential) to 1.2 V (vs. SCE) at a rate of 1 mV / s. The self-corrosion current density (i_corr) and the characteristics of the passivation zone were recorded.
[0034] (4) Hydrogen permeation performance: Electrochemical hydrogen permeation (Devanathan-Stachurski double electrolytic cell method) was used. The sample was used as the diaphragm of the double electrolytic cell. One side (cathode side) was charged with hydrogen at a constant current density in 0.2 mol / L NaOH solution; the other side (anode side) was anoly polarized at a constant potential to +0.3V (vs. SCE) in 0.2 mol / L NaOH solution to oxidize the permeated hydrogen atoms, and the change of oxidation current over time was recorded. After the current reached steady state, the steady-state hydrogen permeation flux (J∞), the apparent hydrogen diffusion coefficient (D), and the hydrogen permeation reduction factor (PRF) relative to the bare substrate were calculated and recorded.
[0035] (5) Neutral salt spray test: The corrosion resistance stability of the coating is tested by neutral salt spray test (NSS). The test temperature is 35℃, the salt spray concentration is 5% NaCl, and the spray is continuous. The cumulative test time (unit: h) when obvious corrosion (or substrate corrosion) appears on the coating surface is recorded.
[0036] The test results are as follows: Table 1. Test results for examples and comparative examples. Data Analysis: Analysis of the above data shows that the stainless steel armor inner wall corrosion-resistant and hydrogen-proof coatings prepared in Examples 1-3 all have complete metal bonding layers, transition layers, MAX phase ceramic layers, α-Al2O3 oxide interface barrier layers, and amorphous or nanocrystalline dense shell structures. The synergistic effect of each layer makes the coating exhibit excellent interfacial bonding strength, surface hardness, corrosion resistance and hydrogen permeation prevention performance.
[0037] Compared with Example 2, Comparative Example 1 lacks a metal bonding layer. The metal bonding layer is the basis for the effective bonding between the coating and the substrate. Without it, the coating cannot form a strong bond with the stainless steel substrate, and it peels off during the deposition process, resulting in the failure of the interface bonding strength test. It is impossible to carry out surface nano-hardness and electrochemical corrosion performance tests. Its hydrogen permeation resistance is the same as that of the bare substrate. The substrate rusts quickly in the neutral salt spray test, and the coating completely loses its protective function. This shows that the metal bonding layer is a prerequisite for the coating to adhere to the substrate and play a protective role.
[0038] Compared with Example 2, Comparative Example 2 lacks the Al transition layer. The transition layer can alleviate the interfacial stress between the metal bonding layer and the MAX phase ceramic layer and strengthen the interlayer bonding. After its absence, the interfacial bonding strength, surface nano-hardness, corrosion resistance and hydrogen permeation resistance of the coating all decreased significantly, indicating that the transition layer plays an important role in improving the interfacial bonding strength and assisting in optimizing the overall protective performance of the coating.
[0039] Compared with Example 2, Comparative Example 3 lacks the α-Al2O3 oxide interface barrier layer, which is the key to blocking hydrogen atom penetration and improving the corrosion resistance of the coating. After its absence, the interfacial bonding strength of the coating did not change significantly, but the hydrogen penetration prevention and corrosion resistance were significantly reduced, indicating that the α-Al2O3 oxide interface barrier layer plays a decisive role in the core protective function of the coating.
[0040] Compared with Example 2, Comparative Example 4 lacks an amorphous or nanocrystalline dense shell layer. This layer can improve the surface hardness of the coating and seal the surface pores. Even after its absence, the interfacial bonding strength of the coating remains at a high level, but the surface performance and protective effect are reduced. This indicates that the amorphous or nanocrystalline dense shell layer can further enhance the surface performance and comprehensive protective capability of the coating.
[0041] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A corrosion-resistant and hydrogen-resistant coating for the inner wall of a stainless steel armor layer, characterized in that, The coating, on the surface of the stainless steel armor layer substrate, comprises, from the inside out, a metal bonding layer, a transition layer, a MAX phase ceramic layer, an oxide interface barrier layer, and an amorphous or nanocrystalline dense shell layer; the metal bonding layer is a Cr layer or a NiCr alloy layer with a thickness of 100~500nm; the transition layer is a Ti or Al transition layer with a thickness of 20~100nm; the MAX phase ceramic layer is a Ti2AlC or Ti2AlN layer with a thickness of 1.5~3.0μm; the oxide interface barrier layer is mainly composed of α-Al2O3 with a thickness of 50~300nm; and the amorphous or nanocrystalline dense shell layer has a thickness of 20~80nm.
2. The coating according to claim 1, characterized in that, The MAX phase ceramic layer was deposited in situ on the transition layer surface using mid-frequency magnetron sputtering technology. During deposition, the substrate temperature was controlled at 700–800°C, pure argon was used as the working gas, and the base vacuum level of the vacuum chamber did not exceed 5.0 × 10⁻⁶. - ³Pa, working air pressure is 0.3~0.8Pa.
3. The coating according to claim 1, characterized in that, The oxide interface barrier layer is generated in situ by performing a medium-temperature controllable oxidation treatment on the MAX phase ceramic layer. The atmosphere of the medium-temperature controllable oxidation treatment is flowing dry air or a nitrogen-oxygen mixture with an oxygen volume fraction of 10-50%. The oxidation treatment temperature is controlled at 680-720℃ and the holding time is 2-4h.
4. The coating according to claim 1, characterized in that, The amorphous or nanocrystalline dense shell is formed by low-energy ion implantation onto the surface of the oxide interface barrier layer, followed by low-temperature annealing at 100-150°C for 1-2 hours. The implanted ions are nitrogen ions, with an implantation energy of 15-35 keV and an implantation dose of 5 × 10¹. 6 ~1×10¹ 8 ions / cm².
5. The coating according to claim 1, characterized in that, The substrate material of the stainless steel armor layer is 304 stainless steel, 316L stainless steel or duplex stainless steel, and the inner diameter of the armor layer is 5~100mm.
6. A method for preparing a corrosion-resistant and hydrogen-resistant coating as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Pretreatment: The inner wall of the stainless steel armor layer is sequentially cleaned and activated pretreatment; S2. Deposition of metal bonding layer, transition layer and MAX phase ceramic layer: The pretreated workpiece is placed in a magnetron sputtering equipment, and the vacuum chamber background vacuum level is evacuated to no higher than 5.0 × 10⁻⁶. - After ³Pa, the substrate is heated to 300~500℃, argon gas is introduced, and a Cr target or NiCr target is sputtered first to deposit a metal bonding layer with a thickness of 100~500nm on the inner wall of the stainless steel armor layer; then a Ti target or Al target is sputtered to deposit a transition layer with a thickness of 20~100nm on the metal bonding layer; then the substrate temperature is raised to 700~800℃, and a Ti-Al-C or Ti-Al-N composite target is sputtered using a medium frequency power supply to deposit a dense Ti2AlC or Ti2AlN ceramic layer on the transition layer. During the deposition process, the uniformity of the coating on the inner wall of the stainless steel armor layer must be ensured. S3. Oxidation treatment: The workpiece with the deposited MAX phase ceramic layer is placed in an oxidation furnace and kept at 680-720℃ for 2-4 hours in a flowing dry air or nitrogen-oxygen mixture atmosphere with oxygen volume fraction of 10-50%. Then it is cooled with the furnace to form a dense α-Al2O3 oxide interface barrier layer in situ. S4. Ion Implantation and Post-treatment: The oxidized workpiece is placed in an ion implantation device, and nitrogen ions with an energy of 15~35keV are implanted at a dose of 5×10¹. 6 ~1×10¹ 8 ions / cm²; After injection, the workpiece is subjected to low-temperature annealing treatment at a temperature of 100~150℃ and a holding time of 1~2h. Then it is sealed in an oxygen-free environment to obtain the corrosion-resistant and hydrogen-proof coating.
7. The method according to claim 6, characterized in that, In step S1, the cleaning and activation pretreatment includes sequential alkaline washing for degreasing, acid washing for activation, ultrasonic cleaning, and finally vacuum drying.
8. The method according to claim 6, characterized in that, In step S2, the method to ensure the uniformity of the coating on the inner wall of the stainless steel armor layer is workpiece rotation or planetary revolution.