Composite hydrogen-resistant coating of high-strength maraging stainless steel and preparation method of composite hydrogen-resistant coating

Abstract

The invention discloses a composite hydrogen-resistant coating of high-strength maraging stainless steel and a preparation method of the composite hydrogen-resistant coating, and belongs to the field of metal material surface modification. The method comprises the steps that a base body is pretreated, then bias cleaning, Cu layer deposition and AlN layer deposition are sequentially carried out, and the Cu / AlN composite hydrogen-resistant coating is obtained. Through the synergistic effect of the Cu layer and the AlN layer, the binding force of the coating and a base body is remarkably enhanced, coating stripping and microcracks caused by thermal stress are avoided, and meanwhile an efficient hydrogen diffusion barrier is formed. The process is simple, the cost is low, the hydrogen embrittlement resistance of the high-strength maraging stainless steel plated with the coating is remarkably improved, and the coating is suitable for long-acting protection of the high-strength maraging stainless steel in a hydrogen-rich environment.

Description

Technical Field

[0001] This invention belongs to the field of surface modification of metallic materials, specifically relating to a composite hydrogen barrier coating for high-strength martensitic aging stainless steel and its preparation method. Background Technology

[0002] In the global transition to a low-carbon energy structure, hydrogen energy, with its clean and efficient advantages, has become a research and application hotspot in the energy field. Metallic materials are the core structural materials in hydrogen energy storage, transportation, and application systems, and their service safety and reliability directly determine the stable operation of related equipment. However, metallic materials are highly susceptible to hydrogen embrittlement in a hydrogen environment. When the hydrogen content entering the material reaches a certain threshold, the material experiences a severe loss of strength or toughness under the combined effects of hydrogen and stress; this is known as hydrogen embrittlement. The higher the strength of a metallic material, the higher its sensitivity to hydrogen embrittlement. Hydrogen embrittlement has become one of the main bottlenecks restricting the application of high-end metallic materials.

[0003] Currently, efficient prevention and control approaches for hydrogen embrittlement in high-strength steel mainly fall into two categories: one is to construct a physical barrier by applying a protective coating, blocking the channels for external hydrogen atoms to penetrate the material matrix; the other is to regulate and optimize the material's microstructure to build stable hydrogen trapping sites, thereby achieving efficient capture of invading hydrogen. Among these, the coating method, due to its direct protection, wide applicability, strong stability, and convenient maintenance, shows superior engineering application prospects in the prevention and control of hydrogen embrittlement in high-strength steel. However, existing hydrogen-barrier coating technologies are mostly developed for ordinary carbon steel or low-alloy steel. For example, CN117802458A discloses a composite nitride hydrogen-barrier coating for carbon steel surfaces, employing a multi-layer nitride structure of CrN, TiN, and AlN. However, the bonding strength between this coating and the metal substrate is weak, and it is designed for ordinary carbon steel with low strength, resulting in a much lower risk of hydrogen embrittlement compared to high-strength maraging stainless steel. Another example is CN119040828A, which discloses a composite hydrogen-barrier coating for high-strength steel surfaces, consisting of an amorphous structure formed by oxides of Al, Cr, and Zr. While this coating has a certain hydrogen-barrier effect, its coefficient of thermal expansion differs significantly from that of the high-strength maraging stainless steel substrate. Under cyclic temperature changes, repeated thermal stress occurs at the coating-substrate interface, accelerating coating peeling and failure.

[0004] For martensitic aging stainless steels with yield strengths exceeding 1500 MPa, the diverse alloying elements, complex microstructure, high surface energy, and tendency to form passivation films make the bonding between the coating and the substrate more challenging. Existing coating systems on such ultra-high-strength substrates often exhibit insufficient bonding strength, susceptibility to cracking and detachment, and difficulty in effectively preventing hydrogen embrittlement. Furthermore, high-strength martensitic aging stainless steels are extremely sensitive to hydrogen embrittlement; even trace amounts of hydrogen permeation can lead to a significant decrease in mechanical properties, thus placing higher demands on the density and hydrogen barrier efficiency of the coating.

[0005] Therefore, how to develop a coating that is firmly bonded to a high-strength martensitic aging stainless steel substrate, has good thermal matching, and possesses excellent hydrogen barrier properties has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that the existing hydrogen barrier coating has insufficient bonding force with the high-strength martensitic aging stainless steel substrate, making it difficult to form a stable and defect-free hydrogen barrier protective layer on the substrate surface.

[0007] The technical solution adopted by this invention to solve its technical problem is: In a first aspect, the present invention provides a method for preparing a composite hydrogen-barrier coating on high-strength martensitic aging stainless steel, comprising the following steps: S1. The high-strength martensitic aging stainless steel matrix is ​​sequentially ground, polished, cleaned and dried. S2. The substrate treated in step S1 is placed in a physical vapor deposition apparatus, first subjected to bias cleaning, and then subjected to coating treatment to obtain high-strength martensitic aging stainless steel coated with Cu / AlN composite hydrogen barrier coating. The coating process specifically involves: depositing a Cu layer using a Cu target at a chamber temperature of 200-300℃ and an argon flow rate of 20-23 sccm for 8-10 minutes, resulting in a thickness of 50-60 μm; subsequently, depositing an AlN layer using an AlN target at a chamber temperature of 200-300℃ and an argon flow rate of 30-35 sccm for 15-20 minutes, resulting in a thickness of 150-170 μm, ultimately obtaining a Cu / AlN composite hydrogen barrier coating.

[0008] In step S1 above, the chemical composition of the high-strength martensitic aging stainless steel matrix, by mass percentage, is: C≤0.02%, 12.00%≤Cr≤13.00%, 8.50%≤Ni≤9.50%, 3.50%≤Co≤5.00%, 2.00%≤Mo≤3.00%, 0.30%≤Al≤0.60%, with the balance being Fe and unavoidable impurities.

[0009] In step S1 above, the high-strength martensitic aging stainless steel matrix, after solution treatment and peak aging treatment, has a yield strength of 1500~1600MPa.

[0010] In step S1 above, the polishing specifically involves using SiC sandpaper of 400#, 800#, 1200#, 2000#, and 5000# in sequence, with the scratches of the next sandpaper completely covering the scratches of the previous sandpaper.

[0011] In step S1 above, the polishing specifically involves mechanical polishing with diamond polishing paste with a particle size of 1.5μm until the substrate surface is free of scratches and has a mirror finish.

[0012] In step S1 above, the cleaning and drying process specifically involves: using an alcohol solution for ultrasonic vibration cleaning for 10-20 minutes, followed by hot air drying for 5-10 minutes to ensure that the polished surface is free of stains.

[0013] In step S2 above, the bias cleaning specifically involves: setting the cavity temperature to 200~300℃ and evacuating the cavity until the vacuum level is ≤1.0×10⁻⁶. -3 Pa; then open the shut-off valve, set the flow limiting valve opening to 85°, the argon flow rate to 20 sccm, and set the bias voltage to -300V to keep the pressure in the chamber above 1.0 Pa. Perform bias cleaning for at least 20 minutes.

[0014] In step S2 above, during the coating process: when depositing the Cu layer, the Cu target power is 150~180W, the vacuum degree is maintained at 0.3~0.5Pa, and the substrate rotation speed is 5~8r / min; when depositing the AlN layer, the AlN target power is 220~250W, the vacuum degree is maintained at 0.1~0.3Pa, and the substrate rotation speed is 5~8r / min.

[0015] Secondly, the present invention provides a high-strength martensitic aging stainless steel coated with a Cu / AlN composite hydrogen-barrier coating, prepared by the above-described method.

[0016] Furthermore, the hydrogen diffusion coefficient of the aforementioned high-strength martensitic aging stainless steel is (1.17~2.45)×10⁻⁶. -9 cm 2 / s.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a Cu / AlN composite hydrogen barrier coating and its preparation method for high-strength martensitic aging stainless steel with a yield strength of 1500-1600 MPa. The composite coating, prepared using physical vapor deposition (PVD), consists of a Cu layer with good adhesion to the substrate and a dense AlN layer, with a total thickness controlled at 200-230 μm. In this composite coating, the Cu layer acts as a transition layer, forming a strong metallic bond with the substrate, significantly enhancing the adhesion between the coating and the substrate. Simultaneously, the FCC crystal structure of Cu acts as a deep hydrogen trap, effectively capturing diffusible hydrogen. The AlN layer, as an outer hydrogen barrier, with its hexagonal structure, extends the hydrogen diffusion path and increases the diffusion barrier, synergistically constructing a highly efficient hydrogen barrier system with the Cu layer. Furthermore, the high thermal conductivity of Cu effectively alleviates thermal stress concentration between the coating and the substrate, preventing interfacial failure under temperature cycling conditions. The synergy of these two layers overcomes the shortcomings of single ceramic coatings, such as high brittleness, easy cracking, and poor adhesion, while also avoiding the problem of insufficient hydrogen barrier efficiency in metal coatings.

[0018] The present invention provides a continuous, dense, and defect-free composite coating on the surface of martensitic aging stainless steel with a yield strength exceeding 1500 MPa. Experiments show that this composite coating can reduce the hydrogen diffusion coefficient of the substrate by more than an order of magnitude, significantly reducing the penetration of diffusible hydrogen into the substrate, thereby significantly improving the service safety of high-strength martensitic aging stainless steel in hydrogen-rich environments. This invention is low-cost and simple to implement, providing a reliable technical solution to the hydrogen embrittlement problem of ultra-high-strength stainless steel. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the hydrogen permeation experimental apparatus involved in the present invention; Figure 2 This is the hydrogen permeation curve of the sample obtained in Example 1 of this invention; Figure 3 This is the hydrogen permeation curve of the sample obtained in Example 2 of this invention; Figure 4 This is the hydrogen permeation curve of the sample obtained in Example 3 of this invention; Figure 5 This is the hydrogen permeation curve of the sample obtained in Comparative Example 1 of this invention. Detailed Implementation

[0020] To make the technical problems, solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with the embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as understood by one of ordinary skill in the art.

[0021] High-strength martensitic aging stainless steel differs fundamentally from ordinary carbon steel or low-alloy steel. This material contains multiple alloying elements such as Cr, Ni, Co, Mo, and Al. Through solution treatment and peak aging, intermetallic compounds precipitate, achieving strengthening. Its microstructure is complex, its surface energy is high, and it readily forms a dense passivation film. These characteristics result in insufficient interfacial adhesion when conventional hydrogen-barrier coatings are deposited on this type of substrate, leading to easy peeling during service. Furthermore, because the substrate itself is extremely sensitive to hydrogen embrittlement, even trace amounts of hydrogen permeation can cause a sharp decline in mechanical properties. Therefore, hydrogen-barrier coating technologies developed for ordinary carbon steel or 900–1200 MPa high-strength steel cannot be directly applied to 1500–1600 MPa martensitic aging stainless steel.

[0022] Therefore, to address the issues of insufficient adhesion and poor thermal compatibility between high-strength martensitic aging stainless steel substrates with yield strengths of 1500-1600 MPa and existing hydrogen-barrier coatings, this invention provides a method for preparing a composite hydrogen-barrier coating for high-strength martensitic aging stainless steel. This invention employs physical vapor deposition (PVD) to sequentially deposit a Cu layer and an AlN layer on the substrate surface. Through a specific bilayer structure design and adaptation of process parameters to the substrate, a bilayer composite hydrogen-barrier coating is formed, thus solving the aforementioned problems. The specific steps are described in detail below.

[0023] I. Matrix Pretreatment First, the high-strength martensitic aging stainless steel substrate undergoes pretreatment. The purpose of pretreatment is to remove oxide scale, oil stains, and processing marks from the substrate surface, obtaining a clean, smooth, and surface-active mirror finish, providing a good interface foundation for subsequent coating. Specifically, SiC sandpaper of grades 400#, 800#, 1200#, 2000#, and 5000# is used for progressive polishing, with the scratches of the next sandpaper completely covering those of the previous one to eliminate surface defects and ensure a progressively improving surface smoothness. Subsequently, mechanical polishing is performed using diamond polishing paste with a particle size of 1.5μm until the substrate surface is scratch-free and exhibits a mirror finish. After polishing, the substrate is immersed in an alcohol solution for ultrasonic cleaning for 10-20 minutes to remove residual polishing paste and oil stains, and then dried with hot air for 5-10 minutes to ensure the polished surface is free of stains. In this pretreatment step, the precision of grinding and polishing directly affects the bonding quality of the subsequent coating. For high-strength martensitic aging stainless steel, its surface passivation film is dense and firmly bonded to the substrate. If microscopic defects or residual contaminants exist on the surface, they will significantly reduce the interfacial bonding energy between the Cu layer and the substrate, causing the coating to preferentially crack and peel off from the defect points during service. Therefore, this embodiment requires polishing to a mirror finish to ensure interface cleanliness and microscopic smoothness.

[0024] As a preferred embodiment, the high-strength martensitic aging stainless steel matrix undergoes solution treatment and peak aging treatment to achieve a yield strength of 1500~1600MPa. The chemical composition of the matrix, by mass percentage, is: C≤0.02%, 12.00%≤Cr≤13.00%, 8.50%≤Ni≤9.50%, 3.50%≤Co≤5.00%, 2.00%≤Mo≤3.00%, 0.30%≤Al≤0.60%, with the balance being Fe and unavoidable impurities.

[0025] II. Biased cleaning The pretreated substrate is placed in a physical vapor deposition (PVD) apparatus and first subjected to bias cleaning. The specific process involves setting the chamber temperature to 200~300℃ and evacuating to a vacuum level ≤1.0×10⁻⁶ within the chamber. -3 Pa; then open the shut-off valve, set the flow-limiting valve opening to 85°, introduce argon gas at a flow rate of 20 sccm, and set the bias voltage to -300V to maintain the chamber pressure above 1.0 Pa for bias cleaning for at least 20 minutes. During this process, the argon gas is ionized to form plasma, which bombards the substrate surface under the acceleration of the negative bias voltage, producing a sputtering cleaning effect.

[0026] Bias cleaning is a crucial step in in-situ activation of the substrate surface before coating deposition. Its core function is to remove residual trace contaminants and dense passivation layers from the substrate surface through high-energy ion bombardment, while simultaneously increasing surface roughness and surface energy, thereby significantly improving the interfacial bonding strength between the subsequent coating and the substrate. For high-strength martensitic aging stainless steel, its surface passivation layer (mainly containing Cr2O3) is more stable and cannot be effectively removed by conventional solvent cleaning; surface activation must be achieved through the ion bombardment effect of bias cleaning. This invention employs a higher bias voltage (-300V) and a longer cleaning time (≥20min) to effectively break down and remove the passivation film, exposing a fresh, active metal surface, thus providing a highly active interface for the subsequent nucleation and growth of the Cu layer. If the bias voltage is too low or the time is too short, residual passivation film will lead to poor bonding between the Cu layer and the substrate, making the coating prone to overall peeling. In addition, the present invention sets the temperature of bias cleaning to 200~300℃, which is consistent with the subsequent coating temperature, in order to avoid the accumulation of thermal stress in the substrate during the heating-cooling-heating process and to ensure interface stability.

[0027] III. Deposited Cu Layer After bias cleaning, a coating process is performed in the same equipment. First, a Cu layer is deposited: under conditions of a chamber temperature of 200–300℃ and an argon flow rate of 20–23 sccm, a Cu layer is deposited using a Cu target for 8–10 minutes, resulting in a thickness of 50–60 μm. During deposition, the Cu target power is 150–180 W, the vacuum level is maintained at 0.3–0.5 Pa, and the substrate rotation speed is 5–8 r / min.

[0028] The Cu layer serves a dual function in this composite coating. First, as a transition layer, Cu exhibits excellent metallurgical compatibility with the high-strength martensitic aging stainless steel substrate. At deposition temperatures of 200–300 °C, Cu atoms can form strong metallic bonds with the substrate surface, significantly enhancing the adhesion between the coating and the substrate. Second, Cu has a face-centered cubic (FCC) crystal structure. The FCC structure contains numerous tetrahedral and octahedral interstitial spaces, which can act as hydrogen traps to capture hydrogen atoms diffusing to the interface, reducing the rate of hydrogen permeation into the substrate. Furthermore, Cu has a high thermal conductivity of 401 W / (m·K), far exceeding that of the subsequent AlN layer (approximately 180 W / (m·K)). Under fluctuating temperature conditions, this gradient thermal conductivity structure can effectively alleviate interfacial thermal stress and prevent coating cracking caused by differences in thermal expansion coefficients.

[0029] For high-strength martensitic aging stainless steel, precise control of Cu layer deposition parameters is crucial. In this invention, the deposition temperature is set at 200-300℃. Below 200℃, Cu atoms lack sufficient migration ability on the substrate surface, failing to form a continuous and dense film, and the interfacial diffusion layer is too thin, resulting in a significant decrease in adhesion. Above 300℃, the substrate may undergo tempering or phase transformation, while increased thermal stress leads to interfacial cracking. The deposition time is set at 8-10 minutes (corresponding to a thickness of 50-60 μm). If the deposition time is too short, the Cu layer is too thin, failing to form a complete coverage, resulting in insufficient overall coating adhesion and easy localized peeling. If the time is too long, the Cu layer is too thick, leading to excessive internal stress accumulation and microcracks on the coating surface. An argon flow rate of 20-23 sccm ensures a stable sputtering rate and a dense film structure. Too low a flow rate results in insufficient sputtering rate and a loose film, while too high a flow rate leads to excessively high sputtered particle energy and increased internal stress in the film.

[0030] IV. Deposited AlN layer After depositing the Cu layer, at the same chamber temperature of 200–300 °C, the working gas was switched to argon with a flow rate of 30–35 sccm. An AlN layer was then deposited using an AlN target for 15–20 min, achieving a thickness of 150–170 μm. During deposition, the AlN target power was 220–250 W, the vacuum level was maintained at 0.1–0.3 Pa, and the substrate rotation speed was 5–8 r / min. The AlN layer was deposited using non-reactive sputtering in a pure argon atmosphere using an AlN target to ensure the stoichiometry and density of the coating composition.

[0031] The AlN layer acts as the primary hydrogen barrier. AlN has a hexagonal crystal structure with dense atomic arrangement, resulting in a tortuous diffusion path and high diffusion barrier for hydrogen atoms. This significantly extends the hydrogen diffusion path and effectively reduces the hydrogen diffusion rate. Defects such as nitrogen vacancies in the AlN layer also act as hydrogen traps, increasing hydrogen solubility. Furthermore, AlN has a melting point above 2200℃ and excellent thermal stability, maintaining its structural integrity under high-temperature or temperature cycling conditions.

[0032] In this invention, the deposition temperature of 200-300℃ is set to balance the stability of the Cu layer and the density of the AlN layer. A deposition time of 15-20 min corresponds to a thickness of 150-170 μm. If the time is too short, the AlN layer is too thin, failing to form a continuous and dense hydrogen barrier, and incomplete coverage leads to exposure of the Cu layer, making the coating prone to peeling. If the time is too long, the internal stress of the hexagonal AlN layer increases sharply, resulting in obvious microcracks on the coating surface and compromising the coating's integrity. An argon flow rate of 30-35 sccm ensures stable sputtering of the AlN target; too low a flow rate results in a porous film, while too high a flow rate leads to excessive internal stress.

[0033] The core of this invention lies not only in the individual functions of the Cu and AlN layers, but also in their synergistic effect. While a single Cu coating exhibits good adhesion and thermal conductivity, it suffers from low hardness and limited hydrogen barrier efficiency. Conversely, a single AlN coating, while possessing excellent hydrogen barrier performance, exhibits poor adhesion to the high-strength martensitic aging stainless steel substrate, a large difference in thermal expansion coefficients, and high brittleness, making it prone to cracking. This invention combines the two: the Cu layer, as the bottom layer, solves the adhesion and thermal matching problems between AlN and the substrate, while the AlN layer, as the top layer, provides a high-density hydrogen diffusion barrier. Simultaneously, the FCC structure of Cu and the hexagonal structure of AlN capture and hinder hydrogen atoms through different mechanisms, extending the hydrogen diffusion path and significantly improving the hydrogen barrier effect. Furthermore, the high thermal conductivity of Cu and the low thermal conductivity of AlN create a gradient transition, effectively dissipating interfacial thermal stress and preventing coating peeling under temperature cycling conditions.

[0034] Through the above steps, bias cleaning, Cu layer deposition, and AlN layer deposition are continuously completed in the PVD equipment, ultimately yielding high-strength martensitic aging stainless steel coated with a Cu / AlN composite hydrogen-barrier coating. The total thickness of this composite coating is 200~230μm, with the Cu layer being 50~60μm and the AlN layer being 150~170μm.

[0035] The following specific embodiments will be provided to explain the solution of the present invention. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0036] In Examples 1-3 below, the chemical composition of the high-strength martensitic aging stainless steel matrix used, by mass percentage, is as follows: C≤0.02%, 12.00%≤Cr≤13.00%, 8.50%≤Ni≤9.50%, 3.50%≤Co≤5.00%, 2.00%≤Mo≤3.00%, 0.30%≤Al≤0.60%, with the balance being Fe and unavoidable impurities. After solution treatment and peak aging, the stainless steel was sequentially polished with 400#, 800#, 1200#, 2000#, and 5000# SiC sandpaper, then mechanically polished to a mirror finish with 1.5μm diamond polishing paste, followed by ultrasonic cleaning with an alcohol solution for 15 minutes, and finally dried with hot air for 5 minutes, completing the pretreatment before coating. The pretreated substrate material was processed into 20×20mm pieces and placed in a physical vapor deposition apparatus, where a vacuum was evacuated to a vacuum level ≤1.2×10⁻⁶. -3 Pa. The coating targets selected are Cu targets and AlN targets.

[0037] Example 1 Bias cleaning parameters: Temperature 200℃, Vacuum 1.0×10⁻⁶ -3 Pa, flow limiting valve opening 85°, argon flow rate 20 sccm, bias voltage -300V, cleaning time 20 min.

[0038] Cu coating: Argon flow rate 20 sccm, Cu target power 150 W, vacuum degree 0.5 Pa, substrate rotation speed 5 r / min, temperature 200 ℃, deposition time 10 min.

[0039] AlN layer deposition: argon flow rate 30 sccm, AlN target power 220 W, vacuum degree 0.3 Pa, substrate rotation speed 5 r / min, temperature 200 ℃, deposition time 20 min.

[0040] Example 2 Bias cleaning parameters: temperature 250℃, vacuum degree 0.7×10 -3 Pa, flow limiting valve opening 85°, argon flow rate 20 sccm, bias voltage -300V, cleaning time 30min.

[0041] Cu coating: Argon flow rate 21 sccm, Cu target power 170 W, vacuum degree 0.4 Pa, substrate rotation speed 5 r / min, temperature 250 ℃, deposition time 8 min.

[0042] AlN coating: Argon flow rate 33 sccm, AlN target power 230 W, vacuum degree 0.2 Pa, substrate rotation speed 5 r / min, temperature 250 ℃, deposition time 15 min.

[0043] Example 3 Bias cleaning parameters: temperature 300℃, vacuum degree 0.4×10 -3 Pa, flow limiting valve opening 85°, argon flow rate 20 sccm, bias voltage -300V, cleaning time 60min.

[0044] Cu plating: Argon flow rate 23 sccm, Cu target power 180 W, vacuum degree 0.3 Pa, substrate rotation speed 8 r / min, temperature 300 ℃, deposition time 8 min.

[0045] AlN layer deposition: argon flow rate 35 sccm, AlN target power 250 W, vacuum degree 0.1 Pa, substrate rotation speed 8 r / min, temperature 300 ℃, deposition time 15 min.

[0046] Comparative Example 1 The same high-strength martensitic aging stainless steel substrate as in the example was selected. After solution treatment and peak aging, it was successively ground, polished, cleaned and dried (the specific process is the same as in the example), but no coating treatment was performed to obtain the sample.

[0047] Adopting such Figure 1 The hydrogen permeation experimental apparatus shown was used to test samples from Examples 1-3 and Comparative Example 1, and the resulting hydrogen permeation curves are as follows. Figures 2-5 As shown. By Figure 2 As can be seen, the curve of Example 1 has a lag time of about 20ks, a steep rise phase, and a steady-state current of about 30μA; Figure 3 The curve of Example 2 has a lag time of about 15ks, a gentle rise, and a steady-state current of about 25μA. Figure 4 The curve in Example 3 has a lag time of approximately 15 ks, a steep rise, and a steady-state current of approximately 28 μA; while Figure 5 The hysteresis time of the uncoated substrate in Comparative Example 1 was only about 3 ks, indicating extremely fast hydrogen atom penetration and a steady-state current of about 28 μA. The calculated hydrogen diffusion coefficient for Example 1 was 1.17 × 10⁻⁶.-9 cm 2 / s, Example 2 is 2.45×10 -9 cm 2 / s, Example 3 is 1.98×10 -9 cm 2 / s, compared to 3.58×10 in Comparative Example 1. -8 cm 2 / s. It is evident that the Cu / AlN composite hydrogen-barrier coating prepared by this invention can reduce the hydrogen diffusion coefficient of high-strength martensitic aging stainless steel by approximately one order of magnitude, significantly improving the material's hydrogen-barrier performance.

[0048] Comparative Example 2 The same high-strength martensitic aging stainless steel substrate as in the example was selected. After solution treatment and peak aging, it was sequentially ground, polished, cleaned, and dried (the specific process was the same as in the example). The only difference between the subsequent steps and those in Example 1 was that the Cu layer deposition time was changed to 5 minutes and the AlN layer deposition time was changed to 10 minutes. Testing revealed that some of the composite hydrogen-barrier coating peeled off from its outer surface.

[0049] Comparative Example 3 The same high-strength martensitic aging stainless steel substrate as in the example was selected. After solution treatment and peak aging, it was sequentially ground, polished, cleaned, and dried (the specific process was the same as in the example). The only difference between the subsequent steps and those in Example 1 was that the Cu layer deposition time was changed to 15 min and the AlN layer deposition time was changed to 30 min. Testing revealed obvious microcracks on the outer surface of the composite hydrogen-barrier coating.

[0050] Comparative Example 4 The same high-strength martensitic aging stainless steel substrate as in the example was selected. After solution treatment and peak aging, it was sequentially ground, polished, cleaned, and dried (the specific process was the same as in the example). The only difference between the subsequent steps and those in Example 1 was that the argon flow rate for the Cu layer was changed to 10 sccm, and the argon flow rate for the AlN layer was changed to 20 sccm. Testing revealed that some of the composite hydrogen-barrier coating peeled off from its outer surface.

[0051] Comparative Example 5 The same high-strength martensitic aging stainless steel substrate as in the example was selected. After solution treatment and peak aging, it was sequentially ground, polished, cleaned, and dried (the specific process was the same as in the example). The only difference between the subsequent steps and those in Example 1 was that the argon flow rate for the Cu layer was changed to 30 sccm, and the argon flow rate for the AlN layer was changed to 40 sccm. Testing revealed obvious microcracks between the Cu and AlN layers of the composite hydrogen barrier coating.

[0052] Comparative Example 6 The same high-strength martensitic aging stainless steel substrate as in the example was selected. After solution treatment and peak aging, it was sequentially ground, polished, cleaned, and dried (the specific process was the same as in the example). The only difference between the subsequent steps and those in Example 1 was that the deposition temperature of both the Cu layer and the AlN layer was changed to 100℃. Testing revealed that some of the composite hydrogen-barrier coating peeled off from its outer surface.

[0053] Comparative Example 7 The same high-strength martensitic aging stainless steel substrate as in the example was selected. After solution treatment and peak aging, it was sequentially ground, polished, cleaned, and dried (the specific process was the same as in the example). The only difference between the subsequent steps and those in Example 1 was that the deposition temperature of both the Cu layer and the AlN layer was changed to 400℃. Inspection revealed obvious microcracks on the outer surface of the composite hydrogen-barrier coating.

[0054] Comparative Examples 2-7 all employed the same Cu / AlN bilayer structure as Example 1, but varied the deposition time, working gas flow rate, or deposition temperature. The results showed that regardless of whether the deposition time was too short or too long, the gas flow rate too low or too high, or the deposition temperature too low or too high, defects such as coating peeling or microcracks would occur. Therefore, the process parameter range defined in this invention is a necessary technical condition for obtaining a continuous, dense, defect-free, and firmly bonded Cu / AlN composite hydrogen-barrier coating.

Claims

1. A method for preparing a composite hydrogen-barrier coating on high-strength martensitic aging stainless steel, characterized in that, Includes the following steps: S1. The high-strength martensitic aging stainless steel matrix is ​​sequentially ground, polished, cleaned and dried. S2. Place the substrate treated in step S1 in a physical vapor deposition apparatus, perform bias cleaning first, and then perform coating treatment to obtain high-strength martensitic aging stainless steel coated with Cu / AlN composite hydrogen barrier coating. The coating process specifically involves: depositing a Cu layer using a Cu target at a chamber temperature of 200-300℃ and an argon flow rate of 20-23 sccm for 8-10 minutes, resulting in a thickness of 50-60 μm; subsequently, depositing an AlN layer using an AlN target at a chamber temperature of 200-300℃ and an argon flow rate of 30-35 sccm for 15-20 minutes, resulting in a thickness of 150-170 μm, ultimately obtaining a Cu / AlN composite hydrogen barrier coating.

2. The preparation method according to claim 1, characterized in that, In step S1, the chemical composition of the high-strength martensitic aging stainless steel matrix, by mass percentage, is: C≤0.02%, 12.00%≤Cr≤13.00%, 8.50%≤Ni≤9.50%, 3.50%≤Co≤5.00%, 2.00%≤Mo≤3.00%, 0.30%≤Al≤0.60%, with the balance being Fe and unavoidable impurities.

3. The preparation method according to claim 1, characterized in that: In step S1, the high-strength martensitic aging stainless steel matrix, after solution treatment and peak aging treatment, has a yield strength of 1500~1600MPa.

4. The preparation method according to claim 1, characterized in that, In step S1, the polishing specifically involves using SiC sandpaper of grades 400#, 800#, 1200#, 2000#, and 5000# in sequence, with the scratches of the next sandpaper completely covering the scratches of the previous sandpaper.

5. The preparation method according to claim 1, characterized in that, In step S1, the polishing specifically involves mechanical polishing with diamond polishing paste with a particle size of 1.5 μm until the substrate surface is free of scratches and has a mirror finish.

6. The preparation method according to claim 1, characterized in that, In step S1, the cleaning and drying process specifically involves: using an alcohol solution for ultrasonic vibration cleaning for 10-20 minutes, followed by hot air drying for 5-10 minutes to ensure that the polished surface is free of stains.

7. The preparation method according to claim 1, characterized in that, In step S2, the bias cleaning specifically involves: setting the cavity temperature to 200~300℃ and evacuating the cavity until the vacuum level is ≤1.0×10⁻⁶. -3 Pa; then open the shut-off valve, set the flow limiting valve opening to 85°, the argon flow rate to 20 sccm, and set the bias voltage to -300V to keep the pressure in the chamber above 1.0 Pa. Perform bias cleaning for at least 20 minutes.

8. The preparation method according to claim 1, characterized in that, In step S2, during the coating process: When depositing the Cu layer, the Cu target power is 150~180W, the vacuum degree is maintained at 0.3~0.5Pa, and the substrate rotation speed is 5~8 r / min; When depositing the AlN layer, the AlN target power is 220~250W, the vacuum degree is maintained at 0.1~0.3Pa, and the substrate rotation speed is 5~8 r / min.

9. A high-strength martensitic aging stainless steel coated with a Cu / AlN composite hydrogen-barrier coating, prepared by the preparation method according to any one of claims 1 to 8.

10. The high-strength martensitic aging stainless steel according to claim 9, characterized in that: The hydrogen diffusion coefficient of the high-strength martensitic aging stainless steel is (1.17~2.45)×10⁻⁶. -9 cm 2 / s.

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