Preparation method of austenitic stainless steel with hydrogen embrittlement resistance, high strength and high plasticity and twin crystal structure
Nanotwinned austenitic stainless steel was prepared by additive manufacturing and electrochemical hydrogen charging, which solved the problems of hydrogen embrittlement and pitting corrosion of austenitic stainless steel in hydrogen-containing environments. This achieved a simultaneous improvement in high strength and high plasticity, making it suitable for applications in various hydrogen environments.
Patent Information
- Application Number
- CN202511317989.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-16
- Publication Date
- 2026-01-23
AI Technical Summary
Existing austenitic stainless steels are prone to hydrogen embrittlement and pitting corrosion in hydrogen-containing environments, and traditional strengthening methods have the risk of coating peeling and an imbalance between strength and plasticity.
Austenitic stainless steel substrates were prepared using additive manufacturing technology. The current density and time in the electrochemical hydrogen charging electrolyte were controlled by electrochemical hydrogen charging method to form a nanotwin structure, ensuring that the twin density was 10%-40%. After heat treatment, a high-strength and high-plasticity twin structure with resistance to hydrogen embrittlement was formed.
It effectively suppresses hydrogen embrittlement and pitting corrosion in hydrogen-rich environments, achieving simultaneous growth in high strength and high plasticity of the material. Moreover, the preparation process is simple, the parameters are controllable, and there is no pollution. It is suitable for bipolar plates in automobiles, nuclear power, hydrogen transportation pipelines, and fuel cells.
Smart Images
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Abstract
Description
Technical Field
[0001] This application relates to a method for preparing austenitic stainless steel, and more particularly to a method for preparing a high-strength, high-ductility twinned austenitic stainless steel with resistance to hydrogen embrittlement. Background Technology
[0002] Hydrogen energy, as a clean and efficient green energy source, is crucial for driving economic development. Large-scale production, transportation, and storage of hydrogen energy are expected in the future. Austenitic stainless steel is often used in hydrogen-environment environments due to its low hydrogen diffusivity and high hydrogen solubility. However, in materials used in hydrogen-environment environments, hydrogen atoms adsorb and diffuse into the metal, leading to brittle fracture, a phenomenon known as hydrogen embrittlement.
[0003] Pre-treated hardened austenitic stainless steel, such as through cold rolling or pre-deformation, aims to introduce twins or high-density dislocations during the process. Twin boundaries themselves possess low interfacial energy and low hydrogen trapping capacity. Furthermore, twins can generate high-density slip dislocations through dislocation / twin interactions, suppressing the initiation of hydrogen-induced cracks and mitigating hydrogen embrittlement during material deformation. However, pre-deformation and cold rolling inevitably introduce martensitic structures into the material, which exacerbates hydrogen embrittlement and pitting corrosion problems.
[0004] Currently, methods used to mitigate hydrogen embrittlement of austenitic stainless steel in hydrogen-exposed environments include pretreatment and surface coating. Surface coating involves depositing highly corrosion-resistant coatings on the stainless steel surface using electrodeposition or magnetron sputtering techniques. Examples include TiC or some plasma oxidation coatings, the purpose of which is to reduce the contact area between the stainless steel and hydrogen, thus reducing hydrogen diffusivity. However, the application of such coatings must consider the problem of coating peeling or damage under long-term operating conditions. Therefore, seeking new strengthening methods to enhance the material's resistance to hydrogen embrittlement is crucial. Furthermore, this strengthening method needs to balance the relationship between strength and plasticity and take into account the application in corrosive environments. Summary of the Invention
[0005] This application provides a method for preparing austenitic stainless steel with a high-strength, high-ductility twinned structure resistant to hydrogen embrittlement, solving the problems of hydrogen embrittlement leading to sudden failure due to reduced strength or ductility in austenitic stainless steel under hydrogen-exposed environments, as well as pitting corrosion under hydrogen-exposed environments. The specific technical solution is as follows: In a first aspect, a method for preparing austenitic stainless steel with a high strength and high plasticity and a hydrogen embrittlement resistant twin structure is provided, which includes the following steps: preparing an austenitic stainless steel substrate by additive manufacturing technology; preparing an electrochemical hydrogen-charged electrolyte and placing the austenitic stainless steel substrate in the electrochemical hydrogen-charged electrolyte; performing electrochemical hydrogen charging, controlling the current density, and preparing a nano-twinned austenitic stainless steel.
[0006] In one embodiment, the austenitic stainless steel substrate is prepared by selective laser printing.
[0007] In one embodiment, the austenitic stainless steel substrate is a 304 series stainless steel or a 316 series stainless steel.
[0008] In one embodiment, the electrochemical hydrogen charging electrolyte is a 0.5 M H2SO4+400 mg / L thiourea solution, a NaOH+thiourea solution or a NaCl+thiourea solution.
[0009] In one embodiment, the current density is 80 mA / cm 2 -180 mA / cm 2 .
[0010] In one embodiment, the hydrogen charging time is 6 h-160 h.
[0011] In one embodiment, the method further comprises the step of: heat treating the hydrogen-charged austenitic stainless steel substrate.
[0012] In one embodiment, the heat treatment temperature is 300 ℃-450 ℃, and the heat treatment time is 2 h-6 h.
[0013] In one embodiment, the density of the nanometer and sub-micron scale twins formed in the austenitic stainless steel substrate ranges from 10%-40%, and the twin density changes with the charging time, and the twin density is preferably 20%-30%.
[0014] In one embodiment, during the hydrogen charging-induced change in the twin structure of the austenitic stainless steel substrate, the twin structure changes in a gradient manner, and during the hydrogen charging process, the phase structure of the austenitic stainless steel substrate remains a single austenite phase.
[0015] In the embodiments of the present application, the austenitic stainless steel substrate is first prepared by additive manufacturing technology, and then the austenitic stainless steel substrate is hydrogen-charged by electrochemical hydrogen charging. The austenitic stainless steel prepared in this way has hydrogen embrittlement sensitivity resistance and pitting corrosion resistance, and has the characteristics of simple preparation process, controllable parameters, low energy consumption and no pollution. The austenitic stainless steel prepared in the present application is suitable for hydrogen environment such as automobile, nuclear power, hydrogen transportation pipeline and fuel cell bipolar plate. BRIEF DESCRIPTION OF DRAWINGS
[0016] The drawings described herein are used to provide further understanding of the present application, and form a part of the present application. The illustrative embodiments of the present application and their descriptions serve to explain the present application, and do not constitute an improper limitation on the present application. In the drawings: Figure 1This is a schematic diagram of the steps in the preparation method of the hydrogen embrittlement-resistant, high-strength, high-ductility twinned austenitic stainless steel of this application. Figure 2 This is a TEM image of Embodiment 1 of this application; Figure 3 This is a selected area electron diffraction pattern of Embodiment 1 of this application; Figure 4 This is the XRD pattern of Embodiment 1 of this application; Figure 5 This is the stress-strain tensile curve of Embodiment 1 of this application; Figure 6 This is an EBSD diagram of Embodiment 2 of this application; Figure 7 This is a corrosion morphology diagram of Embodiment 2 of this application; Figure 8 This is the stress-strain tensile curve of Embodiment 3 of this application; Figure 9 This is the stress-strain tensile curve of Embodiment 4 of this application. Detailed Implementation
[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0018] Please see Figure 1 This is a schematic diagram illustrating the steps of the preparation method of the hydrogen embrittlement-resistant, high-strength, high-ductility twinned austenitic stainless steel according to this application. As shown in the figure, the preparation method of the hydrogen embrittlement-resistant, high-strength, high-ductility twinned austenitic stainless steel of this embodiment is used to prepare hydrogen embrittlement-resistant, high-strength, high-ductility twinned austenitic stainless steel, which is suitable for hydrogen environments such as automobiles, nuclear power plants, hydrogen transportation pipelines, and fuel cell bipolar plates. In this embodiment, the preparation method of the hydrogen embrittlement-resistant, high-strength, high-ductility twinned austenitic stainless steel includes the following steps S1 to S3. In step S1, an austenitic stainless steel substrate is prepared by additive manufacturing technology. As a rapid prototyping technology, additive manufacturing can directly print complete structural parts. The high cooling rate and repeated thermal cycling in this process lead to the formation of a special microstructure in the material. This microstructure exhibits a non-equilibrium metastable cellular structure, which can induce nanotwin structures in a hydrogen environment, thereby improving performance. The twin density at the nano and submicron scales formed in the austenitic stainless steel substrate varies from 10% to 40%. The austenitic stainless steel substrate is formed by selective laser printing (SLM). The austenitic stainless steel substrate is either 304 series stainless steel or 316 series stainless steel.
[0019] In the hydrogen environment, the defects such as grain boundary, dislocation, phase boundary and impurities in the conventional austenitic stainless steel can adsorb hydrogen, reduce the stacking fault energy, and also produce local stress due to the aggregation of hydrogen, leading to martensitic transformation. In addition to the grain boundary, the SLM austenitic stainless steel sample also has a large number of cellular structures, which exhibit three unique aspects: (1) becoming the hydrogen trapping site in addition to the grain boundary, a large number of cellular structures also become active sites for adsorbing hydrogen. Further reducing the local internal stress at the grain boundary and reducing the possibility of martensitic transformation; (2) hydrogen can reduce the stacking fault energy (SFE) on the austenitic twinning plane, thereby promoting the slip of part of the dislocations under lower flow stress. The reduction of stacking fault energy reduces the stress induced to form twins. (3) The dislocation wall has a high density of partial dislocations. Corresponding to the twinning direction, the accumulated partial dislocations produce internal stress after adsorbing hydrogen, which induces the slip of partial dislocations and grows twins in the cellular dislocation wall. When hydrogen atoms occupy the interstitial sites in the cellular structure, they will induce lattice expansion and internal stress. The front of the partial dislocation forms a dislocation dipole, and its Burgers vector is equal to ±b, which matches the Burgers vector on the cell wall. Each time the partial dislocation slips forward, it will drag the accumulated tail dislocation behind it, and through the continuous emission of partial dislocations, the twin grows and forms nanotwins. The length of these twins increases layer by layer with the continuous emission of partial dislocations. In addition, due to the low interfacial energy and strong hydrogen trapping ability of the coherent twin boundary, compared with the grain boundary, the coherent twin boundary itself has the ability to resist hydrogen embrittlement.
[0020] In step S2, an electrochemical hydrogen charging electrolyte is configured, and the austenitic stainless steel substrate is placed in the electrochemical hydrogen charging electrolyte. In this embodiment, the electrochemical hydrogen charging electrolyte is a 0.5 M H2SO4+400 mg / L thiourea solution. In some other embodiments, the electrochemical hydrogen charging electrolyte can also select other electrolytes, such as NaOH+thiourea solution or NaCl+thiourea solution, etc. Among them, thiourea is also selected as a poisoning agent, and other optional poisoning agents such as NH4SCN can also be selected.
[0021] In step S3, the austenitic stainless steel substrate is subjected to hydrogen charging in an electrochemical hydrogen charging electrolyte. The key to the formation of twins in the additive printed sample (austenitic stainless steel substrate) under hydrogen charging is the hydrogen concentration, which affects the size of the reduced stacking fault energy and whether the internal stress is greater than the critical internal stress for the formation of twins, and the size of the hydrogen concentration depends on the hydrogen charging conditions: electrolyte, current density, hydrogen charging time. The twin density in the austenitic stainless steel substrate changes with the charging time, and the twin density is preferably 20%-30%, and during the process of hydrogen charging-induced change in the twin structure of the austenitic stainless steel substrate, the twin structure is gradiently changed, and the corresponding distribution is from several nanometers to ten microns, which is due to the different H atom concentrations at different depths. In the present embodiment, the current density is 80 mA / cm 2 -180 mA / cm 2 , and the hydrogen charging time is 6 h -160 h. During the hydrogen charging process, the phase structure of the austenitic stainless steel substrate remains single austenite phase, and during the process, there is no other structural change.
[0022] As described above, the present embodiment uses an electrochemical hydrogen charging method to induce twin growth. Compared with traditional methods such as rolling and pre-deformation to introduce twins, hydrogen-induced twinning realizes real-time strengthening of materials in a hydrogen environment without the introduction of martensite, precipitates and other structures. The formation of twins provides hardening and strengthening, inhibits the initiation of cracks, and avoids hydrogen embrittlement caused by hydrogen atom injection. At the same time, the partial dislocation slip regulated at the twin boundary can further produce plastic deformation. Therefore, the strength and plasticity are simultaneously increased under hydrogen charging conditions. The hydrogen embrittlement-resistant high-strength high-plasticity twinned austenitic stainless steel prepared in the present embodiment is based on the strengthening provided by hydrogen-induced twinning and the plasticity provided by the slip of partial dislocations at the twin boundary. These strengthening methods will not cause hydrogen embrittlement and premature fracture of the material.
[0023] It should be noted that the twin density referred to in the present embodiment refers to the percentage of the equivalent circular area of the grain containing twins to the total area, the thickness of the twin lamella is several nanometers to several tens of nanometers, and the length of the twin is several nanometers to several tens of microns. The hydrogen-induced twinned structure required in the present embodiment can be induced by electrochemical hydrogen charging to generate surface twins, wherein the hydrogen charging current density can be adjusted according to the powder composition and the stacking fault energy of the printed sample.
[0024] The preparation method of the anti-hydrogen embrittlement high-strength high-plasticity twinned structure austenitic stainless steel of the embodiment first prepares an austenitic stainless steel base material through additive manufacturing, and then charges hydrogen into the austenitic stainless steel base material through an electrochemical hydrogen charging electrolyte. The inhibition of hydrogen embrittlement of the thus-prepared austenitic stainless steel mainly comes from the plasticity strengthening provided by hydrogen-induced twinning, the formation conditions of the twinning are basically equivalent to the use conditions of the material in a hydrogen environment, no other sample treatment is needed, the recycling and sustainable development requirements are met. Meanwhile, the high-strength anti-hydrogen embrittlement steel has the characteristics of multifunction, high surface hardness, good thermal stability, significant pitting resistance, etc. The preparation process of the embodiment is simple, the parameters are controllable, the energy consumption is low, and the process is pollution-free. Compared with other methods of introducing twinned structure such as rolling and dynamic plastic deformation, the nanometer / submicron scale twinned structure can be prepared in any shaped workpiece.
[0025] In the embodiment, the preparation method of the anti-hydrogen embrittlement high-strength high-plasticity twinned structure austenitic stainless steel further includes the following step S4. The hydrogen-charged austenitic stainless steel base material is subjected to heat treatment in step S4. The heat treatment temperature is 300 ℃-450 ℃, and the heat treatment time is 2 h-6 h.
[0026] The beneficial effects of the preparation method of the anti-hydrogen embrittlement high-strength high-plasticity twinned structure austenitic stainless steel of the present application will be described below with specific examples.
[0027] Example 1 Taking the additive manufacturing austenitic stainless steel as the base material, the nanotwin is prepared by the electrochemical hydrogen charging method, and the steps are as follows: after polishing and polishing, the SLM 304L stainless steel plate with a thickness of 1 mm is connected to the cathode and put into the electrolytic tank, the electrolyte is 0.5 M H2SO4+400 mg / L thiourea solution, the hydrogen charging current density is 140 mA / cm 2 , and the hydrogen charging time is 72 h at room temperature, to obtain a 304L stainless steel plate with high-density twinning.
[0028] The SLM 304L stainless steel plate with high-strength anti-hydrogen embrittlement twinned structure obtained above is observed by a transmission electron microscope (JEM 2010, Japan JEOL Electronics Co., Ltd.), and the results show that the main characteristics of the microstructure are nanometer and submicron scale twinning, cellular structure and austenitic phase, as shown in Figure 2 , the thickness of the twinned layer is 25 nm, and stable nanotwins are formed. The selected area electron diffraction spot proves the twinned structure, as shown in Figure 3 ; XRD analysis, as shown in Figure 4 , the diffraction peak shows a single austenitic phase. The engineering stress-strain curve obtained by the tensile test is as shown in Figure 5As shown, the yield strength of the original SLM 304L stainless steel plate is 470 MPa, and the fracture elongation is 50%, while the yield strength of the SLM sample after electrochemical hydrogen charging is 510 MPa, and the fracture elongation is 52%.
[0029] Example 2 With the additive manufacturing austenitic stainless steel as the substrate, the nano-twins were prepared by the electrochemical hydrogen charging method, and the steps were as follows: the SLM 304L stainless steel plate with a thickness of 1 mm was polished and polished, and then connected to the cathode and put into the electrolytic cell, the electrolyte was 0.1 M NaOH + 400 mg / L thiourea solution, the hydrogen charging current density was 100 mA / cm 2 , and the SLM 304L stainless steel plate with high-density twins was obtained after electrochemical hydrogen charging at room temperature for 6 h. The SLM 304L stainless steel plate with high-strength and hydrogen embrittlement-resistant twin structure obtained above was determined by EBSD, and the surface twin volume fraction was 10%, as shown in Figure 6 . The electrochemical corrosion was carried out by constant potential polarization (PS) test for 10 h at a potential window of 0.6 V (relative to SCE). All samples subjected to electrochemical corrosion test were polished with 5000 grit sandpaper and surface mechanically polished with 0.5 μm diamond paste before testing to obtain repeatable results. After electrochemical test, the surface morphology of the corrosion sample was observed by scanning electron microscope, as shown in Figure 7 , wherein the surface of the SLM 304L stainless steel plate is corroded by pits, while the surface of the sample after hydrogen charging has no corrosion pits.
[0030] Example 3 With the additive manufacturing austenitic stainless steel as the substrate, the nano-twins were prepared by the electrochemical hydrogen charging method, and the steps were as follows: the SLM 304L stainless steel plate with a thickness of 1 mm was polished and polished, and then connected to the cathode and put into the electrolytic cell, the electrolyte was 0.5 M NaCl + 400 mg / L NH4SCN solution. The hydrogen charging current density was 160 mA / cm 2 , and the SLM 304L stainless steel plate with high-density twins was obtained after electrochemical hydrogen charging at room temperature for 150 h. The SLM 304L stainless steel plate with high-strength and hydrogen embrittlement-resistant twin structure obtained above was determined by EBSD, and the surface twin volume fraction was 30%. The engineering stress-strain curve obtained by tensile test is shown in Figure 8 , the yield strength is 468 MPa, and the fracture elongation is 49%.
[0031] Example 4 The sample in Example 3 was heat treated at a temperature of 400 o C for 2 h. The engineering stress-strain curve obtained by tensile test of the material is shown in Figure 9As shown, the yield strength thereof is 505 MPa, and the fracture elongation thereof is 52% Example 5 The nanotwins are prepared by electrochemical hydrogen charging on the basis of additive manufacturing austenitic stainless steel as follows: after polishing and polishing, the SLM 316L stainless steel plate with a thickness of 1 mm is connected to the cathode and put into the electrolytic tank, the electrolyte is 0.5 M H2SO4+400 mg / L thiourea solution, the hydrogen charging current density is 180 mA / cm 2 After electrochemical hydrogen charging for 96 h at room temperature, the 316L stainless steel plate with high-density twins is obtained.
[0032] The SLM 316L stainless steel plate with high-strength and hydrogen embrittlement-resistant twin structure obtained above has a surface twin volume fraction of 25% as determined by EBSD. The engineering stress-strain obtained by tensile test shows that the yield strength thereof is 576 MPa, and the fracture elongation thereof is 53%.
[0033] As shown in the above examples 1 to 5, the hydrogen embrittlement-resistant high-strength and high-plasticity twin structure austenitic stainless steel prepared in the present application has the characteristics of high yield strength, tensile strength and high ductility. In addition, the preparation method of the present application is completely equivalent to the working condition of the material in the hydrogen environment, effectively utilizes the beneficial aspects of hydrogen atoms, and at the same time inhibits the occurrence of hydrogen embrittlement, effectively alleviates the current situation of hydrogen embrittlement of stainless steel materials in the hydrogen environment.
[0034] In summary, the present application provides a preparation method of hydrogen embrittlement-resistant high-strength and high-plasticity twin structure austenitic stainless steel, which first prepares an austenitic stainless steel substrate by additive manufacturing technology, and then charges hydrogen to the austenitic stainless steel substrate by electrochemical hydrogen charging. The austenitic stainless steel prepared in this way has hydrogen embrittlement sensitivity and pitting resistance, and the preparation process is simple, the parameters are controllable, the energy consumption is low, and the process is pollution-free. The austenitic stainless steel prepared in the present application is suitable for hydrogen environment such as automobile, nuclear power, hydrogen transportation pipeline and fuel cell bipolar plate.
[0035] It should be noted that in this text, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the statement "including a…" does not exclude the presence of another identical element in the process, method, article or device including the element.
[0036] The embodiments of the present application are described above with reference to the accompanying drawings, but the present application is not limited to the specific embodiments described above, and the specific embodiments described above are merely illustrative, but not restrictive, and a person of ordinary skill in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims.
Claims
1. A method for producing a high-strength high-ductility twinned austenitic stainless steel which is resistant to hydrogen embrittlement, characterized by, The method comprises the following steps: Preparation of an austenitic stainless steel substrate by additive manufacturing technology; Preparation of an electrochemical hydrogen charging electrolyte and placing the austenitic stainless steel substrate in the electrochemical hydrogen charging electrolyte; Passing of an electric current into the electrochemical hydrogen charging electrolyte and hydrogen charging to perform hydrogen charging operation on the austenitic stainless steel substrate.
2. The method of producing a high-strength high-plasticity twinned austenitic stainless steel according to claim 1, characterized by, The austenitic stainless steel substrate is prepared by selective laser printing.
3. The method of producing a high-strength high-plasticity twinned austenitic stainless steel according to claim 1, characterized by, The austenitic stainless steel substrate is a 304 series stainless steel or a 316 series stainless steel.
4. The method for preparing hydrogen-embrittlement-resistant, high-strength, and high-ductility twinned austenitic stainless steel according to claim 1, characterized in that, The electrochemical hydrogen charging electrolyte is a 0.5 M H2SO4+400 mg / L thiourea solution, a NaOH+thiourea solution or a NaCl+thiourea solution.
5. The method for preparing hydrogen-embrittlement-resistant, high-strength, and high-ductility twinned austenitic stainless steel according to claim 1, characterized in that, The density of the current is 80 mA / cm 2 - 180 mA / cm 2 .
6. The method for preparing hydrogen-embrittlement-resistant, high-strength, and high-ductility twinned austenitic stainless steel according to claim 1, characterized in that, The hydrogen charging time is 6 h-160 h.
7. The method of claim 1, wherein the anti-hydrogen embrittlement high-strength high-ductility twinned-phase austenitic stainless steel is prepared by the steps of: preparing a stainless steel powder; and sintering the stainless steel powder. The method further comprises the following steps: Heat treatment of the hydrogen-charged austenitic stainless steel substrate.
8. The method of producing a high-strength high-plasticity twinned austenitic stainless steel according to claim 7, characterized by, Heat treatment temperature 300 o C -450 o C, heat treatment time 2 h -6 h.
9. The method of claim 1, wherein the anti-hydrogen embrittlement high-strength high-ductility twinned-structured austenitic stainless steel is prepared by the steps of: The density of the nanometer and sub-micron scale twins formed in the austenitic stainless steel substrate ranges from 10% to 40%, and the twin density changes with the charging time, and the twin density is preferably 20%-30%. 10. The method for preparing hydrogen-embrittlement-resistant, high-strength, high-ductility twinned austenitic stainless steel according to claim 1, characterized in that, In the process of hydrogen charging-induced change of the twin structure of the austenitic stainless steel substrate, the twin structure is gradiently changed, and the phase structure of the austenitic stainless steel substrate remains single austenite phase during the hydrogen charging process.