Methods for obtaining the elastic modulus and hardness of the samples and the gas-phase hydrogen charging device.

Abstract

This invention provides a method for obtaining the elastic modulus and hardness of a sample and a gas-phase hydrogen charging device. The method includes dividing the sample into hydrogen-charged and non-hydrogen-charged samples; embedding conductive powder into the bottom of the hydrogen-charged and non-hydrogen-charged samples, and polishing the test surfaces of the hydrogen-charged and non-hydrogen-charged samples to obtain hydrogen-charged and non-hydrogen-charged samples; performing nanoindentation tests on the test surfaces to obtain load-depth curves of the hydrogen-charged and non-hydrogen-charged samples; calculating the elastic modulus and hardness of the hydrogen-charged and non-hydrogen-charged samples based on the load-depth curves; the nanoindentation tests include standard nanoindentation tests, micro-load nanoindentation tests, and variable-rate nanoindentation tests. This method can more comprehensively characterize the hydrogen embrittlement of materials and analyze the mechanism of hydrogen embrittlement.

Description

Technical Field

[0001] This invention relates to the field of hydrogen embrittlement analysis technology, specifically to a method for obtaining the elastic modulus and hardness of a sample and a gas-phase hydrogen charging device. Background Technology

[0002] Hydrogen embrittlement is a phenomenon in which hydrogen dissolved in metallic materials reduces the plasticity and strength of the materials, leading to cracking or delayed brittle failure. Furthermore, hydrogen embrittlement is characterized by its insidious nature, time lag, and suddenness. In particular, hydrogen-related components such as liquid hydrogen storage tanks, hydrogen pipelines, and hydrogen combustion chambers in hydrogen fuel engines are prone to catastrophic accidents when hydrogen embrittlement occurs, as the materials may fracture without warning.

[0003] In related technologies, hydrogen embrittlement is usually characterized by slow strain rate tensile tests on material samples, and then the mechanism of hydrogen embrittlement is analyzed. However, this method is a destructive test, which requires tensile testing on multiple samples and repeated tests, resulting in high costs and inaccurate test results. Summary of the Invention

[0004] Based on the above-mentioned technical problems, the present invention provides a method for obtaining the elastic modulus and hardness of a sample and a gas-phase hydrogen charging device, aiming to reduce testing costs, more comprehensively characterize the hydrogen embrittlement of materials and analyze the mechanism of hydrogen embrittlement, improve the accuracy of test results, and at least partially solve the above-mentioned technical problems.

[0005] In a first aspect, the present invention provides a method for obtaining the elastic modulus and hardness of a sample, comprising: dividing the sample into a hydrogen-filled sample and an unfilled sample; embedding conductive powder into the bottom of the hydrogen-filled sample and the unfilled sample, and polishing the test surfaces of the hydrogen-filled sample and the unfilled sample to obtain a hydrogen-filled sample and an unfilled sample; performing a nanoindentation test on the test surfaces to obtain load-depth curves of the hydrogen-filled sample and the unfilled sample; and calculating the elastic modulus and hardness of the hydrogen-filled sample and the unfilled sample based on the load-depth curves; wherein the nanoindentation test includes standard nanoindentation test, micro-load nanoindentation test, and variable rate nanoindentation test.

[0006] Optionally, a nanoindentation test is performed on the surface to be tested to obtain the load-depth curves of the hydrogen-filled sample and the unfilled sample, including: defining multiple spaced target points on the surface to be tested; moving the indenter to each target point in a preset order, and performing a downward press and upward press when moving to each target point to form multiple spaced indentation points.

[0007] Optionally, multiple target points are defined at intervals on the surface to be tested, including: defining nine target points on the surface to be tested, wherein the nine target points are arranged in a 3×3 matrix on the surface to be tested.

[0008] Optionally, the indenter is moved one by one to each of the target points in a preset order, and a downward press and an upward press are performed when it is moved to each target point to form multiple spaced indentations, including: the distance between any two adjacent indentations on the surface to be tested is 20 times the indentation depth of the indentation.

[0009] Optionally, the pressure head is moved sequentially to each of the target points in a preset order, and a downward press and an upward press are performed when it is moved to each target point to form multiple spaced pressure points. The method also includes controlling the pressure head to hold the load for a preset time when it is pressed down to each of the target points.

[0010] Optionally, the samples are divided into hydrogen-filled samples and non-hydrogen-filled samples, including: dividing the samples into two groups, both groups of samples are evacuated using a gas-phase hydrogen filling device; heating the samples to a preset temperature; filling one group of samples with hydrogen gas of a preset concentration, and filling the other group of samples with an inert gas of a preset concentration; cooling the two groups of samples to obtain hydrogen-filled samples and non-hydrogen-filled samples.

[0011] Optionally, the inert gas is argon.

[0012] Optionally, in the process of moving the pressure head one by one to each of the target points in a preset order, and performing a downward press and an upward press when moving to each target point to form multiple spaced pressure points: the pressure head is a glass pressure head.

[0013] Optionally, the pressure head is moved one by one to each of the target points in a preset order, and a downward pressure and an upward lifting are performed when it moves to each target point to form multiple spaced pressure points, including: the pressure head is pressed down at a constant speed and lifted up at a constant speed.

[0014] Secondly, the present invention provides a gas-phase hydrogen charging device, which can be applied to the method for obtaining the elastic modulus and hardness of the sample described in any of the above-mentioned optional embodiments. The gas-phase hydrogen charging device includes a receiving cavity, a vacuum pump, a heater, a first gas cylinder, and a second gas cylinder, wherein: the receiving cavity is used to contain the sample; the vacuum pump pipeline is connected to the receiving cavity; the heater is connected to the receiving cavity; the first gas cylinder stores hydrogen gas and is connected to the receiving cavity; the second gas cylinder stores inert gas and is connected to the receiving cavity.

[0015] The method for obtaining the elastic modulus and hardness of samples provided by the present invention involves dividing the samples into two groups: hydrogen-filled samples as the experimental group and unfilled samples as the control group. Both groups are then inlaid with conductive powder and polished to facilitate clearer observation of the indentation morphology on the sample surface using an electron microscope. After the inlay and polishing processes, nanoindentation tests are performed on both hydrogen-filled and unfilled samples. Specifically, both hydrogen-filled and unfilled samples can be tested using three methods: standard nanoindentation test, micro-load nanoindentation test, and variable-rate nanoindentation test, yielding different results. All of these tests can be performed using a nanoindentation instrument. The final results obtained are the load and indentation depth of the hydrogen-filled and unfilled samples, respectively. By analyzing multiple sets of load and indentation depth results, the elastic modulus and hardness of hydrogen-filled and unfilled samples under the three different conditions are calculated. Furthermore, the sensitivity of the material to hydrogen embrittlement and the mechanism of hydrogen embrittlement can be analyzed using the elastic modulus and hardness. Through these steps, this method conducts nanoindentation tests on both hydrogen-filled and unfilled samples at different load levels and loading rates. Nanoindentation tests cause minimal damage to the material, significantly reducing testing costs. During the nanoindentation test, the load and indentation depth before and after hydrogen filling can be analyzed, yielding the elastic modulus and hardness of the material before and after hydrogen filling. Depending on the testing method, changes in the material's displacement abruptness effect and creep depth, as well as other nanoindentation mechanical responses, can be recorded, thus providing a more comprehensive evaluation of the material's sensitivity to hydrogen embrittlement and the mechanism of hydrogen embrittlement. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a flowchart illustrating a method for obtaining the elastic modulus and hardness of a sample according to an exemplary embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of the gas-phase hydrogen charging device provided in an exemplary embodiment of the present invention; Figure 3 This is a table showing the relationship between samples with different hydrogen contents and sputtering time in an exemplary embodiment of the present invention; Figure 4 This is a schematic diagram comparing samples with different hydrogen contents in a secondary ion mass spectrometry depth profile according to an exemplary embodiment of the present invention. Figure 5 This is a schematic diagram comparing the mechanical responses of unfilled and hydrogen-filled samples under standard nanoindentation tests in an exemplary embodiment of the present invention. Figure 6 for Figure 5 A statistical table of partial results for testing the elastic modulus and hardness of unfilled and hydrogen-filled samples; Figure 7 This is a schematic diagram comparing the mechanical responses of uncharged and hydrogen-charged samples under micro-load nanoindentation testing in an exemplary embodiment of the present invention. Figure 8 This is a schematic diagram comparing the load-depth curves of an uncharged sample and a hydrogen-charged sample in an exemplary embodiment of the present invention. Figure 9 This is an exemplary embodiment of the present invention, showing a comparison of the maximum depth and creep of uncharged and hydrogen-charged samples at different loading rates; Figure 10 In an exemplary embodiment of the present invention, the elastic modulus and hardness of unfilled and hydrogen-filled samples are compared at different loading rates.

[0018] Explanation of reference numerals in the attached figures: 1. Receiving cavity; 2. Vacuum pump; 3. Heater; 4. First gas cylinder; 5. Second gas cylinder; 6. First shut-off valve; 7. Second shut-off valve; 8. Third shut-off valve; 9. Fourth shut-off valve; 10. Control panel; 11. Vacuum gauge; 12. Hydrogen leak alarm. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Hydrogen embrittlement is a phenomenon in which hydrogen dissolved in metallic materials reduces the plasticity and strength of the materials, leading to cracking or delayed brittle failure. Furthermore, hydrogen embrittlement is characterized by its insidious nature, time lag, and suddenness. In particular, hydrogen-related components such as liquid hydrogen storage tanks, hydrogen pipelines, and hydrogen combustion chambers in hydrogen fuel engines are prone to catastrophic accidents when hydrogen embrittlement occurs, as the materials may break without warning.

[0021] Furthermore, hydrogen embrittlement refers to the phenomenon where hydrogen is trapped and transported in various lattice defects (such as vacancies, grain boundaries, dislocations, and precipitates) of materials under hydrogen-exposed environments, leading to interactions and resulting in damage to material properties. This manifests as hydrogen pressure cracking, high-temperature hydrogen erosion, and hydrides. In recent years, researchers have proposed many hypotheses about hydrogen embrittlement based on theoretical calculations and experimental characterization. Among these, the most widely discussed are the hydrogen pressure theory, the weak bond theory, the hydrogen-induced local plasticity theory, and stress-induced hydride cracking. These theories suggest that hydrogen embrittlement is characterized by its insidious nature, time lag, and sudden onset; unexplained fractures can lead to catastrophic accidents and pose serious safety hazards.

[0022] In related technologies, the characterization methods for hydrogen embrittlement of materials mainly include macroscopic mechanical tests and mesoscopic secondary ion mass spectrometry. Macroscopic mechanical tests mainly include slow strain rate tensile tests, low-cycle fatigue tests, and fatigue crack propagation tests.

[0023] The slow strain rate tensile test is commonly used to characterize hydrogen embrittlement in material samples and to analyze the mechanism of hydrogen embrittlement. However, this method is a destructive test that requires tensile testing on multiple samples and repeated tests, which is costly and the test results are not accurate enough.

[0024] In other words, although this method can be used to characterize hydrogen embrittlement of materials in slow strain rate tensile tests, that is, to evaluate the hydrogen embrittlement sensitivity of materials based on the deterioration of tensile properties and changes in fracture morphology, it has significant limitations such as strong destructive force, low testing efficiency, difficulty in micro-region characterization, and difficulty in distinguishing the dominant mechanism of hydrogen embrittlement.

[0025] Furthermore, the hydrogen embrittlement susceptibility of most metallic materials increases with decreasing strain rate, requiring tensile tests at different strain rates, which further increases the test time and cost. In addition, slow strain rate tensile tests at the macroscopic scale cannot characterize hydrogen embrittlement in micro-regions such as welded joints, making it difficult to accurately reveal the microscopic physical mechanism. Finally, the stress level that hydrogen-related components experience during service is usually within the elastic stress range, so slow strain rate tensile tests that use yield strength, tensile strength, etc., as parameters for characterizing hydrogen embrittlement have certain limitations.

[0026] Based on the above-mentioned technical problems, the first aspect of the present invention provides a method for obtaining the elastic modulus and hardness of a sample, aiming to reduce testing costs, more comprehensively characterize the material for hydrogen embrittlement and analyze the mechanism of hydrogen embrittlement, and improve the accuracy of test results.

[0027] refer to Figure 1 As shown, this method mainly includes the following steps.

[0028] S1, the samples are divided into hydrogen-filled samples and non-hydrogen-filled samples.

[0029] S2, conductive powder is embedded in the bottom of the test surface of the hydrogen-filled sample and the non-hydrogen-filled sample, and the test surface of the hydrogen-filled sample and the non-hydrogen-filled sample is polished to obtain the hydrogen-filled sample and the non-hydrogen-filled sample.

[0030] S3, perform nanoindentation tests on the surface to be tested to obtain load-depth curves for hydrogen-filled and non-hydrogen-filled samples.

[0031] S4. Based on the load-depth curve, calculate the elastic modulus and hardness of the hydrogen-filled and unfilled samples.

[0032] The aforementioned nanoindentation tests include standard nanoindentation testing, micro-load nanoindentation testing, and variable rate nanoindentation testing.

[0033] The method for obtaining the elastic modulus and hardness of samples provided by the present invention involves dividing the samples into two groups: hydrogen-filled samples as the experimental group and unfilled samples as the control group. Both groups are then inlaid with conductive powder and polished to facilitate clearer observation of the indentation morphology on the sample surface using an electron microscope. After the inlay and polishing processes, nanoindentation tests are performed on both hydrogen-filled and unfilled samples. Specifically, both hydrogen-filled and unfilled samples can be tested using three methods: standard nanoindentation test, micro-load nanoindentation test, and variable-rate nanoindentation test, yielding different results. All of these tests can be performed using a nanoindentation instrument. The final results obtained are the load and indentation depth of the hydrogen-filled and unfilled samples, respectively. By analyzing multiple sets of load and indentation depth results, the elastic modulus and hardness of hydrogen-filled and unfilled samples under the three different conditions are calculated. Furthermore, the sensitivity of the material to hydrogen embrittlement and the mechanism of hydrogen embrittlement can be analyzed using the elastic modulus and hardness. Through these steps, this method conducts nanoindentation tests on both hydrogen-filled and unfilled samples at different load levels and loading rates. Nanoindentation tests cause minimal damage to the material, significantly reducing testing costs. During the nanoindentation test, the load and indentation depth before and after hydrogen filling can be analyzed, yielding the elastic modulus and hardness of the material before and after hydrogen filling. Depending on the testing method, changes in the material's displacement abruptness effect and creep depth, as well as other nanoindentation mechanical responses, can be recorded, thus providing a more comprehensive evaluation of the material's sensitivity to hydrogen embrittlement and the mechanism of hydrogen embrittlement.

[0034] Specifically, the purpose of embedding conductive powder on the test surfaces of the hydrogen-filled and non-hydrogen-filled samples in the above steps is to ensure that the obtained hydrogen-filled and non-hydrogen-filled samples meet the requirements for subsequent scanning of the indentation morphology of the sample surface by electron microscopy. Specifically, the material of the conductive powder can be thermosetting epoxy resin or phenolic thermosetting resin, etc. Among them, thermosetting epoxy resin has excellent edge preservation ability, chemical resistance and no shrinkage. In this embodiment, phenolic thermosetting resin is mostly used, taking advantage of its better conductivity, which facilitates analysis by electron microscopy.

[0035] In the above embodiments, polishing the test surfaces of hydrogen-filled and non-hydrogen-filled samples is also to enable the surfaces of hydrogen-filled and non-hydrogen-filled samples to meet the requirements of nanoindentation testing. That is, nanoindentation testing usually involves pressing down on the test sample surface with a diamond indenter. Polishing can prevent other irrelevant materials or contaminants on the sample surface from interfering with the test results, thereby improving the accuracy of the test results.

[0036] The nanoindentation test mentioned in the above embodiments is a simple and efficient non-destructive testing technique for obtaining the mechanical properties of micro-areas of materials. Specifically, it can be understood as placing the sample to be tested on the test stage of a nanoindenter, and applying a continuously varying ultra-low load to the sample under computer control. Specifically, a rigid indenter with a regular geometric shape is pressed into the surface of the sample at the micro-nano scale. The load-depth curve of the loading and unloading process is monitored by a high-precision sensor, and the elastic modulus and hardness of the sample are calculated according to the Oliver-Pharr algorithm. In detail, the nanoindentation test will be further described in the following embodiment.

[0037] The Oliver-Pharr algorithm mentioned above is also an algorithm that can calculate the corresponding elastic modulus and hardness based on the load-depth curve of the material to be tested. This embodiment will also elaborate on the specific calculation process of the Oliver-Pharr algorithm below, without going into too much detail here.

[0038] Furthermore, the standard nanoindentation test mentioned in the above embodiments can be understood as applying a force of 100mN to the surface of the sample under test through an indenter, and conducting the test according to the parameters of 30s loading + 30s holding + 10s unloading recommended by the international standard ISO14577-1-2015. That is, when the test is conducted in this way, when the indenter is pressed down to contact the surface of the sample under test, the force is continuously applied for 30 seconds, that is, the force increases by 3.33mN per second, until a force of 100mN is reached. After that, the force of 100mN is maintained for 30 seconds, and then the force is continuously reduced for 10 seconds, that is, the force decreases by 10mN per second, until the force is reduced to zero, and then the indenter is lifted up, thus completing one test.

[0039] The micro-load nanoindentation test mentioned in the above embodiments can be understood as applying a force of 1 mN to the surface of the sample under test through an indenter, and conducting the test according to the parameters of 30s loading + 30s holding + 10s unloading recommended by the international standard ISO14577-1-2015. That is, when the indenter is pressed down to contact the surface of the sample under test, the force is continuously applied for 30 seconds, that is, the force increases by 0.03 mN per second, reaching a force of 100 mN. Then, the applied force of 1 mN is maintained for 30 seconds, and then the applied force is continuously reduced for 10 seconds, that is, the force decreases by 0.1 mN per second, until the force is reduced to zero, and then the indenter is lifted, thus completing one test.

[0040] The variable-rate nanoindentation test mentioned in the above embodiments can be understood as applying and unloading loads at different rates. The maximum applied force can be 10mN. After applying 10mN, the applied force can be maintained for 30 seconds, and then the load can be unloaded at the same rate as the applied load rate to complete one test.

[0041] Specifically, taking an application rate of 1 mN / s as an example, the experimental procedure can be as follows: When the indenter is pressed down to contact the surface of the sample to be tested, the load on the sample surface is gradually increased at an application rate of 1 mN / s. After 10 seconds, the load is 10 mN. At this time, the 10 mN force is maintained for 30 seconds. Then, the load on the sample surface is reduced at a rate of 1 mN / s until the load is zero. The indenter is then lifted to complete one variable rate nanoindentation test.

[0042] Alternatively, the loading and unloading speeds mentioned above can be other values, such as 0.5 mN / s, 0.1 mN / s, and 0.05 mN / s. While keeping the maximum force constant at 10 mN, the time corresponding to both loading and unloading is 20 seconds at a speed of 0.5 mN / s; 100 seconds at a speed of 0.1 mN / s; and 200 seconds at a speed of 0.05 mN / s.

[0043] Therefore, this invention uses variable-rate nanoindentation testing to obtain a more comprehensive elastic modulus and hardness of hydrogen-filled material samples under different conditions by applying loads at different rates for different times. Then, the mechanism of hydrogen embrittlement can be analyzed by using the obtained elastic modulus and hardness.

[0044] Specifically, by testing the elastic modulus and hardness of hydrogen-filled and unfilled samples, the mechanism of hydrogen embrittlement can be analyzed. This can be understood as follows: after undergoing the aforementioned nanoindentation test, the elastic modulus and hardness of the hydrogen-filled sample decrease compared to the unfilled sample. This is because, based on the weak bond theory, hydrogen weakens the bonding between atoms within the material, reducing the binding energy and thus lowering the material's elastic modulus and hardness. Furthermore, by using different forms of nanoindentation testing, the elastic modulus and hardness of the material under different indentation methods can be analyzed more specifically, thereby obtaining more comprehensive data.

[0045] Furthermore, when performing nanoindentation tests on hydrogen-filled samples, the hydrogen content of the hydrogen-filled material can be adjusted to test the elastic modulus and hardness of hydrogen-filled materials with different hydrogen contents. This allows for a more comprehensive test of the elastic modulus and hardness of materials with different hydrogen contents.

[0046] For example, when controlling the hydrogen content of a material, the specific amount of hydrogen can be selected arbitrarily according to the actual testing requirements. For example, for TC4ELI titanium alloy plates, different hydrogen contents such as 0.06%, 0.16%, 0.22%, 0.28%, and 0.52% can be filled into the material and tested separately. In addition, a control group with 0% hydrogen content can be prepared as a control experiment, so as to more comprehensively test the elastic modulus and hardness of the material under different hydrogen contents.

[0047] Furthermore, the aforementioned materials are not limited to TC4ELI titanium alloy plates. In some embodiments, any hydrogen-related materials involved in the aforementioned hydrogen fuel cell engine can be used as test objects, such as GH4169, GH3044, GH4720Li, GH3536 and 9Cr18Mo, or materials such as 304 stainless steel, 316 stainless steel and 321 austenitic stainless steel.

[0048] Furthermore, in step S3 above, the method also includes the following steps.

[0049] S31, define multiple target points arranged at intervals on the surface to be tested.

[0050] S32, the pressure head moves to each target point in a preset order, and performs a downward press and upward lift once when it moves to each target point, so as to form multiple pressure points arranged at intervals.

[0051] Through the above steps S31 and S32, that is, the process of using an indenter to perform indentation testing on the sample, conductive powder is embedded in the sample surface to be tested and polished. Target points can be defined in advance to determine the test position. Then, when the indenter moves to each target point, it performs one downward press and one upward press. This process is the process of pressing down with the indenter at different rates in the above-mentioned nanoindentation test. Specifically, the indenter can be a diamond indenter commonly used in nanoindentation tests. Diamond has advantages such as high hardness, high elastic modulus, low coefficient of thermal expansion, high thermal conductivity, and strong chemical inertness. Alternatively, the indenter can also be made of one of the following hard materials: sapphire, tungsten carbide, and cubic boron nitride.

[0052] Furthermore, the shape of the aforementioned indenter can be selected arbitrarily according to the actual situation. For example, GB / T22458-200 specifies the commonly used indenters for nanoindentation testing, and any one or more of these indenters can be used, such as glass indenters, cubic indenters, Vickers indenters, conical indenters, or spherical indenters. In this test, glass indenters are generally used for testing.

[0053] Furthermore, by combining the above-mentioned pressure application through a glass indenter to multiple target points, the test results can be obtained by combining the data from multiple pressure points, and the average or median values ​​can be selected, which can improve the accuracy of the test results.

[0054] Furthermore, in step S31 above, the method also includes the following steps.

[0055] S311, nine target points are defined on the surface to be measured, and the nine target points are arranged in a 3×3 matrix on the surface to be measured.

[0056] Because the load-depth curves obtained in actual nanoindentation tests inevitably contain deviations, the elastic modulus and hardness measured by the Oliver-Pharr method also deviate from the true values. According to ISO 14577-1:2015, at least five indentation tests should be performed on macroscopic samples; at least 15 tests should be performed on microscopic and nanoscopic samples to improve the reliability and repeatability of the average measurement. GB / T 22458-2008 recommends performing at least ten tests on each standard sample under each test load to reduce the uncertainty of the average measurement. A 3×3 or 4×4 matrix indentation is recommended.

[0057] This can be understood as follows: on a macroscopic scale, the pressing test should not be less than five times. Therefore, in the specific testing process of this embodiment, a 3×3 matrix pressing can be performed according to the above standard, that is, nine target points can meet the most basic testing requirements. More specifically, in addition to using 3×3, in order to further improve the accuracy of the test results, a 4×4 matrix pressing can also be used, that is, a test method with a total of 16 target points.

[0058] Furthermore, in step S32 above, the method also includes the following steps.

[0059] S321 ensures that the spacing between any two adjacent indentations on the surface to be tested is 20 times the indentation depth.

[0060] Through the above S321 step, any two adjacent pressure points can maintain a sufficient distance on the surface to be tested, thereby avoiding interference caused by the two pressure points being too close together, and thus improving the accuracy of the test results. Specifically, the pressure spacing can generally be selected to be more than 20 times the maximum pressure depth. For example, when the above spacing is 20μm, the maximum pressure depth can be 1μm.

[0061] Furthermore, in step S32 above, the method also includes the following step: controlling the pressure head to hold the load for a preset time when pressing down to each target point.

[0062] In the above manner, the load holding preset time corresponds to the time after the indenter contacts the surface of the sample under test with a preset force. By holding the load preset time, the time-related deformation process of the sample under test can be reduced, specifically including, for example, the influence of hysteresis that can be slowly recovered after unloading and creep that cannot be recovered on the test results.

[0063] Furthermore, in step S32 above, the pressure head is pressed down at a constant speed and raised at a constant speed.

[0064] By maintaining a constant downward and upward speed of the indenter, the accuracy of the test results during nanoindentation testing of materials can be further improved. That is, there will be no sudden increase or decrease in the speed of the indenter during the constant downward and upward speed, which improves the safety and accuracy of the test results during the nanoindentation test.

[0065] Furthermore, in step S1 above, the method also includes the following steps.

[0066] S11, the samples are divided into two groups, and both groups are evacuated using a gas phase hydrogen charging device.

[0067] S12, heat the sample to the preset temperature.

[0068] S13, one group of samples is filled with hydrogen gas at a preset concentration, and the other group of samples is filled with inert gas at a preset concentration.

[0069] S14, the two sets of samples are cooled to obtain hydrogen-filled samples and non-hydrogen-filled samples.

[0070] The above method, i.e., the hydrogen charging process for sample pretreatment, involves placing the two sets of samples separately into the vacuum chamber inside the gas-phase hydrogen charging device and then evacuating them. The purpose of evacuation is primarily to prevent interference from other gaseous media during the hydrogen charging process and to prevent dangerous accidents such as hydrogen explosions. Generally, the pressure inside the vacuum chamber can be evacuated to [a certain level]. Pa is used to meet the vacuum conditions; then the two sets of samples in the vacuum chamber are heated to a preset temperature. The preset temperature can be understood as the temperature corresponding to the actual working process of the sample. For example, after heating the material to the preset temperature, one set of samples is filled with hydrogen gas of a preset concentration as the experimental group, and the amount of hydrogen gas filled can be 20 kPa. The other set of samples is filled with inert gas of a preset concentration as the control group, and the amount of inert gas filled can be 20 kPa. The filling with inert gas mainly takes advantage of the chemical inertness of inert gas. Compared with the material being directly heated and cooled in the air, the material is prone to oxidation, decarburization and other problems, which affect the material performance and thus the test results. Therefore, the inertness of inert gas can be used for protection. The inert gas can be a rare gas composed of any element such as helium, neon, argon, krypton, xenon, etc. Preferably, the inert gas in this embodiment can be argon gas, because the content of argon gas in the atmosphere is higher than that of other rare gases, so it is easier to obtain.

[0071] The heating process described above can be achieved using heating tubes or similar devices, which can heat the sample inside the vacuum chamber through thermal radiation.

[0072] Furthermore, the heating process described above can help the hydrogen-filled sample to better combine with hydrogen, thereby more realistically simulating the scenario of materials combining with hydrogen at high temperatures and improving the accuracy of test results.

[0073] After both sets of samples are heated, they can be cooled to room temperature by standing for 1 to 2 hours. Then, the hydrogen gas inside the chamber containing the hydrogen-filled sample is extracted, and the argon gas is filled in. When the chamber containing both sets of samples is kept at the same pressure as the outside atmospheric pressure, the samples can be taken out, thus obtaining hydrogen-filled and non-hydrogen-filled samples.

[0074] Furthermore, this embodiment provides a detailed description of the specific calculation process of the Oliver-Pharr method described above, as exemplarily shown below.

[0075] The load-depth curve of the tested sample was obtained based on the test results of the nanoindenter, and the maximum indentation load was extracted. Maximum indentation depth and residual indentation depth The data points at the top of the unloading curve are fitted using a power-law function (generally only the top 25%~50% of the elastic segment is used), and the fitting coefficients B and b are obtained. Then, the contact stiffness S and contact depth are calculated sequentially. and contact projected area Finally, the reduced modulus was calculated. The elastic modulus E and hardness H of the material being tested.

[0076] Specifically, the aforementioned contact stiffness S can be achieved through... The calculation yielded the result.

[0077] Once the contact stiffness S is obtained, the contact depth can be calculated accordingly. Specifically, it can be done through The calculation yielded the result.

[0078] Get contact depth Then, the contact projection area can be calculated accordingly. Specifically, it can be done through The calculation shows that, It can be understood as the indenter shape constant, which can be determined by referring to the record in GB / T22458-2008.

[0079] Get the contact projection area Then, the equivalent modulus can be calculated accordingly. And hardness H, where the reduced modulus can be obtained through Calculations show that β is a correction factor; hardness can be achieved through... The calculation yielded the result.

[0080] The reduced modulus calculated above Furthermore, the elastic modulus E can be calculated, specifically, by... The calculation yields the result; where v can be interpreted as the Poisson's ratio of the sample. This can be understood as the Poisson's ratio of the pressure head. This can be understood as the elastic modulus of the indenter.

[0081] It should be noted that the above calculation rules are exemplary. For specific calculation methods, please refer to GB / T22458-2008 to obtain the above elastic modulus and hardness.

[0082] A second aspect of the present invention provides a gas-phase hydrogen charging device, as described above. Figure 2 As shown, the gas phase device can be applied to the method for obtaining the elastic modulus and hardness of the sample mentioned in the above embodiments. The gas phase hydrogen charging device includes a receiving cavity 1, a vacuum pump 2, a heater 3, a first gas cylinder 4, and a second gas cylinder 5. The receiving cavity 1 is used to contain the sample; the vacuum pump 2 is connected to the receiving cavity 1; the heater 3 is connected to the receiving cavity 1; the first gas cylinder 4 stores hydrogen and is connected to the receiving cavity 1; the second gas cylinder 5 stores inert gas and is connected to the receiving cavity 1.

[0083] In the above manner, this gas-phase hydrogen charging device can charge the sample with hydrogen, and can also charge the control group sample with inert gas. Specifically, refer to... Figure 2As shown, the gas-phase hydrogen charging device may further include a first shut-off valve 6 installed on the pipeline between the first gas cylinder 4 and the second gas cylinder 5 and the receiving cavity 1, and a second shut-off valve 7 installed between the receiving cavity 1 and the vacuum pump 2. A third shut-off valve 8 is also installed between the first gas cylinder 4 and the receiving cavity 1, located before the first shut-off valve 6. A fourth shut-off valve 9 is also installed between the second gas cylinder 5 and the receiving cavity 1, located before the first shut-off valve 6. The entire hydrogen charging process using this gas-phase hydrogen charging device can be as follows: For samples requiring hydrogen charging, during vacuuming, the first shut-off valve 6 can be closed, and the second shut-off valve 7 can be opened. By starting the vacuum pump 2, excess air in the receiving cavity 1 is removed, allowing the receiving cavity 1 to be in a vacuum state. Then, the second shut-off valve 7 can be closed, sealing the space of the receiving cavity 1. The receiving cavity 1 is then heated by the heater 3 to a preset temperature. After reaching the required temperature, a preset amount of hydrogen can be injected into the containment cavity 1 through the first gas cylinder 4 by opening the first shut-off valve 6 and the fourth shut-off valve 9. Once the amount of hydrogen meets the filling requirements, the first shut-off valve 6 and the fourth shut-off valve 9 are closed. After the sample and hydrogen have fully fused and reacted, the heating of the heater 3 is stopped. After the sample in the containment cavity 1 is cooled to room temperature, the second shut-off valve 7 is opened, and the remaining hydrogen in the containment cavity 1 is extracted by starting the vacuum pump 2. Then, the third shut-off valve 8 and the first shut-off valve 6 are opened, and a preset amount of inert gas, such as argon as mentioned in the above embodiment, is filled into the containment cavity 1 through the second gas cylinder 5. The purpose of filling with argon is to prevent dangerous situations such as explosions caused by hydrogen coming into contact with air when the sample is taken directly from the containment cavity 1. When the pressure in the containment cavity 1 is consistent with the outside pressure, the hydrogen-filled sample can be taken out from the containment cavity 1.

[0084] In related technologies, electrochemical hydrogen charging is commonly used, but this method is prone to drawbacks such as uneven hydrogen distribution and potential introduction of electrochemical noise. The aforementioned gas-phase hydrogen charging device, however, offers advantages such as highly controllable hydrogen charging volume, more uniform hydrogen distribution, and the ability to realistically simulate a high-temperature, high-pressure hydrogen environment.

[0085] In the above embodiments, the receiving cavity 1 may be provided with a closed door, that is, when the sample is placed in, the sample can be placed into the receiving cavity 1 by opening the door, and when the sample is taken out, the sample inside can also be taken out by opening the door.

[0086] The heater 3 can be any suitable type, such as a resistance heater, an electromagnetic heater, or an infrared radiation heater. By attaching the heater 3 to the outer wall of the receiving cavity 1, heat can be transferred to the receiving cavity 1, thereby heating the sample inside the receiving cavity 1.

[0087] The opening and closing of the shut-off valve, the start and stop of the vacuum pump 2, and the start and stop of the heater 3 can all be achieved through the control panel 10. Specifically, the control panel 10 can be a remote PC or a suitable control method such as a PLC to control the operation of the above components.

[0088] For the control group, i.e., the uncharged sample, the same gas-phase hydrogen charging device can be used for complete control. The specific operation is as follows: first, place the sample in the containment chamber 1, close the first shut-off valve 6, open the second shut-off valve 7, and start the vacuum pump 2 to remove excess air from the containment chamber 1, so that the containment chamber 1 can be in a vacuum state. Then, close the second shut-off valve 7 to seal the space of the containment chamber 1. Then, heat the containment chamber 1 with the heater 3. After heating to the preset temperature, open the first shut-off valve 6 and the third shut-off valve 8, and fill the containment chamber with argon gas through the second gas cylinder 5. When the pressure in the containment chamber 1 is consistent with the outside pressure, the hydrogen-charged sample can be taken out from the containment chamber 1.

[0089] Furthermore, you can refer to Figure 2 As shown, the gas phase hydrogen charging device may also include a vacuum gauge 11 installed on the pipeline corresponding to the first shut-off valve 6. The vacuum gauge 11 can monitor the pressure in the containment cavity 1 in real time, and thus obtain the vacuum state in the containment cavity 1.

[0090] Furthermore, refer to Figure 2 As shown, the gas phase hydrogen charging device may also include a hydrogen leak alarm 12 connected to the containment cavity 1. The hydrogen leak alarm 12 can measure the hydrogen content in the containment cavity 1 in real time, and can determine the leakage amount by the pressure drop rate inside the containment cavity 1 when hydrogen leaks. For example, it can be monitored in real time by a pressure sensor or other device. When the leakage amount exceeds the preset range, it can also trigger an alarm function, thereby improving the safety of the gas phase hydrogen charging device.

[0091] The first gas cylinder 4, the second gas cylinder 5, and the receiving cavity 1 can be connected together via a three-way pipe, as shown in the reference. Figure 2 As shown, the first shut-off valve 6 can be set on the side of the three-way pipeline near the receiving cavity 1, the third shut-off valve 8 can be set on the side of the three-way pipeline near the second gas cylinder 5, and the fourth shut-off valve 9 can be set on the side of the three-way pipeline near the first gas cylinder 4.

[0092] The vacuum pump 2 and the receiving cavity 1 can also be connected by a pipeline. The second shut-off valve 7 can be set on the pipeline between the vacuum pump 2 and the receiving cavity 1 to play the role of switching on and off.

[0093] Taking TC4ELI titanium alloy, a typical material for hydrogen-related components, as an example, refer to... Figure 3 and Figure 4As shown, using the gas-phase hydrogen charging device proposed in this invention, samples with hydrogen charging amounts of 0%, 0.06%, 0.16%, 0.22%, 0.28%, and 0.52% were obtained. Secondary mass spectrometry was used to characterize the aggregation and distribution of hydrogen and hydrides within these samples. Figure 4 As can be seen, after hydrogenation, hydrogen mainly accumulates in the β phase and grain boundaries where hydrogen solubility is high, and hydrides precipitate. At the same time, the thickness of the β phase lamellars increases. This is because, with the increase of hydrogen content, hydrogen atoms diffuse from the hydrogen-rich β phase to the hydrogen-poor α phase. Meanwhile, the β phase transformation temperature decreases, causing the α phase to transform into the β phase and needle-like α' phase, and δ hydrides precipitate.

[0094] Taking TC4ELI titanium alloy, a typical material for hydrogen-related components, as an example, the above-mentioned nanoindentation test was used to obtain the mechanical response of unfilled and hydrogen-filled nanoindentations. Figures 5 to 10 As shown, from Figure 5 and Figure 6 As can be seen, the load-depth curve shifts to the right after hydrogen filling. Under the same load level, the hydrogen-filled sample has a greater indentation depth, indicating a softening phenomenon after hydrogen filling, with a corresponding decrease in both elastic modulus and hardness. Based on the weak bond theory, hydrogen weakens the bonding between atoms within the material, reducing the binding energy and thus decreasing the elastic modulus.

[0095] from Figure 7 As can be seen, under micro-load, the loading curves of both unhydrogenated and hydrogen-filled TC4ELI titanium alloys showed obvious displacement abrupt changes, reflecting the transition from elastic to elastoplastic. Hydrogen filling caused the load to decrease from 107μN to 58μN, that is, hydrogen reduced the load required for plastic deformation. This is because hydrogen promotes dislocation nucleation, emission and multiplication.

[0096] refer to Figure 8 It can be seen that the loading rate has a relatively small effect on the load-depth curve of the unhydrogen-charged TC4ELI titanium alloy. As the loading rate (the rate at which the load is applied) decreases, the curve in the loading stage shifts slightly to the right. This is because at a lower loading rate, creep deformation can occur sufficiently during a long period of slow loading, and a lower loading load means a smaller indentation depth. In this case, even a slight creep deformation cannot be ignored compared to the indentation depth, hence the slight rightward shift of the loading curve. On the other hand, the above situation, in turn, weakens the creep deformation in the holding load stage. Therefore, the lower the loading rate, the smaller the creep depth in the holding load stage, but the overall maximum depth still increases. Figure 9 As shown, an increase in maximum depth, i.e., an increase in the indentation contact projection area, results in a decrease in measured hardness, while the change in elastic modulus is relatively small. Figure 10 As shown. For hydrogen-filled TC4ELI titanium alloy, it is... Figure 8It can be seen that as the loading rate decreases from 1 mN / s to 0.1 mN / s, the loading curve shifts significantly to the right. However, when the loading rate decreases to 0.05 mN / s, the loading curve shifts to the left, and its maximum depth is even lower than the maximum depth at 1 mN / s. The former is due to softening under the combined effects of hydrogen charging. The lower the loading rate, the longer the time for dislocations to move on the slip surface and generate plastic strain. The more significant the indentation elastic-plastic deformation and creep deformation after softening, the more significant the maximum depth, and the significantly lower the elastic modulus and hardness. Similarly, the creep deformation in the holding load stage is weakened and reduced, but it is still greater than the creep depth of the un-hydrogen-charged TC4ELI titanium alloy, i.e., as shown... Figure 9 and Figure 10 As shown. The latter is due to the influence of hydrides. At ultra-low loading rates, hydrogen atoms dissolved near the tip of the indenter have sufficient time to diffuse and accumulate, precipitating new δ-hydrides after reaching a critical value. The hard and brittle δ-hydrides hinder dislocation movement, significantly reducing both indentation elasto-plastic deformation and creep deformation, leading to a decrease in maximum depth and creep depth during the holding load stage. Therefore, the elastic modulus and hardness are significantly improved.

[0097] Based on the above analysis, hydrogen weakens the atomic bonding forces within the material, leading to a decrease in elastic modulus and hardness; hydrogen promotes the nucleation, emission, and multiplication of dislocations, resulting in a decrease in the load required for plastic deformation; at ultra-low loading rates, hydrogen has sufficient time to diffuse, enrich, and precipitate new hydrides to hinder dislocation movement, resulting in a significant increase in elastic modulus and hardness.

[0098] Therefore, the method for obtaining the elastic modulus and hardness of the sample and the gas-phase hydrogen charging device proposed in this invention can more comprehensively characterize the hydrogen embrittlement of materials in nanoindentation tests, obtain indentation parameters that are strongly correlated with the hydrogen embrittlement mechanism, and provide key experimental evidence for distinguishing different hydrogen embrittlement mechanisms.

[0099] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope of protection claimed by the present invention.

Claims

1. A method for obtaining the elastic modulus and hardness of a sample, characterized in that, include: The samples were divided into hydrogen-filled samples and non-hydrogen-filled samples; Conductive powder is embedded in the bottom of the hydrogen-filled sample and the non-hydrogen-filled sample, and the test surfaces of the hydrogen-filled sample and the non-hydrogen-filled sample are polished to obtain hydrogen-filled sample and non-hydrogen-filled sample. Nanoindentation tests were performed on the surface to be tested to obtain the load-depth curves of the hydrogen-filled sample and the unfilled sample. Based on the load-depth curve, the elastic modulus and hardness of the hydrogen-filled sample and the unfilled sample were calculated. The nanoindentation tests include standard nanoindentation tests, microload nanoindentation tests, and variable rate nanoindentation tests.

2. The method for obtaining the elastic modulus and hardness of a sample according to claim 1, characterized in that, Nanoindentation tests are performed on the surface to be tested to obtain load-depth curves for the hydrogen-filled sample and the unfilled sample, including: Multiple target points are defined at intervals on the surface to be tested; The pressure head is moved one by one to each of the target points in a preset order, and a downward pressure and upward lifting are performed when it moves to each target point to form multiple pressure points arranged at intervals.

3. The method for obtaining the elastic modulus and hardness of a sample according to claim 2, characterized in that, Multiple target points are defined at intervals on the surface to be tested, including: Nine target points are defined on the surface to be tested, and the nine target points are arranged in a 3×3 matrix on the surface to be tested.

4. The method for obtaining the elastic modulus and hardness of a sample according to claim 2, characterized in that, The pressure head moves sequentially above each target point in a preset order, performing a downward press and an upward lift upon reaching each target point to form multiple spaced pressure points, including: The spacing between any two adjacent indentations on the surface to be tested is such that the distance between them is 20 times the indentation depth.

5. The method for obtaining the elastic modulus and hardness of a sample according to claim 2, characterized in that, The pressure head is moved sequentially to each target point in a preset order, and a downward and upward motion is performed each time it reaches a target point to form multiple spaced pressure points. The method also includes: The pressure head is controlled to maintain a preset load for a certain time when it is pressed down to each of the target points.

6. The method for obtaining the elastic modulus and hardness of a sample according to claim 1, characterized in that, The samples were divided into hydrogen-charged samples and non-hydrogen-charged samples, including: The samples were divided into two groups, and both groups of samples were evacuated using a gas phase hydrogen charging device. Heat the sample to a preset temperature; One set of the samples is filled with hydrogen gas at a preset concentration, and the other set of the samples is filled with inert gas at a preset concentration. The two sets of samples were cooled to obtain hydrogen-filled samples and non-hydrogen-filled samples.

7. The method for obtaining the elastic modulus and hardness of a sample according to claim 6, characterized in that, The inert gas is argon.

8. The method for obtaining the elastic modulus and hardness of a sample according to claim 2, characterized in that, In the process of moving the pressure head sequentially above each target point in a preset order, and performing a downward press and an upward lift once upon reaching each target point, multiple pressure points are formed at intervals: The pressure head is a glass pressure head.

9. The method for obtaining the elastic modulus and hardness of a sample according to claim 2, characterized in that, The pressure head moves sequentially above each target point in a preset order, performing a downward press and an upward lift upon reaching each target point to form multiple spaced pressure points, including: The pressure head is pressed down and lifted at a constant speed.

10. A gas-phase hydrogen charging device, characterized in that, A method for obtaining the elastic modulus and hardness of a sample according to any one of claims 1-9, characterized in that the gas-phase hydrogen charging device comprises a receiving cavity (1), a vacuum pump (2), a heater (3), a first gas cylinder (4), and a second gas cylinder (5), wherein: The receiving cavity (1) is used to hold the sample; The vacuum pump (2) is connected to the receiving cavity (1) via a pipeline. The heater (3) is connected to the receiving cavity (1); The first gas cylinder (4) contains hydrogen gas and is connected to the receiving cavity (1); The second gas cylinder (5) contains inert gas and is connected to the receiving cavity (1).

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