Method for rapidly optimizing components and heat treatment of super martensitic stainless steel

Abstract

The invention discloses a method for rapidly optimizing components and heat treatment of super martensitic stainless steel, and relates to the technical field of material research methods.The method comprises the steps that firstly, a wide component FCC phase region of a stainless steel system is determined according to a phase diagram calculation result, end component components are determined, and then two end components are obtained through smelting and linear cutting in sequence; and fixing the two end components together, annealing and carrying out subzero treatment to obtain a super martensitic stainless steel diffusion couple, and finally carrying out component gradient analysis and hardness and Young modulus test on the diffusion couple to obtain the corresponding relationship among the components, hardness and Young modulus of the stainless steel under different heat treatments. Therefore, the composition of the high-hardness super martensite and corresponding heat treatment parameters are determined. A large amount of approximately continuous phase composition-component-heat treatment-hardness-Young modulus corresponding experimental data information can be obtained in a short time, and the high-performance martensitic stainless steel and heat treatment parameters thereof can be quickly optimized.

Description

Technical Field

[0001] This invention relates to the field of materials research methods, specifically a method for rapidly optimizing the composition and heat treatment of super martensitic stainless steel. Background Technology

[0002] Oil and gas field extraction conditions are becoming increasingly demanding, placing extremely high requirements on the strength and corrosion resistance of well tubing materials. Currently, China relies heavily on imported nickel-based alloys, but their high price and the impact of rising nickel raw material costs have significantly increased costs. Therefore, developing high-strength, high-corrosion-resistant materials has become an urgent need in the oil and gas field equipment sector.

[0003] Super martensitic stainless steel has attracted attention and seen some applications in the oil and gas sector due to its numerous superior properties, but oil and gas companies are placing higher demands on its strength. Developing new high-performance martensitic stainless steels to replace traditional nickel-based alloys is a current hot topic and key focus in the petroleum industry, with significant economic and social benefits; therefore, researching and developing such steels and corresponding heat treatment processes is essential.

[0004] Furthermore, determining the appropriate composition and processing parameters for hardness and Young's modulus in martensitic stainless steel systems is a crucial research task. Traditional alloy development primarily involves testing the material properties of individual composition samples one by one, followed by comparative analysis to select the stainless steel with the best performance and corresponding processing parameters. This method requires significant manpower and resources for a large number of experiments and struggles to guarantee the rigor of experimental conclusions. Moreover, the limited number of experimental sites results in a lack of comprehensive and systematic understanding of the supermartensitic stainless steel system, leading to bottlenecks in related fundamental theoretical research and product development. Therefore, efficiently and quickly acquiring experimental data on the composition, hardness, and Young's modulus of supermartensitic stainless steel under different processing conditions, and rapidly screening for high-performance supermartensitic stainless steel compositions and their heat treatments, is of significant and far-reaching importance for the development of new high-performance stainless steels and the understanding of related mechanisms.

[0005] Therefore, a method for rapidly optimizing the composition and heat treatment of super martensitic stainless steel is proposed to solve the above problems. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to propose a method for rapidly optimizing the composition and heat treatment of super martensitic stainless steel. This method is an efficient way to study the composition, hardness and Young's modulus of stainless steel systems. It can obtain the gradient change bonding region of the interface of different alloy compositions on a single sample, thereby obtaining the hardness and Young's modulus data of multiple stainless steel system compositions, and finally obtaining the composition and heat treatment parameters of super martensitic stainless steel with good comprehensive performance.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for rapidly optimizing the composition and heat treatment of super martensitic stainless steel, comprising:

[0008] S1. The two terminal components of the diffusion couple under study are determined by phase diagram calculation.

[0009] S2. Prepare a stainless steel ingot with two end-point components, then wire cut the stainless steel ingot to obtain a uniform block in the core, grind and polish the block, clean the surface of the block, and obtain the two end-point components of the diffusion couple.

[0010] S3. Fix the two end-point components prepared in S2 together, seal them in a vacuum container containing sponge titanium or sponge yttrium, and perform high-temperature solution annealing. After annealing, take out the block that has been fixed together and cool it to obtain a diffusion couple.

[0011] S4. Place the diffusion couple in liquid nitrogen for cryogenic treatment, seal it in a vacuum container containing sponge titanium or sponge yttrium, and perform tempering treatment to obtain the final diffusion couple sample.

[0012] S5. Perform microstructure and composition gradient analysis, as well as hardness and Young's modulus tests on the obtained diffusion couples to obtain batch experimental data on the composition, process, hardness, and Young's modulus of super martensitic stainless steel. Finally, determine the composition and process of high-performance super martensitic stainless steel based on the changes in hardness and Young's modulus.

[0013] Preferably, the determination of the two end-component components of the diffusion couple to be studied in S1 includes calculating the correlation diagram of alloys with different compositions for the multi-component system; then, in the composition-temperature phase diagram, isothermal section diagram, or correlation diagram of alloys with different compositions, determining the region where the FCC single phase has an iron mass percentage higher than 60%, and taking the composition values ​​corresponding to the two stainless steels with the largest composition difference in this region, that is, the two endpoint values ​​when the stainless steel composition gradient is the largest, which are the two end-component components of the diffusion couple to be studied.

[0014] Preferably, the preparation method of the end-point component in S2 includes smelting or a combination of smelting and forging, and the size of the end-point component block does not exceed 10*10*2mm. 3 .

[0015] Preferably, the vacuum degree in the container described in S3 is less than 10 Pa, the temperature of the high-temperature solution annealing is 900-1200℃, the time is 1-10 days, the cooling method is water cooling to room temperature, and the diffusion couple is a combined block of two end components that are tightly attached together without obvious deformation.

[0016] Preferably, the cryogenic treatment in S4 involves immersion in liquid nitrogen for 5 to 30 minutes, with the vacuum level in the container being less than 10 Pa, the tempering temperature being 400 to 800°C for 0.5 to 5 hours, and the cooling method being water cooling to room temperature.

[0017] Preferably, the microstructure analysis described in S5 is performed using an electron probe microanalysis, scanning electron microscope, or three-dimensional atomic probe microanalysis; the composition gradient analysis method is performed using a spectrometer for point analysis or an energy dispersive spectroscopy (EDS) for surface scanning; and the hardness and Young's modulus testing method is nanoindentation.

[0018] As a preferred embodiment, the high-performance super martensitic stainless steel described in S5 comprises, by mass percentage, the following elemental composition: C 0.02-0.04%, Cr 12-18%, Mo 0.5-2%, Ni 4-8%, Cu 0.5-1.5%, and the balance being Fe.

[0019] Preferably, the high-temperature solution annealing temperature in S5 is 900–1100°C, and the treatment time is 4–8 days; the tempering temperature is 550–750°C, and the treatment time is 0.5–2 hours.

[0020] Compared with existing technologies, the present invention provides a method for rapidly optimizing the composition and heat treatment of super martensitic stainless steel, which has the following beneficial effects:

[0021] 1. Significantly improves R&D efficiency and reduces overall costs;

[0022] Current technologies require the preparation and testing of numerous single-component samples one by one, which is time-consuming, labor-intensive, and produces discrete data. This invention, through diffusion couple technology, requires only the preparation of two end-components. After high-temperature annealing and cryogenic treatment, a continuous gradient distribution of composition (gradient region > 50 μm) can be obtained on a single sample. Combined with nanoindentation and other techniques, batch data on composition, hardness, and Young's modulus can be obtained in one go (e.g., Figure 4 (8 / 12). Compared to the traditional "single-point experiment" model, the R&D cycle is shortened by more than 90%, and the costs of manpower, material resources and time are greatly reduced.

[0023] 2. Scientific material selection design based on phase diagram calculations;

[0024] Existing technologies rely on trial and error based on experience, and the selection of components lacks theoretical guidance. This invention, however, innovatively employs thermodynamic phase diagram calculation software (such as THERMO-CALC or Pandat) to accurately locate the FCC single-phase region within the iron-based content range >60%, and selects the two endpoints with the greatest compositional differences. For example… Figure 1As shown in / 5 / 9, the terminal components are determined by the Cr content-temperature phase diagram, ensuring that the diffusion couple covers the maximum composition gradient range, providing a scientific basis for composition optimization and avoiding blind experiments.

[0025] 3. Cryogenic treatment ensures data comparability and tissue homogeneity;

[0026] Traditional heat treatment often leads to grain coarsening, affecting the accuracy of performance testing. This invention introduces liquid nitrogen cryogenic treatment for 5-30 minutes after high-temperature solution annealing (900–1200℃, 1–10 days) to refine the grains to near their initial state. Comparative Example 2 verifies that without cryogenic treatment, abnormal grain growth and reduced hardness occur. Combined with a vacuum environment and titanium sponge / yttrium deoxidation, oxidation burn-off and porosity cracks (such as…) are effectively suppressed. Figure 2 (6 / 10) ensures the integrity of the diffusion interface, and the obtained data is directly comparable to that of single-component samples.

[0027] 4. Achieve high-throughput continuous data acquisition and multidimensional correlation analysis;

[0028] Existing technologies are limited by discrete experimental points, making it difficult to systematically establish the composition-process-performance mapping relationship. This invention, through the continuous gradient characteristics of diffusion couples, combined with electron probe microanalysis of compositional planes and nanoindentation micro-area testing, obtains an approximately continuous composition-hardness-Young's modulus correspondence curve in a single step, such as... Figure 4 / 8 / 12; For example, in Example 1, an optimized composition (Cr16%) with a hardness of 4.1 GPa and a modulus of 214 GPa was screened out in a single experiment, providing an efficient means to establish a material performance database.

[0029] 5. Clearly define and optimize the component window and process parameters to achieve performance breakthroughs;

[0030] Traditional methods struggle to precisely pinpoint the optimal process range. This invention utilizes high-throughput diffusion couple screening to determine the composition of high-performance super martensitic stainless steel as: C 0.02–0.04%, Cr 12–18%, Mo 0.5–2%, Ni 4–8%, and Cu 0.5–1.5%. This is followed by solution annealing at 900–1100℃ for 4–8 days, liquid nitrogen immersion for 5–30 minutes, and tempering at 550–750℃ for 0.5–2 hours. Examples 1-3 validate the results. After optimization, the hardness reaches 3.8–4.1 GPa and the modulus 214–230 GPa, significantly surpassing commercially available 00Cr13Ni5Mo and 316 stainless steel (mentioned in the background art), meeting the high-strength and corrosion-resistant requirements of the oil and gas extraction field. Attached Figure Description

[0031] Figure 1 This is a flowchart of a method for rapidly optimizing the composition and heat treatment of super martensitic stainless steel according to the present invention.

[0032] Figure 2The Cr content-temperature phase diagram for a stainless steel system containing 0.02% C, 1% Mo, 5% Ni, and 1.5% Cu.

[0033] Figure 3 The microstructure of the stainless steel diffusion couple containing super martensitic stainless steel obtained in Example 1;

[0034] Figure 4 The grain orientation of the stainless steel diffusion couple containing supermartensitic stainless steel obtained in Example 1 is shown.

[0035] Figure 5 This is a graph showing the distribution of hardness and Young's modulus of the stainless steel diffusion couple containing super martensitic stainless steel obtained in Example 1 as a function of composition.

[0036] Figure 6 The Cr content-temperature phase diagram for a stainless steel system containing 0.02% C, 1% Mo, and 5% Ni.

[0037] Figure 7 The microstructure of the stainless steel diffusion couple containing super martensitic stainless steel obtained in Example 2;

[0038] Figure 8 The grain orientation of the stainless steel diffusion couple containing super martensitic stainless steel obtained in Example 2;

[0039] Figure 9 This is a graph showing the distribution of hardness and Young's modulus of the stainless steel diffusion couple containing super martensitic stainless steel obtained in Example 2 as a function of composition.

[0040] Figure 10 The Cr content-temperature phase diagram for a stainless steel system containing 0.02% C, 2% Mo, 5% Ni, and 0.04% Mn.

[0041] Figure 11 The microstructure of the stainless steel diffusion couple containing super martensitic stainless steel obtained in Example 3;

[0042] Figure 12 The grain orientation of the stainless steel diffusion couple containing super martensitic stainless steel obtained in Example 3;

[0043] Figure 13 This is a graph showing the distribution of hardness and Young's modulus of the stainless steel diffusion couple containing super martensitic stainless steel obtained in Example 3 as a function of composition.

[0044] Figure 14 The microstructure of the stainless steel diffusion couple containing super-martensitic stainless steel obtained in Comparative Example 1 is shown.

[0045] Figure 15The grain orientation of the stainless steel diffusion couple containing super martensitic stainless steel obtained in Comparative Example 2 is shown. Detailed Implementation

[0046] 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, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0047] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0048] Example 1;

[0049] A method for rapidly optimizing the composition and heat treatment of super martensitic stainless steel includes the following steps:

[0050] S1. Phase diagram calculations were performed on a stainless steel system containing 0.02% C, 1.5% Mo, 5.5% Ni, and 1.5% Cu. The resulting composition-temperature phase diagram is shown below. Figure 1 As shown, one end component was determined to be C 0.02%, Cr 16%, Mo 1.5%, Ni 5.5%, Cu 1.5% by mass, with the balance being Fe. In order to have a wider range of compositional variation, another end component was selected as 316L stainless steel.

[0051] S2. Weigh the raw materials according to the above two end-component ratios and melt them. Cast the molten steel to obtain a stainless steel ingot, and then wire cut the stainless steel ingot to obtain a core size of 10×10×1.5mm. 3 The block was subjected to coarse grinding, fine grinding, ultrasonic cleaning with deionized water and low temperature drying on its surface to obtain the two end components of the diffusion couple.

[0052] S3. Fix the two end components together, seal them in a vacuum container containing sponge titanium or sponge yttrium (vacuum degree below 10 Pa), and anneal them in a muffle furnace at 1000°C. After 7 days, take the quartz tube out of the annealing furnace and place it in ice water. Quickly break the quartz tube to cool the resulting diffusion couple within 1 minute to obtain the diffusion couple.

[0053] S4. Place the diffusion couple in liquid nitrogen for deep cryogenic treatment for 30 minutes, seal it in a vacuum container containing sponge titanium or sponge yttrium, and anneal it in a muffle furnace at 700°C. After 0.5 hours, remove the quartz tube from the annealing furnace and place it in ice water. Quickly break the quartz tube to cool the resulting diffusion couple within 1 minute to obtain the final diffusion couple sample.

[0054] S5. The obtained stainless steel diffusion couple containing super martensitic stainless steel was subjected to coarse grinding, fine grinding, polishing, ultrasonic cleaning with deionized water, and drying. The microstructure and grain orientation were analyzed using scanning electron microscopy. Figure 2 and Figure 3 Electron probe microanalysis was used for quantitative analysis of the compositional gradient distribution, and nanoindentation was used to determine the hardness and Young's modulus distribution. An experimental database corresponding to composition, hardness, and Young's modulus was then established, as shown in Table 1. The curves of hardness and Young's modulus as a function of the diffusion couple composition are shown in Table 1. Figure 5 As shown.

[0055] Table 1 shows the composition, hardness, and Young's modulus of the stainless steel obtained in Example 1;

[0056]

[0057] Depend on Figure 2 The results show that the stainless steel diffusion couple containing supermartensitic stainless steel obtained in Example 1 has no obvious defects, and its composition is uniform without segregation, forming a compositional gradient region exceeding 150 μm. Furthermore, from Figure 4 The results show that the super martensitic stainless steel obtained in Example 1 has a random orientation distribution and no specific grain orientation, which does not lead to obvious anisotropy in the mechanical properties of the material, and the grain size is controlled below 100 μm. By comparing the changes in hardness at different compositions, super martensitic stainless steels with high hardness and Young's modulus (hardness of 4.1±0.3 GPa and Young's modulus of 214±25 GPa) were quickly screened out.

[0058] This embodiment rapidly prepares diffusion pairs with significant compositional differences in elements such as Cr, Cu, Mn, and Ni, guided by phase diagram calculations, forming compositional gradient regions with considerable distances. Furthermore, cryogenic treatment with liquid nitrogen maintains a grain size similar to or lower than the as-cast grain size. Moreover, this embodiment utilizes nanoindentation and electron probe microanalysis to obtain more than 10 sets of effective experimental data on "composition-hardness-Young's modulus," achieving an improvement of more than 9 times compared to traditional single-detection methods. Finally, the composition and specific heat treatment parameters of high-performance supermartensitic stainless steel are determined using hardness and the ratio of Young's modulus to hardness.

[0059] Example 2;

[0060] A method for rapidly optimizing the composition and heat treatment of super martensitic stainless steel includes the following steps:

[0061] S1. Phase diagram calculations were performed on a stainless steel system containing 0.02% C, 1% Mo, and 5% Ni. The resulting composition-temperature phase diagram is shown below. Figure 5As shown, one end component was determined to be C 0.02%, Cr 15%, Mo 1%, Ni 5% by mass percentage, with the balance being Fe. In order to have a wider range of compositional variation, another end component was selected as 316L stainless steel.

[0062] S2. Weigh the raw materials according to the above two end-component ratios and melt them. Cast the molten steel to obtain a stainless steel ingot, and then wire cut the stainless steel ingot to obtain a core size of 10×10×1.5mm. 3 The block was subjected to coarse grinding, fine grinding, ultrasonic cleaning with deionized water and low temperature drying on its surface to obtain the two end components of the diffusion couple.

[0063] S3. Fix the two end components together, seal them in a vacuum container containing sponge titanium or sponge yttrium (vacuum degree below 10 Pa), and anneal them in a muffle furnace at 1100℃. After 5 days, take the quartz tube out of the annealing furnace and place it in ice water. Quickly break the quartz tube to cool the resulting diffusion couple within 1 minute to obtain the diffusion couple.

[0064] S4. Place the diffusion couple in liquid nitrogen for deep cryogenic treatment for 10 minutes, seal it in a vacuum container containing sponge titanium or sponge yttrium, and anneal it in a muffle furnace at 600°C. After 1 hour, remove the quartz tube from the annealing furnace and place it in ice water. Quickly break the quartz tube to cool the resulting diffusion couple within 1 minute to obtain the final diffusion couple sample.

[0065] S5. The obtained stainless steel diffusion couple containing super martensitic stainless steel was subjected to coarse grinding, fine grinding, polishing, ultrasonic cleaning with deionized water, and drying. The microstructure and grain orientation were analyzed using scanning electron microscopy. Figure 7 and Figure 8 Electron probe microanalysis was used for quantitative analysis of the compositional gradient distribution, and nanoindentation was used to determine the hardness and Young's modulus distribution. An experimental database corresponding to composition, hardness, and Young's modulus was then established, as shown in Table 2. The curves of hardness and Young's modulus as a function of the diffusion couple composition are shown in Table 2. Figure 9 As shown.

[0066] Table 2 shows the composition, hardness, and Young's modulus of the stainless steel obtained in Example 2;

[0067] Cr (wt.%) Mn(wt.%) Ni (wt.%) Young's modulus (GPa) Hardness (GPa) 15.04 0.01 5.04 203±4 3.6±0.1 14.97 0.05 5.11 203±4 3.6±0.1 15.11 0.11 5.02 201±6 3.7±0.1 15.18 0.15 4.75 206±5 3.6±0.1 15.24 0.37 4.6 207±3 3.6±0.1 15.29 0.33 4.55 198±4 3.5±0.1 15.32 0.36 4.93 202±1 3.6±0.1 16.02 0.65 5.69 215±27 3.8±0.2 16.65 1.08 8.36 195±19 3.1±0.2 17.26 1.16 9.69 181±6 2.8±0.1 17.48 1.46 10.48 174±17 2.7±0.2 17.89 1.73 11.54 172±3 2.5±0.2 18.08 2.09 11.72 185±5 2.6±0.1 18.79 2.07 11.41 179±3 2.7±0.2 18.66 1.94 11.76 179±1 2.7±0.1 18.66 2.01 11.74 182±2 2.8±0.1 18.62 2.28 11.77 178±3 2.8±0.1 18.83 2.06 12 185±1 2.8±0.1 18.53 2.03 11.93 177±15 2.6±0.4 18.47 2.12 12.22 170±3 2.4±0.1

[0068] Depend on Figure 8The results show that the super martensitic stainless steel obtained in Example 2 has a random orientation distribution and no specific grain orientation, which does not lead to obvious anisotropy in the mechanical properties of the material, and the grain size is controlled below 100 μm. By comparing the changes in hardness at different compositions, super martensitic stainless steels with high hardness and Young's modulus (hardness of 3.8±0.2 GPa and Young's modulus of 215±27 GPa) were quickly screened out.

[0069] This embodiment rapidly prepares diffusion pairs with significant compositional differences in elements such as Cr, Mn, and Ni, guided by phase diagram calculations, forming compositional gradient regions with considerable distances. Furthermore, cryogenic treatment with liquid nitrogen maintains a grain size similar to or lower than the as-cast grain size. Moreover, this embodiment utilizes nanoindentation and electron probe microanalysis to obtain more than 10 sets of "composition-hardness-Young's modulus" experimental data, achieving an improvement of more than 9 times compared to traditional single-detection methods. Finally, the composition and specific heat treatment parameters of high-performance supermartensitic stainless steel are determined using hardness and the ratio of Young's modulus to hardness.

[0070] Example 3;

[0071] A method for rapidly optimizing the composition and heat treatment of super martensitic stainless steel includes the following steps:

[0072] S1. Phase diagram calculations were performed on a stainless steel system containing 0.02% C, 2% Mo, 5% Ni, and 0.4% Mn. The resulting composition-temperature phase diagram is shown below. Figure 9 As shown, one end-point component was determined to be C 0.02%, Cr 14%, Mo 2%, Ni 5%, Mn 0.4% by mass, with the balance being Fe. In order to have a wider range of compositional variation, another end-point component was selected as 316L stainless steel.

[0073] S2. Weigh the raw materials according to the above two end-component ratios and melt them. Cast the molten steel to obtain a stainless steel ingot, and then wire cut the stainless steel ingot to obtain a core size of 10×10×1.5mm. 3 The block was subjected to coarse grinding, fine grinding, ultrasonic cleaning with deionized water and low temperature drying on its surface to obtain the two end components of the diffusion couple.

[0074] S3. Fix the two end components together, seal them in a vacuum container containing sponge titanium or sponge yttrium (vacuum degree below 10 Pa), and anneal them in a muffle furnace at 900°C. After 10 days, take the quartz tube out of the annealing furnace and place it in ice water. Quickly break the quartz tube to cool the resulting diffusion couple within 1 minute to obtain the diffusion couple.

[0075] S4. Place the diffusion couple in liquid nitrogen for cryogenic treatment for 5 minutes, seal it in a vacuum container containing sponge titanium or sponge yttrium, and anneal it in a muffle furnace at 500°C. After 2 hours, remove the quartz tube from the annealing furnace and place it in ice water. Quickly break the quartz tube to cool the resulting diffusion couple within 1 minute, obtaining the final diffusion couple sample.

[0076] Table 3 shows the composition, hardness, and Young's modulus of the stainless steel obtained in Example 3;

[0077]

[0078] S5. The obtained stainless steel diffusion couple containing super martensitic stainless steel was subjected to coarse grinding, fine grinding, polishing, ultrasonic cleaning with deionized water, and drying. The microstructure and grain orientation were analyzed using scanning electron microscopy. Figure 11 and Figure 12 Electron probe microanalysis was used for quantitative analysis of the component gradient distribution, and nanoindentation was used to determine the hardness and Young's modulus distribution. An experimental database corresponding to the composition, hardness, and Young's modulus was then established, as shown in Table 3. The curves of hardness and Young's modulus as a function of the diffusion couple composition are shown in Table 3. Figure 13 As shown.

[0079] Depend on Figure 12 The results show that the super martensitic stainless steel obtained in Example 1 has a random orientation distribution and no specific grain orientation, which does not lead to obvious anisotropy in the mechanical properties of the material, and the grain size is controlled below 100 μm. By comparing the changes in hardness at different compositions, super martensitic stainless steels with high hardness and Young's modulus (hardness of 3.9±0.1 GPa and Young's modulus of 230±30 GPa) were quickly screened out.

[0080] This embodiment rapidly prepares diffusion pairs with significant compositional differences in elements such as Cr, Cu, Mn, and Ni, guided by phase diagram calculations, forming compositional gradient regions with considerable distances. Furthermore, cryogenic treatment with liquid nitrogen maintains a grain size similar to or lower than the as-cast grain size. Moreover, this embodiment utilizes nanoindentation and electron probe microanalysis to obtain more than 10 sets of "composition-hardness-Young's modulus" experimental data, achieving an improvement of more than 9 times compared to traditional single-detection methods. Finally, the composition and specific heat treatment parameters of high-performance supermartensitic stainless steel are determined using hardness and the ratio of Young's modulus to hardness.

[0081] Comparative Example 1;

[0082] The difference between this embodiment and Embodiment 1 is that, after high-temperature annealing in a muffle furnace at 1000°C for 20 hours, the quartz tube was removed from the annealing furnace and placed in ice water, without subsequent deep cryogenic treatment or tempering. This yielded a stainless steel diffusion couple subjected to high-temperature, short-time solution annealing.

[0083] The microstructure of the stainless steel diffusion couple obtained by high-temperature short-time solution annealing in Comparative Example 1 was analyzed by scanning electron microscopy (SEM). Figure 14 .Depend on Figure 14 It is evident that the stainless steel diffusion couple subjected to high-temperature short-time solution annealing exhibits significant gaps at the interface, resulting in a small compositional gradient region. Hardness and Young's modulus were measured using a nanoindenter, and the corresponding experimental data for composition, hardness, and Young's modulus are shown in Table 4.

[0084] Comparative Example 2;

[0085] The difference between this embodiment and Embodiment 1 is that, after high-temperature annealing in a muffle furnace at 1000°C for 14 days, the quartz tube was removed from the annealing furnace and placed in ice water before undergoing subsequent cryogenic treatment and tempering. This resulted in a stainless steel diffusion couple subjected to high-temperature, long-term solution annealing.

[0086] The grain orientation of the stainless steel diffusion couple obtained by high-temperature long-term solution annealing in Comparative Example 2 is shown in the figure. Figure 15 .Depend on Figure 15 It is evident that the stainless steel diffusion couple subjected to high-temperature, long-term solution annealing exhibits abnormally large grains, resulting in a hardness of no more than 3 GPa, significantly lower than that of the as-cast material.

[0087] The super martensitic stainless steels optimized in Examples 1-3 of this invention exhibit high hardness and Young's modulus under corresponding heat treatment parameters, and their values ​​significantly exceed those of commercially available 00Cr13Ni5Mo super martensitic stainless steel and 316 stainless steel, showing broad application prospects as high-performance metallic materials in marine engineering. Comparative Example 1 failed to produce a compositional gradient range exceeding 10 μm at the interface, indicating that the stainless steel diffusion couple requires a relatively long period of high-temperature solution annealing. Furthermore, the annealing time is inversely correlated with the solution temperature; that is, the higher the solution temperature, the shorter the required annealing time, but it still needs to exceed one day. Comparative Example 2, after prolonged high-temperature solution annealing, resulted in abnormally large grain sizes and a significant decrease in material hardness. In conclusion, the high-temperature solution annealing time needs to consider the solution temperature and be controlled within a reasonable range.

[0088] In summary, the rapid optimization method for the composition and heat treatment process of super martensitic stainless steel in this invention is easy to implement, highly efficient, and can significantly save R&D, manpower, and time costs compared to traditional research methods. Furthermore, cryogenic treatment can refine the grains of super martensitic stainless steel subjected to long-term high-temperature solution annealing to approximately the initial state of the material, ensuring the comparability of diffusion couple samples with single-component samples. The screening method for the composition and heat treatment process of high-performance super martensitic stainless steel in this invention can obtain a large amount of nearly continuous experimental data on phase composition, composition, heat treatment process, and hardness in a short time, contributing to a comprehensive and systematic understanding of stainless steel systems.

[0089] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0090] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method of rapidly optimizing the composition and heat treatment of supermartensitic stainless steel, characterized in that, The application relates to a method for preparing a high-performance super martensitic stainless steel. The method comprises the following steps: S1, determining the compositions of two end inter-element components of a diffusion couple to be studied by a phase diagram calculation method; S2, preparing stainless steel ingots of the two end inter-element components, then linearly cutting the stainless steel ingots to obtain uniform blocks of cores, polishing the blocks, cleaning the surface of the blocks, and obtaining the two end inter-element components of the diffusion couple; S3, fixing the two end inter-element components prepared in S2 together, sealing the components into a container with vacuum and sponge titanium or sponge yttrium, and performing high-temperature solid solution annealing treatment, taking out the blocks fixed together after annealing and cooling, and obtaining a diffusion couple; S4, placing the diffusion couple into liquid nitrogen for deep cooling treatment, sealing the diffusion couple into a container with vacuum and sponge titanium or sponge yttrium, and performing tempering treatment, and obtaining a final diffusion couple sample; 2. The method of rapidly optimizing supermartensitic stainless steel composition and heat treatment according to claim 1, characterized in that, S5, performing microstructure structure analysis and composition gradient analysis on the obtained diffusion couple, and testing the hardness and Young's modulus, obtaining batch experimental data of super martensitic stainless steel composition-process-hardness-Young's modulus, and finally determining the composition and process of the high-performance super martensitic stainless steel according to the hardness and Young's modulus variation.

3. The method of rapidly optimizing supermartensitic stainless steel composition and heat treatment according to claim 1, characterized in that: The end component preparation mode described in S2 includes smelting or smelting combined with forging, and the end component block size is not more than 10*10*2mm 3 .

4. The method of rapidly optimizing supermartensitic stainless steel composition and heat treatment according to claim 1, characterized in that: The determination of the two end inter-element components of the diffusion couple to be studied in S1 comprises the following steps: calculating the correlation phase diagram of different component alloys for a multi-element system; then determining the region of the FCC single phase with iron mass percentage higher than 60% in the composition-temperature phase diagram or the isothermal section diagram or the correlation phase diagram of different component alloys, and taking the composition values corresponding to the two stainless steels with the largest composition difference in the region, that is, the two end point values when the composition gradient of the stainless steel is the largest, as the two end inter-element components of the diffusion couple to be studied.

5. The method of rapidly optimizing supermartensitic stainless steel composition and heat treatment according to claim 1, characterized in that: The vacuum degree in the container in S3 is less than 10 Pa, the high-temperature solid solution annealing temperature is 900-1200 DEG C, the time is 1-10 days, the cooling mode is water cooling to room temperature, and the diffusion couple is a combined block with the two end inter-element components closely adhered together without obvious deformation.

6. The method of rapidly optimizing supermartensitic stainless steel composition and heat treatment according to claim 1, characterized in that: The deep cooling treatment in S4 is soaking in liquid nitrogen, the time is 5-30 minutes, the vacuum degree in the container is less than 10 Pa, the tempering temperature is 400-800 DEG C, the time is 0.5-5 hours, and the cooling mode is water cooling to room temperature.

7. The method of rapidly optimizing supermartensitic stainless steel composition and heat treatment according to claim 1, characterized in that: The microstructure structure analysis in S5 is performed by an electron probe, a scanning electron microscope or a three-dimensional atom probe, the composition gradient analysis method is spot analysis by a wave spectrometer or face scanning by an energy spectrometer, and the hardness and Young's modulus testing method is nanoindentation.

8. The method of rapidly optimizing supermartensitic stainless steel composition and heat treatment according to claim 1, characterized in that: The high-performance super martensitic stainless steel in S5 comprises the following element components in percentage by mass: C 0.02-0.04%, Cr 12-18%, Mo 0.5-2%, Ni 4-8%, Cu 0.5-1.5% and the balance of Fe. The high-temperature solid solution annealing temperature in S5 is 900-1100 DEG C, the treatment time is 4-8 days, the tempering temperature is 550-750 DEG C, and the treatment time is 0.5-2 hours.

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