Method for improving high-temperature lead / lead bismuth corrosion resistance of austenitic stainless steel, laser surface modified austenitic stainless steel and application of laser surface modified austenitic stainless steel

Abstract

The invention discloses a method for improving high-temperature lead / lead bismuth corrosion resistance of austenitic stainless steel, laser surface modified austenitic stainless steel and application, and belongs to the technical field of nuclear reactor nuclear material design. The method comprises the following steps that laser with the energy ranging from 0.9 mJ to 56 mJ and the scanning rate ranging from 0.15 mm / s to 3.60 mm / s is used for irradiating the surface of the austenitic stainless steel for the lead-cooled fast reactor, the surface of the austenitic stainless steel is cooled after being melted, the surface organization structure of the austenitic stainless steel is improved, the organization chemical uniformity is improved, grains are refined, and the laser surface modified austenitic stainless steel is obtained. Through laser surface modification, the surface structure uniformity of the austenitic stainless steel is improved, grains are refined, diffusion of surface oxidation elements is accelerated, the growth quality of an oxidation film on the surface of the material is effectively improved, a compact and stable oxidation film is formed on the surface of the material, and a new thought is provided for improving the liquid metal corrosion resistance of the austenitic stainless steel.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear material design for nuclear reactors, and more particularly to a method for improving the high-temperature resistance of austenitic stainless steel to lead / lead-bismuth corrosion, laser surface-modified austenitic stainless steel, and applications thereof. Background Art

[0002] As an energy form with high energy density, cleanliness, and low carbon, nuclear energy plays an indispensable role in the transformation of the energy structure. Among them, the lead-cooled fast reactor, as one of the fourth-generation reactor types, has attracted much attention due to its many advantages such as simple structure, high power density, high conversion ratio, high thermal efficiency, and modularity.

[0003] The structural materials of lead-cooled fast reactors must operate reliably in environments of high temperature, high irradiation, and strong corrosion. Among them, corrosion problems are the main factors restricting the development of lead-cooled fast reactors. Martensitic steels are widely used in the manufacture of reactor structural materials due to their excellent neutron irradiation resistance and fracture toughness. Initially, T91 and other F / M steel grades were recommended for building the core interior of lead-cooled fast reactors and other transmutation systems. However, due to the irradiation embrittlement effect of martensitic steels and the long-term creep performance being questioned, the use temperature is ultimately limited. To improve the thermal conversion efficiency of lead-cooled fast reactors, it is necessary to increase the operating temperature. Austenitic stainless steel has more excellent high-temperature mechanical properties and has become a candidate structural material. However, the Ni content in austenitic stainless steel is very high, and the selective leaching of elements in a liquid lead or lead-bismuth environment results in poor resistance to lead or lead-bismuth corrosion.

[0004] Currently, promoting the formation of a protective oxide film on the material surface by controlling the oxygen content in the system is an important method to effectively improve the lead-bismuth corrosion resistance of materials. However, this method has high requirements for the thickness and compactness of the oxide film on the material surface. In an oxygen-controlled environment, untreated austenitic stainless steel can spontaneously form a protective oxide film. However, the grain size differences and uneven distribution of chemical components existing in the manufacturing process pose challenges to the uniformity and integrity of the oxide film. These non-uniformities lead to inconsistent thickness and poor compactness of the protective layer, and thus form weak links in local areas, affecting the overall corrosion resistance of the material. How to improve the surface microstructure of the material to improve the compactness and uniformity of the oxide film on the material surface is the key to enhancing its corrosion resistance. Summary of the Invention

[0005] In view of the above problems, the present invention provides a method for improving the high-temperature resistance of austenitic stainless steel to lead / lead-bismuth corrosion. The present invention uses the method of laser remelting to improve the corrosion resistance of the surface of austenitic stainless steel by enhancing the chemical uniformity of the structure and refining the grains.

[0006] The object of the present invention is to provide a method for improving the high-temperature resistance of austenitic stainless steel to lead / lead-bismuth corrosion, comprising the following steps:

[0007] The surface of austenitic stainless steel for lead-cooled fast reactors is irradiated with a laser having an energy of 0.9 mJ to 56 mJ and a scanning rate of 0.15 mm / s to 3.60 mm / s. After the surface of the austenitic stainless steel melts and then cools, the surface microstructure of the austenitic stainless steel is improved, the tissue chemical uniformity is enhanced, and the grains are refined, resulting in laser surface modified austenitic stainless steel.

[0008] The laser surface modified austenitic stainless steel prepared by the present invention forms an oxide film during the corrosion process, improving the corrosion resistance of the austenitic stainless steel in a lead or lead-bismuth environment at 600 °C to 650 °C.

[0009] For example, the energy is 0.9 mJ, 2 mJ, 8 mJ, 16 mJ, 32 mJ, 48 mJ, 56 mJ, etc., and the scanning rate is 0.15 mm / s, 0.3 mm / s, 0.6 mm / s, 1.0 mm / s, 1.6 mm / s, 3.6 mm / s, etc. However, it is not limited to the listed values, and other unlisted values within the above numerical ranges are equally applicable.

[0010] In a preferred embodiment of the present invention, the laser energy range is 0.9 mJ to 7.6 mJ.

[0011] In a preferred embodiment of the present invention, the laser energy is 7.6 mJ.

[0012] In a preferred embodiment of the present invention, the laser scanning rate is 2.25 mm / s to 2.75 mm / s.

[0013] In a preferred embodiment of the present invention, the laser scanning rate is 2.5 mm / s.

[0014] In a preferred embodiment of the present invention, in the austenitic stainless steel material for lead-cooled fast reactors, the mass percentage of Cr element is 16% to 20%, the mass percentage of Ni element is 8% to 14%, and the mass percentage of Mn element is ≤2%.

[0015] In a preferred embodiment of the present invention, during irradiation, the spot diameter is 1 mm to 1.5 mm.

[0016] The second object of the present invention is to provide the laser surface modified austenitic stainless steel prepared by the above method.

[0017] The third object of the present invention is to provide the application of the above laser surface modified austenitic stainless steel in a lead or lead-bismuth corrosion environment, and the temperature of the lead or lead-bismuth corrosion environment is 600 °C to 650 °C. Further, the thickness of the oxide film formed by the laser surface modified austenitic stainless steel during the corrosion process is 2.04 to 3.02 μm.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention improves the high-temperature corrosion resistance of austenitic stainless steel to lead / lead-bismuth by laser surface modification. Laser surface treatment is an effective method to change the surface microstructure and composition distribution of materials. Laser surface treatment utilizes the local thermal effect during the interaction between the laser beam and the sample to remelt and solidify the surface structure of the sample, improving the chemical homogeneity of the structure and refining the grains. The present invention uses a laser with an energy of 0.9 mJ to 7.6 mJ and a scanning rate of 2.25 mm / s to 2.75 mm / s to treat austenitic stainless steel used in lead-cooled fast reactors, improving the surface structure uniformity of austenitic stainless steel and refining the grains, accelerating the diffusion of surface oxidation elements, effectively improving the growth quality of the surface oxide film of the material, and promoting the formation of a dense and stable oxide film on the material surface. During the corrosion process, the oxide film formed on the surface of austenitic stainless steel used in lead-cooled fast reactors improves the high-temperature corrosion resistance to lead / lead-bismuth and extends the service life of the material. Brief Description of the Drawings

[0020] Figure 1 It is a schematic diagram of regulating the surface microstructure of 316L stainless steel by laser melting and solidification. a is the surface of the original austenitic stainless steel, b is the uneven-thickness oxide layer formed on the surface of the original austenitic stainless steel after lead-bismuth corrosion, c is the surface of the austenitic stainless steel modified by laser, and d is the uneven-thickness oxide layer formed on the surface of the austenitic stainless steel modified by laser after lead-bismuth corrosion.

[0021] Figure 2 It is a regional schematic diagram of the original 316L steel and the 316L steel after surface modification in Examples 1 to 7. Among them, (a) is the original 316L, (b) is Example 1, (c) is Example 2, (d) is Example 3, (e) is Example 4, (f) is Example 5, (g) is Example 6, and (h) is Example 7.

[0022] Figure 3 It is a cross-sectional SEM diagram of the oxide film in the surface-modified area of different samples after corrosion at 600°C for 100 h. Among them, (a) is the original 316L, (b) is Example 1, (c) is Example 2, (d) is Example 3, (e) is Example 4, (f) is Example 5, (g) is Example 6, and (h) is Example 7.

[0023] Figure 4 It is a surface scan diagram and EDS diagram of the original surface of the original 316L sample after corrosion at 600°C for 100 h. Among them, (a) is the surface scan diagram, (b) is the Fe element distribution diagram, (c) is the Cr element distribution diagram, (d) is the Ni element distribution diagram, (e) is the O element distribution diagram, (f) is the Mn element distribution diagram, (g) is the Bi element distribution diagram of Example 6, and (h) is the Pb element distribution diagram.

[0024] Figure 5 Surface scanning images and EDS maps of the sample of Example 1 after being corroded at 600 °C for 100 h, where (a) is the surface scanning image, (b) is the distribution map of Fe element, (c) is the distribution map of Cr element, (d) is the distribution map of Ni element, (e) is the distribution map of O element, (f) is the distribution map of Mn element, (g) is the distribution map of Bi element in Example 6, and (h) is the distribution map of Pb element.

[0025] Figure 6 Surface scanning images and EDS maps of the sample of Example 2 after being corroded at 600 °C for 100 h, where (a) is the surface scanning image, (b) is the distribution map of Fe element, (c) is the distribution map of Cr element, (d) is the distribution map of Ni element, (e) is the distribution map of O element, (f) is the distribution map of Mn element, (g) is the distribution map of Bi element in Example 6, and (h) is the distribution map of Pb element.

[0026] Figure 7 Surface scanning images and EDS maps of the sample of Example 3 after being corroded at 600 °C for 100 h, where (a) is the surface scanning image, (b) is the distribution map of Fe element, (c) is the distribution map of Cr element, (d) is the distribution map of Ni element, (e) is the distribution map of O element, (f) is the distribution map of Mn element, (g) is the distribution map of Bi element in Example 6, and (h) is the distribution map of Pb element.

[0027] Figure 8 Surface scanning images and EDS maps of the sample of Example 4 after being corroded at 600 °C for 100 h, where (a) is the surface scanning image, (b) is the distribution map of Fe element, (c) is the distribution map of Cr element, (d) is the distribution map of Ni element, (e) is the distribution map of O element, (f) is the distribution map of Mn element, (g) is the distribution map of Bi element in Example 6, and (h) is the distribution map of Pb element.

[0028] Figure 9 Surface scanning images and EDS maps of the sample of Example 5 after being corroded at 600 °C for 100 h, where (a) is the surface scanning image, (b) is the distribution map of Fe element, (c) is the distribution map of Cr element, (d) is the distribution map of Ni element, (e) is the distribution map of O element, (f) is the distribution map of Mn element, (g) is the distribution map of Bi element in Example 6, and (h) is the distribution map of Pb element.

[0029] Figure 10Surface scanning image and EDS map of the sample of Example 6 after corrosion at 600 °C for 100 h, where (a) is the surface scanning image, (b) is the distribution map of Fe element, (c) is the distribution map of Cr element, (d) is the distribution map of Ni element, (e) is the distribution map of O element, (f) is the distribution map of Mn element, (g) is the distribution map of Bi element of Example 6, and (h) is the distribution map of Pb element.

[0030] Figure 11 Surface scanning image and EDS map of the sample of Example 7 after corrosion at 600 °C for 100 h, where (a) is the surface scanning image, (b) is the distribution map of Fe element, (c) is the distribution map of Cr element, (d) is the distribution map of Ni element, (e) is the distribution map of O element, (f) is the distribution map of Mn element, (g) is the distribution map of Bi element of Example 6, and (h) is the distribution map of Pb element. Detailed implementation manners

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] Candidate structural materials for lead-cooled fast reactors must work reliably in environments with high temperature, high irradiation, and strong corrosion. How to improve the material properties to resist the corrosion of liquid lead or lead-bismuth alloy has become one of the key issues in the application of lead-cooled fast reactors. Without any protective measures, nuclear structural materials are prone to failure due to corrosion. Since the expected lifespan of lead-cooled fast reactors is relatively long, to adopt the corrosion-resistant strategy of generating an oxide layer on the material surface to isolate liquid lead-bismuth, it is necessary to ensure the quality of the oxide layer, that is, a reasonable thickness, dense, continuous and uniform, and tightly combined with the substrate without easy detachment. Therefore, the present invention focuses on the direction of material surface modification and attempts to improve the surface properties of austenitic stainless steel through laser melting and solidification. Specifically, during the interaction between the laser beam and the sample, the physical properties, chemical components, stress state, etc. of the sample are changed through local thermal effects, local chemical reactions, etc. to achieve the regulation of the sample's properties. Laser melting and solidification can refine the surface grains of austenitic stainless steel, improve the chemical uniformity of the structure, and enhance the wear resistance and corrosion resistance of the material surface to a large extent. Grain boundaries are effective ways for atomic diffusion. The increase in their density strengthens the diffusion of elements, and the uniform distribution of elements is more conducive to the formation of a continuous oxide film. However, in the prior art, during the laser melting and solidification process, due to the rapid heating and melting of the high-energy density laser beam, a large temperature gradient is generated between the molten layer and the substrate. During rapid cooling, this temperature gradient will cause the inconsistency of volume expansion and contraction between the melted and solidified layer and the substrate, and they will interact with each other to form internal stress in the melted and solidified layer. This stress is usually tensile stress, and excessive laser energy will cause cracking of the cladding layer and deformation of the substrate. In addition, too low laser energy is difficult to achieve the purpose of refining surface grains and adjusting chemical components; too fast scanning rate will lead to incomplete laser melting and solidification, and cannot fully achieve the melting and recrystallization of the material surface; too slow will cause the problem of repeated action on local areas within the laser spot range, resulting in non-uniformity of the laser modification effect on the surface.

[0033] As Figure 1 shown in a of Figure 1 , oxygen on the surface of austenitic stainless steel diffuses inward along grain boundaries, and oxidation elements diffuse outward, resulting in uneven oxide layer thickness due to differences in grain size and element distribution, as Figure 1 shown in b of Figure 1As shown in d. The quality of the oxide film affects the service life of nuclear materials. If the oxide film is too thick, it is prone to cracking and spalling; if it is too thin, the corrosion resistance of the oxide layer is poor; if it is uneven, the weak areas are prone to failure. All of these will affect the protection effect. Grain boundaries are effective ways for element diffusion. By improving the grain size of the material surface to increase the grain boundary density, it is beneficial to promote the formation of the early oxide film.

[0034] In the austenitic stainless steel material for lead-cooled fast reactors, the content range of Cr element is 16 - 20 wt.%, the content range of Ni element is 8 - 14 wt.%, and the content range of Mn element is ≤2 wt.%.

[0035] Example 1

[0036] The austenitic stainless steel model used in this example is 316L steel.

[0037] Place the 10mm×10mm 316L steel at the laser focus position, and use a laser with an energy of 0.9 mJ and a spot diameter of 1 mm to perform surface treatment on the 316L steel at a scanning speed of 2.5 mm / s to obtain surface-modified austenitic stainless steel.

[0038] Example 2

[0039] The austenitic stainless steel model used in this example is 316L steel.

[0040] Place the 10mm×10mm 316L steel at the laser focus position, and use a laser with an energy of 7.6 mJ and a spot diameter of 1 mm to perform surface treatment on the 316L steel at a scanning speed of 2.5 mm / s to obtain surface-modified austenitic stainless steel.

[0041] Example 3

[0042] The austenitic stainless steel model used in this example is 316L steel.

[0043] Place the 10mm×10mm 316L steel at the laser focus position, and use a laser with an energy of 25 mJ and a spot diameter of 1 mm to perform surface treatment on the 316L steel at a scanning speed of 2.5 mm / s to obtain surface-modified austenitic stainless steel.

[0044] Example 4

[0045] The austenitic stainless steel model used in this example is 316L steel.

[0046] Place the 10mm×10mm 316L steel at the laser focus position, and use a laser with an energy of 56 mJ and a spot diameter of 1 mm to perform surface treatment on the 316L steel at a scanning speed of 2.5 mm / s to obtain surface-modified austenitic stainless steel.

[0047] Example 5

[0048] The austenitic stainless steel used in this example is type 316L steel.

[0049] Place a 10mm×10mm piece of 316L steel at the laser focus position, and use a laser with 7.6mJ and a spot diameter of 1mm to perform surface treatment on the 316L steel at a scanning speed of 0.15mm / s to obtain surface-modified austenitic stainless steel.

[0050] Example 6

[0051] The austenitic stainless steel used in this example is type 316L steel.

[0052] Place a 10mm×10mm piece of 316L steel at the laser focus position, and use a laser with 7.6mJ and a spot diameter of 1mm to perform surface treatment on the 316L steel at a scanning speed of 1.5mm / s to obtain surface-modified austenitic stainless steel.

[0053] Example 7

[0054] The austenitic stainless steel used in this example is type 316L steel.

[0055] Place a 10mm×10mm piece of 316L steel at the laser focus position, and use a laser with 7.6mJ and a spot diameter of 1mm to perform surface treatment on the 316L steel at a scanning speed of 3.6mm / s to obtain surface-modified austenitic stainless steel.

[0056] Example 8

[0057] The austenitic stainless steel used in this example is type 304 stainless steel.

[0058] Place a 10mm×10mm piece of 304 steel at the laser focus position, and use a laser with 7.6mJ and a spot diameter of 1mm to perform surface treatment on the 304 stainless steel at a scanning speed of 2.5mm / s to obtain surface-modified austenitic stainless steel.

[0059] The grain refinement on the surface of the steel and the improvement of the chemical homogeneity of the structure are achieved, optimizing the element diffusion process. After corrosion in a liquid lead-bismuth environment at 600°C for 100h, a uniform and continuous dense oxide film is formed after laser surface modification, thus completing the improvement of the corrosion resistance of the steel material.

[0060] Example 9

[0061] The austenitic stainless steel used in this example is type 347 stainless steel.

[0062] Place 347 steel with a size of 10 mm × 10 mm at the laser focus position. Use a laser with an energy of 7.6 mJ and a spot diameter of 1 mm to perform surface treatment on the surface of 347 stainless steel at a scanning speed of 2.5 mm / s, obtaining surface-modified austenitic stainless steel.

[0063] This makes the grain refinement and tissue chemical uniformity of the steel surface improved, and optimizes the element diffusion process. After corrosion in a liquid lead-bismuth environment at 600 °C for 100 h, a uniform and continuous dense oxide film is formed after laser surface modification, thus completing the improvement of the corrosion resistance of the steel material.

[0064] Figure 2 Figures of the physical objects of Examples 1 to 7 and 316L steel without laser melting are shown. Examples 1 to 7 and 316L steel without laser melting are subjected to lead-bismuth corrosion treatment. Specifically, the oxygen concentration is controlled to be 10 -6 ~10 - 5 wt.%. Immerse the samples in liquid lead-bismuth at 600 °C for corrosion for 100 h. Among them, in the liquid lead-bismuth, the mass percentage of Pb is 44.47 wt%, and the mass percentage of Bi is 55.53 wt%.

[0065] The morphology of the oxide film after lead-bismuth corrosion treatment is as Figures 4 - 11 shown.

[0066] The morphology of the surface oxide film of the original 316L steel after lead-bismuth corrosion treatment is as Figure 3 shown in (a) of Figure 4 and the EDS element distribution map is as Figure 4 shown. In the comparative example, the inner oxide protrudes, the thickness of the oxide film is 1.16 - 3.38 μm, and the thin oxide film area is prone to failure, resulting in the infiltration of liquid lead-bismuth. The quality of the oxide film formed on the surface without laser modification is poor.

[0067] Figure 3 (b) - (e) in Figure 3 are the morphology diagrams of the oxide films after lead-bismuth corrosion treatment of the laser-modified austenitic stainless steel obtained by surface modification under the same scanning rate and different laser energies in Examples 1 to 4 respectively. The thicknesses of the formed oxide films are (b) 1.77 - 3.05 μm, (c) 2.04 - 3.02 μm, (d) 1.46 - 3.35 μm, and (e) 2.71 - 4.02 μm respectively. Figure 3Among them, (c) and (f)-(h) are the morphology diagrams of the oxide films on the laser-modified austenitic stainless steel after lead-bismuth corrosion treatment under the same laser energy but different scanning rates in Example 2 and Examples 5-7. The thicknesses of the generated oxide films are (c) 2.04-3.02 μm, (f) 1.04-3.96 μm, (g) 0.76-4.33 μm, and (h) 1.13-3.20 μm, respectively. The data of the laser parameters and the corresponding oxide film thicknesses are sorted out in Table 1 as follows.

[0068] The thickness range of the surface oxide film obtained in Example 4 is 2.71-4.02 μm. Compared with the original surface with a thickness range of 1.16-3.38 μm, the overall thickness of the oxide film has increased by 0.64-1.55 μm.

[0069] The scanning rate in Example 5 is 0.15 mm / s. The too-low scanning rate results in an increase in the modified overlapping area. Finally, the thickness range of the obtained surface oxide film is 1.04-3.96 μm. Compared with the original surface with a thickness range of 1.16-3.38 μm, while the thickness of the oxide film increases, the uniformity decreases.

[0070] The growth stress of the oxide film is likely to induce the generation of cracks. The excellent denseness of Fe-Cr spinel is sufficient to protect the substrate from LBE corrosion. However, the thickening is more likely to cause the shedding of the oxide film, and the non-uniformity of the oxide film thickness will increase the failure probability of the weak areas. Therefore, the effects of the laser modification treatments adopted in Example 4 and Example 5 are worse than that in Example 2. Although the thickness range of the surface oxide film obtained in Example 3 is 1.46-3.35 μm, compared with the results of the original surface, the strengthening effect is not obvious. Therefore, the effect of the modification treatment with the laser modification parameters in Example 3 is poor. Similarly, the effects of the modification treatments with the laser modification parameters set in Example 6 and Example 7 are poor.

[0071] Example 1 adopted the laser modification parameters of energy 0.9 mJ and scanning speed 2.5 mm / s. The thickness range of the obtained surface oxide film is 1.77-3.05 μm. Compared with the original surface with a thickness range of 1.16-3.38 μm, the oxide film has improvements in both thickness and uniformity.

[0072] Example 2 adopted the laser modification parameters of energy 7.6 mJ and scanning speed 2.5 mm / s. The thickness range of the obtained surface oxide film is 2.04-3.02 μm. Compared with the original surface with a thickness range of 1.16-3.38 μm, the oxide film has improvements in both thickness and uniformity. Combining Figure 6 with the EDS results, it can be further found that after the treatment according to the method of Example 2, the chemical uniformity of the surface structure of 316L steel has also been significantly improved.

[0073] Combining the results of these embodiments, it can be determined that the reasonable range of the laser modification energy setting is 0.9 - 7.6 mJ. Considering the diversity and errors of the condition settings, further, the reasonable range of the scanning rate is 2.25 - 2.75 mm / s.

[0074] Table 1 Laser parameters and oxide film thickness of different embodiments

[0075] Original / Modified Areas of the Sample Laser Energy (mJ) Laser Speed (mm / s) Thickness of Oxide Film (μm) a (Original) -- -- 1.16～3.38 b (Example 1) 0.9 2.5 1.77～3.05 c (Example 2) 7.6 2.5 2.04～3.02 d (Example 3) 25 2.5 1.46～3.35 e (Example 4) 56 2.5 2.71～4.02 f (Example 5) 7.6 0.15 1.04～3.96 g (Example 6) 7.6 1.5 0.76～4.33 h (Example 7) 7.6 3.6 1.13～3.20

[0076] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0077] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A method for improving the high-temperature corrosion resistance of austenitic stainless steel to lead / lead-bismuth, characterized in that It includes the following steps: Irradiate the surface of austenitic stainless steel for lead-cooled fast reactors with a laser having an energy of 0.9 mJ to 56 mJ and a scanning rate of 0.15 mm / s to 3.60 mm / s. After the surface of the austenitic stainless steel melts and then cools, the surface microstructure of the austenitic stainless steel is improved, the tissue chemical uniformity is enhanced, and the grains are refined to obtain laser surface modified austenitic stainless steel. The laser surface modified austenitic stainless steel forms an oxide film during the corrosion process, improving the corrosion resistance of the austenitic stainless steel in a lead or lead-bismuth environment at 600 °C to 650 °C.

2. A method for improving the high-temperature corrosion resistance of austenitic stainless steel to lead / lead bismuth, according to claim 1, characterized in that The laser energy range is 0.9 mJ to 7.6 mJ.

3. A method for improving the high-temperature resistance of austenitic stainless steel to lead / lead-bismuth corrosion according to claim 2, characterized in that, The laser energy is 7.6 mJ.

4. A method for improving the high-temperature lead / lead-bismuth corrosion resistance of austenitic stainless steel according to claim 1, characterized in that, The laser scanning rate is 2.25 mm / s to 2.75 mm / s.

5. A method for improving the high-temperature lead / lead-bismuth corrosion resistance of austenitic stainless steel according to claim 4, characterized in that The laser scanning rate is 2.5 mm / s.

6. A method for improving the high-temperature corrosion resistance of austenitic stainless steel to lead / lead-bismuth, according to claim 1, characterized in that, In the austenitic stainless steel material for lead-cooled fast reactors, the mass percentage of Cr element is 16% to 20%, the mass percentage of Ni element is 8% to 14%, and the mass percentage of Mn element is ≤2%.

7. A method for improving the high-temperature corrosion resistance of austenitic stainless steel to lead / lead-bismuth, according to claim 1, characterized in that During irradiation, the spot diameter is 1 mm to 1.5 mm.

8. A laser surface modified austenitic stainless steel prepared by the method according to any one of claims 1-7.

9. Use of the austenitic stainless steel with laser surface modification according to claim 8 in a lead or lead-bismuth corrosion environment, characterized in that The temperature of the lead or lead-bismuth corrosion environment is 600 °C to 650 °C.

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