Method for strengthening radiation resistance of austenitic stainless steel

Abstract

The invention relates to a method for strengthening the radiation resistance of austenitic stainless steel, and relates to the technical field of nuclear power key structural materials. According to the main technical scheme, the method for strengthening the radiation resistance of the austenitic stainless steel comprises the following steps: carrying out plastic deformation treatment on an austenitic stainless steel part so as to form a specific microstructure in the austenitic stainless steel part; wherein the specific microstructure can promote an austenite phase to be converted into a continuous martensite phase under the irradiation condition; and the austenitic stainless steel part subjected to plastic deformation treatment is subjected to surface removing treatment, so that the surface structure of the austenitic stainless steel part is the specific microstructure, and the austenitic stainless steel with the anti-radiation performance strengthened is obtained. The method is mainly used for enabling the austenitic stainless steel to generate large-range self-adaptive martensite phase transformation under irradiation, so that irradiation defects can be effectively absorbed, and the mechanical property of the austenitic stainless steel is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear power key structure materials, and particularly relates to a method for strengthening the anti-radiation performance of austenitic stainless steel. BACKGROUND

[0002] Austenitic stainless steel is often selected as a nuclear power key structure material due to its excellent mechanical properties, processing properties and corrosion resistance. However, during service, the austenitic stainless steel will be irradiated, resulting in radiation damage and affecting the mechanical properties.

[0003] After the austenitic stainless steel is damaged by radiation, a large number of point defects and defect clusters will be generated, and phase transition will be induced. One is the interaction of defects, solute atoms and defect traps to cause solute segregation, and when the solid solubility is exceeded, a new phase is precipitated (diffusion type phase transition); the other is the stress and strain localization caused by defect aggregation, and when the stress and strain exceed the critical value, a new phase is induced (cutting edge type phase transition). These phase transitions can greatly consume the surrounding radiation defects, but are often isolated and distributed, and the macroscopic performance is that the mechanical properties of the material are significantly deteriorated.

[0004] Among them, the evaluation indexes of the anti-radiation performance of the material mainly include radiation defect density, size, mechanical properties (radiation hardening, embrittlement, creep, etc.). At present, in the field of nuclear power technology, there are mainly the following three methods to improve the anti-radiation performance of austenitic stainless steel:

[0005] 1) Grain refinement: by grain refinement, the interface volume percentage is increased, and the absorption capacity of the material to radiation defects is improved. However, at a low radiation dose, the interaction between the interface and the defects may cause interface instability or element segregation, thereby affecting the service performance of the material.

[0006] 2) Precipitation strengthening: by generating fine and dispersed precipitates in the material, radiation defects can be effectively absorbed / pinned. However, it is difficult to control the uniformity of the distribution of the precipitates in actual production, and the production batch stability is low.

[0007] 3) Element regulation: by adding trace elements according to the application environment, the material performance is improved. However, safety is the first requirement in the field of nuclear power, and the development of new materials must go through rigorous tests, which has the problems of long time consumption and high cost, and cannot realize rapid application.

[0008] In summary, there is an urgent need to develop a new method for strengthening the anti-radiation performance of austenitic stainless steel, so that the austenitic stainless steel after anti-radiation strengthening can effectively absorb radiation defects and maintain excellent mechanical properties. SUMMARY

[0009] Therefore, the application provides a method for strengthening the radiation resistance of an austenitic stainless steel, which mainly aims at enabling the austenitic stainless steel after the strengthening of the radiation resistance to have a wide-range self-adaptive martensite phase change under ion irradiation, so as to effectively absorb irradiation defects and ensure the mechanical properties of the austenitic stainless steel.

[0010] To achieve the above-mentioned purpose, the application mainly provides the following technical scheme:

[0011] In one aspect, the application provides a method for strengthening the radiation resistance of an austenitic stainless steel, which comprises the following steps:

[0012] The plastic deformation treatment step: performing plastic deformation treatment on the austenitic stainless steel part to form a specific microstructure in the austenitic stainless steel part; wherein the specific microstructure can promote the austenite phase to transform into a continuous martensite phase under irradiation conditions;

[0013] The skin removal treatment step: performing skin removal treatment on the austenitic stainless steel part after the plastic deformation treatment, so that the surface layer of the austenitic stainless steel part is the specific microstructure, thereby obtaining the austenitic stainless steel after the strengthening of the radiation resistance.

[0014] Preferably, the specific microstructure comprises a first specific microstructure; wherein in the first specific microstructure: the stacking fault density in the austenite grain is greater than >10 14 m -2 ; the grain boundary comprises Σ3(111) grain boundary and small-angle grain boundary, wherein the size of the austenite grain is nanoscale; preferably, the size of the austenite grain is 30-100 nm.

[0015] Preferably, the specific microstructure comprises a second specific microstructure; wherein the second specific microstructure comprises: austenite grains and ε-martensite, wherein the ε-martensite is a hexagonal close-packed phase; wherein the size of the austenite grain is nanoscale; preferably, the size of the austenite grain is 70-100 nm; preferably, in the second specific microstructure: the volume fraction of the ε-martensite is >60%.

[0016] Preferably, before the plastic deformation treatment step, the method further comprises:

[0017] The milling treatment: performing milling treatment on the surface of the austenitic stainless steel part;

[0018] Preferably, the surface roughness Ra of the austenitic stainless steel part after the milling treatment is less than 0.3 μm.

[0019] Preferably, in the plastic deformation treatment step, the plastic deformation of the austenitic stainless steel piece is realized by surface mechanical rolling treatment.

[0020] Preferably, in the surface mechanical rolling treatment, the rolling tool contacts the material and then presses it to deform the material; preferably, the displacement of the rolling tool is 10-60 μm.

[0021] Preferably, in the surface mechanical rolling treatment, the surface shear strain of the austenitic stainless steel piece is <100, and the strain rate is <10 4 / s;

[0022] Preferably, the skin removal treatment is polishing treatment; preferably, the polishing treatment is electrolytic polishing treatment; further preferably, in the electrolytic polishing treatment, the electrolyte is 10±2% perchloric acid alcohol solution; further preferably, the parameters of the electrolytic polishing treatment are as follows: the temperature of the electrolytic polishing treatment is -20-25 °C, and the voltage of the electrolytic polishing treatment is 20-25 V.

[0023] Preferably, the austenitic stainless steel piece is a nuclear austenitic stainless steel piece, a 304 austenitic stainless steel piece, or a 301 austenitic stainless steel piece.

[0024] Preferably, the austenitic stainless steel piece is a nuclear 304NG austenitic stainless steel piece; wherein,

[0025] When, in the surface mechanical rolling treatment, the surface shear strain of the austenitic stainless steel piece is controlled to be 10-15, and the strain rate is controlled to be 10 2 -10 3 / s, the specific microstructure includes a first specific microstructure; preferably, in the skin removal treatment step, the time of the electrolytic polishing treatment is controlled to be 0.5-1.5 min, so that the surface layer of the austenitic stainless steel piece has the first specific microstructure.

[0026] When, in the surface mechanical rolling treatment, the surface shear strain of the austenitic stainless steel piece is controlled to be 5-10, and the strain rate is controlled to be 10 1 -10 2 / s, the specific microstructure includes a second specific microstructure; preferably, in the skin removal treatment step, the time of the electrolytic polishing treatment is controlled to be 0.5-1.5 min, so that the surface layer of the austenitic stainless steel piece has the second specific microstructure.

[0027] Preferably, the austenitic stainless steel part is a 304 austenitic stainless steel part; wherein, in the surface mechanical rolling treatment, the surface shear strain of the austenitic stainless steel part is controlled to be 5-10, and the strain rate is 10. 1 ~10 2 At / s, the specific microstructure organization includes a second specific microstructure organization.

[0028] On the other hand, embodiments of the present invention provide an austenitic stainless steel part with enhanced radiation resistance, wherein the austenitic stainless steel part with enhanced radiation resistance includes a specific microstructure; wherein the specific microstructure can promote the transformation of the austenitic phase into a continuous martensite phase under irradiation conditions;

[0029] Preferably, the surface microstructure of the radiation-resistant enhanced austenitic stainless steel part is the specific microstructure microstructure; more preferably, the internal microstructure of the radiation-resistant enhanced austenitic stainless steel part, excluding the surface microstructure, includes the specific microstructure microstructure.

[0030] Preferably, the specific microstructure includes a first specific microstructure; wherein, in the first specific microstructure, the stacking fault density within the austenite grains is greater than >10. 14 m -2 The grain boundaries include Σ3(111) grain boundaries and small-angle grain boundaries, wherein the size of the austenite grains is in the nanometer range; preferably, the size of the austenite grains is 30-100 nm.

[0031] Preferably, the specific microstructure includes a second specific microstructure; the second specific microstructure includes: austenite grains and ε-martensite, wherein the ε-martensite is a close-packed hexagonal phase; wherein the size of the austenite grains is in the nanometer range; preferably, the size of the austenite grains is 70-100 nm; preferably, in the second specific microstructure, the volume fraction of ε-martensite is >60%.

[0032] Preferably, the radiation-resistant enhanced austenitic stainless steel part is obtained by strengthening the austenitic stainless steel using any of the above-described methods for enhancing its radiation resistance.

[0033] Compared with the prior art, the method for enhancing the radiation resistance of austenitic stainless steel according to the present invention has at least the following beneficial effects:

[0034] The embodiment of the present application provides a method for strengthening the radiation resistance of an austenitic stainless steel. The method comprises plastic deformation treatment of the austenitic stainless steel to form a specific microstructure in the austenitic stainless steel part. The specific microstructure can promote the transformation of austenite phase into continuous martensite phase under radiation conditions. The continuous martensite phase is a beneficial phase, so that the radiation resistance of the austenitic stainless steel is improved in terms of effective absorption of radiation defects and mechanical properties.

[0035] Further, in order to form the specific microstructure in the austenitic steel, the plastic deformation treatment is as follows: surface mechanical rolling treatment is performed on the austenitic stainless steel part, and a WC-Co hard alloy ball is used as the rolling tool. In the surface mechanical rolling treatment, the shear strain rate of the surface of the austenitic stainless steel part is less than 10 4 / s. Further, after the plastic deformation treatment, the austenitic stainless steel is subjected to skin removal treatment, so that the surface layer of the austenitic stainless steel is the specific microstructure.

[0036] The above description is only a summary of the technical scheme of the present application. In order to more clearly understand the technical means of the present application and to implement the content of the description, the preferred embodiments of the present application are described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The relationship between the volume fraction of alpha-martensite in the austenitic stainless steel 304NG plate sample (GNS) after the radiation resistance strengthening in Example 1 and the austenitic stainless steel 304NG plate sample (CG) without radiation resistance strengthening and the irradiation dose;

[0038] Figure 2 The relationship between the irradiation dislocation loop density and size in the austenitic stainless steel 304NG plate sample (GNS) after the radiation resistance strengthening in Example 1 and the austenitic stainless steel 304NG plate sample (CG) without radiation resistance strengthening and the irradiation dose;

[0039] Figure 3 The hardening rate trend along the depth direction before and after irradiation (50dpa) of the austenitic stainless steel 304NG plate sample (GNS) after the radiation resistance strengthening in Example 1 and the austenitic stainless steel 304NG plate sample (CG) without radiation resistance strengthening;

[0040] Figure 4Figure 1 is a first specific microstructure morphology chart of the irradiation resistance performance strengthened austenitic stainless steel 304NG plate sample of Example 1; wherein, (a) is a bright field image (BF-TEM) of the sample surface layer after surface mechanical rolling treatment; (b) is a selected area electron diffraction pattern of the selected position in (a); (c) is a phase distribution chart obtained by transmission Kikuchi diffraction (TKD) analysis (red represents austenite phase (γ), green represents α'-martensite phase);

[0041] Figure 5 Figure 2 is a further microstructure characterization chart of the surface layer structure of the irradiation resistance performance strengthened austenitic stainless steel 304NG plate sample of Example 1; wherein, (a) is a scanning transmission electron microscopy (STEM) image; (b) is a high-resolution scanning transmission electron microscopy (HRSTEM) image; (c) is a Fourier transform chart.

[0042] Figure 6 Figure 3 is a microstructure chart (room temperature) of the irradiation resistance performance strengthened austenitic stainless steel 304NG plate sample of Example 1 at different irradiation doses; wherein, Figure 6 (a), (b), (c), (d), (e), (f) in Figure 3 are STEM images of irradiation regions after treatment at different irradiation doses, (a1), (b1), (c1), (d1), (e1), (f1) are electron diffraction patterns of the corresponding regions after treatment at different irradiation doses.

[0043] Figure 7 Figure 4 is a distribution chart of the volume percentage of α'-martensite and irradiation damage dose of the irradiation resistance performance strengthened austenitic stainless steel 304NG plate sample after iron ion irradiation at 300°C.

[0044] Figure 8 Figure 5 is a microstructure chart of the control sample and the sample of the example after ion irradiation (300°C); wherein, (a) is a BF-TEM image of the control sample (i.e. the austenitic stainless steel 304NG plate sample without irradiation resistance performance strengthening treatment) after ion irradiation (300°C), (b) is a BF-TEM image of the irradiation resistance performance strengthened austenitic stainless steel 304NG plate sample of the present application after ion irradiation (300°C); (c) is a selected area electron diffraction image of the region of (b).

[0045] Figure 9 Figure 6 is a characterization chart of the surface layer structure of the irradiation resistance performance strengthened austenitic stainless steel 304NG plate of Example 4; wherein, (a) is a BF-TEM image, (b) is a selected area electron diffraction pattern of the boxed region in (a).

[0046] Figure 10He irradiation experiment of the austenitic stainless steel 304NG plate sample whose anti-radiation performance is strengthened according to the embodiment 1 to 3 + XRD pattern after ion irradiation experiment (0.5 MeV / U, 10000 appm).

[0047] Figure 11 Anti-radiation principle diagram of the austenitic stainless steel in the prior art and the austenitic stainless steel whose anti-radiation performance is strengthened according to the embodiment of the present application. DETAILED DESCRIPTION

[0048] In order to further clarify the technical means and effects taken by the present application to achieve the predetermined object of the application, the specific embodiments, structures, features and effects according to the present application are described in detail below in combination with the drawings and preferred embodiments. In the following description, different "an embodiment" or "embodiments" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0049] The present application provides a method for strengthening the anti-radiation performance of an austenitic stainless steel, which can realize large-area and continuous martensite phase transformation of the austenitic stainless steel under irradiation, effectively absorb irradiation defects, ensure mechanical properties, and comprehensively improve the anti-radiation performance of the austenitic stainless steel.

[0050] Mechanism of austenite to α'-martensite transformation: The nuclear austenitic stainless steel represented by 304NG has a relatively unstable austenite due to low Ni content, which is easy to transform into α'-martensite phase under external force. There are two typical phase transformation processes:

[0051] 1) Austenite→α'-martensite;

[0052] 2) Austenite→ε-martensite→α'-martensite.

[0053] Both of the two phase transformation processes are shear type phase transformation, that is, the atomic lattice is displaced through shear mechanism, without involving atomic diffusion.

[0054] Under irradiation conditions, irradiation defects have the characteristics of spontaneous enrichment in high-density defect regions. For general austenitic stainless steel, when the defects in a certain region are enriched to a certain extent, the stress in this region increases significantly, thereby inducing martensite phase transformation. However, the martensite phase transformation consumes the defects in this region, and the region eventually forms a low irradiation defect region, which is not conducive to further phase transformation, and thus forms isolated α'-martensite. Since the hardness of α'-martensite is higher than that of the austenitic matrix, this region is prone to stress concentration during service, which significantly deteriorates the mechanical properties.

[0055] The stacking fault, ε-martensite is a kind of organizational structure of atomic lattice displacement, and preforming these microstructures in austenite helps austenite transform into α'-martensite under a lower stress state, thereby reducing irradiation defects through phase transformation. In addition, irradiation defects can interact with stacking faults and ε-martensite to form α'-martensite, and preforming these special microstructures also enables the formed martensite phase to continuously extend, thereby providing a basis for forming a continuous martensite phase. A large-area continuous martensite phase can effectively avoid stress concentration, so that the material is both strong and tough (TRIP effect).

[0056] The present application constructs a specific microstructure in austenitic stainless steel through severe plastic deformation technology, so that the austenitic stainless steel can undergo a large-area self-adaptive martensite phase transformation under ion irradiation (the austenitic stainless steel without the specific microstructure cannot undergo the transformation). This phenomenon can be clearly reflected by XRD analysis. This feature can effectively absorb irradiation defects and reduce the density and size of irradiation dislocation loops in the material. At the same time, the irradiation hardening rate is low, which greatly improves the irradiation resistance of the austenitic stainless steel.

[0057] In the present application, the specific solutions are as follows:

[0058] The embodiment of the present application provides a method for strengthening the irradiation resistance of an austenitic stainless steel, which comprises the following steps:

[0059] Milling treatment: the surface of the austenitic stainless steel part is subjected to milling treatment; preferably, the surface roughness of the austenitic stainless steel part after the milling treatment is less than 0.3 μm.

[0060] Plastic deformation treatment step: the austenitic stainless steel part is subjected to plastic deformation treatment to form a specific microstructure in the austenitic stainless steel part; wherein the specific microstructure can promote the transformation of austenite into a continuous martensite under irradiation conditions.

[0061] It should be noted that: the specific microstructure includes a first specific microstructure and / or a second specific microstructure. Both of the two specific microstructures can enable the austenitic stainless steel to undergo a large-area, continuous self-adaptive martensite phase transformation under irradiation.

[0062] In the first specific microstructure: the stacking fault density in the austenite grain is greater than > 10 14 m -2 ; the grain boundary includes Σ3(111) grain boundary and low-angle grain boundary, wherein the size of the austenite grain is nanoscale; preferably, the size of the austenite grain is 30-100 nm.

[0063] The second specific microstructure organization includes: austenite grains, and epsilon-martensite, wherein the epsilon-martensite is a hexagonal close-packed phase; the size of the austenite grains is nanoscale; preferably, the size of the austenite grains is 70-100 nm; preferably, in the second specific microstructure organization, the volume fraction of the epsilon-martensite is >60%.

[0064] Preferably, the plastic deformation of the austenitic stainless steel part is realized by surface mechanical rolling treatment of the austenitic stainless steel part. Preferably, in the surface mechanical rolling treatment, a rolling tool of WC-Co cemented carbide ball is used; preferably, the diameter of the WC-Co cemented carbide ball is 6-8 mm. Preferably, in the surface mechanical rolling treatment, the surface shear strain of the austenitic stainless steel part is <100, and the strain rate is <10 4 / s. The rolling tool contacts the material and then is pressed downward to deform the material. Preferably, the downward displacement of the rolling tool is 10-60 μm.

[0065] It should be noted that the term "shear strain" in the present application refers to the relative deformation of an object when sheared. The term "strain rate" refers to the change in strain per unit time.

[0066] The calculation method of the shear strain and the strain rate is as follows:

[0067] The displacement-depth field formula is used to calculate the strain and the strain rate of the material. When the sample surface is sheared and deformed, the displacement field y and the depth x conform to the following function relationship:

[0068] y(x)=ysexp(-kx)

[0069] wherein y s is the displacement of the sample surface layer (x=0), and k is a constant.

[0070] The relationship between the shear strain γ(x) and the displacement can be expressed as:

[0071]

[0072] The strain rate The expression along the depth can be expressed as:

[0073]

[0074] wherein t is the processing time, and V is the moving speed of the rolling ball head.

[0075] The skin removal treatment step: the austenitic stainless steel part after the plastic deformation treatment is subjected to skin removal treatment to obtain the austenitic stainless steel after the performance of the anti-radiation performance is strengthened.

[0076] It should be noted that the surface skin is removed by the surface skin removing treatment, mainly to remove the equiaxed crystal structure (as the surface deformation is the largest), so that the surface layer of the austenitic stainless steel after the irradiation resistance is strengthened is the specific microstructure.

[0077] Preferably, the surface skin removing treatment is polishing treatment; preferably, the polishing treatment is electrolytic polishing treatment; further preferably, in the electrolytic polishing treatment, the electrolyte is 10% perchloric acid alcohol solution. The temperature of the electrolytic polishing treatment is -20-25℃, and the voltage of the electrolytic polishing treatment is 20-25V.

[0078] Preferably, the austenitic stainless steel part is 304NG austenitic stainless steel part for nuclear use; wherein, when the surface shear strain of the austenitic stainless steel part is controlled to be 10-15 and the strain rate is controlled to be 10 2 ~10 3 / s in the surface mechanical rolling treatment, the specific microstructure includes a first specific microstructure; preferably, in the surface skin removing treatment step, the time of the electrolytic polishing treatment is controlled to be 0.5-1.5min, so that the surface layer of the austenitic stainless steel part is the first specific microstructure. When the surface shear strain of the austenitic stainless steel part is controlled to be 5-10 and the strain rate is controlled to be 10 1 ~10 2 / s in the surface mechanical rolling treatment, the specific microstructure includes a second specific microstructure; preferably, in the surface skin removing treatment step, the time of the electrolytic polishing treatment is controlled to be 0.5-1.5min, so that the surface layer of the austenitic stainless steel part is the second specific microstructure.

[0079] Preferably, the austenitic stainless steel part is 304 austenitic stainless steel part; wherein, when the surface shear strain of the austenitic stainless steel part is controlled to be 5-10 and the strain rate is controlled to be 10 1 ~10 2 / s in the surface mechanical rolling treatment, the specific microstructure includes a second specific microstructure.

[0080] It should be noted that: Figure 11As shown in the prior art, the martensite phase generated by the austenitic stainless steel under irradiation is isolated, which is a harmful phase and needs to be avoided as much as possible. However, due to the element composition of the austenitic stainless steel, the formation of martensite is inevitable. The present application constructs a specific microstructure (the first specific microstructure, the second specific microstructure) in the austenitic stainless steel by a severe plastic deformation technology, so that the austenitic stainless steel can occur a large-area self-adaptive martensite phase transition under irradiation (the austenitic stainless steel without the above specific microstructure will not occur). The specific microstructure effectively absorbs irradiation defects, reduces the density and size of irradiation dislocation loops in the material. At the same time, the irradiation hardening rate is low, which greatly improves the anti-irradiation performance of the austenitic stainless steel.

[0081] The scheme of the present application converts the harmful phase into a beneficial phase, and the anti-irradiation performance is comprehensively improved. The martensite grain size formed by the self-adaptive martensite phase transition is still stable at the nanoscale at high irradiation dose, and has a fine-grain strengthening mechanism. Moreover, based on the existing material, the time required for nuclear safety evaluation is greatly reduced, and the severe plastic deformation technology is suitable for wide application in industry, and the industrial adaptability of the method is high. The processing equipment of the present application is simple, the cost is low, and the application range is wide.

[0082] The present application is further illustrated by specific examples and comparative examples as follows:

[0083] Example 1

[0084] The present embodiment provides a method for strengthening the anti-irradiation performance of an austenitic stainless steel to improve the anti-irradiation performance of a nuclear austenitic stainless steel 304NG plate. The main steps are as follows:

[0085] Plastic deformation treatment: the nuclear austenitic stainless steel 304NG plate is subjected to plastic deformation treatment by surface mechanical rolling technology. The specific process parameters are as follows:

[0086] The tool bit of mechanical rolling is a WC / Co hard alloy ball (the diameter of the WC-Co hard alloy ball is 8 mm). The transverse direction of the austenitic stainless steel 304NG plate is defined as the x-axis, and the longitudinal direction is defined as the y-axis. A total of L x ×L y area needs to be processed. In the specific surface mechanical rolling process: after the alloy ball contacts the sample, it continues to press down by 30 μm, then processes (rolls) a displacement (L y ) along the y direction of the plate, then feeds once along the x direction with a step size (P x ) of 0.03 mm, then processes (rolls) a displacement (L y ) along the -y direction, and then feeds along the x direction with a step size (P xThe sample is processed in one feed cycle, repeating this process until the required processing area is completed; the feed rate (v) is 33 mm / s. This process can be considered one processing pass; in this embodiment, two processing passes are performed. It should be noted that "step length" refers to the distance the tool moves in a single pass along the feed direction under CNC program control during CNC machining. In the above surface mechanical rolling treatment, the surface shear strain of the austenitic stainless steel part is set to 10–15, and the strain rate is 10... 2 ~10 3 / s.

[0087] Surface removal: The plastically deformed sheet is cut into approximately 10×10×2mm pieces using wire electrical discharge machining. 3 The block-shaped sample was subjected to surface electropolishing treatment using a 10% perchloric acid alcohol solution as the electropolishing liquid (the temperature, voltage and time of the surface electropolishing treatment were -20℃, 20V, 0.5-1.5min, respectively), resulting in austenitic stainless steel 304NG plate with enhanced radiation resistance.

[0088] Figure 4 The images show the morphology of the first specific microstructure of the radiation-strengthened austenitic stainless steel 304NG sheet from Example 1; (a) is a BF-TEM image of the sample surface after mechanical rolling treatment; (b) is a selected area electron diffraction pattern at the framed location in (a) (reflecting the presence of austenite and α'-martensite in this region); (c) is a phase distribution diagram obtained by transmission Kikuchi diffraction (TKD) analysis (red represents the austenitic phase (γ), green represents the α'-martensite phase), from... Figure 4 It can be seen that the corresponding region contains approximately 10% α'-martensite, randomly distributed within the austenitic matrix.

[0089] Figure 5 The images show further microstructural characterization of the surface microstructure of the radiation-strengthened austenitic stainless steel 304NG sheet from Example 1; (a) is a STEM image, showing high-density stacking faults within the austenitic grains; (b) is an HRSTEM image; and (c) is a Fourier transform image. Figure 4 , Figure 5 This indicates the presence of twins and high-density stacking faults in the region.

[0090] from Figure 4 and Figure 5 It can be seen that in the surface structure of the radiation-resistant enhanced austenitic stainless steel 304NG plate obtained in this embodiment, the stacking fault density within the austenitic grains is greater than >10. 14 m -2The grain boundary includes a Sigma 3 (111) grain boundary and a small-angle grain boundary, and is randomly distributed in the austenite; wherein the size of the austenite grain is nanoscale.

[0091] At room temperature, the Fe 10+ Ion irradiation (0.62 MeV / U, 0.5-155 dpa) test. Figure 6 The microstructure of the irradiated austenitic stainless steel 304NG plate of Example 1 is shown in the figure, wherein the irradiation dose of the sample is different. Figure 6 (a), (b), (c), (d), (e), (f) in (a1), (b1), (c1), (d1), (e1), (f1) are the STEM images of the irradiation region after treatment at different irradiation doses, and the electron diffraction patterns of the corresponding regions are shown in (a1), (b1), (c1), (d1), (e1), (f1), respectively. Figure 6 It can be seen that the content of alpha-prime martensite on the surface of the irradiated sample increases with the increase of the irradiation dose, and the newly generated alpha-prime martensite shows the characteristics of continuous distribution.

[0092] Combined with the characterization results of XRD, TEM and the like, it is confirmed that there is a large range of martensitic phase change, and the density and size of the irradiation dislocation loop in the sample are significantly reduced, which confirms that the irradiation resistance of the material is significantly improved.

[0093] In addition, Figure 1 The relationship between the volume fraction of alpha-prime martensite in the irradiated austenitic stainless steel 304NG plate sample (GNS, treated sample) and the untreated austenitic stainless steel 304NG plate sample (CG, original sample) and the irradiation dose is shown in the figure. Figure 2 The relationship between the irradiation dislocation loop density and size in the irradiated austenitic stainless steel 304NG plate sample (GNS, treated sample) and the untreated austenitic stainless steel 304NG plate sample (CG, original sample) and the irradiation dose is shown in the figure. Figure 3 The hardening rate trend along the depth of the irradiated austenitic stainless steel 304NG plate sample (GNS, treated sample) and the untreated austenitic stainless steel 304NG plate sample (CG, original sample) before and after irradiation at a dose of 50 dpa is shown in the figure. Figure 1 It can be seen that with the increase of the irradiation dose, the volume percentage of alpha-prime martensite in the treated sample increases significantly, while the volume percentage of alpha-prime martensite in the original sample does not change obviously. The main irradiation defect in the austenitic stainless steel irradiated by iron ions is the irradiation dislocation loop. The size and density of the irradiation dislocation loop in different ion irradiated samples are counted, as shown in Figure 2As shown, it can be seen that the size and density of dislocation loops decrease significantly with the occurrence of adaptive martensitic phase transition (0-10 dpa), and even when the irradiation dose reaches 155 dpa, the irradiation dislocation loop density in the original sample is much higher than that of the treated sample, which is 26.3 times that of the treated sample. In addition, in the actual service condition, irradiation hardening is also a major problem in nuclear power structure materials, and the hardening rate of the treated sample is only about 25% compared with about 75% of the original sample (see Figure 3 Therefore, the method is an extremely effective method for improving the irradiation resistance of austenitic stainless steel.

[0094] Example 2

[0095] At 300℃, the Fe 10+ ion irradiation (0.62 MeV / U, 0-50 dpa) test was performed on the austenitic stainless steel 304NG plate sample with improved irradiation resistance obtained in Example 1.

[0096] Figure 7 At 300℃, the Fe 10+ ion irradiation, the volume percentage of α'-martensite and the distribution of irradiation damage dose. As shown, it can be seen that after the test, it is found that the α'-martensite content of the irradiated GNS sample increases with the increase of the irradiation dose. Figure 7

[0097] Figure 8 The microstructure of the sample after ion irradiation (300℃) is shown in the figure; wherein, (a) is the BF-TEM image of the control sample (i.e. the austenitic stainless steel 304NG plate sample without irradiation resistance strengthening treatment) after ion irradiation (300℃), (b) is the BF-TEM image of the austenitic stainless steel 304NG plate sample with improved irradiation resistance of the present application after ion irradiation (300℃), and (c) is the selected area electron diffraction image of the region of (b). As shown, Figure 8 It can be seen that the irradiation defects in (b) are significantly less than those in (a), and no irradiation vacancy clusters are observed in (b). As shown in (c), the austenitic stainless steel 304NG plate sample with improved irradiation resistance of the present application undergoes large-area martensitic phase transition after irradiation at 300℃. Irradiation vacancy clusters appear in the original sample under the influence of temperature, but do not exist in the treated sample, which confirms that the irradiation resistance of the sample is significantly improved.

[0098] Example 3

[0099] In this embodiment, He + ​Ion irradiation experiment (4 MeV, 10000 appm), the irradiation dose of helium ions reached 0.45 dpa.

[0100] Reference is made to Figure 10 It is shown that the content of α'-martensite is about 40% by XRD test, indicating that there is also a wide range of self-adapting martensitic phase transition phenomenon. It is proved that the method is universal under a variety of ion irradiation.

[0101] Example 4:

[0102] The embodiment provides a method for strengthening the irradiation resistance of an austenitic stainless steel, to improve the irradiation resistance of the nuclear austenitic stainless steel 304NG plate, and the main steps are as follows:

[0103] Plastic deformation treatment: the nuclear austenitic stainless steel 304NG plate is subjected to plastic deformation treatment by surface mechanical rolling technology, and the specific process parameters are as follows:

[0104] The tool bit of mechanical rolling is a WC / Co hard alloy ball (the diameter of the WC-Co hard alloy ball is 8 mm). The transverse direction of the austenitic stainless steel 304NG plate is defined as the x-axis, and the longitudinal direction is defined as the y-axis. In the specific surface mechanical rolling process: after the alloy ball contacts the sample, it continues to press down by 10 μm, then processes (rolls) a certain displacement (Ly) along the y direction of the plate, then feeds once along the x direction with a step size (Px) of 0.03 mm, then processes (rolls) a displacement of Ly along the -y direction, and then feeds once along the x direction with a step size (Px) of 0.03 mm, and so on, until the processing is completed, and the feeding rate (v) is 33 mm / s. The above process can be recorded as one treatment pass, and the embodiment processes one pass. In the above surface mechanical rolling treatment, the surface shear strain of the austenitic stainless steel part is 5-10, and the strain rate is 10 1 -10 2 / s.

[0105] Skin removal treatment: the plate after plastic deformation treatment is cut into a square sample with a size of about 10×10×2 mm 3 by wire cut electrical discharge machining, and surface electrolytic polishing treatment is performed by selecting 10% perchloric acid alcohol solution as the electrolytic polishing liquid (wherein the temperature, voltage and time of the surface electrolytic polishing treatment are: -20℃, 20V, 0.5-1.5min, that is, the surface layer is polished by 2-4 μm), to obtain the austenitic stainless steel 304NG plate after strengthening the irradiation resistance.

[0106] The specific microstructure of the surface layer of the austenitic stainless steel 304NG plate after the anti-radiation performance is strengthened in the embodiment is a second specific microstructure. Specifically, the second specific microstructure includes austenitic grains and ε-martensite, where the ε-martensite is a hexagonal close-packed phase; the size of the austenitic grains is nanoscale; and the volume fraction of the ε-martensite in the second specific microstructure is greater than 60%.

[0107] Figure 9 The figure is a characterization diagram of the surface layer microstructure of the austenitic stainless steel 304NG plate after the anti-radiation performance is strengthened in Example 4; where (a) is a transmission electron bright field image, and (b) is a selected area electron diffraction pattern of the boxed region in (a). It can be seen from Figure 9 It can be seen that, after plastic deformation, the austenitic grains evolve into ε-martensite.

[0108] At room temperature, Fe 10+ ion irradiation experiments (0.62 MeV / U, 0-40 dpa) were performed on the austenitic stainless steel 304NG plate after the anti-radiation performance was strengthened. Through TEM selected area electron diffraction analysis of the 40 dpa treated sample, it can be determined that the maximum damage region of ion irradiation has evolved from the austenitic grains and ε-martensite in the unirradiated sample to 100% α'-martensite, and the test results show that there is also a large range of self-adapting martensitic phase change.

[0109] Example 5

[0110] The embodiment provides a method for strengthening the anti-radiation performance of an austenitic stainless steel to improve the anti-radiation performance of a commercial austenitic stainless steel 304 plate, and the main steps are as follows:

[0111] Plastic deformation treatment: the commercial 304 plate is subjected to plastic deformation treatment by surface mechanical rolling technology, and the specific process parameters are as follows:

[0112] The tool bit of the mechanical rolling is a WC / Co hard alloy ball (the diameter of the WC-Co hard alloy ball is 8 mm). The transverse direction of the austenitic stainless steel 304 plate is defined as the x-axis, and the longitudinal direction is defined as the y-axis. In the specific surface mechanical rolling process:

[0113] After the hard alloy ball contacts the sample and continues to press down by 40 μm, then a displacement (L y ) is processed (rolled) along the y direction of the plate, and then a feed of 0.03 mm is performed along the x direction as a step (P x ), and then a displacement (L y ) is processed (rolled) along the -y direction, and then a feed of 0.03 mm is performed along the x direction as a step (P xThe sample is processed in one feed cycle, and this cycle is repeated until the processing is complete. The feed rate (v) is 33 mm / s. This process can be counted as one processing pass; in this embodiment, one processing pass is performed. During the surface mechanical rolling treatment, the surface shear strain of the austenitic stainless steel part is set to 5–10, and the strain rate is 10. 1 ~10 2 / s.

[0114] Surface removal: The plastically deformed sheet is cut into approximately 10×10×2mm pieces using wire electrical discharge machining. 3 The cube-shaped samples were subjected to surface electropolishing treatment using a 10% perchloric acid alcohol solution as the electropolishing solution (the temperature, voltage, and time of the surface electropolishing treatment were -20℃, 20V, and 30s, respectively), resulting in austenitic stainless steel 304 plates with enhanced radiation resistance and commercial 304 plates.

[0115] XRD testing revealed that the microstructure of the surface layer of the radiation-resistant commercial 304 stainless steel sheet was a second specific microstructure, which consisted of austenite grains and ε-martensite, wherein the ε-martensite was a close-packed hexagonal phase; the austenite grains were nanometer-sized; and the volume fraction of ε-martensite in the second specific microstructure was >60%.

[0116] The commercially available 304 stainless steel sheet with enhanced radiation resistance in this embodiment was subjected to Fe treatment at room temperature. 10+ Ion irradiation. Findings: The treated commercial 304 sample also exhibited adaptive martensitic phase transformation under irradiation.

[0117] Comparative Example 1

[0118] Comparative Example 1: The first type of commercial austenitic stainless steel 304L sheet sample was subjected to equal channel extrusion (ECAP) treatment, and the second type of commercial austenitic stainless steel 304L sheet sample was subjected to high pressure torsion (HPT) treatment. In the first type of commercial austenitic stainless steel 304L sheet sample, equiaxed ultrafine grains (grain size ~500nm) were formed, and in the second type of commercial austenitic stainless steel 304L sheet sample, nanocrystals (grain size ~89nm) were formed.

[0119] Here, although the equal channel extrusion (ECAP) and high pressure torsion (HPT) treatments in Comparative Example 1 are also techniques for plastic deformation, they do not form the specific microstructure of this invention.

[0120] The original commercial austenitic stainless steel 304L plate and the two treated commercial 304L samples were irradiated with iron ions (0.066 MeV / U) at room temperature. It was observed that the irradiation-induced martensitic phase transformation was inhibited with the decrease of the grain size. It was shown that the self-adapting martensitic phase transformation could not be induced by only plastic deformation treatment without forming the specific microstructure organization described in the method.

[0121] Comparative Example 2

[0122] Comparative Example 2 provides a method for strengthening the radiation resistance of an austenitic stainless steel to improve the radiation resistance of nuclear austenitic stainless steel 304NG plate. The difference between Comparative Example 2 and Example 1 is that:

[0123] In the surface mechanical rolling treatment, the surface shear strain of the austenitic stainless steel part is greater than 15, and the strain rate is 10 3 ~ 10 4 / s, so that the grains of the austenitic stainless steel are refined into equiaxed nanocrystals, and at this time the dislocation density inside the grains is low.

[0124] The plastic deformation processing parameters of Comparative Example 2 make it impossible to form the first specific microstructure and the second specific microstructure in the austenitic stainless steel 304NG plate.

[0125] Comparative Example 3

[0126] Comparative Example 3 provides a method for strengthening the radiation resistance of an austenitic stainless steel to improve the radiation resistance of nuclear austenitic stainless steel 304NG plate. The difference between Comparative Example 3 and Example 1 is that:

[0127] In the surface mechanical rolling treatment, the surface shear strain of the austenitic stainless steel part is less than 5, and the strain rate is less than 10 / s, so that the grain size of the austenitic stainless steel cannot be effectively refined.

[0128] The plastic deformation processing parameters of Comparative Example 3 make it impossible to form the first specific microstructure and the second specific microstructure in the austenitic stainless steel 304NG plate.

[0129] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification, equivalent change and modification of the above embodiment according to the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A method for enhancing the radiation resistance of austenitic stainless steel, characterized in that, It includes the following steps: Plastic deformation treatment steps: The austenitic stainless steel parts are subjected to plastic deformation treatment to form a specific microstructure in the austenitic stainless steel parts; wherein, the specific microstructure can promote the transformation of the austenitic phase into a continuous martensite phase under irradiation conditions. Skin removal process: The austenitic stainless steel parts after plastic deformation are subjected to skin removal process so that the surface microstructure of the austenitic stainless steel parts is the specific microstructure described above, thereby obtaining austenitic stainless steel with enhanced radiation resistance.

2. The method for enhancing the radiation resistance of austenitic stainless steel according to claim 1, characterized in that, The specific microstructure organization includes a first specific microstructure organization; wherein, in the first specific microstructure organization: Stacking fault density within austenite grains greater than 10 14 m -2 The grain boundaries include Σ3(111) grain boundaries and small-angle grain boundaries; wherein the size of the austenite grains is in the nanometer range; preferably, the size of the austenite grains is 30-100 nm.

3. The method for enhancing the radiation resistance of austenitic stainless steel according to claim 1, characterized in that, The specific microstructure organization includes a second specific microstructure organization; wherein... The second specific microstructure includes: austenite grains and ε-martensite, wherein the ε-martensite is a close-packed hexagonal phase; wherein the size of the austenite grains is in the nanometer range; preferably, the size of the austenite grains is 70-100 nm; preferably, in the second specific microstructure, the volume fraction of the ε-martensite is >60%.

4. The method for enhancing the radiation resistance of austenitic stainless steel according to any one of claims 1-3, characterized in that, Prior to the plastic deformation treatment step, the procedure further includes: Milling treatment: The surface of the austenitic stainless steel part is milled flat; Preferably, the surface roughness Ra of the milled austenitic stainless steel part is less than 0.3 μm.

5. The method for enhancing the radiation resistance of austenitic stainless steel according to any one of claims 1-4, characterized in that, In the plastic deformation treatment step: Plastic deformation of the austenitic stainless steel parts is achieved by mechanically rolling the surface of the austenitic stainless steel parts.

6. The method for enhancing the radiation resistance of austenitic stainless steel according to claim 5, characterized in that, In the surface mechanical rolling process: The rolling tool is used to press down on the material after contact to deform the material; preferably, the pressing displacement of the rolling tool is 10 to 60 μm.

7. The method for enhancing the radiation resistance of austenitic stainless steel according to claim 5, characterized in that, In the aforementioned surface mechanical rolling treatment, the surface shear strain of the austenitic stainless steel part is reduced to <100, and the strain rate is reduced to <10. 4 / s.

8. The method for enhancing the radiation resistance of austenitic stainless steel according to any one of claims 1-7, characterized in that, The skin removal process is a polishing process; preferably, the polishing process is an electrolytic polishing process. More preferably, in the electropolishing process: the electrolyte is a perchloric acid-alcohol solution with a concentration of 10±2%; More preferably, the parameters of the electropolishing treatment are as follows: the temperature of the electropolishing treatment is -20 to 25°C, and the voltage of the electropolishing treatment is 20 to 25V.

9. The method for enhancing the radiation resistance of austenitic stainless steel according to any one of claims 1-8, characterized in that, The austenitic stainless steel parts are nuclear austenitic stainless steel parts, 304 austenitic stainless steel parts, and 301 austenitic stainless steel parts.

10. The method for enhancing the radiation resistance of austenitic stainless steel according to claims 1-8, characterized in that, The austenitic stainless steel parts are nuclear-grade 304NG austenitic stainless steel parts; wherein... During surface mechanical rolling treatment, the surface shear strain of the austenitic stainless steel part is controlled to be 10-15 and the strain rate to be 10. 2 ~10 3 When the time is / s, the specific microstructure includes the first specific microstructure; preferably, in the skin removal process, when the electropolishing time is controlled to be 0.5-1.5min, the surface microstructure of the austenitic stainless steel part is the first specific microstructure. During surface mechanical rolling treatment, the surface shear strain of the austenitic stainless steel part is controlled to be 5-10 and the strain rate to be 10. 1 ~10 2 When / s, the specific microstructure includes a second specific microstructure; preferably, in the skin removal step, the electropolishing time is controlled to be 0.5-1.5min, so that the surface microstructure of the austenitic stainless steel part is the second specific microstructure.

11. The method for enhancing the radiation resistance of austenitic stainless steel according to any one of claims 1-8, characterized in that, The austenitic stainless steel part is a 304 austenitic stainless steel part; wherein... In surface mechanical rolling treatment, the surface shear strain of austenitic stainless steel parts is controlled to be 5–10, and the strain rate is 10. 1 ~10 2 When the time is / s, the specific microstructure includes a second specific microstructure; preferably, in the skin removal step, when the electropolishing time is controlled to be 0.5-1.5min, the surface microstructure of the austenitic stainless steel part is the second specific microstructure.

12. An austenitic stainless steel part with enhanced radiation resistance, characterized in that, The radiation-resistant enhanced austenitic stainless steel part includes a specific microstructure; wherein, the specific microstructure can promote the transformation of the austenitic phase into a continuous martensite phase under irradiation conditions; Preferably, the surface microstructure of the radiation-resistant enhanced austenitic stainless steel part is the specific microstructure microstructure; more preferably, the internal microstructure of the radiation-resistant enhanced austenitic stainless steel part, in addition to the surface microstructure, includes the specific microstructure microstructure. Preferably, the specific microstructure includes a first specific microstructure; wherein, in the first specific microstructure, the stacking fault density within the austenite grains is greater than >10. 14 m -2 The grain boundaries include Σ3(111) grain boundaries and small-angle grain boundaries, wherein the size of the austenite grains is in the nanometer range; preferably, the size of the austenite grains is 30-100 nm. Preferably, the specific microstructure includes a second specific microstructure; the second specific microstructure includes: austenite grains and ε-martensite, wherein the ε-martensite is a close-packed hexagonal phase; wherein the size of the austenite grains is nanometer-scale; preferably, the size of the austenite grains is 70-100 nm; preferably, in the second specific microstructure: The volume fraction of ε-martensite is >60%; Preferably, the radiation-resistant enhanced austenitic stainless steel part is obtained by strengthening the austenitic stainless steel using the radiation-resistant enhancement method of any one of claims 1-11.

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