Method for realizing matrix interface strengthening in lead-bismuth environment
By controlling oxygen and applying low-stress pulsating cyclic loading in a lead-bismuth environment, a stable oxide layer and matrix interface were prepared, solving the incompatibility problem between the in-service material and LBE in LFR, achieving self-healing and long-lasting strengthening effects of the material, and improving the safety and service performance of LFR.
Patent Information
- Application Number
- CN202511571404.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-30
- Publication Date
- 2026-01-09
AI Technical Summary
Under cyclic stress, the incompatibility between the materials in service in LFR and the liquid lead-bismuth environment leads to a rapid deterioration of the material's fracture toughness, elongation, and fatigue performance. Traditional interface strengthening methods are easily damaged and cannot be repaired under stress.
A stable oxide layer and substrate interface were prepared in a lead-bismuth environment by controlling oxygen and low-stress pulsating cyclic loading, forming a coherent interface with self-healing ability. The oxygen content was controlled at 5×10-6~5×10-7wt% by using a mixed gas of 95%Ar and 5%H2, and the loading stress was 100MPa~400MPa for 400~1000 hours.
It achieves stability, durability, and repairability at the oxide layer and substrate interface, improves the mechanical properties of the material, solves the incompatibility problem between LFR service materials and LBE, and provides a guarantee for the long-term safe service of the fourth-generation LFR.
Smart Images
Figure CN121295089A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of metal surface strengthening, and particularly relates to a method for realizing substrate interface strengthening in a lead-bismuth environment. BACKGROUND
[0002] With the rapid development of global economy, the problems of environmental pollution and energy shortage caused by fossil fuels gradually appear. Nuclear energy, as an important energy form, has many advantages such as high efficiency, cleanliness, stability and economy, and is considered as one of the mainstream energy in the future. As one of the most potential reactor types of the fourth generation, the lead-bismuth cooled fast reactor (LFR) is an important part of the nuclear energy technology system and one of the key technologies to realize the efficient, safe and sustainable use of nuclear energy due to its inherent safety, good heat conduction and suitability for multiple scenarios. Liquid lead-bismuth (LBE) is used as the coolant of LFR and the spallation target material of the accelerator driven system due to its low melting point, high boiling point, small neutron absorption cross section and stable chemical properties. However, with the rapid development of LRF and the increasing complexity and severity of the service environment, the comprehensive performance of the service materials in LFR will face severe challenges. This is because when the service materials are exposed to the LBE environment, they will face problems such as liquid metal embrittlement and liquid metal corrosion, which will cause the fracture toughness, elongation and fatigue performance of the service materials to deteriorate rapidly. Therefore, the compatibility problem of the service materials and LBE is one of the key bottlenecks restricting the stable development of LFR. At present, the construction of nanoscale coherent or semi-coherent interface through oxygen control strategy has attracted much attention because the coherent or semi-coherent interface between the oxide layer and the substrate can effectively hinder the movement of dislocations, thereby showing better strengthening effect and weakening the compatibility of the service materials and LBE. Although a large number of studies have revealed the strength of the bonding between the oxide layer and the substrate under different oxygen contents in static corrosion, the effect of different loading modes and cyclic loads on the service process of engineering components is ignored. Cyclic stress will cause plastic deformation and grain boundary migration of the substrate, thereby affecting the formation of the interface between the oxide layer and the substrate. Generally, traditional interface strengthening is mainly achieved through surface treatment processes such as shot peening, cold rolling, laser shock peening and coating. Although the above strengthening methods have achieved good results in the protection of corrosion performance, mechanical properties and fatigue performance, the residual deformation caused by surface extrusion during the preparation process will change the initial microstructure and reduce the service performance. In addition, once the surface strengthened structure prepared by the above process is damaged (even under small stress), it will not heal, thereby reducing the effectiveness and timeliness of interface strengthening. SUMMARY
[0003] The application aims to solve the problem of incompatibility between materials and LBE in LBE environment under the action of cyclic stress, and provides a method for realizing matrix interface strengthening in lead-bismuth environment, which prepares a stable oxide layer and matrix interface in liquid lead-bismuth environment under the action of low stress pulsating loading, and has the characteristics of stability, durability and dynamic repairability, thereby providing a strong guarantee for long-term safety service of the fourth generation LFR.
[0004] In order to solve the above technical problems, the application is implemented by the following technical solutions:
[0005] The application provides a method for realizing matrix interface strengthening in lead-bismuth environment, which comprises the following steps:
[0006] (1) ultrasonic cleaning is performed on the target sample to ensure that the surface is free of stains;
[0007] (2) the target sample is clamped in a sealed cavity of a fatigue loading device, and the load of the fatigue loading device is servoed to zero; solid lead-bismuth is added to the sealed cavity and heated by a heating furnace outside the sealed cavity, so that the lead-bismuth is completely melted and the target sample is submerged;
[0008] (3) ensure that the sealed cavity is completely sealed and the PLC oxygen control system is connected, and then continuously introduce a reducing gas with a flow rate of 30-50 mL / min into the sealed cavity;
[0009] (4) the temperature of the heating furnace is increased to 170-180℃, and then the reducing gas with a flow rate of 30-50 mL / min is used for gas washing;
[0010] (5) under the condition that the reducing gas with a flow rate of 30-50 mL / min is continuously introduced, the temperature of the heating furnace is increased to 445℃-455℃ for oxygen reduction treatment, until the oxygen content in the sealed cavity reaches 5×10 -6 ~5×10 -7 wt%, the flow rate of the reducing gas is reduced to 6-10 mL / min and PLC automatic control is performed;
[0011] (6) under the condition of PLC automatic control, low stress pulsating cyclic load is applied to the target sample;
[0012] (7) after the loading is completed, the temperature of the heating furnace is reduced, the target sample is taken out and the lead-bismuth on the surface of the target sample is cleaned.
[0013] Further, in step (2), the temperature of the heating furnace is set to 140-160℃.
[0014] Further, in steps (3)-(5), the reducing gas is Ar and H2 mixed gas; wherein the volume fraction of Ar is 95%, and the volume fraction of H2 is 5%.
[0015] Furthermore, in step (4), the gas washing time is 15 to 18 hours.
[0016] Furthermore, in step (5), 5×10 -6 ~5×10 -7 The voltage displayed by the PLC oxygen control system for oxygen content in the wt% range is 224~292mV.
[0017] Furthermore, in step (5), the applied load of the low-stress pulsating cyclic load is 100MPa~400MPa, and the duration is 400~1000 hours.
[0018] The beneficial effects of this invention are:
[0019] This invention proposes a method for strengthening the matrix interface in a lead-bismuth environment, which is achieved through oxygen-controlled LBE conditions and low-stress controlled pulsating cycle control. The prepared oxide layer and matrix interface have stability, durability and repairability, thus solving the incompatibility problem between structural materials and LBE in LFR, and has been supported by experimental results and microscopic analysis. Attached Figure Description
[0020] Figure 1 This is a flowchart of the method for strengthening the matrix interface in a lead-bismuth environment according to the present invention.
[0021] Figure 2 This is an oxygen control curve during the preparation process of Example 1 of the present invention.
[0022] Figure 3 This is a projection image of the oxide layer substrate interface prepared in Example 1 of the present invention.
[0023] Figure 4 This is a scanning electron microscope image of the self-healing oxide layer prepared in Example 1 of the present invention.
[0024] Figure 5 Scanning electron microscope (SEM) images of the oxide layer and substrate interface prepared in Comparative Example 1 of this invention: (a) asymmetric loading condition with low stress amplitude; (b) asymmetric loading condition with low average stress; (c) symmetric loading condition with low stress.
[0025] Figure 6 The images show the morphology of the surface oxide layer under different oxygen contents and different fatigue loads. Detailed Implementation
[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.
[0027] Example 1
[0028] like Figure 1 As shown, this embodiment provides a method for strengthening the matrix interface in a lead-bismuth environment, which is carried out according to the following steps:
[0029] Step 1. Immerse the target specimen in alcohol for ultrasonic cleaning for 10 minutes, then remove the target specimen and dry the surface alcohol with a hair dryer.
[0030] Step 2. Place the target specimen on the fatigue testing machine fixture, tighten the screws on the fixture, then turn on the load servo of the testing machine and set the target load to zero. Then add solid LBE into the sealed cavity of the fatigue testing machine, set the temperature of the heating furnace outside the sealed cavity to 160°C, and heat until the solid LBE is completely melted. The amount of lead bismuth should be enough to submerge the target specimen by 1 cm.
[0031] Step 3. Add a graphite gasket to the sealing groove of the fatigue testing machine to ensure sealing. Then, put on the sealing cover of the fatigue testing machine and tighten all the large screws on the top of the cover. Connect the reducing gas path of the sealing chamber, the oxygen sensor and the PLC controller. Then, turn on the pressure reducing valve of the reducing gas cylinder and inject reducing gas at a rate of 50 mL / min. Turn on the PLC controller to manual mode and wait for about 10 minutes until the one-way valve quickly releases gas.
[0032] The PLC control system is used to control the oxygen content by controlling the flow rate of reducing gas.
[0033] The reducing gas is a mixture of 95% Ar and 5% H2 by volume.
[0034] Step 4. Set the heating furnace temperature to 180℃, turn on the PLC controller to manual mode, and then continue to inject reducing gas into the sealed cavity at a rate of 50mL / min for 15~18 hours for gas washing.
[0035] Step 5. With a continuous reducing gas flow of 50 mL / min, first add sufficient insulation cotton around the sealed cavity to ensure insulation effect. Then set the temperature of the heating furnace to 450℃ and start the self-diagnosis mode until the temperature stabilizes at 450℃. After the voltage value drops to about 250 mV, reduce the reducing gas flow to 6 mL / min~10 mL / min, and then start the PLC automatic control mode.
[0036] Step 6. Using the formulas for oxygen content, temperature, and voltage:
[0037] ;
[0038] In the formula, E is the potential difference measured by the oxygen sensor (in V), T is the temperature of the LBE (in K), and C0 is the oxygen concentration.
[0039] The calculated oxygen content ranges from 5 × 10⁻⁶. -6 ~5×10 -7 The voltage value corresponding to wt% is approximately 224~292mV.
[0040] Therefore, after the voltage value automatically controlled by the PLC stabilized at 224~292 mV, the target sample held inside the sealed cavity was subjected to a cyclic stress-controlled low-cycle test under controlled oxygen LBE at 445℃~455℃, with an applied stress ratio of 0 and an applied load of 400 MPa. The fatigue test was set to last for approximately 400 hours. Considering that low stress application can promote oxide layer growth, when the applied stress is less than 400 MPa, the pre-exposure time should be extended to more than 400 hours.
[0041] Step 7. After the experiment, lower the furnace temperature to 160℃~170℃, turn on the large fan to cool down rapidly, and remove the sample once the target temperature is reached. Perform LBE cleaning on the surface using a 1:1:3 mixture of alcohol, glacial acetic acid, and hydrogen peroxide. Then, use wire cutting to cut 5 mm long round bars at the gauge length of the sample. Use SEM-EDS and TEM to characterize the surface morphology of the micron- to nano-scale oxide layer and substrate interface, and analyze the results.
[0042] Figure 2 This is an oxygen control curve diagram from the preparation process of an embodiment of the present invention. Figure 2 It can be seen that the oxygen control effect was good throughout the process.
[0043] Figure 3 A projection image of the oxide layer substrate interface prepared for the example, from... Figure 3 It can be seen that a completely coherent interface was formed between the oxide layer and the substrate after cyclic loading, which indicates that the oxide layer and the substrate have a very good bonding performance.
[0044] Figure 4 Scanning electron microscope (SEM) images of the self-healing oxide layer prepared for the example, from... Figure 4 It can be seen that although the oxide layer under low cyclic stress experienced local cracking, the oxide layer achieved self-repair function at the crack location through redox reaction and coating.
[0045] Comparative Example 1
[0046] The substrate interface and oxide layer were prepared according to the process of Example 1, except that in step 6, (1) asymmetric loading conditions with low stress amplitude; (2) asymmetric loading conditions with low average stress; and (3) symmetric loading conditions with low stress were used.
[0047] Figure 5 shows scanning electron microscope images of the oxide layer and substrate interface prepared under different loading conditions in Comparative Example 1. Figure 5 In (a), the oxide layer matrix interface formed under asymmetric loading conditions with low stress amplitude shows that there are pores and obvious cracking at the oxide layer matrix interface, which indicates that the bonding performance between the oxide layer and the matrix interface is weakened. Figure 5 (b) The oxide layer-matrix interface formed under asymmetric loading conditions with low average stress shows that there are pores at the oxide layer-matrix interface and the self-healing behavior of the oxide layer is reduced, which indicates that the bonding performance between the oxide layer and the matrix interface is weakened. Figure 5 In (c), pores exist inside the oxide layer and at the oxide layer-matrix interface under low-stress symmetrical loading conditions, indicating that the bonding performance between the oxide layer and the matrix interface is weakened.
[0048] To investigate the necessity of exploring the formation mechanism of the oxide layer under oxygen-controlled lead-bismuth, saturated oxygen lead-bismuth and oxygen-controlled lead-bismuth (5×10⁻⁶) were subjected to oxidation tests for 1-2 days. -6 ~5×10 -7 wt%) and low oxygen lead bismuth (10 -8 ~10 -9 Tests under static corrosion and fatigue loading at wt%) provided direct evidence through microscopic characterization. For example... Figure 6 As shown, it can be observed that the surface oxide layer provides enhanced protection to the substrate in oxygen-controlled lead-bismuth environments under both static corrosion and fatigue loading conditions.
[0049] Therefore, this invention provides a method for constructing surface strengthening of service materials under cyclic stress LBE environment. This method can solve the incompatibility problem between service materials and LBE, and provide strong guarantee for the long-term safe service of fourth-generation LFR.
[0050] The technical solutions disclosed and proposed in this invention can be implemented by those skilled in the art by appropriately modifying the conditions and routes, etc. Although the methods and preparation techniques of this invention have been described through preferred embodiments, those skilled in the art can obviously modify or recombine the methods and technical routes described herein without departing from the content, spirit, and scope of this invention to achieve the final preparation technique. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the spirit, scope, and content of this invention.
Claims
1. A method for strengthening the matrix interface in a lead-bismuth environment, the method comprising the following steps: (1) Perform ultrasonic cleaning on the target sample to ensure that the surface is free of stains; (2) The target sample is clamped in the sealed cavity of the fatigue loading device and the load of the fatigue loading device is set to zero; solid lead bismuth is added to the sealed cavity and heated by a heating furnace outside the sealed cavity to completely melt the lead bismuth and submerge the target sample. (3) Ensure that the sealed cavity is completely sealed and the PLC oxygen control system is connected, and then continuously introduce reducing gas into the sealed cavity at a flow rate of 30~50mL / min; (4) Raise the temperature of the heating furnace to 170~180℃, and then wash the gas with a reducing gas at a flow rate of 30~50mL / min; (5) With a continuous flow of reducing gas at a flow rate of 30~50 mL / min, the temperature of the heating furnace is raised to 445℃~455℃ for oxygen reduction treatment until the oxygen content inside the sealed cavity reaches 5×10⁻⁶. -6 ~5×10 -7 Within the wt% range, reduce the flow rate of the reducing gas to 6~10mL / min and implement PLC automatic control; (6) Under PLC automatic control, the furnace temperature is maintained at 445℃~455℃, and the target sample is subjected to low-stress pulsating cyclic load. (7) After loading is completed, reduce the temperature of the heating furnace, remove the target sample and clean the lead and bismuth from the surface of the target sample.
2. The method for strengthening the matrix interface in a lead-bismuth environment according to claim 1, characterized in that, In step (2), the temperature of the heating furnace is set to 140~160℃.
3. The method for strengthening the matrix interface in a lead-bismuth environment according to claim 1, characterized in that, In steps (3)-(5), the reducing gas is a mixture of Ar and H2; wherein the volume fraction of Ar is 95% and the volume fraction of H2 is 5%.
4. The method for strengthening the matrix interface in a lead-bismuth environment according to claim 1, characterized in that, In step (4), the gas washing time is 15 to 18 hours.
5. The method for strengthening the matrix interface in a lead-bismuth environment according to claim 1, characterized in that, In step (5), 5×10 -6 ~5×10 -7 The voltage displayed by the PLC oxygen control system for oxygen content in the wt% range is 224~292mV.
6. The method for strengthening the matrix interface in a lead-bismuth environment according to claim 1, characterized in that, In step (5), the applied load of the low-stress pulsating cyclic load is 100~400MPa and the duration is 400~1000 hours.