Electrolytic polishing method for EBSD of zirconium alloy and stainless steel welded joint

Abstract

The application provides an electrolytic polishing method for a zirconium alloy and stainless steel welded joint EBSD sample, which comprises the following steps: (1) cutting a zirconium alloy and stainless steel welded joint sample to be detected; (2) mechanically polishing the cross section of the welded joint by using sandpaper; (3) preparing an electrolytic polishing solution; (4) placing the polished sample in step (2) into the electrolytic polishing solution in step (3) to perform electrolytic polishing treatment; (5) placing the sample after electrolytic polishing in step (4) into a container containing alcohol, ultrasonic cleaning the container containing the sample for 5 min, and then taking out the sample and blowing cold air by using a hair dryer until no water stains are left, so that the EBSD sample with a smooth and bright surface is obtained. By adjusting the proportion of the electrolytic polishing solution and optimizing the electrolytic polishing process, the polishing and stress layer removal of the cross section of the zirconium alloy and stainless steel welded joint sample are realized, and the EBSD sample detection calibration rate is high.

Description

Technical Field

[0001] This invention belongs to the field of materials science testing and characterization technology, specifically relating to an EBSD electropolishing method for zirconium alloy and stainless steel welded joints. Background Technology

[0002] Zirconium alloys are widely used in water-cooled reactor structural materials, such as fuel rod cladding, positioning grids, and end plugs, due to their small neutron absorption cross-section, excellent corrosion resistance, and good mechanical and machinability. In recent years, the rapid development of my country's nuclear power industry has further increased the potential demand for zirconium alloy processed materials in the nuclear power field. However, zirconium, as a non-ferrous metal, is relatively expensive, and there is overcapacity in primary product production, resulting in high pollution and low efficiency for the overall industry. Therefore, improving the technological content and added value of zirconium products is of great significance. In contrast, stainless steel is inexpensive and has excellent mechanical and machinability, making it widely used in reactor core external support structures. Against this backdrop, achieving high-quality, high-reliability connections between zirconium alloys and stainless steel not only has significant economic and safety benefits but also holds important value for the theoretical research and practical application of related connection technologies.

[0003] Joining dissimilar metals like zirconium alloys and steel remains a significant challenge. The two metals exhibit substantial differences in thermophysical properties, making it prone to forming brittle intermediate phases and resulting in defects such as cracks during welding. Research on the causes and initiation mechanisms of cracks in zirconium alloy-stainless steel welded joints is limited and lacks depth.

[0004] EBSD technology uses a high-energy electron beam to irradiate the sample surface, and the interaction between the electron beam and the sample produces Kikuchi patterns. These diffraction patterns can reflect information such as the crystal symmetry, lattice parameters, and crystal plane angles of the sample, thereby enabling more in-depth characterization and analysis of cracks in welded joints, such as determining whether the grain orientations on both sides of the crack are consistent.

[0005] To further study and characterize the welding crack defects and their formation mechanism between zirconium alloys and stainless steel, it is urgent to develop a method for preparing EBSD samples of zirconium alloy-stainless steel welded joints, so as to optimize the welding process in a more targeted manner. Summary of the Invention

[0006] To address the issue of the need for refrigeration in current zirconium alloy electropolishing processes, the present invention aims to provide a method for preparing EBSD samples of zirconium alloy and stainless steel welded joints at room temperature, which is convenient, low-cost, and has a high calibration rate.

[0007] An EBSD electropolishing method for zirconium alloy and stainless steel welded joints specifically includes the following steps:

[0008] (1) Cut out the zirconium alloy and stainless steel welded joint sample to be tested;

[0009] (2) Use sandpaper to mechanically grind the cross-section of the welded joint;

[0010] (3) Prepare the electrolytic polishing solution;

[0011] (4) Place the polished sample from step (2) into the electropolishing solution from step (3) for electropolishing treatment;

[0012] (5) Place the sample that has been electropolished in step (4) into a container filled with alcohol, and then ultrasonically clean the container containing the sample for 5 minutes. After that, take it out and dry it with a hair dryer until there are no water stains. In this way, a bright and smooth EBSD sample is obtained.

[0013] Preferably, the weld joint cut in step (1) is located in the middle of the sample, and the oil stains on the sample surface are washed away with water and alcohol.

[0014] Preferably, in step (2), 600#, 1000#, 2000#, 4000# and 5000# sandpaper are used in sequence to remove the oxide scale on the surface to be tested, the surface to be tested is polished flat, the previous scratch is completely removed and the sandpaper is replaced, and the sample is rotated 90°.

[0015] Preferably, the sample that has been polished in step (2) is placed in a container filled with alcohol and ultrasonically cleaned for 2 min.

[0016] Preferably, the electropolishing solution in step (3) is a mixed solution composed of perchloric acid and ethanol.

[0017] Preferably, the volume percentage of perchloric acid in step (3) is 3-6%, and the volume percentage of ethanol is 94-97%.

[0018] Preferably, the concentration of the perchloric acid solution is 70-72%, and the concentration of the ethanol solution is 99% or higher.

[0019] Preferably, in step (4), the sample is connected to the anode, the tantalum plate is connected to the cathode, the electrolytic polishing voltage is 20~30 V, the temperature is 15~25 ℃, the polishing time is 20~60 s, and the sample needs to be shaken slightly during polishing.

[0020] Preferably, the method for judging the success of electropolishing of a sample in step (5) is that the weld area is clean and bright.

[0021] Preferably, in step (5), the sample surface is dried with cold air from a hair dryer along one side until there are no water stains.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) The electropolishing method of the present invention is applicable to samples of zirconium alloy and stainless steel welded joints. After electrolysis, the weld area is bright and smooth. The electropolishing solution is simple and convenient to prepare. The raw materials are all common chemical raw materials. It can be operated in the laboratory fume hood. It can be prepared and used immediately and can replace commercial electropolishing solution.

[0024] (2) Electrolysis can be completed at room temperature, eliminating the need for conventional low-temperature electrolysis of zirconium alloys and reducing the material cost of electrolysis. Attached Figure Description

[0025] Figure 1 A flowchart of an EBSD electropolishing method for a zirconium alloy and stainless steel welded joint provided in this embodiment of the invention.

[0026] Figure 2 The figure shows the EBSD test results of the zirconium alloy and stainless steel welded joint specimen prepared in the embodiment of the present invention. Detailed Implementation

[0027] To enable those skilled in the art to better understand this technical solution, the specific embodiments of the present invention will be further described in detail below with reference to examples, but are not limited thereto.

[0028] The specimens used in this invention are electron beam welded specimens of zirconium alloy and stainless steel. The zirconium alloy is domestic Zr-4 alloy, and the stainless steel is 316L stainless steel. The thickness of the plates is 1 mm.

[0029] Use an electrical discharge wire cutting machine to cut a 10 mm × 10 mm × 1 mm sample from the welded joint, and wipe off the surface oil with water and alcohol.

[0030] First, use 600# sandpaper to polish the test section to remove the surface oxide scale. After removing all the previous scratches, change the sandpaper and rotate the sample 90°. Then, change to 1000#, 2000#, 4000# and 5000# sandpaper in sequence to polish the test section smooth.

[0031] Place the polished sample into a beaker containing alcohol and ultrasonically clean it for 2 minutes to remove any remaining fine metal particles from the surface.

[0032] Prepare an electrolytic polishing solution by using a 70-72% perchloric acid solution and an ethanol solution with a concentration of 99% or higher. The ratio of perchloric acid to ethanol in the electrolytic polishing solution is 1:17. First, add 17 parts of ethanol solution, then add 1 part of perchloric acid solution, and stir to mix evenly.

[0033] Connect the sample to the positive electrode and the tantalum plate to the negative electrode. Perform electrolytic polishing on the sample at a voltage of 25 V for 30 s. After electrolysis, place the sample in a beaker containing alcohol and ultrasonically clean it for 5 min to remove any residual electrolytic polishing solution from the surface.

[0034] After ultrasonic cleaning, remove the sample and use a hairdryer on the cool setting to dry it along the direction parallel to the plate until there are no water stains left on the surface.

[0035] EBSD analysis was performed on the electropolished sample prepared in this case, and the EBSD results are as follows: Figure 1 As shown, its calibration rate was measured to be 97.27%.

[0036] Finally, it should be clarified that the above specific embodiments are further detailed descriptions of the present invention and not limitations. Referring to the above examples, those skilled in the art should understand that modifications or equivalent substitutions to the content of the present invention within the spirit and principles of the technical solution of the present invention are all within the protection scope of the present invention.

Claims

1. A method for EBSD electropolishing of zirconium alloys and stainless steel, characterized in that, Includes the following steps: (1) Cut out the zirconium alloy and stainless steel welded joint sample to be tested; (2) Use sandpaper to mechanically grind the cross-section of the welded joint; (3) Prepare the electrolytic polishing solution; (4) Place the polished sample from step (2) into the electropolishing solution from step (3) for electropolishing treatment; (5) Place the sample that has been electropolished in step (4) into a container filled with alcohol, and then ultrasonically clean the container containing the sample for 5 minutes. After that, take it out and dry it with a hair dryer until there are no water stains. In this way, a bright and smooth EBSD sample is obtained.

2. The EBSD electropolishing method for zirconium alloy and stainless steel welded joints according to claim 1, characterized in that, In step (3), the electrolytic polishing solution is a mixture of perchloric acid and ethanol, with perchloric acid accounting for 3-6% by volume and ethanol accounting for 94-97% by volume.

3. The EBSD electropolishing method for zirconium alloy and stainless steel welded joints according to claim 1, characterized in that, The concentration of the perchloric acid solution in step (3) is 70-72%, and the concentration of the ethanol solution is 99% or higher.

4. The EBSD electropolishing method for zirconium alloy and stainless steel welded joints according to claim 1, characterized in that, In step (4), the sample is connected to the anode and the tantalum plate is connected to the cathode. The electrolytic polishing voltage is 20~30 V, the temperature is 15~25 ℃, and the polishing time is 20~60 s.

5. The EBSD electropolishing method for zirconium alloy and stainless steel welded joints according to claim 1, characterized in that, In step (5), use a hairdryer to blow the sample surface dry along one side until there are no water stains.

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