Test method of metallographic etchant for morphology analysis of nuclear power nickel-based alloy carbide

Abstract

The invention discloses a metallographic erosion test method for nuclear power nickel-based alloy carbide morphology analysis. The metallographic erosion test method comprises the following steps: step 1, coarse grinding; step 2, fine grinding and polishing: polishing the sample subjected to coarse grinding to obtain a clean and flat polished surface without scratches; step 3, putting the polished sample into a mixed solution mixed with hydrochloric acid, nitric acid and glycerol, after etching is completed, directly dipping degreasing cotton into the mixed solution mixed with 3% bromine water and methanol without flushing, wiping for one minute, then flushing the surface of the sample with clear water, and finally flushing the sample with alcohol and drying; and 4, performing metallographic observation and analysis. By means of the method, an oxide layer and impurities on the surface of the nickel-based alloy can be effectively removed, and microstructures such as carbides can be clearly shown.

Description

Technical Field

[0001] The invention belongs to the technical field of physical detection, and in particular relates to a metallographic corrosion test method for analyzing the morphology of carbides of nuclear power nickel-based alloys. Background Art

[0002] As a clean and efficient form of energy, nuclear power plays an increasingly important role in the modern energy system. However, key nuclear power components such as evaporators and reactor pressure vessels have extremely harsh working environments and need to withstand the test of high temperature, high pressure, radiation and other factors, so the performance requirements of materials are extremely high. Nickel-based alloys have become the preferred materials for key nuclear power components due to their excellent high-temperature strength, corrosion resistance and oxidation resistance, and are widely used in aerospace, petrochemical and other fields. In these applications, carbides are an important component of nickel-based alloys, and their morphology, size and distribution have an important influence on the performance of nickel-based alloys. The presence of carbides can significantly affect the key properties of the alloy, such as high-temperature strength, corrosion resistance, oxidation resistance and wear resistance. Therefore, accurately observing and analyzing the carbide structure in nickel-based alloys is of great significance for the research and application of materials.

[0003] However, the existing metallographic etching methods for nickel-based alloy carbides have the problem of unsatisfactory etching effects. For example, when hydrochloric acid, nitric acid, copper sulfate / oxalic acid, etc. are used as etching solutions, they can often only reach the grain boundary layer, but cannot penetrate into the carbide layer; for another example, the existing methods erode unevenly. This leads to inaccurate and incomplete observation and analysis of carbides, thereby limiting the in-depth understanding and optimization of alloy properties. Therefore, a new metallographic etching experimental method for nickel-based alloy carbides is needed to improve the etching effect and the convenience of operation. Summary of the invention

[0004] The present invention has found through multiple experiments that hydrochloric acid, nitric acid, and glycerin are compounded in a certain proportion and combined with bromine water and methanol as metallographic etching agents, and used in the metallographic etching test method for nickel-based alloy carbide morphology analysis, which can effectively remove the oxide layer and impurities on the surface of the nickel-based alloy, so that the microstructures such as carbides can be clearly revealed. This provides an intuitive basis for researchers to deeply understand the internal structure of nickel-based alloys, and helps to analyze the distribution, morphology, and bonding of carbides with the matrix. Therefore, the first purpose of the present invention is to provide a metallographic etching test method for nuclear power nickel-based alloy carbide morphology analysis. The second purpose of the present invention is to provide a metallographic etching agent for nickel-based alloys.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] As a first aspect of the present invention, a metallographic corrosion test method for analyzing the morphology of carbides of a nuclear power nickel-based alloy comprises the following steps:

[0007] Step 1: Coarse grinding

[0008] Step 2: Fine grinding and polishing: Polish the rough-ground sample and add polishing agent to obtain a clean, smooth, scratch-free polished surface;

[0009] Step 3: Etching of samples

[0010] Mix hydrochloric acid, nitric acid and glycerin, put them into container No. 1 and mix them evenly for later use;

[0011] Mix 3% bromine water and methanol, put into container No. 2, and set aside;

[0012] Next, put the polished sample into container No. 1, and immerse the sample completely in the mixed solution in container No. 1; after etching, wipe the sample for one minute with absorbent cotton without rinsing, then rinse the sample surface with clean water, and finally rinse the sample with alcohol and blow dry with a hair dryer;

[0013] Step 4: Metallographic observation and analysis.

[0014] According to the present invention, the volume ratio of hydrochloric acid, nitric acid, glycerol, 3% bromine water and methanol is 9:3:1:1-1.5:10.

[0015] According to the present invention, the hydrochloric acid and nitric acid are both analytically pure reagents.

[0016] According to the present invention, the polished sample is immersed in container No. 1 for 20-30 seconds.

[0017] According to the present invention, the polishing agent is a 0.5 μm diamond polishing agent.

[0018] According to the present invention, the rough grinding step is: using sandpaper of different grits to grind the sample step by step, from coarse sandpaper to fine sandpaper, so as to remove scratches and unevenness on the surface of the sample.

[0019] Furthermore, the rough grinding step is: grinding the sample with 120#, 600#, 1000#, and 1200# sandpaper in sequence, and each time a layer of sandpaper is changed, the sample needs to be rotated 90 degrees along the grinding surface so that the new wear marks are perpendicular to the previous wear marks and cover them.

[0020] As a second aspect of the present invention, a metallographic etching agent for nickel-based alloys includes a first reagent and a second reagent, wherein the first reagent is composed of hydrochloric acid, nitric acid and glycerol, and the second reagent is 3% bromine water and methanol, and the volume ratio of hydrochloric acid, nitric acid, glycerol, bromine water and methanol is 9:3:1:1-1.5:10.

[0021] According to the present invention, the hydrochloric acid and nitric acid are both analytically pure reagents.

[0022] The metallographic corrosion test method for analyzing the morphology of nuclear nickel-based alloy carbides of the present invention has the following beneficial effects:

[0023] 1. It can effectively remove the oxide layer and impurities on the surface of nickel-based alloys, so that microstructures such as carbides can be clearly revealed. This provides an intuitive basis for researchers to gain a deeper understanding of the internal structure of nickel-based alloys, and helps to analyze the distribution, morphology, and bonding of carbides with the matrix.

[0024] 2. It can clearly show the different forms of carbides, such as spherical, chain, network, etc. This is crucial for studying the formation mechanism of carbides and their impact on alloy properties. For example, spherical carbides may improve the toughness of the alloy to a certain extent, while needle-shaped carbides may reduce the plasticity of the alloy.

[0025] 3. It can reveal the distribution law of carbides in nickel-based alloys. Uniformly distributed carbides can improve the overall performance of the alloy, while locally concentrated carbides may lead to uneven alloy performance and affect its reliability in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a 500x photograph of the nickel alloy carbide morphology analysis of Example 1.

[0027] Figure 2 This is a 1000x photograph of the nickel alloy carbide morphology analysis of Example 1.

[0028] Figure 3 This is a 1000x photograph of the nickel alloy carbide morphology analysis of Example 2.

[0029] Figure 4 This is a 2000x photograph of the nickel alloy carbide morphology analysis of Example 3.

[0030] Figure 5 This is a 990x photograph of the nickel alloy carbide morphology analysis of Example 4.

[0031] Figure 6 This is a 990x photograph of the nickel alloy carbide morphology analysis of Example 5.

[0032] Figure 7 This is a distribution diagram of conventional grain boundaries, a 1000x photo.

[0033] Figure 8 This is a 1000x photo of the carbide continuous grain boundary distribution. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with specific examples. It should be understood that the following examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0035] Example 1 A metallographic etching agent test method for analyzing the morphology of carbides in nuclear nickel-based alloys

[0036] The method of this embodiment includes the preparation of metallographic samples, etching of samples, and morphology analysis of carbides, as follows:

[0037] 1. Sampling

[0038] Select representative parts from the nickel alloy material for sampling. Cutting tools such as wire cutting, sawing, and electric spark cutting can be used to cut the sample into blocks or sheets of appropriate size for subsequent processing, ensuring that the sample will not be overheated or mechanically damaged during the cutting process, affecting the original state of the carbide. The size of the sample should be moderate to facilitate subsequent processing and observation. Generally, block samples with a side length of 10-20 mm can be selected.

[0039] It should be noted that if the sample is small or irregular in shape, it can be considered to be mounted in resin to facilitate subsequent grinding and polishing operations. Choose appropriate mounting materials and methods to ensure that the sample will not be deformed or damaged during the mounting process.

[0040] 2. Coarse grinding

[0041] Use sandpaper of different grits to grind the sample step by step, from coarse sandpaper to fine sandpaper, to remove scratches and unevenness on the sample surface. Specifically:

[0042] The sample was ground with 120#, 600#, 1000#, and 1200# sandpaper in turn. Each time a layer of sandpaper was changed, the sample was rotated 90 degrees along the grinding surface so that the new grinding marks were perpendicular to the previous grinding marks and covered them.

[0043] 3. Fine grinding and polishing

[0044] Mechanical polishing can be performed using polishing cloth and polishing agent to further improve the surface finish of the sample. Specifically:

[0045] Polish on a velvet polishing cloth and add 0.5μm diamond polishing agent to obtain a clean, smooth, scratch-free polished surface.

[0046] It should be noted that during the rough grinding and polishing process, the flatness and directional consistency of the sample surface should be maintained to avoid deformation or scratches.

[0047] 4. Sample Etching

[0048] The etchant is prepared in a fresh way, and the formula is shown in Table 1.

[0049] The hydrochloric acid and nitric acid in Table 1 are analytically pure reagents, and the bromine water is 3% bromine water.

[0050] When using, put the components in beaker No. 1 in Table 1 into beaker No. 1 and mix evenly;

[0051] Place the components in beaker 2 into beaker 3 and mix evenly.

[0052] Table 1 Etching agent configuration table

[0053]

[0054]

[0055] Note: The difference between Example 5 and other examples in the etching process is that the sample is immersed in the etchant for 20-30 seconds, and then rinsed and dipped with absorbent cotton. Examples 1-4 do not rinse and directly dip with absorbent cotton.

[0056] 5. Etching

[0057] Place the polished sample in beaker No. 1, making sure the sample is completely immersed. The purpose of etching is to create a clear contrast between the carbide and the matrix, making it easier to observe the morphology of the carbide;

[0058] Example 1-4 was immersed in beaker No. 1 for 20-30 seconds, and then wiped with absorbent cotton dipped in the mixed solution of beaker No. 2 (2 ml bromine water or 3 ml bromine water, 20 ml methanol) for one minute without rinsing. The surface was rinsed with water, and finally rinsed with alcohol and dried with a hair dryer to reveal the morphology of the carbide;

[0059] Example 5: Immerse in beaker No. 1 for 20-30s, rinse with absorbent cotton dipped in the mixed solution of beaker No. 2 (2ml bromine water or 3ml bromine water, 20ml methanol) and wipe for one minute, rinse the surface with clean water, and finally rinse with alcohol and dry with a hair dryer to show the morphology of the carbide.

[0060] It should be noted that during the etching process, the beaker can be gently shaken from time to time to ensure uniform etching. At the same time, the changes of the sample should be closely observed during the etching process to avoid excessive etching.

[0061] 6. Metallographic observation and analysis

[0062] 1. Use an electron microscope to observe the corroded samples and obtain the morphological characteristics of carbides.

[0063] 2. The size, shape, distribution, etc. of carbides can be observed under different magnifications.

[0064] 3. Combined with image analysis software, the size and quantity of carbides can be analyzed.

[0065] 4. Compare with the known standard morphology of nickel alloy carbides to determine the type and formation mechanism of carbides in the sample.

[0066] In this step, the dried sample is placed under an electron microscope scanner for observation, and the appropriate magnification and light source are adjusted to observe the morphology, size, distribution and other characteristics of the carbides. The results are shown in Table 1 and Figure 1-6 As shown;

[0067] Based on the observation results, combined with the properties and applications of nickel alloys, the formation mechanism of carbides and their impact on alloy properties are analyzed;

[0068] By observation, the carbide morphology of the sample was observed at 500 times and 1000 times and metallographic photos were taken ( Figure 1-Figure 6 ).

[0069] In summary, the metallographic etching agent test using the etching agent of Example 1 can effectively remove the oxide layer and impurities on the surface of the nickel-based alloy, so that the microstructures such as carbides can be clearly revealed.

[0070] The specific embodiments of the present invention are described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions made to the invention are also within the scope of the present invention. Therefore, the equalization changes and modifications made without departing from the spirit and scope of the present invention should be included in the scope of the present invention.

Claims

1. A metallographic corrosion test method for analyzing the morphology of carbides in nuclear nickel-based alloys, characterized in that: The steps include: Step 1: Coarse grinding; Step 2: Fine grinding and polishing: Polish the rough-ground sample and add polishing agent to obtain a clean, smooth, scratch-free polished surface; Step 3: Etching of samples: Mix hydrochloric acid, nitric acid and glycerin, put them into container No. 1 and mix them evenly for later use; Mix 3% bromine water and methanol, put into container No. 2, and set aside; Next, put the polished sample into container No. 1 and immerse the sample completely in the mixed solution in container No. 1; after etching, wipe the sample for one minute with absorbent cotton dipped in the mixed solution in container No. 2 without rinsing, then rinse the sample surface with clean water, and finally rinse the sample with alcohol and blow dry; Step 4: Metallographic observation and analysis.

2. The metallographic corrosion test method for analyzing the morphology of carbides of nuclear power nickel-based alloys according to claim 1, characterized in that: The volume ratio of the hydrochloric acid, nitric acid, glycerol, 3% bromine water and methanol is 9:3:1:1-1.5:

10.

3. The metallographic corrosion test method for analyzing the morphology of carbides of nuclear power nickel-based alloys according to claim 1, characterized in that: The hydrochloric acid and nitric acid are analytically pure reagents.

4. The metallographic corrosion test method for analyzing the morphology of carbides of nuclear power nickel-based alloys according to claim 1, characterized in that: The polished sample is immersed in container No. 1 for 20-30 seconds.

5. The metallographic corrosion test method for analyzing the morphology of carbides of nuclear nickel-based alloys according to claim 1, characterized in that: The polishing agent is a 0.5 μm diamond polishing agent.

6. The metallographic corrosion test method for analyzing the morphology of carbides of nuclear nickel-based alloys according to any one of claims 1 to 5, characterized in that: The rough grinding step is: using sandpaper of different grits to grind the sample step by step, from coarse sandpaper to fine sandpaper, to remove scratches and unevenness on the surface of the sample.

7. The metallographic corrosion test method for analyzing the morphology of carbides of nuclear nickel-based alloys according to claim 6, characterized in that: The rough grinding step is: the sample is ground with 120#, 600#, 1000#, and 1200# sandpaper in sequence. Each time a layer of sandpaper is changed, the sample needs to be rotated 90 degrees along the grinding surface so that the new grinding marks are perpendicular to the previous grinding marks and cover them.

8. A metallographic etching agent for nickel-based alloys, characterized in that: The invention comprises a first reagent and a second reagent, wherein the first reagent is composed of hydrochloric acid, nitric acid and glycerol, and the second reagent is composed of 3% bromine water and methanol, and the volume ratio of the hydrochloric acid, nitric acid, glycerol, bromine water and methanol is 9:3:1:1-1.5:

10.

9. The metallographic etching agent for nickel-based alloy according to claim 8, characterized in that: The hydrochloric acid and nitric acid are analytically pure reagents.

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