Molten salt corrosion resistant nickel-based alloy and preparation method and application thereof

Abstract

The invention provides a molten salt corrosion resistant nickel-based alloy and a preparation method and application thereof, and belongs to the technical field of nickel alloys. The nickel-based alloy disclosed by the invention comprises the following chemical components in percentage by mass: 10 to 20 percent of Mo, 10 to 20 percent of W, 6 to 10 percent of Cr, 0.1 to 0.5 percent of Si, 0 to 0.6 percent of Mn, 0.03 to 0.06 percent of C, 0 to 0.1 percent of Zr, 0 to 0.06 percent of Fe, 0 to 0.5 percent of Ti and the balance of Ni. And the total amount of Mo and W is not less than 22%. In the nickel-based alloy, Mo and W need to be added at the same time, and the high-temperature mechanical property of the alloy can be improved by reducing the stacking fault of the alloy. Meanwhile, the total amount of Mo and W is controlled to be larger than or equal to 22, the Mo / W ratio is larger than 0.5, continuous Mo-rich M6C carbide can be formed on the grain boundary in the high-temperature aging process of the nickel-based alloy, and the effect of preventing Cr from corroding along the grain is achieved. The nickel-based alloy disclosed by the invention not only has excellent molten salt corrosion resistance, but also has better high-temperature mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of corrosion-resistant alloy materials technology, specifically to a nickel-based alloy resistant to molten salt corrosion, its preparation method and application, and more specifically to a nickel-based alloy resistant to chloride and fluoride molten salt corrosion, its preparation method and application. Background Technology

[0002] Halogenated molten salts, such as those containing chlorides and fluorides, possess advantages such as high melting points, high specific heat capacities, good thermal stability, and excellent heat transfer performance, making them candidate heat transfer and storage media for high-temperature applications such as molten salt reactors, concentrated solar power (CSP) generation, and nuclear fuel reprocessing. Studies have shown that increasing the outlet temperature of molten salt reactors and CSP power plants to above 600℃ can significantly reduce their costs, promoting their commercialization and application. However, the strong corrosiveness of high-temperature chloride and fluoride molten salts to metallic structural materials poses a significant challenge to the long-term service safety of structural alloy materials, necessitating an urgent solution to the corrosion problem of structural alloys in 600-800℃ halide molten salts.

[0003] Studies have found that adding titanium dioxide (W) to nickel-based alloys can improve their high-temperature mechanical properties. For example, Chinese patent application number 201510612608.4 discloses a Ni-(26-28)W-6Cr alloy, whose high-temperature mechanical properties are significantly higher than those of UNS N10003. However, previous studies have found that W is easily corroded in chloride salts, therefore, Ni-(26-28)W-6Cr alloys with excessively high W content do not have ideal resistance to chloride salt corrosion. Chinese patent number CN 112322939 A discloses a nickel-based alloy containing Mo, W, and Nb simultaneously. This alloy improves its radiation resistance and mechanical properties by controlling Mo+W ≤ 22% to precipitate fine MC carbides in the alloy microstructure; however, it does not consider the alloy's resistance to molten salt corrosion. Summary of the Invention

[0004] The technical problem to be solved by this invention is to overcome the limitation of existing nickel-based alloys in achieving both molten salt corrosion resistance and high-temperature mechanical properties. This invention provides a molten salt corrosion resistant nickel-based alloy, its preparation method, and its applications. The nickel-based alloy of this invention not only exhibits excellent molten salt corrosion resistance but also possesses good high-temperature mechanical properties.

[0005] This invention provides a nickel-based alloy resistant to molten salt corrosion, whose chemical composition by mass percentage is: 10-20% Mo, 10-20% W, 6-10% Cr, 0.1-0.5% Si, 0-0.6% Mn, 0.03-0.06% C, 0-0.1% Zr, 0-0.06% Fe, 0-0.5% Ti, with the balance being Ni; and the total amount of Mo and W is ≥22%.

[0006] In the nickel-based alloy of the present invention, Mo and W need to be added to the nickel-based alloy simultaneously. The alloy containing both Mo and W has a lower stacking fault energy than nickel-based alloys containing only Mo or only W. By reducing the stacking fault energy, the high-temperature mechanical properties of the alloy are improved. Furthermore, by controlling the amount of Mo and W, after high-temperature treatment, a continuous secondary precipitate phase M6C carbide appears at the grain boundaries. This intergranular secondary precipitate phase can prevent Cr in the alloy matrix from diffusing outward along the grain boundaries, thus inhibiting intergranular corrosion of the alloy.

[0007] In this invention, preferably, the nickel-based alloy has the following chemical composition by mass percentage: 10-16% Mo, 10-19% W, 6-10% Cr, 0.2-0.4% Si, 0.3-0.6% Mn, 0.03-0.06% C, 0-0.04% Zr, 0-0.06% Fe, 0.1-0.3% Ti, with the balance being Ni.

[0008] In a specific embodiment of the present invention, the nickel-based alloy has the following chemical composition by mass percentage: 10.02-15.1% Mo, 10.03%-18.03% W, 6.12-9.5% Cr, 0.23-0.31% Si, 0.3-0.54% Mn, 0.035-0.05% C, 0.018-0.035% Zr, 0.01-0.06% Fe, 0.22-0.24% Ti, with the balance being Ni.

[0009] In this invention, preferably, the Mo accounts for 10-16% of the mass percentage of the nickel-based alloy, more preferably 10.02%-15.1%, for example 10.02%, 10.05%, 11%, 13.04%, 13.12% and 15.1%.

[0010] In this invention, preferably, the W accounts for 10-19% of the mass percentage of the nickel-based alloy, more preferably 10.03%-18.03%, for example 10.03%; 11.02%, 13.08%, 13.18%, 15.05% and 18.03%.

[0011] In this invention, preferably, the C content in the nickel-based alloy is 0.03-0.06% by mass, more preferably 0.035%-0.05%, for example 0.035%, 0.045%, and 0.05%.

[0012] In this invention, preferably, the sum of the mass percentages of Mo and W in the nickel-based alloy is 22-29%, more preferably 22.02-28.08%, for example 22.02%, 25.07%, 25.13%, 26.20%, 26.22%, and 28.08%. When the sum of the mass percentages of Mo and W is within the above range, it is possible to balance the improvement of the alloy's high-temperature mechanical properties with the maintenance of its overall performance, while also having controllable cost and smelting process.

[0013] In this invention, preferably, the mass ratio of Mo to W in the nickel-based alloy is 0.5-1.5, for example, 0.56, 0.66, 0.99, 1, and 1.5. This ensures that Mo-rich M6C carbides easily form at grain boundaries during high-temperature aging of the alloy.

[0014] In this invention, preferably, the Cr accounts for 6-10% of the mass percentage of the nickel-based alloy, more preferably 6.12-9.5%, for example 6.12%, 6.3% and 9.5%.

[0015] In this invention, preferably, the Si accounts for 0.2-0.4% of the mass percentage of the nickel-based alloy, more preferably 0.23-0.31%, for example 0.23%, 0.24% and 0.31%.

[0016] In this invention, preferably, the Mn accounts for 0.3-0.6% of the mass percentage of the nickel-based alloy, more preferably 0.3-0.54%, for example 0.3%, 0.5% and 0.54%.

[0017] In this invention, preferably, the Zr accounts for 0-0.04% of the mass percentage of the nickel-based alloy, more preferably 0.018-0.035%, for example 0.018%, 0.031%, 0.034% and 0.035%.

[0018] In this invention, preferably, the Fe accounts for 0-0.06% of the mass percentage of the nickel-based alloy, more preferably 0.01-0.06%, for example 0.01%, 0.05% and 0.06%.

[0019] In this invention, preferably, the Ti accounts for 0.1-0.3% of the mass percentage of the nickel-based alloy, more preferably 0.22-0.24%, for example 0.22%, 0.23% and 0.24%.

[0020] In this invention, the nickel-based alloy contains an austenitic phase γ and a precipitated phase, wherein the precipitated phase is M6C.

[0021] In this invention, preferably, the precipitated phase includes a primary precipitated phase and a secondary precipitated phase distributed along the grain boundaries of the alloy.

[0022] The secondary precipitates distributed along the grain boundaries of the alloy can prevent Cr in the alloy matrix from diffusing outward along the grain boundaries, thus inhibiting intergranular corrosion of the alloy.

[0023] This invention also provides a method for preparing a nickel-based alloy, comprising the following steps:

[0024] The master alloy is selected based on the chemical composition of the above-mentioned nickel-based alloy, and the nickel-based alloy is obtained by casting.

[0025] The aforementioned "master alloy" refers to the conventional alloy material used for casting that has been refined to a precise composition in the field of alloy preparation. It can be selected according to the type and content of the required chemical elements before casting.

[0026] In a specific embodiment of the present invention, the method for preparing the nickel-based alloy includes the following steps:

[0027] S1. The master alloy is cast using a vacuum induction furnace;

[0028] S2, homogenization treatment;

[0029] S3, Hot working.

[0030] Preferably, in step S2, the homogenization treatment temperature is 1200~1220℃, for example 1220℃.

[0031] Preferably, in step S2, the homogenization process takes 2 to 4 hours, for example 3 hours (the furnace is loaded at a temperature below 600°C, and timing begins after the temperature is reached), followed by air cooling after removal from the furnace.

[0032] Preferably, in step S3, the temperature of the heat treatment is 1150~1200℃, for example 1200℃.

[0033] Preferably, in step S3, the hot working is forging or hot rolling.

[0034] The present invention also provides an application of the nickel-based alloy described above in a molten salt environment.

[0035] In a specific embodiment of the present invention, the nickel-based alloy is used as a metallic structural material.

[0036] In a specific embodiment of the present invention, the temperature of the molten salt environment is not lower than 600°C, for example, not lower than 800°C.

[0037] In a specific embodiment of the present invention, the molten salt includes chloride molten salt and / or fluoride molten salt.

[0038] The chloride molten salt is selected from one or more of LiCl, NaCl, KCl, MgCl2, CaCl2, ZnCl2 and AlCl3; for example, it is selected from one or more of NaCl-KCl-MgCl2, NaCl-KCl-CaCl2, NaCl-KCl-ZnCl2, KCl-MgCl2 and NaCl-MgCl2.

[0039] The fluoride molten salt is selected from one or more of LiF, NaF, KF, BeF2, ZrF4, UF4, ThF4 and NaBF4; for example, it is selected from one or more of LiF-NaF-KF, LiF-BeF2, LiF-NaF, NaF-BeF2, NaF-ZrF4, KF-ZrF4, LiF-BeF2-UF4 and LiF-BeF2-UF4-ThF4.

[0040] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0041] The reagents and raw materials used in this invention are all commercially available.

[0042] The positive and progressive effects of this invention are as follows:

[0043] The nickel-based alloy of this invention, resistant to molten salt corrosion, employs a specific Mo, W, and Cr ratio, ensuring Mo + W ≥ 22% and Cr ≤ 10%, along with an appropriate amount of C. This allows the resulting nickel-based alloy to precipitate Mo-rich M6C carbides at grain boundaries during high-temperature aging. Furthermore, the coexistence of Mo and W reduces the alloy's stacking fault energy; the higher the Mo / W ratio, the lower the stacking fault energy, which is beneficial for improving mechanical properties. Therefore, the nickel-based alloy of this invention not only exhibits excellent resistance to molten salt corrosion but also possesses good high-temperature mechanical properties. Attached Figure Description

[0044] Figure 1 The image shows the cross-sectional scanning electron microscope (SEM) morphology of the nickel-based alloy obtained in Example 1 after corrosion in NaCl-KCl-MgCl2 molten salt at 800℃ for 100 h.

[0045] Figure 2 The image shows the cross-sectional scanning electron microscope (SEM) morphology of the nickel-based alloy obtained in Example 2 after corrosion in NaCl-KCl-MgCl2 molten salt at 800℃ for 100 h.

[0046] Figure 3 The image shows the cross-sectional scanning electron microscope (SEM) morphology of the nickel-based alloy obtained in Example 3 after corrosion in NaCl-KCl-MgCl2 molten salt at 800℃ for 100 h.

[0047] Figure 4 The image shows the cross-sectional scanning electron microscope (SEM) morphology of the nickel-based alloy obtained in Example 4 after corrosion in NaCl-KCl-MgCl2 molten salt at 800℃ for 100 h.

[0048] Figure 5 The image shows the cross-sectional scanning electron microscope (SEM) morphology of the nickel-based alloy obtained in Example 5 after corrosion in NaCl-KCl-MgCl2 molten salt at 800℃ for 100 h.

[0049] Figure 6 The image shows the cross-sectional scanning electron microscope (SEM) morphology of the nickel-based alloy obtained in Example 6 after corrosion in NaCl-KCl-MgCl2 molten salt at 800℃ for 100 h.

[0050] Figure 7 The image shows the cross-sectional scanning electron microscope (SEM) morphology of the nickel-based alloy obtained in Comparative Example 1 after corrosion in NaCl-KCl-MgCl2 molten salt at 800℃ for 100 h.

[0051] Figure 8 The image shows the cross-sectional scanning electron microscope (SEM) morphology of the nickel-based alloy obtained in Comparative Example 2 after corrosion in NaCl-KCl-MgCl2 molten salt at 800℃ for 100 h.

[0052] Figure 9 The image shows the cross-sectional scanning electron microscope (SEM) morphology of the nickel-based alloy obtained in Example 1 after corrosion in LiF-NaF-KF (FLiNaK) molten salt at 800℃ for 400 h.

[0053] Figure 10 The image shows the cross-sectional scanning electron microscope (SEM) morphology of the nickel-based alloy obtained in Comparative Example 1 after corrosion in LiF-NaF-KF (FLiNaK) molten salt at 800℃ for 400 h.

[0054] Figure 11 The image shows the cross-sectional scanning electron microscope (SEM) morphology of the nickel-based alloy obtained in Comparative Example 2 after corrosion in LiF-NaF-KF (FLiNaK) molten salt at 800℃ for 400 h.

[0055] Figure 12 The original microstructure of the nickel-based alloy obtained in Example 1;

[0056] Figure 13 The original microstructure of the nickel-based alloy obtained in Comparative Example 1;

[0057] Figure 14 The original microstructure of the nickel-based alloy obtained in Comparative Example 2;

[0058] Figure 15The microstructure of the nickel-based alloy obtained in Example 1 after aging at 800°C for 100 hours is shown.

[0059] Figure 16 The microstructure of the nickel-based alloy obtained in Comparative Example 1 after aging at 800℃ for 100h is shown.

[0060] Figure 17 The microstructure of the nickel-based alloy obtained in Comparative Example 2 after aging at 800℃ for 100h is shown. Detailed Implementation

[0061] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0062] Examples 1-6

[0063] The methods for preparing nickel-based alloys provided in Examples 1-6 are as follows:

[0064] S1. The master alloy is cast using a vacuum induction furnace; specifically:

[0065] The high-purity (purity > 99.9%) master alloy containing Ni, Mo, W, Cr, Si, Mn, C, Zr, Ti and Fe is mixed according to the chemical composition ratio of the final nickel-based alloy in Table 1 and melted into ingots in a vacuum induction furnace.

[0066] S2. Homogenization treatment; The homogenization treatment temperature is 1220℃, and the homogenization treatment time is 3 hours.

[0067] S3. Hot working; The hot working method is forging and subsequent high-temperature rolling of thick slabs, and the hot working temperature is 1200℃.

[0068] Comparative Example 1

[0069] Comparative Example 1 provides a nickel-based alloy, the preparation method of which is similar to that of Examples 1-6, except that the proportions of the chemical components in the master alloy in step S1 are different, as shown in Table 1. All other operations and conditions are the same as in Examples 1 to 6.

[0070] The chemical composition of the nickel-based alloy in Comparative Example 1 was designed according to the conventional nickel-molybdenum-chromium-based high-temperature corrosion-resistant alloy UNS N10003.

[0071] Comparative Example 2

[0072] Comparative Example 2 provides a nickel-based alloy, the preparation method of which is similar to that of Examples 1-6, except that the proportions of the chemical components in the master alloy in step S1 are different, as shown in Table 1. All other operations and conditions are the same as in Examples 1-6.

[0073] Effect Experiment Example

[0074] This experiment tests the effects and performance of nickel-based alloys prepared according to the composition of Examples 1-6 and Comparative Examples 1-2 as shown in Table 1 below.

[0075] Table 1. Chemical composition (wt.%) of nickel-based alloys obtained in the examples and comparative examples

[0076]

[0077] I. Methods

[0078] 1. Resistance to molten salt corrosion

[0079] (1) Sample pretreatment method

[0080] The solid solution nickel-based alloy samples obtained in Examples 1-6 and Comparative Examples 1-2 were cut into samples with dimensions of 10 mm × 15 mm × 2.5 mm using wire cutting. A hole with a diameter of 2 mm was drilled in each sample. The surfaces of all samples were polished with SiC sandpaper up to 2000#, then ultrasonically cleaned with deionized water and anhydrous ethanol in sequence, and dried with a hair dryer in cool air for later use.

[0081] (2) Chloride corrosion test method

[0082] The chloride corrosion experiment used a ternary NaCl-KCl-MgCl2 (33-21.6-45.4 mol%) eutectic salt. The molten salt raw materials were analytical grade NaCl, KCl, and MgCl2 (purity greater than 99.5 wt%) produced by Sinopharm Chemical Reagent Co., Ltd. Before the experiment, the chloride salts were weighed and mixed according to the above ratio in a glove box under an inert atmosphere (water and oxygen content less than 1 ppm), with each portion of chloride salt having a total mass of 60 g. The mixed chloride salts were then stored in sealed bags for later use.

[0083] The chloride corrosion experiment employed a double-layer crucible structure, with an inner Al2O3 ceramic crucible and an outer 316 stainless steel crucible. Pretreated samples were loaded into the Al2O3 ceramic crucible, with three parallel samples per experiment. 60g of a NaCl-KCl-MgCl2 (33-21.6-45.4 mol%) solid salt was then added to the Al2O3 ceramic crucible, and the Al2O3 ceramic crucible lid was placed on top. The Al2O3 ceramic crucible containing the samples and molten salt was then placed inside the outer 316 stainless steel crucible, and the stainless steel crucible was welded and sealed. To prevent impurities such as oxygen and moisture from the air from contaminating the molten salt, the entire assembly and welding process of the reactor was carried out in a glove box under an argon atmosphere. The sealed crucible was placed in a high-temperature furnace and held at 800℃ for 100 hours. After the experiment, the crucible was removed, allowed to cool naturally to room temperature, cut, and the samples were removed and cleaned.

[0084] The corrosion weight loss and cross-sectional scanning electron microscope (SEM) morphology of the nickel-based alloys obtained in Examples 1-6 and Comparative Examples 1-2 after corrosion in NaCl-KCl-MgCl2 molten salt at 800℃ for 100 h were measured respectively. The SEM analysis method was performed in accordance with the industry standard JY / T 0584-2020 "General Rules for Analysis Methods of Scanning Electron Microscopy".

[0085] (3) Fluoride salt corrosion test method

[0086] The fluoride salt corrosion experiment used a ternary LiF-NaF-KF (46.5-11.5-42 mol%, FLiNaK) eutectic salt. The molten salt raw materials were analytical grade LiF, NaF, and KF (purity greater than 99.5 wt%) produced by Sinopharm Chemical Reagent Co., Ltd. Before the experiment, the fluoride salts were weighed and mixed according to the above ratio in a glove box under an inert atmosphere (water and oxygen content less than 1 ppm), with each portion of fluoride salt having a total mass of 100 g. The mixed fluoride salts were then stored in sealed bags for later use.

[0087] The fluoride corrosion test apparatus employs a double-layer crucible structure, with an inner graphite crucible and an outer 316 stainless steel crucible. Pretreated samples are loaded into the graphite crucible, with three parallel samples per experiment. 100g of solid FLiNaK salt is then added to the graphite crucible, which is covered with a graphite lid. The graphite crucible is then placed inside the outer 316 stainless steel crucible, and the stainless steel crucible is welded and sealed. To prevent impurities such as oxygen and moisture from the air from contaminating the molten salt, the entire assembly and welding process of the reactor is carried out in a glove box under an argon atmosphere. The sealed crucible is placed in a high-temperature furnace and held at 800℃ for 400 hours. After the experiment, the crucible is removed, allowed to cool naturally to room temperature, cut, and the samples are removed and cleaned.

[0088] The corrosion weight loss and cross-sectional scanning electron microscope (SEM) morphology of the nickel-based alloys obtained in Example 1, Comparative Example 1, and Comparative Example 2 after corrosion in LiF-NaF-KF (FliNaK) molten salt at 800℃ for 400 h were measured respectively. The SEM analysis method was performed in accordance with the industry standard JY / T 0584-2020 "General Rules for Analysis Methods of Scanning Electron Microscopy".

[0089] (4) Microscopic analysis

[0090] Alloys from Example 1, Comparative Example 1, and Comparative Example 2 were subjected to aging treatment at 800℃ in air for 100 hours, and metallographic samples were prepared accordingly. The method was as follows: First, the original and aged states of alloys from Example 1, Comparative Example 1, and Comparative Example 2 were ground and polished. Then, they were etched with 4g copper sulfate, 20mL hydrochloric acid, and 20mL alcohol for 20-30 seconds. The samples were then washed with tap water and dried with a hair dryer. The microstructure of each alloy sample was analyzed using scanning electron microscopy (SEM). The SEM analysis method followed the industry standard JY / T 0584-2020 "General Rules for Analysis Methods of Scanning Electron Microscopy".

[0091] II. Results

[0092] Table 2 shows the corrosion weight loss results of the alloys of Examples 1-6 and Comparative Examples 1-2 after corrosion in NaCl-KCl-MgCl2 molten salt at 800℃ for 100 h. The results show that both the alloys of Examples 1-6 and Comparative Example 1 alloy experienced corrosion weight gain, indicating that neither alloys of Examples 1-6 nor Comparative Example 1 alloy underwent severe corrosion. The alloy of Comparative Example 2 alloy experienced corrosion weight loss, indicating that the alloy of Comparative Example 2 alloy underwent corrosion.

[0093] Table 2. Weight changes of the alloys in the examples and comparative examples after 100 h of chloride corrosion at 800 °C.

[0094]

[0095] Figures 1 to 8 The images show the cross-sectional scanning electron microscope (SEM) morphology of the nickel-based alloys obtained in Examples 1-6 and Comparative Examples 1-2 after corrosion in NaCl-KCl-MgCl2 molten salt at 800℃ for 100 h. It can be seen that the alloys obtained in Examples 1-6 only exhibit weak corrosion in localized areas, with a maximum corrosion depth not exceeding 20 μm. The alloy in Comparative Example 1 showed only weak corrosion in localized areas, with a corrosion depth of approximately 12 μm. The alloy in Comparative Example 2 showed obvious dealloying corrosion pits below the surface, with a corrosion depth of approximately 44.3 μm. These results indicate that the corrosion resistance of the alloys in Examples 1-6 in molten chloride salt at 800℃ is comparable to that of the alloy in Comparative Example 1, and superior to that of the alloy in Comparative Example 2.

[0096] Table 3 shows the corrosion weight loss results of the nickel-based alloys obtained in Example 1, Comparative Example 1, and Comparative Example 2 after corrosion in LiF-NaF-KF (FliNaK) molten salt at 800℃ for 400 h. It was found that the corrosion weight loss of the alloys in Example 1 and Comparative Example 1 in 800℃ FLiNaK molten salt was similar, and both were significantly lower than that of the alloy in Comparative Example 2, indicating that the corrosion resistance of the alloys in Example 1 and Comparative Example 1 is similar, but superior to that of the alloy in Comparative Example 2.

[0097] Table 3. Weight changes of various nickel-based alloys after 400 h of corrosion in FLiNaK molten salt.

[0098]

[0099] Figures 9 to 11 The images show the cross-sectional scanning electron microscope (SEM) morphology of the nickel-based alloys obtained in Example 1 and Comparative Examples 1-2 after corrosion at 800°C for 400 h in LiF-NaF-KF (FliNaK) molten salt. The results show that the alloys of Example 1, Comparative Examples 1, and Comparative Examples 2 all exhibited significant dealloying corrosion, forming corrosion pits in the matrix below the alloy surface. The maximum corrosion depth of the alloy in Example 1 was 170 μm. Figure 9 The maximum corrosion depth of alloy 1 in Comparative Example 1 was 200 μm. Figure 10 The maximum corrosion depth of alloy 2 in comparison example 2 was 230 μm. Figure 11 Based on the combined results of corrosion weight loss and cross-sectional corrosion depth measurements, the corrosion resistance of alloys in Example 1 and Comparative Example 1 in 800℃ FliNaK molten salt is similar, but significantly better than that of Comparative Example 2 alloy.

[0100] Table 4 summarizes the comparison results of corrosion depth of alloys in Examples 1-6 and Comparative Examples 1-2 under different experimental environments. It can be seen that the nickel-based alloys obtained in Examples 1 to 6 of the present invention have good resistance to molten salt corrosion, which is comparable to that of alloy in Comparative Example 1 and superior to that of alloy in Comparative Example 2.

[0101] Table 4. Corrosion depth of nickel-based alloys obtained in the examples and comparative examples in molten halide salts at 800°C

[0102]

[0103] 3. High-temperature mechanical properties

[0104] Using JMatPro 7.0 material calculation software, the high-temperature strength of the nickel-based alloys obtained in Examples 1 to 6 and Comparative Examples 1-2 was calculated. The grain size was set to 10 micrometers, the strain rate to 0.001 / s, and the temperature to 800℃. The calculated mechanical properties are shown in Table 5.

[0105] Table 5. Calculation results of tensile properties of the alloys obtained in the examples and comparative examples at 800℃.

[0106]

[0107] As can be seen, compared with the nickel-based alloy of Comparative Example 1, the nickel-based alloys obtained in Examples 1 to 6 showed significantly increased yield strength and tensile strength at 800°C. Compared with the alloy of Comparative Example 2, the nickel-based alloys obtained in Examples 1 to 6 did not show decreased yield strength and tensile strength at 800°C.

[0108] In summary, the nickel-based alloy of this invention exhibits excellent resistance to molten salt corrosion and also possesses good high-temperature mechanical properties, making it an alloy material with good overall performance.

[0109] 4. Microstructure

[0110] Figures 12 to 17 The microstructures of the alloys in Example 1, Comparative Example 1, and Comparative Example 2 are shown in their original state and aged state at 800℃. The original state surfaces of all three alloys exhibit obvious primary precipitates. After aging at 800℃ for 100 hours, continuous secondary precipitates of M6C carbides (…) appear at the grain boundaries of the alloys in Example 1 and Comparative Example 1. Figure 15 and Figure 16 This has the effect of inhibiting the outward diffusion of Cr along the grain boundaries. However, the alloy in Comparative Example 2 does not have a continuous distribution of secondary precipitates M6C carbides at the grain boundaries. Figure 17 Therefore, Cr in the alloy matrix easily diffuses outward along the grain boundaries, resulting in severe intergranular corrosion.

Claims

1. A nickel-based alloy resistant to molten salt corrosion, characterized in that, Its chemical composition, by mass percentage, is: 10-20% Mo, 10-20% W, 6-10% Cr, 0.1-0.5% Si, 0-0.6% Mn, 0.03-0.06% C, 0-0.1% Zr, 0-0.06% Fe, 0-0.5% Ti, with the balance being Ni; and the total amount of Mo and W is ≥22%.

2. The nickel-based alloy as described in claim 1, characterized in that, It satisfies one or more of the following conditions: (1) The nickel-based alloy, by mass percentage, has the following chemical composition: 10-16% Mo, 10-19% W, 6-10% Cr, 0.2-0.4% Si, 0.3-0.6% Mn, 0.03-0.06% C, 0-0.04% Zr, 0-0.06% Fe, 0.1-0.3% Ti, with the balance being Ni; preferably, the nickel-based alloy has the following chemical composition: 10.02-15.1% Mo, 10.03%-18.03% W, 6.12-9.5% Cr, 0.23-0.31% Si, 0.3-0.54% Mn, 0.035-0.05% C, 0.018-0.035% Zr. 0.01-0.06% Fe, 0.22-0.24% Ti, balance Ni; (2) The Mo content in the nickel-based alloy is 10-16% by mass, preferably 10.02%-15.1%, for example 10.02%, 10.05%, 11%, 13.04%, 13.12% and 15.1%; (3) The W content in the nickel-based alloy is 10-19% by mass, preferably 10.03%-18.03%, for example 10.03%; 11.02%, 13.08%, 13.18%, 15.05% and 18.03%; (4) The mass percentage of C in the nickel-based alloy is 0.03-0.06%, preferably 0.035%-0.05%, for example 0.035%; 0.045% and 0.05%.

3. The nickel-based alloy as described in claim 1, characterized in that, It satisfies one or more of the following conditions: (1) The sum of the mass percentages of Mo and W in the nickel-based alloy is 22-29%, preferably 22.02-28.08%, for example 22.02%, 25.07%, 25.13%, 26.20%, 26.22% and 28.08%; (2) In the nickel-based alloy, the mass ratio of Mo to W is 0.5-1.5, for example, 0.56, 0.66, 0.99, 1 and 1.

5.

4. The nickel-based alloy as described in claim 1, characterized in that, It satisfies one or more of the following conditions: (1) The Cr accounts for 6-10% of the mass of the nickel-based alloy, preferably 6.12-9.5%, for example 6.12%, 6.3% and 9.5%; (2) The Si accounts for 0.2-0.4% of the mass of the nickel-based alloy, preferably 0.23-0.31%, for example 0.23%, 0.24% and 0.31%; (3) The mass percentage of Mn in the nickel-based alloy is 0.3-0.6%, preferably 0.3-0.54%, for example 0.3%, 0.5% and 0.54%; (4) The Zr accounts for 0-0.04% of the mass of the nickel-based alloy, preferably 0.018-0.035%, for example 0.018%, 0.031%, 0.034% and 0.035%; (5) The Fe content in the nickel-based alloy is 0-0.06% by mass, preferably 0.01-0.06%, for example 0.01%, 0.05% and 0.06%; (6) The Ti accounts for 0.1-0.3% of the mass of the nickel-based alloy, preferably 0.22-0.24%, for example 0.22%, 0.23% and 0.24%.

5. The nickel-based alloy as described in claim 1, characterized in that, The nickel-based alloy contains an austenitic phase γ and a precipitated phase, wherein the precipitated phase is M6C; preferably, the precipitated phase includes a primary precipitated phase and a secondary precipitated phase distributed along the alloy grain boundaries.

6. A method for preparing a nickel-based alloy, characterized in that, It includes the following steps: selecting a master alloy based on the chemical composition of the nickel-based alloy according to any one of claims 1-5, and casting the nickel-based alloy.

7. The method for preparing the nickel-based alloy as described in claim 6, characterized in that, The preparation method of the nickel-based alloy includes the following steps: S1. The master alloy is cast using a vacuum induction furnace; S2, homogenization treatment; S3, Hot working.

8. The method for preparing the nickel-based alloy as described in claim 7, characterized in that, It satisfies one or more of the following conditions: (1) In step S2, the temperature of the homogenization process is 1200~1220℃, for example 1220℃; (2) In step S2, the homogenization process takes 2 to 4 hours, for example, 3 hours; (3) In step S3, the temperature of the heat treatment is 1150~1200℃, for example 1200℃; (4) In step S3, the hot working is forging or hot rolling.

9. The use of a nickel-based alloy according to any one of claims 1-5 in a molten salt environment.

10. The application as described in claim 9, characterized in that, It satisfies one or more of the following conditions: (1) The nickel-based alloy is used as a metallic structural material; (2) The temperature of the molten salt environment is not lower than 600℃, for example, not lower than 800℃; (3) The molten salt includes chloride molten salt and / or fluoride molten salt; The chloride molten salt is selected from one or more of LiCl, NaCl, KCl, MgCl2, CaCl2, ZnCl2 and AlCl3; for example, it is selected from one or more of NaCl-KCl-MgCl2, NaCl-KCl-CaCl2, NaCl-KCl-ZnCl2, KCl-MgCl2, and NaCl-MgCl2. The fluoride molten salt is selected from one or more of LiF, NaF, KF, BeF2, ZrF4, UF4, ThF4 and NaBF4; for example, it is selected from one or more of LiF-NaF-KF, LiF-BeF2, LiF-NaF, NaF-BeF2, NaF-ZrF4, KF-ZrF4, LiF-BeF2-UF4 and LiF-BeF2-UF4-ThF4.

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