Radiation resistant nickel-base alloy

Abstract

The application discloses a kind of radiation-resistant nickel-based alloys, the nanometer scale gamma prime precipitated phase is uniformly distributed in the grain of the nickel-based alloy, the main constituent element of gamma prime phase is Ni, Ti and Al, gamma prime phase presents L12 ordered superlattice structure, and same as matrix gamma is face-centered cubic structure.The composition of alloy element composition is as follows in atomic percentage (at.%) :Ni:38-58%, Co:15-30%, Cr:10-20%, Ti:3-9%, Al:1-8%, Mo:1-4%, W:0.5-3%, Fe:0.5-2%, Zr:0.02-0.05%, C:0.05-0.2%, B:0.05-0.2%.The present application obtains nanometer scale gamma prime precipitated phase strengthened nickel-based alloy by solid solution plus aging heat treatment.The alloy does not appear obvious He bubble after irradiation, and there is no obvious gamma prime precipitated phase dissolution phenomenon in the alloy, and only the structure of gamma prime precipitated phase is disordered after irradiation.

Description

Technical Field

[0001] This invention relates to the field of nuclear power materials, and more specifically, to a radiation-resistant nickel-based alloy. Background Technology

[0002] Nuclear energy occupies an extremely important position in the current energy sector. The efficiency and safety of nuclear reactors largely depend on the performance of the structural materials used in their components under extreme conditions such as high temperatures and intense radiation. Nickel-based alloys are widely used in the nuclear industry due to their high strength, good thermal stability at high temperatures, corrosion resistance, and radiation resistance.

[0003] Structural materials used in nuclear reactors are subjected to long-term exposure to high temperatures and high doses of high-energy particle radiation. This alters the internal structure of the alloys, leading to a decline in material properties and a shortened service life. Alloys used in the nuclear industry for extended periods develop various defects after irradiation, including voids, stacking fault tetrahedrons, and dislocation loops. These defects alter the macroscopic properties of the material, causing problems such as swelling and embrittlement.

[0004] The literature (Porollo SI, Dvoriashin AM, Konobeev YV, et al. Microstructure and swelling of neutron irradiated nickel and binary nickel alloys[J]. Journal of Nuclear Materials, 2013, 442(1-3):S809-S812.) describes neutron irradiation of pure nickel and three binary nickel-based alloys with different solutes, with the temperature controlled in the range of 673–823 K. After neutron irradiation, obvious voids appeared in both the pure nickel and binary nickel-based alloy samples, and the materials underwent irradiation swelling. The materials are prone to grain boundary cracking and density reduction, which affects the service performance of the alloys and makes them more susceptible to failure.

[0005] The literature (Fabritsiev SA, Pokrovsky A S. Effect of irradiation temperature on microstructure, radiation hardening and embrittlement of pure copper and copper-based alloy[J]. Journal of Nuclear Materials, 2007, 367-370:977-983.) mentions that irradiation embrittlement is one of the main negative effects of neutron irradiation on copper and copper alloys. Pure copper and copper alloys were irradiated with neutrons at 80 °C and 150 °C, with irradiation doses of 10... -3 dpa, 10 -2 dpa and 10 -1 dpa. After neutron irradiation, the sample developed high-density defect clusters, including stacking fault tetrahedra and dislocation loops. The defect density increased with increasing irradiation dose. The presence of these defect clusters caused significant embrittlement of the material. Increasing the irradiation temperature reduced this embrittlement phenomenon.

[0006] Furthermore, for nickel-based alloys and similar alloys containing precipitates, irradiation can affect the structure, morphology, and distribution of these precipitates. Precipitates with ordered structures may become disordered, and when the irradiation dose increases to a certain level, coarsening and dissolution of the precipitates may even occur. Dissolution of the precipitates negatively impacts the mechanical properties of the alloy.

[0007] The literature (Changizian P, Yao Z, Lu C, et al. Radiation effect on nano-indentation properties and deformation mechanism of a Ni-based superalloy X-750[J]. Journal of Nuclear Materials, 2019, 515:1-13.) describes the Ni-750 nickel-based alloy at 400 ℃ and room temperature. + Ion irradiation. Experimental results showed that after room temperature irradiation, the superlattice representing the ordered structure of the γ′ phase in the aged sample completely disappeared, and the γ′ phase became disordered. In addition, the γ′ phase in the alloy exhibited shape changes, indicating that the γ′ phase partially dissolved.

[0008] To address the above issues, the nuclear field currently needs a nickel-based alloy with good radiation resistance as a reactor structural material. The alloy must be able to maintain structural stability under high-energy particle irradiation to improve reactor safety and service life. Summary of the Invention

[0009] In order to meet the requirements of maintaining stable service performance and extending service life of structural materials in the nuclear industry, the present invention aims to propose a nickel-based alloy containing nanoscale γ′ precipitates, which exhibits good radiation resistance in irradiation environments.

[0010] The technical solution to achieve the purpose of this invention is as follows:

[0011] A radiation-resistant nickel-based alloy has nanoscale γ′ precipitates uniformly distributed within its grains. The main constituent elements of the γ′ phase are Ni, Ti, and Al. The γ′ phase exhibits an L12 ordered superlattice structure and, like the matrix γ, has a face-centered cubic structure.

[0012] Preferably, the elemental composition of the nickel-based alloy, in atomic percentage (at.%), is as follows: Ni: 38-58%, Co: 15-30%, Cr: 10-20%, Ti: 3-9%, Al: 1-8%, Mo: 1-4%, W: 0.5-3%, Fe: 0.5-2%, Zr: 0.02-0.05%, C: 0.05-0.2%, B: 0.05-0.2%.

[0013] A method for preparing the above-mentioned radiation-resistant nickel-based alloy comprises the following steps:

[0014] (1) The metal raw materials are subjected to vacuum induction melting, homogenization treatment and forging treatment in sequence according to the element ratio to obtain a cast-forged nickel-based alloy;

[0015] (2) The nickel-based alloy in step (1) is subjected to solid solution treatment to dissolve the non-uniformly distributed primary precipitates in the alloy to obtain a nickel-based alloy containing nanoscale γ′ precipitates.

[0016] (3) The nickel-based alloy from step (2) is subjected to aging treatment to further regulate the size and distribution of the γ′ precipitate inside the alloy.

[0017] Furthermore, the metal raw materials are smelted in a vacuum induction melting furnace according to the stated element ratio, with the furnace evacuated to a vacuum level of 1×10⁻⁶. -2 Pa is filled with argon gas for protection.

[0018] Furthermore, the homogenization treatment was carried out at a temperature of 1100 ℃ for 48 h.

[0019] Furthermore, the forging temperature is 1050 ℃ and the forging ratio is 4.

[0020] Furthermore, the solution treatment temperature is 1050-1150 ℃, the treatment time is 3-6 h, and the cooling method is air cooling.

[0021] Furthermore, the aging treatment temperature is 650-750 ℃, the treatment time is 1-4 h, and the cooling method is air cooling.

[0022] Furthermore, after aging treatment, the diameter distribution of the γ′ precipitate inside the nickel-based alloy is between 85 and 140 nm, and the volume fraction of the γ′ precipitate is 30-40%.

[0023] Compared with the prior art, the present invention has the following significant advantages:

[0024] (1) The elemental composition of the radiation-resistant nickel-based alloy of the present invention is reasonably and scientifically designed. Among them, Co can improve the stability of the alloy structure; Cr can improve the alloy's oxidation resistance and hot corrosion resistance; Ti can improve the alloy's hot corrosion resistance; Al can effectively inhibit the formation of voids during irradiation; Mo and W are beneficial to improving the mechanical properties and thermal stability of the material.

[0025] (2) The radiation-resistant nickel-based alloy of the present invention can be obtained by a simple and easy heat treatment method to obtain a special structure containing nanoscale γ′ precipitates, thereby improving the overall performance of the alloy and effectively resisting radiation damage.

[0026] (3) The radiation-resistant nickel-based alloy of the present invention is subjected to He 2+ Ion irradiation experiments revealed that no widespread He formation occurred in the alloy. 2+ He bubbles are a common feature in ion irradiation experiments. Inhibiting the formation of He bubbles can effectively prevent materials from swelling after irradiation.

[0027] (4) The radiation-resistant nickel-based alloy of the present invention is subjected to He 2+ Ion irradiation experiments revealed that the γ′ precipitate in the alloy underwent only disordering of its ordered structure after irradiation, without any significant dissolution.

[0028] In summary, the radiation-resistant nickel-based alloy described in this invention has excellent properties, such as no obvious He bubbles appearing after irradiation and the γ′ precipitates in the alloy only undergoing disordering without significant dissolution after irradiation. It can be applied to nuclear reactor structural materials and has broad application prospects.

[0029] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0030] Figure 1 Images showing the microstructure of nickel-based alloys obtained after two heat treatment steps: solution treatment and aging. (a) is a STEM image; (b) is a diffraction image.

[0031] Figure 2 (a) is a TEM image of a nickel-based alloy after room temperature irradiation; (b) is a TEM image of the microstructure of the X-750 nickel-based alloy in Comparative Example 2 after proton irradiation at 380 °C.

[0032] Figure 3 These are diffraction images and energy dispersive spectroscopy (EDS) images of nickel-based alloys after room temperature irradiation. Detailed Implementation

[0033] This invention obtains a nickel-based alloy containing nanoscale γ′ precipitates by rationally controlling the elemental composition and combining it with appropriate heat treatment conditions. This alloy exhibits good radiation resistance in irradiated environments.

[0034] The elemental composition of the nickel-based alloy, expressed as atomic percentage (at.%), is as follows: Ni: 38-58%, Co: 15-30%, Cr: 10-20%, Ti: 3-9%, Al: 1-8%, Mo: 1-4%, W: 0.5-3%, Fe: 0.5-2%, Zr: 0.02-0.05%, C: 0.05-0.2%, B: 0.05-0.2%.

[0035] For various nickel-based alloys, the common main constituent elements include Co, Cr, Ti, Al, Mo, W, etc., and different elements have different roles and functions in the alloy.

[0036] Co and Cr are the main constituent elements of the γ phase matrix of nickel-based alloys. The addition of Co can improve the stability of the microstructure, while Cr can effectively improve the alloy's resistance to oxidation and hot corrosion.

[0037] Ti and Al are the main constituent elements of the γ′ precipitate. The presence of Ti can improve the hot corrosion resistance of nickel-based alloys, while Al helps to form an oxide film, providing better protection for the alloy. Alloying Ni with Ti and Al can effectively reduce or suppress irradiation swelling.

[0038] Mo and W are refractory elements, and their addition to alloys helps improve the material's mechanical properties and thermal stability. Specifically, the addition of Mo can enhance the material's creep resistance.

[0039] The nickel-based alloy of this invention has uniformly distributed nanoscale γ′ precipitates within its grains. The main constituent elements of the γ′ phase are Ni, Ti, and Al, exhibiting an L12 ordered superlattice structure, which, like the matrix γ, has a face-centered cubic structure. Introducing nanoscale precipitates into a single-phase γ-phase nickel-based alloy can effectively improve the overall performance of the alloy. In this invention, the nickel-based alloy exhibits excellent radiation resistance.

[0040] The structure is primarily achieved through heat treatment. First, the cast-forged nickel-based alloy undergoes solution treatment to dissolve the unevenly distributed primary precipitates, resulting in a nickel-based alloy with a uniformly distributed structure reinforced by nanoscale γ′ precipitates. Next, the solution-treated nickel-based alloy undergoes aging treatment to further control the size and distribution of the γ′ precipitates within the alloy.

[0041] Example 1

[0042] By designing a reasonable elemental composition ratio and combining it with a two-step heat treatment process of solution treatment and aging, a nickel-based alloy with nanoscale γ′ precipitates uniformly distributed within the grains was obtained. The alloy's radiation resistance was verified by room temperature irradiation experiments.

[0043] The elemental composition of the nickel-based alloy, expressed in atomic percentages (at.%), is as follows: Ni: 49.10%, Co: 20.87%, Cr: 16.54%, Ti: 4.66%, Al: 5.43%, Mo: 2.15%, W: 0.43%, Fe: 0.61%, Zr: 0.03%, C: 0.13%, B: 0.05%.

[0044] Based on the stated element ratio, the alloy subsequently undergoes vacuum induction melting, homogenization treatment, and forging treatment to obtain a cast-forged nickel-based alloy base material.

[0045] First, the metal raw materials are prepared according to the designed proportions and then smelted in a vacuum induction melting furnace to obtain nickel-based alloy ingots. The furnace is evacuated to a vacuum level of 1×10⁻⁶. -2 Pa was then introduced, followed by argon gas for protection. The ingot was then subjected to a long-term homogenization treatment at 1150 °C for 48 h. Finally, the material was forged at a high temperature of 1050 °C to obtain a cast-forged nickel-based alloy base material with a forging ratio of 4.

[0046] The cast-forged nickel-based alloy base material is then subjected to heat treatment under specific conditions to obtain a nickel-based alloy with radiation resistance. The heat treatment process includes solution treatment and aging treatment.

[0047] The conditions for the solution treatment of the nickel-based alloy are as follows: the solution treatment temperature is 1100 ℃; the solution treatment time is 4 h; and the cooling method is air cooling.

[0048] The conditions for aging treatment of the nickel-based alloy are as follows: aging temperature is 700 ℃; aging time is 2 h; and cooling method is air cooling.

[0049] After aging treatment, the diameter of the γ′ precipitate inside the nickel-based alloy is distributed between 85 and 140 nm, with an average diameter of ~104 nm and a volume fraction of γ′ precipitate of 36.0%.

[0050] Figure 1 The STEM and diffraction images of the microstructure of the nickel-based alloy after both solution and aging heat treatments are shown. Figure 1 In (a), the γ′ precipitate can be observed to be spherical in shape and uniformly dispersed within the γ phase matrix. Figure 1 The diffraction pattern in (b) simultaneously shows diffraction spots representing the γ-phase matrix of the FCC structure and the γ′ precipitate of the L12 ordered structure, which are marked in white and yellow respectively in the figure. The diffraction pattern proves that the γ′ precipitate in the sample before irradiation has an ordered structure.

[0051] The nickel-based alloy was subjected to room temperature irradiation experiments, with the following parameters: the irradiation ion was He. 2+ The irradiation ion energy is 500 keV, and the irradiation ion dose is 2×10⁻⁶. 16 ions / cm 2 The irradiation time was 2.8 hours, and the irradiation temperature was room temperature.

[0052] Figure 2 (a) is after He at room temperature 2+ TEM images of the microstructure of nickel-based alloys after irradiation show that no such features were observed. Figure 2 (b) shows the presence of He bubbles, which are common in irradiation experiments, with only some black spots observed.

[0053] Figure 3 The diffraction pattern and energy dispersive spectroscopy (EDS) images of the nickel-based alloy after room temperature irradiation are shown. The diffraction patterns reveal that the diffraction spots representing the ordered structure of the γ′ precipitates are weak, indicating that most of the γ′ precipitates in the alloy have become disordered. Figure 3The image also displays energy dispersive spectroscopy (EDS) images of the five main elements (Ni, Co, Cr, Ti, and Al) in the nickel-based alloy. Ni has a higher relative proportion within the γ′ precipitate, resulting in higher brightness in the image. Co and Cr are enriched in the matrix, while Ti and Al are enriched in the γ′ precipitate. The EDS images show that the morphology of the γ′ precipitate in the alloy is basically consistent with that of the sample before irradiation. Quantitative analysis of its size shows that the diameter of the γ′ precipitate remains within the range of 85-145 nm, with an average diameter of ~112 nm, and a volume fraction of 39.7%. This comparison indicates that the γ′ precipitate did not undergo significant dissolution after room temperature irradiation.

[0054] Example 2

[0055] The elemental composition of the nickel-based alloy was the same as in Example 1, and the other steps were the same as in Example 1. The aging conditions were changed to: aging temperature of 650 °C; aging time of 2 h; and cooling in air. After aging, the average diameter of the γ′ precipitate inside the nickel-based alloy was ~95 nm, and the volume fraction of the γ′ precipitate was 34.4%. The structural characteristics and γ′ precipitate distribution obtained after aging were similar to those in Example 1.

[0056] Example 3

[0057] The elemental composition of the nickel-based alloy was the same as in Example 1, and the other steps were the same as in Example 1. The aging conditions were changed to: aging temperature of 700 °C; aging time of 4 h; and cooling in air. After aging, the average diameter of the γ′ precipitate inside the nickel-based alloy was ~110 nm, and the volume fraction of the γ′ precipitate was 35.2%. The structural characteristics and γ′ precipitate distribution obtained after aging were similar to those in Example 1.

[0058] Comparative Example 1

[0059] The elemental composition of the nickel-based alloy was the same as in Example 1. The nickel-based alloy base material underwent only solution treatment, without aging. The solution treatment temperature was 1100 °C; the solution treatment time was 4 h. After solution treatment, the diameter distribution of the γ′ precipitates inside the nickel-based alloy was between 50-80 nm, with an average diameter of ~66 nm, and the volume fraction of the γ′ precipitates was 29.7%.

[0060] When nickel-based alloys undergo only solution treatment, the size of the internal γ′ precipitates is small, and their volume fraction is also small. The distribution of the γ′ precipitates is not completely uniform, which cannot effectively improve the alloy's performance.

[0061] Comparative Example 2

[0062] The literature Judge CD, Bhakhri V, et al. The effects of proton irradiation on the microstructural and mechanical property evolution of inconel X-750 with high concentrations of helium[J]. Journal of Nuclear Materials, 2017, 492:213-226. mentions that Judge et al. subjected Inconel X-750 nickel-based alloys to proton irradiation at different temperatures, and a large number of voids appeared in the alloy after irradiation. Pre-implanting the alloy with He can effectively suppress the formation of voids in the alloy, but it only has a suppressive effect and cannot completely eliminate the existence of voids in the alloy. In addition, after irradiation at 380 °C, most of the γ′ precipitates inside the alloy became disordered and dissolved.

[0063] Comparative Example 3

[0064] In the literature Yang LX, Ge HL, et al. High He-ion irradiation resistance of CrMnFeCoNi high-entropy alloy revealed by comparison study with Ni and 304SS[J]. Journal of Materials Science & Technology, 2019, 35(3):300-305., Yang et al. compared the microstructure evolution behavior of CrMnFeCoNi high-entropy alloy, pure nickel, and 304SS stainless steel under He ion irradiation. Regardless of whether irradiation was carried out at room temperature or 450 °C, a large number of diffusely distributed He bubbles and stacking fault tetrahedra appeared inside the three materials.

[0065] Comparative Example 4

[0066] LiteratureYeli G, Chen D, Yabuuchi K, et al. The stability of γ′precipitates in a multi-component FeCoNiCrTi 0.2In the paper "Alloy Under Elevated-Temperature Irradiation [J]. Journal of Nuclear Materials, 2020, 540:152364," Yeli et al. systematically studied FeCoNiCrTi alloys under elevated-temperature irradiation. 0.2 High-entropy alloys are subjected to 6.4 MeV energy Fe in the temperature range of 400-600 ℃. 3+ The evolution of the γ′ precipitate after ion irradiation. They found that at a peak irradiation dose of 13 dpa, the γ′ phase inside the sample became completely disordered and partially dissolved, and the dissolution phenomenon started from the surface of the precipitate.

[0067] Comparative Example 5

[0068] In the literature Zhang HK, Yao Z, Kirk MA, et al. Stability of Ni3(Al, Ti) GammaPrime Precipitates in a Nickel-Based Superalloy Inconel X-750 Under Heavy Ion Irradiation[J]. Metallurgical and Materials Transactions A, 2014, 45(8):3422-3428., Zhang et al. investigated the Kr values ​​of X-750 nickel-based alloy under different temperatures and irradiation doses. 2+ In the ion irradiation experiment, the irradiation energy was 1 MeV. When the irradiation temperature was [value missing], the γ′ precipitated phase became disordered under a dose condition of 0.06 dpa and dissolved significantly at 5.4 dpa.

[0069] The results show that, by utilizing a reasonable elemental composition design and combining it with an appropriate heat treatment process, this invention yields a nickel-based alloy containing nanoscale γ′ precipitates. The diameter of the γ′ precipitates within the alloy is distributed between 85-140 nm, and the volume fraction of the γ′ precipitates is 30-40%. The nickel-based alloy undergoes He... 2+ After ion irradiation, no widespread He was found in the alloy. 2+ In ion irradiation experiments, He bubbles commonly exhibit only disordering of the γ′ precipitate without dissolution after room temperature irradiation. The nickel-based alloy prepared by this invention possesses excellent radiation resistance.

Claims

1. A radiation-resistant nickel-based alloy, characterized in that, The nickel-based alloy grains are uniformly distributed with nanoscale γ′ precipitates. The main constituent elements of the γ′ phase are Ni, Ti and Al. The γ′ phase exhibits an L12 ordered superlattice structure and, like the matrix γ, has a face-centered cubic structure. The diameter of the γ′ precipitate inside the nickel-based alloy is between 85 and 140 nm, and the volume fraction of the γ′ precipitate is 30-40%. The elemental composition of this nickel-based alloy, expressed as atomic percentages (at.%), is as follows: Ni: 38-58%, Co: 15-30%, Cr: 10-20%, Ti: 3-9%, Al: 1-8%, Mo: 1-4%, W: 0.5-3%, Fe: 0.5-2%, Zr: 0.02-0.05%, C: 0.05-0.2%, B: 0.05-0.2%.

2. A method for preparing the radiation-resistant nickel-based alloy as described in claim 1, characterized in that, The specific steps are as follows: (1) The metal raw materials are subjected to vacuum induction melting, homogenization treatment and forging treatment in sequence according to the element ratio to obtain a cast-forged nickel-based alloy; (2) The nickel-based alloy in step (1) is subjected to solid solution treatment to dissolve the non-uniformly distributed primary precipitates in the alloy to obtain a nickel-based alloy containing nanoscale γ′ precipitates. (3) The nickel-based alloy from step (2) is subjected to aging treatment.

3. The method as described in claim 2, characterized in that, The metal raw materials are smelted according to the stated element ratio using a vacuum induction melting furnace, with the furnace evacuated to a vacuum level of 1×10⁻⁶. -2 Pa is filled with argon gas for protection.

4. The method as described in claim 2, characterized in that, The homogenization treatment was carried out at a temperature of 1100 ℃ for 48 h.

5. The method as described in claim 2, characterized in that, The forging temperature is 1050 ℃ and the forging ratio is 4.

6. The method as described in claim 2, characterized in that, The solution treatment temperature is 1050-1150 ℃, the treatment time is 3-6 h, and the cooling method is air cooling.

7. The method as described in claim 2, characterized in that, The aging treatment temperature is 650-750 ℃, the treatment time is 1-4 h, and the cooling method is air cooling.

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