Brittlement-resistant FeCrAl alloy and manufacturing method thereof

Abstract

The invention discloses an embrittlement-resistant FeCrAl alloy and a manufacturing method thereof, and belongs to the field of metal materials. The invention relates to an embrittlement-resistant FeCrAl alloy, which comprises the following components in percentage by weight: 10.0 to 18.0 percent of Cr, 3.5 to 7.0 percent of Al, 0.2 to 0.8 percent of Si, 0.6 to 1.4 percent of Y, 0.4 to 1.3 percent of O, not more than 0.05 percent of C and the balance of Fe and inevitable impurities. The alloy can effectively reduce solid solution of the Al element in an alloy matrix, so that alloy embrittlement caused by segregation of Al under the high-temperature irradiation condition is reduced, the service life of a structural part adopting the alloy under the high-temperature irradiation condition is prolonged, and the reliability of the structural part adopting the alloy under the high-temperature irradiation condition is improved.

Description

Technical Field

[0001] The present invention belongs to the field of metallic materials, and particularly relates to a FeCrAl alloy resistant to embrittlement and a manufacturing method thereof. Background Art

[0002] FeCrAl alloys have good high-temperature corrosion resistance and excellent strength-ductility matching performance, and are widely used as structural materials in advanced nuclear energy systems. However, in order to enhance the corrosion resistance of FeCrAl alloys, a relatively high content of Al element is added, resulting in limited formability of the material. Under high-temperature or strong irradiation conditions, the Al element dissolved in the alloy matrix is prone to segregation, leading to obvious high-temperature embrittlement or irradiation embrittlement of the material. Therefore, the content of Al element in the current FeCrAl materials needs to be limited to less than 4.5% to ensure their comprehensive performance during long-term service in high-temperature and irradiation environments. This causes the FeCrAl alloy structural components in advanced nuclear energy systems to not fully utilize the corrosion resistance advantages brought by high Al content, restricting the further improvement of the mechanical properties and reliability of the nuclear energy system structural components. Summary of the Invention

[0003] The purpose of the present invention is to provide a FeCrAl alloy resistant to embrittlement, which can inhibit the embrittlement phenomenon of FeCrAl alloys under high-temperature or irradiation conditions on the basis of increasing the Al content. The present invention also provides a manufacturing method of a FeCrAl alloy resistant to embrittlement.

[0004] According to an embodiment of one aspect of the present invention, a FeCrAl alloy resistant to embrittlement is provided. By weight ratio, the alloy includes 10.0% - 18.0% of Cr, 3.5% - 7.0% of Al, 0.2% - 0.8% of Si, 0.6% - 1.4% of Y, 0.4% - 1.3% of O, and no more than 0.05% of C, with the balance being Fe and inevitable impurities.

[0005] Further, in some embodiments, by weight ratio, the alloy contains 10.0% - 18.0% of Cr, 4.8% - 7.0% of Al, 0.2% - 0.8% of Si, 0.6% - 1.4% of Y, 0.4% - 1.3% of O, and no more than 0.05% of C, with the balance being Fe and inevitable impurities.

[0006] Further, in some embodiments, the matrix of the FeCrAl alloy resistant to embrittlement includes uniformly dispersed Y-Si-Al-O quaternary oxide particles.

[0007] By controlling the ratios of Y, Si, Al, and O elements, the Al element can be mainly dispersed in the alloy matrix in the form of precipitated phases, thus effectively reducing the solid solution of the Al element in the alloy matrix, further inhibiting the embrittlement of the alloy caused by the grain boundary segregation of solid solution Al under high-temperature irradiation conditions, and further improving the strength and reliability of the alloy.

[0008] Further, in some embodiments, the average particle size of the Y-Si-Al-O quaternary oxide particles is ≤25 nm, and the number density is ≥10 23 / m 3 。

[0009] Further, in some embodiments, the embrittlement-resistant FeCrAl alloy has a yield strength ≥130 MPa, a tensile strength ≥140 MPa, and an elongation ≥25% at 850 °C; and an elongation ≥2.5% after being irradiated at 850 °C with 5 dpa.

[0010] According to an embodiment of another aspect of the present invention, a method for manufacturing an embrittlement-resistant FeCrAl alloy is provided, and the method includes the following steps: Step a): Provide raw materials, which include 10.0% - 18.0% of Cr, 3.5% - 7.0% of Al, 0.2% - 0.8% of Si, 0.6% - 1.4% of Y, 0.4% - 1.3% of O, and no more than 0.05% of C by weight ratio, and the balance is Fe and unavoidable impurities. Among them, Al and Si are added in the form of Al powder coated with SiO2, Y is added in the form of Y2O3 powder, and the remaining elements are added in the form of pure metal powder or alloy powder; Step b): Perform ball milling and mixing on the raw materials to obtain a mixed powder; Step c): Sinter the mixed powder by hot isostatic pressing to obtain an alloy blank; Step d): Perform forging on the alloy blank to obtain a forged blank; Step e): Perform annealing on the forged blank to obtain the finished embrittlement-resistant FeCrAl alloy.

[0011] Adding Si, Al, and O elements in the form of composite powder can, on the one hand, effectively and accurately control the element ratio, and on the other hand, promote the precipitation of Y-Si-Al-O quaternary oxide particles during the manufacturing process, reducing the solid solution of Al in the alloy matrix; manufacturing the alloy by hot isostatic pressing can reduce the appearance of liquid phase during the manufacturing process, further reducing the Al element in the solid solution state.

[0012] Further, in some embodiments, in step a), the raw materials contain 10.0% - 18.0% Cr, 4.8% - 7.0% Al, 0.2% - 0.8% Si, 0.6% - 1.4% Y, 0.4% - 1.3% O, and no more than 0.05% C by weight, with the balance being Fe and unavoidable impurities.

[0013] Further, in some embodiments, in step a), the particle size of the SiO2 - coated Al powder is ≤40 μm.

[0014] Further, in some embodiments, in step c), the treatment temperature of hot isostatic pressing is 1100°C - 1150°C, the holding time is 1 h - 2 h, and the pressure is 120 MPa - 170 MPa.

[0015] Further, in some embodiments, in step e), the annealing treatment temperature is 900°C - 1000°C, and the time is 1.5 h - 2.5 h.

[0016] Further, in some embodiments, this method is used to manufacture the embrittlement - resistant FeCrAl alloy provided in any of the foregoing embodiments. Description of the Drawings

[0017] Figure 1 It is a SEM photograph of the SiO2 - coated Al composite powder in an embodiment; Figure 2 It is a TEM photograph of the structure of the embrittlement - resistant FeCrAl alloy and the elemental distribution map within the photograph area in an embodiment.

[0018] The purpose of the above - mentioned drawings is to make a detailed description of the present invention so that those skilled in the art can understand the technical concept of the present invention, rather than to limit the present invention. Detailed Embodiments

[0019] The present invention will be further described in detail below through specific embodiments in conjunction with the drawings.

[0020] The mention of "embodiment" in this article means that the specific features, structures, or characteristics described in connection with the embodiment may be included in at least one embodiment of this article. The phrase that appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive independent or alternative embodiments. Those skilled in the art should be able to understand that the embodiments in this article can be combined with other embodiments without structural conflict.

[0021] In the description of this article, "a plurality of" means at least two.

[0022] Currently, conventional FeCrAl alloys have good high-temperature mechanical properties and certain radiation resistance, and can be used in the manufacture of various reactor structural components. However, for alloys with a Cr content of 10%-18%, the Al element is prone to grain boundary segregation under high-temperature irradiation conditions, causing significant embrittlement of the alloy. Therefore, documents such as "Alloy design and characterization of arecrystallized FeCrAl-ODS cladding for accident-tolerant BWR fuels: An overview of research activity in Japan. J Nucl Mater, 2023, 583, 154508." point out that it is necessary to control the weight ratio of the Al element at 5% or lower to reduce the serious negative impact on material properties caused by grain boundary embrittlement due to Al segregation. At that time, the Al element has a significant impact on improving the corrosion resistance of FeCrAl. The reduction of the Al element content will lead to a decrease in the corrosion resistance of the FeCrAl alloy, which is also not conducive to improving the service life and reliability of reactor structural components.

[0023] To overcome the above deficiencies, an embodiment of one aspect of the present invention provides a brittle-resistant FeCrAl alloy, which, by weight ratio, includes 10.0%-18.0% of Cr, 3.5%-7.0% of Al, 0.2%-0.8% of Si, 0.6%-1.4% of Y, 0.4%-1.3% of O, and no more than 0.05% of C, with the balance being Fe and unavoidable impurities.

[0024] In a preferred embodiment, the alloy contains 10.0%-18.0% of Cr, 4.8%-7.0% of Al, 0.2%-0.8% of Si, 0.6%-1.4% of Y, 0.4%-1.3% of O, and no more than 0.05% of C, by weight ratio, with the balance being Fe and unavoidable impurities.

[0025] Among them, the alloy matrix includes uniformly dispersed Y-Si-Al-O quaternary oxide particles. In a preferred embodiment, the distribution of the Y-Si-Al-O quaternary oxide particles in the alloy matrix is as Figure 2 shown. By comparing Figure 2 the distributions of different elements therein, it can be seen that the Fe and Cr elements are uniformly distributed in the alloy matrix, while the Y, Si, Al, and O elements are mainly concentrated in the quaternary precipitation phase particles 1, and there is almost no enrichment of the Al element near the grain boundary 2. In a preferred embodiment, the average particle size of the Y-Si-Al-O quaternary oxide particles ≤ 25 nm, and the number density ≥ 10 23 / m 3。

[0026] In conventional FeCrAl alloys, 80%-90% of the Al element is distributed in the alloy matrix in a solid solution form, and a small number exists in the form of ternary oxide precipitation phases. Through Figure 2 comparison, it can be seen that the embrittlement-resistant FeCrAl alloy provided by the embodiments of the present invention effectively reduces the Al content in solid solution in the alloy matrix, and thus can effectively prevent the grain boundary precipitation of the Al element under high temperature and / or irradiation conditions, and inhibit the catalytic tendency of the alloy.

[0027] The embrittlement-resistant FeCrAl alloy provided in the above embodiments has good high-temperature mechanical properties and irradiation embrittlement resistance. At 850°C, the yield strength of the alloy is ≥130 MPa, the tensile strength is ≥140 MPa, and the elongation is ≥25%; after irradiation treatment of 5 dpa at 850°C, the elongation after fracture of the alloy is ≥2.5%.

[0028] According to an embodiment of another aspect of the present invention, a method for manufacturing an embrittlement-resistant FeCrAl alloy is provided, and the method includes the following steps: Step a): Provide raw material powders. The raw material powders include 10.0%-18.0% of Cr, 3.5%-7.0% of Al, 0.2%-0.8% of Si, 0.6%-1.4% of Y, 0.4%-1.3% of O, and no more than 0.05% of C by weight ratio, and the balance is Fe and unavoidable impurities; in a preferred embodiment, the raw material powders contain 10.0%-18.0% of Cr, 4.8%-7.0% of Al, 0.2%-0.8% of Si, 0.6%-1.4% of Y, 0.4%-1.3% of O, and no more than 0.05% of C by weight ratio, and the balance is Fe and unavoidable impurities. Among them, Al and Si are added in the form of Al powders coated with SiO2; Y is added in the form of Y2O3 powders; the remaining elements are added in the form of pure metal powders or alloy powders. Specifically, in some embodiments, Fe-Cr alloy powders can be prepared by the gas atomization powder process; the sol-gel method is used to uniformly coat a layer of SiO2 on the surface of micron-sized pure Al powder to obtain composite powders. The morphology of the Al composite powders coated with SiO2 under an electron microscope is as Figure 1 shown, and its average particle size is ≤40 μm.

[0029] Step b): Perform ball milling and mixing treatment on the Fe-Cr alloy powders, the SiO2-coated Al composite powders, and the Y2O3 powders to obtain mixed powders, and the ball-to-material ratio for ball milling and mixing is 10:1, and the rotation speed is 400 rpm.

[0030] Step c): Load the mixed powder into a mold and perform hot isostatic pressing in a hot isostatic pressing furnace at a heating temperature of 1100°C - 1150°C, an insulation time of 1 h - 2 h, and a pressure of 120 MPa - 170 MPa to obtain an alloy blank.

[0031] Step d): Forge the alloy blank to obtain a forged blank. The purpose of the forging process is to further densify the structure of the alloy blank and eliminate defects such as pores remaining after the hot isostatic pressing process.

[0032] Step e): Anneal the forged blank to stabilize the microstructure and morphology of the alloy. The annealing temperature is 900°C - 1000°C and the time is 1.5 h - 2.5 h to obtain a brittle - resistant FeCrAl alloy product.

[0033] The above - mentioned method can be used to manufacture the brittle - resistant FeCrAl alloy provided in the foregoing embodiments. Since the hot isostatic pressing process is used for forming, the raw materials do not melt and there is no liquid phase during the forming process, effectively avoiding the appearance of non - uniform solidification structure and segregation. By adding Al, Si, and O elements in the form of Al2O3 powder coated with SiO2, the uniformity of the elemental composition is further improved, promoting the full participation of Al element in the formation of Y - Si - Al - O quaternary oxide particles and reducing the solid solution of Al in the alloy structure. The average particle size of the Y - Si - Al - O quaternary oxide particles in the finished alloy is ≤25 nm, and the number density is ≥10 23 / m 3 。

[0034] In the first preferred embodiment, the FeCrAl alloy is manufactured by the following method: Provide raw material powders, wherein by weight percentage: Cr accounts for 14.5%, Al accounts for 4.8%, Si accounts for 0.35%, Y accounts for 0.95%, O accounts for 0.65%, C < 0.05%, and the balance is Fe. Among them, Fe and Cr are added in the form of Fe - Cr alloy powder, Al and Si are added in the form of Al composite powder coated with SiO₂ with a particle size of about 20 μm, and Y is added in the form of Y₂O₃ powder.

[0035] Perform ball - milling on the raw material powders to obtain mixed powders.

[0036] Load the mixed powders into a mold and perform hot isostatic pressing at 1150°C for 2 h under a pressure of 150 MPa to obtain an alloy blank.

[0037] Forge the alloy blank to obtain a forged blank.

[0038] Anneal the forged blank in a muffle furnace at a heating temperature of 900°C - 1000°C for 2 h to obtain a brittle - resistant FeCrAl alloy product.

[0039] The yield strength of the alloy sample at 850 °C is 156 MPa, the tensile strength is 166 MPa, and the elongation after fracture is 42%; the elongation after fracture is 5.8% after irradiation treatment at 850 °C for 5 dpa.

[0040] In the second preferred embodiment, the FeCrAl alloy is manufactured by the following method: Raw material powders are provided, in which by weight percentage: Cr accounts for 14.2%, Al accounts for 5.5%, Si accounts for 0.61%, Y accounts for 1.18%, O accounts for 1.02%, C < 0.05%, and the balance is Fe. Among them, Fe and Cr are added in the form of Fe-Cr alloy powders, Al and Si are added in the form of Al composite powders coated with SiO2 with a particle size of about 20 μm, and Y is added in the form of Y2O3 powders.

[0041] The raw material powders are subjected to ball milling treatment to obtain a mixed powder.

[0042] The mixed powder is loaded into a mold and subjected to hot isostatic pressing treatment at 1150 °C for 2 h under 150 MPa to obtain an alloy blank.

[0043] The alloy blank is subjected to forging treatment to obtain a forged blank.

[0044] The forged blank is subjected to annealing treatment in a muffle furnace at a heating temperature of 900 °C - 1000 °C for 2 h to obtain a finished FeCrAl alloy resistant to embrittlement.

[0045] The yield strength of the alloy sample at 850 °C is 152 MPa, the tensile strength is 168 MPa, and the elongation after fracture is 41%; the elongation after fracture is 4.2% after irradiation treatment at 850 °C for 5 dpa.

[0046] In the third preferred embodiment, the FeCrAl alloy is manufactured by the following method: Raw material powders are provided, in which by weight percentage: Cr accounts for 15.5%, Al accounts for 6.7%, Si accounts for 0.77%, Y accounts for 1.34%, O accounts for 1.24%, C < 0.05%, and the balance is Fe. Among them, Fe and Cr are added in the form of Fe-Cr alloy powders, Al and Si are added in the form of Al composite powders coated with SiO2 with a particle size of about 20 μm, and Y is added in the form of Y2O3 powders.

[0047] The raw material powders are subjected to ball milling treatment to obtain a mixed powder.

[0048] The mixed powder is loaded into a mold and subjected to hot isostatic pressing treatment at 1150 °C for 2 h under 150 MPa to obtain an alloy blank.

[0049] The alloy blank is subjected to forging treatment to obtain a forged blank.

[0050] The forged blank is annealed in a muffle furnace at a heating temperature of 900 °C - 1000 °C for 2 h to obtain a brittle - resistant FeCrAl alloy finished product.

[0051] The yield strength of this alloy sample at 850 °C is 145 MPa, the tensile strength is 152 MPa, and the elongation after fracture is 35%; after irradiation treatment at 850 °C with 5 dpa, the elongation after fracture is 3.9%.

[0052] In the comparative example, a FeCrAl alloy is manufactured in the following manner: Raw material powders are provided, in which by weight percentage: Cr accounts for 15.4%, Al accounts for 6.6%, Si accounts for 0.78%, Y accounts for 1.31%, O accounts for 1.23%, C < 0.05%, and the balance is Fe. In the raw material powders, Y is added in the form of Y2O3 powder, and the remaining components are in the form of pure metal powders or homogeneous alloy powders.

[0053] The raw material powders are ball - milled and mixed, then loaded into a mold and subjected to hot isostatic pressing at 1150 °C under 150 MPa for 2 h, and then forged and annealed at 900 °C - 1000 °C for 2 h to obtain the comparative - example FeCrAl alloy.

[0054] The yield strength of this alloy sample at 850 °C is 188 MPa, the tensile strength is 201 MPa, and the elongation after fracture is 16%; after irradiation treatment at 850 °C with 5 dpa, the elongation after fracture is only 0.8%.

[0055] By comparing the above - mentioned examples with the comparative example, it can be seen that the brittle - resistant FeCrAl alloy provided by the present invention exhibits good mechanical properties and resistance to irradiation embrittlement under high - temperature irradiation conditions, and can effectively improve the service life and reliability of the structural components of nuclear power facilities.

[0056] The purpose of the above - mentioned examples is to further elaborate on the present invention in combination with the drawings so that those skilled in the art can understand the technical concept of the present invention. Within the scope disclosed by the present invention, optimizing or equivalently replacing the technical features involved, and combining the implementation manners in different embodiments without conflict in principle all fall within the protection scope of the present invention.

Claims

1. A brittle-resistant FeCrAl alloy, characterized in that, By weight, it includes 10.0% - 18.0% of Cr, 3.5% - 7.0% of Al, 0.2% - 0.8% of Si, 0.6% - 1.4% of Y, 0.4% - 1.3% of O, and no more than 0.05% of C, with the balance being Fe and inevitable impurities. During the manufacturing process of the embrittlement-resistant FeCrAl alloy, Al and Si are added in the form of Al powder coated with SiO2.

2. The embrittlement-resistant FeCrAl alloy according to claim 1, characterized in that, By weight, it contains 10.0% - 18.0% of Cr, 4.8% - 7.0% of Al, 0.2% - 0.8% of Si, 0.6% - 1.4% of Y, 0.4% - 1.3% of O, and no more than 0.05% of C, with the balance being Fe and inevitable impurities.

3. The embrittlement-resistant FeCrAl alloy according to claim 1 or 2, characterized in that, The matrix of the embrittlement-resistant FeCrAl alloy structure includes uniformly dispersed Y-Si-Al-O quaternary oxide particles.

4. The embrittlement-resistant FeCrAl alloy according to claim 3, characterized in that, The average particle size of the Y-Si-Al-O quaternary oxide particles is ≤ 25 nm, and the number density is ≥ 10 23 / m 3 .

5. The embrittlement-resistant FeCrAl alloy according to claim 4, characterized in that, The embrittlement-resistant FeCrAl alloy has a yield strength ≥ 130 MPa, a tensile strength ≥ 140 MPa, and an elongation ≥ 25% at 850 °C; the elongation ≥ 2.5% after being irradiated at 850 °C with a dose of 5 dpa.

6. A method for manufacturing a brittle-resistant FeCrAl alloy, characterized in that, It includes the following steps: Step a): Provide raw materials, which by weight include 10.0% - 18.0% of Cr, 3.5% - 7.0% of Al, 0.2% - 0.8% of Si, 0.6% - 1.4% of Y, 0.4% - 1.3% of O, and no more than 0.05% of C, with the balance being Fe and inevitable impurities. Among them, Al and Si are added in the form of Al powder coated with SiO2, Y is added in the form of Y2O3 powder, and the remaining elements are added in the form of pure metal powder or alloy powder; Step b): Conduct ball milling and mixing treatment on the raw materials to obtain a mixed powder; Step c): Sinter the mixed powder by hot isostatic pressing process to obtain an alloy billet; Step d): Conduct forging treatment on the alloy billet to obtain a forged billet; Step e): Conduct annealing treatment on the forged billet to obtain the finished product of the embrittlement-resistant FeCrAl alloy.

7. The manufacturing method of the brittle - resistant FeCrAl alloy according to claim 6, characterized in that, In step a), the raw materials by weight contain 10.0% - 18.0% of Cr, 4.8% - 7.0% of Al, 0.2% - 0.8% of Si, 0.6% - 1.4% of Y, 0.4% - 1.3% of O, and no more than 0.05% of C, with the balance being Fe and inevitable impurities.

8. The method for manufacturing a brittle - resistant FeCrAl alloy according to claim 6 or 7, characterized in that, In step a), the particle size of the Al powder coated with SiO2 is ≤ 40 μm.

9. The method for manufacturing a brittle fracture-resistant FeCrAl alloy according to claim 6 or 7, characterized in that, In step c), the treatment temperature of hot isostatic pressing is 1100 °C - 1150 °C, the holding time is 1 h - 2 h, and the pressure is 120 MPa - 170 MPa.

10. The method for manufacturing a brittle - resistant FeCrAl alloy according to claim 6 or 7, characterized in that, In step e), the annealing treatment temperature is 900 °C - 1000 °C, and the time is 1.5 h - 2.5 h.

11. The method for manufacturing a brittle fracture-resistant FeCrAl alloy according to claim 6 or 7, characterized in that, It is used to manufacture the embrittlement-resistant FeCrAl alloy as described in any one of claims 1 to 5.

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