Dispersion-strengthened creep-resistant nickel-based alloy for microreactors and its manufacturing method

Abstract

Dispersion-strengthened creep-resistant nickel-based alloy for microreactors and its manufacturing method, belonging to the field of nickel-based alloys. By weight ratio, the alloy includes 14.0% - 20.0% of Cr, 2.0% - 10.0% of Fe, 0.2% - 1.0% of Ti, 0.2% - 1.0% of Zr, 0.05% - 1.0% of Al, 0.2% - 0.8% of Si, not more than 0.05% of C, as well as 0.31% - 1.42% of Y, 0.01% - 0.4% of O, and the balance is Ni and inevitable impurities. The alloy has good mechanical properties and creep properties above 950 °C, can effectively improve the reliability of the structural components of the microreactor, and improve the economy of the microreactor.

Description

Technical Field

[0001] The present invention belongs to the field of nickel-based alloys, and particularly relates to a dispersion-strengthened creep-resistant nickel-based alloy for a micro-reactor and a manufacturing method thereof. Background Art

[0002] With the development of civil nuclear power technology, micro-reactors have received increasing attention. Micro-reactors are small in volume, simple in system structure, and high in inherent safety, and are considered to have good prospects in application scenarios such as power supply in remote areas, deep space and deep sea exploration, etc., where there is a lack of external support or unmanned operation. Therefore, the structural materials of micro-reactors face the design requirements of serving at ultra-high temperatures and being maintained without refueling for years, and need to have better high-temperature mechanical properties, high-temperature durability, and reliability. Nickel-based superalloys have excellent high-temperature performance and processing performance, and at the same time have the advantage of resistance to irradiation swelling. Currently, they are one of the structural materials preferentially considered in the design of micro-reactors. However, existing high-temperature nickel-based alloys such as Alloy 718 and Alloy 230 cannot serve at temperatures above 950°C, and their high-temperature mechanical properties, creep properties, and irradiation damage resistance cannot meet the design requirements of micro-reactors. Therefore, providing a nickel-based alloy with higher performance has positive significance for improving the reliability and economy of micro-reactors. Summary of the Invention

[0003] The purpose of the present invention is to provide a dispersion-strengthened creep-resistant nickel-based alloy for a micro-reactor, which has good creep resistance under high-temperature irradiation conditions.

[0004] According to an embodiment of one aspect of the present invention, a dispersion-strengthened creep-resistant nickel-based alloy for a micro-reactor is provided. The alloy includes, by weight ratio, 14.0%-20.0% of Cr, 2.0%-10.0% of Fe, 0.2%-1.0% of Ti, 0.2%-1.0% of Zr, 0.05%-1.0% of Al, 0.2%-0.8% of Si, not more than 0.05% of C, and 0.31%-1.42% of Y, 0.01%-0.4% of O, with the balance being Ni and inevitable impurities.

[0005] The alloy has good creep resistance under high-temperature conditions of 950°C and is suitable for manufacturing structural components of micro-reactors.

[0006] Further, in some embodiments, in the alloy, by weight ratio, Zr:Al:Si = 3:1:4.

[0007] By controlling the ratio of Zr, Al, and Si, it is promoted that the alloy composition forms uniformly dispersed precipitate particles, reducing the formation of supersaturated solid solution, thereby reducing the risk of grain boundary segregation under high-temperature irradiation conditions.

[0008] Further, in some embodiments, the matrix of the dispersion-strengthened creep-resistant nickel-based alloy for the micro-reactor is a nickel matrix, in which dispersed precipitation phase particles are distributed, and the dispersed precipitation phase particles include Y-Zr-O particles, Y-Al-O particles, and Y-Si-O particles.

[0009] Further, in some embodiments, in the microstructure of the dispersion-strengthened creep-resistant nickel-based alloy for the micro-reactor, the size of the dispersed precipitation phase particles at the grain boundaries is larger than that of the dispersed precipitation phase particles within the grains.

[0010] The larger-sized precipitation phases in the alloy are pinned at the grain boundaries, which helps to inhibit grain boundary migration under high-temperature conditions; the relatively smaller-sized precipitation phases are dispersed within the grains, which can further improve the creep resistance of the material.

[0011] Further, in some embodiments, the dispersion-strengthened creep-resistant nickel-based alloy for the micro-reactor has a yield strength of not less than 165 MPa, a tensile strength of not less than 169 MPa, and an elongation after fracture of not less than 40% at 1000 °C; the creep rupture limit stress at 1000 °C / 5 dpa for 10000 h is not less than 50 MPa.

[0012] According to an embodiment of another aspect of the present invention, there is provided a manufacturing method of a dispersion-strengthened creep-resistant nickel-based alloy for a micro-reactor, the method comprising the following steps:

[0013] Step a): Providing powder raw materials, the powder raw materials comprising 14.0% - 20.0% of Cr, 2.0% - 10.0% of Fe, 0.2% - 1.0% of Ti, 0.2% - 1.0% of Zr, 0.05% - 1.0% of Al, 0.2% - 0.8% of Si, not more than 0.05% of C, and 0.4% - 1.8% of Y2O3 particles by weight ratio, with the balance being Ni;

[0014] Step b): Performing hot isostatic pressing on the powder raw materials to obtain an alloy billet;

[0015] Step c): Performing forging on the alloy billet to obtain a forged billet;

[0016] Step d): Performing heat treatment and cold rolling on the forged billet to obtain a cold-rolled billet;

[0017] Step e): Performing annealing on the cold-rolled billet to obtain a finished dispersion-strengthened creep-resistant nickel-based alloy for the micro-reactor.

[0018] Further, in some embodiments, in step a), in the powder raw materials, Zr:Al:Si = 3:1:4, and the particle size of the Y2O3 particles is 100 nm - 500 nm.

[0019] Further, in some embodiments, in step b), the temperature of the hot isostatic pressing treatment is 1200°C - 1300°C, and the time is 2h - 4h.

[0020] Further, in some embodiments, in step d), the heat treatment process is as follows: first, keep the temperature at 1200°C - 1300°C for 1h - 3h, and then cool down to 700°C - 900°C and continue to keep the temperature for 1h - 3h; the total deformation amount of the cold rolling treatment is 20% - 40%.

[0021] Further, in some embodiments, in step e), the annealing treatment temperature is (1300 - 1000x)°C, where x is the total deformation amount of the cold rolling treatment in step d).

[0022] Further, the method for manufacturing the dispersion-strengthened creep-resistant nickel-based alloy for a microreactor provided in the above embodiments is used to manufacture the dispersion-strengthened creep-resistant nickel-based alloy for a microreactor provided in any one of the foregoing embodiments. Description of the Drawings

[0023] Figure 1 It is a transmission electron microscope photograph of the nickel-based alloy structure in an embodiment;

[0024] Figure 2 It is a transmission electron microscope photograph of the nickel-based alloy structure in a comparative example;

[0025] Figure 3 It is Figure 2 The distribution map of Si element in

[0026] The purpose of the above 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 aiming to limit the present invention. Detailed Embodiments

[0027] The present invention will be further described in detail below through specific embodiments.

[0028] When "embodiment" is mentioned herein, it means that the specific features, structures or characteristics described in combination with the embodiment can be included in at least one embodiment of the present invention. The phrase appearing at 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 the present invention can be combined with other embodiments without structural conflicts.

[0029] In the description herein, the meaning of "a plurality of" is at least two.

[0030] All kinds of microreactors represented by the heat pipe microreactor have simple structures, small volumes, and good inherent safety, and have broad application prospects in the fields of scientific research, disaster relief, environmental protection, etc. Since the application scenarios of microreactors usually lack external support and even need to be in an unattended state for a long time, the safety and reliability of microreactors are particularly important. At the same time, in order to improve the economy of microreactors, their operating temperatures are higher than those of conventional commercial reactors, and can even reach above 950 °C. Under such high-temperature irradiation conditions, the high-temperature mechanical properties, radiation damage resistance properties, especially the high-temperature creep properties of conventional superalloys such as Alloy 718 and Alloy 230 are insufficient and can no longer meet the design requirements of microreactors.

[0031] To solve the above problems, an embodiment of the present invention provides a dispersion-strengthened creep-resistant nickel-based alloy for a microreactor, which can serve stably for a long time above 950 °C and has good high-temperature mechanical properties and creep properties.

[0032] By weight ratio, the alloy includes 14.0%-20.0% of Cr, 2.0%-10.0% of Fe, 0.2%-1.0% of Ti, 0.2%-1.0% of Zr, 0.05%-1.0% of Al, 0.2%-0.8% of Si, no more than 0.05% of C, and 0.31%-1.42% of Y, 0.01%-0.4% of O, and the balance is Ni and inevitable impurities.

[0033] In order to reduce the formation of supersaturated solid solutions and fully form dispersed strengthening particles in the alloy matrix, in a preferred embodiment, Zr:Al:Si = 3:1:4 is further controlled. Under this ratio, the elements Zr, Al, and Si can fully participate in the formation of dispersed Y-Zr-O particles, Y-Al-O particles, and Y-Si-O particles, thereby avoiding grain boundary segregation of Zr, Al, and Si under high-temperature irradiation conditions, which causes material embrittlement. By controlling the total amount and ratio of Zr, Al, and Si, the precipitates with larger sizes are pinned at the grain boundaries to inhibit grain boundary migration under high-temperature stress conditions to improve the creep resistance; the precipitates with smaller sizes are dispersed in the grains to further improve the high-temperature mechanical properties of the material; the remaining O element is also beneficial to the improvement of creep properties. A higher Cr element is beneficial to improving the high-temperature corrosion resistance. At the same time, based on the material characteristics involved in the present invention, the high-content Cr element does not segregate in the irradiation environment, but is pinned at the particle / matrix interface by the dispersed particles; the added Fe element can partially replace Ni, thereby reducing the irradiation embrittlement defects caused by Ni after neutron irradiation; the Ti element is used for solid solution strengthening.

[0034] The yield strength of this alloy is not less than 165 MPa at 1000 °C, the tensile strength is not less than 169 MPa, and the elongation after fracture is not less than 40%, showing good high-temperature performance. The creep rupture limit stress at 1000 °C / 5 dpa for 10000 h is not less than 50 MPa, showing good creep performance.

[0035] The dispersion-strengthened creep-resistant nickel-based alloy for a microreactor provided in the above embodiments can be manufactured by the manufacturing method provided in an embodiment of another aspect of the present invention. This method specifically includes the following steps:

[0036] Step a): Provide powder raw materials. The powder raw materials include alloy powders containing 14.0% - 20.0% of Cr, 2.0% - 10.0% of Fe, 0.2% - 1.0% of Ti, 0.2% - 1.0% of Zr, 0.05% - 1.0% of Al, 0.2% - 0.8% of Si, and not more than 0.05% of C by weight, and Y2O3 particles accounting for 0.4% - 1.8% of the total weight of the powder raw materials (converted to Y content of about 0.31% - 1.42% and O content of about 0.01% - 0.4%), with the balance being pure Ni powder. In a preferred embodiment, Zr:Al:Si = 3:1:4 in the powder raw materials, and the particle size of the Y2O3 particles is from 100 nm to 500 nm.

[0037] Step b): Mix the powder raw materials evenly. For example, ball milling can be used for mixing, and then it is loaded into a mold for vacuum degassing treatment. After welding and sealing the mold, it is loaded into a hot isostatic pressing furnace and subjected to hot isostatic pressing treatment at 1250 °C for 2.5 h with a pressure of at least 100 MPa to obtain an alloy billet.

[0038] Step c): Perform hot forging treatment on the alloy billet to further eliminate the pore defects in the alloy billet, promote tissue homogenization, break up the possible solidification structure, and obtain a forged billet with uniform structure.

[0039] Step d): Keep the forged billet at 1250 °C for 2 h, cool it down to 800 °C and continue to keep it for 2 h, then cool it with the furnace, and then perform cold rolling processing to obtain a cold-rolled billet, where the total cold rolling deformation is 20% - 40%.

[0040] Step e): Perform annealing treatment on the cold-rolled billet. The annealing temperature is (1300 - 1000x) °C, where x is the total cold rolling deformation in step d). The annealing time is adaptively adjusted according to the recrystallization degree of the material, and it is appropriate for the alloy structure to undergo sufficient recrystallization, avoiding incomplete heating that leaves deformed grains in the structure or overheating that causes abnormal grain growth. After annealing treatment, the finished product of the dispersion-strengthened creep-resistant nickel-based alloy for a microreactor is obtained.

[0041] In a preferred embodiment, the dispersion-strengthened creep-resistant nickel-based alloy for the micro-reactor is manufactured by the following method:

[0042] The powder raw material components by weight ratio are: Cr 18.0%, Fe 5.0%, Al 0.2%, Ti 0.6%, Zr 0.6%, Si 0.8%, Y2O3 particles 1.0%, C < 0.05%, and the rest is Ni.

[0043] Mix the powder raw materials evenly, load them into a mold, compact and degas, seal by welding, and then load them into a hot isostatic pressing furnace for hot isostatic pressing treatment. The heating temperature is 1250 °C, the pressure is at least 100 MPa, and the holding time is 2.5 h to obtain an alloy billet.

[0044] Perform hot forging on the alloy billet. The forging temperature is 850 °C and the total deformation is 35% to obtain a forged billet. Load the forged billet into a muffle furnace, hold it at 1250 °C for 2 h, cool it down to 800 °C and continue to hold for 2 h, and take it out after cooling with the furnace. Subsequently, perform cold rolling with a total cold rolling deformation of 20% to obtain a cold-rolled billet. Anneal the cold-rolled billet at 1100 °C for 2 h to obtain the alloy finished product.

[0045] The microstructure morphology of the alloy finished product under a transmission electron microscope is as Figure 1 shown. It can be seen that uniformly dispersed smaller precipitates are formed within the Ni matrix grains, and the larger precipitates are pinned at the grain boundaries.

[0046] Test the high-temperature mechanical properties and creep properties of the alloy. Its yield strength at 1000 °C is 178 MPa, the tensile strength is 180 MPa, and the elongation after fracture reaches 40%; the creep fracture limit stress at 1000 °C / 5 dpa for 10000 h is 72 MPa.

[0047] In another preferred embodiment, the dispersion-strengthened creep-resistant nickel-based alloy for the micro-reactor is manufactured by the following method:

[0048] The powder raw material components by weight ratio are: Cr 18.0%, Fe 5.0%, Al 0.1%, Ti 0.6%, Zr 0.3%, Si 0.4%, Y2O3 particles 0.6%, C < 0.05%, and the rest is Ni.

[0049] Mix the powder raw materials evenly, load them into a mold, compact and degas, seal by welding, and then load them into a hot isostatic pressing furnace for hot isostatic pressing treatment. The hot isostatic pressing heating temperature is 1250 °C, the pressure is at least 100 MPa, and the heating time is 2.5 h to obtain an alloy billet.

[0050] The alloy billet is subjected to hot forging at a hot forging temperature of 850 °C and a total deformation of 35% to obtain a forged billet. The forged billet is loaded into a muffle furnace for heat treatment. It is held at 1250 °C for 2 h in the muffle furnace, cooled to 800 °C and held for another 2 h, and then taken out after furnace cooling. Subsequently, cold rolling is carried out with a total cold rolling deformation of 30% to obtain a cold-rolled billet. The cold-rolled billet is annealed at 1000 °C for 2 h to obtain the alloy product.

[0051] The high-temperature mechanical properties and creep properties of the alloy are tested. Its yield strength at 1000 °C is 168 MPa, the tensile strength is 169 MPa, and the elongation after fracture reaches 47%; the creep fracture limit stress at 1000 °C / 5 dpa for 10000 h is 60 MPa.

[0052] In yet another preferred embodiment, the dispersion-strengthened creep-resistant nickel-based alloy for a microreactor is manufactured by the following method:

[0053] The powder raw material components by weight ratio are: Cr 16.0%, Fe 10.0%, Al 0.2%, Ti 0.6%, Zr 0.6%, Si 0.8%, Y2O3 particles 1.6%, C < 0.05%, and the rest is Ni.

[0054] The powder raw materials are mixed evenly, loaded into a mold, compacted and degassed, welded and sealed, and then loaded into a hot isostatic pressing furnace for hot isostatic pressing treatment. The hot isostatic pressing heating temperature is 1250 °C, the pressure is at least 100 MPa, and the heating time is 2.5 h to obtain an alloy billet.

[0055] The alloy billet is subjected to hot forging at a hot forging temperature of 850 °C and a total deformation of 35% to obtain a forged billet. The forged billet is loaded into a muffle furnace and held at 1250 °C for 2 h, cooled to 800 °C and held for another 2 h, and then taken out after furnace cooling. Subsequently, cold rolling is carried out with a total cold rolling deformation of 40% to obtain a cold-rolled billet. The cold-rolled billet is annealed at 900 °C for 2 h to obtain the alloy product.

[0056] The high-temperature mechanical properties and creep properties of the alloy are tested. Its yield strength at 1000 °C is 170 MPa, the tensile strength is 180 MPa, and the elongation after fracture reaches 42%; the creep fracture limit stress at 1000 °C / 5 dpa for 10000 h is 58 MPa.

[0057] In a comparative example, the nickel-based alloy sample is manufactured by the following method:

[0058] The powder raw material components by weight ratio are: Cr 16.0%, Fe 10.0%, Al 1.5%, Ti 0.6%, Zr 1.2%, Si 1.5%, Y2O3 particles 3.9%, C < 0.05%, and the rest is Ni.

[0059] The process parameters in the manufacturing process of the nickel-based alloy of the comparative example are the same as those of the previous comparative example.

[0060] The microstructure morphology of the alloy finished product under a transmission electron microscope is as Figure 2 shown. It can be seen that the sizes of both intragranular precipitation phases and grain boundary precipitation phases are significantly larger than those in Figure 1 the examples. For Figure 2 the microstructure in, the energy spectrum analysis of Si is carried out, and the result is as Figure 3 shown. It can be seen that there is obvious grain boundary aggregation of Si element.

[0061] The high-temperature mechanical properties and creep properties of this alloy are tested. Its yield strength at 1000 °C is 320 MPa, the tensile strength is 385 MPa, and the elongation after fracture is only 11%; the creep fracture limit stress at 1000 °C / 5 dpa for 10000 h is only 9 MPa, and the creep performance is very low, making it difficult to meet the use requirements.

[0062] Through the comparison of the above examples and comparative examples, it can be known that the dispersion-strengthened creep-resistant nickel-based alloy provided by the embodiments of the present invention has good mechanical properties and creep properties above 950 °C, is suitable for long-term service under the high-temperature stress conditions of a microreactor, can effectively improve the strength and reliability of the structural components of the microreactor, enable the microreactor to work at a higher temperature, and achieve better economy.

[0063] The purpose of the above embodiments 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 dispersion-strengthened creep-resistant nickel-based alloy for a microreactor, characterized in that, By weight, it includes 14.0% - 20.0% of Cr, 2.0% - 10.0% of Fe, 0.2% - 1.0% of Ti, 0.2% - 1.0% of Zr, 0.05% - 1.0% of Al, 0.2% - 0.8% of Si, no more than 0.05% of C, and 0.31% - 1.42% of Y, 0.01% - 0.4% of O, with the balance being Ni and inevitable impurities. By weight, Zr:Al:Si = 3:1:4; the matrix of the dispersion-strengthened creep-resistant nickel-based alloy for the micro-reactor is a nickel matrix, in which dispersed precipitation phase particles are distributed. The dispersed precipitation phase particles include Y-Zr-O particles, Y-Al-O particles, and Y-Si-O particles; The dispersion-strengthened creep-resistant nickel-based alloy for the micro-reactor has a yield strength of not less than 165 MPa, a tensile strength of not less than 169 MPa, and an elongation after fracture of not less than 40% at 1000 °C; the creep rupture limit stress at 1000 °C / 5 dpa for 10000 h is not less than 50 MPa.

2. The dispersion-strengthened creep-resistant nickel-based alloy for a microreactor according to claim 1, wherein In the microstructure of the dispersion-strengthened creep-resistant nickel-based alloy for the micro-reactor, the size of the dispersed precipitation phase particles at the grain boundaries is larger than that of the dispersed precipitation phase particles within the grains.

3. A manufacturing method of a dispersion-strengthened creep-resistant nickel-based alloy for a microreactor, characterized in that, A method for manufacturing the dispersion-strengthened creep-resistant nickel-based alloy for the micro-reactor as claimed in claim 1 or 2, comprising the following steps: Step a): Provide powder raw materials, which by weight include 14.0% - 20.0% of Cr, 2.0% - 10.0% of Fe, 0.2% - 1.0% of Ti, 0.2% - 1.0% of Zr, 0.05% - 1.0% of Al, 0.2% - 0.8% of Si, no more than 0.05% of C, and 0.4% - 1.8% of Y2O3 particles, with the balance being Ni; Step b): Perform hot isostatic pressing on the powder raw materials to obtain an alloy billet; Step c): Perform forging on the alloy billet to obtain a forged billet; Step d): Perform heat treatment and cold rolling on the forged billet to obtain a cold-rolled billet; Step e): Perform annealing on the cold-rolled billet to obtain the finished dispersion-strengthened creep-resistant nickel-based alloy for the micro-reactor.

4. The manufacturing method of the dispersion-strengthened creep-resistant nickel-based alloy for a microreactor according to claim 3, characterized in that, In step a), Zr:Al:Si = 3:1:4 in the powder raw materials, and the particle size of the Y2O3 particles is 100 nm - 500 nm.

5. The manufacturing method of the dispersion-strengthened creep-resistant nickel-based alloy for a micro-reactor according to claim 3, characterized in that, In step b), the temperature of the hot isostatic pressing is 1200 °C - 1300 °C, and the time is 2 h - 6. The manufacturing method of the dispersion-strengthened creep-resistant nickel-based alloy for a micro-reactor according to claim 3, wherein, ​ 7. The manufacturing method of the dispersion-strengthened creep-resistant nickel-based alloy for a microreactor according to claim 6, characterized in that, ​

Images