A nickel-based alloy for high-power micro-reactor and a manufacturing method thereof

Abstract

A nickel-based alloy for a high-power micro-reactor comprises, by weight, 14.0%-29% Cr, 3.0%-5.0% Fe, 0.1%-2.0% Mn, 3.0%-5.0% Mo, 10.0%-18.0% W, 0.1%-0.5% Al, 0.15%-0.85% C, 0.005%-0.05% La, 0.01%-0.25% Si, 0.9%-6.8% Nb, and the remainder is Ni and unavoidable impurities; wherein, by weight, the ratio of Nb:C is 8:1-6:1, and Cr is not less than (7×C+14)%. The alloy has good high-temperature mechanical properties and radiation damage resistance, can be in long-term stable service in an irradiation environment above 900°C, and has good resistance to radiation embrittlement. The invention also provides a method for manufacturing the nickel-based alloy for a high-power micro-reactor.

Description

Technical Field

[0001] The invention belongs to the field of nuclear power, and in particular relates to a nickel-based alloy for a high-power micro-reactor and a manufacturing method thereof. Background Art

[0002] As a new type of reactor, high-power micro-reactors are small in size and flexible, so they are considered to have good application potential and have good application prospects in scenarios such as power generation in remote areas. Compared with traditional commercial reactors, high-power micro-reactors have higher operating temperatures, and the core temperature can reach over 900°C in service, which puts more stringent performance requirements on structural materials. At present, the high-temperature alloy materials used in traditional commercial reactors generally cannot meet the mechanical properties and irradiation performance requirements under high temperature conditions, which restricts the development and application of high-power micro-reactors. Therefore, providing a nickel-based alloy with better high-temperature radiation tolerance is of positive significance for the promotion of high-power micro-reactors. Summary of the invention

[0003] The purpose of the present invention is to provide a nickel-based alloy for a high-power micro-reactor, which can be used stably for a long time in an irradiation environment above 900°C. The present invention also provides a method for manufacturing the nickel-based alloy for a high-power micro-reactor.

[0004] According to an embodiment of one aspect of the present invention, there is provided a nickel-based alloy for a high-power micro-reactor, wherein the alloy comprises, by weight, 14.0%-29% Cr, 3.0%-5.0% Fe, 0.1%-2.0% Mn, 3.0%-5.0% Mo, 10.0%-18.0% W, 0.1%-0.5% Al, 0.15%-0.85% C, 0.005%-0.05% La, 0.01%-0.25% Si, 0.9%-6.8% Nb, and the remainder is Ni and unavoidable impurities; wherein, by weight, the ratio of Nb:C is 8:1-6:1, and Cr is not less than (7×C+14)%.

[0005] The alloy controls the content of Cr, Nb and C, so that dispersed carbides can be formed in the alloy. These carbides can capture helium bubbles generated under high-temperature irradiation conditions, prevent helium bubbles from aggregating and growing, thereby improving the alloy's resistance to radiation damage; at the same time, it can avoid embrittlement caused by segregation of Nb and C elements and improve the mechanical properties of the alloy. Specifically, when the Nb content is too low, the Nb content in the nickel alloy grains is low, and Nb gathers at the grain boundaries, resulting in a large difference in strength between the grain boundaries and the grains of the nickel alloy, which damages the mechanical properties; when the Nb content is within an appropriate range, in addition to the formation of NbC, the distribution of Nb elements at the grain boundaries and in the grains is relatively balanced; when Nb is excessive, Nb segregation will occur, causing the decline of the mechanical properties of the alloy.

[0006] Furthermore, in some embodiments, among the unavoidable impurities, by weight, Ti does not exceed 0.01%, Co does not exceed 0.01%, P does not exceed 0.01%, S does not exceed 0.005%, and B does not exceed 0.0001%.

[0007] The Co element is prone to transmutation under neutron irradiation conditions, producing strong induced radioactivity; the transmutation products of the B element in an irradiated environment are prone to cause embrittlement of nickel-based alloys.

[0008] Furthermore, in some embodiments, in the structure of the nickel-based alloy for high-power micro-reactor, the matrix is ​​a Ni-Cr solid solution, and NbC and Cr are distributed in the matrix. 23 C6 precipitation phase.

[0009] By controlling the content of Ni and C, Nb and C can be precipitated in the form of NbC, avoiding the reduction of alloy strength caused by separate precipitation; by controlling the content of Cr and C, the remaining C can be combined with Cr to form Cr 23 C6 precipitation phase prevents C from segregating at grain boundaries.

[0010] Furthermore, in some embodiments, the room temperature tensile elongation of the nickel-based alloy for high-power micro-reactor is not less than 5% after neutron irradiation treatment at 900°C / 3dpa.

[0011] Furthermore, in some embodiments, the nickel-based alloy for high-power micro-reactor is used to manufacture reactor structural parts, and the reactor structural parts include heat pipe micro-reactor core, gas-cooled reactor intermediate heat exchanger or molten salt reactor support structure.

[0012] According to another embodiment of the present invention, a method for manufacturing a nickel-based alloy for a high-power micro-reactor is provided, which is used to manufacture the nickel-based alloy for a high-power micro-reactor provided in any of the above embodiments, and comprises the following steps:

[0013] Providing alloy raw materials according to alloy components, and melting and casting the alloy raw materials into an alloy blank;

[0014] hot forging the alloy blank to obtain an alloy forging;

[0015] The alloy forging is heat treated to obtain an alloy finished product.

[0016] Furthermore, in some embodiments, the alloy raw material is melted by vacuum melting.

[0017] Furthermore, in some embodiments, the alloy forging is heat treated in a muffle furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1FIG. 1 is a transmission electron microscope photograph of the nickel-based alloy structure in one embodiment.

[0019] The purpose of the above drawings is to explain the present invention in detail so that those skilled in the art can understand the technical concept of the present invention, but it is not intended to limit the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below through specific embodiments.

[0021] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The phrase appearing in various locations 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 herein may be combined with other embodiments without causing structural conflicts.

[0022] In the description of this article, the terms "first", "second" and the like are only used to distinguish different objects, and cannot be understood as indicating relative importance or limiting the quantity, specific order or primary and secondary relationship of the described technical features. In the description of this article, the meaning of "plurality" is at least two.

[0023] Due to the high service temperature and harsh working conditions of commercial reactor cores, the structural materials used to manufacture core components need to have very high comprehensive performance. First, the structural materials need to have good high-temperature mechanical properties, meet the design requirements of high-temperature tensile strength, creep performance and other indicators, be able to serve stably for a long time at high temperatures, and have sufficient high-temperature chemical stability to resist high-temperature oxidation and corrosion; secondly, due to the need to withstand long-term neutron irradiation, the structural materials also need to have good radiation damage resistance, and should not experience significant radiation growth, swelling and embrittlement after long-term neutron irradiation. Performance degradation; finally, in order to reduce the radioactive contamination of waste, the structural materials should try to avoid using elements that are easily transmuted into long-half-life radioactive isotopes after absorbing neutrons, so as to reduce the total amount of high-level radioactive waste after scrapping. Due to the above limitations, many conventional high-temperature materials cannot be used in the construction of nuclear power facilities. The service temperature of existing high-temperature nickel-based alloys for nuclear power is usually 600℃-700℃. After exceeding this temperature range, the existing high-temperature nickel-based alloys for nuclear power are prone to creep failure or rapid embrittlement under high-temperature neutron irradiation conditions.

[0024] However, in order to further improve the power generation efficiency, the core temperature of the new high-power micro-reactor represented by the heat pipe micro-reactor is further increased. The core temperature under rated conditions can reach above 900°C. This results in the performance of existing nickel-based high-temperature alloys for nuclear power being unable to meet the design requirements of high-power micro-reactors, restricting the research and development of high-power micro-reactors.

[0025] In order to solve the above problems, an embodiment of one aspect of the present invention provides a nickel-based alloy for high-power micro-reactors, which can maintain good mechanical properties under neutron irradiation conditions above 900°C and has good resistance to irradiation embrittlement. The composition of the alloy contains 14.0%-29% Cr, 3.0%-5.0% Fe, 0.1%-2.0% Mn, 3.0%-5.0% Mo, 10.0%-18.0% W, 0.1%-0.5% Al, 0.15%-0.85% C, 0.005%-0.05% La, 0.01%-0.25% Si, 0.9%-6.8% Nb, and the balance is Ni and unavoidable impurities; wherein, the ratio of Nb:C is 8:1-6:1 by weight, and Cr is not less than (7×C+14)%.

[0026] In order to reduce the generation of induced radioactivity and avoid the accumulation of gas generated by transmutation of alloy elements after neutron capture in the tissue, in the preferred embodiment, the impurity elements in the alloy are further strictly controlled, and the weight ratio is such that Ti does not exceed 0.01%, Co does not exceed 0.01%, P does not exceed 0.01%, S does not exceed 0.005%, and B does not exceed 0.0001%.

[0027] By controlling the contents of C, Cr and Nb in the alloy, Nb is combined with carbon to form NbC precipitated phase evenly distributed in the alloy structure. NbC can capture helium bubbles generated during high-temperature irradiation and prevent helium bubbles from aggregating and growing in the alloy structure, thereby effectively improving the alloy's resistance to radiation embrittlement under high-temperature conditions; the remaining C element can fully combine with Cr in the alloy to form Cr 23 C6 precipitation phase is formed to avoid excessive carbon segregation at the grain boundary, which causes the alloy's mechanical properties to decrease. At the same time, the addition of Fe can replace part of Ni, thereby reducing the generation of helium bubbles to a certain extent. If the Fe content is too low, it will lead to the loss of plasticity after irradiation treatment, and if the Fe content is too high, it will have an adverse effect on the creep properties of the material; W and Mo can play a role in solid solution strengthening, but if they are excessive, they will cause segregation and affect the material strength; Si can improve the corrosion resistance of the material, but excessive Si is prone to cause material embrittlement due to segregation.

[0028] After neutron irradiation treatment at 900℃ / 3dpa, the alloy has a room temperature tensile elongation of no less than 5%, showing good resistance to radiation damage.

[0029] The alloy can be used to manufacture reactor structural parts, including but not limited to heat pipe micro-reactor cores, gas-cooled reactor intermediate heat exchangers and molten salt reactor support structures.

[0030] In a preferred embodiment, the alloy is obtained by vacuum melting raw materials, casting them into alloy blanks, and then hot forging and heat treating them.

[0031] In a first preferred embodiment, a nickel-based alloy for a high-power micro-reactor is manufactured in the following manner: alloy raw materials are configured according to the following components: by weight, Cr 16.6, Fe 3.5, Mn 4.0, Mo 4.0, W 16.2, Al 0.2, C0.15, La 0.02, Si 0.10, Ti<0.01, Nb 1.05, Co<0.01, P<0.01, S<0.005, B<0.0001, and the balance is Ni; the alloy raw materials are vacuum melted and cast into an alloy billet; the alloy billet is hot forged; the hot-forged alloy is placed in a muffle furnace for heat treatment to obtain a nickel-based alloy product.

[0032] The Co content in the alloy is controlled below 0.01% to avoid strong induced radioactivity in the micro-reactor; the B content is controlled below 0.0001% to reduce the gas produced by transmutation; by controlling the Nb and C contents to 7:1, Nb is precipitated to form a uniformly dispersed NbC phase, which acts as a trap to capture helium bubbles generated by irradiation and inhibits the aggregation and growth of helium bubbles in the alloy structure under high-temperature irradiation conditions; the remaining C and Cr elements form a carbide precipitation phase, which can avoid the segregation of C elements in areas such as grain boundaries, thereby improving the high-temperature mechanical properties and radiation damage resistance of the material.

[0033] After neutron irradiation treatment at 900℃ / 3dpa, the alloy was stretched at room temperature, and the elongation reached 5.2%.

[0034] In a second preferred embodiment, a nickel-based alloy for a high-power micro-reactor is manufactured in the following manner: alloy raw materials are configured according to the following components: by weight, Cr 23.1, Fe 3.5, Mn 4.0, Mo 4.0, W 16.2, Al 0.2, C 0.5, La 0.02, Si 0.10, Ti<0.01, Nb 3.5, Co<0.01, P<0.01, S<0.005, B<0.0001, and the balance is Ni; the alloy raw materials are vacuum melted and cast into an alloy billet; the alloy billet is hot forged; the hot-forged alloy is placed in a muffle furnace for heat treatment to obtain a nickel-based alloy product.

[0035] The Co content in the alloy is controlled below 0.01% to avoid strong induced radioactivity in the micro-reactor; the B content is controlled below 0.0001% to reduce the gas produced by transmutation; by controlling the Nb and C contents to 7:1, Nb is precipitated to form a uniformly dispersed NbC phase, which acts as a trap to capture helium bubbles generated by irradiation and inhibits the aggregation and growth of helium bubbles in the alloy structure under high-temperature irradiation conditions; the remaining C and Cr elements form a carbide precipitation phase, which can avoid the segregation of C elements in areas such as grain boundaries, thereby improving the high-temperature mechanical properties and radiation damage resistance of the material.

[0036] The alloy sample was cut to make a TEM (transmission electron microscope) specimen for TEM observation, and the photo is as follows: Figure 1 EDX analysis shows that dispersed NbC phase particles 1 are evenly distributed in the matrix, and Cr is precipitated near the grain boundary. 23 C6 phase particles 2.

[0037] After neutron irradiation treatment at 900℃ / 3dpa, the alloy was stretched at room temperature, and the elongation reached 8.8%.

[0038] In a third preferred embodiment, a nickel-based alloy for a high-power micro-reactor is manufactured in the following manner: alloy raw materials are configured according to the following components: by weight, Cr 28.9, Fe 3.5, Mn 4.0, Mo 4.0, W 16.2, Al 0.2, C0.85, La 0.02, Si 0.10, Ti<0.01, Nb 5.96, Co<0.01, P<0.01, S<0.005, B<0.0001, and the balance is Ni; the alloy raw materials are vacuum melted and cast into an alloy billet; the alloy billet is hot forged; the hot-forged alloy is placed in a muffle furnace for heat treatment to obtain a nickel-based alloy product.

[0039] The Co content in the alloy is controlled below 0.01% to avoid strong induced radioactivity in the micro-reactor; the B content is controlled below 0.0001% to reduce the gas produced by transmutation; by controlling the Nb and C contents to 7:1, Nb is precipitated to form a uniformly dispersed NbC phase, which acts as a trap to capture helium bubbles generated by irradiation and inhibits the aggregation and growth of helium bubbles in the alloy structure under high-temperature irradiation conditions; the remaining C and Cr elements form a carbide precipitation phase, which can avoid the segregation of C elements in areas such as grain boundaries, thereby improving the high-temperature mechanical properties and radiation damage resistance of the material.

[0040] After neutron irradiation treatment at 900℃ / 3dpa, the alloy was stretched at room temperature, and the elongation reached 10.1%.

[0041] Conventional 230 alloy is stretched at room temperature after neutron irradiation at 900℃ / 3dpa, and its elongation is less than 2%. In a comparative example, the nickel-based alloy composition is: Nb 8.1%, C<0.01%, Cr 12.5%, and the remaining components are the same as the first preferred embodiment. After being treated under the same conditions, the elongation of the nickel-based alloy in the comparative example is only 1.1%.

[0042] The nickel-based alloy for high-power micro-reactors provided in the above embodiment avoids the use of elements that are easy to increase induced radioactivity and elements that are easy to transmute and produce helium bubbles, and through reasonable control of the elements such as C, Nb, Cr in the alloy, a uniformly dispersed carbide precipitation phase is formed in the matrix, which can capture the helium bubbles produced under high-temperature irradiation conditions while enhancing the mechanical properties of the alloy structure, thereby effectively improving the mechanical properties and radiation damage resistance of the alloy under high-temperature irradiation conditions. The alloy is suitable for manufacturing metal structures such as core structural parts of high-power micro-reactors that need to serve for a long time under high-temperature irradiation conditions.

[0043] The purpose of the above embodiments is to explain the present invention in detail in conjunction with the accompanying drawings so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, the optimization or equivalent replacement of the components and method steps involved, and the combination of implementation methods in different embodiments without conflict of structure and principle, all fall within the protection scope of the present invention.

Claims

1. A nickel-based alloy for high-power micro-reactor, characterized in that: The nickel-based alloy for high-power micro-reactor is used to manufacture reactor structural parts; The composition of the nickel-based alloy for high-power micro-reactor contains, by weight, 14.0%-29% Cr, 3.0%-5.0% Fe, 0.1%-2.0% Mn, 3.0%-5.0% Mo, 10.0%-18.0% W, 0.1%-0.5% Al, 0.15%-0.85% C, 0.005%-0.05% La, 0.01%-0.25% Si, 0.9%-6.8% Nb, and the balance is Ni and unavoidable impurities; wherein, by weight, the ratio of Nb:C is 8:1-6:1, and Cr is not less than (7×C+14)%; After the nickel-based alloy for high-power micro-reactor is irradiated with neutrons at 900°C / 3dpa, the room temperature tensile elongation is not less than 5%.

2. The nickel-based alloy for high-power micro-reactor according to claim 1, characterized in that: Among the inevitable impurities, by weight, Ti does not exceed 0.01%, Co does not exceed 0.01%, P does not exceed 0.01%, S does not exceed 0.005%, and B does not exceed 0.0001%.

3. The nickel-based alloy for high-power micro-reactor according to claim 1, characterized in that: In the structure of the nickel-based alloy for high-power micro-reactor, the matrix is ​​a Ni-Cr solid solution, and NbC and Cr are distributed in the matrix. 23 C6 precipitation phase.

4. The nickel-based alloy for high-power micro-reactor according to claim 1, 2 or 3, characterized in that: The reactor structural parts include a heat pipe micro-reactor core, a gas-cooled reactor intermediate heat exchanger or a molten salt reactor support structure.

5. A method for manufacturing a nickel-based alloy for a high-power micro-reactor, characterized in that: Used to manufacture a nickel-based alloy for a high-power micro-reactor according to any one of claims 1 to 4, and comprising the following steps: Providing alloy raw materials according to alloy components, and melting and casting the alloy raw materials into an alloy blank; hot forging the alloy blank to obtain an alloy forging; The alloy forging is heat treated to obtain an alloy finished product.

6. The method for manufacturing a nickel-based alloy for a high-power micro-reactor according to claim 5, characterized in that: The alloy raw material is melted by vacuum melting.

7. The method for manufacturing a nickel-based alloy for a high-power micro-reactor according to claim 5, characterized in that: The alloy forging is heat treated in a muffle furnace.

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