Radiation-resistant nickel-chromium alloy for modular reactor cladding and preparation method of radiation-resistant nickel-chromium alloy

Abstract

The invention discloses an anti-radiation nickel-chromium alloy for a modular reactor cladding. The anti-radiation nickel-chromium alloy is prepared from the following elements in percentage by mass: 30%-45% of Cr, 0.5%-3% of Mo, 0.1%-0.4% of Al, 0.3%-0.6% of Fe, 0.05%-0.3% of W, 0.1%-0.25% of Ti, 0.03%-0.2% of C, 0.01%-0.2% of Ce and the balance of Ni and inevitable impurity elements. The preparation method of the alloy comprises the following steps: 1, uniformly mixing materials; 2, vacuum melting; thirdly, multi-heating-number forging is conducted; and 4, heat treatment cooling. According to the nickel-chromium alloy, Ni serves as a matrix, Cr and Mo serve as main alloying elements, a stable and uniform solid solution strengthening austenite phase is formed, and the alloy has excellent mechanical strength, corrosion resistance, radiation resistance and machining performance; the comprehensive mechanical property and the structural stability of the alloy are guaranteed through multi-heating-number forging and heat treatment.

Description

Technical Field

[0001] The invention relates to the technical field of nickel-based alloy preparation, and in particular to a radiation-resistant nickel-chromium alloy for modular reactor cladding and a preparation method thereof. Background Art

[0002] The fuel core is the core of the nuclear reactor to achieve nuclear fission, while the cladding is the component that directly loads the fuel core. As the most important safety barrier of the reactor, the cladding is mainly used to prevent the escape of fission products and the pollution of the surrounding environment, isolate the fuel core and coolant to prevent chemical reactions, and provide sufficient structural strength to maintain structural integrity under the condition of high-pressure coolant flushing. Therefore, the choice of cladding alloy material determines the service life and safety and reliability of the nuclear reactor. Zirconium alloy is the most widely used cladding alloy material in current nuclear reactors. However, its poor corrosion resistance at high temperatures has never been solved, which has buried hidden dangers for the safety of nuclear reactors. Therefore, the research and development of a new generation of nuclear fuel cladding materials is currently being actively carried out around the world to replace the existing zirconium alloy cladding materials. Compared with traditional cladding materials (such as zirconium alloy and austenitic stainless steel), the performance characteristics of nickel-chromium alloy make it an ideal choice for the fuel cladding material of the new generation of nuclear reactors: under the condition of high-dose neutron irradiation, the alloy exhibits a smaller low-temperature radiation-induced embrittlement effect; in a variety of corrosive media (such as high-temperature water vapor, seawater and other corrosive media), the alloy exhibits more excellent corrosion resistance; in the temperature range of 300℃~400℃ and under the condition of high-dose neutron irradiation, the alloy exhibits more excellent comprehensive mechanical properties; under the conditions of high temperature and long-term service, the alloy still maintains good structural stability.

[0003] With the rapid development of the fourth-generation modular small reactor, there is an urgent need to develop new nickel-chromium alloys with low activation, radiation resistance, corrosion resistance, high strength and toughness, and stable structure, and to master their preparation process to ensure the stability of the material. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a radiation-resistant nickel-chromium alloy for modular reactor cladding in view of the deficiencies of the above-mentioned prior art. The nickel-chromium alloy takes Ni as the matrix, Cr and Mo as the main alloying elements, and Al, Fe, W, Ti, C, and Ce as the secondary added elements to form a stable and uniformly organized single austenite phase, so that the nickel-chromium alloy has excellent comprehensive mechanical properties, corrosion resistance, radiation resistance and processing performance, solving the problem of poor comprehensive mechanical properties and corrosion resistance of traditional cladding alloys.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a radiation-resistant nickel-chromium alloy for modular reactor cladding, characterized in that it is composed of the following elements in mass percentage: Cr 30%~45%, Mo 0.5%~3%, Al 0.1%~0.4%, Fe 0.3%~0.6%, W 0.05%~0.3%, Ti 0.1%~0.25%, C 0.03%~0.2%, Ce 0.01%~0.2%, the balance is Ni and inevitable impurity elements; the mass percentages of the inevitable impurity elements are: Si≤0.25%, Mn≤0.2%, O≤0.05%, S≤0.01%, P≤0.01%; the room temperature tensile yield strength of the nickel-chromium alloy is greater than 600MPa, the tensile strength is greater than 850MPa, the elongation after fracture is greater than 30%, the tensile yield strength at 350℃ is greater than 350MPa, the tensile strength is greater than 650MPa, the elongation after fracture is greater than 20%, and the radiation swelling rate is less than 5%.

[0006] The nickel-chromium alloy of the present invention uses Ni as a matrix, and uses heat-resistant and corrosion-resistant Cr and Mo as main alloying elements. By regulating the contents of the three elements, a single stable γ-austenite structure is formed within a set alloy composition range, that is, a γ-austenite alloy with uniform structure and single phase is obtained, and the Cr and Mo atoms replace the positions of Ni atoms in the original lattice in the form of atomic substitution. The difference in atomic size causes obvious lattice distortion in the local alloy structure, hinders the movement of dislocations, inhibits the slip of dislocations, produces a significant solid solution strengthening effect, and improves the strength of the nickel-chromium alloy. At the same time, the addition of the Cr element reduces the tough-brittle transition temperature of the nickel-chromium alloy after irradiation, and enhances the oxidation resistance and corrosion resistance of the nickel-chromium alloy; the addition of the Mo element improves the high temperature strength and corrosion resistance of the nickel-chromium alloy in liquid, and the addition of the Al element improves the oxidation resistance of the nickel-chromium alloy. In addition, Fe, Ti, and W added to the nickel-chromium alloy of the present invention are all low-activation elements, which ensure that the radioactivity of the nickel-chromium alloy decays rapidly after high-energy neutron irradiation, ensuring that the nickel-chromium alloy has excellent low-activation and radiation resistance properties; the added trace element C precipitates carbides at the grain boundaries, improves the grain boundary strength of the nickel-chromium alloy, and ensures the stable mechanical properties of the nickel-chromium alloy at high temperatures, while the addition of trace Ce elements improves the high-temperature durability of the nickel-chromium alloy. In addition, the present invention also controls the impurity elements in the nickel-chromium alloy to avoid the segregation of harmful elements at the grain boundaries, thereby ensuring the grain boundary strength of the nickel-chromium alloy, ensuring that the nickel-chromium alloy has a stable organizational structure and mechanical properties, and improving the reliability of the nickel-chromium alloy. In summary, the nickel-chromium alloy of the present invention has excellent comprehensive performance and meets the requirements in the complex service environment of modular reactors.

[0007] The above-mentioned radiation-resistant nickel-chromium alloy for modular reactor cladding is characterized in that it is composed of the following elements in mass percentage: Cr 41%~43%, Mo 1.2%~1.7%, Al 0.25%~0.4%, Fe 0.4%~0.5%, W 0.2%~0.25%, Ti0.15%~0.2%, C 0.1%~0.17%, Ce 0.1%~0.15%, and the balance is Ni and inevitable impurity elements; the mass percentage of the inevitable impurities is: Si≤0.2%, Mn≤0.1%, O≤0.02%, S≤0.01%, P≤0.01%.

[0008] In addition, the present invention also discloses a method for preparing the above-mentioned radiation-resistant nickel-chromium alloy for modular reactor cladding, characterized in that the method comprises the following steps: Step 1, material mixing: according to the composition requirements of the target product nickel-chromium alloy, weigh NiCr50 master alloy, NiW42 master alloy, NiMo50 master alloy, metal Ce, electrolytic Ni, sponge titanium, high-purity Fe, metal Al and graphite particles and mix them evenly to obtain an alloy material; Step 2, vacuum smelting: vacuum smelting the alloy material obtained in step 1, and then casting it into an ingot to obtain a nickel-chromium alloy ingot; Step 3: Forging: The nickel-chromium alloy ingot obtained in step 2 is subjected to multiple-fire forging to obtain a forged nickel-chromium alloy ingot; Step 4: heat treatment and cooling: heat treat the forged nickel-chromium alloy ingot obtained in step 3, and obtain the nickel-chromium alloy after cooling.

[0009] The present invention selects high-quality intermediate alloy raw materials with similar melting points, which reduces the difficulty of smelting process on the one hand, ensures the composition stability of nickel-chromium alloy during smelting, and ensures that the impurity content of nickel-chromium alloy is very low and the purity is high on the other hand. In addition, the present invention strictly controls the smelting and subsequent processing of nickel-chromium alloy to ensure that the nickel-chromium alloy has a suitable grain size and a uniform structure without the presence of a second phase, thereby ensuring the final comprehensive performance and reliability of the nickel-chromium alloy.

[0010] The above-mentioned preparation method is characterized in that the composition of the NiCr50 master alloy in step 1 is: Cr 47%~53%, and the balance is Ni and inevitable impurity elements; the composition of the NiW42 master alloy is: W 35%~45%, and the balance is Ni and inevitable impurity elements; the composition of the NiMo50 master alloy is: Mo 45%~50%, and the balance is Ni and inevitable impurity elements; the mass purity of the metal Ce is not less than 99%, the mass purity of the electrolytic Ni is more than 99.5%, the mass purity of the high-purity Fe is more than 99.7%, the mass content of Ti in the sponge titanium is not less than 99.8%, the mass purity of the metal Al is more than 99%, and the mass content of carbon in the graphite particles is more than 99.9%.

[0011] The above-mentioned preparation method is characterized in that the vacuum melting in step 2 is one or more of vacuum consumable arc melting, vacuum induction melting and vacuum suspension melting, the vacuum degree of the vacuum melting is 0.001Pa~0.01Pa, the melting temperature is 1400℃~1800℃, and the melting time is 20min~30min. The present invention avoids contact with air by melting, refining, alloying and casting the metal raw materials under a vacuum environment, thereby preventing oxidation and burning of alloy elements. In addition, vacuum conditions help to remove gases, non-metallic inclusions and harmful metal impurities in the melt, thereby improving the purity and performance of nickel-chromium alloys.

[0012] The above-mentioned preparation method is characterized in that the number of multi-fire forgings in step three is 3 to 5 times, and the specific process is: the nickel-chromium alloy ingot is sent into a heating furnace for heating and insulation, the target temperature of the heating furnace hearth is 900°C to 1100°C, and the insulation time of the nickel-chromium alloy ingot in the heating furnace is controlled to be 60min to 80min. After the nickel-chromium alloy ingot is heated and heat-insulated, it is taken out of the furnace for forging in three different directions, the start forging temperature is above 1050°C, the stop forging temperature is above 900°C, and the deformation amount of each forging is 40% to 50%. The present invention controls the temperature of multi-fire forging so that the nickel-chromium alloy ingot is forged once at a temperature close to the liquidus temperature of the γ phase, thereby ensuring that all alloying elements in the nickel-chromium alloy are completely dissolved into the Ni matrix, and then the temperature is successively reduced by 50°C to 100°C in the γ phase region for subsequent forging deformation, thereby achieving grain crushing and uniform distribution of alloying elements, thereby ensuring the machinability and composition uniformity of the subsequently deformed nickel-chromium alloy, and having optimal organizational uniformity and mechanical properties.

[0013] The above-mentioned preparation method is characterized in that the heat treatment system in step 4 is: keeping warm at 1000°C to 1100°C for 5min to 10min, and the cooling method is water cooling or air cooling. The present invention effectively eliminates the residual stress in the alloy after forging by controlling the temperature and holding time of the heat treatment, and promotes the uniformity of the organization through the dynamic recrystallization of the deformed organization, thereby comprehensively improving the comprehensive performance of the nickel-chromium alloy.

[0014] The modular reactor irradiation environment and related tests involved in the present invention are equivalent to 540keV helium ion room temperature irradiation, and the irradiation injection is 1.0×10 15 Ions / cm 2 ~1.0×10 17 Ions / cm 2 , the corresponding radiation damage dose is 1.0dpa~10dpa; a transparent film is used to block half of the irradiated sample for mask method test, and the evaluation of the radiation swelling rate is tested by atomic force microscopy on the surface fluctuation of the sample. Through the light microscope, multiple clearly visible grain boundaries are found in the irradiated and non-irradiated areas of the sample, and the radiation swelling rate of the sample is calculated using the formula "irradiation swelling rate = (swelling height / irradiation depth) × 100%". The irradiation depth of the sample is calculated using the Monte Carlo particle transport program.

[0015] Compared with the prior art, the present invention has the following advantages: 1. The nickel-chromium alloy of the present invention controls the content of the matrix element Ni and the main alloying elements Cr and Mo to ensure that the nickel-chromium alloy has a single-phase γ-austenite solid solution with uniform structure and single phase within a wide temperature range, forms severe lattice distortion in the nickel-chromium alloy structure, inhibits the slip of dislocations, and achieves a significant solid solution strengthening effect, so that the nickel-chromium not only has excellent mechanical properties and antioxidant and corrosion resistance, but also takes into account the machinability of the γ-austenite phase.

[0016] 2. The nickel-chromium alloy of the present invention ensures that the nickel-chromium alloy has excellent low activation and radiation resistance by adding the secondary low activation elements Fe, Ti, and W, and improves the anti-oxidation ability of the nickel-chromium alloy by adding the Al element; at the same time, by adding trace elements C and Ce, the stable mechanical properties of the nickel-chromium alloy at high temperatures are guaranteed, and the high-temperature durability of the nickel-chromium alloy is improved; in addition, the present invention strictly controls the content of impurity elements to avoid the segregation of harmful elements at the grain boundaries, thereby ensuring the high-temperature strength of the material. Therefore, the nickel-chromium alloy has excellent comprehensive performance and meets the requirements in the complex service environment of the nuclear reactor.

[0017] 3. The present invention adopts a variety of nickel-based master alloys with similar melting points as raw materials, which effectively solves the metallurgical problems such as the burning of low-melting-point elements and the formation of high-melting-point refractory blocks caused by the melting point difference that is easy to occur during the smelting process of adding single metal raw materials, thereby preparing a nickel-chromium alloy ingot with uniform composition and structure, avoiding metallurgical defects such as element segregation and unmelted blocks; in addition, the nickel-based master alloy raw materials used in the present invention are of high quality and low impurity content, ensuring that the prepared nickel-chromium alloy ingot has extremely high purity.

[0018] 4. The preparation method of the present invention adopts a multi-fire forging process, which, on the one hand, ensures the uniformity of the components and microstructure of the nickel-chromium alloy and improves the comprehensive mechanical properties of the nickel-chromium alloy. On the other hand, the grain size of the nickel-chromium alloy is refined by controlling the deformation of the nickel-chromium alloy during the forging process, so that a large number of interfaces in the microstructure become effective traps for radiation defects, thereby absorbing a large number of radiation-induced defects (such as point defects, dislocations and clusters, etc.), significantly improving the radiation resistance of the nickel-chromium alloy.

[0019] 5. The present invention adopts a heat treatment process to effectively eliminate the residual stress in the alloy after forging, and promotes the uniformity of the structure through dynamic recrystallization of the deformed structure, thereby comprehensively improving the comprehensive performance of the nickel-chromium alloy.

[0020] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the phase diagram of the nickel-chromium alloy system of the present invention.

[0022] Figure 2 This is the XRD pattern of the nickel-chromium alloy prepared in Example 1 of the present invention.

[0023] Figure 3 This is a scan image of the nickel-chromium alloy prepared in Example 1 of the present invention.

[0024] Figure 4 This is the distribution diagram of Ni element in the nickel-chromium alloy prepared in Example 1 of the present invention.

[0025] Figure 5 This is the distribution diagram of Cr element in the nickel-chromium alloy prepared in Example 1 of the present invention.

[0026] Figure 6 This is the distribution diagram of Mo element in the nickel-chromium alloy prepared in Example 1 of the present invention.

[0027] Figure 7 This is the distribution diagram of W element in the nickel-chromium alloy prepared in Example 1 of the present invention.

[0028] Figure 8 This is the tensile test curve of the nickel-chromium alloy prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] Figure 1 The nickel-chromium alloy system phase diagram of the present invention is shown in FIG. Figure 1 It can be seen that Cr has a large solid solubility in Ni. In order to ensure the processing performance of nickel-chromium alloy, nickel-chromium alloy should maintain a single γ-austenite phase. Therefore, the mass percentage of Cr in nickel-chromium alloy should not exceed 47.47%; in addition, the processing and heat treatment temperature of nickel-chromium alloy should be set at 1000℃~1200℃.

[0030] Example 1 The radiation-resistant nickel-chromium alloy for modular reactor cladding of the present embodiment is composed of the following elements in percentage by mass: Cr 41%, Mo 1.2%, Al 0.25%, Fe 0.4%, W 0.2%, Ti 0.15%, C 0.1%, Ce 0.1%, and the balance is Ni and unavoidable impurity elements.

[0031] The method for preparing the radiation-resistant nickel-chromium alloy for modular reactor cladding of this embodiment comprises the following steps: Step 1, material mixing: according to the composition requirements of the target product nickel-chromium alloy, weigh NiCr50 master alloy, NiW42 master alloy, NiMo50 master alloy, metal Ce, electrolytic Ni, sponge titanium, high-purity Fe, metal Al and graphite particles and mix them evenly to obtain an alloy material; The composition of the NiCr50 master alloy is: Cr 50%, the balance is Ni and inevitable impurity elements; the composition of the NiW42 master alloy is: W 40%, the balance is Ni and inevitable impurity elements; the composition of the NiMo50 master alloy is: Mo 47%, the balance is Ni and inevitable impurity elements; the mass purity of the metal Ce is not less than 99%, the mass purity of the electrolytic Ni is more than 99.5%, the mass purity of the high-purity Fe is more than 99.7%, the mass content of Ti in the sponge titanium is not less than 99.8%, the mass purity of the metal Al is more than 99%, and the mass content of carbon in the graphite particles is more than 99.9%; Step 2, vacuum melting: placing the alloy material obtained in step 1 in a vacuum suspension induction furnace for vacuum suspension induction melting, the vacuum degree is 0.005 Pa, the melting temperature is 1600° C., the melting time is 25 min, and then casting into an ingot to obtain a nickel-chromium alloy ingot; Step 3, forging: sending the nickel-chromium alloy ingot obtained in step 2 into a heating furnace for heating and heat preservation, the target temperature of the heating furnace hearth is 1000°C, and the insulation time of the nickel-chromium alloy ingot in the heating furnace is controlled to be 70 minutes. After the nickel-chromium alloy ingot is heated and heat-insulated, it is taken out from the furnace for 4 times of forging in three different directions, the start forging temperature is 1150°C, the stop forging temperature is 950°C, and the deformation amount of each forging is 45%, so as to obtain a forged nickel-chromium alloy ingot; Step 4: heat treatment and cooling: subject the forged nickel-chromium alloy ingot obtained in step 3 to a short-time recrystallization heat treatment, keep the temperature at 1050° C. for 8 min, and air-cool to obtain a nickel-chromium alloy.

[0032] The chemical composition of the nickel-chromium alloy prepared in this embodiment was tested, and the results are shown in Table 1 below.

[0033]

[0034] As can be seen from Table 1, the nickel-chromium alloy prepared in this embodiment contains very low levels of impurity elements, especially P and S elements, which avoids affecting the high-temperature grain boundary strength of the nickel-chromium alloy.

[0035] After testing, the room temperature tensile yield strength of the nickel-chromium alloy prepared in this embodiment is 620MPa, the tensile strength is 915MPa, and the elongation after fracture is 36%. Under the condition of 350°C, the tensile yield strength of the alloy material is 450MPa, the tensile strength is 710MPa, the elongation after fracture is 23%, and the radiation swelling rate is 2.6%.

[0036] Figure 2 The XRD pattern of the nickel-chromium alloy prepared in this embodiment is as follows: Figure 2 It can be seen that the nickel-chromium alloy contains the γ phase, which is single and has a uniform structure.

[0037] Figure 3 is a scanning image of the nickel-chromium alloy prepared in this embodiment, Figure 4~Figure 7 They are the distribution diagrams of Ni, Cr, Mo and W in the nickel-chromium alloy prepared in this embodiment, combined with Figure 3 and Figure 4~Figure 7 It can be seen that the Ni, Cr, Mo and W elements in the nickel-chromium alloy are uniformly distributed as a whole, there is no macroscopic segregation of high-density elements, and no infusible blocks of high-melting-point elements are formed.

[0038] Figure 8 This is the tensile test curve of the nickel-chromium alloy prepared in this embodiment. Figure 8 It can be seen that the nickel-chromium alloy has excellent mechanical strength and plasticity both at room temperature and high temperature.

[0039] Example 2 The radiation-resistant nickel-chromium alloy for modular reactor cladding of the present embodiment is composed of the following elements in percentage by mass: Cr 43%, Mo 1.7%, Al 0.4%, Fe 0.5%, W 0.25%, Ti 0.2%, C 0.17%, Ce 0.15%, and the balance is Ni and unavoidable impurity elements.

[0040] The method for preparing the radiation-resistant nickel-chromium alloy for modular reactor cladding of this embodiment comprises the following steps: Step 1, material mixing: according to the composition requirements of the target product nickel-chromium alloy, weigh NiCr50 master alloy, NiW42 master alloy, NiMo50 master alloy, metal Ce, electrolytic Ni, sponge titanium, high-purity Fe, metal Al and graphite particles and mix them evenly to obtain an alloy material; The composition of the NiCr50 master alloy is: Cr 48%, the balance is Ni and inevitable impurity elements; the composition of the NiW42 master alloy is: W 37%, the balance is Ni and inevitable impurity elements; the composition of the NiMo50 master alloy is: Mo 46%, the balance is Ni and inevitable impurity elements; the mass purity of the metal Ce is not less than 99%, the mass purity of the electrolytic Ni is more than 99.5%, the mass purity of the high-purity Fe is more than 99.7%, the mass content of Ti in the sponge titanium is not less than 99.8%, the mass purity of the metal Al is more than 99%, and the mass content of carbon in the graphite particles is more than 99.9%; Step 2, vacuum melting: placing the alloy material obtained in step 1 in a vacuum induction furnace for vacuum induction melting, the vacuum degree is 0.007 Pa, the melting temperature is 1550° C., the melting time is 25 min, and then casting into an ingot to obtain a nickel-chromium alloy ingot; Step 3, forging: sending the nickel-chromium alloy ingot obtained in step 2 into a heating furnace for heating and heat preservation, the target temperature of the heating furnace hearth is 950°C, and the insulation time of the nickel-chromium alloy ingot in the heating furnace is controlled to be 75 minutes. After the nickel-chromium alloy ingot is heated and heat-insulated, it is taken out from the furnace for 4 fire forgings in three different directions, the start forging temperature is 1150°C, the stop forging temperature is 950°C, and the deformation amount of each forging is 45%, so as to obtain the forged nickel-chromium alloy ingot; Step 4: heat treatment and cooling: the forged nickel-chromium alloy ingot obtained in step 3 is subjected to short-time recrystallization heat treatment, kept at 1000° C. for 7 minutes, and air-cooled to obtain a nickel-chromium alloy.

[0041] The chemical composition of the nickel-chromium alloy prepared in this embodiment was tested, and the results are shown in Table 2 below.

[0042]

[0043] As can be seen from Table 2, the nickel-chromium alloy prepared in this embodiment contains very low levels of impurity elements, especially P and S elements, which avoids affecting the high-temperature grain boundary strength of the nickel-chromium alloy.

[0044] After testing, the room temperature tensile yield strength of the nickel-chromium alloy prepared in this embodiment is 605MPa, the tensile strength is 908MPa, and the elongation after fracture is 34%. Under the condition of 350°C, the tensile yield strength of the alloy material is 455MPa, the tensile strength is 686MPa, the elongation after fracture is 23%, and the radiation swelling rate is 2.9%.

[0045] Example 3 The radiation-resistant nickel-chromium alloy for modular reactor cladding of the present embodiment is composed of the following elements in percentage by mass: Cr 30%, Mo 0.5%, Al 0.1%, Fe 0.3%, W 0.05%, Ti 0.1%, C 0.03%, Ce 0.01%, and the balance is Ni and unavoidable impurity elements.

[0046] The method for preparing the radiation-resistant nickel-chromium alloy for modular reactor cladding of this embodiment comprises the following steps: Step 1, material mixing: according to the composition requirements of the target product nickel-chromium alloy, weigh NiCr50 master alloy, NiW42 master alloy, NiMo50 master alloy, metal Ce, electrolytic Ni, sponge titanium, high-purity Fe, metal Al and graphite particles and mix them evenly to obtain an alloy material; The composition of the NiCr50 master alloy is: Cr 47%, the balance is Ni and inevitable impurity elements; the composition of the NiW42 master alloy is: W 35%, the balance is Ni and inevitable impurity elements; the composition of the NiMo50 master alloy is: Mo 45%, the balance is Ni and inevitable impurity elements; the mass purity of the metal Ce is not less than 99%, the mass purity of the electrolytic Ni is more than 99.5%, the mass purity of the high-purity Fe is more than 99.7%, the mass content of Ti in the sponge titanium is not less than 99.8%, the mass purity of the metal Al is more than 99%, and the mass content of carbon in the graphite particles is more than 99.9%; Step 2, vacuum melting: placing the alloy material obtained in step 1 in a vacuum induction furnace for vacuum induction melting, the vacuum degree is 0.01 Pa, the melting temperature is 1400° C., the melting time is 30 min, and then casting into an ingot to obtain a nickel-chromium alloy ingot; Step 3, forging: sending the nickel-chromium alloy ingot obtained in step 2 into a heating furnace for heating and heat preservation, the target temperature of the heating furnace is 900°C, and the insulation time of the nickel-chromium alloy ingot in the heating furnace is controlled to be 80 minutes. After the nickel-chromium alloy ingot is heated and heat-insulated, it is taken out from the furnace for three fire forgings in three different directions, the start forging temperature is 1050°C, the stop forging temperature is 900°C, and the deformation amount of each forging is 40%, so as to obtain a forged nickel-chromium alloy ingot; Step 4: heat treatment and cooling: subject the forged nickel-chromium alloy ingot obtained in step 3 to a short-time recrystallization heat treatment, keep the temperature at 1000° C. for 10 min, and obtain a nickel-chromium alloy after water cooling.

[0047] The chemical composition of the nickel-chromium alloy prepared in this embodiment was tested, and the results are shown in Table 3 below.

[0048]

[0049] It can be seen from Table 3 that the nickel-chromium alloy prepared in this embodiment contains very low impurity elements, especially P and S elements, which avoids affecting the high-temperature grain boundary strength of the nickel-chromium alloy.

[0050] After testing, the room temperature tensile yield strength of the nickel-chromium alloy prepared in this embodiment is 610 MPa, the tensile strength is 872 MPa, and the elongation after fracture is 33%. At 350°C, the tensile yield strength of the alloy material is 352 MPa, the tensile strength is 655 MPa, the elongation after fracture is 21%, and the radiation swelling rate is 3.2%.

[0051] Example 4 The radiation-resistant nickel-chromium alloy for modular reactor cladding of the present embodiment is composed of the following elements in percentage by mass: Cr 45%, Mo 3%, Al 0.4%, Fe 0.6%, W 0.3%, Ti 0.25%, C 0.2%, Ce 0.2%, and the balance is Ni and unavoidable impurity elements.

[0052] The method for preparing the radiation-resistant nickel-chromium alloy for modular reactor cladding of this embodiment comprises the following steps: Step 1, material mixing: according to the composition requirements of the target product nickel-chromium alloy, weigh NiCr50 master alloy, NiW42 master alloy, NiMo50 master alloy, metal Ce, electrolytic Ni, sponge titanium, high-purity Fe, metal Al and graphite particles and mix them evenly to obtain an alloy material; The composition of the NiCr50 master alloy is: Cr 53%, the balance is Ni and inevitable impurity elements; the composition of the NiW42 master alloy is: W 45%, the balance is Ni and inevitable impurity elements; the composition of the NiMo50 master alloy is: Mo 50%, the balance is Ni and inevitable impurity elements; the mass purity of the metal Ce is not less than 99%, the mass purity of the electrolytic Ni is more than 99.5%, the mass purity of the high-purity Fe is more than 99.7%, the mass content of Ti in the sponge titanium is not less than 99.8%, the mass purity of the metal Al is more than 99%, and the mass content of carbon in the graphite particles is more than 99.9%; Step 2, vacuum melting: placing the alloy material obtained in step 1 in a vacuum consumable arc furnace for vacuum consumable arc melting, the vacuum degree is 0.001Pa, the melting temperature is 1800°C, the melting time is 20min, and then casting into an ingot to obtain a nickel-chromium alloy ingot; Step 3, forging: sending the nickel-chromium alloy ingot obtained in step 2 into a heating furnace for heating and heat preservation, the target temperature of the heating furnace hearth is 1100°C, and the insulation time of the nickel-chromium alloy ingot in the heating furnace is controlled to be 60 minutes. After the nickel-chromium alloy ingot is heated and heat-insulated, it is taken out from the furnace for 4 fire forgings in three different directions, the start forging temperature is 1200°C, the stop forging temperature is 1000°C, and the deformation amount of each forging is 50%, so as to obtain a forged nickel-chromium alloy ingot; Step 4: heat treatment and cooling: subject the forged nickel-chromium alloy ingot obtained in step 3 to a short-time recrystallization heat treatment, keep the temperature at 1100° C. for 5 minutes, and obtain the nickel-chromium alloy after air cooling.

[0053] The chemical composition of the nickel-chromium alloy prepared in this embodiment was tested, and the results are shown in Table 4 below.

[0054]

[0055] It can be seen from Table 4 that the nickel-chromium alloy prepared in this embodiment contains very low impurity elements, especially P and S elements, which avoids affecting the high-temperature grain boundary strength of the nickel-chromium alloy.

[0056] After testing, the room temperature tensile yield strength of the nickel-chromium alloy prepared in this embodiment is 630 MPa, the tensile strength is 893 MPa, and the elongation after fracture is 31%. The tensile yield strength of the alloy material at 350°C is 392 MPa, the tensile strength is 689 MPa, the elongation after fracture is 20%, and the radiation swelling rate is 3.6%.

[0057] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

[0058] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. Radiation-resistant nickel-chromium alloy for modular reactor cladding, characterized in that: The nickel-chromium alloy is composed of the following elements in mass percentage: Cr 30%-45%, Mo 0.5%-3%, Al 0.1%-0.4%, Fe 0.3%-0.6%, W 0.05%-0.3%, Ti 0.1%-0.25%, C 0.03%-0.2%, Ce 0.01%-0.2%, and the balance is Ni and inevitable impurity elements; the mass percentage of the inevitable impurity elements is: Si≤0.25%, Mn≤0.2%, O≤0.05%, S≤0.01%, P≤0.01%; the room temperature tensile yield strength of the nickel-chromium alloy is greater than 600MPa, the tensile strength is greater than 850MPa, and the elongation after fracture is greater than 30%, the tensile yield strength at 350°C is greater than 350MPa, the tensile strength is greater than 650MPa, the elongation after fracture is greater than 20%, and the radiation swelling rate is less than 5%.

2. The radiation-resistant nickel-chromium alloy for modular reactor cladding according to claim 1, characterized in that: The following elements are present in percentage by mass Composition: Cr 41%~43%, Mo 1.2%~1.7%, Al 0.25%~0.4%, Fe 0.4%~0.5%, W 0.2%~0.25%, Ti 0.15%~0.2%, C 0.1%~0.17%, Ce 0.1%~0.15%, the balance is Ni and inevitable impurity elements; the mass percentage of the inevitable impurities is: Si≤0.2%, Mn≤0.1%, O≤0.02%, S≤0.01%, P≤0.01%.

3. A method for preparing the radiation-resistant nickel-chromium alloy for modular reactor cladding according to claim 1 or 2, characterized in that: The method comprises the following steps: Step 1, material mixing: according to the composition requirements of the target product nickel-chromium alloy, weigh NiCr50 master alloy, NiW42 master alloy, NiMo50 master alloy, metal Ce, electrolytic Ni, sponge titanium, high-purity Fe, metal Al and graphite particles and mix them evenly to obtain an alloy material; Step 2, vacuum smelting: vacuum smelting the alloy material obtained in step 1, and then casting it into an ingot to obtain a nickel-chromium alloy ingot; Step 3: Forging: The nickel-chromium alloy ingot obtained in step 2 is subjected to multiple-fire forging to obtain a forged nickel-chromium alloy ingot; Step 4: heat treatment and cooling: heat treat the forged nickel-chromium alloy ingot obtained in step 3, and obtain the nickel-chromium alloy after cooling.

4. The preparation method according to claim 3, characterized in that: The composition of the NiCr50 master alloy in step 1 is: Cr 47%~53%, and the balance is Ni and inevitable impurity elements; the composition of the NiW42 master alloy is: W 35%~45%, and the balance is Ni and inevitable impurity elements; the composition of the NiMo50 master alloy is: Mo 45%~50%, and the balance is Ni and inevitable impurity elements; the mass purity of the metal Ce is not less than 99%, the mass purity of the electrolytic Ni is more than 99.5%, the mass purity of the high-purity Fe is more than 99.7%, the mass content of Ti in the sponge titanium is not less than 99.8%, the mass purity of the metal Al is more than 99%, and the mass content of carbon in the graphite particles is more than 99.9%.

5. The preparation method according to claim 3, characterized in that: The vacuum melting in step 2 is one or more of vacuum consumable arc melting, vacuum induction melting and vacuum suspension melting. The vacuum degree of the vacuum melting is 0.001Pa~0.01Pa, the melting temperature is 1400℃~1800℃, and the melting time is 20min~30min.

6. The preparation method according to claim 3, characterized in that: The number of multi-fire forgings described in step three is 3 to 5 times, and the specific process is: the nickel-chromium alloy ingot is sent into a heating furnace for heating and insulation, the target temperature of the heating furnace hearth is 900°C to 1100°C, and the insulation time of the nickel-chromium alloy ingot in the heating furnace is controlled to be 60min to 80min. After the nickel-chromium alloy ingot is heated and insulated, it is taken out of the furnace for forging in three different directions, the start forging temperature is above 1050°C, the stop forging temperature is above 900°C, and the deformation of each forging is 40% to 50%.

7. The preparation method according to claim 3, characterized in that: The heat treatment system in step 4 is: keeping warm at 1000°C~1100°C for 5min~10min, and the cooling method is water cooling or air cooling.

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