FeCrAl-based ODS alloy material for accident-resistant fuel element and preparation method of FeCrAl-based ODS alloy material

Abstract

The invention provides a FeCrAl-based ODS alloy material for accident-resistant fuel elements, which comprises the following components in percentage by mass: 9.0 to 11.5 percent of Cr, 1.5 to 2.5 percent of W, 3.0 to 4.0 percent of Al, 0.6 to 1.5 percent of Ta, 0.9 to 1.5 percent of Si, 0.25 to 0.5 percent of Y2O3, less than or equal to 0.008 percent of C, less than or equal to 0.008 percent of N and the balance of iron and inevitable impurities. The invention further provides a preparation method of the FeCrAl-based ODS alloy material for the accident-resistant fuel element. According to the FeCrAl-based ODS alloy material for the accident-resistant fuel element and the preparation method of the FeCrAl-based ODS alloy material, the FeCrAl-based ODS alloy material has excellent high-temperature oxidation performance under the 1000-DEG C water vapor condition, has high high-temperature strength and structure thermal stability at the high temperature of 800 DEG C and has excellent mechanical strength and plasticity at the room temperature.

Description

Technical Field

[0001] The invention relates to the technical field of iron-based alloy structural materials, and in particular to a FeCrAl-based ODS alloy material for accident-resistant fuel elements and a preparation method thereof. Background Art

[0002] Nuclear fuel elements are the core components of the reactor. They are not only the energy source of the reactor, but also the first safety barrier to contain radioactive fission products. Their performance is an important guarantee for the advancement, safety and reliability of the reactor. The international nuclear fuel professional field has proposed the design of accident-tolerant fuel elements (ATF), which requires that the accident-tolerant fuel cladding material must have better resistance to high-temperature water vapor oxidation than the existing zirconium alloy cladding. Studies have shown that FeCrAl-based alloys with appropriate Cr and Al contents have excellent resistance to high-temperature water vapor oxidation and corrosion resistance, and are very promising candidate materials for ATF cladding materials.

[0003] At present, most commercial FeCrAl-based alloy materials have high Cr and Al contents (Cr: 15-30%, Al: 5-15%). Although a higher Al content can improve the high-temperature oxidation resistance of FeCrAl alloys, its adverse effect is that it significantly reduces the toughness and plasticity of FeCrAl alloys. In addition, higher Cr and Al contents also make FeCrAl alloys more susceptible to aging hardening and radiation embrittlement under irradiation and high-temperature environments, posing a major safety hazard to reactor operation. In order to ensure the safety and reliability of accident-resistant fuel elements under high temperature and irradiation conditions in the reactor, the high-temperature mechanical strength and toughness and plasticity of existing FeCrAl alloys still cannot fully meet the requirements of ATF fuel elements.

[0004] Therefore, improving the high-temperature mechanical strength and toughness and ductility of FeCrAl alloy while ensuring its excellent high-temperature oxidation performance is a key technical issue in the development of FeCrAl alloy for accident-resistant fuel elements. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a FeCrAl-based ODS alloy material for accident-resistant fuel elements, which has excellent high-temperature oxidation performance under 1000°C water vapor conditions, high high-temperature strength and structural thermal stability at 800°C, and excellent mechanical strength and plasticity at room temperature, and a preparation method thereof.

[0006] In order to solve the above technical problems, the present invention provides a FeCrAl-based ODS alloy material for accident-resistant fuel elements, wherein the components and contents thereof include, by mass percentage, Cr 9.0-11.5%, W 1.5-2.5%, Al 3.0-4.0%, Ta 0.6-1.5%, Si 0.9-1.5%, Y2O3 0.25-0.5%, C ≤ 0.008%, N ≤ 0.008%, and the balance is iron and unavoidable impurities.

[0007] 2. The FeCrAl-based ODS alloy material for accident-resistant fuel elements according to claim 1, characterized in that the sum of the mass percentages of Cr and Al is not less than 13%, and the weight percentages of W and Ta are not less than 2.0%.

[0008] The present invention also provides a method for preparing a FeCrAl-based ODS alloy material for an accident-resistant fuel element, comprising the following steps:

[0009] In terms of mass percentage, the components and contents include: Cr 9.0-11.5%, W 1.5-2.5%, Al 3.0-4.0%, Ta 0.6-1.5%, Si 0.9-1.5%, Y2O3 0.25-0.5%, C≤0.008%, N≤0.008%, and the balance is iron and unavoidable impurities. The raw materials are provided with a sum of the mass percentage content of Cr and Al not less than 13%, and the weight percentage content of W and Ta not less than 2.0%;

[0010] The Cr, W, Al, Ta, Si and Fe in the raw materials are melted and cast to obtain a master alloy ingot;

[0011] The master alloy ingot is remelted and then atomized to obtain alloy powder;

[0012] The alloy powder and Y2O3 powder are subjected to ball milling alloying treatment to obtain mechanical alloying powder;

[0013] The mechanically alloyed powder is sealed in a steel ladle and hot isostatically pressed to obtain a FeCrAl-based alloy material.

[0014] Furthermore, the iron is industrial pure iron, the purity of Cr, W, Al, Ta and Si is above 99.9%, the particle size of the Y2O3 powder is less than 30nm, and the purity is greater than 99.99%.

[0015] Furthermore, the Cr, W, Al, Ta, Si and Fe are melted in a vacuum induction melting furnace. Before melting, the melting chamber of the vacuum induction melting furnace is evacuated to below 10 Pa and then filled with argon until the pressure reaches atmospheric pressure.

[0016] Furthermore, the smelting temperature is 1500°C to 1600°C, the smelting time is 0.5 to 1.5 hours, the pouring temperature is 1400°C to 1600°C, and the remelting temperature of the master alloy ingot is 1500°C to 1600°C.

[0017] Furthermore, the master alloy molten liquid formed after remelting the master alloy ingot is impacted with argon gas with a pressure range of 7.0 to 7.5 MPa to form master alloy droplets, and the master alloy droplets are cooled in a cooling chamber to form alloy powder with a particle size less than 200 mesh.

[0018] Furthermore, the ball-to-material ratio of the alloy powder and the Y2O3 powder during ball milling is 5:1-15:1, the main disc speed of the ball mill is 200-300 r / min, and the ball milling time is 40-60 h.

[0019] Furthermore, the mechanical alloying powder is sealed in a steel bag and the vacuum degree of degassing is 10 -4 Pa.

[0020] Furthermore, the hot isostatic pressing sintering pressure is 100-200 MPa, the sintering temperature is 1100-1150° C., and the holding time is 2-3 hours.

[0021] The invention provides a FeCrAl-based ODS alloy material for accident-resistant fuel elements and a preparation method thereof. Based on the alloy dispersion strengthening principle, by selecting elements such as Cr, Al, W, Ta, Si and Y2O3 and optimizing the element content, powder metallurgy, mechanical alloying, hot isostatic pressing and other processing techniques and optimizing the processing parameters, the prepared FeCrAl-based ODS alloy material for accident-resistant fuel elements has both excellent high-temperature oxidation resistance and high-temperature mechanical properties. It has excellent high-temperature oxidation resistance under 1000°C water vapor conditions, and its high-temperature steam oxidation rate under 1000°C water vapor conditions is much lower than that of the currently commercial nuclear power cladding material Zr-4 alloy. In addition, the present invention provides a method for preparing a FeCrAl-based ODS alloy material for an accident-resistant fuel element, which obtains uniformly distributed fine dispersed oxide particles after processing techniques such as mechanical alloying, hot isostatic pressing and sintering and optimization and control of processing process parameters, significantly improving the mechanical properties of the alloy, having high high-temperature strength and thermal stability of the structure at a high temperature of 800°C, and also having high mechanical strength and suitable processing plasticity at room temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A flow chart of a method for preparing a FeCrAl-based ODS alloy material for an accident-resistant fuel element provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] An FeCrAl-based ODS alloy material for accident-resistant fuel elements provided in an embodiment of the present invention comprises, by mass percentage, Cr 9.0-11.5%, W 1.5-2.5%, Al 3.0-4.0%, Ta 0.6-1.5%, Si 0.9-1.5%, Y2O3 0.25-0.5%, C≤0.008%, N≤0.008%, and the remainder is iron and unavoidable impurities. The content of unavoidable impurities meets the standards of current commercial industrial pure iron and ferritic stainless steel.

[0024] Among them, the FeCrAl-based ODS alloy material for accident-resistant fuel elements provided by the present invention not only controls the mass percentage content of Cr to 9.0-11.5%, and the mass percentage content of Al to 3.0-4.0%, but also controls the sum of the mass percentage contents of Cr and Al to no less than 13%, so that the FeCrAl-based ODS alloy material can maintain good high-temperature oxidation performance and corrosion resistance.

[0025] Furthermore, the present invention adds 0.9% to 1.5% Si to the FeCrAl-based ODS alloy material, which is beneficial to the combination of the FeCrAl-based ODS alloy material with Y and O atoms during the hot isostatic pressing sintering process, forming Y-Si-O oxide particles with a particle size of less than 100 nm and uniform dispersion, thereby improving the room temperature and high temperature mechanical properties of the alloy.

[0026] At the same time, the present invention adds 0.6-1.5% Ta to the FeCrAl-based ODS alloy material and controls the weight percentage content of W and Ta to no less than 2.0%, which can increase the lattice distortion of the FeCrAl-based ODS alloy, achieve the purpose of solid solution strengthening, and further improve the room temperature mechanical properties and high temperature strength of the alloy.

[0027] See also Figure 1 The present invention provides a method for preparing a FeCrAl-based ODS alloy material for an accident-resistant fuel element, comprising the following steps:

[0028] Step 1) In terms of mass percentage, the components and contents include: Cr 9.0-11.5%, W 1.5-2.5%, Al 3.0-4.0%, Ta 0.6-1.5%, Si 0.9-1.5%, Y2O3 0.25-0.5%, C≤0.008%, N≤0.008%, and the balance is iron and unavoidable impurities. Raw materials are prepared, and the sum of the mass percentage contents of Cr and Al in the prepared raw materials is not less than 13%, and the weight percentage contents of W and Ta are not less than 2.0%.

[0029] The iron is industrial pure iron, the purity of Cr, W, Al, Ta and Si is above 99.9%, the particle size of the Y2O3 powder is less than 30nm, and the purity is greater than 99.99%.

[0030] Step 2) Cr, W, Al, Ta, Si and Fe in the raw materials are melted and cast to obtain a master alloy ingot.

[0031] Among them, Cr, W, Al, Ta, Si and Fe are melted in a vacuum induction melting furnace. Before melting, the melting chamber of the vacuum induction melting furnace is evacuated to below 10Pa, and then filled with argon gas until the pressure reaches atmospheric pressure.

[0032] Among them, the smelting temperature is controlled at 1500°C ~ 1600°C, and the smelting time is controlled at 0.5 ~ 1.5h.

[0033] As an optimal specific implementation mode of the present invention, the smelting temperature is controlled at 1550°C and the smelting time is controlled at 1h.

[0034] Among them, the pouring temperature is controlled at 1400℃~1600℃.

[0035] As a best specific implementation manner of the present invention, the pouring temperature is controlled at 1500°C.

[0036] Step 3) The master alloy ingot is remelted and then atomized to obtain alloy powder.

[0037] Among them, the remelting temperature of the master alloy ingot is controlled at 1500℃~1600℃.

[0038] As an optimal specific embodiment of the present invention, the remelting temperature of the master alloy ingot is controlled to be 1550°C.

[0039] The master alloy molten liquid formed after remelting the master alloy ingot is impacted with argon gas with a pressure range of 7.0-7.5 MPa to form master alloy droplets, and the master alloy droplets are cooled in a cooling chamber to form alloy powder with a particle size less than 200 mesh.

[0040] Step 4) The alloy powder and Y2O3 powder are subjected to ball milling alloying treatment to obtain mechanically alloyed powder.

[0041] The alloy powder and the Y2O3 powder are ball milled in a ball mill. The ball-to-material ratio of the alloy powder to the Y2O3 powder is 5:1 to 15:1, the main disc speed of the ball mill is 200 to 300 r / min, and the ball milling time is 40 to 60 h.

[0042] As an optimal specific implementation mode of the present invention, the ball-to-material ratio of alloy powder to Y2O3 powder during ball milling is controlled to be 10:1, the main disc speed of the ball mill is controlled to be 260r / min, and the ball milling time is controlled to be 50h.

[0043] Step 5) The mechanically alloyed powder is sealed in a steel ladle and hot isostatically pressed to obtain a FeCrAl-based alloy material.

[0044] Among them, after the mechanical alloying powder is sealed in the steel bag, the steel bag is first evacuated to remove the air in the bag, and then the bag is evacuated to a vacuum degree of 10 -4 Pa.

[0045] Then, the mechanical alloying powder in the steel jacket is subjected to high temperature sintering to densify the mechanical alloying powder, wherein the hot isostatic pressing sintering pressure is controlled at 100-200 MPa, the sintering temperature is controlled at 1100-1150° C., and the holding time is controlled at 2-3 hours.

[0046] The following is a specific description of the preparation method of the FeCrAl-based ODS alloy material for accident-resistant fuel elements provided by the present invention through examples.

[0047] Example 1

[0048] (1) Use industrial pure iron and high-purity alloy with a purity greater than 99.9% according to the formula shown in Table 1.

[0049] (2) Fe, Cr, Al, W, Ta, and Si are melted in a vacuum induction melting furnace. Before melting, the melting chamber is evacuated to reduce the pressure to 10 Pa, and then high-purity argon is filled into the melting chamber. When the pressure reaches atmospheric pressure, the argon filling is stopped. Melt at 1550°C for 1 hour, and pour when the charge is melted. The pouring temperature is 1500°C. After melting and pouring, a master alloy ingot is obtained.

[0050] (3) The master alloy ingot is remelted at 1550°C, and the master alloy melt is ejected from the nozzle, and under the impact of high-speed argon gas at a pressure of 7.25 MPa, tiny master alloy droplets are formed. The master alloy droplets are rapidly cooled in the cooling chamber to form spherical alloy powders with a particle size of less than 200 mesh.

[0051] (4) The alloy powder and nano Y2O3 powder (the particle size of Y2O3 powder is less than 30nm and the purity is greater than 99.99%) are subjected to mechanical alloying treatment by ball milling. Ball milling method: dry milling, ball milling time: 50h, main disc speed 260 rpm, ball to material ratio: 10:1.

[0052] (5) After ball milling, the ball milled powder is sealed in a steel bag and sintered and densified by hot isostatic pressing. The hot isostatic pressing process is as follows: pressure 150 MPa, sintering temperature 1125 ° C, and holding time 2.5 h; FeCrAl-based ODS alloy material is obtained after hot isostatic pressing and sintering.

[0053] The mechanical properties and high-temperature oxidation properties of the FeCrAl-based ODS alloy material for accident-resistant fuel elements prepared in the embodiment of the present invention at different temperatures are shown in Table 2.

[0054] Table 1

[0055]

[0056] Table 2

[0057]

[0058]

[0059] Example 2

[0060] (1) Use industrial pure iron and high-purity alloy with a purity greater than 99.9% according to the formula shown in Table 1.

[0061] (2) Fe, Cr, Al, W, Ta, and Si are melted in a vacuum induction melting furnace. Before melting, the melting chamber is evacuated to reduce the pressure to 10 Pa, and then high-purity argon is filled into the melting chamber. When the pressure reaches atmospheric pressure, the argon filling is stopped. Melt at 1500°C for 1.5 hours, and pour when the charge is melted. The pouring temperature is 1600°C. After melting and pouring, a master alloy ingot is obtained.

[0062] (3) The master alloy ingot is remelted at 1500°C, and the master alloy melt is ejected from the nozzle, and under the impact of high-speed argon gas at a pressure of 7.5 MPa, tiny master alloy droplets are formed. The master alloy droplets are rapidly cooled in the cooling chamber to form spherical alloy powders with a particle size of less than 200 mesh.

[0063] (4) The alloy powder and nano Y2O3 powder (the particle size of Y2O3 powder is less than 30nm and the purity is greater than 99.99%) are subjected to mechanical alloying treatment by ball milling. Ball milling method: dry milling, ball milling time: 40h, main disc speed 300 rpm, ball to material ratio: 5:1.

[0064] (5) After ball milling, the ball milled powder is sealed in a steel bag and sintered and densified by hot isostatic pressing. The hot isostatic pressing process is as follows: pressure 200 MPa, sintering temperature 1100 ° C, and holding time 3 h; FeCrAl-based ODS alloy material is obtained after hot isostatic pressing and sintering.

[0065] The mechanical properties and high-temperature oxidation properties of the FeCrAl-based ODS alloy material for accident-resistant fuel elements prepared in the embodiment of the present invention at different temperatures are shown in Table 2.

[0066] Example 3

[0067] (1) Use industrial pure iron and high-purity alloy with a purity greater than 99.9% according to the formula shown in Table 1.

[0068] (2) Fe, Cr, Al, W, Ta, and Si are melted in a vacuum induction melting furnace. Before melting, the melting chamber is evacuated to reduce the pressure to 10 Pa, and then high-purity argon is filled into the melting chamber. When the pressure reaches atmospheric pressure, the argon filling is stopped. Melt at 1600°C for 0.5h, and pour when the charge is melted. The pouring temperature is 1400°C. After melting and pouring, a master alloy ingot is obtained.

[0069] (3) The master alloy ingot is remelted at 1500°C-1600°C, and the master alloy melt is ejected from the nozzle and forms tiny master alloy droplets under the impact of high-speed argon gas at a pressure of 7.0 MPa. The master alloy droplets are rapidly cooled in the cooling chamber to form spherical alloy powders with a particle size of less than 200 mesh.

[0070] (4) The alloy powder and nano Y2O3 powder (the particle size of Y2O3 powder is less than 30nm and the purity is greater than 99.99%) are subjected to mechanical alloying treatment by ball milling. Ball milling method: dry milling, ball milling time: 60h, main disc speed 200 rpm, ball to material ratio: 15:1.

[0071] (5) After ball milling, the ball milled powder is sealed in a steel bag and sintered and densified by hot isostatic pressing. The hot isostatic pressing process is as follows: pressure 100 MPa, sintering temperature 1150 ° C, and holding time 2 h; FeCrAl-based ODS alloy material is obtained after hot isostatic pressing and sintering.

[0072] The mechanical properties and high-temperature oxidation properties of the FeCrAl-based ODS alloy material for accident-resistant fuel elements prepared in the embodiment of the present invention at different temperatures are shown in Table 2.

[0073] It can be seen from Table 2 that the FeCrAl-based ODS alloy materials for accident-resistant fuel elements prepared in Examples 1-3 of the present invention have excellent room temperature and high temperature tensile mechanical properties, high tensile strength and good elongation. After 5h and 10h oxidation, the FeCrAl-based ODS alloy materials for accident-resistant fuel elements prepared in Examples 1-3 of the present invention have low oxidation weight gain values. In addition, the FeCrAl-based ODS alloy materials for accident-resistant fuel elements prepared in Examples 1-3 of the present invention also have strong antioxidant properties in a high-temperature water vapor environment.

[0074] Therefore, the preparation method of FeCrAl-based ODS alloy material for accident-resistant fuel elements provided by the present invention optimizes the alloy elements and their contents and optimizes the processing technology and process parameters, so that the prepared FeCrAl-based ODS alloy material for accident-resistant fuel elements has both excellent high-temperature oxidation resistance and high-temperature mechanical properties. It has excellent high-temperature oxidation performance under 1000°C water vapor conditions, has high high-temperature strength and thermal stability of the alloy at 800°C, and has high mechanical strength and suitable processing plasticity at room temperature.

[0075] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A FeCrAl-based ODS alloy material for accident-resistant fuel elements, characterized in that: Calculated by mass percentage, the components and contents include: Cr 9.0-11.5%, W 1.5-2.5%, Al 3.0-4.0%, Ta 0.6-1.5%, Si 0.9-1.5%, Y2O3 0.25-0.5%, C≤0.008%, N≤0.008%, and the balance is iron and unavoidable impurities.

2. The FeCrAl-based ODS alloy material for accident-resistant fuel elements according to claim 1, characterized in that: The sum of the mass percentage contents of Cr and Al is not less than 13%, and the weight percentage contents of W and Ta are not less than 2.0%.

3. A method for preparing the FeCrAl-based ODS alloy material for accident-resistant fuel elements according to claim 1 or 2, characterized in that: The steps include: Prepare the raw materials according to the components and contents of claim 1 or 2; The Cr, W, Al, Ta, Si and Fe in the raw materials are melted and cast to obtain a master alloy ingot; The master alloy ingot is remelted and then atomized to obtain alloy powder; The alloy powder and Y2O3 powder are subjected to ball milling alloying treatment to obtain mechanical alloying powder; The mechanically alloyed powder is sealed in a steel ladle and hot isostatically pressed to obtain a FeCrAl-based alloy material.

4. The method for preparing the FeCrAl-based ODS alloy material for accident-resistant fuel elements according to claim 3, characterized in that: The iron is industrial pure iron, the purity of Cr, W, Al, Ta and Si is above 99.9%, the particle size of the Y2O3 powder is less than 30nm, and the purity is greater than 99.99%.

5. The method for preparing the FeCrAl-based ODS alloy material for accident-resistant fuel elements according to claim 3, characterized in that: The Cr, W, Al, Ta, Si and Fe are melted in a vacuum induction melting furnace. Before melting, the melting chamber of the vacuum induction melting furnace is evacuated to below 10 Pa and then filled with argon until the pressure reaches atmospheric pressure.

6. The method for preparing the FeCrAl-based ODS alloy material for accident-resistant fuel elements according to claim 5, characterized in that: The smelting temperature is 1500°C to 1600°C, the smelting time is 0.5 to 1.5 hours, the pouring temperature is 1400°C to 1600°C, and the remelting temperature of the master alloy ingot is 1500°C to 1600°C.

7. The method for preparing the FeCrAl-based ODS alloy material for accident-resistant fuel elements according to claim 3, characterized in that: The master alloy molten liquid formed after remelting the master alloy ingot is impacted with argon gas with a pressure range of 7.0-7.5 MPa to form master alloy droplets, and the master alloy droplets are cooled in a cooling chamber to form alloy powder with a particle size less than 200 meshes.

8. The method for preparing the FeCrAl-based ODS alloy material for accident-resistant fuel elements according to claim 3, characterized in that: The ball-to-material ratio of the alloy powder to the Y2O3 powder during ball milling is 5:1-15:1, the main disc speed of the ball mill is 200-300 r / min, and the ball milling time is 40-60 hours.

9. The method for preparing the FeCrAl-based ODS alloy material for accident-resistant fuel elements according to claim 3, characterized in that: The mechanical alloying powder is sealed in a steel bag and the vacuum degree of degassing is 10 -4 Pa.

10. The method for preparing the FeCrAl-based ODS alloy material for accident-resistant fuel elements according to claim 3, characterized in that: The hot isostatic pressing sintering pressure is 100-200 MPa, the sintering temperature is 1100-1150° C., and the heat preservation time is 2-3 hours.

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