High-performance ferrite / martensite double-phase ODS steel and preparation method thereof

Abstract

The invention relates to high-performance ferrite / martensite dual-phase ODS steel and a preparation method thereof, and belongs to the technical field of ferrite / martensite dual-phase steel, and the high-performance ferrite / martensite dual-phase ODS steel comprises the following components in percentage by weight: 0.06-0.1% of C, 8.5-9.5% of Cr, 0-4% of W, 0-4% of Mn, 0.5-2.5% of Al, 0.5-2.5% of Si, 0-1.1% of nano oxide particles and the balance of Fe. The balance is Fe and inevitable impurity elements; al, Si and nano oxide particles are added on the basis of preparing 9CrWMn stainless steel, the content of C is controlled, formation of a Cr2O3 protective layer is promoted, formation of a coarse second phase is avoided while the morphology of a matrix structure is regulated and controlled, and the ferrite / martensite double-phase ODS steel resistant to high-temperature oxidation, resistant to LBE corrosion and high in tensile strength is prepared; and meanwhile, the ferrite / martensite double-phase ODS steel has excellent radiation resistance and excellent comprehensive performance.

Description

Technical Field

[0001] The present invention relates to the technical field of ferrite / martensite dual-phase steel, and in particular to a high-performance ferrite / martensite dual-phase ODS steel and a preparation method thereof. Background Art

[0002] Ferrite / martensite dual-phase oxide dispersion-strengthened (ODS) steels are currently widely used in applications such as fourth-generation nuclear reactors, often as fuel cladding materials for pressurized water reactors (PWRs), lead-cooled fast reactors (LFRs), and very high-temperature reactors (UHRTs). Compared to traditional ferritic and austenitic stainless steels, the martensite in the matrix reduces helium bubble coarsening and radiation swelling, resulting in excellent radiation resistance. Furthermore, nano-oxide particles (typically Y2O3), which are stable at high temperatures, are dispersed throughout the alloy matrix, imparting improved high-temperature mechanical properties and radiation resistance. Therefore, this alloy is expected to meet the high-performance requirements of nuclear reactor materials, attracting widespread attention and promising future development.

[0003] Ferrite / martensite duplex ODS steels contain a relatively low Cr content, typically around 9 wt.%, making it difficult to form a dense, anti-oxidation protective layer at high temperatures. This layer is unable to prevent the diffusion of liquid lead-bismuth eutectic (LBE) and oxygen ions into the alloy matrix, as well as the outward diffusion of matrix metal ions. This results in the alloy's poor resistance to oxidative corrosion. Al and Si have a high affinity for oxygen, and adding high levels of these elements to the alloy forms an anti-oxidation protective film, improving the alloy's resistance to oxidative corrosion. However, adding high Al levels inhibits martensite formation, while high Si levels degrade the alloy's mechanical properties. Therefore, the addition of either Si or Al alone cannot simultaneously improve the overall performance of 9Cr ODS steel.

[0004] The current ferrite / martensite dual-phase ODS steel faces the problems of poor oxidation corrosion resistance and mechanical properties. Summary of the Invention

[0005] In view of the above problems, the present invention provides a high-performance ferrite / martensite duplex ODS steel and a preparation method thereof. On the basis of preparing 9CrWMn stainless steel, Al, Si and nano-oxide particles are added simultaneously, and the C content is controlled to prepare a ferrite / martensite duplex ODS steel with resistance to high-temperature oxidation, LBE corrosion and high tensile strength (900-1200MPa). At the same time, the ferrite / martensite duplex ODS steel has excellent radiation resistance and excellent comprehensive performance.

[0006] One object of the present invention is to provide a high-performance ferrite / martensite dual-phase ODS steel, wherein the high-performance ferrite / martensite dual-phase ODS steel comprises, by weight percentage, C: 0.06-0.1%; Cr: 8.5-9.5%; W: 0-4%; Mn: 0-4%; Al: 0.5-2.5%; Si: 0.5-2.5%; nano-oxide particles: 0-1.1%; and the remainder is Fe and unavoidable impurity elements.

[0007] Further, the nano-oxide particles include Y2O3, Y-Ti-O, Y-Zr-O and / or Y-Hf-O;

[0008] Furthermore, the Y-Ti-O includes Y2TiO5 and / or Y2Ti2O7; the Y-Zr-O includes Y4Zr3O 12 , the Y-Hf-O includes Y2Hf2O7;

[0009] The present invention simultaneously adds appropriate amounts of Al and Si to the 9CrWMn stainless steel. Al and Si preferentially react with inwardly diffusing O, preventing Cr oxidation within the ODS alloy matrix. This promotes the outward conversion of Cr ions and further facilitates the formation of a Cr2O3 protective film on the matrix surface. The Cr2O3 protective film hinders the inward diffusion of O ions, lead, and bismuth, as well as the outward diffusion of ODS alloy matrix ions, thereby improving the oxidation resistance and corrosion resistance of the ferrite / martensite duplex ODS steel at temperatures between 300 and 1000°C.

[0010] Another object of the present invention is to provide a method for preparing high-performance ferrite / martensite dual-phase ODS steel, comprising:

[0011] Step 1: Mixing a certain amount of nano-oxide particles and metal powder; mechanically alloying the nano-oxide particles and metal powder to obtain ODS alloyed powder;

[0012] Step 2: Sintering the ODS alloying powder to obtain a bulk ODS alloy;

[0013] Step 3, heat treating the sintered bulk ODS alloy to obtain high-performance ferrite / martensite dual-phase ODS steel;

[0014] Preferably, the nano-oxide particles in step 1 are Y2O3, Y-Ti-O, Y-Zr-O and / or Y-Hf-O; and the nano-oxide is prepared by a sol-gel or precipitation method.

[0015] The invention adopts a sol-gel or precipitation method to prepare nano oxide particles. The process is simple and efficient, and the prepared nano oxide particles are small in size and free of agglomeration.

[0016] Preferably, Y-Ti-O includes Y2TiO5 and / or Y2Ti2O7; the Y-Zr-O includes Y4Zr3O 12 ; The Y-Hf-O includes Y2Hf2O7;

[0017] Preferably, the metal powder in step 1 is a simple powder or a pre-alloyed powder; the pre-alloyed powder is prepared by gas atomization or rotating electrode atomization;

[0018] Preferably, the metal powder in step 1 comprises: by weight percentage, C: 0.06-0.1%; Cr: 8.5-9.5%; W: 0-4%; Mn: 0-4%; Al: 0.5-2.5%; Si: 0.5-2.5%;

[0019] Preferably, the mechanical alloying time in step 1 is 10-100 hours, and the rotation speed is 150-800 rpm;

[0020] Preferably, the sintering in step 2 includes hot isostatic pressing, hot pressing or hot extrusion;

[0021] Furthermore, the hot isostatic pressing sintering temperature is: 1130-1170°C, the pressure is 120-170 MPa; and the sintering time is 1-4 hours;

[0022] The present invention uses hot isostatic pressing, hot pressing or hot extrusion processes to form a bulk ODS alloy with high density, while maintaining a small matrix grain size, a small composite oxide particle size and excellent comprehensive performance.

[0023] Preferably, the heat treatment temperature in step 3 is 780-1170° C. and the time is 30-200 min;

[0024] The present invention performs heat treatment on the sintered bulk ODS alloy at 780-1170° C. to ensure complete austenitization and forms martensite during the quenching process.

[0025] The invention adds 0.5-2.5% by weight of aluminum. During high-temperature oxidation at 600-1000°C and LBE corrosion at 300-800°C, Al forms an Al2O3 protective layer on the surface of the ODS alloy matrix, thereby enhancing oxidation corrosion resistance.

[0026] The present invention adds 0.5-2.5% silicon by weight on the basis of adding Al, which can ensure that the alloy is a ferrite-martensite dual-phase steel and has good corrosion resistance, further improving the material's resistance to high-temperature oxidation corrosion without deteriorating the mechanical properties and radiation resistance of ODS steel.

[0027] The invention adds 0.06-0.1 weight percent carbon, ensures that the dual-phase steel can form 5-60% austenite phase after heat treatment, and reduces the influence of coarse carbides on the brittleness of the ODS alloy.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] (1) The present invention promotes the formation of a Cr2O3 protective layer by synergistically introducing Al and Si into the ODS alloy, thereby improving the high-temperature oxidation resistance of the ferrite / martensite dual-phase ODS steel;

[0030] (2) The present invention promotes the formation of a Cr2O3 protective layer by synergistically introducing Al and Si into the ODS alloy, thereby improving the LBE corrosion resistance of the ferrite / martensite dual-phase ODS steel;

[0031] (3) The present invention introduces Al and Si into the ODS alloy in a coordinated manner, thereby regulating the matrix microstructure while avoiding the formation of coarse second phases, thereby improving the mechanical properties of ferrite / martensite dual-phase ODS steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings are only for purposes of illustrating particular embodiments and are not to be considered limiting of the invention.

[0033] Figure 1 Schematic diagram of a scanning electron microscope image of a bulk ODS alloy after heat treatment with simultaneous addition of Al and Si in an embodiment of the present invention;

[0034] Figure 2 Schematic diagram comparing the tensile curves of Example 1, Comparative Example 1, and Comparative Example 2 of the present invention;

[0035] Figure 3 Schematic diagram of oxidation weight gain curves of Example 1, Comparative Example 1 and Comparative Example 2 of the present invention after oxidation at 850° C. for 200 h. DETAILED DESCRIPTION

[0036] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. In addition, the present invention can also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0037] A specific embodiment of the present invention, as Figure 1-3, discloses a high-performance ferrite / martensite dual-phase ODS steel and a preparation method thereof. In order to illustrate the effectiveness of the method proposed by the present invention, the above technical solution of the present invention is described in detail below through a specific embodiment. The specific implementation steps are as follows:

[0038] One object of the present invention is to provide a high-performance ferrite / martensite dual-phase ODS steel, wherein the high-performance ferrite / martensite dual-phase ODS steel comprises, by weight percentage, C: 0.06-0.1%; Cr: 8.5-9.5%; W: 0-4%; Mn: 0-4%; Al: 0.5-2.5%; Si: 0.5-2.5%; nano-oxide particles: 0-1.1%; and the remainder is Fe and unavoidable impurity elements.

[0039] Further, the nano-oxide particles include Y2O3, Y-Ti-O, Y-Zr-O and / or Y-Hf-O;

[0040] Furthermore, the Y-Ti-O includes Y2TiO5 and / or Y2Ti2O7; the Y-Zr-O includes Y4Zr3O 12 , the Y-Hf-O includes Y2Hf2O7;

[0041] The present invention simultaneously adds appropriate amounts of Al and Si to the 9CrWMn stainless steel. Al and Si preferentially react with inwardly diffusing O, preventing Cr oxidation within the ODS alloy matrix. This promotes the outward conversion of Cr ions and further facilitates the formation of a Cr2O3 protective film on the matrix surface. The Cr2O3 protective film hinders the inward diffusion of O ions, lead, and bismuth, as well as the outward diffusion of ODS alloy matrix ions, thereby improving the oxidation resistance and corrosion resistance of the ferrite / martensite duplex ODS steel at temperatures between 300 and 1000°C.

[0042] Another object of the present invention is to provide a method for preparing high-performance ferrite / martensite dual-phase ODS steel, comprising:

[0043] Step 1: Mixing a certain amount of nano-oxide particles and metal powder; mechanically alloying the nano-oxide particles and metal powder to obtain ODS alloyed powder;

[0044] Step 2: Sintering the ODS alloying powder to obtain a bulk ODS alloy;

[0045] Step 3, heat treating the sintered bulk ODS alloy to obtain high-performance ferrite / martensite dual-phase ODS steel;

[0046] Preferably, the nano-oxide particles in step 1 are Y2O3, Y-Ti-O, Y-Zr-O and / or Y-Hf-O; and the nano-oxide is prepared by a sol-gel or precipitation method.

[0047] The invention adopts a sol-gel or precipitation method to prepare nano oxide particles. The process is simple and efficient, and the prepared nano oxide particles are small in size and free of agglomeration.

[0048] Preferably, Y-Ti-O includes Y2TiO5 and / or Y2Ti2O7; the Y-Zr-O includes Y4Zr3O 12 ; The Y-Hf-O includes Y2Hf2O7;

[0049] Preferably, the metal powder in step 1 is a simple powder or a pre-alloyed powder; the pre-alloyed powder is prepared by gas atomization or rotating electrode atomization;

[0050] Preferably, the metal powder in step 1 comprises: by weight percentage, C: 0.06-0.1%; Cr: 8.5-9.5%; W: 0-4%; Mn: 0-4%; Al: 0.5-2.5%; Si: 0.5-2.5%;

[0051] Preferably, the mechanical alloying time in step 1 is 10-100 hours, and the rotation speed is 150-800 rpm;

[0052] Preferably, the sintering in step 2 includes hot isostatic pressing, hot pressing or hot extrusion;

[0053] Furthermore, the hot isostatic pressing sintering temperature is: 1130-1170°C, the pressure is 120-170 MPa; and the sintering time is 1-4 hours;

[0054] The present invention uses hot isostatic pressing, hot pressing or hot extrusion processes to form a bulk ODS alloy with high density, while maintaining a small matrix grain size, a small composite oxide particle size and excellent comprehensive performance.

[0055] Preferably, the heat treatment temperature in step 3 is 780-1170° C. and the time is 30-200 min;

[0056] The present invention performs heat treatment on the sintered bulk ODS alloy at 780-1170° C. to ensure complete austenitization and forms martensite during the quenching process.

[0057] The invention adds 0.5-2.5% by weight of aluminum. During high-temperature oxidation at 600-1000°C and LBE corrosion at 300-800°C, Al forms an Al2O3 protective layer on the surface of the ODS alloy matrix, thereby enhancing oxidation corrosion resistance.

[0058] The present invention adds 0.5-2.5% silicon by weight on the basis of adding Al, which can ensure that the alloy is a ferrite-martensite dual-phase steel and has good corrosion resistance, further improving the material's resistance to high-temperature oxidation corrosion without deteriorating the mechanical properties and radiation resistance of ODS steel.

[0059] The invention adds 0.06-0.1 weight percent carbon, ensures that the dual-phase steel can form 5-60% austenite phase after heat treatment, and reduces the influence of coarse carbides on the brittleness of the ODS alloy.

[0060] Example 1

[0061] Nano-sized Y2Ti2O7 particles were prepared by sol-gel method;

[0062] The elemental powders and Y2Ti2O7 nanoparticles were mechanically alloyed for 48 hours at a ball mill speed of 300 rpm. The elemental powders comprised the following weight percentages: C: 0.06-0.1%; Cr: 8.5-9.5%; W: 0-4%; Mn: 0-4%; Al: 0.5-2.5%; and Si: 0.5-2.5%.

[0063] After alloying, the powder was hot isostatically pressed and sintered at a temperature of 1160°C for 2 h. The C content was precisely controlled. The ODS alloy composition is shown in Table 1.

[0064] After sintering, heat treatment is performed: first, the ODS alloy is kept at 1050℃ for 1 hour to completely austenitize, and then quenched in water to room temperature;

[0065] After heat treatment, 9CrWMnAlSi-Y2Ti2O7 ferrite / martensite dual-phase ODS steel is obtained. The microstructure of the 9CrWMnAlSi-Y2Ti2O7 ferrite / martensite dual-phase ODS steel is as follows: Figure 1 As shown in Figure 2, it can be seen from the scanning electron microscope that the structure of the ODS alloy is composed of two phases: equiaxed ferrite and massive martensite.

[0066] Comparative Example 1

[0067] Nano-sized Y2Ti2O7 particles were prepared by sol-gel method;

[0068] The elemental powders and Y2Ti2O7 nanoparticles were mechanically alloyed for 48 hours at a ball mill speed of 300 rpm. The elemental powders comprised the following weight percentages: C: 0.06-0.1%; Cr: 8.5-9.5%; W: 0-4%; Mn: 0-4%; and Si: 0.5-2.5%.

[0069] After alloying, the powder was hot isostatically pressed and sintered at a temperature of 1160°C for 2 h. The C content was precisely controlled. The ODS alloy composition is shown in Table 1.

[0070] After sintering, heat treatment is performed: first, the ODS alloy is kept at 1050℃ for 1 hour to completely austenitize, and then quenched in water to room temperature;

[0071] After heat treatment, 9CrWMnSi-Y2Ti2O7 ferrite / martensite dual-phase ODS steel was obtained.

[0072] Comparative Example 2

[0073] Nano-sized Y2Ti2O7 particles were prepared by sol-gel method;

[0074] The elemental powders and Y2Ti2O7 nanoparticles were mechanically alloyed for 48 hours at a ball mill speed of 300 rpm. The elemental powders comprised the following weight percentages: C: 0.06-0.1%; Cr: 8.5-9.5%; W: 0-4%; Mn: 0-4%; and Al: 0.5-2.5%.

[0075] After alloying, the powder was hot isostatically pressed at 1160°C for 2 hours, while the C content was precisely controlled.

[0076] After sintering, heat treatment is performed: first, the ODS alloy is kept at 1050℃ for 1 hour to completely austenitize, and then quenched in water to room temperature;

[0077] After heat treatment, 9CrWMnAl-Y2Ti2O7 ferrite / martensite dual-phase ODS steel was obtained.

[0078] Figure 2 Compared with the tensile curves of the ODS alloys of Example 1, Comparative Example 1 and Comparative Example 2 in Table 2, it can be seen from the chart that the tensile strength of the ODS alloy with the addition of appropriate amounts of Al and Si is significantly improved compared with the ODS alloy with only single addition of Al or Si, while the elongation can still be maintained at a high level.

[0079] Figure 3 This is a comparison of the weight gain curves of Example 1, Comparative Example 1 and Comparative Example 2 after oxidation at 850°C for 200h. It can be seen from the figure that the oxidation weight gain of the alloy with simultaneous addition of Al and Si ODS is the lowest and the oxidation resistance is the best.

[0080] Table 3 is a statistical table of the oxide film thickness and corrosion layer thickness of the ODS alloy after LBE corrosion for 1555 hours at 550°C and saturated oxygen conditions for Example 1, Comparative Example 1 and Comparative Example 2. It can be seen from the table that the oxide layer and lead-bismuth corrosion depths of the ODS alloy with simultaneous addition of Al and Si are the lowest, and therefore the LBE corrosion resistance is better.

[0081] Table 1 Composition of the elemental powders of Example 1, Comparative Example 1 and Comparative Example 2 (wt.%)

[0082] C W Mn Al Si Cr <![CDATA[Y2Ti2O7]]> Fe Example 1 0.06 1.5 0.7 1.5 1 9 0.6 margin Comparative Example 1 0.06 1.5 0.7 0 2.5 9 0.6 margin Comparative Example 2 0.06 1.5 0.7 2.5 0 9 0.6 margin

[0083] Table 2 Mechanical properties of 9CrWMnAlSi-Y2Ti2O7 ferrite / martensite dual-phase ODS steel prepared in Example 1, Comparative Example 1 and Comparative Example 2

[0084] tensile strength Elongation Example 1 1194MPa 8.4％ Comparative Example 1 1096MPa 7.3％ Comparative Example 2 953MPa 9.6％

[0085] Table 3 Thickness of ODS alloy oxide film and corrosion layer of 9CrWMnAlSi-Y2Ti2O7 ferrite / martensite dual-phase ODS steel after LBE corrosion at 550℃ and saturated oxygen for 1555h in Example 1, Comparative Example 1 and Comparative Example 2

[0086] Oxide layer thickness Corrosion layer thickness Example 1 12.8±3.2μm 8.2±3.6μm Comparative Example 1 18.5±4.7μm 12.6±4.6μm Comparative Example 2 22.6±8.5μm 8.4±4.1μm

[0087] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A high performance ferrite / martensite dual-phase ODS steel, characterized in that: The high-performance ferrite / martensite dual-phase ODS steel comprises, by weight percentage, C: 0.06-0.1%, Cr: 8.5-9.5%, W: 0-4%, Mn: 0-4%, Al: 0.5-2.5%, Si: 0.5-2.5%, nano-oxide particles: 0-1.1%, and the remainder is Fe and unavoidable impurity elements.

2. A method for preparing high-performance ferrite / martensite dual-phase ODS steel, characterized in that: include: Step 1: Mixing a certain amount of nano-oxide particles and metal powder; mechanically alloying the nano-oxide particles and metal powder to obtain ODS alloyed powder; Step 2: Sintering the ODS alloying powder to obtain a bulk ODS alloy; Step 3: heat-treating the sintered bulk ODS alloy to obtain high-performance ferrite / martensite dual-phase ODS steel.

3. The method for preparing high performance ferrite / martensite dual-phase ODS steel according to claim 2, characterized in that: The nano-oxide particles include Y2O3, Y-Ti-O, Y-Zr-O and / or Y-Hf-O.

4. The method for preparing high performance ferrite / martensite dual-phase ODS steel according to claim 3, characterized in that: The Y-Ti-O is Y2TiO5 or Y2Ti2O7; the Y-Zr-O is Y4Zr3O 12 ; The Y-Hf-O is Y2Hf2O7.

5. The method for preparing high performance ferrite / martensite dual-phase ODS steel according to claim 2, characterized in that: The metal powder in step 1 is a simple powder or a pre-alloyed powder.

6. The method for preparing high performance ferrite / martensite dual-phase ODS steel according to claim 5, characterized in that: The metal powder in step 1 includes, by weight percentage, C: 0.06-0.1%, Cr: 8.5-9.5%, W: 0-4%, Mn: 0-4%, Al: 0.5-2.5%, and Si: 0.5-2.5%.

7. The method for preparing high performance ferrite / martensite dual-phase ODS steel according to claim 2, characterized in that: The mechanical alloying time in step 1 is 10-100 hours, and the rotation speed is 150-800 rpm.

8. The method for preparing high performance ferrite / martensite dual-phase ODS steel according to claim 2, characterized in that: The sintering method in step 2 includes hot isostatic pressing, hot pressing or hot extrusion.

9. The method for preparing high performance ferrite / martensite dual-phase ODS steel according to claim 8, characterized in that: The hot isostatic pressing sintering temperature in step 2 is 1130-1170° C., the pressure is 120-170 MPa, and the sintering time is 1-4 hours.

10. The method for preparing high performance ferrite / martensite dual-phase ODS steel according to claim 2, characterized in that: The heat treatment temperature in step 3 is 780-1170° C. and the time is 30-200 min.

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