A trace / trace element regulation method for optimizing the creep and oxidation performance of nickel-based single crystal superalloys

Abstract

The present application relates to the technical field of nickel-based superalloy, and particularly relates to a trace / microelement regulation method for optimizing the creep and oxidation performance of nickel-based single crystal superalloy. The trace / microelements in the optimized nickel-based single crystal superalloy satisfy the following conditions: Hf 1000-2000ppm; C: 50-150ppm; the total content of C+B is not more than 150ppm; Ce: 0 or 20-100ppm, Y: 0 or 20-100ppm, and 0 C+Y≤3 / 4 of the content of C element; and the total content of C, B, Hf, Ce and Y is 1000-2500ppm. The present application controls the added content of trace / microelements C, B, Hf, Ce and Y in the nickel-based single crystal superalloy, optimizes the micro-area distribution of the elements in the alloy structure, and thus improves the comprehensive service performance of the alloy in high-temperature creep and oxidation.

Description

Technical Field

[0001] This invention relates to the field of nickel-based superalloy technology, and in particular to a method for controlling trace / micro-elements to optimize the creep and oxidation properties of nickel-based single-crystal superalloys. Background Technology

[0002] Nickel-based single-crystal superalloys, due to their excellent heat resistance and high-temperature mechanical properties, have become key materials for manufacturing high-pressure turbine blades for aero-engines and gas turbines. A typical nickel-based single-crystal superalloy contains major additive elements (>1 wt.%) and trace (0.0001~0.01 wt.%) and micro (0.01~1 wt.%) additive elements. Major additive elements mainly include Ni, Al, Ta, Mo, Re, W, Cr, Co, and Ru, while common trace and micro additive elements include C, B, Hf, Ce, and Y. In traditional design, the addition of trace and micro elements is mainly used to improve the alloy's casting process performance or enhance its oxidation resistance; therefore, related design approaches mostly focus on optimizing these two aspects. However, recent studies have shown that the introduction of trace and micro elements has a significant impact on the mechanical properties of single-crystal alloys, especially creep properties. Currently, due to insufficient understanding of their influence mechanism and control methods, it is difficult to systematically balance the creep and oxidation properties of alloys in alloy composition design. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a trace element control method for optimizing the creep and oxidation properties of nickel-based single-crystal superalloys. The method of the present invention can optimize the overall service performance of nickel-based single-crystal superalloys in terms of creep and oxidation.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a nickel-based single-crystal superalloy with both high-temperature creep resistance and oxidation resistance, comprising major elements and trace / micro elements, wherein the trace / micro elements include multiple of C, B, Hf, Ce and Y; The trace elements meet the following conditions: Hf 1000~2000ppm; C: 50~150ppm; the total content of C+B does not exceed 150ppm; Ce: 0 or 20~100ppm, Y: 0 or 20~100ppm, and 0<Ce+Y≤3 / 4 of the C element content; and the total content of the five elements C, B, Hf, Ce and Y is 1000~2500ppm.

[0005] Preferably, the major elements include multiple elements selected from Ni, Al, Ta, Mo, Re, W, Cr, and Co.

[0006] Preferably, by mass percentage, it includes Al 5.0~9.0%, Ta 3.0~9.0%, Mo >1.0 and ≤12.0%, Co >1.0 and ≤10.0% or 0%, Cr >1.0 and ≤7.0%, Re 1.5~6.0%, W >1 and ≤6.0% or 0%, and Ni balance.

[0007] This invention provides a method for preparing a nickel-based single-crystal superalloy with both high-temperature creep resistance and oxidation resistance as described above, comprising the following steps: Provide master alloy ingots; The master alloy ingot is melted to obtain the master alloy; The master alloy is melted and then directionally solidified to obtain a cast single-crystal high-temperature alloy. The cast single-crystal superalloy is heat-treated to obtain the nickel-based single-crystal superalloy that has both high-temperature creep resistance and oxidation resistance.

[0008] Preferably, the heat treatment is divided into three heat treatments; the heat treatment includes: a first treatment in which the temperature is raised from 20~40℃ to Ts-5℃~Ts+5℃, held for 2~10h, and cooled by air cooling, wherein Ts is the solution treatment temperature of the standard heat treatment of nickel-based single crystal high-temperature alloys; a second treatment in which the temperature is raised from 20~40℃ to 1000~1150℃, held for 2~4h, and cooled by air cooling; and a third treatment in which the temperature is raised from 20~40℃ to 870~1080℃, held for 4~6h, and cooled by air cooling.

[0009] Preferably, the heating rate for the three heat treatments is independently 5~15℃ / min.

[0010] This invention provides a nickel-based single-crystal superalloy with both high-temperature creep resistance and oxidation resistance, comprising major elements and trace / micro elements. The trace / micro elements include multiples of C, B, Hf, Ce, and Y. The trace / micro elements meet the following conditions: Hf 1000~2000ppm; C: 50~150ppm; the total content of C+B does not exceed 150ppm; Ce: 0 or 20~100ppm; Y: 0 or 20~100ppm, and 0 < Ce+Y ≤ 3 / 4 of the C element content; and the total content of the five elements C, B, Hf, Ce, and Y is 1000~2500ppm. This invention, compared to existing nickel-based single-crystal superalloys, does not change the major elements but only optimizes the composition of trace / microelements. Specifically, this invention optimizes the micro-region distribution of trace elements (C, B, Hf, Ce, and Y) in the alloy microstructure by controlling the addition content of trace C, B, Hf, Ce, and Y elements, thereby improving the overall service performance of the alloy against high-temperature creep and oxidation. This invention provides an element regulation technology path for optimizing the microstructure stability and improving the overall performance of nickel-based single-crystal superalloys.

[0011] Unlike traditional trace element control methods that optimize single casting properties or single oxidation properties, this invention focuses on the multiple effects of these elements on the alloy's microstructure, creep properties, and oxidation properties. By understanding their distribution in the microstructure and their influence on creep and oxidation behavior, the microstructure stability of the alloy is improved, while simultaneously enhancing its high-temperature creep and oxidation properties. This invention effectively improves the overall service performance of the alloy in a low-cost and high-efficiency manner. Because the amount of elements involved is extremely small and does not require expensive additional processing equipment, this technical approach significantly reduces R&D and trial-and-error costs, demonstrating a high-efficiency and low-cost overall technical advantage. Attached Figure Description

[0012] Figure 1 The images show the SEM microstructure of the original alloy in Example 1, where (a) is at low magnification and (b) is at high magnification. Figure 2 This is an EPMA surface scan of the original alloy in Example 1; Figure 3 The image shows the SAED pattern of the original alloy carbides under a transmission electron microscope. Figure 4 The images show the SEM microstructure of the alloy with optimized composition in Example 1, where (a) is at low magnification and (b) is at high magnification. Figure 5 Example 1 compares the creep properties of the two alloys at 1100℃ / 120MPa; Figure 6 The oxidation weight gain curves of the two alloys in Example 1 at 1100℃ are shown. Figure 7 The oxidation rate curves of the two alloys in Example 1 at 1100℃ are shown. Figure 8 The SEM microstructure of the alloy with optimized composition in Example 2 is shown in (a) and (b) at low magnification, and (c) at high magnification. Figure 9 EPMA surface scan of the composition-optimized alloy in Example 2; Figure 10 SAED pattern of the composition-optimized alloy carbide under transmission electron microscopy in Example 2; Figure 11 Example 2 compares the creep properties of the two alloys at 1100℃ / 120MPa; Figure 12 The oxidation weight gain curves of the two alloys at 1100℃ are shown in Example 2. Figure 13 The oxidation rate curves of the two alloys in Example 2 at 1100℃ are shown. Figure 14The images show the SEM microstructure of the original alloy in Example 3, where (a) is at low magnification and (b) is at high magnification. Figure 15 The SEM microstructure of the alloy with optimized composition in Example 3 is shown in (a) low magnification and (b) high magnification. Figure 16 Example 3 compares the creep properties of the two alloys at 1100℃ / 120MPa; Figure 17 The oxidation weight gain curves of the two alloys in Example 3 at 1100℃ are shown. Figure 18 The oxidation rate curves of the two alloys in Example 3 at 1100℃ are shown. Detailed Implementation

[0013] This invention provides a nickel-based single-crystal superalloy with both high-temperature creep resistance and oxidation resistance, comprising major elements and trace / micro elements, wherein the trace / micro elements include multiple of C, B, Hf, Ce and Y; The trace elements meet the following conditions: Hf 1000~2000ppm; C: 50~150ppm; the total content of C+B does not exceed 150ppm; Ce: 0 or 20~100ppm, Y: 0 or 20~100ppm, and 0<Ce+Y≤3 / 4 of the C element content; and the total content of the five elements C, B, Hf, Ce and Y is 1000~2500ppm.

[0014] In a specific embodiment, the Hf content can be 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900 or 2000 ppm.

[0015] In specific embodiments, the content of C can be 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150 ppm. In this invention, the total content of C+B does not exceed 150 ppm. Both C and B are small atomic and light elements, and their mechanisms of action are similar, exhibiting similar effects, such as reducing the tendency to form small-angle grain boundaries. Therefore, this invention requires controlling the total content of both.

[0016] In specific embodiments, the Ce content can be 0, 20, 30, 40, 50, 60, 70, 80, 90, or 100 ppm; the Y content can be 0, 20, 30, 40, 50, 60, 70, 80, 90, or 100 ppm; and 0 < Ce + Y ≤ 3 / 4 of the C element content. By controlling the total Ce and Y content within the above ranges, this invention can prevent the formation of harmful precipitates and improve the oxidation resistance of the alloy.

[0017] By controlling the content of each element within the above-mentioned range, this invention ensures that nickel-based single-crystal superalloys possess both excellent high-temperature creep resistance and high-temperature oxidation resistance.

[0018] In specific embodiments of the present invention, the total content of the five elements C, B, Hf, Ce, and Y can be 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, or 2500 ppm. The present invention controls the content of these five elements within the range of 1000-2500 ppm, which is beneficial for ensuring the stability of the alloy structure.

[0019] In this invention, the major elements preferably include multiples of Ni, Al, Ta, Mo, Re, W, Cr, and Co; by mass percentage, the nickel-based single-crystal superalloy with both high-temperature creep resistance and oxidation resistance comprises Al 5.0~9.0%, Ta 3.0~9.0%, Mo >1.0 and ≤12.0%, Co >1.0 and ≤10.0% or 0%, Cr >1.0 and ≤7.0%, Re 1.5~6.0%, W >1 and ≤6.0% or 0%, with Ni as the balance. In specific embodiments, the Al content in the nickel-based single-crystal superalloy with both high-temperature creep and oxidation resistance can be 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, or 9.0%, the Ta content can be 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, or 9.0%, and the Mo content can be 1.1%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, 11.0%, or 12.0%. The content of Co can be 0%, 1.1%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, or 10.0%; the content of Cr can be 1.1%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, or 7.0%; the content of Re can be 1.5%, 2.0%, 3.0%, 4.0%, 5.0%, 5.5%, or 6.0%; and the content of W can be 0%, 1.1%, 1.5%, 2.0%, 3.0%, 4.0%, 5.0%, 5.5%, or 6.0%.

[0020] Compared with existing nickel-based single-crystal superalloys (hereinafter referred to as the original alloy), this invention does not change the composition of its major elements, but only optimizes the composition of its trace / micro elements, so as to obtain a nickel-based single-crystal superalloy (hereinafter referred to as the optimized alloy) that has both high-temperature creep resistance and oxidation resistance.

[0021] In this invention, the optimized alloy has no precipitates or contains precipitates, but the chemical composition, element types, and crystal structure of the precipitates in the original alloy remain unchanged compared to the original alloy.

[0022] In this invention, when the optimized alloy contains precipitates, the precipitates in the optimized alloy simultaneously satisfy: (a) the increase in precipitate content compared to the precipitates in the original alloy does not exceed 5%; (b) within any 100 μm... 2 Up to 200μm 2 (c) The statistical difference in the number of precipitates in different regions within the field of view is less than 5%; 2 In this invention, the content of the precipitated phase refers to a percentage by area, or a volume percentage converted from an area percentage.

[0023] In this invention, the average size and volume fraction of the γ' phase precipitated in the optimized alloy do not exceed 10% and 2% respectively compared to the original alloy.

[0024] This invention improves the high-temperature creep and oxidation resistance of the original alloy by optimizing the trace elements without changing its main microstructure.

[0025] This invention provides a method for preparing a nickel-based single-crystal superalloy with both high-temperature creep resistance and oxidation resistance as described above, comprising the following steps: Provide master alloy ingots; The master alloy ingot is melted to obtain the master alloy; The master alloy is melted and then directionally solidified to obtain a cast single-crystal high-temperature alloy. The cast single-crystal superalloy is heat-treated to obtain the nickel-based single-crystal superalloy that has both high-temperature creep resistance and oxidation resistance.

[0026] The present invention provides a master alloy ingot based on the target composition of the nickel-based single-crystal superalloy (hereinafter referred to as the optimized alloy) that has both high-temperature creep resistance and oxidation resistance.

[0027] The present invention does not impose any special limitation on the method of obtaining the master alloy ingot; it can be prepared by a preparation method well known in the art, which is common knowledge in the art.

[0028] After obtaining the master alloy ingot, the master alloy ingot is melted to obtain the master alloy; the master alloy is melted and then directionally solidified to obtain the cast single crystal high-temperature alloy; the cast single crystal high-temperature alloy is heat-treated to obtain the nickel-based single crystal high-temperature alloy with both high-temperature creep resistance and oxidation resistance.

[0029] This invention does not impose special requirements on the melting process; any melting process well-known in the art can be used. In an embodiment of this invention, vacuum induction melting is specifically employed. This invention does not impose special requirements on the directional solidification method; any directional solidification method well-known in the art can be used, such as the pulling method. In an embodiment of this invention, directional solidification is performed in a single crystal growth furnace with a temperature gradient of 30 K / cm, while the crystal is pulled at a speed of 3 mm / min.

[0030] In this invention, the heat treatment is preferably divided into three heat treatments; the heat treatment preferably includes: a first treatment in which the temperature is raised from 20~40℃ to Ts-5℃~Ts+5℃, held for 2~10h, and cooled by air cooling, wherein Ts is the solution treatment temperature of the standard heat treatment of nickel-based single crystal high-temperature alloy; a second treatment in which the temperature is raised from 20~40℃ to 1000~1150℃, held for 2~4h, and cooled by air cooling; and a third treatment in which the temperature is raised from 20~40℃ to 870~1080℃, held for 4~6h, and cooled by air cooling.

[0031] In this invention, the heating rate for each of the three heat treatments is preferably 5-15 °C / min. This invention achieves uniform elemental distribution and optimizes microstructure through heat treatment.

[0032] The trace / micro-element control method for optimizing the creep and oxidation properties of nickel-based single-crystal superalloys provided by the present invention will be described in detail below with reference to the embodiments. However, these should not be construed as limiting the scope of protection of the present invention.

[0033] Example 1 Taking the control of C element in a nickel-based single-crystal superalloy as an example: The original composition of this single-crystal superalloy is as follows: major elements are Al 5.0~7.0%, Ta 5.0~9.0%, Mo >1.0 and ≤3.0%, Co 6.0~10.0%, Cr 5.0~7.0%, Re 3~6%, W 3.0~6.0%, Ni balance, and trace elements are 550 ppm C, 50 ppm B, 1680 ppm Hf, and 20 ppm Y, with a total concentration of 2300 ppm. Without changing the major elements, only the trace elements of the alloy are adjusted and optimized. The C element is reduced to 100 ppm, and the optimized total concentration of trace elements is approximately 1850 ppm (<2500 ppm). The synergistic content of C and B is 150 ppm (≤150 ppm), and the total content of Ce and Y is 20 ppm, which is less than 3 / 4 of the C compound content. The specific composition is shown in Table 1.

[0034] The master alloy ingots of the original alloy and the optimized alloy were melted using a vacuum induction melting (VIM) process. The resulting master alloy was then used to obtain as-cast single-crystal test rods using a directional solidification method. The master alloy ingot was melted in a single-crystal growth furnace, and the resulting molten metal was poured into a mold shell. After holding at a certain temperature, the temperature gradient of the single-crystal growth furnace was controlled at 30 K / cm, while the crystal was pulled at a speed of 3 mm / min. After cooling, as-cast single-crystal high-temperature alloy test rods were obtained. Both the as-cast original alloy and the as-cast optimized alloy were subjected to the same heat treatment to homogenize the microstructure. The first heat treatment was performed by heating to 1335℃ at a rate of 15℃ / min and holding for 2 hours, followed by air cooling. The second heat treatment was performed by heating to 1120℃ at a rate of 15℃ / min and holding for 4 hours, followed by air cooling. The third heat treatment was performed by heating to 1050℃ at a rate of 15℃ / min and holding for 4 hours, followed by air cooling.

[0035] Table 1 Original and optimized composition of the single-crystal alloy in Example 1

[0036] The microstructure of the original alloy after heat treatment is shown in Figure 1. Figure 1 Among them, (a) low magnification; (b) high magnification. At low magnification, a field of view of 200 μm can be observed. 2 White precipitates were present in the microstructure, with some exceeding 10 μm in size and a content of 0.708%. Under high magnification, γ' phase and white γ' phase channels were visible in the alloy microstructure. After heat treatment, the γ / γ' phases were uniform in size and distribution, and the γ' phase exhibited a well-defined cubic shape. The average size and volume fraction of the γ' phase were 0.403 μm and 64.51%, respectively. Compositional analysis of the white precipitates in the microstructure was performed using electron probe microanalysis (EPMA). (See attached image). Figure 2 As shown in Table 2, the white precipitate was identified as a Ta- and Hf-rich MC-type carbide. The structure of the carbide was analyzed using selected area electron diffraction (SAED) under transmission electron microscopy, as shown in... Figure 3 As shown, by referring to the standard diffraction pattern in GB / T 18907-2013, the two diffraction axes obtained are the 1-10 and 112 diffraction axes of the face-centered cubic structure, thus it can be determined that the carbide has a face-centered cubic crystal structure.

[0037] Table 2. EPMA spot scan measurement results of carbide composition.

[0038] The microstructure of the composition-optimized alloy after heat treatment is shown in Figure 1. Figure 4Among them, (a) low magnification; (b) high magnification. At low magnification, it can be seen that after the carbon content is reduced, there are no more carbide precipitates in the alloy microstructure; at high magnification, the morphology of the γ / γ' phase in the heat-treated microstructure has changed slightly, but the size and distribution of the two phases are still uniform and the γ' phase is still in good cubic shape. The average size and volume fraction of the γ' phase are 0.431 μm and 63.59%, respectively; compared with the microstructure parameters of the original alloy, the change in the average size and volume fraction of the γ' phase is 6.94% and 0.92%, respectively, which meets the requirements.

[0039] The creep properties of the two heat-treated alloys were tested at 1100℃ / 120MPa according to the national standard GB / T 2039-2012. The creep strain-time curves are shown below. Figure 5 As shown, the creep rupture times of the original alloy and the composition-optimized alloy were 271 h and 410 h, respectively. It can be seen that compared with the creep rupture time of the original alloy, the creep rupture time of the alloy with reduced carbon content increased by about 0.51 times, indicating that reducing carbon content can improve the creep life of the alloy.

[0040] The two heat-treated alloys were subjected to cyclic oxidation tests at 1100℃ for a total time of 100 h according to standard HB 5258-2000. The oxidation weight gain curves are shown below. Figure 6 The total oxidation weight gain of the original alloy and the composition-optimized alloy were similar. The average oxide scale removal value of the original alloy and the composition-optimized alloy was 3.09 g / m². 2 and 2.44 g / m 2 The oxidation rate curve is shown in [reference needed]. Figure 7 During the oxidation process, the oxidation rate of the composition-optimized alloy was slower, with the average oxidation rates of the original alloy and the composition-optimized alloy being 0.009 g / (m²). 2 ·h) and 0.006 g / (m 2 •h). Cyclic oxidation experiments showed that, compared with the original alloy, the optimized alloy exhibited lower oxidation weight gain and a more stable oxidation rate. According to the evaluation standard table for the oxidation resistance of high-temperature alloys in HB 5258-2000 (see Table 3), the oxidation resistance of the optimized alloy falls within the oxidation resistance level.

[0041] In summary, reducing the carbon content can significantly improve the high-temperature creep performance of the alloy while ensuring its oxidation resistance, thus enhancing the overall performance of the alloy.

[0042] Table 3. Evaluation Standards for Oxidation Resistance of High-Temperature Alloys in HB 5258-2000 Standard

[0043] Example 2: Taking the control of C, B, and Ce elements in a nickel-based single-crystal superalloy as an example: The single-crystal alloy is identical to the original alloy in Example 1. A second optimization route was applied to the trace elements of this alloy, reducing the carbon element concentration to 150 ppm, ceasing the addition of boron, and increasing the ce element concentration to 70 ppm. The optimized total concentration of trace elements was approximately 1740 ppm (<2500 ppm), the total content of carbon and boron was 70 ppm (<150 ppm), and the total content of ce and y was 90 ppm, less than 3 / 4 of the carbon content. Specific composition is shown in Table 4. Since this original alloy is identical to the original alloy in Example 1, the alloy preparation process, heat treatment steps, microstructure morphology of the original alloy, and compositional structure analysis of the precipitates are described in Example 1.

[0044] Table 4 Original and optimized compositions of the single-crystal alloy in Example 2

[0045] The heat-treated microstructure of the alloy optimized according to the second optimization route is shown below. Figure 8 As shown, (a) and (b) are low magnification, and (c) is high magnification. At low magnification, the field of view is 200 μm. 2 As can be seen, the alloy still contains white precipitates, with a content of 0.723%. Compared with the carbides precipitated in the original alloy, the morphology of these precipitates has changed; their average size is smaller, and their morphology is a skeletal structure composed of fine particles. Figure 8 As shown in (b), the size of individual precipitated particles remained within 10 μm, meeting the requirements. At high magnification, the morphology of the γ / γ' phases in the heat-treated microstructure changed. While the size and distribution of both phases remained uniform, the γ' phase exhibited slight spheroidization compared to the original alloy. The average size and volume fraction of the γ' phase were 0.427 μm and 63.45%, respectively. Compared to the microstructure parameters of the original alloy, the changes in the average size and volume fraction of the γ' phase were 5.96% and 1.06%, respectively, meeting the requirements.

[0046] Compositional analysis of the white precipitates in the composition-optimized alloy microstructure was performed using electron probe microanalysis (EPMA). (See attached image.) Figure 9 As shown in Table 5, the composition of the white precipitate did not change significantly; it remained a Ta- and Hf-rich MC-type carbide, with Ta being the most abundant element. Selected area electron diffraction (SEG) was performed on the carbides in the composition-optimized alloy using transmission electron microscopy (TEM). Figure 10 As shown, by comparing with the standard diffraction pattern, the two diffraction axes obtained are the 111 and 112 diffraction axes of the face-centered cubic structure, which confirms that the crystal structure of the carbide has not changed and remains a face-centered cubic structure; in the diffraction spots, the 11-1 diffraction spot is 3.84 nm from the center point. -1This indicates that the interplanar spacing between the (111) planes of the carbide crystal is 1 / 3.84 = 0.26 nm, which is consistent with... Figure 3 The distance between the diffraction points in the middle 11-1 is 3.88 nm. -1 The difference is small, indicating that the lattice parameters of the carbide have not changed significantly.

[0047] Table 5. EPMA spot scan measurement results of carbide composition

[0048] The creep properties of the two heat-treated alloys were tested at 1100℃ / 120MPa according to the national standard GB / T 2039-2012. The creep strain-time curves are shown below. Figure 11 As shown, the creep rupture times of the original alloy and the composition-optimized alloy were 271 h and 283 h, respectively. It can be seen that the creep rupture time of the alloy with reduced carbon content increased by 12 h compared with that of the original alloy.

[0049] The two heat-treated alloys were subjected to cyclic oxidation resistance tests at 1100℃ for a total time of 100 h according to standard HB 5258-2000. The oxidation weight gain curves are shown below. Figure 12 As shown, the oxidation weight gain of the composition-optimized alloy is lower than that of the original alloy. The average oxide scale removal measurements for the original alloy and the composition-optimized alloy are 3.09 g / m². 2 and 0.65 g / m 2 The oxidation rate curve is shown in [reference needed]. Figure 13 As shown, the oxidation rate of the composition-optimized alloy is slower during the oxidation process. The average oxidation rates of the original alloy and the composition-optimized alloy are 0.009 g / (m²). 2 ·h) and 0.005 g / (m 2 •h). The results of the cyclic oxidation experiment show that the oxidation performance of the optimized alloy is superior to that of the original alloy. According to the evaluation standard table of oxidation resistance of high temperature alloys in HB 5258-2000 (see Table 3), the oxidation performance of the optimized alloy is close to the level of complete oxidation resistance.

[0050] In summary, by adjusting the C, B, and Ce elements, the creep performance and oxidation resistance of the alloy were improved, thus enhancing its overall performance.

[0051] Example 3: Taking the control of C, B, Hf, Ce, and Y elements in another nickel-based single-crystal superalloy as an example: The original composition of this single-crystal superalloy was as follows: major elements Al 6.0~9.0%, Ta 3.0~6.0%, Mo 8.0~12.0%, Cr >1.0 and ≤4.0%, Re 1.5~4.5%, Ni balance, with no trace elements added. Without changing the major elements, only the trace elements of the alloy were adjusted and optimized. C was added to 50 ppm, B to 30 ppm, Hf to 1500 ppm, Ce to 21 ppm, and Y to 20 ppm. The optimized total concentration of trace elements was approximately 1621 ppm (<2500 ppm), the synergistic content of C and B was 80 ppm (<150 ppm), and the total content of Ce and Y was 41 ppm, which was less than 3 / 4 of the C content (60 ppm). The specific composition is shown in Table 6. Both the as-cast original alloy and the as-cast composition-optimized alloy were subjected to the same heat treatment to homogenize the microstructure. The first heat treatment was carried out at a rate of 15℃ / min to 1315℃ and held for 4 h, followed by a rate of 5℃ / min to 1335℃ and held for 2 h before being removed and air-cooled. The second heat treatment was carried out at a rate of 15℃ / min to 1050℃ and held for 2 h before being removed and air-cooled. The third heat treatment was carried out at a rate of 15℃ / min to 890℃ and held for 6 h before being removed and air-cooled.

[0052] Table 6 Original and optimized compositions of the single-crystal alloy in Example 3

[0053] The microstructure of the original alloy after heat treatment is shown in Figure 1. Figure 14 Among them, (a) low magnification and (b) high magnification. It can be seen that there are no precipitated phases in the original alloy structure. Under high magnification, it can be seen that after heat treatment, the γ / γ' phase is uniform in size and distribution and the γ' phase is in good cubic shape. The average size and volume fraction of the γ' phase are 0.442 μm and 65.44%, respectively.

[0054] The microstructure of the composition-optimized alloy after heat treatment is shown in Figure 1. Figure 15 As shown, (a) is at low magnification and (b) is at high magnification. At low magnification, it can be seen that the reasonable addition of C, B, Hf, Ce, and Y elements does not cause the formation of carbides or precipitates in the alloy microstructure. At high magnification, the morphology of the γ / γ' phase in the heat-treated microstructure changes, but the size and distribution of the two phases remain uniform. The average size and volume fraction of the γ' phase are 0.465 μm and 65.17%, respectively. Compared with the microstructure parameters of the original alloy, the changes in the average size and volume fraction of the γ' phase are 5.20% and 0.27%, respectively, which meet the requirements.

[0055] The creep properties of the two heat-treated alloys were tested at 1100℃ / 120MPa according to the national standard GB / T 2039-2012. The creep strain-time curves are shown below. Figure 16 As shown, the creep rupture times of the original alloy and the composition-optimized alloy were 103 h and 112 h, respectively. It can be seen that the creep rupture time of the alloy with reduced carbon content increased by 9 h compared with that of the original alloy.

[0056] The two heat-treated alloys were subjected to cyclic oxidation resistance tests at 1100℃ for a total time of 100 h according to standard HB 5258-2000. The oxidation weight gain curves are shown below. Figure 17 As shown, the total oxidation weight gain of the composition-optimized alloy was reduced by approximately 23.6 g / m compared to the original alloy. 2 The average oxide scale removal values ​​for the original alloy and the composition-optimized alloy were 26.9 g / m². 2 and 0.61 g / m 2 The oxidation rate curve is shown in [reference needed]. Figure 18 As shown, the oxidation rate decreased significantly after the addition of C, B, Hf, Ce, and Y elements during the oxidation process. The average oxidation rates of the original alloy and the composition-optimized alloy were 0.098 g / (m²). 2 ·h) and 0.011 g / (m 2 •h). The results of the cyclic oxidation experiment show that the oxidation performance of the alloy after adding C, B, Hf, Ce and Y elements is significantly improved compared with the original alloy. According to the evaluation standard table of oxidation resistance of high temperature alloys in HB 5258-2000 standard (see Table 3), the oxidation performance of the composition-optimized alloy is close to the level of complete oxidation resistance.

[0057] In summary, by adjusting the C, B, Hf, Ce, and Y elements, the creep resistance of the alloy was ensured while the oxidation resistance was significantly improved, thus enhancing the overall performance of the alloy.

[0058] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A nickel-based single-crystal superalloy with both high-temperature creep resistance and oxidation resistance, comprising major elements and trace / micro elements, characterized in that, The trace elements include multiples of C, B, Hf, Ce, and Y; The trace elements meet the following conditions: Hf 1000~2000ppm; C: 50~150ppm; Total C+B content not exceeding 150ppm; Ce: 0 or 20~100ppm, Y: 0 or 20~100ppm, and 0 < Ce + Y ≤ 3 / 4 of the C element content; and the total content of the five elements C, B, Hf, Ce and Y is 1000~2500ppm.

2. The nickel-based single-crystal superalloy according to claim 1, characterized in that, The major elements include multiples of Ni, Al, Ta, Mo, Re, W, Cr, and Co.

3. The nickel-based single-crystal superalloy according to claim 2, characterized in that, The content by mass percentage includes Al 5.0~9.0%, Ta 3.0~9.0%, Mo >1.0 and ≤12.0%, Co >1.0 and ≤10.0% or 0%, Cr >1.0 and ≤7.0%, Re 1.5~6.0%, W >1 and ≤6.0% or 0%, and Ni balance.

4. The method for preparing the nickel-based single-crystal superalloy with both high-temperature creep resistance and oxidation resistance as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Provide master alloy ingots; The master alloy ingot is melted to obtain the master alloy; The master alloy is melted and then directionally solidified to obtain a cast single-crystal high-temperature alloy. The cast single-crystal superalloy is heat-treated to obtain the nickel-based single-crystal superalloy that has both high-temperature creep resistance and oxidation resistance.

5. The preparation method according to claim 4, characterized in that, The heat treatment is divided into three heat treatments; the heat treatment includes: the first treatment, which involves heating from 20~40℃ to Ts-5℃~Ts+5℃, holding at that temperature for 2~10 hours, and cooling by air cooling, where Ts is the solution treatment temperature of the standard heat treatment of nickel-based single crystal high-temperature alloys; the second treatment, which involves heating from 20~40℃ to 1000~1150℃, holding at that temperature for 2~4 hours, and cooling by air cooling; and the third treatment, which involves heating from 20~40℃ to 870~1080℃, holding at that temperature for 4~6 hours, and cooling by air cooling.

6. The preparation method according to claim 4, characterized in that, The heating rate for each of the three heat treatments was independently 5~15℃ / min.

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