Method for regulating and controlling carbide form in solidification process of high-temperature alloy and product thereof

Abstract

The invention relates to a method for regulating and controlling a carbide form in a high-temperature alloy solidification process and a product thereof. The method comprises the following steps: heating a nickel-based high-temperature alloy raw material to obtain a melt; inserting an electrode into the melt, and preheating for a period of time; setting a first pulse voltage, a pulse current and a pulse frequency according to the carbon content of the nickel-based superalloy raw material; setting a second pulse voltage, a pulse current and a pulse frequency according to different temperature intervals during pulse current treatment in the melt solidification process; and the obtained melt is subjected to heat preservation, second pulse voltage, pulse current and pulse frequency continue to be applied, and the nickel-based superalloy with the carbide morphology changed is obtained after treatment is finished. According to the method, pulse treatment is conducted on the nickel-based superalloy melt and in the melt solidification process, the regulation and control treatment time in the superalloy melt is short, the strengthening effect of refining and dispersing large-size carbides can be achieved, and accurate regulation and control over the morphology and size of the carbides are achieved through pulse current in the stages of carbide precipitation and melt solidification.

Description

Technical Field

[0001] The present invention belongs to the technical field of regulating the solidification process of superalloy melts, and specifically relates to a method for regulating the morphology of carbides during the solidification process of superalloys and its products. Background Art

[0002] In recent years, superalloys have been strategic key basic raw materials strongly supported by the country. The control of carbides in superalloys is becoming an important field in the production of high-quality metals. However, traditional superalloy technologies cannot precisely regulate the morphology and size of carbides in the alloy. The carbides in superalloys can be mainly divided into four categories: small blocky, long strip, Chinese character-like, and large blocky. In superalloys, carbides, as strengthening phases, their morphology, distribution, and stability are directly related to various properties of the alloy such as high-temperature strength, creep performance, and oxidation resistance. Fine and dispersed carbides can effectively hinder the movement of dislocations and improve the strength and hardness of the alloy. Coarse carbides, on the other hand, will become the initiation points of cracks, reducing the toughness and fatigue performance of the material, and even becoming the crack sources for subsequent processing and forging cracking. Therefore, by controlling the formation and evolution of carbides, the comprehensive performance of superalloys can be significantly improved to meet the requirements of different application fields.

[0003] Currently, for the problem of cracking in the processing and forging of materials caused by large-sized carbides in superalloys, there are measures such as controlling the cooling rate, solution treatment and aging treatment, and regulating the alloy composition, but this problem cannot be efficiently solved all the time. Precise control of temperature cannot be achieved by controlling the cooling rate, and it has a great impact on the material properties. Too fast cooling rate will cause defects such as shrinkage cavities in the material, and too slow will cause further nucleation and growth of carbides. The solution treatment and aging treatment processes take a long time, and the temperature selection range and cooling rate are greatly restricted. The composition regulation is greatly restricted by process parameters and carbide types. In recent years, the pulsed current melt purification technology has been continuously developed and has made good progress in the purification and homogenization regulation of various metal melts. The existing patent CN117431480A discloses a method for homogenizing nickel-based single-crystal superalloys using pulsed current, which can quickly eliminate carbides by applying a gradient pulsed current. However, it only performs homogenization pulsed treatment on solid samples of superalloys and cannot transform the carbides in solid samples into strengthening phases in superalloys. And according to research, there are differences in electrical conductivity between carbides such as niobium carbide and titanium carbide in superalloys and superalloy melts. Pulsed current can effectively inhibit the nucleation and growth of carbides and limit the formation of large-sized carbides. Summary of the Invention

[0004] In order to overcome the above problems existing in the prior art, the present invention provides a method for regulating the morphology of carbides during the solidification process of superalloys and its products to solve the above problems existing in the prior art.

[0005] A method for regulating the morphology of carbides during the solidification process of nickel-based superalloys, comprising the following steps:

[0006] S1. Place the nickel-based superalloy raw material in a corundum crucible and heat it to a certain temperature in an electric resistance furnace, and keep it warm for a period of time to fully melt the raw material to obtain a melt;

[0007] S2. During the continued insulation of the melt, insert the electrode connected to the pulsed current generating device into the melt and preheat it for a period of time;

[0008] S3. According to the carbon content of the nickel-based superalloy raw material, set the first pulsed voltage, pulsed current and pulse frequency output by the pulsed current generating device;

[0009] S4. According to the different temperature ranges during the pulsed current treatment in the solidification process of the melt, set the second pulsed voltage, pulsed current and pulse frequency output by the pulsed current generating device;

[0010] S5. Keep the melt obtained in S4 warm and continue to apply the second pulsed voltage, pulsed current and pulse frequency for a period of time. After the treatment is completed, turn off the electric resistance furnace and the pulsed power supply. After the electric resistance furnace cools down to a certain temperature, take out the obtained sample from the electric resistance furnace and perform air cooling to obtain a nickel-based superalloy with changed carbide morphology.

[0011] In the above-mentioned aspects and any possible implementation manners, a further implementation manner is provided. The period of time in S1 is 30 min, and the period of time in S2 and S5 is 5 - 10 min.

[0012] In the above-mentioned aspects and any possible implementation manners, a further implementation manner is provided. The carbon content of the nickel-based superalloy raw material is 0.03 - 0.12 wt.%.

[0013] In the above-mentioned aspects and any possible implementation manners, a further implementation manner is provided. The material of the electrode is graphite, and its bottom end is inserted to the bottom of the molten pool where the melt is located.

[0014] In the above-mentioned aspects and any possible implementation manners, a further implementation manner is provided. The first pulsed voltage is 5 - 36 V, the current intensity is 100 - 300 A, and the pulse frequency is 100 - 50000 Hz.

[0015] In the above-mentioned aspects and any possible implementation manners, a further implementation manner is provided. The certain temperature in S1 is 1400 - 1500 °C, and the certain temperature in S5 is 1250 °C - 1200 °C.

[0016] For the aspects and any possible implementation modes described above, a further implementation mode is provided. When the carbon content of the nickel-based superalloy raw material is [0.03, 0.05] wt.%, the first pulse frequency is [100, 1000] Hz, the current intensity is [140, 150] A, and the pulse voltage is [10, 20] V;

[0017] When the carbon content of the nickel-based superalloy raw material is (0.05, 0.08] wt.%, the first pulse frequency is (1000, 10000] Hz, the current intensity is [100, 110] A, and the pulse voltage is (20, 30] V;

[0018] When the carbon content of the nickel-based superalloy raw material is (0.08, 0.12] wt.%, the first pulse frequency is (10000, 50000] Hz, the current intensity is [80, 90] A, and the pulse voltage is (30, 36] V.

[0019] For the aspects and any possible implementation modes described above, a further implementation mode is provided. Specifically, S4 is as follows: When performing pulsed current treatment in the temperature range of 1500 - 1450 °C, the second pulse voltage, pulse current, and pulse frequency are all increased by 10 - 15% compared to the first pulse voltage, pulse current, and pulse frequency;

[0020] When performing holding electro-pulse treatment in the temperature range of 1450 - 1350 °C, the first pulse voltage, pulse current, and pulse frequency are adopted;

[0021] When performing holding electro-pulse treatment in the temperature range of 1350 - 1250 °C, the second pulse voltage, pulse current, and pulse frequency are all decreased by 10 - 15% compared to the first pulse voltage, pulse current, and pulse frequency.

[0022] For the aspects and any possible implementation modes described above, a further implementation mode is provided. The air cooling rate in S5 is 10 °C - 50 °C / min.

[0023] The present invention also provides a nickel-based superalloy, which is prepared by the method described above.

[0024] Advantages of the present invention

[0025] The method for regulating the carbide morphology in the solidification process of nickel-based superalloys of the present invention comprises the following steps: placing the nickel-based superalloy raw materials in a corundum crucible and heating them to a certain temperature in an electric resistance furnace, holding for a period of time to fully melt the raw materials to obtain a melt; during the continued holding of the melt, inserting an electrode connected to a pulsed current generating device into the melt and preheating for a period of time; setting the first pulsed voltage, pulsed current and pulse frequency output by the pulsed current generating device according to the carbon content of the nickel-based superalloy raw materials; setting the second pulsed voltage, pulsed current and pulse frequency output by the pulsed current generating device according to the different temperature ranges during the pulsed current treatment in the solidification process of the melt; holding the obtained melt and continuing to apply the second pulsed voltage, pulsed current and pulse frequency for a period of time, after the treatment is completed, turning off the electric resistance furnace and the pulsed power supply, after the electric resistance furnace cools down to a certain temperature, taking out the obtained sample from the electric resistance furnace for air cooling to obtain a nickel-based superalloy with changed carbide morphology. The present invention performs pulsed treatment on the nickel-based superalloy melt and during the solidification process of the melt. The pulsed current can promote the redistribution of elements in the superalloy melt, and the regulation treatment time in the superalloy melt is short, and the strengthening effect of refining and dispersing large-sized carbides can be achieved. The morphology and size of carbides can be precisely regulated by pulsed current during the carbide precipitation and melt solidification stages. The present invention regulates from the process source, has a short treatment time and is green and pollution-free, and is expected to be applied to industrial production as a new green and efficient means. The present invention sets different pulse frequencies, pulsed voltages and pulsed currents; and the pulse frequency parameter range is wider. The current intensities generated under different pulse frequencies and pulsed voltages are different. The current intensity generated under low-frequency pulsed current is higher, while the current intensity under ultra-high-frequency pulsed current is lower, but at the same time, the ultra-high-frequency pulsed current has an oscillation effect. The method of the present invention can effectively solve the problem of forging cracking caused by large-sized carbides in the subsequent processing of superalloys. This method regulates from the process source, simplifies the process flow, and can greatly reduce the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 FIG. is a schematic structural diagram of the device for regulating the size and morphology of carbides during the solidification of a superalloy melt by pulsed current according to the present invention;

[0027] Figure 2 FIG. shows the comparison of the size and morphology of carbides after solidification of superalloys with and without pulsed current treatment in the examples and comparative examples of the present invention, wherein, (a) is the effect diagram of the example, and (b) is the effect diagram of the comparative example;

[0028] Figure 3 FIG. is a flowchart of the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] To better understand the technical solution of the present invention, the content of the present invention includes but is not limited to the specific embodiments hereinafter. Similar technologies and methods should be regarded as within the scope of protection of the present invention. To make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments.

[0030] It should be clear that the embodiments described in the present invention are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0031] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms of "a", "the" and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0032] As Figure 3 shown, the present invention provides a method for regulating the carbide morphology in the solidification process of nickel-based superalloys, including the following steps:

[0033] S1. Place the nickel-based superalloy raw material in a corundum crucible and heat it to a certain temperature in a resistance furnace, and keep it warm for a period of time to fully melt the raw material to obtain a melt;

[0034] S2. During the continuous insulation of the melt, insert the electrode connected to the pulsed current generating device into the melt and preheat it for a period of time;

[0035] S3. Set the first pulse voltage, pulse current and pulse frequency output by the pulsed current generating device according to the carbon content of the nickel-based superalloy raw material;

[0036] S4. Set the second pulse voltage, pulse current and pulse frequency output by the pulsed current generating device according to the different temperature ranges during the pulsed current treatment in the solidification process of the melt;

[0037] S5. Keep the melt obtained in S4 warm and continue to apply the second pulse voltage, pulse current and pulse frequency for a period of time. After the treatment is completed, turn off the resistance furnace and the pulsed power supply. After the resistance furnace cools down to a certain temperature, take out the obtained sample from the resistance furnace and air-cool it to obtain a nickel-based superalloy with changed carbide morphology.

[0038] Specifically, the specific process of the present invention is as follows:

[0039] A method for regulating the carbide morphology in the solidification process of superalloys, including the following steps:

[0040] S1: Place the nickel-based superalloy raw material in a corundum crucible and heat it in a resistance furnace to 1400 - 1500 °C. Keep it warm for 30 min to fully melt the raw material. Stir the melt during the holding period to make its composition and temperature uniform, and fully melt the superalloy to obtain a melt;

[0041] S2: Keep the melt warm. Connect the graphite electrode to the pulse current generating device through a metal wire. After connecting the two parallel electrodes to the pulse power supply, vertically insert them into the melt and preheat for 5 - 10 min to prevent the nickel-based superalloy melt from adhering to the graphite electrode;

[0042] S3: Set the initial pulse voltage, pulse current, and pulse frequency according to the carbon content of the nickel-based superalloy raw material. The initial pulse voltage, pulse current, and pulse frequency are regarded as the first pulse voltage, pulse current, and pulse frequency, providing a reference for subsequent adjustment of the pulse current value;

[0043] S4: Further adjust the initial pulse voltage, pulse current, and pulse frequency as the second pulse voltage, pulse current, and pulse frequency according to the different temperature ranges during the pulse current treatment in the solidification process of the melt. Apply pulse current treatment to the melt for 5 - 10 min during the holding stage. The second pulse voltage, pulse current, and pulse frequency set different specific parameters for different treatment temperatures; during the solidification process of the melt, after applying the pulse current, the carbides change from large blocky or strip-shaped to dot-shaped. The pulse current mainly produces an effect during the carbide precipitation stage in the solidification process of the melt, used to inhibit the growth of carbides.

[0044] S5: After the treatment, turn off the resistance furnace and the pulse power supply. After the resistance furnace cools down to 1250 °C - 1200 °C, take out the sample from the resistance furnace and air-cool it. The cooling rate is 10 °C - 50 °C / min to quickly cool the obtained sample and further inhibit the nucleation and growth of carbides.

[0045] Preferably, in the step S1, the melting temperature of the nickel-based superalloy raw material is controlled within the temperature range where the nickel-based superalloy raw material is completely in a molten state and meets the requirements of industrial production, specifically 1500 - 1520 °C.

[0046] Preferably, in the step S1, the carbon content of the nickel-based superalloy raw material is 0.03 - 0.11 wt.%.

[0047] As Figure 1As shown in the figure, the device for regulation includes a pulse generator, a copper wire 1, a copper nose 2, a graphite electrode 3, a corundum crucible 4, a metal melt 5, and a resistance furnace. The corundum crucible 4 is placed in the resistance furnace, and a nickel-based superalloy raw material is placed in the corundum crucible 4, that is, the reaction takes place here. A copper nose 2 is provided at the upper end of the graphite electrode 3, and the copper nose 2 is connected to the pulse generator through the copper wire 1. When the nickel-based superalloy raw material in the corundum crucible 4 is heated by the resistance furnace, the pulse generator applies a set pulse voltage, pulse current, and pulse frequency to the metal melt 5 through the copper wire 1 and the graphite electrode 3.

[0048] Preferably, in step S2, the bottom end of the graphite electrode 3 is located at the deepest part of the melt.

[0049] Preferably, in step S3, the pulse voltage is 5 - 36V, the current intensity is 100 - 300A, and the pulse frequency is 100 - 50000Hz.

[0050] Further preferably, in step S3, according to the carbon content of the nickel-based superalloy raw material, the initial pulse voltage, pulse current, and pulse frequency are set, specifically:

[0051] When the carbon content of the nickel-based superalloy raw material is [0.03, 0.05] wt.%, the first pulse frequency is [100, 1000] Hz, the current intensity is [140, 150] A, and the pulse voltage is [10, 20] V;

[0052] When the carbon content of the nickel-based superalloy raw material is (0.05, 0.08] wt.%, the first pulse frequency is (1000, 10000] Hz, the current intensity is [100, 110] A, and the pulse voltage is (20, 30] V;

[0053] When the carbon content of the nickel-based superalloy raw material is (0.08, 0.12] wt.%, the first pulse frequency is (10000, 50000] Hz, the current intensity is [80, 90] A, and the pulse voltage is (30, 36] V.

[0054] Preferably, in step S4, according to the different temperature ranges during the pulse current treatment in the solidification process of the melt, the initial pulse voltage, pulse current, and pulse frequency are further adjusted, specifically:

[0055] Under the condition of the same carbon content, the subsequent pulse-related parameters are set according to different temperatures. When pulse current treatment is carried out in the melt temperature range of 1500 - 1450 °C, the second pulse voltage, pulse current and pulse frequency increase by 10 - 15% compared with the first pulse voltage, pulse current and pulse frequency. That is, when the carbon content is known, under the condition of the same carbon content, the first pulse parameters can be determined. At this time, the basis for the percentage increase of the second pulse parameters is the first pulse parameters, and the same applies hereinafter.

[0056] Under the condition of the same carbon content, the subsequent pulse-related parameters are set according to different temperatures. When holding electric pulse treatment is carried out in the melt temperature range of 1450 - 1350 °C, the first pulse voltage, pulse current and pulse frequency are adopted, that is, the related parameters of the electric pulse remain unchanged;

[0057] Under the condition of the same carbon content, the subsequent pulse-related parameters are set according to different temperatures. When holding electric pulse treatment is carried out in the melt temperature range of 1350 - 1250 °C, the second pulse voltage, pulse current and pulse frequency are reduced by 10 - 15% compared with the first pulse voltage, pulse current and pulse frequency.

[0058] Preferably, in step S5, after the resistance furnace cools down to 1250 °C - 1200 °C, when the sample solidifies and becomes solid, it is taken out of the resistance furnace for air cooling, and the air cooling rate is set to 50 °C / min. The refinement of the large-size carbide particle size can be realized under the treatment of a short time, and the precise control of the carbide morphology and size can be achieved.

[0059] The following will be described by specific examples and comparative examples

[0060] Example 1

[0061] In this example, pulse current treatment is carried out on a nickel-based superalloy raw material with a carbon content of 0.045 wt.% in a crucible. The steps are as follows:

[0062] S1: The nickel-based superalloy raw material is placed in a crucible and heated to 1500 °C in a resistance furnace, and kept warm for 30 min to fully melt the raw material. Subsequently, the melt is stirred to make its composition and temperature uniform;

[0063] S2: The melt is kept warm at 1520 °C. After connecting two parallel electrodes to the pulse power supply, they are vertically inserted into the deepest part of the melt and preheated for 5 min;

[0064] S3: Set the pulse voltage, pulse current and pulse frequency; the pulse voltage is 15 V, the current intensity is 145 A, and the pulse frequency is 100 Hz.

[0065] S4: After the treatment is completed, turn off the resistance furnace and the pulse power supply. After the resistance furnace cools down to 1250 °C, take out the sample from the resistance furnace and air-cool it. The cooling rate is 50 °C / min.

[0066] S5: The solidified ingot obtained after pulse treatment is longitudinally cut along the center line of the two electrodes. After grinding and polishing, the morphology, size and distribution of carbides can be clearly observed in the backscattering mode of the scanning electron microscope. It is observed that the carbides are evenly distributed in the ingot without enrichment. After detecting and statistically analyzing the carbides at different positions, it is obtained that the area ratio of carbides is reduced from the original 2.03% to the lowest 1.36%, and the maximum reduction rate reaches 33%. The average particle size of carbides is reduced from the original 25.35 μm to the lowest 13.45 μm, and the maximum reduction rate reaches 46.9%. The superalloy ingot realizes the dispersion strengthening of carbides.

[0067] Example 2

[0068] In this example, a nickel-based superalloy raw material with a carbon content of 0.062 wt.% in the crucible is treated with pulsed current. The steps are as follows:

[0069] S1: Place the nickel-based superalloy raw material in the crucible and heat it to 1500 °C in a resistance furnace. Keep it warm for 30 min to fully melt the raw material, and then stir the melt to make its composition and temperature uniform;

[0070] S2: Keep the melt at 1520 °C for further insulation. Connect two parallel electrodes to the pulse power supply and vertically insert them into the deepest part of the melt, and preheat for 5 min;

[0071] S3: Set the pulse voltage, pulse current and pulse frequency; the pulse voltage is 25 V, the current intensity is 125 A, and the pulse frequency is 500 Hz.

[0072] S4: After the treatment is completed, turn off the resistance furnace and the pulse power supply. After the resistance furnace cools down to 1250 °C, take out the sample from the resistance furnace and air-cool it. The cooling rate is 50 °C / min.

[0073] S5: The solidified ingot obtained after pulse treatment is longitudinally cut along the center line of the two electrodes. After grinding and polishing, the morphology, size and distribution of carbides can be clearly observed in the backscattering mode of the scanning electron microscope. It is observed that the carbides are evenly distributed in the ingot without enrichment. After detecting and statistically analyzing the carbides at different positions, it is obtained that the area ratio of carbides is reduced from the original 2.05% to the lowest 1.29%, and the maximum reduction rate reaches 37%. The average particle size of carbides is reduced from the original 25.07 μm to the lowest 11.35 μm, and the maximum reduction rate reaches 54.7%. The superalloy ingot realizes the dispersion strengthening of carbides.

[0074] Example 3

[0075] In this embodiment, a nickel-based superalloy raw material with a carbon content of 0.096 wt.% in a crucible is processed by pulsed current. The steps are as follows:

[0076] S1: Place the nickel-based superalloy raw material in a crucible and heat it to 1500 °C in a resistance furnace. Keep it warm for 30 min to fully melt the raw material, and then stir the melt to make its composition and temperature uniform;

[0077] S2: Keep the melt at 1520 °C for further insulation. Connect two parallel electrodes to a pulsed power supply and vertically insert them into the deepest part of the melt, and preheat for 5 min;

[0078] S3: Set the pulsed voltage, pulsed current and pulse frequency; the pulsed voltage is 30 V, the current intensity is 110 A, and the pulse frequency is 3000 Hz.

[0079] S4: After the treatment is completed, turn off the resistance furnace and the pulsed power supply. After the resistance furnace cools down to 1250 °C, take out the sample from the resistance furnace and air-cool it, and the cooling rate is 50 °C / min.

[0080] S5: The solidified ingot obtained after pulsed treatment is longitudinally cut along the center line of the two electrodes. After grinding and polishing, the morphology, size and distribution of carbides can be clearly observed in the backscattering mode of a scanning electron microscope. It is observed that the carbides are evenly distributed in the ingot without enrichment. After detecting and statistically analyzing the carbides at different positions, it is obtained that the area ratio of carbides is reduced from the original 2.02% to the lowest 1.12%, and the maximum reduction rate reaches 44.5%. The average particle size of carbides is reduced from the original 26.47 μm to the lowest 8.98 μm, and the maximum reduction rate reaches 66%. The superalloy ingot realizes the dispersion strengthening of carbides.

[0081] Example 4

[0082] In this embodiment, a nickel-based superalloy raw material with a carbon content of 0.11 wt.% in a crucible is processed by pulsed current. The steps are as follows:

[0083] S1: Place the nickel-based superalloy raw material in a crucible and heat it to 1500 °C in a resistance furnace. Keep it warm for 30 min to fully melt the raw material, and then stir the melt to make its composition and temperature uniform;

[0084] S2: Keep the melt at 1520 °C for further insulation. Connect two parallel electrodes to a pulsed power supply and vertically insert them into the deepest part of the melt, and preheat for 5 min;

[0085] S3: Set the pulsed voltage, pulsed current and pulse frequency; the pulsed voltage is 32 V, the current intensity is 100 A, and the pulse frequency is 10000 Hz.

[0086] S4: After the treatment, turn off the resistance furnace and the pulse power supply. After the resistance furnace cools down to 1250 °C, take out the sample from the resistance furnace and air-cool it. The cooling rate is 50 °C / min.

[0087] S5: The solidified ingot obtained after pulse treatment is longitudinally cut along the center line of the two electrodes. After grinding and polishing, the morphology, size and distribution of carbides can be clearly observed in the backscattering mode of a scanning electron microscope. It is observed that the carbides are evenly distributed in the ingot without enrichment. After detecting and statistically analyzing the carbides at different positions, it is obtained that the area ratio of carbides is reduced from the original 2.11% to the lowest 1.11%, and the maximum reduction rate reaches 47.3%. The average particle size of carbides is reduced from the original 26.47 μm to the lowest 9.67 μm, and the maximum reduction rate reaches 63.4%. The superalloy ingot realizes the dispersion strengthening of carbides.

[0088] Example 5

[0089] In this example, a nickel-based superalloy raw material with a carbon content of 0.11 wt.% in the crucible is treated with pulsed current. The steps are as follows:

[0090] S1: Place the nickel-based superalloy raw material in the crucible and heat it to 1500 °C in a resistance furnace. Keep it warm for 30 min to fully melt the raw material, and then stir the melt to make its composition and temperature uniform;

[0091] S2: Keep the melt at 1520 °C. After connecting two parallel electrodes to the pulse power supply, vertically insert them into the deepest part of the melt and preheat for 5 min;

[0092] S3: Set the pulse voltage, pulse current and pulse frequency; the pulse voltage is 36 V, the current intensity is 90 A, and the pulse frequency is 30000 Hz.

[0093] S4: After the treatment, turn off the resistance furnace and the pulse power supply. After the resistance furnace cools down to 1250 °C, take out the sample from the resistance furnace and air-cool it. The cooling rate is 50 °C / min.

[0094] S5: The solidified ingot obtained after pulse treatment is longitudinally cut along the center line of the two electrodes. After grinding and polishing, the morphology, size and distribution of carbides can be clearly observed in the backscattering mode of a scanning electron microscope. It is observed that the carbides are evenly distributed in the ingot without enrichment. After detecting and statistically analyzing the carbides at different positions, it is obtained that the area ratio of carbides is reduced from the original 2.11% to the lowest 0.93%, and the maximum reduction rate reaches 55.9%. The average particle size of carbides is reduced from the original 25.03 μm to the lowest 10.45 μm, and the maximum reduction rate reaches 58.2%. The superalloy ingot realizes the dispersion strengthening of carbides.

[0095] Comparative Example 1

[0096] In this comparative example, a nickel-based superalloy raw material with a carbon content of 0.11 wt.% in the crucible was processed without applying a pulsed current. The steps are as follows:

[0097] S1: Place the nickel-based superalloy raw material in a crucible and heat it to 1500 °C in a resistance furnace. Keep it warm for 30 min to fully melt the raw material, and then stir the melt to make its composition and temperature uniform;

[0098] S2: Keep the melt warm at 1520 °C, vertically insert two parallel electrodes into the deepest part of the melt, and preheat for 5 min, but do not apply pulsed current treatment;

[0099] S3: After the treatment, turn off the resistance furnace and the pulsed power supply. After the resistance furnace cools down to 1250 °C, take out the sample from the resistance furnace and air-cool it. The cooling rate is 50 °C / min.

[0100] S4: In this comparative example, no pulsed current was applied. After the treatment, the solidified ingot was longitudinally cut along the center line of the two electrodes. After grinding and polishing, the morphology, size and distribution of carbides can be clearly observed in the backscattering mode of a scanning electron microscope. It is observed that the carbides are evenly distributed in the ingot and no enrichment phenomenon occurs. After detecting and statistically analyzing the carbides at different positions, it is obtained that the area ratio of carbides decreases from the original 2.11% to the lowest 1.98%, and the maximum reduction rate reaches 6.1%. The average particle size of carbides decreases from the original 26.47 μm to the lowest 24.12 μm, and the maximum reduction rate reaches 8.8%. The superalloy ingot fails to achieve carbide dispersion strengthening.

[0101] Comparative Example 2

[0102] In this comparative example, a nickel-based superalloy raw material with a carbon content of 0.08 wt.% in the crucible was processed with a pulsed current. The steps are as follows:

[0103] S1: Place the nickel-based superalloy raw material in a crucible and heat it to 1500 °C in a resistance furnace. Keep it warm for 30 min to fully melt the raw material, and then stir the melt to make its composition and temperature uniform;

[0104] S2: Keep the melt warm at 1350 °C, connect two parallel electrodes to the pulsed power supply and vertically insert them into the deepest part of the melt, and preheat for 5 min;

[0105] S3: Set the pulsed voltage, pulsed current and pulse frequency; the pulsed voltage is 28 V, the current intensity is 120 A, and the pulse frequency is 1000 Hz.

[0106] S4: After the treatment, turn off the resistance furnace and the pulsed power supply. The sample is cooled with the furnace from 1520 °C. The cooling rate is 50 °C / min.

[0107] S5: In this comparative example, the pulse parameters are not set according to the carbon content, nor are they adjusted according to the temperature range change during the pulse current treatment in the solidification process of the melt. The solidified ingot obtained after pulse treatment is longitudinally cut along the center line of the two electrodes. After grinding and polishing, the morphology and size distribution of carbides can be clearly observed in the backscattering mode of a scanning electron microscope. It is observed that the carbides are evenly distributed in the ingot without enrichment. After detecting and statistically analyzing the carbides at different positions, it is obtained that the area ratio of carbides decreases from the original 2.02% to a minimum of 1.66%, and the maximum reduction rate reaches 17.8%. The average particle size of carbides decreases from the original 26.33 μm to a minimum of 20.51 μm, and the maximum reduction rate reaches 22.1%. The carbide dispersion strengthening of the superalloy ingot cannot be achieved.

[0108] Comparative Example 3

[0109] In this comparative example, pulse current treatment is carried out on a nickel-based superalloy raw material with a carbon content of 0.08 wt.% in a crucible. The steps are as follows:

[0110] S1: Place the nickel-based superalloy raw material in a crucible and heat it to 1500 °C in a resistance furnace, keep it warm for 30 min to fully melt the raw material, and then stir the melt to make its composition and temperature uniform;

[0111] S2: Keep the melt at 1250 °C. After connecting two parallel electrodes to a pulse power supply, vertically insert them into the deepest part of the melt and preheat for 5 min;

[0112] S3: Set the pulse parameters according to the change of carbon content, and set the pulse voltage, pulse current and pulse frequency; the pulse voltage is 30 V, the current intensity is 120 A, and the pulse frequency is 2000 Hz.

[0113] S4: After the treatment is completed, turn off the resistance furnace and the pulse power supply. The sample is cooled with the furnace from 1520 °C, and the cooling rate is 50 °C / min.

[0114] S5: In this comparative example, the pulse parameters were set according to the carbon content, but the pulse parameters were not adjusted according to the temperature range change during the pulsed current treatment in the solidification process of the melt. The solidified ingot obtained after the pulse treatment was longitudinally cut along the center line of the two electrodes. After grinding and polishing, the morphology and size distribution of the carbides could be clearly observed in the backscattering mode of the scanning electron microscope. It was observed that the carbides were evenly distributed in the ingot without enrichment. After detecting and statistically analyzing the carbides at different positions, it was found that the area fraction of the carbides decreased from the original 2.02% to a minimum of 1.61%, with a maximum reduction rate of 20.2%. The average particle size of the carbides decreased from the original 25.89 μm to a minimum of 19.9 μm, with a maximum reduction rate of 23.13%. The carbide dispersion strengthening of the superalloy ingot was not achieved.

[0115] Comparative Example 4

[0116] In this comparative example, a pulsed current treatment was carried out on a nickel-based superalloy raw material with a carbon content of 0.08 wt.% in a crucible. The steps are as follows:

[0117] S1: Place the nickel-based superalloy raw material in a crucible and heat it to 1500 °C in a resistance furnace, hold for 30 min to fully melt the raw material, and then stir the melt to make its composition and temperature uniform;

[0118] S2: Keep the melt at 1520 °C for further holding. After connecting two parallel electrodes to the pulse power supply, vertically insert them into the deepest part of the melt and preheat for 5 min;

[0119] S3: Set the pulse parameters according to the change of carbon content, and set the pulse voltage, pulse current and pulse frequency; the pulse voltage is 30 V, the current intensity is 120 A, and the pulse frequency is 2000 Hz.

[0120] S4: After the treatment, turn off the resistance furnace and the pulse power supply. The sample is cooled with the furnace from 1520 °C, and the cooling rate is 10 °C / min.

[0121] S5: In this comparative example, the pulse parameters were set according to the carbon content and adjusted according to the temperature range change during the pulsed current treatment in the solidification process of the melt, but the cooling rate was adjusted to 10 °C / min. The solidified ingot obtained after the pulse treatment was longitudinally cut along the center line of the two electrodes. After grinding and polishing, the morphology and size distribution of the carbides could be clearly observed in the backscattering mode of the scanning electron microscope. It was observed that the carbides were evenly distributed in the ingot without enrichment. After detecting and statistically analyzing the carbides at different positions, it was found that the area fraction of the carbides decreased from the original 2.02% to a minimum of 1.78%, with a maximum reduction rate of 11.8%. The average particle size of the carbides decreased from the original 27.35 μm to a minimum of 21.13 μm, with a maximum reduction rate of 22.74%. The carbide dispersion strengthening of the superalloy ingot was not achieved.

[0122] As Figure 2 shown in (a) and (b) therein, for the cases with and without the application of pulsed current, it can be obtained by combining the above-mentioned examples and comparative examples that, within the temperature range where the superalloy raw material is completely in a molten state and meets the requirements of industrial production, the corresponding pulsed voltage, pulsed current and pulse frequency are set according to the carbon content of the nickel-based superalloy raw material; meanwhile, according to the different temperature intervals during the pulsed current treatment in the melt solidification process, the initial pulsed voltage, pulsed current and pulse frequency are adjusted in real time. After the pulsed treatment is completed, the specimen is taken out of the resistance furnace and air-cooled, and the air-cooling rate is set at 50 °C / min. The efficient control of the carbide size and morphology can be realized under the treatment for a short time, so as to achieve the fine and dispersed distribution of carbides in the superalloy ingot. The present invention can effectively solve the problems such as forging cracking caused by large-size carbides in the subsequent processing of superalloys. By regulating from the process source, the process flow is simplified, and the production cost can be greatly reduced.

[0123] The above description has shown and described several preferred embodiments of the present invention. However, as mentioned before, it should be understood that the present invention is not limited to the forms disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be changed within the scope of the application concept described herein through the above teachings or the techniques or knowledge in related fields. And the changes and alterations made by those skilled in the art without departing from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

1. A method for controlling the morphology of carbides during the solidification process of nickel-based superalloys, characterized in that, It includes the following steps: S1. Place the nickel-based superalloy raw material in a corundum crucible and heat it to a certain temperature in an electric resistance furnace, and keep it warm for a period of time to fully melt the raw material to obtain a melt; S2. During the continuous insulation of the melt, insert the electrode connected to the pulsed current generator into the melt and preheat it for a period of time; S3. Set the first pulse voltage, pulse current and pulse frequency output by the pulsed current generator according to the carbon content of the nickel-based superalloy raw material; S4. Set the second pulse voltage, pulse current and pulse frequency output by the pulsed current generator according to the different temperature ranges during the pulsed current treatment in the solidification process of the melt; S5. Insulate the melt obtained in S4 and continue to apply the second pulse voltage, pulse current and pulse frequency for a period of time. After the treatment is completed, turn off the electric resistance furnace and turn off the pulsed power supply. After the electric resistance furnace cools down to a certain temperature, take out the obtained sample from the electric resistance furnace and perform air cooling to obtain a nickel-based superalloy with changed carbide morphology.

2. The method according to claim 1, wherein The period of time in S1 is 30 min, and the period of time in S2 and S5 is 5 - 10 min.

3. The method according to claim 1 or 2, characterized in that, The carbon content of the nickel-based superalloy raw material is 0.03 - 0.12 wt.%.

4. The method according to claim 1, wherein The material of the electrode is graphite, and its bottom end is inserted to the bottom of the molten pool where the melt is located.

5. The method according to claim 1, characterized in that, The first pulse voltage is 5 - 36 V, the current intensity is 100 - 300 A, and the pulse frequency is 100 - 50000 Hz.

6. The method according to claim 1, wherein The certain temperature in S1 is 1400 - 1500 °C, and the certain temperature in S5 is 1250 °C - 1200 °C.

7. The method according to claim 3, wherein When the carbon content of the nickel-based superalloy raw material is [0.03, 0.05] wt.%, the first pulse frequency is [100, 1000] Hz, the current intensity is [140, 150] A, and the pulse voltage is [10, 20] V; When the carbon content of the nickel-based superalloy raw material is (0.05, 0.08] wt.%, the first pulse frequency is (1000, 10000] Hz, the current intensity is [100, 110] A, and the pulse voltage is (20, 30] V; When the carbon content of the nickel-based superalloy raw material is (0.08, 0.12] wt.%, the first pulse frequency is (10000, 50000] Hz, the current intensity is [80, 90] A, and the pulse voltage is (30, 36] V.

8. The method according to claim 1, wherein S4 is specifically: when performing pulsed current treatment in the temperature range of 1500 - 1450 °C, the second pulse voltage, pulse current and pulse frequency are all increased by 10 - 15% compared with the first pulse voltage, pulse current and pulse frequency; When performing holding electric pulse treatment in the temperature range of 1450 - 1350 °C, use the first pulse voltage, pulse current and pulse frequency; When performing holding electric pulse treatment in the temperature range of 1350 - 1250 °C, the second pulse voltage, pulse current and pulse frequency are all decreased by 10 - 15% compared with the first pulse voltage, pulse current and pulse frequency.

9. The method according to claim 1, wherein The air cooling rate in S5 is 10 °C - 50 °C / min.

10. A nickel-based superalloy, characterized in that, The nickel-based superalloy is prepared by the method described in any one of claims 1 - 9.

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