A nickel-based wrought superalloy, a turbine disk and a method of making the same

Abstract

This invention relates to a nickel-based wrought superalloy, a turbine disk, and a method for preparing the same, belonging to the field of high-temperature alloy design and preparation technology. The nickel-based wrought superalloy comprises the following chemical composition by weight percentage: Co: 16-20 wt%; Cr: 6.0-9.0 wt%; Ti: 2.0-3.0 wt%; Al: 4.0-6.0 wt%; W: 10.0-12.0 wt%; Mo: 0.5-2.5 wt%; Ta: 0.2-2.0 wt%; C: 0.08-0.16 wt%; Zr: 0.02-0.05 wt%; B: 0.02-0.05 wt%; Ni is the balance; wherein, in the nickel-based wrought superalloy, the sum of the weight percentages of Al, Ti, and Ta is ≥7.5 wt%; and the sum of the weight percentages of C, Zr, and B is ≤0.2 wt%. This invention is primarily used to design and manufacture a nickel-based wrought superalloy that not only possesses high thermal strength but also is machinable through casting and forging processes. This nickel-based wrought superalloy can be used to fabricate turbine disks with a maximum service temperature exceeding 850°C.

Description

Technical Field

[0001] This invention relates to the field of high-temperature alloy design and preparation technology, and in particular to a nickel-based wrought high-temperature alloy, a turbine disk and its preparation method. Background Technology

[0002] With the development and advancement of aerospace technology, the exit temperature of aero-engines is increasing, thus placing ever higher demands on the heat resistance of core hot-end components. Most wrought superalloys experience a significant decrease in strength above 800°C; and beyond 850°C, their strength remains low while their plasticity suffers. Although highly alloyed powder-formed superalloys can achieve excellent high-temperature strength, powder alloys are costly and have long preparation cycles. Therefore, there is an urgent need to invent a wrought superalloy with high heat resistance that can be prepared using casting and forging methods.

[0003] Currently, only GH4975 alloy (ЭЛ975) can withstand deformation high-temperature alloys above 850℃. However, this alloy has a high degree of alloying, serious ingot segregation, is difficult to prepare, has a low yield, and is prone to extremely uneven microstructure and properties.

[0004] Currently, the alloys and preparation technologies for turbine disks resistant to 850℃ are as follows: The first technology involves adding rare earth elements such as Ce, La, and Y to the GH4975 alloy to achieve excellent thermal strength. However, the presence of Nb increases the segregation of the ingot, hindering hot working. The second technology proposes a heat treatment method to improve the deformation capability of GH4975 alloy ingots. This method uses 1180℃ to homogenize the ingot before air cooling to room temperature. However, this method suffers from low homogenization diffusion temperature and rapid cooling rate, leading to poor homogenization and cracking during cooling. The third technology is based on electron beam melting to prepare an 850℃ resistant alloy. This alloy contains Hf, increasing cost. Furthermore, the high temperature and vacuum during electron beam melting cause significant volatilization of Cr and C, making it difficult to control and resulting in low preparation efficiency. The fourth technology designs a low-W, low-C alloy. While this alloy reduces segregation and is easier to process, it is detrimental to high-temperature strength.

[0005] In summary, there is an urgent need for a nickel-based wrought superalloy that not only possesses high thermal strength but also has the machinability of casting and forging processes, thus providing the necessary turbine disk material for high thrust-ratio engines. Summary of the Invention

[0006] In view of this, the present invention provides a nickel-based wrought superalloy, a turbine disk and a method for preparing the same, with the main objective of designing a nickel-based wrought superalloy that not only has high thermal strength but also is machinable by casting and forging processes.

[0007] To achieve the above objectives, the present invention mainly provides the following technical solutions:

[0008] On one hand, embodiments of the present invention provide a nickel-based wrought superalloy, wherein, by weight percentage, the nickel-based wrought superalloy comprises the following chemical composition:

[0009] Co: 16-20 wt%; Cr: 6.0-9.0 wt%; Ti: 2.0-3.0 wt%; Al: 4.0-6.0 wt%; W: 10.0-12.0 wt%; Mo: 0.5-2.5 wt%; Ta: 0.2-2.0 wt%; C: 0.08-0.16 wt%; Zr: 0.02-0.05 wt%; B: 0.02-0.05 wt%; Ni is the balance.

[0010] In the nickel-based wrought superalloy, the sum of the weight percentages of Al, Ti, and Ta is ≥7.5wt%; and the sum of the weight percentages of C, Zr, and B is ≤0.2wt%.

[0011] Preferably, the nickel-based wrought superalloy comprises the following chemical composition: Co: 18-20 wt%; Cr: 6.0-7.5 wt%; Ti: 2.0-2.7 wt%; Al: 4.5-6.0 wt%; W: 10.0-11.0 wt%; Mo: 0.5-1.2 wt%; Ta: 0.2-0.5 wt%; C: 0.10-0.16 wt%; Zr: 0.02-0.03 wt%; B: 0.02-0.03 wt%; Ni is the balance.

[0012] On the other hand, embodiments of the present invention also provide a method for preparing the above-mentioned nickel-based wrought superalloy, wherein the preparation method includes the following steps:

[0013] Vacuum induction melting step: The raw material is subjected to vacuum induction melting to obtain the first ingot;

[0014] Electroslag remelting step: Under a protective atmosphere, the first ingot is subjected to electroslag remelting treatment to obtain the second ingot;

[0015] Vacuum self-consumption smelting step: The second ingot is subjected to vacuum self-consumption smelting treatment to obtain a nickel-based deformed high-temperature alloy.

[0016] Preferably, before electroslag remelting the first ingot, annealing is required to promote the precipitation of precipitates at grain boundaries and inhibit intergranular cracking; preferably, the annealing temperature is 1140-1180℃ and the annealing time is 15-30h.

[0017] Preferably, before the second ingot is subjected to vacuum consumable metallurgy, it needs to be annealed to promote the precipitation of precipitate phase at the grain boundaries and inhibit intergranular cracking; preferably, the annealing temperature is 1140-1180℃ and the annealing time is 15-30h.

[0018] In another aspect, embodiments of the present invention provide a turbine disk, wherein the turbine disk is made of the aforementioned nickel-based wrought high-temperature alloy.

[0019] Preferably, in the microstructure of the turbine disk: the carbides at the grain boundaries are discontinuously distributed, and the grain size is 20-100 μm; preferably, the γ′ phase is distributed inside the grains; preferably, the γ′ phase content of the turbine disk is 55-65 wt%.

[0020] Preferably, the method for preparing the turbine disk includes the following steps:

[0021] Step 1): Prepare a nickel-based wrought superalloy using any of the above-described methods.

[0022] Step 2) The nickel-based deformed superalloy is subjected to diffusion annealing to eliminate solidification segregation in the alloy.

[0023] Step 3) Cool the diffusion-annealed nickel-based deformed superalloy to the billet deformation temperature and perform billet deformation treatment to obtain fine-grained rods;

[0024] Step 4) The fine-grained rod is subjected to isothermal forging to obtain a turbine disk blank;

[0025] Step 5) The turbine disk blank is subjected to solution treatment, rough machining and aging treatment in sequence to obtain the turbine disk.

[0026] Preferably, in step 2), the diffusion annealing temperature is 1210-1260℃ and the diffusion annealing time is 20-50h; and / or in step 3), the billet deformation temperature is 1150-1190℃; and / or in step 3), the billet deformation treatment is upsetting or hot extrusion; and / or; in step 4), the isothermal forging temperature is 1150-1190℃; and / or in step 5), the solution treatment temperature is 1210-1230℃ and the solution treatment time is 4-6h; and / or in step 5), the aging treatment temperature is 930-980℃ and the aging treatment time is 5-10h.

[0027] Preferably, the turbine disk has a yield strength ≥800MPa, tensile strength ≥850MPa, and elongation ≥5% at a temperature of 780-850℃; and / or the turbine disk has a creep rupture life ≥150h at 800℃±2℃ and 500MPa±2MPa; and / or the turbine disk has a creep rupture life ≥50h at 850℃±2℃ and 400MPa±2MPa.

[0028] Compared with the prior art, the nickel-based wrought superalloy, turbine disk, and preparation method of the present invention have at least the following beneficial effects:

[0029] On one hand, embodiments of the present invention provide a nickel-based wrought superalloy, which, by weight percentage, comprises the following chemical composition: Co: 16-20 wt%; Cr: 6.0-9.0 wt%; Ti: 2.0-3.0 wt%; Al: 4.0-6.0 wt%; W: 10.0-12.0 wt%; Mo: 0.5-2.5 wt%; Ta: 0.2-2.0 wt%; C: 0.08-0.16 wt%; Zr: 0.02-0.05 wt%; B: 0.02-0.05 wt%; Ni is the balance. The design of the above chemical composition is explained as follows: The present invention adds Al, Ti, and Ta elements, and controls Al+Ti+Ta ≥ 7.5 wt%. No Nb element is added to the alloy, which can reduce the segregation degree of the ingot and improve the homogeneity of the alloy billet. Meanwhile, the high carbon content in the alloy allows carbon to readily combine with sparingly soluble elements, forming dispersed carbides and reducing the segregation of these elements. Controlling the C+Zr+B content below 0.2 wt% prevents the formation of continuous thin-film carbides or borides at grain boundaries, which could reduce the alloy's ductility and toughness. Furthermore, the high Co and W content significantly reduces the alloy's stacking fault energy, making it more prone to twinning strengthening within its service temperature range, thus improving its thermal strength and creep resistance. Therefore, the nickel-based wrought superalloy designed in this invention not only possesses high thermal strength but also exhibits machinability through casting and forging processes.

[0030] On the other hand, this invention also provides a method for preparing a turbine disk. Using the aforementioned chemical composition-designed wrought high-temperature alloy and appropriate processes, a turbine disk with a maximum service temperature of over 850°C is prepared. Specifically: The preparation process involves conventional vacuum induction melting, protective atmosphere electroslag remelting, and vacuum arc remelting. No equipment modifications are required, reducing costs. Due to the high degree of alloying, based on the alloy's solution temperature, the first ingot after vacuum induction melting and the second ingot after electroslag remelting are annealed at 1140-1180°C for 15-30 hours to eliminate stress and precipitate a large amount of precipitate phase at grain boundaries to inhibit intergranular cracking and prevent electrode fracture due to excessive structural stress. The third ingot after vacuum arc remelting is then subjected to diffusion annealing at 1210-1260°C to eliminate solidification segregation in the alloy. After diffusion annealing, the deformed superalloy is cooled in the furnace to 1150-1200℃, and then subjected to multi-directional upsetting or hot extrusion to prepare fine-grained rods. These rods are then loaded and unloaded, heated to 1150-1190℃ for isothermal forging to obtain turbine disk blanks. A solution treatment at 1210-1230℃ for 4-6 hours is required, followed by air cooling or gas quenching to room temperature. Rough machining is then performed, followed by aging treatment at 930-980℃ for 5-10 hours, followed by air cooling or gas quenching to room temperature. This single-step aging process saves energy and improves the production efficiency of the alloy. The above process yields turbine disks with uniform microstructure, excellent creep resistance, and high strength even at 850℃.

[0031] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0032] Figure 1 Microstructure diagram of the turbine disk prepared in Example 1;

[0033] Figure 2 Grain boundary morphology diagram of the turbine disk prepared in Example 1;

[0034] Figure 3 Microstructure diagram of the turbine disk prepared in Example 2;

[0035] Figure 4 The grain boundary morphology diagram of the turbine disk prepared in Example 2;

[0036] Figure 5 Microstructure diagram of the turbine disk prepared in Example 3;

[0037] Figure 6The image shows the grain boundary morphology of the turbine disk prepared in Example 3;

[0038] Figure 7 Microstructure diagram of the turbine disk prepared for Comparative Example 1;

[0039] Figure 8 This is a microstructure diagram of the turbine disk prepared in Comparative Example 2;

[0040] Figure 9 This is a microstructure diagram of the turbine disk prepared in Comparative Example 3;

[0041] Figure 10 This is a microstructure diagram of the turbine disk prepared in Comparative Example 4. Detailed Implementation

[0042] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific embodiments, structures, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0043] The term "fine-grained rod" as used in this invention refers to rods with grain sizes of grade 8 or higher, or even below 10 μm.

[0044] The term "isothermal forging" as used in this invention refers to upsetting a billet (fine-grained bar) into a disc.

[0045] Currently, most wrought high-temperature alloy materials for turbine disks both domestically and internationally employ dual-stage (vacuum induction melting + vacuum consumable remelting) and triple-stage smelting processes (vacuum induction melting + protective atmosphere electroslag remelting + vacuum consumable remelting). This invention addresses engine requirements and, based on the current state of traditional triple-stage smelting equipment, develops a nickel-based wrought high-temperature alloy, a turbine disk, and its preparation method, thereby achieving a comprehensive improvement in the performance of turbine disk components.

[0046] The present invention provides a nickel-based wrought superalloy that not only possesses high thermal strength but also exhibits machinability through casting and forging, thus enabling it to provide the necessary turbine disk material for high thrust-to-weight ratio engines. The specific details of the present invention are as follows:

[0047] An embodiment of the present invention provides a nickel-based wrought superalloy, wherein, by weight percentage, the nickel-based wrought superalloy comprises the following chemical composition:

[0048] Co: 16-20 wt%; Cr: 6.0-9.0 wt%; Ti: 2.0-3.0 wt%; Al: 4.0-6.0 wt%; W: 10.0-12.0 wt%; Mo: 0.5-2.5 wt%; Ta: 0.2-2.0 wt%; C: 0.08-0.16 wt%; Zr: 0.02-0.05 wt%; B: 0.02-0.05 wt%; Ni is the balance; wherein, in the nickel-based wrought superalloy: the sum of the weight percentages of Al, Ti, and Ta is ≥7.5 wt%; the sum of the weight percentages of C, Zr, and B is ≤0.2 wt%.

[0049] The composition design of the wrought superalloy of this invention is explained below: This invention adds Al, Ti, and Ta elements to a nickel-based wrought superalloy, with Al+Ti+Ta ≥ 7.5wt%. No Nb element is added to the alloy, reducing the segregation degree of the ingot and improving the homogeneity of the alloy billet. Simultaneously, the alloy has a relatively high C content, as C easily combines with sparingly soluble elements to form dispersed carbides, further reducing the segregation degree of sparingly soluble elements. The C+Zr+B content is controlled below 0.2wt% to prevent the formation of continuous thin-film carbides or borides at grain boundaries, which would reduce the alloy's ductility and toughness.

[0050] Preferably, the nickel-based wrought superalloy comprises the following chemical composition: Co: 18-20 wt%; Cr: 6.0-7.5 wt%; Ti: 2.0-2.7 wt%; Al: 4.5-6.0 wt%; W: 10.0-11.0 wt%; Mo: 0.5-1.2 wt%; Ta: 0.2-0.5 wt%; C: 0.10-0.16 wt%; Zr: 0.02-0.03 wt%; B: 0.02-0.03 wt%; Ni is the balance.

[0051] Regarding the above-mentioned preferred contents, the following explanations are provided: Increasing the Co content helps reduce stacking fault energy, and increasing the Co content can introduce microtwin strengthening effects; the preferred Co content is 18-20 wt%. Due to the high degree of alloying in the designed alloy, excessive Cr content can easily form the TCP phase. However, Cr plays a role in high-temperature oxidation resistance in the alloy, so the preferred Cr content is 6-7.5 wt%. Although Ta is a γ′ phase forming element, its high density and high price mean it is used at the lower limit. The goal is to increase the Ti+Al content to ensure excellent thermal strength of the alloy. W and Mo play a solid solution strengthening role, but W is prone to segregation, so its content is used at the lower limit. C can form carbides, reducing element segregation and improving the alloy's yield. It also forms grain boundary carbides, improving the alloy's high-temperature creep resistance; therefore, C is used at the upper limit. Zr and B are grain boundary segregating elements, improving grain boundary bonding strength; both are used at the middle limit.

[0052] The preparation methods of the nickel-based wrought superalloy with the above-mentioned chemical composition and the turbine disk processed from the nickel-based wrought superalloy are mainly as follows:

[0053] Vacuum induction melting step: The raw material is subjected to vacuum induction melting to obtain the first ingot;

[0054] Electroslag remelting step: Under a protective atmosphere, the first ingot is subjected to electroslag remelting treatment to obtain the second ingot;

[0055] Vacuum self-consumption smelting step: The second ingot is subjected to vacuum self-consumption smelting treatment to obtain a nickel-based deformed high-temperature alloy.

[0056] Diffusion annealing: The nickel-based wrought superalloy is subjected to diffusion annealing to eliminate solidification segregation in the alloy;

[0057] Blanking deformation treatment: Cool the diffusion-annealed nickel-based deformed superalloy to the blanking deformation temperature and perform blanking deformation treatment to obtain fine-grained rods;

[0058] Isothermal forging: The fine-grained bar is subjected to isothermal forging to obtain a turbine disk blank;

[0059] Solution treatment and aging treatment: The turbine disk blank is subjected to solution treatment, rough machining treatment and aging treatment in sequence to obtain the turbine disk.

[0060] Here, it should be noted that the following steps are necessary: ​​The preparation process, involving conventional vacuum induction melting, protective atmosphere electroslag remelting, and vacuum arc remelting, requires no equipment modifications, thus reducing costs. Due to the high degree of alloying, based on the alloy's solution temperature, the first ingot after vacuum induction melting and the second ingot after electroslag remelting need to be annealed at 1140-1180℃ for 15-30 hours to relieve stress and precipitate a large amount of precipitate phase at grain boundaries to inhibit intergranular cracking and prevent electrode fracture due to excessive structural stress. The third ingot after vacuum arc remelting undergoes diffusion annealing at 1210-1260℃ to eliminate solidification segregation in the alloy. The diffused annealed high-temperature alloy is cooled in the furnace to 1150-1200℃, and then deformed into fine-grained rods through multi-directional upsetting or hot extrusion. These fine-grained rods are then loaded and unloaded, heated to 1150-1190℃ for isothermal forging to obtain turbine disk blanks. Solution treatment at 1210-1230℃ for 4-6 hours is required, followed by air cooling or gas quenching to room temperature. Then, rough machining is performed, and finally, aging treatment at 930-980℃ for 5-10 hours is carried out, followed by air cooling or gas quenching to room temperature. It should also be noted that the above diffusion annealing treatment has a good homogenization effect, and the slow cooling treatment coarsens the γ′ phase in the alloy, promoting recrystallization during subsequent hot deformation and inhibiting grain growth, thereby improving the alloy's hot plasticity, reducing deformation resistance, and solving hot working problems.

[0061] The turbine disk prepared by this invention has a γ′ phase content of 55-65 wt% at temperatures below 850°C. The turbine disk exhibits the following properties: yield strength ≥ 800 MPa, tensile strength ≥ 850 MPa, and elongation ≥ 5% at 850°C; and / or creep rupture life ≥ 150 h at 800°C and 500 MPa; and / or creep rupture life ≥ 50 h at 850°C and 400 MPa.

[0062] Compared with existing technologies, the nickel-based superalloy designed and prepared in this invention is a highly alloyed wrought superalloy, but it does not contain Nb or rare earth elements, thus reducing the degree of segregation. Since the addition of rare earth elements is difficult and has a low yield, and this invention does not contain rare earth elements, the preparation cost of the alloy is reduced. Furthermore, this invention uses Ta to achieve excellent solid solution strengthening and precipitation strengthening effects. The aging process after turbine disk forming adopts single-step aging, compared to the two-step aging of GH4795 alloy. This invention eliminates the intermediate aging holding time of 1000-1150℃ for 2-10 hours, and the final aging time is only 5-10 hours, saving energy and improving the efficiency of alloy production.

[0063] The present invention will be further illustrated below through specific experimental examples:

[0064] The chemical composition of the deformed high-temperature alloys in the following examples and comparative examples is shown in Table 1.

[0065] Table 1 (wt%)

[0066] alloy C Al B Cr Mo Ti W Nb Zr Co Ta Re Ni Example 1 0.12 5.0 0.03 9 2.5 3.0 12.0 -- 0.03 17 0.4 -- Remain Example 2 0.15 5.0 0.02 7.5 1.0 2.5 11.0 -- 0.02 18 0.3 -- Remain Example 3 0.16 6.0 0.02 6.0 0.5 2.0 10.0 -- 0.02 20 0.2 -- Remain Comparative Example 1 0.06 5.5 0.05 11 3.5 2.0 8.0 2.0 0.05 17.0 -- -- Remain Comparative Example 2 0.10 4.5 0.006 7.5 1.0 2.0 9.5 1.0 -- 14.0 -- 0.12 Remain Comparative Example 3 0.15 4.0 0.05 7.5 1.0 2.0 10.0 -- 0.05 18 0.2 -- Remain Comparative Example 4 0.15 5.0 0.02 7.5 1.0 2.5 11.0 -- 0.02 18 0.3 -- Remain

[0067] Example 1

[0068] This embodiment prepares a nickel-based wrought superalloy and a turbine disk, the chemical composition of which is shown in Table 1. The process includes the following steps:

[0069] Vacuum induction melting step: The raw material is subjected to vacuum induction melting to obtain the first ingot. Then, the first ingot is annealed at 1180℃ and held for 15 hours to relieve stress, so that a large amount of precipitate phase is precipitated at the grain boundaries to inhibit intergranular cracking and prevent fracture due to excessive structural stress.

[0070] Electroslag remelting step: Under a protective atmosphere, the first ingot is subjected to electroslag remelting to obtain a second ingot. Then, the second ingot is annealed at 1180℃ for 15 hours to relieve stress, so that a large amount of precipitated phase is precipitated at the grain boundaries to inhibit intergranular cracking and prevent fracture due to excessive structural stress.

[0071] Vacuum self-consumption smelting step: The second ingot is subjected to vacuum self-consumption smelting treatment to obtain a nickel-based deformed high-temperature alloy.

[0072] Diffusion annealing: The nickel-based wrought superalloy is subjected to diffusion annealing to eliminate solidification segregation in the alloy. The diffusion annealing temperature is 1210℃ and the time is 45h.

[0073] Blanking and Deformation Treatment: The diffusion-annealed nickel-based wrought superalloy is cooled to the blanking and deformation temperature and subjected to blanking and deformation treatment to obtain fine-grained rods. Specifically, the diffusion-annealed wrought superalloy is cooled to 1150°C in the furnace and then subjected to multi-directional upsetting and drawing blanking and deformation to prepare fine-grained rods.

[0074] Isothermal forging: Fine-grained rods are loaded and unloaded, heated to 1150℃ and isothermal forging is performed to obtain turbine disk blanks.

[0075] Solution treatment and aging treatment: The turbine disk blank is solution treated at 1210℃ for 6 hours and then air-cooled to room temperature; then rough machining is performed, and finally aging treatment is performed at 950℃ for 8 hours and air-cooled to room temperature to obtain the turbine disk.

[0076] The turbine disk prepared in this embodiment has a γ′ phase content of 60 wt% at temperatures below 850°C. The turbine disk exhibits the following properties: a yield strength of 820 MPa, a tensile strength of 881 MPa, and an elongation of 5% at 850°C; a creep rupture life of 185 hours at 800°C / 500 MPa and 60 hours at 850°C / 400 MPa.

[0077] Figure 1 Microstructure diagram of the turbine disk prepared in Example 1; Figure 2 The image shows the grain boundary morphology of the turbine disk prepared in Example 1; from Figure 1 and Figure 2 It can be seen that the average grain size of the alloy is 30 μm, and only a small amount of primary γ′ phase (γ′ phase with a size reaching the micrometer scale) exists in the alloy, with a size of about 1-3 μm; a large number of discontinuous M phases exist at the grain boundaries. 23 C6 carbides strengthen grain boundaries.

[0078] Example 2

[0079] This embodiment prepares a nickel-based wrought superalloy and a turbine disk, the chemical composition of which is shown in Table 1. The process includes the following steps:

[0080] Vacuum induction melting step: The raw material is subjected to vacuum induction melting to obtain the first ingot. Then, the first ingot is annealed at 1160℃ for 25 hours to relieve stress, so that a large amount of precipitate phase is precipitated at the grain boundaries to inhibit intergranular cracking and prevent fracture due to excessive structural stress.

[0081] Electroslag remelting step: Under a protective atmosphere, the first ingot is subjected to electroslag remelting to obtain a second ingot. Then, the second ingot is annealed at 1160℃ for 25 hours to relieve stress, so that a large amount of precipitated phase is precipitated at the grain boundaries to inhibit intergranular cracking and prevent fracture due to excessive structural stress.

[0082] Vacuum self-consumption smelting step: The second ingot is subjected to vacuum self-consumption smelting treatment to obtain a nickel-based deformed high-temperature alloy.

[0083] Diffusion annealing: The nickel-based wrought superalloy is subjected to diffusion annealing to eliminate solidification segregation in the alloy. The diffusion annealing temperature is 1240℃, and the time is 35 hours.

[0084] Blanking and Deformation Treatment: The diffusion-annealed nickel-based wrought superalloy is cooled to the blanking and deformation temperature and subjected to blanking and deformation treatment to obtain fine-grained rods. Specifically, the diffusion-annealed wrought superalloy is cooled to 1160°C in the furnace and then subjected to multi-directional upsetting and drawing blanking and deformation to prepare fine-grained rods.

[0085] Isothermal forging: Fine-grained rods are loaded and unloaded, heated to 1170℃ and isothermal forging is performed to obtain turbine disk blanks.

[0086] Solution treatment and aging treatment: The turbine disk blank is solution treated at 1220℃ for 5 hours and then air-cooled to room temperature; then rough machining is performed, and finally aging treatment is performed at 940℃ for 10 hours and air-cooled to room temperature to obtain the turbine disk.

[0087] The turbine disk prepared in this embodiment has a γ′ phase content of 62 wt% at temperatures below 850°C. The turbine disk exhibits the following properties: a yield strength of 835 MPa, a tensile strength of 885 MPa, and an elongation of 6% at 850°C; a creep rupture life of 220 h at 800°C / 500 MPa and 65 h at 850°C / 400 MPa.

[0088] Figure 3 Microstructure diagram of the turbine disk prepared in Example 2; Figure 4 The image shows the grain boundary morphology of the turbine disk prepared in Example 2; from Figure 3 and Figure 4 It can be seen that the average grain size of the alloy is 45 μm, and only a small amount of primary γ′ phase exists in the alloy, with a size of about 1-3 μm; a large number of discontinuous M phases exist at the grain boundaries. 23 C6 carbides strengthen grain boundaries.

[0089] Example 3

[0090] This embodiment prepares a nickel-based wrought superalloy and a turbine disk, the chemical composition of which is shown in Table 1. The process includes the following steps:

[0091] Vacuum induction melting step: The raw material is subjected to vacuum induction melting to obtain the first ingot. Then, the first ingot is annealed at 1150℃ for 30 hours to relieve stress, so that a large amount of precipitate phase is precipitated at the grain boundaries to inhibit intergranular cracking and prevent fracture due to excessive structural stress.

[0092] Electroslag remelting step: Under a protective atmosphere, the first ingot is subjected to electroslag remelting to obtain a second ingot. Then, the second ingot is annealed at 1150℃ for 30 hours to relieve stress, so that a large amount of precipitated phase is precipitated at the grain boundaries to inhibit intergranular cracking and prevent fracture due to excessive structural stress.

[0093] Vacuum self-consumption smelting step: The second ingot is subjected to vacuum self-consumption smelting treatment to obtain a nickel-based deformed high-temperature alloy.

[0094] Diffusion annealing: The nickel-based wrought superalloy is subjected to diffusion annealing to eliminate solidification segregation in the alloy. The diffusion annealing temperature is 1250℃, and the time is 25 hours.

[0095] Blanking and Deformation Treatment: The diffusion-annealed nickel-based wrought superalloy is cooled to the blanking and deformation temperature and subjected to blanking and deformation treatment to obtain fine-grained rods. Specifically, the diffusion-annealed wrought superalloy is cooled to 1190°C in the furnace and then subjected to multi-directional upsetting and drawing blanking and deformation to prepare fine-grained rods.

[0096] Isothermal forging: Fine-grained rods are loaded and unloaded, heated to 1190℃ and isothermal forging is performed to obtain turbine disk blanks.

[0097] Solution treatment and aging treatment: The turbine disk blank is solution treated at 1230℃ for 4 hours and then air-cooled to room temperature; then rough machining is performed, and finally aging treatment is performed at 930℃ for 10 hours and air-cooled to room temperature to obtain the turbine disk.

[0098] The turbine disk prepared in this embodiment has a γ′ phase content of 65 wt% at temperatures below 850°C. The turbine disk exhibits the following properties: a yield strength of 850 MPa, a tensile strength of 890 MPa, and an elongation of 6.5% at 850°C; a creep rupture life of 240 hours at 800°C / 500 MPa and 70 hours at 850°C / 400 MPa.

[0099] Figure 5 Microstructure diagram of the turbine disk prepared in Example 3; Figure 6 The image shows the grain boundary morphology of the turbine disk prepared in Example 3; from Figure 5 and Figure 6 It can be seen that the average grain size of the alloy is 40 μm, and only a small amount of primary γ′ phase exists in the alloy, with a size of about 1-5 μm; a large number of discontinuous M phases exist at the grain boundaries. 23 C6 carbides strengthen grain boundaries.

[0100] Comparative Example 1

[0101] Comparative Example 1 prepared a nickel-based wrought superalloy and a turbine disk, the chemical composition of which is shown in Table 1. The process included the following steps:

[0102] Vacuum induction melting step: The raw material is subjected to vacuum induction melting to obtain the first ingot. Then, the first ingot is annealed at a temperature of 1122℃.

[0103] Electroslag remelting step: Under a protective atmosphere, the first ingot is subjected to electroslag remelting to obtain a second ingot. Then, the second ingot is annealed at a temperature of 1020°C.

[0104] Vacuum self-consumption smelting step: The second ingot is subjected to vacuum self-consumption smelting treatment to obtain a nickel-based deformed high-temperature alloy.

[0105] Homogenization annealing: The nickel-based wrought superalloy is subjected to homogenization annealing treatment. The diffusion annealing treatment is carried out at a temperature of 1180℃ for 45 hours.

[0106] Blanking and deformation treatment: The homogenized annealed nickel-based deformed superalloy is upset and drawn at 1180℃ to prepare bars.

[0107] Isothermal forging: Fine-grained rods are loaded and unloaded, heated to 1150℃ and isothermal forging is performed to obtain turbine disk blanks.

[0108] Solution treatment and aging treatment: The turbine disk blank is solution treated at 1160℃ for 8 hours, then held at 1100℃ for 7 hours for intermediate aging treatment, and finally aged at 850℃ for 32 hours. After air cooling to room temperature, the turbine disk is obtained.

[0109] The turbine disk prepared in Comparative Example 1 had a γ′ phase content of 52 wt% at temperatures below 850°C. The turbine disk exhibited the following properties: a yield strength of 748 MPa, a tensile strength of 880 MPa, and an elongation of 6.0% at 850°C; a creep rupture life of 108 h at 800°C / 500 MPa and 30 h at 850°C / 400 MPa.

[0110] Figure 7 Microstructure diagram of the turbine disk prepared for Comparative Example 1, from Figure 7 It can be seen that the average grain size of the alloy reaches more than 80 μm. Due to the presence of Nb, the alloy is prone to segregation and easy to form MC carbides. Furthermore, the grain boundaries are straight and there are almost no precipitated phases at the grain boundaries. At the same time, since the γ′ phase is less than 60 wt%, the high-temperature strength of the alloy is not as good as that of the embodiment of the present invention.

[0111] Comparative Example 2

[0112] Comparative Example 2 prepared a nickel-based wrought superalloy and a turbine disk, the chemical composition of which is shown in Table 1. The process included the following steps:

[0113] Vacuum induction melting step: The raw material is subjected to vacuum induction melting to obtain the first ingot. Then, the first ingot is annealed at a temperature of 1152℃.

[0114] Electroslag remelting step: Under a protective atmosphere, the first ingot is subjected to electroslag remelting to obtain a second ingot. Then, the second ingot is annealed at a temperature of 1100°C.

[0115] Vacuum self-consumption smelting step: The second ingot is subjected to vacuum self-consumption smelting treatment to obtain a nickel-based deformed high-temperature alloy.

[0116] Homogenization annealing: The nickel-based wrought superalloy is subjected to homogenization annealing treatment. The diffusion annealing temperature is 1190℃.

[0117] Blanking and deformation treatment: The homogenized annealed nickel-based deformed superalloy is upset and drawn at 1170℃ to prepare bars.

[0118] Isothermal forging: Fine-grained rods are loaded and unloaded, heated to 1160℃ and isothermal forged to obtain turbine disk blanks.

[0119] Solution treatment and aging treatment: The turbine disk blank is solution treated at 1180℃ for 8 hours, then held at 1100℃ for 7 hours for intermediate aging treatment, and finally aged at 850℃ for 32 hours. After air cooling to room temperature, the turbine disk is obtained.

[0120] The turbine disk prepared in Comparative Example 2 had a γ′ phase content of 60 wt% at temperatures below 850℃. The turbine disk exhibited the following properties: a yield strength of 780 MPa, a tensile strength of 886 MPa, and an elongation of 5.0% at 850℃; a creep rupture life of 120 h at 800℃ / 500 MPa and 45 h at 850℃ / 400 MPa.

[0121] Figure 8 The microstructure of the turbine disk prepared in Comparative Example 2 shows that the average grain size of the alloy reaches more than 70 μm. Due to the presence of Nb, the alloy is prone to segregation and easily forms MC carbides. Some carbides are present at the grain boundaries. However, due to the relatively low content of γ′ phase and solid solution strengthening elements, the high-temperature strength of the alloy is not as good as that of the embodiment of the present invention.

[0122] Comparative Example 3

[0123] Comparative Example 3 prepared a nickel-based wrought superalloy and a turbine disk, the chemical composition of which is shown in Table 1 (its chemical composition does not meet the requirements of "the sum of the weight percentages of Al, Ti, and Ta elements ≥ 7.5 wt%; the sum of the weight percentages of C, Zr, and B elements ≤ 0.2 wt%" as described in this invention). The process includes the following steps:

[0124] Vacuum induction melting step: The raw material is subjected to vacuum induction melting to obtain the first ingot. Then, the first ingot is annealed at a temperature of 1160℃.

[0125] Electroslag remelting step: Under a protective atmosphere, the first ingot is subjected to electroslag remelting to obtain a second ingot. Then, the second ingot is annealed at a temperature of 1150°C.

[0126] Vacuum self-consumption smelting step: The second ingot is subjected to vacuum self-consumption smelting treatment to obtain a nickel-based deformed high-temperature alloy.

[0127] Homogenization annealing: The nickel-based wrought superalloy is subjected to homogenization annealing treatment. The diffusion annealing treatment is carried out at a temperature of 1220℃ for 40 hours.

[0128] Blanking and deformation treatment: The homogenized annealed nickel-based deformed superalloy is upset and drawn at 1160℃ to prepare bars.

[0129] Isothermal forging: Fine-grained rods are loaded and unloaded, heated to 1160℃ and isothermal forged to obtain turbine disk blanks.

[0130] Solution treatment and aging treatment: The turbine disk blank is solution treated at 1180℃ for 5 hours and then aged at 950℃ for 10 hours. After air cooling to room temperature, the turbine disk is obtained.

[0131] The turbine disk prepared in Comparative Example 3 had a γ′ phase content of 60 wt% at temperatures below 850℃. The turbine disk exhibited the following properties: a yield strength of 750 MPa, a tensile strength of 800 MPa, and an elongation of 5.0% at 850℃; a creep rupture life of 130 h at 800℃ / 500 MPa and 50 h at 850℃ / 400 MPa.

[0132] Figure 9 Microstructure diagram of the turbine disk prepared in Comparative Example 3, from Figure 9 It can be seen that the average grain size of the alloy reaches more than 35 μm. The alloy contains a large number of primary carbides, so the microstructure is relatively uneven. At the same time, there is a lack of carbide reinforcement at the grain boundaries, so the high temperature strength of the alloy is not as good as that of this application.

[0133] Comparative Example 4

[0134] Comparative Example 4 describes the preparation of a nickel-based wrought superalloy and a turbine disk. The chemical composition is shown in Table 1 (the chemical composition meets the composition range requirements of this invention, but some process parameters differ). The process includes the following steps:

[0135] Vacuum induction melting step: The raw material is subjected to vacuum induction melting to obtain the first ingot. Then, the first ingot is annealed at 1160℃ for 25 hours to relieve stress, so that a large amount of precipitate phase is precipitated at the grain boundaries to inhibit intergranular cracking and prevent fracture due to excessive structural stress.

[0136] Electroslag remelting step: Under a protective atmosphere, the first ingot is subjected to electroslag remelting to obtain a second ingot. Then, the second ingot is annealed at 1160℃ for 25 hours to relieve stress, so that a large amount of precipitated phase is precipitated at the grain boundaries to inhibit intergranular cracking and prevent fracture due to excessive structural stress.

[0137] Vacuum self-consumption smelting step: The second ingot is subjected to vacuum self-consumption smelting treatment to obtain a nickel-based deformed high-temperature alloy.

[0138] Diffusion annealing: The nickel-based wrought superalloy is subjected to diffusion annealing to eliminate solidification segregation in the alloy. The diffusion annealing temperature is 1240℃ and the time is 30h.

[0139] Blanking and Deformation Treatment: The diffusion-annealed nickel-based wrought superalloy is cooled to the blanking and deformation temperature and subjected to blanking and deformation treatment. Specifically, the diffusion-annealed wrought superalloy is subjected to multi-directional upsetting and drawing at 1140℃ to prepare bars.

[0140] Isothermal forging: The bar stock is loaded and unloaded, heated to 1130℃ for upsetting, and a turbine disk blank is obtained.

[0141] Solution treatment and aging treatment: The turbine disk blank is solution treated at 1170℃ for 5 hours and then air-cooled to room temperature; then rough machining is performed, and finally aging treatment is performed at 940℃ for 10 hours and air-cooled to room temperature to obtain the turbine disk.

[0142] The turbine disk prepared in this embodiment has a γ′ phase content of 60 wt% at temperatures below 850°C. The turbine disk exhibits the following properties: a yield strength of 795 MPa, a tensile strength of 835 MPa, and an elongation of 4% at 850°C; a creep rupture life of 100 hours at 800°C / 500 MPa and 25 hours at 850°C / 400 MPa.

[0143] Figure 10 The microstructure of the turbine disk prepared in Comparative Example 4 shows that the grains in the alloy are flat and contain a large number of carbide clusters, resulting in insufficient strengthening effect. Therefore, the high-temperature strength of the alloy is not as good as that of the embodiments of the present invention.

[0144] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a turbine disk, characterized in that, The turbine disk is made of a nickel-based wrought superalloy; the nickel-based wrought superalloy comprises the following chemical composition by weight percentage: Co: 18-20wt%; Cr: 6.0-7.5wt%; Ti: 2.0-2.7wt%; Al: 4.5-6.0wt%; W: 10.0-11.0wt%; Mo: 0.5-1.2wt%; Ta: 0.2-0.5wt%; C: 0.10-0.16wt% Zr: 0.02-0.03wt% B: 0.02-0.03 wt%; Ni is the balance; the nickel-based wrought superalloy does not contain Nb. Specifically, by ensuring that the sum of the weight percentages of Al, Ti, and Ta elements in the nickel-based wrought superalloy is ≥7.5wt% and that no Nb element is added, the segregation of the ingot can be reduced and the homogeneity of the alloy billet can be improved; the sum of the weight percentages of C, Zr, and B elements is ≤0.2wt% to prevent the formation of continuous thin film carbides or borides at the grain boundaries, which would reduce the plasticity and toughness of the alloy. The nickel-based wrought superalloy is prepared by the following method: Vacuum induction melting step: The raw material is subjected to vacuum induction melting to obtain the first ingot; Electroslag remelting step: Under a protective atmosphere, the first ingot is subjected to electroslag remelting treatment to obtain the second ingot; Vacuum consumable smelting step: The second ingot is subjected to vacuum consumable smelting treatment to obtain a nickel-based wrought high-temperature alloy; Before electroslag remelting the first ingot, annealing is performed to promote the precipitation of precipitates at grain boundaries and suppress intergranular cracking. Before the second ingot is subjected to vacuum arc remelting, it is annealed to promote the precipitation of precipitates at grain boundaries and inhibit intergranular cracking. The method for preparing the turbine disk includes the following steps: Step 1), using the above-described method for preparing nickel-based wrought superalloys, a nickel-based wrought superalloy is prepared; Step 2) The nickel-based deformed superalloy is subjected to diffusion annealing to eliminate solidification segregation in the alloy; wherein the diffusion annealing temperature is 1210-1260℃ and the diffusion annealing time is 20-50h. Step 3) The nickel-based deformed superalloy after diffusion annealing is cooled in the furnace to 1150-1200℃, and then subjected to billet deformation treatment by multi-directional upsetting or hot extrusion to obtain fine-grained rods; wherein the billet deformation temperature is 1150-1190℃. Step 4) The fine-grained rod is loaded and unloaded, heated to 1150-1190 ℃ for isothermal forging treatment to obtain turbine disk blank; Step 5) The turbine disk blank is subjected to solution treatment, rough machining and aging treatment in sequence to obtain the turbine disk; wherein the solution treatment temperature is 1210-1230℃ and the solution treatment time is 4-6h; the aging treatment temperature is 930-980℃ and the aging treatment time is 5-10h.

2. The method for preparing a turbine disk according to claim 1, characterized in that, The annealing treatment prior to electroslag remelting of the first ingot is performed at a temperature of 1140-1180°C for a duration of 15-30 hours.

3. The method for preparing a turbine disk according to claim 1, characterized in that, The annealing temperature before the second ingot is 1140-1180℃ and the annealing time is 15-30h.

4. A turbine disk, characterized in that, The turbine disk is prepared by the method of preparing a turbine disk according to any one of claims 1-3; wherein, in the microstructure of the turbine disk: the carbides at the grain boundaries are discontinuously distributed, and the grain size is 20-100μm; The γ′ phase is distributed inside the grains; The γ′ phase content of the turbine disk is 55-65 wt%.

5. The turbine disk according to claim 4, characterized in that, The turbine disk has a yield strength ≥800MPa, tensile strength ≥850MPa, and elongation ≥5% at a temperature of 780-850℃. The turbine disk has a service life of ≥150h under conditions of 800℃±2℃ and 500MPa±2MPa. The turbine disk has a service life of ≥50h under conditions of 850℃±2℃ and 400MPa±2MPa.

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