High-purity austenite nickel-based high-temperature alloy and production method thereof

Abstract

The invention discloses a high-purity austenite nickel-based high-temperature alloy and a preparation method thereof, and belongs to the technical field of metallurgy. The nickel-based high-temperature alloy comprises the following chemical components: 0.015-0.025% of C, less than or equal to 0.5% of Si, less than or equal to 0.50% of Mn, more than or equal to 58.0% of Ni, 28.5-31.0% of Cr, 9.0-11.0% of Fe, less than or equal to 0.10% of Nb + Ta, less than or equal to 0.05% of Cu and the balance of inevitable impurity elements. The production method comprises the working procedures of vacuum induction melting, electroslag remelting, gradient temperature control forging and heat treatment. Vacuum induction melting is combined with a double-stage deoxidation process, and electroslag remelting, gradient temperature control forging and customized heat treatment procedures of a CaF2: CaO: Al2O3: MgO: TiO2 novel slag system are adopted. Through precise design of alloy components and collaborative optimization of a preparation process, the alloy has excellent mechanical properties and corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to a high-purity austenitic nickel-based superalloy and its production method. Background Technology

[0002] Austenitic nickel-based superalloys are primarily used in aerospace engine combustion chambers, steam generators in nuclear power systems, high-temperature reactors in chemical equipment, and as manufacturing materials for high-end components in additive manufacturing. These alloys, with nickel as the matrix, maintain the stability of the face-centered cubic (FCC) austenitic structure at high temperatures through mechanisms such as solid solution strengthening, precipitation strengthening, and grain boundary strengthening. This allows for long-term service in the 600–1200℃ range, expanding the application limits of traditional materials under extreme high-temperature and high-pressure conditions. However, current mainstream nickel-based superalloys still face key technological bottlenecks in their preparation and application, severely restricting their reliability in extreme environments.

[0003] First, the purity of nickel-based alloys is difficult to control. While traditional vacuum induction melting can control the oxygen content to around 10%,... -6 While the surface area is relatively stable, microscopic inclusions such as Al2O3 and MgO are still difficult to completely remove. When the size of these inclusions exceeds 8 μm, the crease life of the alloy under 900℃ / 100MPa conditions drops sharply from 3000h to 800h. Conventional single-stage deoxidation processes cannot stably control the oxygen content below 20ppm, becoming a major cause of crack initiation. Secondly, elemental segregation is difficult to avoid. Segregation of elements such as Cr and Nb between dendrites causes significant unevenness in local corrosion resistance and mechanical properties. Related studies have shown that the Cr content in the interdendritic region of the as-cast alloy can fluctuate by ±4%, resulting in a 3-fold increase in its corrosion rate. Local enrichment of Nb easily induces the precipitation of the Laves brittle phase, deteriorating high-temperature plasticity. Furthermore, nickel-based alloys have poor forging formability. Traditional forging processes usually use constant temperature and constant speed parameters, resulting in a difference of more than 15% in deformation between thick-walled and thin-walled regions and a grain size difference of more than 30%, causing stress concentration during subsequent heat treatment and inducing early cracking. Finally, the slag system lacks stability during electroslag remelting. The existing CaF2-CaO-Al2O3 slag system has a wide high-temperature viscosity control window and insufficient adsorption capacity for non-metallic inclusions. At the same time, due to the absence of TiO2 component, the lack of TiO2 synergistic effect makes it difficult to effectively suppress the oxidation loss of Ti elements, thereby weakening the corrosion resistance of the alloy.

[0004] To address the aforementioned technical problems, this invention proposes a comprehensive technical solution. By introducing a two-stage deoxidation process, gradient temperature-controlled forging technology, and a novel CaF2-CaO-Al2O3-MgO-TiO2 slag system, the total O+N content is reduced to below 30ppm and the inclusion size is controlled to ≤5μm while maintaining the high-temperature strength of the material. This provides key process support for promoting the engineering application of next-generation nickel-based superalloys. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a high-purity austenitic nickel-based superalloy and its production method. The austenitic nickel-based alloy obtained by the method of the present invention has uniform composition, high purity and excellent performance.

[0006] A high-purity austenitic nickel-based superalloy, wherein the chemical composition and mass percentage of the nickel-based superalloy are as follows: C: 0.015~0.025%, Si≤0.5%, Mn≤0.50%, Ni≥58.0%, Cr: 28.5~31.0%, Fe: 9.0~11.0%, Nb+Ta≤0.10%, Cu≤0.05%, with the remainder being unavoidable impurities.

[0007] The nickel-based superalloy of this invention has the following room temperature properties: tensile strength ≥720MPa, yield strength ≥240MPa, elongation after fracture ≥45%, and surface hardness ≥170HB; the mechanical properties of the nickel-based superalloy meet the following requirements: tensile strength at 600℃ ≥510MPa, creep rupture life at 800℃ / 50MPa ≥2500h; total O+N content of the nickel-based superalloy <20ppm, and corrosion rate in 65% nitric acid ≤0.35mm / a.

[0008] The nickel-based superalloy of the present invention has a single-phase austenitic face-centered cubic (FCC) structure with a γ' phase (Ni3Al) of 50-100 nm in size dispersed within the grains. There are no carbide or Laves phase brittle phase precipitation at the grain boundaries. The average grain size is 8-12 μm and the inclusion size is ≤5 μm. The microstructure has excellent uniformity.

[0009] Another object of the present invention is to provide a method for producing the above-mentioned austenitic nickel-based superalloy, comprising vacuum induction melting, electroslag remelting, gradient temperature-controlled forging, and heat treatment processes; the specific control steps are as follows: (1) Vacuum induction melting process: a two-stage deoxidation process is adopted. First, carbon powder is added for carbon deoxidation, and after 5 minutes, nano aluminum powder is added for aluminothermic reduction. The oxygen partial pressure is controlled at 1.5-2.0 Pa. (2) Electroslag remelting: A new slag system of CaF2-CaO-Al2O3-MgO-TiO2 is adopted, wherein the mass ratio of Al2O3 / TiO2 is controlled at 1.5 to 2.0; (3) Gradient temperature control forging: Adjust the process parameters according to the thickness of the forging. The forging temperature of the thick-walled area with a thickness ≥ 50 mm is 950~1000℃ and the anvil pressing speed is 3~5 mm / s. The forging temperature of the thin-walled area with a thickness < 50 mm is 900~950℃ and the anvil pressing speed is 1~3 mm / s. (4) Heat treatment: Solution treatment and aging treatment are carried out in sequence. Solution treatment is to heat the forging material from room temperature to 1000-1150℃ and hold it for 2-2.5 hours. Aging treatment is to hold it at 700-750℃ for 1-1.5 hours after forging.

[0010] In step (1) of the present invention, the amount of carbon powder added is 0.01 to 0.015% of the alloy mass, and the amount of nano aluminum powder added is 0.02 to 0.03% of the alloy mass.

[0011] In step (1) of the present invention, argon is blown into the bottom throughout the vacuum induction melting process. The argon flow rate is 30-40 L / min in the early stage and 50-60 L / min in the later stage. The casting and tapping temperature is controlled at 180-230°C above the liquidus temperature, and the tapping time is controlled at 3-6 min.

[0012] In step (2) of the present invention, the chemical composition and mass percentage of the novel slag system are as follows: CaF2: 50-55%, CaO: 5.75-18%, Al2O3: 18-22.75%, MgO: 2-4%, TiO2: 10-13%.

[0013] In step (2) of the present invention, the viscosity of the slag system is controlled at 0.9 to 1.2 Pa·s; the slag formation period is 20V / 3000-3500A and the remelting period is 25V / 4000-4500A.

[0014] Before the gradient temperature-controlled forging described in this invention, the forging is homogenized and annealed at 1200-1250℃ for 4-6 hours. The heating rate during the annealing process is 30-40℃ / h, the single deformation is 12-25%, and the total deformation is ≥50%. After forging, it is air-cooled to room temperature.

[0015] In step (4) of the present invention, the heat treatment rate is 480-720℃ / h for solution heating and 10-20℃ / h for furnace cooling after aging.

[0016] The beneficial effects of adopting the above technical solution are as follows: 1. The high-purity austenitic nickel-based superalloy and its production method of the present invention have significant advantages. The composition precisely controls the proportion of elements such as C and Cr, strictly controls the content of impurities such as Nb+Ta and Cu, and is combined with a high-nickel matrix of Ni≥58.0%, laying the foundation for performance. 2. In the production of the present invention, the novel slag system of vacuum induction dual-stage deoxidation + electroslag remelting is used to achieve an oxygen content ≤15ppm and an inclusion size ≤5μm, which greatly improves the purity. Gradient temperature-controlled forging and customized heat treatment are matched to refine the grains to 8-12μm, promote the dispersion precipitation of 50-100nm γ' phase, and eliminate brittle phases such as carbides at the grain boundaries. 3. This invention exhibits the following performance characteristics: room temperature tensile strength ≥720MPa, elongation after fracture ≥45%, tensile strength at 600℃ ≥510MPa, creep rupture life at 800℃ / 50MPa ≥2500h, and corrosion rate in 65% nitric acid <0.35mm / a. It balances strength, toughness, high-temperature stability, and corrosion resistance. Compared to traditional alloys, its compositional uniformity, microstructure stability, and overall performance are comprehensively optimized, making it suitable for harsh high-temperature and corrosive conditions and promising broad application prospects. Attached Figure Description

[0017] Figure 1 Example 1: Metallographic structure of an austenitic nickel-based alloy; Figure 2 Example 1: Microstructure of the γ' phase in an austenitic nickel-based alloy. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to specific embodiments.

[0019] A method for producing high-purity austenitic nickel-based superalloys includes four core processes: vacuum induction melting, electroslag remelting, gradient temperature-controlled forging, and heat treatment. The specific control steps are as follows: (1) Vacuum induction melting: Furnace charging: Metallic Cr (≥99.5%), pure iron (≥99.9%), and electrolytic nickel (≥99.95%) are charged into the crucible in the specified proportions; nano-aluminum powder (≥99.9%) and carbon powder (≥99.9%) are charged into the top hopper for deoxidation. Oxygen partial pressure control: The actual oxygen partial pressure is controlled at 1.5–2.0 Pa. Two-stage deoxidation: In the first stage, 0.01–0.015% carbon powder is added to react with oxygen to generate CO; after 5 minutes, in the second stage, 0.02–0.03% nano-aluminum powder is added to completely remove residual oxygen; bottom blowing with argon gas is used throughout the process (30–40 L / min in the early stage and 50–60 L / min in the later stage). The tapping temperature is controlled at 180–230℃ above the liquidus, and the tapping time is 3–6 minutes.

[0020] (2) Electroslag remelting: The new slag system formula adopts a CaF2:CaO:Al2O3:MgO:TiO2 slag system with the following mass percentages: CaF2: 50-55%, CaO: 5.75-18%, Al2O3: 18-22.75%, MgO: 2-4%, TiO2: 10-13%; wherein the Al2O3 / TiO2 ratio is controlled at 1.5-2.0. The actual viscosity is controlled at 0.9-1.2 Pa·s. The voltage is 20V and the current is 3000-3500A during the slag formation period; the voltage is 25V and the current is 4000-4500A during the remelting period; and the voltage is 20V during the feeding period to ensure that the slag layer uniformly covers the molten steel.

[0021] (3) Gradient temperature controlled forging: Homogenization annealing: Hold at 1200–1250℃ for 4–6 hours, with a heating rate of 30–40℃ / h, to eliminate dendritic segregation in the ingot. Gradient process parameters: Adjust according to the thickness difference of the forging. Thick-walled area (≥50mm): forging temperature 950–1000℃, anvil pressing speed 3–5mm / s; Thin-walled area (<50mm): forging temperature 900–950℃, anvil pressing speed 1–3mm / s; single deformation amount 12–25%, total deformation amount ≥50%, air cool to room temperature after forging.

[0022] (4) Heat treatment: Solution treatment: The forging is heated from room temperature to 1000–1150℃ at a rate of 480–720℃ / h and held for 2–2.5h to dissolve excess carbides and strengthening phases. Aging treatment: After forging, the forging is held at 700–750℃ for 1–1.5h to promote uniform precipitation of the γ' phase; then it is furnace cooled to room temperature at a rate of 10–20℃ / h to eliminate forging stress. Example 1

[0023] A method for producing high-purity austenitic nickel-based superalloys includes four core processes: vacuum induction melting, electroslag remelting, gradient temperature-controlled forging, and heat treatment. The specific control steps are as follows: (1) Vacuum induction melting: Vacuum induction melting: Charging: Metallic Cr (≥99.5%), pure iron (≥99.9%), and electrolytic nickel (≥99.95%) are charged into the crucible in proportion; nano aluminum powder (≥99.9%) and carbon powder (≥99.9%) are charged into the top hopper for deoxidation. Oxygen partial pressure control: The oxygen partial pressure is actually controlled at 1.5 Pa. Two-stage deoxidation: In the first stage, 0.01% carbon powder is added to react with oxygen to generate CO; after 5 min, 0.02% nano aluminum powder is added in the second stage to completely remove residual oxygen; argon gas is blown from the bottom throughout the process (30 L / min in the early stage and 50 L / min in the later stage), the tapping temperature is controlled at 180℃ above the liquidus, and the tapping time is 3 min.

[0024] (2) Electroslag remelting: New slag system formula: CaF2:CaO:Al2O3:MgO:TiO2 slag system is adopted, with the following mass percentages: CaF2: 50%, CaO: 18%, Al2O3: 18%, MgO: 2%, TiO2: 12%; wherein the Al2O3 / TiO2 ratio is controlled at 1.5. The viscosity is actually controlled at 0.9 Pa·s. The voltage is 20V and the current is 3000A during the slag formation period; the voltage is 25V and the current is 4000A during the remelting period; and the voltage is 20V during the feeding period to ensure that the slag layer uniformly covers the molten steel.

[0025] (3) Gradient temperature control forging: Homogenization annealing: 1200℃ for 4h, heating rate 30℃ / h, to eliminate dendritic segregation in the ingot. Gradient process parameters: adjusted according to the thickness difference of the forging. Thick wall area (≥50mm): forging temperature 950℃, anvil pressing speed 3mm / s; thin wall area (<50mm): forging temperature 900℃, anvil pressing speed 1mm / s; single deformation amount 12%, total deformation amount 50%, air cooling to room temperature after forging.

[0026] (4) Heat treatment: Solution treatment: The forging is heated from room temperature to 1000℃ at a rate of 480℃ / h and held for 2h to dissolve excess carbides and strengthening phases. Aging treatment: After forging, it is held at 700℃ for 1h to promote uniform precipitation of γ' phase; then it is furnace cooled to room temperature at a rate of 10℃ / h to eliminate forging stress. Example 2

[0027] A method for producing high-purity austenitic nickel-based superalloys includes four core processes: vacuum induction melting, electroslag remelting, gradient temperature-controlled forging, and heat treatment. The specific control steps are as follows: (1) Vacuum induction melting: Charging: Metallic Cr (≥99.5%), pure iron (≥99.9%), and electrolytic nickel (≥99.95%) are charged into the crucible in proportion; nano-aluminum powder (≥99.9%) and carbon powder (≥99.9%) are charged into the top hopper for deoxidation. Oxygen partial pressure control: The oxygen partial pressure is actually controlled at 2.0 Pa. Two-stage deoxidation: In the first stage, 0.015% carbon powder is added to react with oxygen to generate CO; after 5 min, 0.03% nano-aluminum powder is added in the second stage to completely remove residual oxygen; argon gas is blown from the bottom throughout the process (40 L / min in the early stage and 60 L / min in the later stage). The tapping temperature is controlled at 230℃ above the liquidus, and the tapping time is 6 min.

[0028] (2) Electroslag remelting: New slag system formula: CaF2:CaO:Al2O3:MgO:TiO2 slag system is adopted, with the following mass percentages: CaF2: 55%, CaO: 7.2%, Al2O3: 20.8%, MgO: 4%, TiO2: 13%; wherein the Al2O3 / TiO2 ratio is controlled at 1.6. The viscosity is actually controlled at 1.2 Pa·s. The voltage is 20V and the current is 3500A during the slag formation period; the voltage is 25V and the current is 4500A during the remelting period; and the voltage is 20V during the feeding period to ensure that the slag layer uniformly covers the molten steel.

[0029] (3) Gradient temperature control forging: Homogenization annealing: 1250℃ for 6h, heating rate 40℃ / h, to eliminate dendritic segregation in the ingot. Gradient process parameters: adjusted according to the thickness difference of the forging. Thick wall area (≥50mm): forging temperature 1000℃, anvil pressing speed 5mm / s; thin wall area (<50mm): forging temperature 950℃, anvil pressing speed 3mm / s; single deformation amount 25%, total deformation amount 60%, air cooling to room temperature after forging.

[0030] (4) Heat treatment: Solution treatment: The forging is heated from room temperature to 1150℃ at a rate of 720℃ / h and held for 2.5h to dissolve excess carbides and strengthening phases. Aging treatment: After forging, it is held at 750℃ for 1.5h to promote uniform precipitation of γ' phase; then it is furnace cooled to room temperature at a rate of 20℃ / h to eliminate forging stress. Example 3

[0031] A method for producing high-purity austenitic nickel-based superalloys includes four core processes: vacuum induction melting, electroslag remelting, gradient temperature-controlled forging, and heat treatment. The specific control steps are as follows: (1) Vacuum induction melting: Charging: Metallic Cr (≥99.5%), pure iron (≥99.9%), and electrolytic nickel (≥99.95%) are charged into the crucible in proportion; nano-aluminum powder (≥99.9%) and carbon powder (≥99.9%) are charged into the top hopper for deoxidation. Oxygen partial pressure control: The oxygen partial pressure is actually controlled at 1.75 Pa. Two-stage deoxidation: In the first stage, 0.0125% carbon powder is added to react with oxygen to generate CO; after 5 min, 0.025% nano-aluminum powder is added in the second stage to completely remove residual oxygen; argon gas is blown from the bottom throughout the process (35 L / min in the early stage and 55 L / min in the later stage). The tapping temperature is controlled at 205℃ above the liquidus line, and the tapping time is 4.5 min.

[0032] (2) Electroslag remelting: New slag system formula: CaF2:CaO:Al2O3:MgO:TiO2 slag system is adopted, with the following mass percentages: CaF2: 51%, CaO: 13%, Al2O3: 21%, MgO: 3%, TiO2: 12%; wherein the Al2O3 / TiO2 ratio is controlled at 1.75. The viscosity is actually controlled at 1.05 Pa·s. The voltage is 20V and the current is 3250A during the slag formation period; the voltage is 25V and the current is 4250A during the remelting period; and the voltage is 20V during the feeding period to ensure that the slag layer uniformly covers the molten steel.

[0033] (3) Gradient temperature control forging: Homogenization annealing: 1225℃ for 5h, heating rate 35℃ / h, to eliminate dendritic segregation in the ingot. Gradient process parameters: adjusted according to the thickness difference of the forging. Thick wall area (≥50mm): forging temperature 975℃, anvil pressing speed 4mm / s; thin wall area (<50mm): forging temperature 925℃, anvil pressing speed 2mm / s; single deformation amount 18.5%, total deformation amount 55%, air cooling to room temperature after forging.

[0034] (4) Heat treatment: The forging is heated from room temperature to 1075℃ at a rate of 600℃ / h and held for 2.25h to dissolve excess carbides and strengthening phases. Aging treatment: After forging, it is held at 725℃ for 1.25h to promote uniform precipitation of γ' phase; then it is furnace cooled to room temperature at a rate of 15℃ / h to eliminate forging stress. Example 4

[0035] A method for producing high-purity austenitic nickel-based superalloys includes four core processes: vacuum induction melting, electroslag remelting, gradient temperature-controlled forging, and heat treatment. The specific control steps are as follows: (1) Vacuum induction melting: Charging: Metallic Cr (≥99.5%), pure iron (≥99.9%), and electrolytic nickel (≥99.95%) are charged into the crucible in proportion; nano-aluminum powder (≥99.9%) and carbon powder (≥99.9%) are charged into the top hopper for deoxidation. Oxygen partial pressure control: The oxygen partial pressure is actually controlled at 1.6 Pa. Two-stage deoxidation: In the first stage, 0.011% carbon powder is added to react with oxygen to generate CO; after 5 min, 0.022% nano-aluminum powder is added in the second stage to completely remove residual oxygen; argon gas is blown from the bottom throughout the process (32 L / min in the early stage and 52 L / min in the later stage). The tapping temperature is controlled at 190℃ above the liquidus line, and the tapping time is 3.5 min.

[0036] (2) Electroslag remelting: New slag system formula: CaF2:CaO:Al2O3:MgO:TiO2 slag system is adopted, with the following mass percentages: CaF2: 52%, CaO: 14%, Al2O3: 20.9%, MgO: 2.1%, TiO2: 11%; wherein the Al2O3 / TiO2 ratio is controlled at 1.9. The viscosity is actually controlled at 0.95 Pa·s. The voltage is 20V and the current is 3100A during the slag formation period; the voltage is 25V and the current is 4100A during the remelting period; and the voltage is 20V during the feeding period to ensure that the slag layer uniformly covers the molten steel.

[0037] (3) Gradient temperature control forging: Homogenization annealing: 1210℃ for 4.5h, heating rate 32℃ / h, to eliminate dendritic segregation in the ingot. Gradient process parameters: adjusted according to the thickness difference of the forging. Thick wall area (≥50mm): forging temperature 960℃, anvil pressing speed 3.5mm / s; thin wall area (<50mm): forging temperature 910℃, anvil pressing speed 1.5mm / s; single deformation amount 14%, total deformation amount 52%, air cooling to room temperature after forging.

[0038] (4) Heat treatment: The forging is heated from room temperature to 1030℃ at a rate of 550℃ / h and held for 2.1h to dissolve excess carbides and strengthening phases. Aging treatment: After forging, it is held at 710℃ for 1.1h to promote uniform precipitation of γ' phase; then it is furnace cooled to room temperature at a rate of 13℃ / h to eliminate forging stress. Example 5

[0039] A method for producing high-purity austenitic nickel-based superalloys includes four core processes: vacuum induction melting, electroslag remelting, gradient temperature-controlled forging, and heat treatment. The specific control steps are as follows: (1) Vacuum induction melting: Charging: Metallic Cr (≥99.5%), pure iron (≥99.9%), and electrolytic nickel (≥99.95%) are charged into the crucible in proportion; nano-aluminum powder (≥99.9%) and carbon powder (≥99.9%) are charged into the top hopper for deoxidation. Oxygen partial pressure control: The oxygen partial pressure is actually controlled at 1.9 Pa. Two-stage deoxidation: In the first stage, 0.014% carbon powder is added to react with oxygen to generate CO; after 5 min, 0.028% nano-aluminum powder is added in the second stage to completely remove residual oxygen; argon gas is blown from the bottom throughout the process (38 L / min in the early stage and 58 L / min in the later stage), and the final oxygen content of the molten steel is 9 ppm. The tapping temperature is controlled at 220℃ above the liquidus line, and the tapping time is 5.5 min.

[0040] (2) Electroslag remelting: New slag system formula: CaF2:CaO:Al2O3:MgO:TiO2 slag system is adopted, with the following mass percentages: CaF2: 54.25%, CaO: 5.75%, Al2O3: 24%, MgO: 4%, TiO2: 12%; wherein the Al2O3 / TiO2 ratio is controlled at 2.0. The viscosity is actually controlled at 1.15 Pa·s. The voltage is 20V and the current is 3400A during the slag formation period; the voltage is 25V and the current is 4400A during the remelting period; and the voltage is 20V during the feeding period to ensure that the slag layer uniformly covers the molten steel.

[0041] (3) Gradient temperature control forging: Homogenization annealing: 1240℃ for 5.5h, heating rate 38℃ / h, to eliminate dendritic segregation in the ingot. Gradient process parameters: adjusted according to the thickness difference of the forging. Thick wall area (≥50mm): forging temperature 990℃, anvil pressing speed 4.5mm / s; thin wall area (<50mm): forging temperature 940℃, anvil pressing speed 2.5mm / s; single deformation amount 22%, total deformation amount 58%, air cooling to room temperature after forging.

[0042] (4) Heat treatment: The forging is heated from room temperature to 1020℃ at a rate of 680℃ / h and held for 2.4h to dissolve excess carbides and strengthening phases. Aging treatment: After forging, it is held at 740℃ for 1.4h to promote uniform precipitation of γ' phase; then it is furnace cooled to room temperature at a rate of 18℃ / h to eliminate forging stress.

[0043] The performance testing of the austenitic nickel-based alloys produced in Examples 1-5 was conducted as follows: Chemical composition was determined using a direct-reading spectrometer. Tensile strength, yield strength, and elongation after fracture at room temperature and 600℃ were tested using a high-temperature tensile testing machine. Surface hardness at room temperature was measured using a Brinell hardness tester. Creep life at 800℃ / 50MPa was tested using a high-temperature creep testing machine. Corrosion rate in 65% nitric acid was calculated using the weight loss method, by weighing the mass difference of the samples before and after corrosion using an electronic balance. γ' phase size and average grain size were observed using transmission electron microscopy (TEM) and scanning electron microscopy (SEM), and measured using Image-Pro image analysis software; inclusion size was detected using ASPEX inclusion automatic scanning electron microscopy. All tests ensured data accuracy and repeatability, meeting the requirements for alloy performance characterization. The chemical composition results of the austenitic nickel-based alloys in Examples 1-5 are shown in Table 1, the room temperature mechanical properties are shown in Table 2, and the high-temperature mechanical properties are shown in Table 3.

[0044] Table 1 Chemical composition of austenitic nickel-based alloys in Examples 1-5

[0045] Table 2 Room temperature mechanical properties of austenitic nickel-based alloys in Examples 1-5

[0046] Table 3 High-Temperature Mechanical Properties of Austenitic Nickel-Based Alloys in Examples 1-5

[0047] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-purity austenitic nickel-based superalloy, characterized in that, The chemical composition and mass percentage of the nickel-based superalloy are as follows: C: 0.015~0.025%, Si≤0.5%, Mn≤0.50%, Ni≥58.0%, Cr: 28.5~31.0%, Fe: 9.0~11.0%, Nb+Ta≤0.10%, Cu≤0.05%, with the remainder being unavoidable impurities.

2. The high-purity austenitic nickel-based superalloy according to claim 1, characterized in that, The nickel-based superalloy has the following room temperature properties: tensile strength ≥720MPa, yield strength ≥240MPa, elongation after fracture ≥45%, and surface hardness ≥170HB; the mechanical properties of the nickel-based superalloy meet the following requirements: tensile strength at 600℃ ≥510MPa, creep rupture life at 800℃ / 50MPa ≥2500h; total O+N content of the nickel-based superalloy <20ppm, and corrosion rate in 65% nitric acid ≤0.35mm / a.

3. The high-purity austenitic nickel-based superalloy according to claim 1, characterized in that, The microstructure of the nickel-based superalloy is a single-phase austenitic face-centered cubic (FCC) structure with a γ' phase Ni3Al dispersed within the grains at a size of 50-100 nm. There are no carbide or Laves brittle phase precipitates at the grain boundaries. The average grain size is 8-12 μm, and the inclusion size is ≤5 μm.

4. A method for producing a high-purity austenitic nickel-based superalloy according to any one of claims 1-3, characterized in that, The production method includes vacuum induction melting, electroslag remelting, gradient temperature controlled forging, and heat treatment processes; the specific control steps are as follows: (1) Vacuum induction melting: A two-stage deoxidation process is adopted. First, carbon powder is added for carbon deoxidation, and after 5 minutes, nano aluminum powder is added for aluminothermic reduction. The oxygen partial pressure is controlled at 1.5 to 2.0 Pa. (2) Electroslag remelting: A new slag system of CaF2-CaO-Al2O3-MgO-TiO2 is adopted, wherein the mass ratio of Al2O3 / TiO2 is controlled at 1.5 to 2.0; (3) Gradient temperature control forging: Adjust the process parameters according to the thickness of the forging. The forging temperature of the thick-walled area with a thickness ≥ 50 mm is 950~1000℃ and the anvil pressing speed is 3~5 mm / s. The forging temperature of the thin-walled area with a thickness < 50 mm is 900~950℃ and the anvil pressing speed is 1~3 mm / s. (4) Heat treatment: Solution treatment and aging treatment are carried out in sequence. Solution treatment is to heat the forging material from room temperature to 1000-1150℃ and hold it for 2-2.5 hours. Aging treatment is to hold it at 700-750℃ for 1-1.5 hours after forging.

5. The method for producing an austenitic nickel-based superalloy according to claim 4, characterized in that, In step (1), the amount of carbon powder added is 0.01 to 0.015% of the alloy mass, and the amount of nano-aluminum powder added is 0.02 to 0.03% of the alloy mass.

6. The method for producing an austenitic nickel-based superalloy according to claim 4, characterized in that, In step (1), argon gas is blown from the bottom throughout the vacuum induction melting process. The argon gas flow rate is 30-40 L / min in the early stage and 50-60 L / min in the later stage. The casting and tapping temperature is controlled at 180-230℃ above the liquidus temperature, and the tapping time is controlled at 3-6 min.

7. A method for producing an austenitic nickel-based superalloy according to any one of claims 4-6, characterized in that, In step (2), the chemical composition and mass percentage of the new slag system are as follows: CaF2: 50-55%, CaO: 5.75-18%, Al2O3: 18-22.75%, MgO: 2-4%, TiO2: 10-13%.

8. A method for producing an austenitic nickel-based superalloy according to any one of claims 4-6, characterized in that, In step (2) of electroslag remelting, the viscosity of the slag system is controlled at 0.9 to 1.2 Pa·s; the slag formation period is 20V / 3000-3500A and the remelting period is 25V / 4000-4500A.

9. A method for producing an austenitic nickel-based superalloy according to any one of claims 4-6, characterized in that, Before the gradient temperature-controlled forging, the forging is homogenized and annealed at 1200-1250℃ for 4-6 hours. The heating rate during the annealing process is 30-40℃ / h, the single deformation is 12-25%, and the total deformation is ≥50%. After forging, it is air-cooled to room temperature.

10. A method for producing an austenitic nickel-based superalloy according to any one of claims 4-6, characterized in that, In step (4) heat treatment, the solution heating rate is 480-720℃ / h and the furnace cooling rate after aging is 10-20℃ / h.

Images