An aerospace, difficult-to-deform, nickel-based, high-temperature alloy rod and a method of making the same

Abstract

The application is suitable for the alloy material processing technical field, and provides an aerospace difficult-to-deform nickel-based high-temperature alloy rod and a preparation method thereof.The preparation method comprises the following steps: S1, triple smelting to prepare an ingot; S2, pulse current assisted multi-stage homogenization treatment: pulse current is applied at three temperature stages to perform homogenization; S3, stepwise temperature control forging: the lower limit of the surface temperature of the blank is controlled in the multi-pass forging process, and the blank is returned to the furnace for temperature compensation when the surface temperature decreases to the lower limit; S4, radial forging forming; S5, two-stage deformation heat treatment: after radial forging, post-forging deformation treatment is performed, and then solid solution and two-stage aging treatment are performed.The application shortens the treatment cycle through pulse current assisted homogenization, improves the yield of the finished product by controlling the temperature difference between the surface and the core of the blank through multi-stage temperature control forging, and realizes synergistic gain of fine-grain strengthening and precipitation strengthening through two-stage deformation heat treatment.The prepared alloy rod has a room temperature tensile strength of greater than or equal to 1640 MPa and a 750 DEG C / 620 MPa endurance life of greater than or equal to 108 h.

Description

Technical Field

[0001] This invention relates to the field of alloy material processing technology, and in particular to a difficult-to-deform nickel-based high-temperature alloy bar for aerospace applications and its preparation method. Background Technology

[0002] Difficult-to-deform nickel-based superalloys are a class of nickel-based wrought superalloys that are precipitation-strengthened with the γ′ phase as the main strengthening phase. These alloys possess excellent high-temperature strength, creep resistance, fatigue resistance, and oxidation corrosion resistance, making them key materials for manufacturing core hot-end components such as turbine disks, turbine blades, and combustion chambers of aero-engines. With the continuous increase in the thrust-to-weight ratio of aero-engines, turbine inlet temperatures are constantly rising, placing higher demands on the temperature resistance of alloys. To meet the service requirements above 800℃, high-γ′ phase wrought superalloys such as GH4151, GH4175, and GH4975 have been developed both domestically and internationally. Among them, the total mass fraction of age-hardening elements Al, Ti, and Nb in the GH4151 alloy is as high as approximately 10%, and the volume fraction of the γ′ phase is as high as 54%; the mass fraction of the γ′ phase in the GH4975 alloy can even reach as high as 64%.

[0003] High γ′ phase content, while imparting excellent high-temperature performance, also presents significant challenges to the preparation process—significantly increasing the alloy's deformation resistance, noticeably decreasing its thermoplasticity, and narrowing the hot working window, making it highly susceptible to cracking and microstructural instability during hot deformation. In recent years, my country has conducted extensive research on the preparation processes of difficult-to-deform nickel-based superalloys. For example, CN113231589A discloses a forging method to improve the microstructure uniformity of difficult-to-deform nickel-based superalloys. This method utilizes multi-stage forging on a high-speed forging mill combined with narrow-temperature zone control to improve the microstructure uniformity of the bar stock. CN117488221B discloses a method for homogenizing iron-nickel-based superalloy ingots during blanking. This method combines primary homogenization treatment, short-time high-temperature homogenization, and narrow-temperature zone successive cooling forging to address the problem of coarse or inhomogeneous microstructure often found in existing large-size iron-nickel-based superalloy ingots after blanking.

[0004] Although existing technologies have made some progress in smelting and forging, significant shortcomings remain. On the one hand, homogenization treatment still relies primarily on traditional hot-field diffusion, resulting in long processing cycles, high energy consumption, and insufficient effectiveness in eliminating strongly segregated elements such as W, Mo, and Nb. Residual dendritic segregation and low-melting-point eutectic phases easily become crack initiation points during subsequent hot working. On the other hand, the control of the temperature difference between the billet surface and core during forging remains relatively crude. For large-diameter bars, the surface temperature drops much faster than the core, easily leading to coarse grains and microcracks at the edges. Furthermore, existing forging processes mostly employ flat-anvil forging throughout, resulting in imprecise control of deformation between forging cycles. The critical deformation for complete recrystallization is relatively large, and the penetration of plastic deformation in the core is poor, leading to insufficient dynamic recrystallization in the core and further exacerbating the extreme grain size difference between the core and edges.

[0005] In conclusion, the existing technology obviously has inconveniences and defects in practical use, so it is necessary to improve it. Summary of the Invention

[0006] To address the aforementioned shortcomings, the present invention aims to overcome the technical defects in existing difficult-to-deform nickel-based superalloy preparation processes, such as low homogenization efficiency, poor uniformity of forging structure, and separation between deformation and heat treatment, and to provide a method for preparing difficult-to-deform nickel-based superalloy bars for aerospace applications.

[0007] To achieve the above objectives, the present invention provides a method for preparing a difficult-to-deform nickel-based superalloy bar for aerospace applications, comprising the following steps:

[0008] S1 Tri-Smelting Preparation of Ingots: Weigh the alloy raw materials and use a triple smelting process of vacuum induction melting, protective atmosphere electroslag remelting and vacuum consumable remelting to obtain consumable ingots.

[0009] S2 Pulse Current Assisted Multi-Stage Homogenization Treatment: Under the assistance of pulse current, the consumable ingot is subjected to multi-stage temperature-controlled homogenization diffusion annealing treatment to obtain a homogenized ingot.

[0010] S3 stepped temperature-controlled forging: The homogenized ingot is forged in multiple forging cycles. During each forging cycle, the surface temperature of the billet is controlled to be above the lower limit of the set surface temperature for that cycle. When the surface temperature of the billet drops to the lower limit of the set surface temperature, it is returned to the furnace for reheating to obtain the bar after billet opening.

[0011] S4 radial forging: After the billet is heated, it is subjected to multiple radial forgings to obtain the radially forged bar.

[0012] S5 dual-stage deformation heat treatment: After heating the forged bar to subsolid temperature and holding it at that temperature, it first undergoes post-forging deformation treatment, followed by solution treatment and dual-stage aging treatment.

[0013] As a further improvement, in step S1, the alloy raw materials, by mass fraction, include: Cr 9.0~12.0%, Co 14.0~17.0%, W 9.0~11.0%, Mo 0.8~1.5%, Al 4.8~5.5%, Ti 2.2~3.2%, Nb 1.0~2.0%, C 0.06~0.12%, B 0.015~0.035%, Zr 0.02~0.06%, Ce 0.005~0.020%, Mg 0.002~0.008%, with the balance being Ni and unavoidable impurities.

[0014] As a further improvement, in step S1, the vacuum induction melting includes three stages: melting, refining, and tapping. The melting vacuum degree is 0~1 Pa, the melting temperature is 1500~1550℃, the refining vacuum degree is 0~1 Pa, the refining temperature is 1500~1550℃, the refining time is 60~90 min, and the tapping temperature is 1450~1480℃. During the protective atmosphere electroslag remelting process, Ar is introduced for protection, the Ar flow rate is 30~50 L / min, and the remelting rate is controlled at 3.0~5.0 kg / min. The vacuum consumable remelting controls the vacuum degree to be 0~0.1 Pa and the remelting rate to be 3.0~6.0 kg / min.

[0015] As a further improvement, in step S2, the specific process of pulse current-assisted multi-stage homogenization is as follows:

[0016] (a) Heat to 850-950℃ at a rate of 50-100℃ / h, hold for 10-20 h, and apply a pulsed current density of 10-50 A / cm. 2 Frequency 50~500 Hz, duty cycle 30~70%;

[0017] (b) Increase the temperature to 1180-1200℃ at a rate of 30-80℃ / h, hold for 30-50 h, and apply a pulsed current density of 5-30 A / cm. 2 Frequency 100~1000 Hz, duty cycle 20~60%;

[0018] (c) Cool to 1160-1180℃ at a rate of 40-60℃ / h, hold for 10-20 h, and apply a pulsed current density of 5-20 A / cm. 2 Frequency 50~500 Hz, duty cycle 20~50%;

[0019] For large-sized ingots, pulsed current is applied in segments along the ingot axis to ensure that the uniformity of the current density distribution across the ingot cross section does not exceed ±10%.

[0020] As a further improvement, the specific process of the stepped temperature-controlled forging in step S3 is as follows:

[0021] (a) First forging: Heat to 1180~1200℃, hold for 2~6 h, upsetting and drawing, control the billet surface temperature to 1150~1200℃, final forging temperature to 1100±5℃, deformation amount to 20~30%;

[0022] (b) Second forging: Heat to 1160~1180℃, hold for 2~6 h, upsetting and drawing, control the billet surface temperature to 1130~1180℃, final forging temperature to 1080±5℃, deformation amount to 25~35%;

[0023] (c) Third forging: Heat to 1140~1160℃, hold for 2~6 h, upsetting and drawing, control the billet surface temperature to 1110~1160℃, final forging temperature to 1080±5℃, deformation amount to 20~30%;

[0024] The total forging ratio for each heat is 6~8; when the surface temperature of the billet drops to the lower limit of the set surface temperature for that heat, it is returned to the furnace for reheating. The reheating temperature is the heating temperature of that heat, and the reheating time is 0.5~2 hours. The number of times the billet is returned to the furnace for reheating in a single heat should not exceed 3 times to avoid repeated alternation of hot and cold temperatures, which would exacerbate thermal fatigue.

[0025] As a further improvement, in step S4, the heating temperature for radial forging is 1120~1160℃, the deformation amount per pass is 15~25%, and the final forging temperature is 1050±5℃.

[0026] As a further improvement, the specific process of the two-stage deformation heat treatment in step S5 is as follows:

[0027] (a) Post-forging deformation treatment: Heat the radially forged bar to 1080~1120℃, hold for 1~3 h, and perform 10~20% compression deformation at a deformation rate of 0.01~0.1 s. -1 ;

[0028] (b) Solution treatment: Temperature 1110~1160℃, hold for 1~4 h, then air cool;

[0029] (c) First-level aging treatment: temperature 760~800℃, heat preservation for 8~20 h, air cooling;

[0030] (d) Secondary aging treatment: temperature 650~720℃, heat preservation for 8~16 h, air cooling.

[0031] Another objective of this invention is to provide a difficult-to-deform nickel-based high-temperature alloy rod for aerospace applications, prepared using the aforementioned method. The alloy rod has an average grain size of grade 7, a γ′ phase volume fraction of 50-60%, a room temperature tensile strength of 1640-1680 MPa, a room temperature yield strength of 1210-1255 MPa, a 750℃ tensile strength of 1230-1270 MPa, a 750℃ yield strength of 1085-1120 MPa, and a 750℃ / 620 MPa creep rupture life of 108-118 h.

[0032] In summary, the beneficial effects of the present invention are as follows:

[0033] 1. Pulsed Current Assisted Multi-Stage Homogenization Treatment: Based on traditional multi-stage homogenization, pulsed current external field assistance is introduced; the electroplastic effect and Joule heating effect generated by the pulsed current can significantly enhance the atomic diffusion ability of segregated elements such as W, Mo, and Nb, thereby increasing the segregation elimination efficiency by 30-50% and shortening the homogenization time; at the same time, the periodic oscillation of the pulsed current can promote the dissolution of low-melting-point phases between dendrites and the redistribution of elements, effectively avoiding the grain coarsening caused by traditional long-term high-temperature homogenization.

[0034] 2. Stepped temperature-controlled forging: Breaking through the traditional extensive mode of "heating-forging-returning", a strategy for controlling the lower limit of surface temperature during each forging process is established; by segmented temperature control and timely temperature replenishment, the temperature difference between the surface and the core of the billet is controlled within 50℃, effectively suppressing the generation of coarse grains and microcracks at the edges; combined with the strategy of decreasing temperature in three forging cycles (1190℃→1170℃→1150℃) and increasing deformation (20~30%→25~35%→20~30%), the gradual refinement of grains and uniformity of microstructure are achieved.

[0035] 3. Two-stage deformation heat treatment: Breaking the traditional separation between forging and heat treatment, 10-20% of post-forging deformation treatment is introduced before solution treatment. This deformation treatment is carried out in the temperature range (1080-1120℃) where the γ′ phase is not completely dissolved. It can introduce an appropriate amount of dislocations and subgrain boundaries, providing nucleation sites for recrystallization in subsequent solution treatment, thereby obtaining finer recrystallized grains. At the same time, the dislocations introduced by deformation can serve as non-uniform nucleation sites for the γ′ phase, promoting the dispersed precipitation of the γ′ phase during aging, and achieving a synergistic gain of fine grain strengthening and precipitation strengthening. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Non-essential improvements and adjustments made by those skilled in the art based on the above description are still within the scope of protection of this invention.

[0037] Example 1 This example uses the following alloy raw materials (mass percentage, wt%): Cr 10.5%, Co 15.5%, W 10.0%, Mo 1.2%, Al 5.2%, Ti 2.6%, Nb 1.5%, C 0.09%, B 0.025%, Zr 0.04%, Ce 0.010%, Mg 0.005%, with the balance being Ni and unavoidable impurities (O≤0.0030%, N≤0.0020%, S≤0.0015%, P≤0.0015%).

[0038] This embodiment provides a method for preparing a difficult-to-deform nickel-based superalloy bar for aerospace applications, comprising the following steps:

[0039] S1 triple smelting process for ingot preparation

[0040] Raw materials were weighed according to the alloy composition ratio, and consumable ingots were prepared using a three-stage smelting process of “vacuum induction melting (VIM) + protective atmosphere electroslag remelting (PESR) + vacuum arc remelting (VAR)”.

[0041] Vacuum Induction Melting (VIM): The materials are batched according to the above element ratio. Ni, Cr, Co, W, and Mo are charged into the vacuum induction melting furnace for melting. After complete melting, refining is carried out. Al, Ti, Nb, C, B, Zr, and Mg are added in the later stage of refining. The rare earth element Ce is added in one go in the form of Ni-Ce master alloy after refining and 12 minutes before casting. The vacuum degree is controlled at 0.8 Pa and the melting temperature is 1530℃ during melting. The vacuum degree is controlled at 0.8 Pa and the refining temperature is 1530℃ during refining. The refining time is 75 minutes. During tapping, the melt temperature is reduced to 1460℃ and cast into consumable electrode rods under vacuum.

[0042] Electroslag Remelting (PESR): VIM ingots are used as consumable electrodes and electroslag remelted under a protective atmosphere to obtain electroslag remelted ingots; Ar is introduced for protection during the process, with an Ar flow rate of 40 L / min and a remelting rate of 4.0 kg / min.

[0043] Vacuum self-consumption remelting (VAR): ESR ingots are subjected to vacuum self-consumption remelting, with the vacuum level controlled at 0.08 Pa and the remelting rate at 4.5 kg / min.

[0044] S2 pulse current assisted multi-stage homogenization processing

[0045] (a) The temperature was increased to 900℃ at a rate of 80℃ / h and held for 15 h, while a pulsed current was applied with a pulsed current density of 30 A / cm. 2 The pulse frequency is 200 Hz and the duty cycle is 50%.

[0046] (b) The temperature was increased to 1190℃ at a rate of 50℃ / h and held for 40 h, while a pulsed current was applied with a pulsed current density of 15 A / cm². 2 The pulse frequency is 500 Hz and the duty cycle is 40%.

[0047] (c) Cool to 1170℃ at a rate of 50℃ / h, hold for 15 h, and simultaneously apply a pulsed current with a pulsed current density of 10 A / cm². 2 The pulse frequency is 200 Hz and the duty cycle is 30%.

[0048] After homogenization, the oxide layer and dealloyed layer on the surface of the consumable ingot are removed by turning, with a turning depth of ≥3~5 mm on one side.

[0049] S3 stepped temperature controlled forging

[0050] (a) First forging: The ingot is heated to 1190°C and held for 4 hours before upsetting and drawing. During forging, the surface temperature of the billet is controlled at 1150~1190°C, the final forging temperature is 1100°C, and the deformation is 25%.

[0051] (b) Second forging: The billet is heated to 1170°C, held for 4 hours, and then upset and drawn. During the forging process, the surface temperature of the billet is controlled at 1130~1170°C, the final forging temperature is 1080°C, and the deformation is 30%.

[0052] (c) Third forging: The billet is heated to 1150℃, held for 4 hours, and then upset and drawn. During the forging process, the surface temperature of the billet is controlled at 1110~1150℃, the final forging temperature is 1080℃, and the deformation is 25%.

[0053] The total forging ratio for each firing is 7. During each firing process, when the surface temperature of the billet drops to the lower limit of the surface temperature control for that firing, it is immediately returned to the furnace for reheating. The reheating temperature is the heating temperature for that firing, and the reheating time is 1 hour.

[0054] S4 radial forging

[0055] After the billet is heated to 1140℃, it is then subjected to multi-pass radial forging using a radial forging machine. The deformation amount in each pass is controlled at 20%, and the final forging temperature is 1050℃.

[0056] S5 Dual-Stage Deformation Heat Treatment

[0057] (a) Post-forging deformation treatment: The radially forged bar is heated to 1100℃ and held for 2 h, then subjected to 15% compression deformation, with the deformation rate controlled at 0.05 s. -1 ;

[0058] (b) Solution treatment: Heat the deformed bar to 1130°C, hold for 2 hours, and then air cool;

[0059] (c) Two-stage aging treatment: The first stage of aging involves heating the forged bar to 780°C, holding it at that temperature for 16 hours, and then air-cooling it to room temperature after it is taken out of the furnace; the second stage of aging involves heating the forged bar to 700°C, holding it at that temperature for 12 hours, and then air-cooling it to room temperature after it is taken out of the furnace.

[0060] Example 2 This example uses the following alloy raw materials (mass percentage, wt%): Cr 9.0%, Co 14.0%, W 9.0%, Mo 0.8%, Al 4.8%, Ti 2.2%, Nb 1.0%, C 0.06%, B 0.015%, Zr 0.02%, Ce 0.005%, Mg 0.002%, with the balance being Ni and unavoidable impurities (O≤0.0030%, N≤0.0020%, S≤0.0015%, P≤0.0015%).

[0061] This embodiment provides a method for preparing a difficult-to-deform nickel-based superalloy bar for aerospace applications, comprising the following steps:

[0062] S1 triple smelting process for ingot preparation

[0063] Raw materials were weighed according to the alloy composition ratio, and consumable ingots were prepared using a three-stage smelting process of “vacuum induction melting (VIM) + protective atmosphere electroslag remelting (PESR) + vacuum arc remelting (VAR)”.

[0064] Vacuum Induction Melting (VIM): The materials are batched according to the above element ratio. Ni, Cr, Co, W, and Mo are charged into the vacuum induction melting furnace for melting. After complete melting, refining is carried out. Al, Ti, Nb, C, B, Zr, and Mg are added in the later stage of refining. The rare earth element Ce is added in one go in the form of Ni-Ce master alloy after refining and 12 minutes before casting. The vacuum degree is controlled at 0.8 Pa and the melting temperature is 1530℃ during melting. The vacuum degree is controlled at 0.8 Pa and the refining temperature is 1530℃ during refining. The refining time is 75 minutes. During tapping, the melt temperature is reduced to 1460℃ and cast into consumable electrode rods under vacuum.

[0065] Electroslag Remelting (PESR): VIM ingots are used as consumable electrodes and electroslag remelted under a protective atmosphere to obtain electroslag remelted ingots; Ar is introduced for protection during the process, with an Ar flow rate of 40 L / min and a remelting rate of 4.0 kg / min.

[0066] Vacuum self-consumption remelting (VAR): ESR ingots are subjected to vacuum self-consumption remelting, with the vacuum level controlled at 0.08 Pa and the remelting rate at 4.5 kg / min.

[0067] S2 pulse current assisted multi-stage homogenization processing

[0068] (a) The temperature was increased to 900℃ at a rate of 80℃ / h and held for 15 h, while a pulsed current was applied with a pulsed current density of 30 A / cm. 2 The pulse frequency is 500 Hz and the duty cycle is 60%.

[0069] (b) The temperature was increased to 1190℃ at a rate of 50℃ / h and held for 40 h, while a pulsed current was applied with a pulsed current density of 15 A / cm². 2 The pulse frequency is 800 Hz and the duty cycle is 50%.

[0070] (c) Cool to 1170℃ at a rate of 50℃ / h, hold for 15 h, and simultaneously apply a pulsed current with a pulsed current density of 10 A / cm². 2 The pulse frequency is 400 Hz and the duty cycle is 40%.

[0071] After homogenization, the oxide layer and dealloyed layer on the surface of the consumable ingot are removed by turning, with a turning depth of ≥3~5 mm on one side.

[0072] S3 stepped temperature controlled forging

[0073] (a) First forging: The ingot is heated to 1190°C and held for 4 hours before upsetting and drawing. During forging, the surface temperature of the billet is controlled at 1150~1190°C, the final forging temperature is 1100°C, and the deformation is 25%.

[0074] (b) Second forging: The billet is heated to 1170°C, held for 4 hours, and then upset and drawn. During the forging process, the surface temperature of the billet is controlled at 1130~1170°C, the final forging temperature is 1080°C, and the deformation is 30%.

[0075] (c) Third forging: The billet is heated to 1150℃, held for 4 hours, and then upset and drawn. During the forging process, the surface temperature of the billet is controlled at 1110~1150℃, the final forging temperature is 1080℃, and the deformation is 25%.

[0076] The total forging ratio for each firing is 6. During each firing process, when the surface temperature of the billet drops to the lower limit of the surface temperature control for that firing, it is immediately returned to the furnace for reheating. The reheating temperature is the heating temperature for that firing, and the reheating time is 1 hour.

[0077] S4 radial forging

[0078] After the billet is heated to 1140℃, it is then subjected to multi-pass radial forging using a radial forging machine. The deformation amount in each pass is controlled at 20%, and the final forging temperature is 1050℃.

[0079] S5 Dual-Stage Deformation Heat Treatment

[0080] (a) Post-forging deformation treatment: The radially forged bar is heated to 1100℃ and held for 2 h, then subjected to 15% compression deformation, with the deformation rate controlled at 0.05 s. -1 ;

[0081] (b) Solution treatment: Heat the deformed bar to 1130°C, hold for 2 hours, and then air cool;

[0082] (c) Two-stage aging treatment: The first stage of aging involves heating the forged bar to 780°C, holding it at that temperature for 16 hours, and then air-cooling it to room temperature after it is taken out of the furnace; the second stage of aging involves heating the forged bar to 700°C, holding it at that temperature for 12 hours, and then air-cooling it to room temperature after it is taken out of the furnace.

[0083] Example 3. This example uses the following alloy raw materials (mass percentage, wt%): Cr 12.0%, Co 17.0%, W 11.0%, Mo 1.5%, Al 5.5%, Ti 3.2%, Nb 2.0%, C 0.12%, B 0.035%, Zr 0.06%, Ce 0.020%, Mg 0.008%, with the balance being Ni and unavoidable impurities (O≤0.0030%, N≤0.0020%, S≤0.0015%, P≤0.0015%).

[0084] This embodiment provides a method for preparing a difficult-to-deform nickel-based superalloy bar for aerospace applications, comprising the following steps:

[0085] S1 triple smelting process for ingot preparation

[0086] Raw materials were weighed according to the alloy composition ratio, and consumable ingots were prepared using a three-stage smelting process of “vacuum induction melting (VIM) + protective atmosphere electroslag remelting (PESR) + vacuum arc remelting (VAR)”.

[0087] Vacuum Induction Melting (VIM): The materials are batched according to the above element ratio. Ni, Cr, Co, W, and Mo are charged into the vacuum induction melting furnace for melting. After complete melting, refining is carried out. Al, Ti, Nb, C, B, Zr, and Mg are added in the later stage of refining. The rare earth element Ce is added in one go in the form of Ni-Ce master alloy after refining and 12 minutes before casting. The vacuum degree is controlled at 0.8 Pa and the melting temperature is 1530℃ during melting. The vacuum degree is controlled at 0.8 Pa and the refining temperature is 1530℃ during refining. The refining time is 75 minutes. During tapping, the melt temperature is reduced to 1460℃ and cast into consumable electrode rods under vacuum.

[0088] Electroslag Remelting (PESR): VIM ingots are used as consumable electrodes and electroslag remelted under a protective atmosphere to obtain electroslag remelted ingots; Ar is introduced for protection during the process, with an Ar flow rate of 40 L / min and a remelting rate of 4.0 kg / min.

[0089] Vacuum self-consumption remelting (VAR): ESR ingots are subjected to vacuum self-consumption remelting, with the vacuum level controlled at 0.08 Pa and the remelting rate at 4.5 kg / min.

[0090] S2 pulse current assisted multi-stage homogenization processing

[0091] (a) The temperature was increased to 900℃ at a rate of 80℃ / h and held for 15 h, while a pulsed current was applied with a pulsed current density of 30 A / cm. 2 The pulse frequency is 200 Hz and the duty cycle is 50%.

[0092] (b) The temperature was increased to 1190℃ at a rate of 50℃ / h and held for 40 h, while a pulsed current was applied with a pulsed current density of 15 A / cm². 2 The pulse frequency is 500 Hz and the duty cycle is 40%.

[0093] (c) Cool to 1170℃ at a rate of 50℃ / h, hold for 15 h, and simultaneously apply a pulsed current with a pulsed current density of 10 A / cm². 2 The pulse frequency is 200 Hz and the duty cycle is 30%.

[0094] After homogenization, the oxide layer and dealloyed layer on the surface of the consumable ingot are removed by turning, with a turning depth of ≥3~5 mm on one side.

[0095] S3 stepped temperature controlled forging

[0096] (a) First forging: The ingot is heated to 1190°C and held for 4 hours before upsetting and drawing. During forging, the surface temperature of the billet is controlled at 1150~1190°C, the final forging temperature is 1100°C, and the deformation is 25%.

[0097] (b) Second forging: The billet is heated to 1170°C, held for 4 hours, and then upset and drawn. During the forging process, the surface temperature of the billet is controlled at 1130~1170°C, the final forging temperature is 1080°C, and the deformation is 30%.

[0098] (c) Third forging: The billet is heated to 1150℃, held for 4 hours, and then upset and drawn. During the forging process, the surface temperature of the billet is controlled at 1110~1150℃, the final forging temperature is 1080℃, and the deformation is 25%.

[0099] The total forging ratio for each firing is 8. During each firing process, when the surface temperature of the billet drops to the lower limit of the surface temperature control for that firing, it is immediately returned to the furnace for reheating. The reheating temperature is the heating temperature for that firing, and the reheating time is 1.5 hours.

[0100] S4 radial forging

[0101] After the billet is heated to 1140℃, it is then subjected to multi-pass radial forging using a radial forging machine. The deformation amount in each pass is controlled at 20%, and the final forging temperature is 1050℃.

[0102] S5 Dual-Stage Deformation Heat Treatment

[0103] (a) Post-forging deformation treatment: The radially forged bar is heated to 1100℃ and held for 2 h, then subjected to 15% compression deformation, with the deformation rate controlled at 0.05 s. -1 ;

[0104] (b) Solution treatment: Heat the deformed bar to 1130°C, hold for 2 hours, and then air cool;

[0105] (c) Two-stage aging treatment: The first stage of aging involves heating the forged bar to 780°C, holding it at that temperature for 16 hours, and then air-cooling it to room temperature after it is taken out of the furnace; the second stage of aging involves heating the forged bar to 700°C, holding it at that temperature for 12 hours, and then air-cooling it to room temperature after it is taken out of the furnace.

[0106] Example 4 This example uses the same alloy raw materials as Example 1.

[0107] This embodiment provides a method for preparing a difficult-to-deform nickel-based superalloy bar for aerospace applications, comprising the following steps:

[0108] S1 triple smelting process for ingot preparation

[0109] Raw materials were weighed according to the alloy composition ratio, and consumable ingots were prepared using a three-stage smelting process of “vacuum induction melting (VIM) + protective atmosphere electroslag remelting (PESR) + vacuum arc remelting (VAR)”.

[0110] Vacuum Induction Melting (VIM): The materials are batched according to the above element ratio. Ni, Cr, Co, W, and Mo are charged into the vacuum induction melting furnace for melting. After complete melting, refining is carried out. Al, Ti, Nb, C, B, Zr, and Mg are added in the later stage of refining. The rare earth element Ce is added in one go in the form of Ni-Ce master alloy after refining and 12 minutes before casting. The vacuum degree is controlled at 0.8 Pa and the melting temperature is 1530℃ during melting. The vacuum degree is controlled at 0.8 Pa and the refining temperature is 1530℃ during refining. The refining time is 75 minutes. During tapping, the melt temperature is reduced to 1460℃ and cast into consumable electrode rods under vacuum.

[0111] Electroslag Remelting (PESR): VIM ingots are used as consumable electrodes and electroslag remelted under a protective atmosphere to obtain electroslag remelted ingots; Ar is introduced for protection during the process, with an Ar flow rate of 40 L / min and a remelting rate of 4.0 kg / min.

[0112] Vacuum self-consumption remelting (VAR): ESR ingots are subjected to vacuum self-consumption remelting, with the vacuum level controlled at 0.08 Pa and the remelting rate at 4.5 kg / min.

[0113] S2 pulse current assisted multi-stage homogenization processing

[0114] (a) The temperature was increased to 900℃ at a rate of 80℃ / h and held for 15 h, while a pulsed current was applied with a pulsed current density of 30 A / cm. 2 The pulse frequency is 200 Hz and the duty cycle is 50%.

[0115] (b) The temperature was increased to 1190℃ at a rate of 50℃ / h and held for 40 h, while a pulsed current was applied with a pulsed current density of 15 A / cm². 2 The pulse frequency is 500 Hz and the duty cycle is 40%.

[0116] (c) Cool to 1170℃ at a rate of 50℃ / h, hold for 15 h, and simultaneously apply a pulsed current with a pulsed current density of 10 A / cm². 2 The pulse frequency is 200 Hz and the duty cycle is 30%.

[0117] After homogenization, the oxide layer and dealloyed layer on the surface of the consumable ingot are removed by turning, with a turning depth of ≥3~5 mm on one side.

[0118] S3 stepped temperature controlled forging

[0119] (a) First forging: The ingot is heated to 1190°C and held for 4 hours before upsetting and drawing. During forging, the surface temperature of the billet is controlled at 1150~1190°C, the final forging temperature is 1100°C, and the deformation is 25%.

[0120] (b) Second forging: The billet is heated to 1170°C, held for 4 hours, and then upset and drawn. During the forging process, the surface temperature of the billet is controlled at 1130~1170°C, the final forging temperature is 1080°C, and the deformation is 30%.

[0121] (c) Third forging: The billet is heated to 1150℃, held for 4 hours, and then upset and drawn. During the forging process, the surface temperature of the billet is controlled at 1110~1150℃, the final forging temperature is 1080℃, and the deformation is 25%.

[0122] The total forging ratio for each firing is 7. During each firing process, when the surface temperature of the billet drops to the lower limit of the surface temperature control for that firing, it is immediately returned to the furnace for reheating. The reheating temperature is the heating temperature for that firing, and the reheating time is 1 hour.

[0123] S4 radial forging

[0124] After the billet is heated to 1140℃, it is then subjected to multi-pass radial forging using a radial forging machine. The deformation amount in each pass is controlled at 20%, and the final forging temperature is 1050℃.

[0125] S5 Dual-Stage Deformation Heat Treatment

[0126] (a) Post-forging deformation treatment: The radially forged bar is heated to 1100℃ and held for 2 h, then subjected to 18% compression deformation, with the deformation rate controlled at 0.03 s. -1 ;

[0127] (b) Solution treatment: Heat the deformed bar to 1130°C, hold for 2 hours, and then air cool;

[0128] (c) Two-stage aging treatment: The first stage of aging involves heating the forged bar to 780°C, holding it at that temperature for 16 hours, and then air-cooling it to room temperature after it is taken out of the furnace; the second stage of aging involves heating the forged bar to 700°C, holding it at that temperature for 12 hours, and then air-cooling it to room temperature after it is taken out of the furnace.

[0129] Example 5: This example uses the same alloy raw materials as Example 1.

[0130] This embodiment provides a method for preparing a difficult-to-deform nickel-based superalloy bar for aerospace applications, comprising the following steps:

[0131] S1 triple smelting process for ingot preparation

[0132] Raw materials were weighed according to the alloy composition ratio, and consumable ingots were prepared using a three-stage smelting process of “vacuum induction melting (VIM) + protective atmosphere electroslag remelting (PESR) + vacuum arc remelting (VAR)”.

[0133] Vacuum Induction Melting (VIM): The materials are batched according to the above element ratio. Ni, Cr, Co, W, and Mo are charged into the vacuum induction melting furnace for melting. After complete melting, refining is carried out. Al, Ti, Nb, C, B, Zr, and Mg are added in the later stage of refining. The rare earth element Ce is added in one go in the form of Ni-Ce master alloy after refining and 12 minutes before casting. The vacuum degree is controlled at 0.8 Pa and the melting temperature is 1530℃ during melting. The vacuum degree is controlled at 0.8 Pa and the refining temperature is 1530℃ during refining. The refining time is 75 minutes. During tapping, the melt temperature is reduced to 1460℃ and cast into consumable electrode rods under vacuum.

[0134] Electroslag Remelting (PESR): VIM ingots are used as consumable electrodes and electroslag remelted under a protective atmosphere to obtain electroslag remelted ingots; Ar is introduced for protection during the process, with an Ar flow rate of 40 L / min and a remelting rate of 4.0 kg / min.

[0135] Vacuum self-consumption remelting (VAR): ESR ingots are subjected to vacuum self-consumption remelting, with the vacuum level controlled at 0.08 Pa and the remelting rate at 4.5 kg / min.

[0136] S2 pulse current assisted multi-stage homogenization processing

[0137] (a) The temperature was increased to 900℃ at a rate of 80℃ / h and held for 15 h, while a pulsed current was applied with a pulsed current density of 30 A / cm. 2 The pulse frequency is 500 Hz and the duty cycle is 60%.

[0138] (b) The temperature was increased to 1190℃ at a rate of 50℃ / h and held for 40 h, while a pulsed current was applied with a pulsed current density of 15 A / cm². 2 The pulse frequency is 800 Hz and the duty cycle is 50%.

[0139] (c) Cool to 1170℃ at a rate of 50℃ / h, hold for 15 h, and simultaneously apply a pulsed current with a pulsed current density of 10 A / cm². 2 The pulse frequency is 400 Hz and the duty cycle is 40%.

[0140] After homogenization, the oxide layer and dealloyed layer on the surface of the consumable ingot are removed by turning, with a turning depth of ≥3~5 mm on one side.

[0141] S3 stepped temperature controlled forging

[0142] (a) First forging: The ingot is heated to 1190°C and held for 4 hours before upsetting and drawing. During forging, the surface temperature of the billet is controlled at 1150~1190°C, the final forging temperature is 1100°C, and the deformation is 25%.

[0143] (b) Second forging: The billet is heated to 1170°C, held for 4 hours, and then upset and drawn. During the forging process, the surface temperature of the billet is controlled at 1130~1170°C, the final forging temperature is 1080°C, and the deformation is 30%.

[0144] (c) Third forging: The billet is heated to 1150℃, held for 4 hours, and then upset and drawn. During the forging process, the surface temperature of the billet is controlled at 1110~1150℃, the final forging temperature is 1080℃, and the deformation is 25%.

[0145] The total forging ratio for each firing is 7. During each firing process, when the surface temperature of the billet drops to the lower limit of the surface temperature control for that firing, it is immediately returned to the furnace for reheating. The reheating temperature is the heating temperature for that firing, and the reheating time is 1.5 hours.

[0146] S4 radial forging

[0147] After the billet is heated to 1140℃, it is then subjected to multi-pass radial forging using a radial forging machine. The deformation amount in each pass is controlled at 20%, and the final forging temperature is 1050℃.

[0148] S5 Dual-Stage Deformation Heat Treatment

[0149] (a) Post-forging deformation treatment: The radially forged bar is heated to 1100℃ and held for 2 h, then subjected to 18% compression deformation, with the deformation rate controlled at 0.03 s. -1 ;

[0150] (b) Solution treatment: Heat the deformed bar to 1130°C, hold for 2 hours, and then air cool;

[0151] (c) Two-stage aging treatment: The first stage of aging involves heating the forged bar to 780°C, holding it at that temperature for 16 hours, and then air-cooling it to room temperature after it is taken out of the furnace; the second stage of aging involves heating the forged bar to 700°C, holding it at that temperature for 12 hours, and then air-cooling it to room temperature after it is taken out of the furnace.

[0152] Comparative Example 1: A method for preparing a difficult-to-deform nickel-based superalloy bar for aerospace applications, referring to Example 1, differs in that the homogenization treatment in step S2 is different.

[0153] The homogenization process in step S2 of Comparative Example 1 includes:

[0154] (a) Heat to 900℃ at a rate of 80℃ / h and hold for 15 h;

[0155] (b) Heat to 1190℃ at a rate of 50℃ / h and hold for 40 h;

[0156] (c) Cool down to 1170℃ at a rate of 50℃ / h and hold for 15 h.

[0157] Comparative Example 2 is a method for preparing a difficult-to-deform nickel-based superalloy bar for aerospace applications, referring to Example 1, except that the homogenization treatment in step S2 is different.

[0158] The homogenization process in step S2 of Comparative Example 2 includes:

[0159] The temperature was increased to 1190℃ at a rate of 80℃ / h and held for 48 h.

[0160] Comparative Example 3 is a method for preparing a difficult-to-deform nickel-based superalloy bar for aerospace applications, referring to Example 1, except that the forging treatment in step S3 is different.

[0161] Step S3 of the forging process in Comparative Example 3 includes:

[0162] After heating to 1190℃ in three stages and holding for 4 hours, upsetting and drawing were carried out without segmented surface temperature control or heat replenishment strategies. The final forging temperature was 1000℃.

[0163] Comparative Example 4: The difficult-to-deform nickel-based superalloy bar and its preparation method are compared with those of Example 1, except that the heat treatment in step S5 of the preparation method is different.

[0164] Step S5 of Comparative Example 4 includes the following heat treatment:

[0165] After radial forging, the solution treatment and two-stage aging treatment are performed directly, without post-forging deformation treatment.

[0166] Comparative Example 5 refers to the difficult-to-deform nickel-based superalloy bar and its preparation method as described in Example 1, except that the forging treatment in step S3 and the heat treatment in step S5 are different.

[0167] Step S3 forging in Comparative Example 5 includes:

[0168] After heating to 1190℃ in three stages and holding for 4 hours, upsetting and drawing were carried out without segmented surface temperature control or heat replenishment strategies. The final forging temperature was 1000℃.

[0169] Step S5 of Comparative Example 5 includes the following heat treatment:

[0170] After radial forging, the solution treatment and two-stage aging treatment are performed directly, without post-forging deformation treatment.

[0171] The tensile and creep properties of the nickel-based superalloys of Examples 1-5 and Comparative Examples 1-5 were tested using conventional testing methods in the art, as shown in Tables 1, 2 and 3.

[0172] Table 1. Tensile property test results of nickel-based superalloys at room temperature.

[0173]

[0174] Table 2. Tensile properties of nickel-based superalloys at 750℃

[0175]

[0176] Table 3. Test results of creep rupture properties of nickel-based superalloys at 750℃

[0177]

[0178] The test results above show that the tensile properties and creep properties of Examples 1-5 are higher than those of Comparative Examples 1-5. Among them, Example 5, by comprehensively using high-frequency pulse parameters, enhanced temperature compensation strategy and 18% post-forging deformation, achieves the best performance in all aspects.

[0179] Combined with Example 1 and Comparative Examples 1 and 2, it is shown that the electroplastic effect and Joule heating effect generated by the pulsed current can significantly enhance the atomic diffusion ability of segregated elements such as W, Mo, and Nb, making dendrite segregation more thorough; multi-stage homogenization and pulsed current have a synergistic effect, and the combination of the two can improve tensile properties and durability.

[0180] Combined with Example 1 and Comparative Example 3, it is shown that without surface temperature control, the surface temperature of the billet drops too quickly, the surface-to-core temperature difference exceeds 150°C, and the surface deformation resistance increases dramatically, resulting in microcracks; at the same time, the final forging temperature is too low (≤1000°C), causing the γ′ phase to precipitate prematurely, further deteriorating the thermoplasticity.

[0181] Combined with Example 1 and Comparative Example 4, it is shown that the dislocations and subgrain boundaries introduced by the post-forging deformation treatment provide nucleation sites for subsequent recrystallization. At the same time, the deformation dislocations, as non-uniform nucleation sites for the γ′ phase, promote the dispersed precipitation of the γ′ phase, achieving a synergistic gain of fine grain strengthening and precipitation strengthening.

[0182] Combining Example 1 and Comparative Example 5, it is shown that pulse-assisted homogenization provides the basis for tissue homogeneity, stepped temperature-controlled forging ensures that the tissue is not damaged during hot working, and two-stage deformation heat treatment maximizes the strengthening potential. The three work together and none of them can be omitted.

[0183] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art should be able to make corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A method for preparing a difficult-to-deform nickel-based superalloy bar for aerospace applications, characterized in that, Includes the following steps: S1 Tri-Smelting Preparation of Ingots: Weigh the alloy raw materials and use a triple smelting process of vacuum induction melting, protective atmosphere electroslag remelting and vacuum consumable remelting to obtain consumable ingots. S2 Pulse Current Assisted Multi-Stage Homogenization Processing: Under the assistance of pulse current, the consumable ingot is subjected to multi-stage temperature-controlled homogenization diffusion annealing to obtain a homogenized ingot. S3 stepped temperature-controlled forging: The homogenized ingot is forged in multiple forging cycles. During each forging cycle, the surface temperature of the billet is controlled to be above the lower limit of the set surface temperature for that cycle. When the surface temperature of the billet drops to the lower limit of the set surface temperature, it is returned to the furnace for reheating to obtain the bar after billet opening. S4 radial forging: After the billet is heated, it is subjected to multiple radial forgings to obtain the radially forged bar. S5 dual-stage deformation heat treatment: After heating the forged bar to subsolid temperature and holding it at that temperature, it first undergoes post-forging deformation treatment, followed by solution treatment and dual-stage aging treatment. In step S1, the alloy raw materials, by mass fraction, include: Cr 9.0~12.0%, Co 14.0~17.0%, W 9.0~11.0%, Mo 0.8~1.5%, Al 4.8~5.5%, Ti 2.2~3.2%, Nb 1.0~2.0%, C 0.06~0.12%, B 0.015~0.035%, Zr 0.02~0.06%, Ce 0.005~0.020%, Mg 0.002~0.008%, with the balance being Ni and unavoidable impurities; In step S2, the specific process of pulse current-assisted multi-stage homogenization is as follows: (a) Heat to 850-950℃ at a rate of 50-100℃ / h, hold for 10-20 h, and apply a pulsed current density of 10-50 A / cm. 2 Frequency 50~500 Hz, duty cycle 30~70%; (b) Increase the temperature to 1180-1200℃ at a rate of 30-80℃ / h, hold for 30-50 h, and apply a pulsed current density of 5-30 A / cm. 2 Frequency 100~1000 Hz, duty cycle 20~60%; (c) Cool to 1160-1180℃ at a rate of 40-60℃ / h, hold for 10-20 h, and apply a pulsed current density of 5-20 A / cm. 2 Frequency 50~500 Hz, duty cycle 20~50%; In step S3, the specific process of stepped temperature-controlled forging is as follows: (a) First forging: Heat to 1180~1200℃, hold for 2~6 h, upsetting and drawing, control the billet surface temperature to 1150~1200℃, final forging temperature to 1100±5℃, deformation amount to 20~30%; (b) Second forging: Heat to 1160~1180℃, hold for 2~6 h, upsetting and drawing, control the billet surface temperature to 1130~1180℃, final forging temperature to 1080±5℃, deformation amount to 25~35%; (c) Third forging: Heat to 1140~1160℃, hold for 2~6 h, upsetting and drawing, control the billet surface temperature to 1110~1160℃, final forging temperature to 1080±5℃, deformation amount to 20~30%; The total forging ratio for each heat is 6~8; when the surface temperature of the billet drops to the lower limit of the set surface temperature for that heat, it is returned to the furnace for reheating. The reheating temperature is the heating temperature of that heat, and the reheating time is 0.5~2 hours. The number of times the billet is returned to the furnace for reheating in a single heat should not exceed 3 times to avoid repeated hot and cold cycles that exacerbate thermal fatigue. In step S5, the specific process of the two-stage deformation heat treatment is as follows: (a) Post-forging deformation treatment: Heat the radially forged bar to 1080~1120℃, hold for 1~3 h, and perform 10~20% compression deformation at a deformation rate of 0.01~0.1 s. -1 ; (b) Solution treatment: Temperature 1110~1160℃, hold for 1~4 h, then air cool; (c) First-level aging treatment: temperature 760~800℃, heat preservation for 8~20 h, air cooling; (d) Secondary aging treatment: temperature 650~720℃, heat preservation for 8~16 h, air cooling.

2. The method for preparing aerospace-grade, difficult-to-deform nickel-based superalloy bars according to claim 1, characterized in that, In step S1, the vacuum induction melting includes three stages: melting, refining, and tapping. The melting vacuum degree is 0~1 Pa, the melting temperature is 1500~1550℃, the refining vacuum degree is 0~1 Pa, the refining temperature is 1500~1550℃, the refining time is 60~90 min, and the tapping temperature is 1450~1480℃. During the protective atmosphere electroslag remelting process, Ar is introduced for protection, the Ar flow rate is 30~50 L / min, and the remelting rate is controlled at 3.0~5.0 kg / min. The vacuum consumable remelting controls the vacuum degree to be 0~0.1 Pa and the remelting rate to be 3.0~6.0 kg / min.

3. The method for preparing aerospace-grade, difficult-to-deform nickel-based superalloy bars according to claim 1, characterized in that, In step S4, the heating temperature for radial forging is 1120~1160℃, the deformation amount per pass is 15~25%, and the final forging temperature is 1050±5℃.

4. A difficult-to-deform nickel-based superalloy bar for aerospace applications, characterized in that, The alloy rod is prepared using the preparation method described in any one of claims 1 to 3. The alloy rod has an average grain size of grade 7, a γ′ phase volume fraction of 50 to 60%, a room temperature tensile strength of 1640 to 1680 MPa, a room temperature yield strength of 1210 to 1255 MPa, a 750℃ tensile strength of 1230 to 1270 MPa, a 750℃ yield strength of 1085 to 1120 MPa, and a 750℃ / 620 MPa creep rupture life of 108 to 118 h.

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