A short-process preparation method for Inconel 718 alloy rings

Abstract

The present invention belongs to the field of metal materials technology, and specifically relates to a short-process method for preparing Inconel 718 alloy rings, comprising vacuum melting, vacuum centrifugal casting, hot rolling, and heat treatment to produce the Inconel 718 alloy rings. These steps significantly shorten the process flow and improve production efficiency. Compared to traditional preparation processes, they can also save production costs, reduce energy consumption, and reduce emissions. The prepared Inconel 718 alloy rings have fine and uniform grain size, a grain size reaching ASTM 9, high strength, and excellent overall performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal materials, and in particular relates to a method for preparing Inconel 718 alloy rings through a short process. Background Art

[0002] Inconel 718 is currently the most widely used nickel-based superalloy. It exhibits excellent strength, ductility, and corrosion resistance in the medium- to high-temperature range of 235°C to 650°C. This material is widely used in the manufacture of key annular components in aircraft engines, including casings, sealing rings, load-bearing rings, and guide rings.

[0003] Although various manufacturing processes for high-temperature alloy rings have been proposed, for example, Chinese patent CN201611090986.1 sequentially processes GH4169 alloy billets through upsetting, hole forming, first rolling, second rolling, and third rolling, followed by heat treatment to produce GH4169 alloy rings. Chinese patent CN201711449768.7 utilizes a rolling-leveling-rolling manufacturing method to produce GH4169 rings, including sawing, heating, heat preservation, upsetting, punching, hole expansion, rolling, leveling, and rolling. Chinese patent CN201811515356.3 heats, upsets, and punches GH4169 alloy bar stock to form a blank, which is then heated multiple times and gradually expanded (pre-expansion and final expansion) to obtain a ring blank. Finally, it undergoes bulging to size and heat treatment. Chinese patent CN202411642922.2 utilizes GH4169 bar stock, which is triple-melted and then formed through upsetting, punching, and hole expansion. This process is then rolled on a CNC ring rolling machine and finally heat-treated. These patents generally rely on multiple heating cycles, multiple deformation passes, and complex machining processes. The ring forming process requires multiple preheating, deformation, and cooling steps, resulting in a lengthy process flow, high energy consumption, and a long production cycle. Furthermore, the multiple large deformations and high-temperature treatments can easily introduce problems such as coarse grains, abnormal textures, and uneven microstructures, leading to fluctuations in the microstructure and performance of the finished product. This makes it difficult to achieve both high performance and manufacturing efficiency and cost control.

[0004] In recent years, powder metallurgy combined with hot isostatic pressing (PM-HIP) technology has also been applied to the production of high-temperature alloy rings. For example, Chinese patents CN202311019590.8 and CN202411031884.7 both utilize powder metallurgy to produce ring blanks by hot isostatic pressing of high-temperature alloy powders. This method effectively avoids the segregation and shrinkage defects found in traditional ingot casting by preforming a powder body and then densifying it under high temperature and high pressure, resulting in a uniform and fine structure. However, the high cost of raw materials for powder metallurgy, the complex and time-consuming powder preparation and packaging processes, and the subsequent need for large-scale deformation hot working to achieve dimensional accuracy and performance optimization result in overall manufacturing costs far exceeding those of traditional processes, making it difficult to promote and apply in large-scale production.

[0005] Therefore, the existing high-temperature alloy ring manufacturing processes, whether it is the traditional multi-step long process method or the powder metallurgy combined with hot isostatic pressing (PM-HIP) technology, have problems such as high cost, long cycle, high energy consumption, low forming efficiency and fluctuations in organizational properties. It is difficult to meet the urgent needs of aviation engine rings for high performance, high reliability and large-scale production. Summary of the Invention

[0006] In view of this, the present invention discloses a method for preparing Inconel 718 alloy rings in a short process, which specifically comprises the following steps:

[0007] S1. Vacuum Melting: Inconel 718 alloy material is vacuum melted in a vacuum induction melting furnace to obtain Inconel 718 alloy liquid metal. This step effectively reduces the risk of gas inclusion and composition segregation during the melting process through vacuum melting and inert gas protection, ensuring the compositional basis for subsequent phase transformation and microstructure control.

[0008] S2. Pour the Inconel 718 alloy molten metal into a centrifugal casting machine for vacuum centrifugal casting until the Inconel 718 alloy molten metal is completely solidified and cooled to room temperature, then close the centrifugal casting machine to obtain the Inconel 718 alloy cast ring blank. The above-mentioned centrifugal casting process can achieve the precipitation of γ'' phase in the Inconel 718 alloy cast ring blank, and a large number of fine ellipsoidal γ'' phases are formed near the grain boundaries and arranged and distributed along the grain boundaries. Compared with the traditional casting process, the centrifugal casting process improves the filling capacity and effectively suppresses shrinkage and macrosegregation by enhancing the static pressure and thermal gradient during solidification. At the same time, the local stress field induced by the centrifugal force field and the rapid solidification environment jointly reduce the nucleation energy barrier of the γ'' phase, so that the γ'' phase can be finely dispersed and precipitated in the cast state. The present invention achieves the fine dispersion precipitation of the γ'' phase in the cast state, providing a precursor phase basis for inducing the γ''→δ phase transformation in the subsequent hot rolling process.

[0009] However, the aforementioned centrifugal casting process can lead to the precipitation of Laves phase in the Inconel 718 alloy cast ring. In Inconel 718 alloy, Laves phase, a brittle intermetallic compound rich in Nb and Mo, often segregates along grain boundaries at the end of solidification to form coarse, massive or dendritic structures. This is a significant structural defect that degrades alloy properties. Its presence not only consumes the Nb required for the formation of the γ' strengthening phase, inhibiting the precipitation of the precipitated strengthening phase, but also, due to its brittleness and irregular, large-scale morphology, it easily becomes a crack source during service, reducing the material's toughness and fracture resistance.

[0010] In step S2, the pouring temperature is 1420~1450℃, and the mold speed of the centrifugal casting machine is 600~800r / min. If the pouring temperature is lower than 1420°C, the fluidity of the melt decreases, which is not conducive to the complete filling of the ring mold. It is easy to form defects such as cold shut and shrinkage at the end of filling. In severe cases, it will cause the ring blank to fail to form. If the pouring temperature is higher than 1450°C, the overheating of the melt will prolong the solidification time, aggravate the solute segregation between dendrites, and promote the enrichment of elements such as Nb and Mo at the grain boundaries, thereby increasing the precipitation of Laves phase and even inducing high-temperature defects such as solidification hot cracks. The above temperature range can take into account both the filling fluidity and solidification control requirements, and is the best window for achieving organizational uniformity and phase control. When the mold speed of the centrifugal casting machine is lower than 600r / min, the centrifugal force is insufficient, the driving force for the melt to fill the mold is reduced, and macro defects such as segregation, shrinkage holes, and even cracks are likely to appear on the inner wall area of ​​the ring; when the speed exceeds 800r / min, the excessive centrifugal acceleration will cause the metal liquid to have too strong an impact force, which may cause the melt to splash, reducing the integrity and surface quality of the finished product. Due to its compositional characteristics, Inconel 718 alloy is inevitably accompanied by a certain amount of Laves phase precipitation at the end of solidification, especially under the condition of Nb enrichment in the residual melt area between dendrites. The present invention optimizes the vacuum centrifugal casting process. By optimizing the pouring temperature and mold speed control strategy, it effectively shortens the solidification time and inhibits the Nb segregation behavior between dendrites, so that the initial precipitation behavior of the Laves phase is controlled. The size of the Laves phase finally formed is significantly reduced and the distribution is discrete, which can greatly reduce its negative impact on the uniformity of the structure and mechanical properties. This organizational feature provides a good foundation for the further fragmentation and dissolution of the Laves phase in the subsequent controlled rolling, controlled cooling and heat treatment processes.

[0011] S3. The Inconel 718 alloy cast ring blank was preheated and then rolled on a rolling mill, undergoing two deformation passes to obtain an Inconel 718 alloy ring forging. The key to the secondary hot rolling process design lies in applying deformation in stages to achieve coordinated regulation of the γ'' to δ phase transformation behavior by stress state and temperature, while also promoting the fracture and fragmentation of the primary Laves phase under the action of deformation stress.

[0012] S4. Heat treatment of the Inconel 718 alloy ring forgings, including solution treatment, is performed. The specific solution treatment procedure involves heating the Inconel 718 alloy ring forgings to 950°C–980°C, holding for 1 hour, and then water cooling to room temperature. Under the process conditions specified in steps S1–S3, solution treatment fully dissolves the γ' and γ'' phases into the matrix, forming a uniform, supersaturated solid solution. The partially crushed Laves phase also dissolves at high temperatures, forming submicron-sized particles. This treatment effectively eliminates residual stresses generated by the previous hot rolling process. It should be noted that residual stresses primarily arise from non-uniform plastic strain during hot deformation and thermal stress accumulation during cooling. Water cooling after solution treatment effectively blocks secondary precipitation of the δ phase during cooling, preventing embrittlement caused by excessive grain boundary pinning. The γ' phase is a pre-existing phase within the alloy.

[0013] Preferably, in step S4, the heat treatment process also includes aging treatment: the solution-treated Inconel 718 alloy ring is heated to 700-730°C, held at this temperature for 8 hours, then furnace-cooled to 600-630°C at a rate of 50°C / h. After further holding for 8 hours, the ring is air-cooled to room temperature to obtain the Inconel 718 alloy ring. This double aging treatment precisely controls the precipitation of the γ′ phase in stages. The first stage promotes the nucleation and precipitation of the γ′ phase at a higher temperature, resulting in a high-density strengthening phase. The second stage optimizes the size and distribution of the precipitated phase at a lower temperature, improving coherence and pinning ability to maximize the precipitation strengthening effect. Simultaneously, the controlled rolling and controlled cooling strategy induces the formation of an appropriate amount of uniformly distributed δ phase, which remains stable along grain boundaries and acts as a grain-boundary pinning agent during the heat treatment process. By effectively pinning grain boundaries, the δ phase limits the growth of recrystallized grains, promotes microstructure refinement and stabilization, and contributes to a fine and uniform recrystallized grain structure. After heat treatment, the grains of the rings are further refined evenly, with an average grain size of 13.6 μm and a grain size of ASTM grade 9.

[0014] As a supplement to the technical solution of the present invention, in step S3, the Inconel 718 alloy cast ring blank is preheated to 980-1010°C and held for 2 hours. This preheating treatment allows the first hot rolling pass to achieve sufficient plastic deformation and grain breakage in the high-temperature zone, promotes the initiation of the dynamic recrystallization process, homogenizes the structure, and suppresses coarse primary grains, achieving coordinated regulation of the stress state and temperature for the γ'' to δ phase transformation behavior.

[0015] As a supplement to the technical solution of the present invention, in step S3, the Inconel 718 alloy cast ring blank is cooled to below 800°C after the first deformation and then deformed for the second time. In the second pass, high-density dislocations and strain energy are continuously introduced in the low-temperature zone below 800°C, effectively delaying the excessive transformation of γ'' to δ phase, inducing only an appropriate amount of δ phase to precipitate at the grain boundary, forming a stable and uniform pinning phase distribution, and inhibiting the growth of recrystallized grains. In Inconel 718 alloy, γ'' phase is the main precipitation strengthening phase, and its thermal stability under hot deformation conditions is relatively low. Especially under the coupling effect of high temperature and large deformation, it is very easy to undergo excessive transformation to δ phase. This type of excessive phase transformation severely weakens the strengthening effect of the γ' phase: on the one hand, the large amount of δ phase precipitation consumes the Nb element originally used to form γ', reducing the subsequent precipitation ability of the γ' phase; on the other hand, the formed δ phase often precipitates along the grain boundaries in a continuous, coarse needle-like morphology, which not only weakens the grain boundary bonding force and causes significant grain boundary embrittlement, but also easily becomes a crack source, reducing the toughness and service stability of the material. Therefore, this controlled rolling and controlled cooling strategy prevents the agglomeration and coarsening of the δ phase while ensuring the full retention of the γ' strengthening phase, achieving a coordinated optimization of microstructure refinement and strengthening phase.

[0016] As a supplement to the technical solution of the present invention, water cooling is performed after the second deformation in step S3. The water cooling process after the hot roll forming can quickly cross the sensitive temperature zone for δ phase precipitation, further suppressing the rapid precipitation and growth of δ phase.

[0017] As a supplement to the technical solution of the present invention, in step S3, the first reduction is 30% to 40%, and the second reduction is 30% to 40%, for a total reduction of 60% to 80% for both roll-forming passes. The large deformation in the first pass introduces a high density of dislocations and severe plastic strain, which causes the primary Laves phase to fracture and break under the deformation stress, reducing particle size and altering its morphological integrity. The second pass, at a lower temperature (below 800°C), further inhibits the growth and agglomeration of the Laves phase at high temperatures. Combined with rapid water cooling, this reduces the thermal stability of the Laves phase.

[0018] As a supplement to the technical solution of the present invention, in step S3, after the first deformation, the Inconel 718 alloy cast ring blank is cooled to a temperature within the range of 700-800° C. for the second deformation. When the temperature is lower than 700° C., cracks may appear after hot rolling.

[0019] As a supplement to the technical solution of the present invention, in step S3, the feeding speed of the core roller of the rolling machine is 0.8~1.5mm / s.

[0020] Beneficial effects:

[0021] 1. Shortened process flow and improved production efficiency. Centrifugal casting directly forms rings within 30 minutes. The subsequent hot rolling and heat treatment shortens the cycle to 5-6 days, greatly shortening the process flow and production cycle compared to traditional hot forming methods.

[0022] 2. Material savings and cost reduction. The new process directly forms centrifugally cast ring blanks through rolling, eliminating the punching step in existing processes. Aside from scale loss, no other waste material is generated, thus reducing the generation of punching waste. Taking a 1.2m diameter ring as an example, the new process can save 25% to 35% of material. At the same time, the reduced number of heating times also reduces material loss. Generally, the first heating loss is 2% to 3%, and the second heating loss is 1.5% to 2%. The more heating times, the greater the loss. Therefore, the reduction in the number of heating times and the forging process also reduces material loss. Eliminating the second heating and forging process can save an additional 3% to 4% of material.

[0023] 3. Energy conservation and emission reduction. The new process reduces the number of billet heating times, saves energy, and reduces emissions of pollutants such as CO2. This meets the current national demand for promoting green development and promotes the realization of clean production goals.

[0024] 4. Savings on equipment investment: Since the upsetting and punching processes are omitted, the present invention does not require large equipment such as forging hammers and hydraulic presses, thus reducing equipment investment costs and corresponding power consumption.

[0025] 5. The Inconel 718 cast ring blank prepared by vacuum centrifugal casting has no shrinkage defects, no macrosegregation, fine and uniform grains, an average grain size of 56μm, and γ″ phase precipitated both within the grains and at the grain boundaries.

[0026] 6. The present invention regulates the precipitation behavior of the δ phase by implementing a controlled rolling and controlled cooling strategy during the hot rolling process, so that the γ″ phase is transformed into the δ phase in an appropriate amount, avoiding excessive consumption of the strengthening phase γ″ and grain boundary embrittlement. At the same time, the pinning effect of the appropriate amount of δ phase on the grain boundary is utilized to effectively inhibit the growth of recrystallized grains and achieve grain refinement.

[0027] 7. The present invention can effectively regulate the Laves phase, realize the crushing and dissolution of Laves, and thus transform the traditional harmful large-sized, irregular Laves phase into a beneficial submicron granular Laevs phase.

[0028] 8. It can effectively control the grain size. The average grain size of the ring reaches 13.6μm and the grain size reaches ASTM 9.

[0029] 9. The tensile strength of the Inconel 718 alloy rings prepared by the present invention reaches 1367 MPa at room temperature, exceeding the military standard by 7.6%; the elongation reaches 29.7%, exceeding the military standard by 98%, both reaching and exceeding the military standard, with excellent comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flow chart for preparing the Inconel 718 alloy ring of the present invention.

[0031] Figure 2 (a) is the macroscopic corrosion morphology of the longitudinal section of the Inconel 718 alloy cast ring prepared in Example 1.

[0032] Figure 2 (b) is a metallographic microstructure of the inner ring portion of the Inconel 718 alloy casting ring blank prepared in Example 1.

[0033] Figure 2 (c) is a metallographic microstructure of the ring portion of the Inconel 718 alloy cast ring blank prepared in Example 1.

[0034] Figure 2 (d) is a metallographic microstructure of the outer ring portion of the Inconel 718 alloy casting ring blank prepared in Example 1.

[0035] Figure 2 (e) is a statistical diagram of the grain sizes at the inner, middle, and outer ring positions of the longitudinal section of the Inconel 718 alloy cast ring blank prepared in Example 1.

[0036] Figure 3 This is the Laves phase morphology of the Inconel 718 alloy cast ring blank prepared in Example 1.

[0037] Figure 4 (a) γ'' phase morphology near the grain boundary of the Inconel 718 alloy cast ring prepared in Example 1 and the corresponding selected area electron diffraction (SAED) pattern.

[0038] Figure 4 (b) γ'' phase morphology in the intragranular region of the Inconel 718 alloy cast ring blank prepared in Example 1 and the corresponding selected area electron diffraction (SAED) pattern.

[0039] Figure 5 (a) Inverse pole figure (IPF figure) of the Inconel 718 alloy ring forging prepared in Example 1.

[0040] Figure 5 (b) is the distribution diagram of large and small angle grain boundaries of the Inconel 718 alloy ring forging prepared in Example 1.

[0041] Figure 5 (c) is the internal local orientation deviation (GOS) diagram of the Inconel 718 alloy ring forging prepared in Example 1.

[0042] Figure 6 This is the δ phase morphology of the Inconel 718 alloy ring forging prepared in Example 1.

[0043] Figure 7 (a) Inverse pole figure (IPF figure) of the Inconel 718 alloy ring prepared in Example 1.

[0044] Figure 7 (b) is a statistical diagram of the grain size of the Inconel 718 alloy ring prepared in Example 1.

[0045] Figure 8 This is a Laves phase morphology of the Inconel 718 alloy ring prepared in Example 1.

[0046] Figure 9 This is the δ phase morphology of the Inconel 718 alloy ring prepared in Example 1.

[0047] Figure 10 This is a room temperature tensile curve of the Inconel 718 alloy ring prepared in Example 1.

[0048] Figure 11 This is a Laves phase morphology of the fracture cross section of the Inconel 718 alloy ring prepared in Example 1 after room temperature stretching.

[0049] Figure 12 This is a photo of the finished product of the Inconel 718 alloy ring prepared in Example 1.

[0050] Figure 13 This is the δ phase morphology of the Inconel 718 alloy ring forging prepared in Example 4.

[0051] Figure 14 (a) is the microstructure diagram of the Inconel 718 alloy ring forging prepared in Comparative Example 1.

[0052] Figure 14 (b) is the microstructure of the Inconel 718 alloy ring prepared in Comparative Example 1.

[0053] Figure 15 (a) is the microstructure of the Inconel 718 alloy ring forging prepared in Comparative Example 2.

[0054] Figure 15(b) is the microstructure of the Inconel 718 alloy ring prepared in Comparative Example 2.

[0055] Figure 16 (a) is the microstructure diagram of the Inconel 718 alloy ring forging prepared in Comparative Example 3.

[0056] Figure 16 (b) is the microstructure of the Inconel 718 alloy ring prepared in Comparative Example 3.

[0057] Figure 17 This is the EBSD grain orientation map of the Inconel 718 alloy ring prepared in Comparative Example 3.

[0058] Figure 18 (a) is the Laves phase microstructure diagram of the Inconel 718 alloy cast ring blank prepared in Comparative Example 4.

[0059] Figure 18 (b) is the Laves phase metallographic structure diagram of the Inconel 718 alloy ring prepared in Comparative Example 4.

[0060] Figure 19 This is a cross-sectional macroscopic photograph of the Inconel 718 alloy ring prepared in Comparative Example 5.

[0061] Figure 20 This is a physical picture of the Inconel 718 alloy cast ring blank prepared in Comparative Example 6.

[0062] Figure 21 This is the metallographic structure diagram of the Inconel 718 alloy ring forging prepared in Comparative Example 7.

[0063] Figure 22 This is a macroscopic photograph of the cross section of the Inconel 718 alloy ring prepared in Comparative Example 8.

[0064] Figure 23 This is the metallographic structure diagram of the Inconel 718 alloy ring prepared in Comparative Example 9. DETAILED DESCRIPTION

[0065] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0066] The present invention revolves around the phase transformation behavior and organizational regulation of Inconel 718 high-temperature alloy rings during the short-process preparation process. The core lies in achieving grain boundary stabilization and grain refinement by controlling the γ''→δ phase transformation, while coordinating the effective regulation of the Laves phase to improve organizational uniformity and comprehensive performance. Combining vacuum centrifugal casting, high-strain hot rolling (controlled rolling and controlled cooling) and optimized heat treatment paths, a set of ring preparation processes with compact processes and excellent performance has been formed. The following is a detailed description of the vacuum centrifugal casting-controlled rolling and controlled cooling short-process collaborative preparation method for Inconel 718 alloy rings of the present invention in conjunction with the accompanying drawings and embodiments. Figure 1 FIG. 1 is a flow chart of the preparation of the Inconel 718 alloy ring according to the present invention.

[0067] Example 1: The short-process Inconel 718 alloy ring preparation method of this embodiment is carried out according to the following steps:

[0068] S1: Vacuum Melting. The Inconel 718 alloy raw material is placed in a vacuum induction melting furnace. The vacuum is reduced to below 1 Pa, and then a high-purity argon protective atmosphere is introduced. The raw material is heated under the argon atmosphere until it is completely melted, obtaining an Inconel 718 alloy liquid with a uniform composition.

[0069] S2: Vacuum centrifugal casting. The smelted Inconel 718 alloy liquid is kept at 1420℃ for 10 minutes and quickly poured into a metal mold made of 45 steel. The mold is centrifugally rotated at a speed of 600r / min. The melt fills the mold under high centrifugal force and stops rotating after cooling to room temperature in a vacuum environment, forming a dense Inconel 718 alloy casting ring blank without shrinkage cavities. Figure 2 (a) is the longitudinal section macroscopic corrosion morphology of the vacuum centrifugal Inconel 718 alloy casting ring. The microstructure metallographic images of the casting ring at different positions are as follows: Figure 2 (b) to Figure 2 (d), where Figure 2 (b) is the inner ring area, Figure 2 (c) Central, Figure 2 (d) is the outer ring area, Figure 2 (e) is the statistical diagram of the grain size at the inner, middle and outer ring positions of the longitudinal section of the vacuum centrifugal Inconel 718 alloy casting ring billet. Figure 2 It can be seen that the overall tissue is uniform and dense.

[0070] Figure 3This is the Laves phase morphology of an Inconel 718 alloy cast ring. This phase is mainly concentrated along the grain boundaries and appears as irregular blocks. The overall distribution is relatively continuous and small, with a particle size of approximately 5μm. The vacuum centrifugal casting process forms a fine and uniform primary Laves phase under a high centrifugal force field and rapid solidification environment. This is significantly different from the large chain or block-like Nb-rich phase that is easily generated in traditional ingot casting processes. Rapid solidification suppresses the severe segregation of solute elements at grain boundaries, significantly reducing the size of the Laves phase and making the morphology more dispersed, thereby reducing the risk of stress concentration and crack source formation during subsequent deformation.

[0071] The γ'' precipitation behavior of the cast ring was further observed by transmission electron microscopy (TEM). Figure 4 As shown in (a), a large number of small ellipsoidal γ'' phases can be clearly observed near the grain boundaries, distributed along the grain boundaries. Figure 4 (b) shows the morphology of γ'' precipitation in the intragranular region, which is dispersed and uniformly distributed in the matrix. Figure 4 (a) Figure 4 (b) The illustration in the upper right corner is the corresponding selected area electron diffraction (SAED) pattern. The observed characteristic superlattice diffraction spots further verify that the precipitated phase is the γ'' phase, and the orientation relationship is Z=

[001] . The centrifugal casting process improves the filling capacity and effectively suppresses shrinkage and macrosegregation by enhancing the static pressure and thermal gradient during solidification. At the same time, the local stress field induced by the centrifugal force field and the rapid solidification environment jointly reduce the nucleation energy barrier of the γ'' phase, allowing the γ'' phase to achieve fine dispersed precipitation in the cast state. The present invention achieves fine dispersed precipitation of the γ'' phase in the cast state, providing a precursor phase basis for inducing the γ''→δ phase transformation in the subsequent hot rolling process.

[0072] S3: Hot Rolling. After holding at 1000°C for 2 hours, the rings were transferred to a CNC radial-axial rolling mill for hot rolling. The core roller feed speed was set at 1 mm / s, and rolling was performed in two passes. The first pass achieved a 40% reduction; the second pass, performed after the rings had cooled to 800°C, achieved a 30% reduction, for a total reduction of 70%. After rolling, the rings were rapidly cooled using water cooling to obtain Inconel 718 alloy ring forgings.

[0073] The microstructure characteristics of Inconel 718 alloy ring forgings after controlled rolling and hot and cold rolling are as follows: Figure 5 shown. Figure 5 (a) is the inverse pole figure (IPF figure), which shows that after controlled rolling and controlled cooling, the grains present obvious orientation texture, some grains are oriented along the rolling direction, and the texture strength is enhanced. Figure 5(b) is the distribution diagram of large-angle grain boundaries (>15°), which shows that the controlled rolling and controlled cooling strategy can effectively introduce a large number of small-angle grain boundaries into the structure while retaining some large-angle grain boundaries, which is beneficial to subsequent recrystallization and texture evolution. Figure 5 (c) shows the internal local orientation deviation (GOS) diagram. The overall GOS distribution is high, with large areas appearing red, reflecting the large amount of strain energy and high-density dislocation structures stored within the material due to plastic deformation. This high stored energy state originates from the low-temperature rolling in the second pass of the controlled rolling and cooling strategy. This high stored energy structure significantly influences phase transformation and diffusion behavior during subsequent heat treatment.

[0074] like Figure 6 Figure 2 shows the δ phase morphology of an Inconel 718 alloy ring forging. During hot rolling, fine, dispersed δ phase preferentially forms near grain boundaries. The δ phase is distributed along the grain boundaries in a needle-like pattern. The controlled rolling and controlled cooling strategy induces a moderate transformation of some pre-precipitated γ' phase into δ phase, resulting in a moderate and evenly distributed δ phase in the microstructure.

[0075] S4: Heat Treatment. The hot-rolled Inconel 718 ring forgings undergo solution treatment and dual aging. First, the solution treatment is completed by holding at 980°C for one hour and then water cooling. Then, the forging is held at 720°C for eight hours, furnace-cooled to 620°C at a rate of 50°C / hour, and then held for another eight hours before air cooling to room temperature to complete the aging treatment. This results in the Inconel 718 alloy ring.

[0076] The above solution treatment can make the γ' phase and γ'' phase fully dissolve into the matrix to form a uniform supersaturated solid solution. And make the partially broken Laves phase dissolve at high temperature to present submicron particles, as shown in the following example: Figure 8 The figure below shows the Laves phase morphology of an Inconel 718 alloy ring. Residual stresses generated by the initial hot rolling process are eliminated. Water cooling effectively blocks the secondary precipitation of δ phase during the cooling process, preventing embrittlement caused by excessive grain boundary pinning.

[0077] like Figure 9 As shown in FIG. 1 , the δ phase morphology of the Inconel 718 alloy ring in Example 1 is shown. The δ phase effectively pins the grain boundaries, limits the growth of recrystallized grains, promotes the refinement and stabilization of the structure, and helps to obtain a fine and uniform recrystallized grain structure.

[0078] like Figure 7 (a) shows the inverse pole figure (IPF figure) of the Inconel 718 alloy ring. After heat treatment, the grains of the ring are further uniformly refined.

[0079] like Figure 7(b) shows the grain size statistics of Inconel 718 alloy rings. The average grain size reaches 13.6 μm and the grain size is ASTM grade 9.

[0080] like Figure 10 Figure 2 shows the room temperature tensile curve of an Inconel 718 alloy ring. The sample exhibits excellent mechanical properties, with a tensile strength of 1367 MPa and an elongation of 29.7%. Compared to military standards (tensile strength of 1270 MPa and elongation of 15%), the alloy ring produced by this invention has an approximately 7.6% increase in tensile strength and an approximately 84% increase in elongation. These comprehensive properties meet and exceed military standards, demonstrating that the process of this invention can significantly improve the comprehensive mechanical properties of Inconel 718 alloy rings, meeting the high performance and reliability requirements of key aircraft engine components.

[0081] like Figure 11 Figure 2 shows the localized Laves phase morphology in a tensile fracture cross-section. Fine, dispersed Laves phase particles, approximately submicron in size, are visible in the fracture, exhibiting a hierarchical fracture pattern. The fine Laves phase preferentially fractures in a hierarchical pattern during tensile stress, evenly releasing local stress and preventing stress concentration, eliminating the crack source.

[0082] Finally, after machining and peeling, we get Figure 12 Ring forging product shown.

[0083] Example 2: A method for preparing an Inconel 718 alloy ring, comprising the following steps:

[0084] S1: Vacuum Melting. The Inconel 718 alloy raw material is placed in a vacuum induction melting furnace. The vacuum is reduced to below 1 Pa, and then a high-purity argon protective atmosphere is introduced. The raw material is heated under the argon atmosphere until it is completely melted, obtaining an Inconel 718 alloy liquid with a uniform composition.

[0085] S2: Vacuum centrifugal casting. The molten Inconel 718 alloy is held at 1420°C for 10 minutes and then rapidly poured into a 45-grade steel mold. The mold is centrifugally rotated at 600 rpm. The melt fills the mold under high centrifugal force and cools to room temperature in a vacuum environment before the furnace stops rotating, forming a dense, shrinkage-free Inconel 718 cast ring blank.

[0086] S3: Hot Rolling. The centrifugally cast Inconel 718 alloy ring blanks were held at 1000°C for 2 hours and then transferred to a CNC radial-axial rolling mill for hot rolling. The core roller feed speed was set at 1 mm / s, and rolling was performed in two passes. The first pass achieved a 40% reduction; the second pass, performed after the rings had cooled to 800°C, achieved a 40% reduction, bringing the total reduction to 80%. After rolling, the rings were rapidly cooled using water cooling.

[0087] S4: Heat treatment. The hot-rolled Inconel 718 ring forgings were subjected to solution treatment and dual aging treatment. First, the solution treatment was completed by holding at 980°C for 1 hour and then water cooling. Then, the temperature was maintained at 720°C for 8 hours, furnace-cooled to 620°C at a rate of 50°C / h, and then air-cooled to room temperature for aging after holding for another 8 hours. This embodiment further enhanced the effects of strain accumulation and dislocation introduction during controlled rolling and controlled cooling by increasing the total deformation to 80%.

[0088] Example 2 increases the total deformation to 80%. The Inconel 718 alloy rings prepared under this condition still maintain a good level in terms of organizational uniformity, grain refinement and phase transformation control. The room temperature tensile test shows that the tensile strength reaches 1358MPa and the elongation is 27.2%. Both indicators meet and exceed military standards, showing a good match between strength and toughness. However, compared with Example 1, the further increase in deformation, while strengthening recrystallization and Laves phase fragmentation, also promotes more phase transformation of γ'' phase to δ phase, resulting in a relative decrease in the retention of the strengthening phase γ''. Excessive transformation of the γ'' phase weakens the precipitation strengthening effect and becomes a key factor limiting further performance improvement.

[0089] Example 3: A method for preparing an Inconel 718 alloy ring, comprising the following steps:

[0090] S1: Vacuum Melting. The Inconel 718 alloy raw material is placed in a vacuum induction melting furnace. The vacuum is reduced to below 1 Pa, and then a high-purity argon protective atmosphere is introduced. The raw material is heated under the argon atmosphere until it is completely melted, obtaining an Inconel 718 alloy liquid with a uniform composition.

[0091] S2: Vacuum centrifugal casting. The molten Inconel 718 alloy is held at 1420°C for 10 minutes and then rapidly poured into a 45-grade steel mold. The mold is centrifugally rotated at 800 rpm. The melt fills the mold under high centrifugal force and cools to room temperature in a vacuum furnace before the mold is stopped, forming a dense, shrinkage-free Inconel 718 cast ring blank.

[0092] S3: Hot Rolling. The centrifugally cast Inconel 718 alloy ring blanks were held at 1000°C for 2 hours and then transferred to a CNC radial-axial rolling mill for hot rolling. The core roller feed speed was set at 1 mm / s, and rolling was performed in two passes. The first pass achieved a 40% reduction; the second pass, performed after the rings had cooled to 800°C, achieved a 30% reduction, for a total reduction of 70%. After rolling, the rings were rapidly cooled using water cooling.

[0093] S4: Heat Treatment. The hot-rolled Inconel 718 ring forgings undergo solution treatment and dual aging. First, the solution treatment is completed by holding at 980°C for one hour and then water cooling. Then, the ring forging is held at 720°C for eight hours, furnace cooled to 620°C at a rate of 50°C / hour, and then held for another eight hours before air cooling to room temperature for aging.

[0094] In Example 3, the rotation speed of the centrifugal casting stage was adjusted to 800 r / min, thereby further enhancing the density of the cast ring blank and the refinement effect of the primary Laves phase. The subsequent controlled rolling, controlled cooling and heat treatment paths are basically the same as those in Example 1, relying on secondary hot rolling and rapid water cooling to suppress excessive precipitation of the δ phase and maintain the strengthening ability of the γ'' phase. The results of mechanical property tests show that the tensile strength reaches 1384 MPa and the elongation is 26.8%. The performance also far exceeds the military standard, verifying the applicability and stability of the process of the present invention. Although the total amount of deformation is the same as that in Example 1, different initial casting conditions may affect the strain energy storage and precipitation behavior, resulting in slightly different mechanical performance.

[0095] Example 4: A method for preparing an Inconel 718 alloy ring, comprising the following steps:

[0096] S1: Vacuum Melting. The Inconel 718 alloy raw material is placed in a vacuum induction melting furnace. The vacuum is reduced to below 1 Pa, and then a high-purity argon protective atmosphere is introduced. The raw material is heated under the argon atmosphere until it is completely melted, obtaining an Inconel 718 alloy liquid with a uniform composition.

[0097] S2: Vacuum centrifugal casting. The molten Inconel 718 alloy is held at 1420°C for 10 minutes and then rapidly poured into a 45-grade steel mold. The mold is centrifugally rotated at 600 rpm. The melt fills the mold under high centrifugal force and cools to room temperature in a vacuum environment before the furnace stops rotating, forming a dense, shrinkage-free Inconel 718 cast ring blank.

[0098] S3: Hot Rolling. The centrifugally cast Inconel 718 ring blanks were held at 1000°C for 2 hours and then transferred to a CNC radial-axial rolling mill for hot rolling. The core roller feed speed was set at 1 mm / s, and rolling was performed in two passes. The first pass achieved a 40% reduction; the second pass, performed after the ring had cooled to 700°C, achieved a 30% reduction, for a total reduction of 70%. After rolling, the rings were rapidly cooled using water cooling.

[0099] S4: Heat Treatment. The hot-rolled Inconel 718 ring forgings undergo solution treatment and dual aging. First, the solution treatment is completed by holding at 980°C for one hour and then water cooling. Then, the forging is held at 720°C for eight hours, furnace-cooled to 620°C at a rate of 50°C / hour, and then held for another eight hours before air cooling to room temperature to complete the aging treatment. This results in the Inconel 718 alloy ring.

[0100] Based on the controlled rolling and controlled cooling strategy, this embodiment adjusts the starting temperature of the second rolling pass to 700°C, which is still within the lower limit of the hot working temperature range of Inconel 718 alloy. This temperature range has good strain energy accumulation capacity, which helps to introduce higher dislocation density and stress field, and induces the appropriate amount of γ''→δ phase transformation to form a grain boundary pinning network. Figure 13 Figure 2 shows the metallographic structure of the Inconel 718 alloy ring forging prepared in Example 4. The figure shows uniform microstructure, and a local magnified view reveals uniform precipitation of fine δ phase on the grain boundaries, distributed in the form of dots or short rods. The amount of δ phase is slightly lower than that in Example 1 at 800°C, but its size is small, distribution is uniform, and morphology is stable, still effectively achieving grain boundary pinning. This microstructure confirms that under the 700°C hot deformation pass, the degree of γ'' to δ phase transformation is moderate, the strengthening phase is not excessively consumed, and a balance is successfully achieved between recrystallized grain refinement and phase transformation regulation.

[0101] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is only step S3.

[0102] S3: Hot Rolling. The centrifugally cast Inconel 718 alloy ring blanks were held at 1000°C for 2 hours and then transferred to a CNC radial-axial rolling mill for hot rolling. The core roll feed rate was set at 1 mm / s, and rolling was performed in two passes, with a first pass reducing the ring by 40%. This was followed by a second pass, at a temperature of 950°C and a reduction of 30%, for a total reduction of 70%. After rolling, the rings were rapidly cooled using water cooling.

[0103] like Figure 14 As shown, Figure 14 (a) is the microstructure of Inconel 718 alloy ring forging after hot rolling. Figure 14(b) is the microstructure of the Inconel 718 alloy ring after heat treatment. Comparative Example 1 did not adopt a controlled rolling and controlled cooling strategy, and lacked effective regulation of the δ phase precipitation behavior, resulting in a large amount of δ phase precipitation at the grain boundaries during hot rolling, mainly distributed in coarse dendritic or rod-like forms, with clear interface contours and obvious orientation arrangement. After heat treatment, the δ phase further aggregated and grew, still retaining a dendritic or flaky morphology, with short rods or fragmented states appearing locally. Due to the lack of the controlled rolling and controlled cooling process to inhibit the phase transformation process, the γ″ strengthening phase is transformed into the δ phase in large quantities during hot working, which not only weakens the role of the strengthening phase, but also increases the risk of grain boundary embrittlement, thereby adversely affecting the structural stability and mechanical properties of the material.

[0104] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is only step S3.

[0105] S3: Hot Rolling. The centrifugally cast Inconel 718 alloy ring blanks were held at 1000°C for 2 hours and then transferred to a CNC radial-axial rolling mill for hot rolling. The core roller feed speed was set at 1 mm / s, and rolling was performed in two passes. The first pass achieved a 40% reduction; the second pass, performed after the rings had cooled to 800°C, achieved a 30% reduction, bringing the total reduction to 70%. After rolling, the rings were air-cooled.

[0106] like Figure 15 As shown, Figure 15 (a) is the microstructure of Inconel 718 alloy ring forging after hot rolling. Figure 15 (b) shows the microstructure of the Inconel 718 alloy ring after subsequent heat treatment. Comparative Example 2 used air cooling instead of water cooling during hot rolling, lacking effective control over the evolution of the Laves phase morphology. As a result, the Laves phase remained distributed in a coarse, dendritic eutectic form after hot rolling, with a clear interface profile and failure to achieve metastable refinement. After heat treatment, portions of the Laves phase remained in a dendritic or flaky morphology, with no effective fragmentation or dissolution. Due to the insufficient cooling rate, the coarse growth of the Laves phase at high temperatures could not be suppressed, hindering subsequent structural homogenization and performance improvement.

[0107] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is only step S3.

[0108] S3: Hot Rolling. The centrifugally cast Inconel 718 alloy ring blanks were held at 1000°C for 2 hours and then transferred to a CNC radial-axial rolling mill for hot rolling. The core roller feed speed was set at 1 mm / s, and rolling was performed in two passes. The first pass achieved a 30% reduction; the second pass, performed after the ring had cooled to 800°C, achieved a 20% reduction, for a total reduction of 50%. After rolling, the rings were rapidly cooled using water cooling to obtain Inconel 718 alloy ring forgings.

[0109] like Figure 16 As shown, Figure 16 (a) is the microstructure of Inconel 718 alloy ring forging after hot rolling. Figure 16 (b) Microstructure of the Inconel 718 alloy ring after subsequent heat treatment. The second-pass reduction and total reduction were both low, resulting in a coarse, blocky Laves phase with distinct boundaries and irregular morphology after hot rolling. After heat treatment, the Laves phase morphology changes somewhat, but a dendritic or lamellar structure is still observed. Some particles exhibit short rod-like or fragmented morphologies, demonstrating the Laves phase's thermal stability under high-temperature heat treatment conditions.

[0110] like Figure 17 Figure 2 shows the EBSD grain orientation map of the Inconel 718 alloy ring from Comparative Example 3. The map shows generally large grains, with some exhibiting elongated or blocky distribution. The grain morphology is irregular, and the grain boundaries are distinct. Due to insufficient deformation and inadequate dynamic recrystallization, effective grain refinement was not achieved, resulting in a large number of coarse grains remaining in the microstructure and unsatisfactory grain refinement.

[0111] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is only step S2.

[0112] S2: Vacuum centrifugal casting. The molten Inconel 718 alloy is held at 1500°C for 10 minutes and then rapidly poured into a 45-grade steel mold. The mold is centrifugally rotated at 600 rpm. The melt fills the mold under high centrifugal force and cools to room temperature in a vacuum furnace before stopping, forming the Inconel 718 cast ring billet.

[0113] This comparative example does not optimize the centrifugal casting process parameters, and the pouring temperature is too high. Figure 18(a) shows the Laves phase microstructure of an Inconel 718 alloy cast ring. This phase precipitates primarily along grain boundaries, exhibiting irregular, blocky, and dendritic eutectic structures. The Laves phase is relatively large, with significant aggregation in some areas, exceeding 10 μm in length, and exhibiting a distinctly coarsened state. The Laves phase exhibits distinct boundaries and strong interfacial tension, which can easily lead to structural discontinuities and stress concentration areas. Excessively high pouring temperatures prolong solidification time and exacerbate Nb segregation between dendrites, prompting the Laves phase to preferentially grow at the end of solidification, making it difficult to suppress the formation of a coarse morphology. Despite the presence of a coarsened Laves phase in the cast ring, the overall casting still possesses a certain degree of density, with no macroscopic crack defects, allowing the test to proceed smoothly to the hot rolling and heat treatment stages. Figure 18 (b) shows the distribution of the Laves phase in the final ring prepared in Comparative Example 4. After thermal processing and heat treatment, the Laves phase is still widely present and cannot be effectively broken and dissolved. A large number of coarse block or flaky residues remain in the structure, cross-linked with each other and distributed at the grain boundaries. This morphology is significantly different from the submicron-scale, diffusely distributed fine Laves phase in Example 1, indicating that the unoptimized casting temperature will significantly reduce the subsequent phase control ability and hinder the process of structural homogenization. Ultimately, the mechanical properties of the ring prepared in this comparative example are poor, and the tensile strength and plasticity level are significantly lower than the optimized implementation path of the present invention, verifying the necessity of a reasonable temperature window for Laves phase refinement control in the high-temperature centrifugal casting process.

[0114] Comparative Example 5: The preparation method of Inconel 718 alloy rings in a short process is carried out according to the following steps:

[0115] S1: Vacuum Melting. The Inconel 718 alloy raw material is placed in a vacuum induction melting furnace. The vacuum is reduced to below 1 Pa, and then a high-purity argon protective atmosphere is introduced. The raw material is heated under the argon atmosphere until it is completely melted, obtaining an Inconel 718 alloy liquid with a uniform composition.

[0116] S2: Vacuum centrifugal casting: The molten Inconel 718 alloy liquid is kept at 1420°C for 10 minutes and quickly poured into a metal mold made of 45 steel. The mold is centrifugally rotated at 600 rpm.

[0117] S3: Hot Rolling. The centrifugally cast Inconel 718 alloy ring blanks were held at 1000°C for 2 hours and then transferred to a CNC radial-axial rolling mill for hot rolling. The core roller feed speed was set at 1 mm / s, and rolling was performed in two passes. The first pass achieved a 50% reduction; the second pass, performed after the ring had cooled to 800°C, achieved a 30% reduction, for a total reduction of 80%. After rolling, the rings were rapidly cooled using water cooling to obtain Inconel 718 alloy ring forgings.

[0118] like Figure 19 The figure shows a cross-sectional macroscopic photograph of the Inconel 718 alloy ring forging prepared in Comparative Example 5. It can be seen that there are obvious macroscopic cracking defects on the inner and outer surfaces of the specimen. The cracks extend along the deformation direction and penetrate multiple grain areas. The crack boundaries are clear, which are typical high-strain induced cracks. This type of defect seriously damages the continuity and structural integrity of the material and cannot meet the subsequent machining and service requirements. In the first deformation process, the comparative example designed a single-pass reduction of 50%. The internal stress release channel of the material is insufficient, and the uniform dynamic recrystallization process cannot be effectively initiated, resulting in stress-strain accumulation in local areas, and then early cracking.

[0119] Comparative Example 6: The preparation method of Inconel 718 alloy rings in a short process is carried out according to the following steps:

[0120] S1: Vacuum Melting. The Inconel 718 alloy raw material is placed in a vacuum induction melting furnace. The vacuum is reduced to below 1 Pa, and then a high-purity argon protective atmosphere is introduced. The raw material is heated under the argon atmosphere until it is completely melted, obtaining an Inconel 718 alloy liquid with a uniform composition.

[0121] S2: Vacuum centrifugal casting. The smelted Inconel 718 alloy liquid is kept at 1420℃ for 10 minutes and quickly poured into a metal mold made of 45# steel. The mold is centrifugally rotated at 400r / min. The melt is filled into the mold under high centrifugal force and cooled to room temperature in a vacuum environment. Then the rotation is stopped to obtain the Inconel 718 alloy casting ring billet. After taking out the casting ring billet and observing it, as shown in the following figure: Figure 20 As shown in the figure, there are serious defects on the inner wall that are visible to the naked eye. Analysis shows that the defect is caused by insufficient centrifugal field strength, which prevents the melt from fully filling the mold and forming a complete and dense cast ring blank, making it impossible to enter the subsequent hot rolling process.

[0122] Comparative Example 7: The preparation method of Inconel 718 alloy rings in a short process is carried out according to the following steps:

[0123] S1: Vacuum Melting. The Inconel 718 alloy raw material is placed in a vacuum induction melting furnace. The vacuum is reduced to below 1 Pa, and then a high-purity argon protective atmosphere is introduced. The raw material is heated under the argon atmosphere until it is completely melted, obtaining an Inconel 718 alloy liquid with a uniform composition.

[0124] S2: Vacuum centrifugal casting: The molten Inconel 718 alloy is kept at 1420°C for 10 minutes and then quickly poured into a metal mold made of 45 steel. The mold is centrifugally rotated at 600 rpm.

[0125] S3: Hot Rolling. The centrifugally cast Inconel 718 alloy ring blanks were held at 1000°C for 2 hours and then transferred to a CNC radial-axial rolling mill for hot rolling. The core roller feed speed was set at 1 mm / s, and rolling was performed in two passes. The first pass achieved a 40% reduction; the second pass, performed after the ring had cooled to 550°C, achieved a 30% reduction, for a total reduction of 70%. After rolling, the rings were rapidly cooled using water cooling to obtain Inconel 718 alloy ring forgings.

[0126] like Figure 21 Shown is the metallographic structure diagram of the Inconel 718 alloy ring forging prepared in Comparative Example 7. Microcracks can be observed along the grain boundary direction in the figure. The difference between Comparative Example 7 and Example 1 is that the starting temperature of the second hot rolling in step S3 is significantly reduced to only 550°C, which is lower than the lower limit of the recommended hot working temperature zone of Inconel 718 alloy. The plasticity of the material in this temperature range decreases significantly, the dynamic recovery and recrystallization capabilities are insufficient, and the deformation resistance increases significantly. Continuing to apply 30% deformation at this temperature will cause a sharp accumulation of dislocation density, and the internal stress of the organization cannot be released in time, thereby forming micro crack sources at the grain boundaries.

[0127] Comparative Example 8: The preparation method of Inconel 718 alloy rings in a short process is carried out according to the following steps:

[0128] S1: Vacuum Melting. The Inconel 718 alloy raw material is placed in a vacuum induction melting furnace. The vacuum is reduced to below 1 Pa, and then a high-purity argon protective atmosphere is introduced. The raw material is heated under the argon atmosphere until it is completely melted, obtaining an Inconel 718 alloy liquid with a uniform composition.

[0129] S2: Vacuum centrifugal casting: The molten Inconel 718 alloy liquid is kept at 1420°C for 10 minutes and quickly poured into a metal mold made of 45 steel. The mold is centrifugally rotated at 600 rpm.

[0130] S3: Hot Rolling. The centrifugally cast Inconel 718 alloy ring blanks were held at 950°C for 2 hours and then transferred to a CNC radial-axial rolling mill for hot rolling. The core roller feed rate was set at 1 mm / s, and rolling was performed in two passes. The first pass achieved a 40% reduction; the second pass, performed after the ring had cooled to 800°C, achieved a 30% reduction, for a total reduction of 70%. After rolling, the rings were rapidly cooled using water cooling to obtain Inconel 718 alloy ring forgings.

[0131] like Figure 22Shown is a macroscopic photograph of the cross section of the Inconel 718 alloy ring forging prepared in Comparative Example 8. It can be observed that there are obvious irregular deformation areas and slight cracking signs on the upper surface of the ring. The surface is wavy along the circumferential direction, and metal tear-like notches appear in local areas, showing that the material has insufficient plastic response and uneven stress release during deformation. As a typical precipitation-strengthened nickel-based alloy, Inconel 718 alloy has a narrow hot working window, and 950°C is close to its critical deformation temperature range. At this temperature, the γ″ strengthening phase is still in the stable phase region. At the same time, the recrystallization driving force is insufficient, and the degree of structural softening is limited, resulting in a significant increase in deformation resistance. The lack of plasticity of the material in the initial stage of rolling makes it difficult to release macroscopic stress concentration, which ultimately manifests as local discontinuities and tear-like openings on the surface, reducing the forming integrity.

[0132] Comparative Example 9: The difference between Comparative Example 9 and Example 1 is only step S3.

[0133] S3: Hot Rolling. The centrifugally cast Inconel 718 alloy ring blanks were held at 1050°C for 2 hours and then transferred to a CNC radial-axial rolling mill for hot rolling. The core roller feed speed was set at 1 mm / s, and rolling was performed in two passes. The first pass achieved a 40% reduction; the second pass, performed after the ring had cooled to 800°C, achieved a 30% reduction, for a total reduction of 70%. After rolling, the rings were rapidly cooled using water cooling to obtain Inconel 718 alloy ring forgings.

[0134] like Figure 23 Shown is the metallographic structure diagram of the Inconel 718 alloy ring forging prepared in Comparative Example 9. The grain size in the figure is obviously coarse, the overall uniformity of the organization is poor, and no obvious grain boundary pinning structure is observed, reflecting that significant grain growth behavior occurs during the coupling process of thermal deformation and heat treatment. The average grain size can be measured in the figure to be about 68μm. The only difference between Comparative Example 9 and Example 1 is that the hot rolling preheating temperature in step S3 is increased from 1000°C to 1050°C. Although the Inconel 718 alloy has good plasticity in this temperature range, the thermal stability of the δ phase is significantly reduced under high temperature and long-term heat preservation conditions, and it is easy to dissolve. In hot rolling, due to the existence of a heat preservation process of several hours, the δ phase is often almost completely dissolved before deformation. Due to the lack of grain growth resistance during the hot deformation process, the recrystallized grains grow abnormally driven by the coupling of strain and temperature, and eventually form Figure 23 The coarse-grained structure shown.

[0135] Room temperature mechanical properties and Laves phase morphology were tested for the Inconel 718 alloy rings prepared in the Examples and Comparative Examples. The results are shown in the following table. Due to technical issues with cracking during the preparation of Comparative Examples 5 to 8, mechanical property testing and Laves phase morphology testing were not performed.

[0136] Table 1. Mechanical properties and tissue testing statistics of examples and comparative examples

[0137]

[0138] According to the above test and analysis results, it is obvious that the Inconel 718 high-temperature alloy ring forgings prepared in Examples 1 to 4 are superior to the comparative examples in terms of mechanical properties, grain refinement effect, and microstructure control ability. The specific performance is as follows:

[0139] (1) In terms of room temperature tensile properties, the tensile strength and elongation of the rings obtained in Examples 1-4 are all better than the military standard (1270 MPa / 15%), and are also significantly higher than the performance of Comparative Examples 1-3, reflecting the significant advantages of the process of the present invention in terms of strength and plasticity coordination.

[0140] (2) In terms of microstructure, the as-cast Laves phase in the examples all achieved submicron refinement and dispersed distribution. However, coarse Laves phases with a size of 10 μm or more were observed in several comparative examples (such as comparative examples 2 and 4), which not only weakened the precipitation ability of the strengthening phase but also may become a source of crack initiation. In addition, the grain size obtained in the examples was controlled between 13.6–14.2 μm, and the grain size reached ASTM grade 9, which is far superior to the coarse grain structure of 68 μm (ASTM grade 5) in comparative example 9.

[0141] (3) In terms of hot working microstructure stability, the present invention effectively regulates the γ''→δ phase transformation behavior through a controlled rolling and controlled cooling strategy, ensuring that the δ phase plays a role in grain boundary pinning while preventing its excessive precipitation from causing grain boundary embrittlement. Comparing the process conditions of Comparative Example 1 and Comparative Example 9, which lack or miscontrol this strategy, the former shows a large amount of δ phase agglomeration, while the latter shows abnormal grain growth due to the complete dissolution of the δ phase, both of which verify the advantages of the present invention in the dimension of phase transformation control.

[0142] (4) In terms of forming stability and defect control, the controlled rolling and cooling path of the present invention significantly improves the structural coordination and plasticity reserve of the material during thermal deformation. Several comparative examples (Comparative Examples 5-8) exhibited obvious cracking failure when the parameters of the present invention were not used.

[0143] The above description is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A short-process method for preparing Inconel 718 alloy rings, characterized in that: The following steps are involved: S1. Place the Inconel 718 alloy material in a vacuum induction melting furnace for vacuum melting to obtain Inconel 718 alloy liquid metal; S2. The Inconel 718 alloy molten metal is poured into a centrifugal casting machine for vacuum centrifugal casting at a pouring temperature of 1420-1450°C and a mold speed of 600-800 r / min until the Inconel 718 alloy molten metal is completely solidified and cooled to room temperature. The centrifugal casting machine is then closed to obtain an Inconel 718 alloy cast ring blank. S3. The Inconel 718 alloy cast ring blank is preheated and then rolled on a rolling mill. The rolling process is performed in two passes. After the first deformation, the Inconel 718 alloy cast ring blank is cooled to below 800°C and then subjected to a second deformation pass to obtain an Inconel 718 alloy ring forging. S4. heat treating the Inconel 718 alloy ring forging, including solution treatment and aging treatment. The solution treatment system is to heat the Inconel 718 alloy ring forging to 950-980°C, hold the temperature for 1 hour, and then cool it with water to obtain the Inconel 718 alloy ring. The aging treatment process is carried out after the solution treatment. The specific aging system is: keeping at 700-730 ° C for 8 hours, then cooling with the furnace to 600-630 ° C at a rate of 50 ° C / h, and then keeping at this temperature for another 8 hours and then air cooling to room temperature to obtain Inconel 718 alloy rings.

2. The method for preparing a short-process Inconel 718 alloy ring according to claim 1, characterized in that: In step S3, the preheat treatment system of the Inconel 718 alloy cast ring blank is to heat the Inconel 718 alloy cast ring blank to 980-1010° C. and keep it warm for 2 hours.

3. The method for preparing a short-process Inconel 718 alloy ring according to claim 1, characterized in that: In step S3, the core roller feed speed of the rolling machine is 0.8-1.5 mm / s.

4. The method for preparing a short-process Inconel 718 alloy ring according to claim 1, characterized in that: In step S3, after the first deformation, the Inconel 718 alloy cast ring blank is cooled to a temperature within a range of 700-800° C. and then subjected to a second deformation.

5. The method for preparing a short-process Inconel 718 alloy ring according to claim 4, characterized in that: In step S3, the first reduction is 30% to 40%, the second reduction is 30% to 40%, and the total reduction of the two rolling and forming passes is 60% to 80%.

6. The method for preparing a short-process Inconel 718 alloy ring according to claim 4, characterized in that: In step S3, water cooling treatment is performed after the second deformation.

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