GH3128 alloy forged bar and preparation method thereof

Abstract

The invention discloses a GH3128 alloy forged bar and a preparation method thereof. The preparation method comprises the following steps: smelting GH3128 alloy according to design components to prepare an alloy ingot; the alloy ingot is subjected to high-temperature homogenization treatment within the temperature range of 1180-1200 DEG C, so that redissolution of carbides is promoted, and the continuous precipitation tendency of grain boundaries is weakened; then multi-heating-number rapid forging cogging is conducted, so that as-cast dendritic crystals are broken, and the structure uniformity is improved; under the condition that the finish forging temperature is not lower than 850 DEG C, one-heating-number 45%-50% large-deformation precision forging is carried out; and finally, the forged bar is cooled, and a GH3128 alloy forged bar finished product is obtained. The GH3128 alloy forged bar prepared through the method shows excellent high-temperature plasticity and durability under the condition of 950 DEG C, the high-temperature tensile elongation is not lower than 100%, the percentage reduction of area is not lower than 90%, the high-temperature durable elongation is not lower than 88%, the durable fracture time is not lower than 40 hours, the high-temperature tensile strength is not lower than 200 MPa, and the GH3128 alloy forged bar is suitable for being used for manufacturing a high-temperature steel bar. The material is suitable for key bearing components under high-temperature service conditions.

Description

Technical Field

[0001] This invention relates to the field of alloy preparation technology, and more specifically, to a GH3128 alloy forged bar and its preparation method. Background Technology

[0002] GH3128 alloy is a nickel-based solid solution strengthened high-temperature alloy with excellent high-temperature strength, oxidation resistance, and corrosion resistance, and is widely used in aerospace, gas turbines, and high-temperature load-bearing components. Under long-term high-temperature service conditions, this type of alloy needs to simultaneously possess high strength, good high-temperature plasticity, and stable creep performance. Forged bars are one of its important product forms. Currently, GH3128 alloy forged bars are typically prepared using conventional composition design and traditional hot working processes. However, in actual production and use, it has been found that with increasing service temperature and extended service time, GH3128 alloy is prone to the formation of unfavorable precipitates within a specific temperature range, especially the precipitation of alloy-rich phases such as μ phase at grain boundaries, exhibiting a continuous or semi-continuous distribution. These unfavorable precipitates typically have high hardness and brittleness, easily becoming crack initiation sources under high-temperature tensile or creep loading conditions, thus significantly reducing the material's high-temperature plasticity and creep life.

[0003] From a technological perspective, existing preparation methods often suffer from problems such as unreasonable selection of homogenization temperature ranges and insufficient homogenization effects. This results in insufficient re-dissolution of carbides and segregated elements in the as-cast microstructure, making them prone to re-precipitation of undesirable phases along grain boundaries during subsequent hot deformation. Meanwhile, traditional forging processes often employ multi-stage, small-deformation precision forging, which, while capable of achieving the desired shape, has limited effect on breaking up as-cast dendrites, resulting in insufficient grain refinement. Furthermore, at lower final forging temperatures, grain boundary precipitates are more likely to distribute continuously, further weakening the material's high-temperature plasticity.

[0004] Furthermore, existing technologies do not pay enough attention to the synergistic relationship between the composition range of GH3128 alloy and hot working processes. There is a lack of systematic matching between the alloy element ratio and the heat treatment and forging windows, making it difficult to ensure high-temperature strength while also taking into account high-temperature plasticity and creep performance. Therefore, how to effectively suppress the formation of unfavorable phases such as μ phase, improve the grain boundary precipitation state, and enhance the plasticity and creep performance of GH3128 alloy forged bars under high-temperature conditions without sacrificing the high-temperature strength of the alloy remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] One of the technical problems to be solved by the present invention is to provide a method for preparing GH3128 alloy forged bars, so as to solve the problem that in the prior art, GH3128 alloy forged bars are prone to precipitation of unfavorable phases such as μ phase, continuous precipitation of grain boundaries, and poor microstructure uniformity, resulting in insufficient high-temperature plasticity and creep performance.

[0006] To overcome the shortcomings of the prior art, the present invention provides a method for preparing GH3128 alloy forged bars, the method comprising the following steps: S1: Composition Design and Melting: Melt the GH3128 alloy according to the designed composition and make it into an alloy ingot; S2: High-temperature homogenization treatment: The alloy ingot is homogenized in the temperature range of 1180-1200℃ to promote carbide redissolution and weaken the tendency of continuous precipitation at grain boundaries. S3: Multi-fire rapid forging: The alloy ingot after homogenization is subjected to multi-fire rapid forging to break up the as-cast dendrites and improve the uniformity of the microstructure. S4: One-time large deformation precision forging: Under the condition that the final forging temperature is not lower than 850℃, the billet after the initial forging is subjected to one-time precision forging to refine the grains and control the precipitation of grain boundary phases. S5: Cooling: Cool the precision-forged bar to obtain GH3128 alloy forged bar.

[0007] Compared with the prior art, the preparation method of GH3128 alloy forged bars of the present invention has the following advantages: The preparation method of GH3128 alloy forged bars of the present invention achieves systematic control over as-cast segregation, dendritic structure and grain boundary precipitation behavior through the synergistic treatment of melting and ingot making, high-temperature homogenization, multi-fire rapid forging, single-fire large deformation precision forging and cooling. Among them, the high-temperature homogenization treatment can promote the diffusion and dissolution of segregating components and carbides in the as-cast structure, thereby weakening the basis for the formation of continuous grain boundary precipitation; while multi-fire rapid forging is beneficial for large cumulative deformation. The process continuously breaks down the as-cast dendritic skeleton and promotes microstructure homogenization, providing a prerequisite for subsequent fine forging. A single-pass fine forging is performed at a final forging temperature of not less than 850℃ to avoid grain boundary embrittlement / precipitation aggravation induced by low-temperature deformation, while achieving significant grain refinement and microstructure densification. The above steps form a synergistic effect of homogenization, breaking down, refining, and stabilization, resulting in a more uniform microstructure and a reduced tendency for continuous grain boundary precipitates in the forged bar. This improves the stability of high-temperature plasticity and high-temperature creep performance without sacrificing high-temperature strength.

[0008] In one possible implementation, in step S1, the designed composition of the GH3128 alloy, by mass proportion, includes: C: 0.02-0.04%, Cr: 19.0-22.0%, W: 7.5-8.5%, Mo: 8.0-8.5%, Ti: 0.5-0.8%, Al: 0.6-0.8%, Fe: 0.2-0.5%, with the balance being Ni and other unavoidable impurities.

[0009] Compared with the prior art, this embodiment limits the composition of GH3128 alloy to the range of C 0.02–0.04%, Cr 19.0–22.0%, W 7.5–8.5%, Mo 8.0–8.5%, Ti 0.5–0.8%, Al 0.6–0.8%, Fe 0.2–0.5% (balance Ni). This can maintain the solid solution strengthening ability of the γ matrix while keeping the content of high melting point strong solid solution elements such as W and Mo within a controllable range, avoiding the tendency of excessive alloying element brittle phase (μ phase) formation. At the same time, the appropriate C content ensures the stable existence of necessary carbide phases without excessive coarsening or continuity along grain boundaries, thereby providing a compositional basis for obtaining a more stable grain boundary state in subsequent heat treatment and forging, which is ultimately conducive to improving the consistency of high-temperature plasticity and creep performance.

[0010] In one possible implementation, the design composition of the GH3128 alloy, by mass proportion, includes: C: 0.028-0.032%, Cr: 20.0-21.5%, W: 7.8-8.2%, Mo: 8.1-8.3%, Ti: 0.58-0.76%, Al: 0.68-0.76%, Fe: 0.25-0.35%, with the balance being Ni and other unavoidable impurities.

[0011] Compared with the prior art, this embodiment further narrows the composition to C 0.028–0.032%, Cr 20.0–21.5%, W 7.8–8.2%, Mo 8.1–8.3%, Ti 0.58–0.76%, Al 0.68–0.76%, Fe 0.25–0.35% (balance Ni), which can more accurately balance the relationship between solid solution strengthening and precipitate formation, so that the γ matrix strengthening elements are in a more stable ratio range, and reduce the sensitivity of grain boundary precipitation and microstructure dispersion caused by composition fluctuations. As a result, the bar material can more easily achieve a stable high level in terms of high-temperature tensile plasticity and creep life, which is suitable for performance consistency control in mass production.

[0012] In one possible implementation, in step S1, the smelting is carried out by a dual smelting process of vacuum induction melting and electroslag remelting.

[0013] Compared with a single smelting process, the dual smelting method of vacuum induction melting and electroslag remelting in this embodiment can significantly reduce the content of inclusions and gases. Furthermore, the secondary purification effect of electroslag remelting improves the size and distribution uniformity of inclusions, thereby reducing the risk of inclusions acting as crack initiators and inducing early cracking under high-temperature tensile and sustained loading.

[0014] In one possible implementation, in step S2, the homogenization process is carried out at a temperature of 1190°C for 20-40 hours.

[0015] Compared to conventional methods that suffer from insufficient homogenization or inadequate diffusion due to low temperature / time, this embodiment further limits the homogenization temperature and time. Holding at 1190°C for 20–40 hours significantly enhances the diffusion of alloying elements and the re-dissolution process of carbides, which more fully weakens dendritic segregation in the as-cast state and reduces continuous precipitation caused by enrichment at grain boundaries during subsequent hot deformation. The 20–40 hour time window ensures sufficient diffusion homogenization while avoiding the risk of abnormal grain growth or microstructure coarsening due to excessively long holding time. This lays the foundation for obtaining a fine and uniform microstructure and improving high-temperature plasticity and creep performance during subsequent forging.

[0016] In one possible implementation, in step S3, the initial heating temperature of the multi-fire rapid forging is 1160-1180℃, the final heating temperature is 1140-1160℃, and the final forging temperature is controlled at 850-900℃.

[0017] Compared with the prior art, this embodiment limits the billet heating temperature to 1160–1180℃, which allows the alloy to be in a deformation range with good high-temperature plasticity, enabling full deformation and effective breaking of the as-cast structure. The final heating temperature of 1140–1160℃ can reduce the risk of overheating while ensuring the subsequent deformation capacity, and inhibit the formation of coarse grains and unfavorable precipitates at grain boundaries. The final forging temperature of 850–900℃ avoids grain boundary embrittlement and precipitation aggravation caused by excessively low final forging temperature, while retaining a certain recrystallization / recovery capacity to obtain a more uniform and refined structure, ultimately improving high-temperature plasticity and creep performance.

[0018] In one possible implementation, step S3, the multi-fire rapid forging billet opening includes 3-5 fires of forging.

[0019] Compared with existing technologies, 3–5 heating cycles can form a more sufficient cumulative forging ratio during the segmented heating and deformation process, so that the cast dendritic skeleton and segregation bands are gradually broken and pulled apart, thereby significantly improving the uniformity of the structure. Controlling the heating cycles to within 5 times can avoid the risks of grain coarsening and repeated growth of grain boundary precipitates caused by excessive thermal cycling, thus achieving both microstructure refinement and stability.

[0020] In one possible implementation, in step S4, the deformation amount of the single-pass precision forging is 45%-50%.

[0021] Compared with existing technologies, the above-mentioned technical solution can significantly promote dynamic recrystallization and grain refinement through a large deformation of 45-50%, and reduce the difference in grain size between the outer edge and the center of the bar by homogenizing the cross-sectional strain distribution through strong plastic deformation, thereby improving the uniformity of the microstructure. At the same time, limiting the deformation to within 50% can avoid the risk of excessive temperature drop, surface damage or cracking caused by excessive deformation, so as to obtain a fine and uniform microstructure more stably under the condition that the final forging temperature is not lower than 850℃. Therefore, higher and more stable high-temperature ductility and service life are also obtained.

[0022] One of the technical problems to be solved by the present invention is to provide a GH3128 alloy forged bar to solve the problems of insufficient high-temperature plasticity and large fluctuations in high-temperature creep performance of GH3128 alloy forged bars under high-temperature service conditions, and the difficulty in simultaneously improving plasticity and creep performance while ensuring high-temperature strength.

[0023] To overcome the shortcomings of the prior art, the present invention provides a GH3128 alloy forged bar, which is prepared by the above-described preparation method.

[0024] In one possible implementation, the forged bar stock meets the following performance indicators at a test temperature of 950°C: (a) High-temperature tensile elongation A ≥ 100%; (b) High-temperature tensile reduction of area Z ≥ 90%; (c) High-temperature creep elongation A ≥ 88%; (d) High-temperature sustained fracture time τ ≥ 40 hours; (e) High-temperature tensile strength Rm ≥ 200 MPa.

[0025] Compared with the prior art, the GH3128 alloy forged bar of the present invention has the following advantages: The GH3128 alloy forged bar of the present invention achieves a significant and stable improvement in high-temperature plasticity and high-temperature creep performance without reducing the high-temperature strength level of the alloy. The forged bar of the present invention simultaneously possesses a high-temperature tensile elongation of over 100%, a high reduction of area, and a high-temperature creep fracture time of over 40 hours at 950℃. It exhibits excellent deformation capacity and long-term service reliability under high-temperature loading conditions. Through the synergistic control of composition design and the heat-deformation process, the present invention ensures the stable existence of the γ phase in the GH3128 alloy matrix while significantly reducing the tendency of unfavorable phases such as the μ phase to continuously precipitate at grain boundaries, thereby weakening the grain boundary embrittlement source. Simultaneously, the resulting forged bar has a more uniform microstructure, finer grains, and a more dispersed distribution of grain boundary precipitates, avoiding the problem of limited high-temperature plasticity and creep performance caused by uneven microstructure or continuous grain boundary precipitation in the prior art. The GH3128 alloy forged bar of the present invention maintains a high-temperature tensile strength of not less than 200... While achieving MPa, it simultaneously improves high-temperature plasticity and high-temperature creep performance, fundamentally solving the technical defects of existing GH3128 alloy forged bars that have acceptable strength but insufficient plasticity and creep performance, and has significant engineering application value. Attached Figure Description

[0026] Figure 1 The graph shows a comparison of the thermodynamic calculation results of the volume fraction (Vol.%) of each phase with temperature at different temperatures between the GH3128 alloy prepared in Example 2 and the comparative example. The left graph corresponds to the comparative example, and the right graph corresponds to Example 2. Figure 2 The images show a comparison of the microstructure of the GH3128 alloy forged bar obtained in Example 2 and the comparative example, where (a) is the microstructure of the comparative example and (b) is the microstructure of Example 2 after optimization. Figure 3 This is a scanning electron microscope (SEM) image of the GH3128 alloy forged bar obtained in Example 2. Detailed Implementation

[0027] First, those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0028] This invention provides a method for preparing GH3128 alloy forged bars, the method comprising the following steps: S1: Composition Design and Melting: Melt the GH3128 alloy according to the designed composition and make it into an alloy ingot; S2: High-temperature homogenization treatment: The alloy ingot is homogenized in the temperature range of 1180-1200℃ to promote carbide redissolution and weaken the tendency of continuous precipitation at grain boundaries. S3: Multi-fire rapid forging: The alloy ingot after homogenization is subjected to multi-fire rapid forging to break up the as-cast dendrites and improve the uniformity of the microstructure. S4: One-time large deformation precision forging: Under the condition that the final forging temperature is not lower than 850℃, the billet after the initial forging is subjected to one-time precision forging to refine the grains and control the precipitation of grain boundary phases. S5: Cooling: Cool the precision-forged bar to obtain GH3128 alloy forged bar.

[0029] As a preferred embodiment, in step S1, the design composition of the GH3128 alloy, by mass ratio, includes: C: 0.02-0.04%, Cr: 19.0-22.0%, W: 7.5-8.5%, Mo: 8.0-8.5%, Ti: 0.5-0.8%, Al: 0.6-0.8%, Fe: 0.2-0.5%, with the balance being Ni and other unavoidable impurities.

[0030] As a preferred embodiment, the design composition of the GH3128 alloy, by mass ratio, includes: C: 0.028-0.032%, Cr: 20.0-21.5%, W: 7.8-8.2%, Mo: 8.1-8.3%, Ti: 0.58-0.76%, Al: 0.68-0.76%, Fe: 0.25-0.35%, with the balance being Ni and other unavoidable impurities.

[0031] As a preferred embodiment, in step S1, the smelting adopts a dual smelting process of vacuum induction melting and electroslag remelting.

[0032] As a preferred embodiment, in step S2, the homogenization treatment is carried out at a temperature of 1190°C for 20-40 hours.

[0033] As a preferred embodiment, in step S3, the initial heating temperature of the multi-fire rapid forging is 1160-1180℃, the final heating temperature is 1140-1160℃, and the final forging temperature is controlled at 850-900℃.

[0034] As a preferred embodiment, in step S3, the multi-fire rapid forging blanking includes 3-5 fires of forging.

[0035] As a preferred embodiment, in step S4, the deformation amount of the single-pass precision forging is 45%-50%.

[0036] This invention provides a GH3128 alloy forged bar, which is prepared by the above-described method.

[0037] As a preferred embodiment, the forged bar meets the following performance indicators at a test temperature of 950℃: (a) High-temperature tensile elongation A ≥ 100%; (b) High-temperature tensile reduction of area Z ≥ 90%; (c) High-temperature creep elongation A ≥ 88%; (d) High-temperature sustained fracture time τ ≥ 40 hours; (e) High-temperature tensile strength Rm ≥ 200 MPa.

[0038] This invention provides a GH3128 alloy forged bar and its preparation method. Through a combination of processes including billet preparation, vacuum induction melting, electroslag remelting, high-temperature homogenization treatment, multi-stage forging, and single-stage large-deformation precision forging, coupled with optimized alloy composition design and a reasonable forging deformation regime, high-quality GH3128 alloy forged bars with uniform microstructure and stable performance are successfully prepared. This invention optimizes and controls the composition of the GH3128 alloy, stabilizing the C content at approximately 0.02-0.04%, and rationally matching the contents of alloying elements such as W, Mo, and Cr, effectively suppressing the μ phase within the typical processing and service temperature range of 850-950℃. The precipitation of harmful phases improves the microstructure stability of the alloy from a compositional perspective. Simultaneously, a high-temperature homogenization process further dissolves carbides in the as-cast microstructure, reducing the tendency for elemental segregation and continuous grain boundary precipitation. Furthermore, the use of a 45-50% single-fire large deformation precision forging process effectively refines the grains and improves microstructure uniformity, allowing the grain size difference between the outer edge and center of the forged bar to be controlled within a small range. This significantly enhances the high-temperature plasticity and comprehensive mechanical properties of the material. This invention achieves simultaneous improvement in high-temperature plasticity and creep resistance without reducing the high-temperature strength level of the GH3128 alloy, demonstrating significant technological advancement and engineering application value.

[0039] Example 1 This embodiment provides a GH3128 alloy forged bar and its preparation method. The finished bar has a diameter of Φ180 mm. The GH3128 alloy forged bar is prepared by this method, which includes the following steps: S1: Composition Design and Melting The GH3128 alloy was melted and made into alloy ingots according to the following mass percentage composition: C: 0.03%, Cr: 21.5%, W: 8.13%, Mo: 8.12%, Ti: 0.62%, Al: 0.69%, Ni: 60.45%, Fe: 0.35%.

[0040] S2: High-temperature homogenization treatment The alloy ingot is subjected to a high-temperature homogenization treatment at 1190°C. This homogenization treatment further dissolves carbides in the as-cast microstructure and reduces the tendency for continuous precipitation at grain boundaries, thus providing a basis for achieving microstructure homogenization in the subsequent forging process.

[0041] S3: Multi-fire rapid forging billet The homogenized alloy ingots were subjected to initial forging: the initial heating temperature was 1169℃; the final heating temperature was 1153℃; and the final forging temperature during the initial forging process was controlled at ≥850℃. Through multi-stage rapid initial forging, the as-cast dendrites can be broken up and the microstructure homogeneity improved.

[0042] S4: One-shot large deformation precision forging The billet after the initial forging is subjected to one-time precision forging, and the deformation amount is controlled at 48%. The above deformation amount is beneficial to improve the uniformity of the microstructure, so that the difference between the outer edge grain size and the center grain size of the forging bar can be controlled within 2 levels, and good high-temperature plasticity is obtained. During the precision forging process, the final forging temperature is controlled not to be lower than 850℃.

[0043] S5: After cooling and precision forging, the forged bar is cooled to obtain the finished GH3128 alloy forged bar.

[0044] Performance testing The obtained bars were subjected to high-temperature tensile and high-temperature creep performance tests at 950℃. Two-sample tests were conducted, and the results are as follows: Sample 1: High-temperature tensile elongation A=100.00%, Rm=210.00 MPa, reduction of area Z=90.00%; High-temperature creep elongation A=89.00%, creep fracture time τ=43.98 h; Sample 2: High temperature tensile elongation A=102.50%, Rm=212.00 MPa, reduction of area Z=91.00%; high temperature creep elongation A=93.00%, creep fracture time τ=40.30 h.

[0045] Example 2 This embodiment provides a GH3128 alloy forged bar and its preparation method. The finished bar has a diameter of Φ180 mm. The GH3128 alloy forged bar is prepared by this method, which includes the following steps: S1: Composition Design and Melting The GH3128 alloy was melted and made into alloy ingots according to the following mass percentage composition: C: 0.03%, Cr: 20.1%, W: 7.9%, Mo: 8.19%, Ti: 0.60%, Al: 0.74%, Ni: 62.18%, Fe: 0.26%.

[0046] S2: High-temperature homogenization treatment The alloy ingot is subjected to high-temperature homogenization treatment at a temperature of 1190°C to promote carbide re-dissolution and reduce the tendency for continuous precipitation at grain boundaries.

[0047] S3: Multi-fire rapid forging billet The homogenized alloy ingot is subjected to billet forging: the billet heating temperature is 1170℃; the final heating temperature is 1150℃; the final forging temperature during the billet process is controlled at ≥850℃ to ensure the temperature and microstructure of the subsequent precision forging.

[0048] S4: One-shot large deformation precision forging The billet after roughing is subjected to one-time precision forging, with the forging deformation controlled at 45%; the final forging temperature is controlled at no less than 850℃ during the precision forging process; through deformation of more than 45% combined with homogenization treatment, the uniformity of the microstructure can be significantly improved and the unfavorable precipitates at grain boundaries can be suppressed.

[0049] S5: Cooling After precision forging, the forged bar is cooled to obtain the finished GH3128 alloy forged bar.

[0050] Organization and performance testing High-temperature tensile and high-temperature creep performance tests were conducted at 950℃ using two specimens. The results are as follows: Sample 1: High-temperature tensile elongation A=109.00%, Rm=203.00 MPa, reduction of area Z=92.00%; High-temperature creep elongation A=96.00%, creep rupture time τ=47.60 h; Sample 2: High temperature tensile elongation A=106.00%, Rm=215.00 MPa, reduction of area Z=92.00%; high temperature creep elongation A=99.00%, creep fracture time τ=48.60 h.

[0051] To compare and verify the improvement effect of the method of the present invention on the high-temperature plasticity and creep rupture properties of GH3128 alloy forged bars, bars of the same grade GH3128 alloy and the same specification (Φ180 mm) were selected as comparative examples. The comparative examples were prepared using the company's conventional forging bar manufacturing process. Compared with the embodiments of the present invention, the process route did not employ the high-temperature homogenization temperature range and the subsequent single-pass large deformation precision forging control conditions defined by the present invention. The high-temperature tensile and high-temperature creep rupture properties of the comparative examples were tested at the same test temperature (950℃) and using the same test method as the embodiments. The test results are shown in Table 1.

[0052] The alloy composition of the comparative GH3128 alloy forging bar is C: 0.035-0.040%, Cr: 20.1%, W: 8.5%, Mo: 8.5%, Ti: 0.60%, Al: 0.74%, Ni: 62.18%, Fe: 0.26% (high carbon, high W, high Mo).

[0053] It adopts a high-temperature homogenization process of 1180℃, which is 10℃ lower than the improved process.

[0054] The process employs a heating temperature of 1160℃±10℃ for billet preparation, a final heating temperature of 1130℃±10℃, and a final forging temperature controlled below 850℃. Before the improvement, the initial heating and final heating temperatures were lower, and the final forging temperature was sometimes below 850℃. This lower forging temperature is detrimental to carbide breakage, hinders carbide elimination, carbide aggregation, and banding, resulting in reduced and unstable overall mechanical properties.

[0055] The precision forging deformation is controlled at 35-40%. If the deformation rate is too small, it will be difficult to control the grain size and improve the mechanical properties. After improvement, the total deformation rate is increased by more than 45%, and a large deformation pass is designed with a pass deformation rate of ≥23%, which effectively controls the grain size of the finished product and improves the mechanical properties.

[0056] Table 1: Test results of sample performance in Examples 1-2 and comparative examples Table 1 shows the comparison results of the high-temperature tensile properties and high-temperature creep properties of GH3128 alloy forged bars at 950℃, including standard requirements, comparative test values, and test values ​​of Examples 1 and 2 prepared using the method of this invention. As shown in Table 1, compared with the samples before the improvement (high-temperature tensile elongation A: 75.00%-87.50%, reduction of area Z: 88.00%-90.00%, high-temperature creep rupture elongation A: 56.00%-65.00%, creep rupture time τ: 32.30-35.98 h), the high-temperature plasticity and creep rupture properties of Examples 1 and 2 of the present invention are significantly improved. The high-temperature tensile elongation A increases to 100.00%-109.00%, the reduction of area Z increases to 90.00%-92.00%, the high-temperature creep rupture elongation A increases to 89.00%-99.00%, and the creep rupture time τ increases to 40.30-48.60 h; at the same time, the high-temperature tensile strength Rm remains at the level of 203.00-215.00 MPa, compared with 214.00-219.00 MPa before the improvement. The MPa is on the same order of magnitude as the overall strength, indicating that the present invention achieves simultaneous improvement of high-temperature plasticity and high-temperature creep performance without significantly reducing high-temperature strength, thus verifying the effectiveness of the method of the present invention in improving the high-temperature service performance of GH3128 alloy forged bars.

[0057] like Figure 1 As shown, Figure 1 This is a comparison of the thermodynamic calculation results of the GH3128 alloy prepared in Example 2 of this invention and the comparative example at different temperatures, showing the change of each phase volume fraction (Vol.%) with temperature. The left figure is the comparative example group before optimization, and the right figure is the Example 2 group after optimization. The comparison shows that within the temperature range of approximately 700-900℃ (… Figure 1 The low-phase content range shown in the red box indicates that, in addition to the γ matrix phase, the alloy before optimization still contains a certain proportion of low-content precipitates. Among them, the μ phase (MU) gradually decreases with increasing temperature, but its disappearance temperature is relatively high, approaching zero only when it reaches approximately 900℃. In contrast, the overall amount of μ phase precipitation in the optimized alloy is reduced, and its decay with increasing temperature is faster, decreasing to near zero in a lower temperature range. Therefore, in the range corresponding to the subsequent final forging temperature window (e.g., 850-900℃), the μ phase precipitation tendency of the optimized alloy is significantly weakened, which helps to avoid the adverse effects of μ phase on high-temperature plasticity. At the same time, the volume fraction of other low-content phases (e.g., M6C, M23C6, M3B2, etc.) is also at a low level, indicating that the optimized alloy has better microstructure stability in the target processing temperature range.

[0058] like Figure 2 As shown, Figure 2Comparison of the microstructures of the rods prepared in Example 2, where (a) is the microstructure of the control state and (b) is the microstructure after optimization (scale bar is 20 μm). Figure 2 (a) It can be observed that there are many dispersed precipitates in the matrix, and a μ phase appears in local areas (indicated by the arrows in the figure). Meanwhile, the precipitate distribution near the grain boundaries is more pronounced. Figure 2 (b) shows clear grain outlines, a significant reduction in continuous precipitates at grain boundaries, a cleaner overall microstructure, and a decreasing trend in both the number and size of precipitates. This comparison further illustrates that the key heat / deformation window in the preparation method of this invention is rationally controlled, effectively improving the grain boundary precipitation state and reducing the probability of unfavorable phases such as μ phase, thereby contributing to obtaining more stable high-temperature plasticity.

[0059] like Figure 3 As shown, Figure 3 The image shows the scanning electron microscope (SEM) morphology of the rod obtained in Example 2 (accelerating voltage 15 kV, magnification × 500, scale bar 50 μm). Figure 2 As can be seen, the matrix region obtained in Example 2 is relatively uniform, and the precipitated particles exist in a small, fine, and dispersed form, without obvious large-sized continuous precipitate bands or coarse aggregates; a small number of nearly circular or dot-shaped particles are visible locally, and the overall precipitation exhibits a diffuse, fine, and relatively uniform distribution characteristic; this morphological result is consistent with... Figure 2 The gold-coated structure echoes the design, demonstrating that the present invention can reduce the tendency of unfavorable phases / coarse precipitates to form through synergistic control of the preparation method and alloy composition, thereby improving the microstructure stability and mechanical properties of the material under high-temperature conditions.

[0060] In summary, through a systematic comparison of Examples 1 and 2 with the comparative examples, it can be seen that the GH3128 alloy forging bar preparation method proposed in this invention can significantly improve its high-temperature plasticity and high-temperature creep performance without reducing the high-temperature strength level of the alloy. Within the GH3128 alloy composition design range, this invention, through the reasonable matching of the contents of key alloying elements such as Cr, W, Mo, Ti, and Al, ensures the stable existence of the matrix γ phase while reducing the tendency for the formation of unfavorable phases such as the μ phase, providing a favorable thermodynamic basis for subsequent microstructure control from the compositional level. Furthermore, this invention further controls the high-temperature homogenization treatment temperature at 1180-120°C. Within the 0℃ range, the carbides in the as-cast microstructure are fully dissolved, weakening the driving force for continuous precipitation of the μ phase at grain boundaries from the source. Combined with the synergistic control of multi-stage rapid forging and single-stage 45%-50% large deformation precision forging, while ensuring the final forging temperature is not lower than 850℃, this effectively breaks up as-cast dendrites, refines grains, and significantly improves microstructure uniformity. Through the synergistic effect of composition design and hot deformation process, this invention maintains a more stable and uniform microstructure in the temperature range relevant to actual processing and service, significantly reducing the adverse effects of unfavorable grain boundary precipitation on high-temperature plasticity. High-temperature tensile elongation, high-temperature creep elongation, and creep fracture time are simultaneously improved. This invention, through the synergistic optimization of composition control and preparation process, effectively solves the problems of insufficient plasticity and limited creep performance of existing GH3128 alloy forged bars under high-temperature service conditions, demonstrating significant technological advancement and engineering application value.

[0061] In the description of this invention, the references to "one embodiment," "some embodiments," "in this embodiment," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0062] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing GH3128 alloy forged bars, characterized in that, The method includes the following steps: S1: Composition Design and Melting: Melt the GH3128 alloy according to the designed composition and make it into an alloy ingot; S2: High-temperature homogenization treatment: The alloy ingot is homogenized in the temperature range of 1180-1200℃ to promote carbide redissolution and weaken the tendency of continuous precipitation at grain boundaries. S3: Multi-fire rapid forging: The alloy ingot after homogenization is subjected to multi-fire rapid forging to break up the as-cast dendrites and improve the uniformity of the microstructure. S4: One-time large deformation precision forging: Under the condition that the final forging temperature is not lower than 850℃, the billet after the initial forging is subjected to one-time precision forging to refine the grains and control the precipitation of grain boundary phases. S5: Cooling: Cool the precision-forged bar to obtain GH3128 alloy forged bar.

2. The method for preparing GH3128 alloy forged bars according to claim 1, characterized in that, In step S1, the design composition of the GH3128 alloy, by mass ratio, includes: C: 0.02-0.04%, Cr: 19.0-22.0%, W: 7.5-8.5%, Mo: 8.0-8.5%, Ti: 0.5-0.8%, Al: 0.6-0.8%, Fe: 0.2-0.5%, with the balance being Ni and other unavoidable impurities.

3. The method for preparing GH3128 alloy forged bars according to claim 2, characterized in that, The design composition of the GH3128 alloy, by mass ratio, includes: C: 0.028-0.032%, Cr: 20.0-21.5%, W: 7.8-8.2%, Mo: 8.1-8.3%, Ti: 0.58-0.76%, Al: 0.68-0.76%, Fe: 0.25-0.35%, with the balance being Ni and other unavoidable impurities.

4. The method for preparing GH3128 alloy forged bars according to claim 1, characterized in that, In step S1, the smelting adopts a dual smelting method of vacuum induction melting and electroslag remelting.

5. The method for preparing GH3128 alloy forged bars according to claim 1, characterized in that, In step S2, the homogenization process is carried out at a temperature of 1190°C for 20-40 hours.

6. The method for preparing GH3128 alloy forged bars according to claim 1, characterized in that, In step S3, the initial heating temperature of the multi-fire rapid forging is 1160-1180℃, the final heating temperature is 1140-1160℃, and the final forging temperature is controlled at 850-900℃.

7. The method for preparing GH3128 alloy forged bars according to claim 1, characterized in that, In step S3, the multi-fire rapid forging billet opening includes 3-5 fire forging cycles.

8. The method for preparing GH3128 alloy forged bars according to claim 1, characterized in that, In step S4, the deformation amount of the single-pass precision forging is 45%-50%.

9. A GH3128 alloy forged bar, characterized in that, The GH3128 alloy forged bar is prepared by the preparation method described in any one of claims 1-8.

10. The GH3128 alloy forged bar according to claim 9, characterized in that, At a test temperature of 950℃, the forged bar meets the following performance indicators: (a) High-temperature tensile elongation A ≥ 100%; (b) High-temperature tensile reduction of area Z ≥ 90%; (c) High-temperature creep elongation A ≥ 88%; (d) High-temperature sustained fracture time τ ≥ 40 hours; (e) High-temperature tensile strength R m ≥ 200 MPa.

Images