Nickel-based alloy grain boundary strengthening machining process based on multi-stage variable-speed forging

Abstract

The invention provides a nickel-based alloy grain boundary strengthening machining process based on multi-stage variable speed forging, and belongs to the technical field of nickel-based alloy machining.The nickel-based alloy grain boundary strengthening machining process comprises the steps that a nickel-based alloy raw material containing strengthening phase elements is selected according to a target application scene, and the nickel-based alloy raw material is converted into a forging blank through smelting and casting procedures; then, nickel-based alloys with different components are simulated, parameters of all stages of multi-stage variable-speed forging are preliminarily determined, and a correlation model between the alloy components and the technological parameters is constructed; then low-temperature and low-speed rough forging, medium-temperature and medium-speed precision forging and high-temperature and high-speed finish forging are carried out according to the model, so that the blank is gradually machined till the performance detection standard is met; and finally, the forged nickel-based alloy is subjected to heat treatment, and the nickel-based alloy is machined into the needed size and shape. According to the method, through the multi-stage variable speed control of the forging process and the synergistic effect of the follow-up treatment process, effective strengthening of the nickel-based alloy grain boundary is achieved, and the comprehensive performance of the nickel-based alloy is improved.

Description

Technical Field

[0001] The invention relates to the technical field of nickel-based alloy processing, and in particular to a nickel-based alloy grain boundary strengthening processing technology based on multi-stage variable speed forging. Background Art

[0002] In modern industry, nickel-based alloys are widely used in key fields such as aerospace, energy, and chemical industry due to their excellent high-temperature strength, corrosion resistance, and oxidation resistance. However, with the continuous development of industrial technology, the performance requirements for nickel-based alloys are becoming increasingly stringent. As one of the key factors affecting the performance of nickel-based alloys, the structure and characteristics of grain boundaries have an important influence on the strength, toughness, creep resistance and other properties of the alloy. Traditional processing technology has certain limitations in grain boundary strengthening. It is difficult to accurately control the microstructure and strengthening effect of grain boundaries, and it cannot meet the high performance requirements of nickel-based alloys in high-end application scenarios.

[0003] Therefore, it is of great practical significance to develop an efficient and precise nickel-based alloy grain boundary strengthening processing technology. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a nickel-based alloy grain boundary strengthening processing technology based on multi-stage variable speed forging, which achieves effective strengthening of the nickel-based alloy grain boundaries and improves the comprehensive performance of the nickel-based alloy through multi-stage variable speed control of the forging process and synergy with subsequent processing technology.

[0005] To achieve the above object, the present invention provides the following solutions: A nickel-based alloy grain boundary strengthening process based on multi-stage variable speed forging comprises the following steps: S1. According to the specific requirements of the target application scenario for the performance of the nickel-based alloy, select the nickel-based alloy raw materials containing strengthening phase elements, and convert the raw materials into forging billets through smelting and casting processes; S2. Based on the thermal simulation test machine, the nickel-based alloys with different compositions are simulated to preliminarily determine the parameters of each stage of multi-stage variable speed forging, and based on the forging data of nickel-based alloys with different compositions, the correlation model between alloy composition and process parameters is constructed; S3, based on the correlation model, determining the process parameters of multi-stage variable speed forging, and then performing low temperature and low speed rough forging at the first stage, medium temperature and medium speed fine forging at the second stage, and high temperature and high speed final forging at the third stage on the billet to obtain the forged nickel-based alloy; S4. Heat-treating the forged nickel-based alloy to improve the grain boundary strengthening effect of the nickel-based alloy, and processing the forged and heat-treated nickel-based alloy into a desired size and shape, and grinding and polishing to obtain a nickel-based alloy sample.

[0006] Preferably, in S1, the nickel-based alloy raw material containing strengthening phase elements is selected to include one or more of nickel, chromium, molybdenum, tungsten, aluminum, titanium, niobium and cobalt.

[0007] Preferably, in S1, the nickel-based alloy raw material containing strengthening phase elements is converted into a forged billet through a smelting and casting process, including: smelting the raw material at a smelting temperature of 1350-1450°C for a smelting time of 1.5-4h, and then casting at a casting temperature of 1320-1400°C to obtain a forged billet.

[0008] Preferably, in S2, based on a thermal simulation test machine, the nickel-based alloys with different compositions are simulated to preliminarily determine the parameters of each stage of the multi-stage variable speed forging, including: simulating the nickel-based alloys at different temperature ranges of 900-1300°C and strain rates of 0.01-10s by using a thermal simulation test machine. ~1 The thermal deformation behavior under the condition of high speed forging was studied, and the stress-strain curve was obtained. By analyzing the laws of grain growth and grain boundary evolution, the thermal simulation experimental data was obtained, and then the parameters of each stage of multi-stage variable speed forging were preliminarily determined.

[0009] Preferably, in S2, based on the forging data of nickel-based alloys with different compositions, a correlation model between alloy composition and process parameters is constructed, including: based on the obtained thermal simulation experimental data, obtaining nickel-based alloy data with different compositions and process parameters of multi-stage variable speed forging corresponding to nickel-based alloys with different compositions, constructing an alloy composition and process parameter database, and constructing a mathematical model reflecting the intrinsic relationship between alloy composition and process parameters through a machine learning algorithm.

[0010] Preferably, in S3, the first stage of low-temperature and low-speed rough forging includes: heating the blank to 950-1050°C by an induction heating furnace and keeping it warm for 1-3 hours, and then forging the blank on an electric screw press, controlling the forging speed to 0.005-0.018 mm / s and the deformation to 30%-45%, so as to initially achieve the crushing of coarse grains.

[0011] Preferably, in S3, the medium-temperature medium-speed precision forging in the second stage includes: reheating the billet after the first stage to 1050-1150°C, and adjusting the forging speed of the second stage to 0.02-0.04 mm / s and the deformation to 20%-35% according to the forging speed and deformation in the first stage, so as to promote the migration and reorganization of grain boundaries, further refine the grains, form fine and evenly distributed grain boundaries, and make the γ' phase or γ'' phase precipitate evenly near the grain boundaries.

[0012] Preferably, in S3, the third stage of high-temperature and high-speed final forging includes: heating the billet after the second stage to the solidus temperature of the alloy of 1170~1270°C, and performing final forging at a forging speed of 0.05~0.09mm / s to eliminate the internal stress generated in the first two stages of billet forging and further strengthen the grain boundaries.

[0013] Preferably, in S3, the nickel-based alloy is tested in sequence for microstructure, hardness and mechanical properties, wherein the average grain size of the microstructure is less than 60 μm, the grain boundaries are continuous and there is no obvious impurity segregation; the Brinell hardness is 200~270 HB, the yield strength is greater than 450 MPa, and the elongation is not less than 16%.

[0014] Preferably, in S4, the heat treatment of the nickel-based alloy after forging includes solution treatment and aging treatment. The process of the solution treatment is: heating the nickel-based alloy after multi-stage variable speed forging to 1180~1220℃, keeping it warm for 2~4h, so that the alloy elements are fully dissolved in the alloy matrix, and the alloy components are homogenized to eliminate the microsegregation generated during the forging process; the process of the aging treatment is: placing the nickel-based alloy after the solution treatment in an environment of 700~750℃, keeping it warm for 8~12h, so as to promote the precipitation of fine dispersed strengthening phases in the nickel-based alloy, thereby strengthening the grain boundaries and the nickel-based alloy matrix.

[0015] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: (1) The present invention simulates nickel-based alloys with different compositions by using a thermal simulation test machine, obtains thermal simulation experimental data, and constructs a correlation model between alloy composition and process parameters. This process achieves accurate matching of alloy composition with multi-stage variable speed forging process parameters. Compared with the prior art, it no longer relies on empirical broad parameter settings, but is based on scientific simulation and data analysis to tailor the most suitable forging parameters for each specific nickel-based alloy, thereby significantly improving the pertinence and effectiveness of the forging process and improving the stability and consistency of product quality.

[0016] (2) The multi-stage variable speed forging process of the present invention includes low-temperature and low-speed rough forging, medium-temperature and medium-speed fine forging, and high-temperature and high-speed final forging. Through the step-by-step forging process, the effective crushing of coarse grains, the migration and reorganization of grain boundaries, and the uniform precipitation of γ' phase or γ'' phase near the grain boundaries are achieved. Finally, after heat treatment, fine and uniformly distributed grain boundaries are obtained, which greatly strengthens the grain boundaries. Compared with the existing technology, the grain boundary strengthening effect is more significant, thereby greatly improving the comprehensive properties of nickel-based alloys, such as strength, toughness, fatigue resistance, etc., and broadening the application range of nickel-based alloys in aerospace, energy and other fields.

[0017] (3) The present invention sequentially tests the microstructure, hardness and mechanical properties of nickel-based alloys, and can timely discover problems that may occur during the forging process, such as grain size that does not meet the requirements, uneven hardness, excessive internal stress, etc., and then adjust the forging process parameters to avoid investing more costs in subsequent processes. At the same time, it ensures the quality of the final product, reduces the scrap rate, and improves production efficiency and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 The present invention is a flow chart of a nickel-based alloy grain boundary strengthening processing technology based on multi-stage variable speed forging. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown, the present invention provides a nickel-based alloy grain boundary strengthening processing technology based on multi-stage variable speed forging, comprising the following steps: S1. According to the specific requirements of the target application scenario for the performance of the nickel-based alloy, select the nickel-based alloy raw materials containing strengthening phase elements, and convert the raw materials into forging billets through smelting and casting processes; S2. Based on the thermal simulation test machine, the nickel-based alloys with different compositions are simulated to preliminarily determine the parameters of each stage of multi-stage variable speed forging, and based on the forging data of nickel-based alloys with different compositions, the correlation model between alloy composition and process parameters is constructed; S3, based on the correlation model, determining the process parameters of multi-stage variable speed forging, and then performing low temperature and low speed rough forging at the first stage, medium temperature and medium speed fine forging at the second stage, and high temperature and high speed final forging at the third stage on the billet to obtain the forged nickel-based alloy; S4. The forged nickel-based alloy is heat-treated to improve the grain boundary strengthening effect of the nickel-based alloy, and the forged and heat-treated nickel-based alloy is processed into a desired size and shape, and then ground and polished to obtain a nickel-based alloy sample.

[0023] Specifically, in S1, the nickel-based alloy raw material containing strengthening phase elements includes one or more of nickel, chromium, molybdenum, tungsten, aluminum, titanium, niobium and cobalt. The nickel-based alloy raw material containing strengthening phase elements is converted into a forged billet through a smelting and casting process, including: smelting the raw material at a smelting temperature of 1350-1450° C. for a smelting time of 1.5-4 hours, and then casting at a casting temperature of 1320-1400° C. to obtain a forged billet.

[0024] In S2, based on the thermal simulation test machine, the nickel-based alloys with different compositions are simulated, and the parameters of each stage of multi-stage variable speed forging are preliminarily determined, including: through the thermal simulation test machine, the thermal deformation behavior of the nickel-based alloy in different temperature ranges of 900~1300℃ and strain rates of 0.01~10s~1 is simulated, and the stress-strain curve is obtained. By analyzing the laws of grain growth and grain boundary evolution, the thermal simulation experimental data is obtained, and then the parameters of each stage of multi-stage variable speed forging are preliminarily determined. Based on the forging data of nickel-based alloys with different compositions, a correlation model between alloy composition and process parameters is constructed, including: based on the obtained thermal simulation experimental data, the nickel-based alloy data of different compositions and the process parameters of multi-stage variable speed forging corresponding to nickel-based alloys with different compositions are obtained, and a database of alloy composition and process parameters is constructed, and a mathematical model reflecting the intrinsic relationship between alloy composition and process parameters is constructed through machine learning algorithms. Specifically including: Data are collected from a large number of nickel-based alloy forging experiments and actual production cases, including combinations of nickel-based alloy elements with different compositions, including the mass fractions of the main alloying elements of nickel-based alloys (nickel Ni, chromium Cr, molybdenum Mo, tungsten W, aluminum Al, titanium Ti, niobium Nb, cobalt Co, etc.), accurate to 0.01%; also including trace elements (such as boron B, zirconium Zr, hafnium Hf, etc.) and their contents, as well as the type of alloy (such as solid solution strengthening type, aging strengthening type, etc.). And record the multi-stage variable speed forging process parameters corresponding to each sample, such as the temperature, forging speed, and holding time of each stage; as well as the performance indicators of the final product, such as grain size, hardness, tensile strength, etc. Specifically: In S3, the first stage of low-temperature and low-speed rough forging includes: heating the billet to 950~1050℃ in an induction heating furnace and keeping it warm for 1~3h, and then forging the billet on an electric screw press, controlling the forging speed to 0.005~0.018mm / s and the deformation to 30%~45%, thereby initially achieving the crushing of coarse grains. The second stage of medium-temperature medium-speed precision forging includes: reheating the billet after the first stage to 1050~1150℃, adjusting the forging speed of the second stage to 0.02~0.04mm / s and the deformation to 20%~35% according to the forging speed and deformation of the first stage, so as to promote the migration and reorganization of grain boundaries, further refine the grains, form fine and evenly distributed grain boundaries, and make the γ' phase or γ'' phase precipitate evenly near the grain boundaries. The third stage of high-temperature and high-speed final forging includes: heating the billet after the second stage to the solidus temperature of the alloy of 1170~1270℃, and performing the final forging at a forging speed of 0.05~0.09mm / s to eliminate the internal stress generated in the first two stages of billet forging and further strengthen the grain boundaries. S3 also includes testing the microstructure, hardness and mechanical properties of nickel-based alloys in sequence, where the average grain size of the microstructure is less than 60μm, the grain boundaries are continuous and there is no obvious impurity segregation; the Brinell hardness is 200~270HB, the yield strength is greater than 450MPa, and the elongation is not less than 16%.

[0025] Based on MySQL or PostgreSQL relational database, build alloy composition and process parameter database, then use machine learning algorithm to build the correlation model between alloy composition and process parameters, and finally use the collected data to train the selected algorithm, and divide the original data into 70% training set, 15% validation set and 15% test set. During the training process, adjust the parameters of the model to minimize the error of the model on the validation set, and use mean square error and mean absolute error to evaluate the performance of the model. Finally, use the test set to verify the trained model to ensure that the model has good generalization ability. Specifically: The collected original data sample set is recorded as D， ,in Nis the number of samples in the original data sample set, is the alloy composition data, is the corresponding process parameter data; and is divided into training sets D train , validation set D val and test set D test ; Among them, the training set D train Sample size n train =0.7 N ; Validation set D val Sample size n val =0.15 N ; Test set D test Sample size n test =0.15 N ; Then, a machine learning algorithm is used to build an association model. Let the model function be , where x is the input alloy composition feature vector, is the parameter set of the model; the model's prediction value for the sample is During the training process, constantly adjust To optimize model performance.

[0026] The mean square error and mean absolute error are used to evaluate the performance of the model. The mean square error of the training set is: ; During the training phase, the model parameters are adjusted through the optimization algorithm , the goal is to make Keep decreasing, so that the predicted value of the model on the training set is closer to the true value.

[0027] Validation set mean square error: ; During the training process, the validation set mean square error is calculated regularly to monitor the generalization ability of the model. When it no longer decreases, stop training to avoid overfitting.

[0028] Test set mean square error: ; After training, the model performance is evaluated using the test set. It reflects the prediction accuracy of the model on unknown data.

[0029] Mean absolute error of the training set: ; and Similarly, its value is expected to decrease during training.

[0030] The mean absolute error of the validation set is: ; Used to assist in evaluating the performance of the model on the validation set.

[0031] The mean absolute error of the test set is: ; and Jointly evaluate the performance of the model on the test set.

[0032] Comprehensively consider the training set, validation set and test set MSE and MAE The model performance can be evaluated by calculating the comprehensive evaluation index S : ; in, and is the weight coefficient, and .like and , then there is overfitting; if , Both are large and , is also large, there is underfitting. Ideally, and Should , Close to the surface, the model has good generalization ability.

[0033] If the model performs as expected on the test set, it can be applied to the prediction of process parameters of new alloy compositions. When encountering new nickel-based alloy materials, its composition data is input into the associated model, and the corresponding initial prediction values ​​of the multi-stage variable speed forging process parameters are output. The initial prediction values ​​are then adjusted based on actual experience and production conditions to determine the final process parameters.

[0034] In S4, the nickel-based alloy after forging is subjected to heat treatment including solution treatment and aging treatment. The process of the solution treatment is as follows: heating the nickel-based alloy after multi-stage variable speed forging to 1180-1220°C and keeping it warm for 2-4 hours to fully dissolve the alloy elements in the alloy matrix and homogenize the alloy components to eliminate the microsegregation generated during the forging process; the process of the aging treatment is as follows: placing the nickel-based alloy after the solution treatment in an environment of 700-750°C and keeping it warm for 8-12 hours to promote the precipitation of fine dispersed strengthening phases in the nickel-based alloy, thereby strengthening the grain boundaries and the nickel-based alloy matrix.

[0035] The present invention will be further verified by using three nickel-based alloys, Inconel 718, Inconel 625 and Hastelloy X.

[0036] Example 1 In this embodiment, Inconel 718 is selected for processing, which specifically includes the following steps: Raw material selection and billet preparation: According to the high-temperature strength and oxidation resistance of nickel-based alloys required by high-temperature parts of aircraft engines, Inconel 718 nickel-based alloy raw materials containing strengthening phase elements such as nickel, chromium, molybdenum, niobium, and titanium are selected; the raw materials are placed in a vacuum induction melting furnace and smelted at a melting temperature of 1420°C for 3 hours. Subsequently, the smelted alloy liquid is cast into a specific mold using a centrifugal casting process at a casting temperature of 1370°C to obtain a forged billet.

[0037] Simulation and correlation model construction: Using the Gleeble thermal simulation test machine, Inconel 718 alloy samples were subjected to temperature range of 950-1250℃ and strain rate of 0.01-5s. ~1 Thermal deformation simulation was performed under 30°C. The thermal simulation experimental data were obtained by analyzing the stress-strain curve, grain growth and grain boundary evolution. Based on the experimental data obtained, the composition data and corresponding forging process parameters of different batches of Inconel 718 alloy during the forging process were collected to build a database of alloy composition and process parameters. The BP neural network algorithm was used to construct a mathematical model that reflects the intrinsic relationship between alloy composition and process parameters.

[0038] Multi-stage variable speed forging and testing: (1) The first stage of low-temperature and low-speed rough forging: The billet is heated to 1000°C by an induction heating furnace and kept warm for 2 hours. Then, the billet is forged on an electric screw press at a forging speed of 0.01 mm / s and a deformation of 40%, and the coarse grains are initially crushed. At this time, the average grain size is reduced from the initial 100 μm to 70 μm, the crystal interface area fraction is increased from 10% to 15%, and the Brinell hardness reaches 180 HB.

[0039] (2) Second stage medium temperature and medium speed precision forging: The billet after the first stage is reheated to 1100℃. According to the forging conditions in the first stage, the forging speed in the second stage is adjusted to 0.03mm / s and the deformation is 30%, which promotes the migration and reorganization of grain boundaries, further refines the grains, and makes the γ' phase or γ'' phase precipitate uniformly near the grain boundaries. After this stage, the average grain size is further reduced to 50μm, the crystal interface area fraction is increased to 22%, and the Brinell hardness is increased to 210HB.

[0040] (3) The third stage of high-temperature and high-speed final forging: The billet after the second stage is heated to 1230°C and the final forging is carried out at a forging speed of 0.07 mm / s to eliminate the internal stress generated in the first two stages of billet forging and further strengthen the grain boundaries. After forging, the average grain size is stable at 45 μm, the crystal interface volume fraction reaches 28%, and the Brinell hardness is 230 HB. In addition, the microstructure test results show that the grain boundaries are continuous and there is no obvious impurity segregation; the yield strength is 500 MPa, the elongation is 20%, and all indicators meet the expected standards.

[0041] Heat treatment and finished product processing: (1) Solution treatment: The Inconel 718 nickel-based alloy after multi-stage variable speed forging is heated to 1200°C and kept warm for 3 hours to fully dissolve the alloy elements in the alloy matrix, homogenize the alloy composition, and eliminate the microsegregation generated during the forging process.

[0042] (2) Aging treatment: The nickel-based alloy after solution treatment is placed in a 720℃ environment for 10 hours to promote the precipitation of fine dispersed strengthening phases in the nickel-based alloy, thereby strengthening the grain boundaries and the nickel-based alloy matrix. After this treatment, the Brinell hardness is further increased to 250HB. Finally, the forged and heat-treated Inconel 718 nickel-based alloy is processed into the size and shape required for high-temperature components of aircraft engines, and after grinding and polishing, a nickel-based alloy sample that meets the requirements is obtained.

[0043] Example 2 In this embodiment, Inconel 625 is selected for processing, which specifically includes the following steps: Raw material selection and billet preparation: In view of the corrosion resistance and strength requirements of nickel-based alloys for offshore oil production equipment, Inconel 625 nickel-based alloy raw materials containing strengthening elements such as nickel, chromium, molybdenum, and niobium are selected. The raw materials are melted at a melting temperature of 1400°C for 2.5 hours, and then the alloy liquid is cast into a forging billet using a sand casting method at a casting temperature of 1350°C.

[0044] Simulation and correlation model construction: Using DIL805A thermal simulation test machine, Inconel 625 alloy was tested in the temperature range of 900~1300℃ and 0.01~10s ~1 Thermal deformation simulation is performed at a strain rate to obtain stress-strain curves and related thermal simulation experimental data. Based on the data, a database of alloy composition and process parameters is constructed, and a support vector machine algorithm is used to construct a correlation model between alloy composition and process parameters.

[0045] Multi-stage variable speed forging and testing: (1) The first stage of low-temperature and low-speed rough forging: The billet is heated to 980°C in an induction heating furnace, kept warm for 1.5 hours, and then forged on an electric screw press at a forging speed of 0.008 mm / s and a deformation of 35% to initially break up the coarse grains. At this time, the average grain size is reduced from the initial 110 μm to 80 μm, the crystal interface area fraction is increased from 8% to 13%, and the Brinell hardness is 170 HB.

[0046] (2) Second stage medium temperature and medium speed precision forging: reheat the billet after the first stage forging to 1080℃, adjust the forging speed to 0.025mm / s and the deformation to 25%, promote grain boundary migration and reorganization, refine the grains, and make the γ' phase or γ'' phase precipitate uniformly near the grain boundary. After this stage, the average grain size is reduced to 55μm, the crystal interface area fraction is increased to 20%, and the Brinell hardness reaches 220HB.

[0047] (3) The third stage of high-temperature and high-speed final forging: The billet is heated to 1220°C and the final forging is performed at a forging speed of 0.06 mm / s to eliminate internal stress and strengthen the grain boundaries. After forging, the average grain size is 50 μm, the grain interface volume fraction is 25%, and the Brinell hardness is 240 HB. At the same time, the microstructure shows that the grain boundary is in good condition; the yield strength is 490 MPa, and the elongation is 18%, which meets the performance requirements.

[0048] Heat treatment and finished product processing: (1) Solution treatment: Heat the forged Inconel 625 alloy to 1190 °C and keep it for 2.5 h to achieve uniform dissolution of alloy elements and homogenization of composition.

[0049] (2) Aging treatment: Keep the temperature at 730℃ for 9 hours to promote the precipitation of strengthening phases and strengthen the grain boundaries and matrix. After heat treatment, the Brinell hardness is increased to 260HB. Finally, the forged and heat-treated Inconel 625 nickel-based alloy is processed into the size and shape of parts required for offshore oil production equipment, and qualified nickel-based alloy samples are obtained after grinding and polishing.

[0050] Example 3 In this embodiment, Hastelloy X is selected for processing, which specifically includes the following steps: Raw material selection and billet preparation: Considering the high temperature strength and thermal fatigue resistance of nickel-based alloys required by the gas turbine combustion chamber, Hastelloy X nickel-based alloy raw materials containing strengthening phase elements such as nickel, chromium, molybdenum, tungsten, and cobalt are selected. The raw materials are melted at a melting temperature of 1430°C for 3.5 hours, and then the forging billet is obtained by metal mold casting at a casting temperature of 1360°C.

[0051] Simulation and correlation model construction: Using the Formastor~F thermal simulation test machine, Hastelloy X alloy was tested in the temperature range of 950~1300℃ and 0.01~8s ~1 Thermal deformation simulation was performed at the strain rate to obtain thermal simulation experimental data. A database of alloy composition and process parameters was constructed, and a correlation model was constructed using the random forest algorithm.

[0052] Multi-stage variable speed forging and testing: (1) The first stage of low-temperature and low-speed rough forging: The billet is heated to 1020°C and kept warm for 2.5 hours, and then forged on an electric screw press at a forging speed of 0.012 mm / s and a deformation of 42% to initially break the grains. At this time, the average grain size changes from 120 μm to 85 μm, the intergranular interface volume fraction increases from 9% to 14%, and the Brinell hardness reaches 185 HB.

[0053] (2) The second stage of medium temperature and medium speed precision forging: the billet is reheated to 1120℃, the forging speed is adjusted to 0.035mm / s, and the deformation is 32% to promote grain boundary migration and reorganization, refine the grains, and make the γ' phase or γ'' phase precipitate uniformly near the grain boundary. After this stage, the average grain size is reduced to 52μm, the intergranular interface area fraction is increased to 23%, and the Brinell hardness is 225HB.

[0054] (3) The third stage of high-temperature and high-speed final forging: The billet is heated to 1240°C and the final forging is performed at a forging speed of 0.08 mm / s to eliminate internal stress and strengthen the grain boundary. After forging, the average grain size of the microstructure is 48 μm, the grain boundary is continuous and free of impurities, the crystal interface volume fraction reaches 27%, and the Brinell hardness is 250 HB. The yield strength is 470 MPa and the elongation is 17%, which meets the performance test standards.

[0055] Heat treatment and finished product processing: (1) Solution treatment: Heat the Hastelloy X alloy to 1210°C and keep it at this temperature for 3.5 hours to allow the alloy elements to dissolve evenly and the composition to become homogenous.

[0056] (2) Aging treatment: Keep the temperature at 740℃ for 11h to promote the precipitation of strengthening phases and strengthen the grain boundaries and matrix. After heat treatment, the Brinell hardness is further increased to 270HB. Finally, the forged and heat-treated Hastelloy X nickel-based alloy is processed into the size and shape required for the gas turbine combustion chamber, and after grinding and polishing, a nickel-based alloy sample that meets the requirements is obtained.

[0057] Therefore, by adopting the above-mentioned nickel-based alloy grain boundary strengthening processing technology based on multi-stage variable speed forging, the multi-stage variable speed control of the forging process and the synergy with the subsequent processing technology are achieved to effectively strengthen the nickel-based alloy grain boundaries and improve the comprehensive performance of the nickel-based alloy.

[0058] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0059] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A nickel-based alloy grain boundary strengthening process based on multi-stage variable speed forging, characterized in that: The following steps are involved: S1. According to the requirements of the target application scenario for the performance of the nickel-based alloy, select the nickel-based alloy raw materials containing strengthening phase elements, and convert the raw materials into forging billets through smelting and casting processes; S2. Based on the thermal simulation test machine, the nickel-based alloys with different compositions are simulated to preliminarily determine the parameters of each stage of multi-stage variable speed forging, and based on the forging data of nickel-based alloys with different compositions, the correlation model between alloy composition and process parameters is constructed; S3, based on the correlation model, determining the process parameters of multi-stage variable speed forging, and then performing low temperature and low speed rough forging at the first stage, medium temperature and medium speed fine forging at the second stage, and high temperature and high speed final forging at the third stage on the billet, until the forged nickel-based alloy meets the performance test standard; In S3, the first stage of low-temperature and low-speed rough forging includes: heating the billet to 950~1050℃ through an induction heating furnace and keeping it warm for 1~3h, then forging the billet on an electric screw press, controlling the forging speed to 0.005~0.018mm / s and the deformation to 30%~45%, and preliminarily achieving the crushing of coarse grains; the second stage of medium-temperature and medium-speed fine forging includes: reheating the billet after the first stage to 1050~1150℃, adjusting the second stage according to the forging speed and deformation of the first stage The forging speed is 0.02-0.04 mm / s and the deformation is 20%-35%, which promotes the migration and reorganization of grain boundaries, further refines the grains, forms fine and evenly distributed grain boundaries, and makes the γ' phase or γ'' phase precipitate evenly near the grain boundaries; the third stage of high-temperature and high-speed final forging includes: heating the billet after the second stage to the solidus temperature of the alloy of 1170-1270°C, and performing the final forging at a forging speed of 0.05-0.09 mm / s to eliminate the internal stress generated in the first two stages of billet forging and further strengthen the grain boundaries; S4. Heat-treating the forged nickel-based alloy to improve the grain boundary strengthening effect of the nickel-based alloy, and processing the forged and heat-treated nickel-based alloy into a desired size and shape, and grinding and polishing to obtain a nickel-based alloy sample.

2. The nickel-based alloy grain boundary strengthening process based on multi-stage variable speed forging according to claim 1 is characterized in that: In S1, the strengthening phase elements of the nickel-based alloy raw material include one or more of nickel, chromium, molybdenum, tungsten, aluminum, titanium, niobium and cobalt.

3. The nickel-based alloy grain boundary strengthening process based on multi-stage variable speed forging according to claim 2 is characterized in that: In S1, the nickel-based alloy raw material containing strengthening phase elements is converted into a forged billet through a smelting and casting process, including: smelting the raw material at a smelting temperature of 1350-1450°C for a smelting time of 1.5-4h, and then casting at a casting temperature of 1320-1400°C to obtain a forged billet.

4. The nickel-based alloy grain boundary strengthening process based on multi-stage variable speed forging according to claim 1 is characterized in that: In S2, based on the thermal simulation test machine, the nickel-based alloys with different compositions were simulated, and the parameters of each stage of multi-stage variable speed forging were preliminarily determined, including: the thermal simulation test machine was used to simulate the nickel-based alloys in different temperature ranges of 900~1300℃ and strain rates of 0.01~10s ~1 The thermal deformation behavior under the condition of high speed forging was studied, and the stress-strain curve was obtained. By analyzing the laws of grain growth and grain boundary evolution, the thermal simulation experimental data was obtained, and then the parameters of each stage of multi-stage variable speed forging were preliminarily determined.

5. The nickel-based alloy grain boundary strengthening process based on multi-stage variable speed forging according to claim 4 is characterized in that: In S2, based on the forging data of nickel-based alloys with different compositions, a correlation model between alloy composition and process parameters is constructed, including: based on the obtained thermal simulation experimental data, obtaining nickel-based alloy data with different compositions and process parameters of multi-stage variable speed forging corresponding to nickel-based alloys with different compositions, constructing an alloy composition and process parameter database, and constructing a mathematical model reflecting the intrinsic relationship between alloy composition and process parameters through a machine learning algorithm.

6. The nickel-based alloy grain boundary strengthening process based on multi-stage variable speed forging according to claim 1 is characterized in that: In S3, the microstructure, hardness and mechanical properties of the nickel-based alloy were tested in turn, wherein the average grain size of the microstructure was less than 60 μm, the grain boundaries were continuous and there was no obvious impurity segregation; the Brinell hardness was 200~270 HB, the yield strength was greater than 450 MPa, and the elongation was not less than 16%.

7. The nickel-based alloy grain boundary strengthening process based on multi-stage variable speed forging according to claim 1 is characterized in that: In S4, the nickel-based alloy after forging is subjected to heat treatment including solution treatment and aging treatment. The process of the solution treatment is as follows: heating the nickel-based alloy after multi-stage variable speed forging to 1180-1220°C and keeping it warm for 2-4 hours to fully dissolve the alloy elements in the alloy matrix and homogenize the alloy components to eliminate the microsegregation generated during the forging process; the process of the aging treatment is as follows: placing the nickel-based alloy after the solution treatment in an environment of 700-750°C and keeping it warm for 8-12 hours to promote the precipitation of fine dispersed strengthening phases in the nickel-based alloy, thereby strengthening the grain boundaries and the nickel-based alloy matrix.

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