Method for regulating and controlling microstructure and fatigue performance of nickel-based superalloy prepared by LPBF

Abstract

A method for regulating and controlling the microstructure and fatigue performance of nickel-based superalloy prepared through LPBF comprises the following steps that S1, nickel-based superalloy powder and doped powder are mixed and evenly dispersed through ball milling; s2, the product is put into a forming cavity of LPBF printing equipment, a product model is imported into the LPBF printing equipment, a product is printed layer by layer through an LPBF technology, and an interlayer in-situ tempering technology is adopted after printing of each layer is completed; s3, argon is filled before printing; s4, performing crystal orientation deviation control and preheating treatment on the substrate by adopting a single crystal seed layer presetting technology; s5, printing is carried out; and S6, after printing is completed, double-aging heat treatment is conducted. According to the method for regulating and controlling the microstructure and the fatigue performance of the nickel-based superalloy prepared through the LPBF, precipitated phase distribution, grain orientation and defect suppression are synergistically optimized, a fatigue fracture is in a dimple shape, the fatigue life of a product is remarkably prolonged, the reliability of the product is remarkably improved, and the method can be used for manufacturing turbine blades of aero-engines.

Description

Technical Field

[0001] The present invention belongs to the field of metal additive manufacturing, and particularly relates to a method for regulating the microstructure and fatigue performance of nickel-based superalloys prepared by LPBF. Background Art

[0002] As the core material of aero-engine turbine blades, the fatigue performance of nickel-based superalloys directly determines the service safety and life reliability of turbine blades under extreme alternating loads. There are many deficiencies in traditional preparation processes. For example, the microvoids generated during casting will become the preferred locations for the initiation of fatigue cracks, reducing the crack initiation resistance of the alloy; the coarsely and unevenly precipitated γ' phase is not only difficult to play a strengthening role, but is also likely to become a crack source, accelerating the initiation and propagation of fatigue cracks. In addition, the random grain boundary distribution is prone to form stress concentration, promoting the initiation and propagation of fatigue cracks along the grain boundaries and reducing the fatigue strength of the alloy. At the same time, the residual stress gradient and dislocation tangles caused by thermomechanical processing will lead to differences in tensile and compressive stresses in different regions inside the alloy, further exacerbating the anisotropy of fatigue performance, making the deformation coordination of the alloy under alternating loads poor, local stress and strain concentration, and accelerating the accumulation of fatigue damage. These factors together lead to the uncertainty of the fatigue performance of the alloy, seriously restricting the reliability boundary of turbine blade design.

[0003] The laser powder bed fusion (LPBF) technology provides a new way for the microstructure reconstruction and fatigue performance optimization of nickel-based superalloys. LPBF can achieve high-precision forming of complex shapes by melting powders layer by layer with a high-energy density laser. Its rapid cooling and solidification characteristics significantly refine the alloy microstructure, improve the density, optimize the γ' phase distribution, and eliminate the microshrinkage and γ / γ' eutectic defects in traditional processes, making the material microstructure more uniform and significantly reducing the anisotropy of performance, thereby improving the fatigue life and reliability.

[0004] However, this technology also faces many challenges in the application process. The high alloy content of nickel-based superalloys gives them a wide solidification temperature range. Coupled with the characteristics of rapid laser solidification and melt pool phase transformation, it is easy to cause increased element segregation and crack sensitivity. Secondly, the residual stress generated during the LPBF process and the phase transformation shrinkage stress are superimposed on each other, easily inducing cracks in regions such as grain boundaries, seriously affecting the formability and mechanical properties of the alloy. At the same time, the microdefects (such as lack of fusion, pores) caused by the complex thermomechanical coupling field during the LPBF preparation process, the stress concentration at the interfaces of heterogeneous precipitates, and the dislocation evolution behavior under cyclic loads are still the bottlenecks restricting the leapfrog improvement of fatigue performance.

[0005] Therefore, how to effectively suppress the generation of cracks, control the formation of microdefects, and optimize the microstructure is the key to the further development of the LPBF technology in the field of nickel-based superalloy turbine blade preparation.

[0006] In summary, traditional nickel-based superalloy preparation methods have numerous limitations. LPBF technology offers a novel approach for microstructural reconstruction and fatigue performance optimization in nickel-based superalloys. However, how to leverage the advantages of LPBF technology to precisely control the alloy's precipitation phase and fatigue performance remains an urgent challenge in materials science.

[0007] Therefore, the present invention aims to provide a method for regulating the precipitation phase and fatigue properties of nickel-based high-temperature alloys prepared by LPBF, so as to overcome the shortcomings of the existing technology and improve the comprehensive performance and application value of nickel-based high-temperature alloys. Summary of the Invention

[0008] Purpose of the Invention: To overcome the above-mentioned deficiencies, the present invention aims to provide a method for regulating the microstructure and fatigue properties of nickel-based superalloys prepared by LPBF. By optimizing the existing LPBF process for forming nickel-based superalloys, the present invention can precisely control the precipitation phase and fatigue properties of nickel-based superalloys, thereby improving the overall performance and application value of nickel-based superalloys.

[0009] The purpose of the present invention is achieved through the following technical solutions: A method for regulating the microstructure and fatigue properties of a nickel-based high-temperature alloy prepared by LPBF, comprising the following steps: S1: placing nickel-based high-temperature alloy powder and doping powder in a ball mill and fully mixing them to obtain a mixed powder; S2: placing the mixed powder into a forming chamber of an LPBF printing device, importing a product model into the LPBF printing device, printing the product layer by layer using an LPBF process, and performing an interlayer in-situ tempering process after each layer is printed, planning a printing path and an interlayer in-situ tempering path; S3: Before printing, fill with argon gas and ensure that the oxygen content in the atmosphere of the forming chamber is reduced to <15 ppm; S4: Using single crystal seed layer pre-deposition technology, the substrate of the LPBF printing equipment is controlled for crystal orientation deviation and preheated; S5: Click the forming button of the LPBF printing device until the product is printed; S6: Take out the formed product from the forming chamber and separate the product from the substrate by cutting.

[0010] The present invention's method for regulating the microstructure and fatigue properties of nickel-based high-temperature alloys prepared by LPBF is rationally designed. It combines powder doping, in-situ thermomechanical coupling field regulation of precipitate distribution, and directional construction of fatigue performance microstructures to synergistically optimize precipitate distribution, grain orientation, and defect suppression, significantly improving the fatigue life and reliability of the product.

[0011] Specifically, the powders are mixed by a ball mill to uniformly disperse the doped powders in the nickel-based superalloy powders, providing a good foundation for subsequent forming. The in-situ tempering process between layers helps optimize the distribution of the precipitated phases. Planning the printing path and the in-situ tempering path between layers ensures the orderly progress of the forming process. Controlling the oxygen content in the forming chamber can reduce oxidation defects. Adjusting the substrate temperature and pre-setting the single crystal seed layer helps control the microstructure and orientation of the alloy and improve the fatigue performance.

[0012] Furthermore, in the method for regulating the microstructure and fatigue performance of nickel-based superalloys prepared by LPBF as described above, in S1, the powders are nickel-based superalloy powders with gas atomization grades of GH4169, GH4378, and GH4033; the doped powder is rare earth silicate Yb2SiO5 and the doping amount is 0.4 - 0.8 wt% of the nickel-based superalloy powders.

[0013] By doping nano-Yb2SiO5 powders as nucleation cores, the average size of the γ' phase is refined to reach 14 nm. Combining with the means of in-situ tempering between layers, the uniform precipitation of the γ' phase is promoted during the printing process, and the single crystal seed layer pre-setting technology is used to achieve the epitaxial growth of grains along the principal stress axis, reducing the sensitivity of grain boundary cracks.

[0014] Furthermore, in the method for regulating the microstructure and fatigue performance of nickel-based superalloys prepared by LPBF as described above, in S1, the nickel-based superalloy powders are controlled to have a powder particle size of 15 - 53 μm, a fluidity of Hall flow rate ≤ 25 s / 50 g, and an oxygen content ≤ 200 ppm through argon cycle drying and mechanical screening; the powder particle size of the doped powder is 50 - 200 nm.

[0015] The characteristics of the powders will directly affect the subsequent forming process and the performance of the final product. Defining reasonable powder particle size, powder fluidity, and low oxygen content helps improve the forming quality.

[0016] Furthermore, in the method for regulating the microstructure and fatigue performance of nickel-based superalloys prepared by LPBF as described above, in S1, the ball mill is a planetary ball mill.

[0017] In S2, the mixed powder is placed into the forming chamber of the LPBF printing device, and a leveling operation is performed on the substrate, scraper, and mixed powder of the LPBF printing device through a tool; the imported product model is sliced. Performing a leveling operation on the substrate, scraper, and mixed powder can ensure that the thickness of the powder layer is uniform during the printing process, avoiding problems such as unstable molten pools and forming defects caused by uneven powder layer thickness. The imported product model is sliced using software to convert the three-dimensional model into two-dimensional slice data, which guides the LPBF printing device to print the product layer by layer, ensuring the printing accuracy and precision, and enabling the precise manufacturing of products such as turbine blades with complex shapes.

[0018] Further, in the above method for regulating the microstructure and fatigue performance of nickel-based superalloy prepared by LPBF, the product in S2 is a turbine blade.

[0019] The method of the present invention is designed and optimized for the manufacturing of turbine blades. The turbine blades prepared by the method of the present invention can meet the usage requirements under complex working conditions such as high temperature, high pressure, and high-speed rotation, improving the reliability and performance of aeroengines. In particular, the present invention significantly improves the fatigue performance of the material by regulating the distribution of precipitation phases, grain orientation, and other microstructure characteristics. The optimization of these microstructures is adapted to the working characteristics of turbine blades, effectively reducing the risk of fatigue crack initiation and propagation during the service of turbine blades, extending their service life, and reducing maintenance and replacement costs.

[0020] Further, in the above method for regulating the microstructure and fatigue performance of nickel-based superalloy prepared by LPBF, the process parameters of the LPBF printing device are set as follows: the laser power during the LPBF process printing is 300 - 400 W, the scanning speed is 650 - 800 mm / s, the scanning spacing is 0.1 - 0.3 mm, the powder spreading layer thickness is 40 - 60 μm, and the scanning direction rotates 67° per layer.

[0021] Preferably, the process parameters of the LPBF printing device are set as follows: the laser power during the LPBF process printing is 360 W, the scanning speed is 700 mm / s, the scanning spacing is 0.1 mm, the powder spreading layer thickness is 60 μm, and the scanning direction rotates 67° per layer.

[0022] The process parameters synergistically optimize the molten pool morphology, solidification behavior, and microstructure formation during the LPBF printing process. In particular, setting the scanning direction to rotate 67° per layer can effectively change the grain growth direction, avoiding the formation of coarse columnar grains with grains growing along a single direction, thereby refining the grains, improving the isotropy and fatigue performance of the material. At the same time, this rotational scanning method can also reduce the concentration of residual stress, reducing the possibility of crack initiation and propagation caused by residual stress.

[0023] Furthermore, in the above method for regulating the microstructure and fatigue properties of nickel-based superalloys prepared by LPBF, the process parameters of the LPBF printing equipment are set as follows: the laser power during the in-situ interlayer tempering process is 110 - 150 W, the scanning speed is 1200 - 1500 mm / s, non-melting scanning is performed on the formed layer, and the interlayer cooling rate is controlled to be 10 - 50 °C / s; the number of tempering times in the in-situ interlayer tempering process is 1 - 3 times per layer, the precipitation size of the γ' phase in the product is ≤50 nm, and the volume fraction is 40 - 60%.

[0024] In-situ interlayer tempering uses low-power laser for non-melting scanning. Utilizing the thermal accumulation effect, without melting the formed layer, it promotes the in-situ aging precipitation of the γ' phase. Controlling the interlayer cooling rate to be 10 - 50 °C / s can further adjust the precipitation kinetics of the γ' phase, enabling the γ' phase to precipitate uniformly and finely. The selection of the number of tempering times of 1 - 3 times per layer can be optimized according to the specific material and performance requirements of the product.

[0025] Preferably, the laser power during the in-situ interlayer tempering process is 120 W, the scanning speed is 1500 mm / s, non-melting scanning is performed on the formed layer, and the interlayer cooling rate is controlled to be 30 °C / s.

[0026] Furthermore, in the above method for regulating the microstructure and fatigue properties of nickel-based superalloys prepared by LPBF, in S4, the crystal orientation deviation of the single-crystal seed layer of the substrate is set to be <3°, and the substrate is preheated to 150 - 180 °C; the single-crystal seed layer realizes the directional arrangement of grains along the main stress axis direction of the product through epitaxial growth technology.

[0027] Setting the crystal orientation deviation of the single-crystal seed layer of the substrate to be <3° can ensure a high degree of orientation of grains along the main stress axis direction during the growth process. Such directionally arranged grains can reduce the sensitivity of crack initiation at grain boundaries, and reducing the angle between the grain boundary and the main stress direction can improve the crack propagation resistance of the material, thereby significantly enhancing the fatigue performance of the material. Preheating the substrate to 150 - 180 °C can reduce the temperature gradient between the molten pool and the substrate, reduce the generation of thermal stress. At the same time, preheating can also promote the epitaxial growth of grains, making the grains more continuous and dense, and further optimizing the microstructure.

[0028] Furthermore, in the above method for regulating the microstructure and fatigue properties of nickel-based superalloys prepared by LPBF, the grain orientation ratio of the product is >85%, the fatigue fracture surface shows a dimpled morphology, and the crack sources are dispersed.

[0029] Furthermore, in the above method for regulating the microstructure and fatigue performance of nickel-based superalloys prepared by LPBF, in step S6, the product is separated from the substrate by wire cutting, and then double aging treatment is carried out. The double aging treatment is set as follows: heat preservation at (710-730)°C for 8 h, and then heat preservation at (610-630)°C for another 8 h, followed by furnace cooling; after the double aging heat treatment, the γ' phase of the product is dispersed, and the spacing is ≤200 nm.

[0030] In step S6, after standing until the substrate cools to room temperature, the formed product is taken out from the forming chamber.

[0031] Preferably, the double aging treatment is set as follows: heat preservation at 720°C for 8 h, and then heat preservation at 620°C for another 8 h, followed by furnace cooling.

[0032] Using wire cutting technology to separate the product from the substrate has the advantages of high cutting accuracy and small heat-affected zone, etc., and can avoid the deformation and damage that may be brought by traditional machining methods. After printing, double aging heat treatment is carried out on the product. After the double aging treatment, the γ' phase of the product is dispersed, and the spacing is ≤200 nm. This dispersed γ' phase can form a uniform strengthening phase network, effectively hindering the movement of dislocations, improving the strength and hardness of the material. At the same time, the dispersed γ' phase can also improve the fatigue resistance of the material and delay the crack propagation speed, thus significantly improving the fatigue life and reliability of the product.

[0033] Compared with the prior art, the present invention has the following beneficial effects: (1) The method for regulating the microstructure and fatigue performance of nickel-based superalloys prepared by LPBF disclosed in the present invention delays oxidation damage by doping Yb2SiO5 powder into the LPBF forming powder (nickel-based superalloy powder) and utilizing the self-healing potential in rare earth silicates. At the same time, the nanoparticles serve as heterogeneous nucleation cores, reducing the nucleation energy barrier of the precipitated phase and increasing the density of the precipitated phase; at the same time, the silicate phase has better stability than oxides in an environment containing S / Cl, further improving the life of the product (such as turbine blades); (2) The method for regulating the microstructure and fatigue performance of nickel-based superalloys prepared by LPBF disclosed in the present invention uses low-power laser scanning to perform non-melting tempering on the formed layer, and utilizes the heat accumulation effect to promote the in-situ aging precipitation of the γ' phase. And it can be achieved by regulating the tempering times of 1-3 times per layer and the interlayer cooling rate within 10-50°C / s; after printing, combined with aging heat treatment, controlling the γ' phase size ≤50 nm and the volume fraction of 40-60%, the dispersed distribution spacing of the precipitated phase ≤200 nm can be realized; while shortening the process chain, defects are eliminated, and the phase distribution uniformity is improved; (3)The method for regulating the microstructure and fatigue performance of nickel-based superalloys prepared by LPBF disclosed in the present invention adopts a 67° rotation scanning strategy and combines a substrate pre-placed single crystal seed layer with an orientation deviation <3° to achieve the strengthening of the epitaxial texture in the direction of the main stress axis of the blade, making the proportion of the single crystal seed layer orientation >85% and reducing the sensitivity of grain boundary crack initiation. A controllable grain morphology and precipitate size are constructed to form multiple anti-fatigue barriers. Description of the Drawings

[0034] Figure 1 It is the grain orientation map of the electron backscatter diffraction (EBSD) of the turbine blade prepared in Example 1 of the present invention; Figure 2 It is the grain boundary angle map of the electron backscatter diffraction (EBSD) of the turbine blade prepared in Example 1 of the present invention; Figure 3 It is the grain size map of the electron backscatter diffraction (EBSD) of the turbine blade prepared in Example 1 of the present invention; Figure 4 It is the transmission electron microscopy (TEM) test result map of the turbine blade prepared in Example 1 of the present invention; Figure 5 It is the fatigue fracture surface map of the turbine blade prepared in Example 1 of the present invention ((a) and (b) are both Example 1). Detailed Embodiments

[0035] Next, Example 1, Example 2, and Example 3 will be combined with specific experimental data and the attached Figures 1 to 5 , and the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Unless otherwise specified, the raw materials, methods, and equipment used in the embodiments of the present invention are conventional raw materials, methods, and equipment in the technical field.

[0036] The raw material information used in the embodiments of the present invention is as follows: Nickel-based superalloy powder: The nickel-based superalloy powder sections with the grades of GH4169, GH4738, and GH4033 corresponding to GB / T 14992-2005 are subjected to gas atomization treatment. The powder particle size is 15~53μm, the fluidity is Hall flow rate ≤25s / 50g, and the oxygen content is ≤200ppm. The required particle size and performance requirements are achieved through argon cycle drying and mechanical screening.

[0037] Doped powder: Commercial rare earth silicate Yb2SiO5 nano powder, with a powder particle size of 50~200nm.

[0038] The following Examples 1, 2, and 3 provide a method for regulating the microstructure and fatigue properties of nickel-based high-temperature alloys prepared by LPBF.

[0039] Example 1 The method for regulating the microstructure and fatigue properties of a nickel-based high-temperature alloy prepared by LPBF in Example 1 comprises the following steps: S1: Mixing gas-atomized GH4169 powder with Yb2SiO5 nanopowder (the amount of Yb2SiO5 is 0.6wt% of the GH4169 powder). Then, the mixed powder is placed in a planetary ball mill for thorough mixing. S2: Place the processed mixed powder into the forming chamber of the LPBF printing device, and use tools to level the substrate, scraper and mixed powder; import the turbine blade model into the LPBF printing device, and use software to slice the imported turbine blade model; set the process parameters of the LPBF printing device: the laser power of the LPBF process printing process is 300W, the scanning speed is 700mm / s, the scanning pitch is 0.1mm, the powder layer thickness is 60μm, and the scanning direction rotates 67° per layer; the laser power of the interlayer in-situ tempering process is 120W, the scanning speed is 1500mm / s, the formed layer is scanned without melting, the interlayer cooling rate is controlled at 30℃ / s, and the number of tempering times is 2 times / layer; S3: Before printing, fill with argon gas, requiring the oxygen content in the atmosphere of the forming chamber to drop to <15 ppm; S4: Using the single crystal seed layer pre-setting technology, the single crystal seed layer of the substrate of the LPBF printing equipment has a crystal orientation deviation of <001> <3, and the preheating temperature of the substrate is 150°C; S5: When the oxygen content of the atmosphere in the forming chamber drops to less than 15 ppm and the substrate temperature rises to 120°C, click the forming button of the LPBF printing device until the turbine blade is printed; S6: After printing is completed, the substrate is allowed to cool to room temperature, and the substrate is separated from the substrate using wire cutting technology, and then double aging treatment is performed. The double aging treatment is set to: 720℃ / 8h and 620℃ / 8h furnace cooling to obtain the turbine blade of Example 1.

[0040] Example 2 The method for regulating the microstructure and fatigue properties of a nickel-based high-temperature alloy prepared by LPBF in Example 2 comprises the following steps: S1: Mix the gas-atomized GH4738 powder with Yb2SiO5 nanopowder (0.4 wt% of GH4141 powder). Then, place the mixed powder in a planetary ball mill for thorough mixing. S2: Put the processed mixed powder into the forming chamber of the LPBF printing device, and use tools to level the substrate, scraper, and mixed powder; import the turbine blade model into the LPBF printing device, and use software to slice the imported turbine blade model; set the process parameters of the LPBF printing device: the laser power during the LPBF process printing is 350 W, the scanning speed is 750 mm / s, the scanning spacing is 0.1 mm, the powder spreading layer thickness is 60 μm, and the scanning direction rotates 67° per layer; the laser power during the in-situ tempering process between layers is 120 W, the scanning speed is 1500 mm / s, perform non-melting scanning on the formed layer, control the cooling rate between layers to be 35 °C / s, and the tempering times are 1 time / layer; S3: Before printing, fill with argon, and require the oxygen content in the atmosphere of the forming chamber to be reduced to <15 ppm; S4: Adopt the single crystal seed layer pre-setting technology, so that the <001> crystal orientation deviation of the single crystal seed layer of the substrate of the LPBF printing device is <3, and the preheating temperature of the substrate is 180 °C; S5: When the oxygen content in the atmosphere of the forming chamber is reduced to <15 ppm and the substrate temperature rises to 150 °C, click the forming button of the LPBF printing device until the turbine blade printing is completed; S6: After printing is completed, wait until the substrate cools to room temperature, use wire cutting technology to separate it from the substrate, and then perform double aging treatment. The double aging treatment is set as: furnace cooling at 720 °C / 8 h and 620 °C / 8 h to obtain the turbine blade of Example 2.

[0041] Example 3 The method for regulating the microstructure and fatigue performance of nickel-based superalloy prepared by LPBF in Example 3 includes the following steps: S1: Mix the gas atomized GH4033 powder with Yb2SiO5 nano powder (the doping amount is 0.8 wt% of the GH4133 powder), and then place the mixed powder in a planetary ball mill for sufficient mixing; S2: Put the processed mixed powder into the forming chamber of the LPBF printing device, and use tools to level the substrate, scraper, and mixed powder; import the turbine blade model into the LPBF printing device, and use software to slice the imported turbine blade model; set the process parameters of the LPBF printing device: the laser power during the LPBF process printing is 370 W, the scanning speed is 700 mm / s, the scanning spacing is 0.1 mm, the powder spreading layer thickness is 60 μm, and the scanning direction rotates 67° per layer; the laser power during the in-situ tempering process between layers is 120 W, the scanning speed is 1500 mm / s, perform non-melting scanning on the formed layer, control the cooling rate between layers to be 20 °C / s, and the tempering times are 3 times / layer; S3: Before printing, argon is filled in, and it is required that the oxygen content in the atmosphere of the forming chamber is reduced to <15 ppm; S4: The single-crystal seed layer pre-setting technology is adopted to make the <001> crystal orientation deviation of the substrate of the LPBF printing equipment less than 3, and the preheating temperature of the substrate is 180 °C; S5: When the oxygen content in the atmosphere of the forming chamber is reduced to <15 ppm and the substrate temperature rises to 120 °C, click the forming button of the LPBF printing equipment until the turbine blade printing is completed; S6: After printing is completed, it is left stationary until the substrate cools to room temperature, and it is separated from the substrate by wire cutting technology, and then double aging treatment is carried out. The double aging treatment is set as: furnace cooling at 720 °C / 8 h and 620 °C / 8 h to obtain the turbine blade of Example 3.

[0042] Effect verification The turbine blade prepared in Example 1 is tested, and the test results are as Figure 1 、 2 、3, 4, 5 show.

[0043] From Figure 1 、 2 、3, 4, 5, it can be seen that: (1) Doping Yb2SiO5 nano-powder in nickel-based superalloy and achieving uniform dispersion through planetary ball milling process, combined with adjusting the substrate preheating temperature to 150 - 180 °C, has a significant impact on the solidification behavior of the LPBF forming melt pool and the thermal accumulation effect; (2) Yb2SiO5 nano-powder serves as a heterogeneous nucleation core, effectively reducing the nucleation energy barrier of the γ' phase. At the same time, the oxidation resistance of the silicate phase inhibits high-temperature oxidation damage; through the 67° rotation scanning strategy and the single-crystal seed layer pre-setting technology, the grains grow epitaxially along the main stress axis direction of the turbine blade, and the formed texture is as Figure 1 、 2 、3 show; (3) As Figure 4 shows, for the nickel-based superalloy formed by LPBF under the method of the present invention, the size of the γ' phase is controlled below 50 nm and is dispersed, which can effectively hinder dislocation slip and inhibit crack propagation; (4) As can be seen from the fatigue fracture surface diagram as Figure 5 shows, the turbine blade of Example 1 prepared by the method of the present invention presents a dimpled fracture morphology and dispersed crack sources, confirming the improvement of fatigue life by the synergistic effect of grain boundary strengthening, precipitate phase optimization and nano-particles.

[0044] In summary, the present invention provides a method for regulating the microstructure and fatigue properties of nickel-based superalloys prepared by LPBF, which can synergistically optimize the precipitate distribution, grain orientation and defect suppression, make the fatigue fracture surface present a dimpled morphology, significantly improve the fatigue life and reliability, and is applicable to the manufacture of aeroengine turbine blades.

[0045] There are many specific application ways of the present invention, and the above description is only the preferred embodiment of the present invention. It should be noted that the above embodiments are only used to illustrate the present invention and are not used to limit the protection scope of the present invention. For those of ordinary skill in the art of the present technology, without departing from the principle of the present invention, several improvements can be made, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. A method for regulating the microstructure and fatigue properties of nickel-based superalloys prepared by LPBF, characterized in that The steps include: S1: placing the prepared nickel-based high-temperature alloy powder and the doping powder in a ball mill and fully mixing them to obtain a mixed powder; S2: placing the mixed powder into a forming chamber of an LPBF printing device, importing a product model into the LPBF printing device, printing the product layer by layer using an LPBF process, and performing an interlayer in-situ tempering process after each layer is printed, planning a printing path and an interlayer in-situ tempering path; S3: Before printing, fill with argon gas and ensure that the oxygen content in the atmosphere of the forming chamber is reduced to <15 ppm; S4: Using single crystal seed layer pre-deposition technology, the substrate of the LPBF printing equipment is controlled for crystal orientation deviation and preheated; S5: Click the forming button of the LPBF printing device until the product is printed; S6: Take out the formed product from the forming chamber and separate the product from the substrate by cutting.

2. The method for regulating the microstructure and fatigue properties of nickel-based superalloys prepared by LPBF according to claim 1, wherein, In S1, the nickel-based high-temperature alloy powder is a gas-atomized Ni-Cr-Fe-Co-Mo-Ti-Al pre-alloyed powder; the doped powder is rare earth silicate Yb2SiO5 and the doping amount is 0.4-0.8 wt% of the nickel-based high-temperature alloy powder.

3. The method for regulating the microstructure and fatigue properties of nickel-based superalloys prepared by LPBF according to claim 2, characterized in that The nickel-based high-temperature alloy powder is dried by argon circulation and mechanically screened to control its powder particle size to 15-53 μm, fluidity to a Hall flow rate of ≤25 s / 50 g, and oxygen content to ≤200 ppm; the powder particle size of the doped powder is 50-200 nm.

4. The method for regulating the microstructure and fatigue properties of nickel-based superalloys prepared by LPBF according to claim 1, characterized in that In S1, the ball mill is a planetary ball mill.

5. The method for regulating the microstructure and fatigue properties of nickel-based superalloys prepared by LPBF according to claim 1, characterized in that The product in S2 is a turbine blade.

6. The method for regulating the microstructure and fatigue properties of nickel-based superalloys prepared by LPBF according to any one of claims 1 or 5, characterized in that, The process parameters of the LPBF printing equipment are set as follows: the laser power of the LPBF printing process is 300-400 W, the scanning speed is 650-800 mm / s, the scanning pitch is 0.1-0.3 mm, the powder layer thickness is 40-60 μm, and the scanning direction rotates 67° per layer.

7. The method for controlling the microstructure and fatigue properties of a nickel-based superalloy prepared by LPBF according to any one of claims 1 or 5, wherein the process parameters of the LPBF printing equipment are set as follows: the laser power during the interlayer in-situ tempering process is 110-150 W, the scanning speed is 1200-1500 mm / s, the formed layer is scanned non-meltingly, and the interlayer cooling rate is controlled at 10-50°C / s; the number of tempering times during the interlayer in-situ tempering process is 1-3 times / layer, and the γ′ phase precipitation size of the product is ≤50 nm, with a volume fraction of 40-60%.

8. The method for regulating the microstructure and fatigue properties of nickel-based superalloys prepared by LPBF according to any one of claims 1 or 5, characterized in that, In S4, the crystal orientation deviation of the single crystal seed layer of the substrate is set to be less than 3°, and the substrate is preheated to 150-180° C.; the single crystal seed layer is epitaxially grown to achieve directional arrangement of grains along the principal stress axis of the product.

9. The method for regulating the microstructure and fatigue properties of nickel-based superalloys prepared by LPBF according to claim 8, wherein, The grain orientation of the product is greater than 85%, the fatigue fracture has a dimple-like morphology, and the crack sources are dispersed.

10. The method for regulating the microstructure and fatigue properties of nickel-based superalloys prepared by LPBF according to any one of claims 1 or 5, characterized in that, In S6, the product is separated from the substrate by wire cutting, and then double aging treatment is performed. The double aging treatment is set as follows: (710-730)°C for 8 hours, (610-630)°C for another 8 hours, and furnace cooling. After the double aging heat treatment, the γ′ phase of the product is dispersed with a spacing of ≤200 nm.

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