Micro-channel selective melting additive manufacturing method for nickel-based C276 material with ultra-small bending radius

Abstract

The invention discloses a selective melting additive manufacturing method for a nickel-based C276 material micro-channel with an ultra-small bending radius. The method comprises the steps that high-precision three-dimensional modeling is conducted on a target micro-channel part with the ultra-small bending radius; obtaining a minimum support structure according to the geometric features and the thermal field simulation result, and embedding the minimum support structure into the STL file to form a complete construction file; according to the complete construction file, printing parameters of a printer are dynamically adjusted in the selective melting process in combination with the target micro-channel part configuration and C276 powder characteristics; carrying out support structure removal and annealing treatment on the printed piece; and the printed piece is subjected to inner wall roughness polishing. By means of the manufacturing method, the nickel-based C276 material micro-channel part with the ultra-small bending radius can be manufactured, wherein the nickel-based C276 material micro-channel part is high in ultra-small bending radius adaptability, high in size precision, excellent in surface quality, low in residual stress and resistant to corrosion.

Description

Technical Field

[0001] This invention relates to an additive manufacturing method with an ultra-small bending radius, and more particularly to a microchannel selective melting additive manufacturing method for nickel-based C276 material with an ultra-small bending radius. Background Technology

[0002] Microchannel components made of nickel-based C276 with ultra-small bending radii have wide applications in many high-end fields due to their excellent corrosion resistance, mechanical properties, and thermal stability. Especially in the fine chemical industry, these microchannel components can serve as transport and reaction carriers for highly corrosive fluids, significantly improving reaction efficiency and safety. In the aerospace field, their ultra-small bending radius makes them suitable for complex cooling circuits in engines and gas turbines, enabling efficient thermal management within extreme space constraints. Furthermore, in high-precision medical implants and miniature high-efficiency heat exchangers, C276 microchannel structures not only ensure biocompatibility and microstructural stability but also withstand long-term corrosion and complex physiological environments. However, due to the high complexity of the microchannel's ultra-small bending radius structure and the high melting point, high strength, and high chemical inertness of the C276 nickel-based alloy itself, existing traditional manufacturing processes generally face prominent challenges in achieving high curvature, narrow channels, and high density forming. These challenges include difficulty in achieving uniform wall thickness, low channel closure, difficulty in ensuring forming accuracy and surface quality, high residual stress, easy warping and deformation, low material utilization, and difficulty in controlling the consistency of large-size complex structures. These challenges severely limit the large-scale application and service reliability of ultra-small bending radius nickel-based C276 microchannel parts in high-end equipment.

[0003] Selective laser melting (SLM), a representative technology of powder bed fusion additive manufacturing, can directly form near-net-shape, complex internal flow channels, and microstructured integrated metal components through a layer-by-layer melting-solidification mechanism, and has been widely used in high-end equipment manufacturing. However, when processing nickel-based superalloys (such as C276 and Hastelloy X), SLM still faces defects such as columnar crystal growth, elemental segregation, porosity, and susceptibility to hot cracking due to concentrated energy input, large thermal gradient, and extremely high cooling rate. Traditional single-layer constant power and fixed scanning strategies lack real-time feedback, making it difficult to balance density, surface roughness, and geometric consistency. Although subsequent conventional heat treatment or hot isostatic pressing can heal defects to some extent, it is time-consuming and costly, and for microchannel components with extremely small curvature, there are problems with dimensional deformation and difficulty in controlling internal wall roughness. Overall, these limitations restrict the reliability and large-scale application of nickel-based superalloy SLM parts. Although the SLM-C276 technology has made some progress in industrial verification, it is still insufficient for the synergistic regulation of microstructure and properties in extremely complex structures, especially in suppressing microcracks, improving inner wall quality, and achieving mass consistency. Summary of the Invention

[0004] The purpose of this invention is to provide a selective melting additive manufacturing method for microchannels made of nickel-based C276 material with an ultra-small bending radius, which can produce microchannel parts made of nickel-based C276 material with an ultra-small bending radius that have strong adaptability to ultra-small bending radius, high dimensional accuracy, excellent surface quality, low residual stress and corrosion resistance.

[0005] Technical solution: The microchannel selective melting additive manufacturing method for nickel-based C276 material with ultra-small bending radius described in this invention includes the following steps: Step 1: Perform high-precision 3D modeling of the target microchannel part with an ultra-small bending radius and output an STL file for printing; Step 2: Receive the STL file, obtain the minimum support structure based on the geometric features and thermal field simulation results, and embed the minimum support structure into the STL file to form a complete build file; Step 3: Based on the complete construction file, during the selective melting process, dynamically adjust the printer's printing parameters according to the target microchannel part configuration and the characteristics of C276 powder to achieve powder-configuration coupling and densification to output printed parts. Step 4: Remove the support structure and perform segmented annealing on the printed parts to eliminate residual stress. Step 5: Polish the inner wall roughness of the printed part to obtain the target microchannel part.

[0006] Furthermore, in step 1, the specific steps for performing high-precision 3D modeling of the target microchannel part with an ultra-small bending radius are as follows: Step 1.1: Model the target microchannel part in the Solidworks software environment and ensure that it meets the process constraints. Step 1.2: Compare the minimum wall thickness feature, overhang angle feature, closed cavity feature, and powder discharge channel feature item by item, and make geometric corrections to the risk items based on the comparison results; Step 1.3: Evaluate the placement direction by combining the center of gravity, support amount, and thermal distortion to obtain the optimal placement direction that balances molding quality and efficiency. Step 1.4: Unify the normal of the triangular face, repair missing edges and holes in the force lines, re-lay the mesh in sparse areas, correct the closure of the STL file, and output a closed STL file.

[0007] Furthermore, in step 2, the specific steps for obtaining the minimized support structure based on geometric features and thermal field simulation results are as follows: Step 2.1: Delineate risk zones based on the geometric characteristics of the target microchannel component and the results of thermal field simulation, and set up support structures for each risk zone; Step 2.2: Call the Ansys Additive thermo-mechanical iteration module to perform cyclic simulation on the currently set support structure, and dynamically adjust the support density of the support structure or apply reverse compensation according to the thermal stress threshold and the warping threshold. Step 2.3: When the simulation results of the Ansys Additive thermo-mechanical iteration module show that the thermal stress and warpage meet the thermal stress threshold and warpage threshold respectively, the currently set support structure is taken as the minimum support structure.

[0008] Furthermore, in step 2.1, the specific steps for setting up the support structures for each risk zone are as follows: Step 2.1.1: Determine the risk level of the risk area, including high-risk areas, medium-risk areas, and low-risk areas; Step 2.1.2: If the risk area is a high-risk area, the support structure adopts a conical support and an additional heat-conducting frame is arranged along the inner side of the thin wall; if the risk area is a medium-risk area, the support structure adopts a line-surface hybrid tree-like support; if the risk area is a low-risk area, the support structure adopts a directional support.

[0009] Furthermore, in step 3, the specific steps for dynamically adjusting the printer's printing parameters based on the target microchannel component configuration and the characteristics of C276 powder are as follows: Step 3.1: Preset the printer's printing parameters based on the particle size, sphericity, and geometric information of the C276 powder and the supporting structure; Step 3.2: Capture the printer's monitoring parameters through high frame rate vision, radiation thermometry, and interlayer infrared thermal imaging. The monitoring parameters include melt pool width, melt pool peak temperature, and powder uniformity. Step 3.3: During the printing process, fine-tune the printing parameters based on the monitoring data to achieve closed-loop control of the energy density of the printed parts, defect suppression, and densification.

[0010] Furthermore, in step 3.1, the specific steps for presetting the printer's printing parameters based on the C276 powder particle size, sphericity, and the geometric information of the support structure are as follows: Step 3.1.1: Determine the printer's printing parameters based on the particle size, sphericity, and geometric information of the C276 powder and the support structure. The printing parameters include laser power, scanning rate, powder thickness, overlap rate, and inert atmosphere flow rate. Step 3.1.2: Set the laser power range to 200~320 W and the scanning rate range to 600~900 mm / s. -1 The powder coating thickness ranges from 20 to 30 µm, the overlap rate ranges from 35 to 45%, and the inert atmosphere flow rate ranges from 35 to 45 L / min. -1 ; Step 3.1.3: Set the corresponding printing parameters according to the set value ranges, and use different value combinations to form multiple printing parameter groups; Step 3.1.4: Conduct printing experiments on each printing parameter group, and select six printing parameter groups with a printing relative density > 99.9% and a melting depth between 1.4 and 1.6 times the powder thickness to write them into the printing database; Step 3.1.5: Select a print parameter group from the print database to preset the printer's print parameters.

[0011] Furthermore, in step 3.3, the specific steps for fine-tuning the printing parameters based on monitoring data during the printing process are as follows: Step 3.3.1: Real-time capture of molten pool width and peak molten pool temperature; Step 3.3.2: Compare the captured molten pool width and peak temperature with the width threshold and peak temperature threshold, respectively; Step 3.3.3: Based on the comparison results, fine-tune the laser power, scanning rate, inert atmosphere flow rate, and powder thickness of the next layer without pausing the printer.

[0012] Furthermore, in step 4, the specific steps for removing the support structure and performing segmented annealing on the printed part are as follows: Step 4.1: Cool the printed part to the range of 35~45℃, and then move it together with the substrate into the argon glove box. Use a continuous fiber laser to cut the support structure, and then use a sanding belt and a ceramic bead jet to remove the excess support structure in two stages. The surface roughness Ra is controlled between 5~7 µm. Step 4.2: Use a non-contact blue light scanner to remeasure the external dimensions of the printed part, and record the positions where the deviation exceeds ±30µm; Step 4.3: Perform three-stage annealing on the printed parts in a tube vacuum furnace; Step 4.4: Record the energy changes of the elastic wave release using an acoustic emission sensor. Use the total elastic wave energy recorded during the first complete thermal cycle as a baseline value. In subsequent heat treatments, start the cooling section when the accumulated elastic wave energy reaches 90% of the baseline value. The cooling rate of the cooling section is set to 8°C / min. -1 After the temperature cools to 400℃, it is then slowly reduced to 80℃ using a furnace-cooled method.

[0013] Furthermore, in step 4.3, when performing three-stage annealing on the printed parts using a tube vacuum furnace, the three-stage annealing specifically involves: The first stage is the stress relief stage, in which the temperature inside the tubular vacuum furnace is increased by 8 °C / min. -1The temperature is rapidly increased to a range of 640~660 ℃ and held at that temperature for 2 h. The second stage is the recrystallization stage, in which the temperature inside the tube vacuum furnace is increased by 6 °C / min under the conditions of a hydrogen-nitrogen-argon mixed gas and a pH of 10 kPa. -1 The temperature was rapidly increased to a range of 1040–1060 °C and held at that temperature for 1 hour. The third stage is the precipitation control stage, in which the temperature inside the tube vacuum furnace is increased at 3 °C / min under a pure argon atmosphere. -1 The temperature was reduced from 1040~1060 ℃ to 860~880 ℃ at a rate of 4 h, and then kept at 860~880 ℃ for 4 h.

[0014] Furthermore, in step 5, the specific steps for roughening the inner wall of the printed part are as follows: Step 5.1: Immerse the printed part in a chemical polishing solution composed of HF, HNO3, and deionized water, with volume fractions of HF, HNO3, and deionized water of 5%, 15%, and 80%, respectively. Step 5.2: After ultrasonically stirring in the chemical polishing solution for 30 seconds, the printed part is taken out and then rinsed with deionized water and anhydrous ethanol in sequence, and then dried with 80 ℃ hot air. Step 5.3 involves curing the passive film on the surface at a low temperature of 400 ℃ for 4 h, which precipitates fine carbides to achieve precipitation strengthening.

[0015] Compared with existing technologies, the advantages of this invention are as follows: by obtaining a minimized support structure based on geometric features and thermal field simulation results, the minimum generation of the support structure is achieved, thus meeting printing requirements; by dynamically adjusting the printer's printing parameters in conjunction with the target microchannel part configuration and C276 powder characteristics, the printing parameters are adjusted in real time to maintain the optimal printing state at all times; by performing segmented annealing on the printed parts, effective residual stress release, grain refinement, and uniform carbide precipitation are achieved, thereby significantly improving the service reliability and extreme condition adaptability of the microchannel parts. Attached Figure Description

[0016] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram of the three-dimensional modeling and mesh repair process of the present invention; Figure 3 This is a schematic diagram of gradient support generation according to the present invention; Figure 4 This is a schematic diagram of metallographic testing of the post-polishing treatment of the present invention; Figure 5 The figure shows the tensile test results of the C276 spline of the present invention. Detailed Implementation

[0017] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the embodiments described.

[0018] like Figure 1 As shown, the microchannel selective melting additive manufacturing method for nickel-based C276 material with ultra-small bending radius disclosed in this invention includes the following steps: Step 1: Perform high-precision 3D modeling of the target microchannel part with an ultra-small bending radius and output an STL file for printing; Step 2: Receive the STL file, obtain the minimum support structure based on geometric features and thermal field simulation results, and embed the minimum support structure into the STL file to form a complete build file. The complete build file is a 3mf build file, which contains the support removal sequence and anti-collision path information, and can be directly used for printing. Step 3: Based on the complete construction file, during the selective melting process, dynamically adjust the printer's printing parameters according to the target microchannel part configuration and the characteristics of C276 powder to achieve powder-configuration coupling and densification to output printed parts. Step 4: Remove the support structure and perform segmented annealing on the printed parts to eliminate residual stress. Step 5: Polish the inner wall roughness of the printed part to obtain the target microchannel part.

[0019] By obtaining a minimized support structure based on geometric features and thermal field simulation results, the support structure is generated to meet printing requirements. By dynamically adjusting the printer's printing parameters in conjunction with the target microchannel part configuration and C276 powder characteristics, the printing parameters are adjusted in real time to maintain optimal printing conditions. By performing segmented annealing on the printed parts, effective residual stress release, grain refinement, and uniform carbide precipitation are achieved, thereby significantly improving the service reliability and extreme condition adaptability of the microchannel parts.

[0020] Furthermore, in step 1, the specific steps for performing high-precision 3D modeling of the target microchannel part with an ultra-small bending radius are as follows: Step 1.1: Model the target microchannel part in the Solidworks software environment and ensure that it meets the process constraints. The process constraints require a minimum bending radius of 10 mm, a wall thickness of ≥100 µm, and a closed cavity with a powder discharge channel of ≥0.4 mm. Step 1.2: Compare the minimum wall thickness feature, overhang angle feature, closed cavity feature, and powder discharge channel feature item by item. The threshold for the overhang angle feature is set to 45°. Based on the comparison results, the risk items are geometrically corrected by calling the "Local Relaxation-Rounding-Rib Reinforcement" tool. Step 1.3: Evaluate the placement direction by combining the center of gravity, support amount, and thermal distortion. Calculate the comprehensive score of center of gravity-support amount-thermal distortion. Select the three placement directions with the highest scores based on the comprehensive score. Then, the operator selects and locks the placement direction with the smallest thermal deformation, thus obtaining the optimal placement direction that balances molding quality and efficiency. Step 1.4: After model geometry correction and placement orientation locking, perform a final check and repair on the mesh exported to STL to ensure consistent triangular face normals, eliminate missing force lines and holes, re-mesh sparse areas, and correct the closure of the STL file, such as... Figure 2 As shown, the final output is a closed STL that satisfies the requirements of subsequent slicing and printing processes in terms of both geometry and mesh. This allows us to utilize the final model shape and orientation information determined in the previous steps, while also thoroughly removing all mesh defects before actual slicing, ensuring printing quality.

[0021] Furthermore, in step 2, the specific steps for obtaining the minimized support structure based on geometric features and thermal field simulation results are as follows: Step 2.1: Based on the geometric characteristics of the target microchannel component and the results of thermal field simulation, risk zones are delineated, and support structures are set for each risk zone, such as... Figure 3 As shown, the support structure is generally a multi-layered, gradient support structure with denser support at the top and sparser support at the bottom. Thermally conductive / stabilizing frame supports are inserted for local overheating or easily deformable locations. The denser support at the top and sparser support at the bottom is set to use high-density, small-pitch support near the important forming surface (upper overhang surface) of the printed part, and the support becomes sparser further away from the critical parts. Step 2.2: Call the Ansys Additive thermal-mechanical iteration module to perform cyclic simulation on the currently set support structure, and dynamically adjust the support density of the support structure or apply reverse compensation according to the thermal stress threshold and the warpage threshold. The thermal stress threshold is set to be greater than 300 MPa, and the warpage threshold is set to be greater than 1% of the wall thickness. Step 2.3: When the simulation results of the Ansys Additive thermo-mechanical iteration module show that the thermal stress and warpage meet the thermal stress threshold and warpage threshold respectively, the currently set support structure is taken as the minimum support structure.

[0022] Furthermore, in step 2.1, the specific steps for setting up the support structures for each risk zone are as follows: Step 2.1.1: Determine the risk level of the risk area, including high-risk areas, medium-risk areas, and low-risk areas; Step 2.1.2: If the risk area is a high-risk area, the support structure adopts a conical support with a tip diameter of 80µm, a root diameter of 160µm, and a step distance of 0.6mm, and an additional heat-conducting frame is arranged along the inner side of the thin wall; if the risk area is a medium-risk area, the support structure adopts a line-surface hybrid tree-like support; if the risk area is a low-risk area, the support structure adopts a directional support.

[0023] Furthermore, in step 3, the specific steps for dynamically adjusting the printer's printing parameters based on the target microchannel component configuration and the characteristics of C276 powder are as follows: Step 3.1: Preset the printer's printing parameters based on the particle size, sphericity, and geometric information of the C276 powder and the supporting structure; Step 3.2: Capture the printer's monitoring parameters through high frame rate vision, radiation thermometry, and interlayer infrared thermal imaging. The monitoring parameters include melt pool width, melt pool peak temperature, and powder uniformity. Step 3.3: During the printing process, fine-tune the printing parameters based on the monitoring data to achieve closed-loop control of the energy density of the printed parts, defect suppression, and densification.

[0024] Furthermore, in step 3.1, the specific steps for presetting the printer's printing parameters based on the C276 powder particle size, sphericity, and the geometric information of the support structure are as follows: Step 3.1.1: Determine the printer's printing parameters based on the particle size, sphericity, and geometric information of the C276 powder and the support structure. The printing parameters include laser power, scanning rate, powder thickness, overlap rate, and inert atmosphere flow rate. Step 3.1.2: Set the laser power range to 200~320 W and the scanning rate range to 600~900 mm / s. -1 The powder coating thickness ranges from 20 to 30 µm, the overlap rate ranges from 35% to 45%, and the inert atmosphere flow rate ranges from 35% to 45 L / min. -1 ; Step 3.1.3: Set the corresponding printing parameters according to the set value ranges, and use different value combinations to form multiple printing parameter groups; Step 3.1.4: Conduct printing experiments for each set of printing parameters, such as... Figure 4As shown, by measuring the melt depth and overlap width under a microscope and analyzing the porosity using metallographic images, six sets of printing parameters with a relative density >99.9% and a melt depth between 1.4 and 1.6 times the powder thickness were selected and written into the printing database. The relative density refers to the ratio of the actual density of the specimen to the theoretical density of the material, reflecting the quality of curing. For example, when the powder thickness is set to 50 µm, the corresponding melt depth should be between 70 µm (50 µm × 1.4) and 80 µm (50 µm × 1.6). In this way, it is ensured that the selected parameters can achieve full melting while avoiding overheating or damage to the substrate. Step 3.1.5: Select a print parameter group from the print database to preset the printer's print parameters.

[0025] Furthermore, in step 3.3, the specific steps for fine-tuning the printing parameters based on monitoring data during the printing process are as follows: Step 3.3.1: Capture the molten pool width and peak temperature in real time, with a capture period of 10ms; Step 3.3.2: Compare the captured molten pool width and peak temperature with the width threshold and peak temperature threshold, respectively. The width threshold is set to 90~110 µm, and the peak temperature threshold is set to greater than or equal to 2100 K. Step 3.3.3: Based on the comparison results, fine-tune the laser power, scanning rate, inert atmosphere flow rate, and powder thickness of the next layer without pausing the printer. The fine-tuning of the powder thickness is based on the C276 powder particle size distribution, taking D... 50 The half value of (30~40 µm) is used as the maximum adjustment step, that is, each time the scraper stroke is raised or lowered by 20 µm.

[0026] Furthermore, during fine-tuning, the laser power adjustment range is limited to ±10W, and the scanning rate adjustment range is limited to ±20 mm / s. -1 Within this range, the fine-tuning range of the inert atmosphere flow rate is limited to ±3 L / min. -1 Within this range, the fine-tuning of the powder coating thickness is limited to ±20 µm. For example, when the molten pool width exceeds the upper limit of 110 µm, the system will reduce the laser power by 5 W or increase the scanning rate by 10 mm / s. -1 To reduce the molten pool width, when the molten pool width exceeds the lower limit of 90µm, the system increases the laser power by 5 W or decreases the scanning rate by 10 mm / s. -1 To increase the molten pool size; when the peak temperature of the molten pool is below 2100 K, the laser power is increased by 8 W, while the scanning rate is simultaneously reduced by 15 mm / s. -1 All the above fine-tuning is limited to ±10 W (laser power) and ±20 mm / s. -1(Scan rate) and ±3 L min -1 Within the (inert atmosphere flow rate), ensure smooth adjustment without introducing shocks; after these synchronous corrections are completed, the toner spreading unit below the printhead controls the motor to drive the scraper stroke along the Z-axis to increase or decrease, thereby changing the toner spreading thickness: if the energy density decreases, the scraper is raised by 20 µm to increase the toner spreading thickness; if the energy density is too high, the scraper is lowered by 20 µm to reduce the toner spreading thickness. This achieves the purpose of synchronously correcting the toner spreading thickness of the next layer, ensuring a constant energy density.

[0027] Furthermore, during the printing process, the oxygen content in the chamber is continuously monitored. The target oxygen content is less than 50 ppm. When the oxygen content rises above 40 ppm, the inert gas (argon) refresh rate needs to be increased, and a powder layer thickness self-check is triggered to prevent secondary oxidation that could cause splashing and porosity. Data from the entire printing process is fed into a random forest model for training. After printing is completed, the model automatically outputs cross-batch correction coefficients.

[0028] Furthermore, in step 4, the specific steps for removing the support structure and performing segmented annealing on the printed part are as follows: Step 4.1: Cool the printed part to the range of 35~45℃, preferably 40℃, and then move it together with the substrate into an argon glove box. Use a 200 W continuous fiber laser to cut the support structure, and then use a sanding belt and a ceramic bead jet to remove the excess support structure in two stages. The surface roughness Ra is controlled between 5~7 µm. Step 4.2: Use a non-contact blue light scanner (accuracy ±15 µm) to remeasure the external dimensions of the printed part, record the positions where the deviation exceeds ±30 µm, and write them back to the support compensation database for the next round of forming optimization. Step 4.3, in a tube vacuum furnace (ultimate pressure 5 × 10⁻⁶) -3 The printed parts are annealed in three stages within Pa. Step 4.4: Record the energy changes of the elastic wave release using an acoustic emission sensor. Use the total elastic wave energy recorded during the first complete thermal cycle (in the initial stage of the heat treatment process, a complete thermal cycle is performed, and the accumulated elastic wave energy is recorded throughout this process as the total elastic wave energy) as the baseline value (E0). In subsequent heat treatments, when the accumulated elastic wave energy reaches 90% of the baseline value (i.e., 0.9E0), the cooling section is activated to obtain the ideal second phase size and distribution. The cooling rate of the cooling section is set to 8 °C / min. -1 When the temperature is cooled to 400 ℃, it is then slowly reduced to 80 ℃ by furnace cooling to lock the microstructure obtained in the precipitation control stage, taking into account both the stability of the precipitated phase and the comprehensive mechanical properties of the material.

[0029] Furthermore, in step 4.3, when performing three-stage annealing on the printed parts using a tube vacuum furnace, the three-stage annealing specifically involves: The first stage is the stress relief stage, in which the temperature inside the tubular vacuum furnace is increased by 8 °C / min. -1 The temperature is rapidly increased to a range of 640~660 ℃, preferably 650 ℃, and held at 640~660 ℃ for 2 h. The residual stress from processing and welding is eliminated through recovery and dislocation rearrangement, preventing deformation and cracking during subsequent high-temperature operation or service. The second stage is the recrystallization stage, in which the temperature inside the tube vacuum furnace is increased by 6 °C / min under the conditions of a hydrogen-nitrogen-argon mixed gas and a pH of 10 kPa. -1 The temperature is rapidly increased to a range of 1040~1060 ℃, preferably 1050 ℃, and held at 1040~1060 ℃ for 1 hour. This process refines the grains through the growth of new crystal nuclei, eliminates work hardening, restores the plasticity of the material, and lays a uniform parent phase structure for precipitation strengthening. The third stage is the precipitation control stage, in which the temperature inside the tube vacuum furnace is increased at 3 °C / min under a pure argon atmosphere. -1 The temperature is reduced from 1040~1060 ℃ to a temperature range of 860~880 ℃, preferably 870 ℃, and held at 860~880 ℃ for 4 h.

[0030] After a three-stage annealing heat treatment, the residual stress, measured by aperture diffraction, was <80 MPa, the grain size was refined to approximately 10 µm, and Mo-rich M6C carbides precipitated uniformly. Figure 5 As shown, the left side is the SEM microstructure of the fracture surface of the microchannel C276 printed part after tensile fracture (scanning magnification of 2000x, scale of 50 µm). A large number of deep and uniform equiaxed pits and a small number of microcrack initiation zones can be clearly seen. The typical ductile fracture characteristics indicate that the material absorbed a large amount of deformation energy during the tensile process. The right side is the stress-strain curve of the printed part after three-stage annealing. The yield strength of the printed part is about 450 MPa, the tensile strength is about 720 MPa, and the elongation after fracture exceeds 70%.

[0031] In contrast, conventionally rolled or forged C276 sheets typically have an elongation at break of only 40%–55%, and yield strength and tensile strength are mostly between 350 and 550 MPa. Printed parts not only have higher strength but also better ductility. This advantage stems from the three-stage annealing process, which effectively releases residual stress (hole diffraction measurement <80 MPa), refines the grains to approximately 10 µm, and promotes the uniform precipitation of Mo-rich M6C carbides at grain boundaries and within the grains. This achieves a synergistic improvement in both strength and toughness at the microscopic level, significantly enhancing the service reliability and fracture resistance of microchannel components under extreme conditions.

[0032] Furthermore, in step 5, the specific steps for roughening the inner wall of the printed part are as follows: Step 5.1: Immerse the printed part in a chemical polishing solution composed of HF, HNO3, and deionized water, with volume fractions of HF, HNO3, and deionized water of 5%, 15%, and 80%, respectively. Step 5.2: After ultrasonically stirring in the chemical polishing solution for 30 seconds, the printed part is taken out and then rinsed with deionized water and anhydrous ethanol in sequence, and then dried with 80 ℃ hot air. Step 5.3 involves curing the passive film on the surface at a low temperature of 400 ℃ for 4 h, which precipitates fine carbides to achieve precipitation strengthening.

[0033] After grinding to improve the inner wall roughness, the final inner wall roughness measured by white light interferometer was Ra 1.8 µm, the porosity was 0.08%, and the creep life (980 ℃ / 150 MPa) was improved by 22% compared with the unoptimized sample.

[0034] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A method for selective melting additive manufacturing of microchannels using nickel-based C276 material with ultra-small bending radius, characterized in that, Includes the following steps: Step 1: Perform high-precision 3D modeling of the target microchannel part with an ultra-small bending radius and output an STL file for printing; Step 2: Receive the STL file, obtain the minimum support structure based on the geometric features and thermal field simulation results, and embed the minimum support structure into the STL file to form a complete build file; Step 3: Based on the complete construction file, during the selective melting process, dynamically adjust the printer's printing parameters according to the target microchannel part configuration and the characteristics of C276 powder to achieve powder-configuration coupling and densification to output printed parts. Step 4: Remove the support structure and perform segmented annealing on the printed parts to eliminate residual stress. Step 5: Polish the inner wall roughness of the printed part to obtain the target microchannel part.

2. The method for selective melting additive manufacturing of nickel-based C276 microchannels with ultra-small bending radii according to claim 1, characterized in that, In step 1, the specific steps for performing high-precision 3D modeling of the target microchannel part with an ultra-small bending radius are as follows: Step 1.1: Model the target microchannel part in the Solidworks software environment and ensure that it meets the process constraints. Step 1.2: Compare the minimum wall thickness feature, overhang angle feature, closed cavity feature, and powder discharge channel feature item by item, and make geometric corrections to the risk items based on the comparison results; Step 1.3: Evaluate the placement direction by combining the center of gravity, support amount, and thermal distortion to obtain the optimal placement direction that balances molding quality and efficiency. Step 1.4: Unify the normal of the triangular face, repair missing edges and holes in the force lines, re-lay the mesh in sparse areas, correct the closure of the STL file, and output a closed STL file.

3. The method for selective melting additive manufacturing of nickel-based C276 microchannels with ultra-small bending radii according to claim 1, characterized in that, In step 2, the specific steps for obtaining the minimized support structure based on geometric features and thermal field simulation results are as follows: Step 2.1: Delineate risk zones based on the geometric characteristics of the target microchannel component and the results of thermal field simulation, and set up support structures for each risk zone; Step 2.2: Call the Ansys Additive thermo-mechanical iteration module to perform cyclic simulation on the currently set support structure, and dynamically adjust the support density of the support structure or apply reverse compensation according to the thermal stress threshold and the warping threshold. Step 2.3: When the simulation results of the Ansys Additive thermo-mechanical iteration module show that the thermal stress and warpage meet the thermal stress threshold and warpage threshold respectively, the currently set support structure is taken as the minimum support structure.

4. The method for selective melting additive manufacturing of nickel-based C276 microchannels with ultra-small bending radius according to claim 3, characterized in that, In step 2.1, the specific steps for setting up the support structure for each risk zone are as follows: Step 2.1.1: Determine the risk level of the risk area, including high-risk areas, medium-risk areas, and low-risk areas; Step 2.1.2: If the risk area is a high-risk area, the support structure adopts a conical support and an additional heat-conducting frame is arranged along the inner side of the thin wall; if the risk area is a medium-risk area, the support structure adopts a line-surface hybrid tree-like support; if the risk area is a low-risk area, the support structure adopts a directional support.

5. The method for selective melting additive manufacturing of nickel-based C276 microchannels with ultra-small bending radii according to claim 3, characterized in that, In step 3, the specific steps for dynamically adjusting the printer's printing parameters based on the target microchannel component configuration and the characteristics of C276 powder are as follows: Step 3.1: Preset the printer's printing parameters based on the particle size, sphericity, and geometric information of the C276 powder and the supporting structure; Step 3.2: Capture the printer's monitoring parameters through high frame rate vision, radiation thermometry, and interlayer infrared thermal imaging. The monitoring parameters include melt pool width, melt pool peak temperature, and powder uniformity. Step 3.3: During the printing process, fine-tune the printing parameters based on the monitoring data to achieve closed-loop control of the energy density of the printed parts, defect suppression, and densification.

6. The method for selective melting additive manufacturing of nickel-based C276 microchannels with ultra-small bending radii according to claim 5, characterized in that, In step 3.1, the specific steps for presetting the printer's printing parameters based on the C276 powder particle size, sphericity, and the geometric information of the support structure are as follows: Step 3.1.1: Determine the printer's printing parameters based on the particle size, sphericity, and geometric information of the C276 powder and the support structure. The printing parameters include laser power, scanning rate, powder thickness, overlap rate, and inert atmosphere flow rate. Step 3.1.2: Set the laser power range to 200~320 W and the scanning rate range to 600~900 mm / s. -1 The powder coating thickness ranges from 20 to 30 µm, the overlap rate ranges from 35 to 45%, and the inert atmosphere flow rate ranges from 35 to 45 L / min. -1 ; Step 3.1.3: Set the corresponding printing parameters according to the set value ranges, and use different value combinations to form multiple printing parameter groups; Step 3.1.4: Conduct printing experiments on each printing parameter group, and select six printing parameter groups with a printing relative density > 99.9% and a melting depth between 1.4 and 1.6 times the powder thickness to write them into the printing database; Step 3.1.5: Select a print parameter group from the print database to preset the printer's print parameters.

7. The method for selective melting additive manufacturing of nickel-based C276 microchannels with ultra-small bending radii according to claim 5, characterized in that, In step 3.3, the specific steps for fine-tuning the printing parameters based on monitoring data during the printing process are as follows: Step 3.3.1: Real-time capture of molten pool width and peak molten pool temperature; Step 3.3.2: Compare the captured molten pool width and peak temperature with the width threshold and peak temperature threshold, respectively; Step 3.3.3: Based on the comparison results, fine-tune the laser power, scanning rate, inert atmosphere flow rate, and powder thickness of the next layer without pausing the printer.

8. The method for selective melting additive manufacturing of nickel-based C276 microchannels with ultra-small bending radii according to claim 1, characterized in that, In step 4, the specific steps for removing the support structure and performing segmented annealing on the printed parts are as follows: Step 4.1: Cool the printed part to the range of 35~45℃, and then move it together with the substrate into the argon glove box. Use a continuous fiber laser to cut the support structure, and then use a sanding belt and a ceramic bead jet to remove the excess support structure in two stages. The surface roughness Ra is controlled between 5~7 µm. Step 4.2: Use a non-contact blue light scanner to remeasure the external dimensions of the printed part, and record the positions where the deviation exceeds ±30µm; Step 4.3: Perform three-stage annealing on the printed parts in a tube vacuum furnace; Step 4.4: Record the energy changes of the elastic wave release using an acoustic emission sensor. Use the total elastic wave energy recorded during the first complete thermal cycle as a baseline value. In subsequent heat treatments, start the cooling section when the accumulated elastic wave energy reaches 90% of the baseline value. The cooling rate of the cooling section is set to 8°C / min. -1 After the temperature cools to 400℃, it is then slowly reduced to 80℃ using a furnace-cooled method.

9. The method for selective melting additive manufacturing of nickel-based C276 microchannels with ultra-small bending radii according to claim 8, characterized in that, In step 4.3, when the printed parts are annealed in a three-stage process using a tube vacuum furnace, the three-stage annealing process is as follows: The first stage is the stress relief stage, in which the temperature inside the tubular vacuum furnace is increased by 8 °C / min. -1 The temperature is rapidly increased to a range of 640~660℃ and held at that temperature for 2 hours. The second stage is the recrystallization stage, in which the temperature inside the tube vacuum furnace is increased by 6 °C / min under the conditions of a hydrogen-nitrogen-argon mixed gas and a pH of 10 kPa. -1 The temperature was rapidly increased to a range of 1040–1060 °C and held at that temperature for 1 hour. The third stage is the precipitation control stage, in which the temperature inside the tube vacuum furnace is controlled at 3 °C / min under a pure argon atmosphere. -1 The temperature was reduced from 1040~1060 ℃ to 860~880 ℃ at a rate of 4 h, and then kept at 860~880 ℃ for 4 h.

10. The method for selective melting additive manufacturing of nickel-based C276 microchannels with ultra-small bending radii according to claim 1, characterized in that, Step 5, the specific steps for roughening the inner wall of the printed part are as follows: Step 5.1: Immerse the printed part in a chemical polishing solution composed of HF, HNO3, and deionized water, with volume fractions of HF, HNO3, and deionized water of 5%, 15%, and 80%, respectively. Step 5.2: After ultrasonically stirring in the chemical polishing solution for 30 seconds, the printed part is taken out and then rinsed with deionized water and anhydrous ethanol in sequence, and then dried with 80 ℃ hot air. Step 5.3 involves curing the passive film on the surface at a low temperature of 400 ℃ for 4 h, which precipitates fine carbides to achieve precipitation strengthening.

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