A laser powder bed additive manufacturing method and equipment

Abstract

This invention discloses a laser powder bed additive manufacturing method and equipment. The laser powder bed additive manufacturing method includes: laying powder material on a substrate in a forming chamber; purging the forming chamber; scanning and printing on the powder material according to a preset laser scanning path, melting the powder material along the preset laser scanning path; wherein the preset laser scanning path includes moving in a first direction while oscillating in a second direction, the first direction intersecting the second direction; after printing, annealing and cutting the molten powder material to obtain a part. This invention can effectively change the internal flow state of the molten pool, reduce the formation of internal defects in the part, and improve the efficiency of laser scanning printing.

Description

Technical Field

[0001] The present invention relates to the field of additive manufacturing, and in particular to a laser powder bed additive manufacturing method and equipment. Background Technology

[0002] Laser Powder Bed Fusion (LPBF) is a typical metal additive manufacturing technology that enables the integrated forming of complex structural parts and has broad application prospects in aerospace, energy and high-end equipment manufacturing.

[0003] However, in practical engineering applications, existing LPBF processes generally suffer from a contradiction between low forming efficiency and difficulty in consistently ensuring forming quality. In traditional LPBF processes, when using a smaller melt pool size for layer-by-layer melting and stacking, the amount of material melted and deposited per unit time is limited. Coupled with limitations in scanning spacing and layer thickness, the overall forming efficiency is low, making it difficult to meet the engineering manufacturing requirements of large-size, complex structural parts. Furthermore, the cooling and solidification process of a large melt pool is unstable, easily introducing significant residual stress and deformation, leading to fluctuations in the mechanical properties of the parts and a decline in surface quality. Therefore, existing technologies often face the contradiction between melt pool instability and increased defect levels when trying to improve melt pool size and scanning speed, making it difficult to balance efficiency and quality. Summary of the Invention

[0004] This invention provides a laser powder bed additive manufacturing method and equipment to effectively change the internal flow state of the molten pool, reduce the formation of internal defects in parts, and improve laser scanning printing efficiency.

[0005] In a first aspect, embodiments of the present invention provide a laser powder bed additive manufacturing method, the laser powder bed additive manufacturing method comprising: Powder material is laid on the substrate inside the molding chamber; The forming chamber is then purged with air. The powder material is scanned and printed according to a preset laser scanning path, and the powder material on the preset laser scanning path is melted; wherein, the preset laser scanning path includes moving in a first direction and oscillating in a second direction, and the first direction and the second direction intersect; After printing, the molten powder material is annealed and cut to obtain the part.

[0006] Optionally, the swinging mode includes sine scanning, cosine scanning, circular scanning, elliptical scanning, horizontal figure-eight scanning, and vertical figure-eight scanning, wherein the first direction is perpendicular to the second direction.

[0007] Furthermore, the sinusoidal scan and the cosine scan satisfy the following: ; ; The circular scan and the elliptical scan satisfy the following: ; ; The vertical figure-eight scanning satisfies: ; ; The horizontal figure-eight scan satisfies: ; ; in, The scanning speed of the laser along the first direction is denoted as . The scanning speed of the laser along the second direction is denoted as . To preset the laser scanning speed, The amplitude of the swing. For frequency, For time.

[0008] Furthermore, the step of scanning and printing on the powder material according to a preset laser scanning path, and melting the powder material along the preset laser scanning path, includes: During the printing process, the molten pool parameters of the powder material are acquired; The gas parameters in the forming chamber are adjusted according to the material type of the powder material and the parameters of the molten pool, so that the temperature of the molten pool of the powder material is within a preset temperature range and the oxygen content in the forming chamber is within a preset oxygen content range.

[0009] Furthermore, the forming chamber is purged, including: The forming chamber is repeatedly evacuated and filled with inert gas until the oxygen content in the forming chamber is less than the preset oxygen content.

[0010] Furthermore, the molten powder material is annealed and cut to obtain parts, including: The molten powder material is annealed; The part is obtained by cutting along the contact surface between the powder material and the substrate.

[0011] Furthermore, each type of powder material has a corresponding preset thickness, laser power, oscillation amplitude, frequency, and scanning speed; After obtaining the part, the process also includes: Extract the microscopic parameters from the part; The preset thickness, laser power, oscillation amplitude, frequency, and scanning speed of the powder material are optimized based on the microscopic parameters.

[0012] Furthermore, the microscopic parameters of the part are extracted, including: The microscopic parameters of the part are obtained by means of a microscope, and the microscopic parameters include at least one of the following: internal pores of the molten pool, unfused areas, microcracks, grain structure, and molten pool size.

[0013] Furthermore, the optimization of the preset thickness, laser power, oscillation amplitude, frequency, and scanning speed of the powder material based on the microscopic parameters, wherein the preset thickness is the thickness of the powder material laid on the substrate, including: The stability value of the molten pool is evaluated based on the microscopic parameters; wherein, the fewer the number of defects in the molten pool among the microscopic parameters, the greater the stability value of the molten pool. The preset thickness, laser power, oscillation amplitude, frequency, and scanning speed of the powder material are adjusted multiple times to obtain the corresponding molten pool stability values. The preset thickness of the powder material, laser power, oscillation amplitude, frequency, and scanning speed corresponding to the maximum value of the molten pool stability are taken as the optimal values.

[0014] Secondly, embodiments of the present invention also provide a laser powder bed additive manufacturing apparatus, wherein the laser powder bed additive manufacturing apparatus performs laser powder bed additive manufacturing according to the laser powder bed additive manufacturing method described in any embodiment of the present invention.

[0015] This invention provides a laser powder bed additive manufacturing method and equipment. The method involves laying powder material on a substrate within a forming chamber, purging the chamber to ensure the environment meets printing requirements, and then scanning the powder material along a preset laser scanning path to melt the powder material. After printing, the molten powder material is annealed and cut to obtain the part. Because the preset laser scanning path involves movement in a first direction and oscillation in a second direction, a wider powder band can be melted in a single laser scan, forming a large molten pool, thus improving laser scanning printing efficiency. Furthermore, the oscillation in the second direction while moving in the first direction effectively alters the flow state within the molten pool, allowing for the full removal of pores, inclusions, and unfused areas, reducing internal defects in the part. This significantly increases the melting range per unit time while reducing defects such as voids, unfused areas, and hot cracks, achieving a balance between high efficiency and high quality. Attached Figure Description

[0016] Figure 1 A flowchart of a laser powder bed additive manufacturing method provided in an embodiment of the present invention; Figure 2 A schematic diagram of the path for sinusoidal / cosine scanning provided in an embodiment of the present invention; Figure 3 A schematic diagram of circular / elliptical scanning provided in an embodiment of the present invention; Figure 4 A schematic diagram of the path for vertical figure-eight scanning provided in an embodiment of the present invention; Figure 5 A schematic diagram of a horizontal figure-eight scanning method provided in an embodiment of the present invention; Figure 6 A flowchart of another laser powder bed additive manufacturing method provided in an embodiment of the present invention; Figure 7 A flowchart for optimizing parameters in a laser powder bed additive manufacturing process, provided as an embodiment of the present invention; Figure 8 A flowchart illustrating another laser powder bed additive manufacturing method provided in this embodiment of the invention; Figure 9 This is a comparison diagram of a large molten pool and a small molten pool provided for an embodiment of the present invention. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0018] In traditional LPBF (Laser-to-Boiler) processes, a small melt pool size is typically used for layer-by-layer melting and stacking to ensure concentrated laser energy and full material fusion, thereby achieving high part density and surface quality. However, this small melt pool forming mode results in a limited amount of material melted and deposited per unit time. In addition, the scanning interval and layer thickness are limited, leading to low overall forming efficiency, making it difficult to meet the engineering manufacturing needs of large-size, complex-structured parts.

[0019] To improve forming efficiency, existing technologies attempt to create wide or large molten pools by increasing laser power or spot size, thereby increasing the width of a single melting pass and improving melting efficiency per unit time. However, wide or large molten pool modes have significant limitations in practical applications: due to the increased molten pool size, the temperature gradient within the melting region becomes more complex, and the energy distribution between the edge and center of the molten pool is uneven, easily leading to defects such as voids, incomplete fusion, segregation, and hot cracks; simultaneously, the cooling and solidification process of a large molten pool is unstable, easily introducing large residual stresses and deformations, resulting in fluctuations in the mechanical properties of the parts and a decrease in surface quality. Therefore, simply relying on a wide molten pool strategy to improve efficiency often comes with significant quality losses, making it difficult to meet the stringent requirements of high-density, high-reliability parts in critical fields such as aerospace.

[0020] In summary, existing technologies often face the contradiction between molten pool instability and increased defect levels when trying to improve molten pool size and scanning speed, making it difficult to balance efficiency and quality.

[0021] To address the aforementioned problems, this invention provides a laser powder bed additive manufacturing method. By using a laser to perform oscillating scanning printing along a preset laser scanning path, the size of the molten pool is increased and the scanning efficiency is improved. This effectively controls the molten pool morphology and thermal gradient changes, thereby significantly increasing the melting range per unit time while reducing defects such as voids, incomplete fusion, and hot cracks. This achieves a balance between high efficiency and high quality, solving the key problem in the prior art where wide molten pool forming efficiency is high but quality is difficult to guarantee. Figure 1 A flowchart of a laser powder bed additive manufacturing method provided in an embodiment of the present invention is shown below. Figure 1 As shown, the laser powder bed additive manufacturing method includes: S110. Powder material is laid on the substrate inside the molding chamber.

[0022] The forming chamber is a sealed printing space in the metal powder bed additive manufacturing equipment. All laser powder bed additive manufacturing and printing operations are carried out in the forming chamber. The powder material includes, but is not limited to, titanium alloys, aluminum alloys, high-temperature alloys, stainless steel and other metal materials and their derivatives. The substrate, as a carrier platform, provides a flat and stable surface for the laying and melting of powder materials. On the other hand, it can fix the growing parts during the printing process to prevent the parts from shifting or warping.

[0023] S120. Wash the forming chamber with air.

[0024] Specifically, the gas environment inside the forming chamber needs to be controlled before printing. By purging the forming chamber, the oxygen content inside the chamber is reduced to the range required for printing, thereby preventing the powder material from oxidizing and locally ablated. The purging process can be carried out by evacuating and filling with high-purity inert gas (such as argon or nitrogen) to form an oxygen-free and moisture-free protective atmosphere, in order to further prevent the powder material from oxidizing under high temperature conditions.

[0025] S130. Scan and print on the powder material according to the preset laser scanning path, and melt the powder material on the preset laser scanning path; wherein, the preset laser scanning path includes moving in the first direction and swinging in the second direction at the same time, and the first direction and the second direction intersect.

[0026] Specifically, to balance increasing the molten pool size and improving scanning efficiency, a preset laser scanning path needs to be designed based on the original linear scanning path of the part before laser printing. This path moves along a first direction while simultaneously applying a regular oscillation in a second direction. During printing, the laser scans the powder material along the preset laser scanning path at a preset speed, melting the powder material along the path. On one hand, the laser's movement in the first direction and oscillation in the second direction allows for the melting of a wider powder band in a single scan, forming a large molten pool and improving scanning efficiency. Furthermore, a high-power laser can be selected to form a wide or large molten pool, further enhancing scanning efficiency. On the other hand, the regular oscillation in the second direction creates micro-area stirring, ensuring thorough mixing within the molten pool. This flow helps to fully remove pores, inclusions, and unfused areas, reducing internal defects and solving the technical problem in existing technologies where high molten pool forming efficiency is achieved but quality is difficult to guarantee.

[0027] S140. After printing, the molten powder material is annealed and cut to obtain the part.

[0028] Specifically, after printing along the preset laser scanning path, the molten powder material is annealed and cut to peel the part off the substrate, obtaining a complete part product. This embodiment of the invention uses a swing scanning method during laser printing. By moving in the first direction while simultaneously swinging and scanning in the second direction, a large molten pool is formed, significantly increasing the material deposition per unit time and achieving high-efficiency additive manufacturing. Simultaneously, the large molten pool plays a supporting role in controlling porosity and incomplete fusion defects during the stirring of the micro-region molten pool, ensuring that the part maintains a certain degree of density and mechanical uniformity under high-efficiency forming conditions. This significantly improves manufacturing efficiency per unit time while effectively reducing metallurgical defects in the molten pool micro-region, achieving high-efficiency, high-quality part forming and providing a reliable additive manufacturing technology solution for aerospace, energy, and high-end equipment manufacturing fields.

[0029] This invention provides a laser powder bed additive manufacturing method. The method involves laying powder material on a substrate within a forming chamber, purging the chamber to ensure the environment meets printing requirements, scanning the powder material along a preset laser scanning path, melting the powder material along the path, and then annealing and cutting the molten powder material to obtain a part. Because the preset laser scanning path involves movement in a first direction and oscillation in a second direction, with the first and second directions intersecting, the flow state within the molten pool can be effectively altered. This allows for the full removal of pores, inclusions, and unfused areas, reducing internal defects in the part. When this method is applied to bed additive manufacturing using a large molten pool, it achieves a balance between high efficiency and high quality, solving the technical problem in existing technologies where high molten pool forming efficiency is difficult to guarantee quality.

[0030] In some embodiments of the present invention, the swinging mode includes sine scanning, cosine scanning, circular scanning, elliptical scanning, horizontal figure-eight scanning, and vertical figure-eight scanning, with the first direction perpendicular to the second direction.

[0031] Specifically, the oscillation mode of the laser along the preset laser scanning path includes, but is not limited to, sinusoidal scanning, cosine scanning, circular scanning, elliptical scanning, horizontal figure-eight scanning, and vertical figure-eight scanning. By further adjusting the oscillation amplitude, frequency, and scanning speed, the morphology of the molten pool can be optimized to ensure melting uniformity and thermal gradient stability.

[0032] In embodiments of the present invention, sinusoidal scanning and cosine scanning satisfy the following: ; ; Circular and elliptical scans satisfy the following: ; ; Vertical figure-eight scanning satisfies: ; ; Horizontal figure-eight scan satisfies: ; ; in, Let be the scanning speed of the laser along the first direction. Let be the scanning speed of the laser along the second direction. To preset the laser scanning speed, The amplitude of the swing. For frequency, For time.

[0033] Specifically, preset laser scanning speed Specifically, this refers to the laser scanning speed under traditional linear scanning. The first direction is the x-axis, which is the scanning direction of the laser under traditional linear scanning. The second direction is the y-axis, which is perpendicular to the traditional laser scanning direction. R represents the oscillation amplitude, or the amplitude of the oscillation. This refers to the frequency, i.e., the oscillation frequency, which is also the reciprocal of the period. The scanning speed along the first direction for sinusoidal and cosine scans. Equal to preset laser scanning speed This is equal to the laser scanning speed under the traditional linear scanning method, thus increasing the laser scanning speed along the second direction compared to the traditional linear scanning method. This improves scanning efficiency and molten pool size. Circular scanning, elliptical scanning, horizontal figure-eight scanning, and vertical figure-eight scanning, based on the laser scanning speed of traditional linear scanning methods, reset the scanning speed along the first direction. Second direction scanning speed This is to further improve scanning efficiency and achieve regular oscillating scanning.

[0034] Figure 2 This is a schematic diagram of the sine / cosine scanning path provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of circular / elliptical scanning provided in an embodiment of the present invention. Figure 4 This is a schematic diagram of the path for a vertical figure-eight scanning method provided in an embodiment of the present invention. Figure 5 This is a schematic diagram of a horizontal figure-eight scanning method provided in an embodiment of the present invention, as shown below. Figure 2-5As shown, the laser moves along the preset laser scanning path while simultaneously applying regular oscillations in the second direction Y. This allows for the selection of a high-power laser to form a wide or large molten pool during printing, improving forming efficiency. Furthermore, the molten pool disturbance generated by the oscillation acts as a micro-area stirring mechanism, ensuring thorough stirring within the molten pool micro-area. The flow of the molten pool helps to fully remove pores, inclusions, and unfused areas, reducing the formation of internal defects in the parts and achieving a balance between high efficiency and high quality.

[0035] This invention utilizes various oscillating scanning methods to form a large molten pool, significantly increasing the material deposition rate per unit time and achieving high-efficiency additive manufacturing. Simultaneously, the large molten pool plays a supporting role in controlling porosity and incomplete fusion defects during the stirring of the micro-region molten pool, ensuring that the part maintains a certain degree of density and mechanical uniformity even under high-efficiency forming conditions.

[0036] In some embodiments of the present invention, a laser scans and prints on a powder material according to a preset laser scanning path and a preset oscillation pattern, and melts the powder material on the preset laser scanning path according to a preset oscillation amplitude, frequency, and scanning speed, including: During the printing process, the molten pool parameters of the powder material are acquired; the gas parameters in the forming chamber are adjusted according to the material type of the powder material and the molten pool parameters to ensure that the molten pool temperature of the powder material is within a preset temperature range and the oxygen content in the forming chamber is within a preset oxygen content range.

[0037] Specifically, the molten pool parameters for powder materials can be the molten pool temperature. When the molten pool temperature is within a preset range and the oxygen content in the forming chamber is within a preset oxygen content range, fewer defects are generated in the molten pool, and the molten pool is stable. During the printing process, the gas parameters in the forming chamber can be adjusted according to the type of powder material and the molten pool parameters to ensure that the molten pool temperature and oxygen content of the powder material are within a controllable range. This improves the density and mechanical uniformity of the formed parts, ensures the stable formation of a large molten pool, improves printing efficiency, and also has an auxiliary effect on the density of the parts.

[0038] This invention also provides another laser powder bed additive manufacturing method. Figure 6 A flowchart of another laser powder bed additive manufacturing method provided in an embodiment of the present invention is shown below. Figure 6 As shown, it includes: S210. Powder material is laid on the substrate inside the molding chamber.

[0039] In some embodiments of the present invention, before laying the powder material, a printing substrate needs to be installed in the forming chamber. Furthermore, the flatness of the substrate is required to be ≤0.03 mm to improve the accuracy of laser printing. After the substrate is installed, the gap between the substrates is checked using a feeler gauge, preferably a 0.04 mm feeler gauge. If a slight damping sensation is felt during the check, it indicates that the substrate installation and positioning meet the requirements, ensuring the uniformity of the printed layer thickness and the forming accuracy of the part. Subsequently, metal powder is uniformly laid on the substrate. The powder material includes, but is not limited to, titanium alloys, aluminum alloys, high-temperature alloys, stainless steel, and other metal materials and their derivatives. Furthermore, by optimizing the powder layer thickness and distribution uniformity, it can be ensured that each layer of powder is fully melted during the forming process, reducing the probability of localized voids and incomplete fusion defects.

[0040] S220. Perform vacuuming and inert gas filling operations on the forming chamber until the oxygen content in the forming chamber is less than the preset oxygen content.

[0041] Specifically, before printing, to thoroughly purge the forming chamber, the chamber can be evacuated and filled with inert gas in a cyclical manner to reduce the oxygen content until it is lower than a preset level, thereby preventing powder oxidation and localized ablation. After purge is complete, the laser powder bed additive manufacturing equipment containing the forming chamber can automatically output laser and start the printing program to scan and print on the powder material.

[0042] S230. Scan and print on the powder material according to the preset laser scanning path, and melt the powder material on the preset laser scanning path; wherein, the preset laser scanning path includes moving in the first direction and swinging in the second direction at the same time, and the first direction and the second direction intersect.

[0043] Specifically, in this embodiment of the invention, the laser scanning path and printing parameters can be further designed based on the original linear scanning path. While moving the scanning path along the first direction, a regular oscillation is applied in the second direction to fully stir the micro-regions of the molten pool. Through oscillating scanning, the internal flow state of the molten pool can be effectively changed, allowing pores, inclusions, and locally unfused areas to be fully discharged, reducing the formation of internal defects. The oscillation method includes, but is not limited to, the sinusoidal, cosine, elliptical, horizontal figure-eight, and vertical figure-eight scanning paths in this embodiment of the invention. Furthermore, by adjusting the oscillation amplitude, frequency, and scanning speed, the molten pool morphology can be optimized, further ensuring melting uniformity and thermal gradient stability.

[0044] S240. After printing, the molten powder material is annealed.

[0045] Specifically, after the powder material on the preset laser scanning path is melted and printed by laser, the molten powder material is subjected to stress-relieving annealing treatment, for example, it can be held at 800℃ for 2 hours to release the residual stress in the molten powder material and prevent the part from being significantly deformed.

[0046] S250. Cut along the contact surface between the powder material and the substrate to obtain the part.

[0047] After annealing, the parts are wire-cut along the upper surface of the substrate. Local heating should be avoided during the cutting process to ensure the structural integrity and surface quality of the parts. By optimizing the printing parameters and cutting process, defects caused by microcracks and thermal stress can be reduced.

[0048] Each type of powder material has a corresponding preset thickness, laser power, oscillation amplitude, frequency and scanning speed. The preset thickness is the thickness of the powder material laid on the substrate.

[0049] Specifically, since different powder materials have different properties, the preset thickness, laser power, oscillation amplitude, frequency and scanning speed can be different for different powder materials. This allows each powder material to produce high-quality parts when laser printing is performed according to the corresponding preset thickness, laser power, oscillation amplitude, frequency and scanning speed.

[0050] After obtaining the parts, the parameters in the laser printing manufacturing process can be optimized. By adjusting the oscillation amplitude, frequency and scanning speed, the morphology of the molten pool can be optimized, thereby further ensuring the uniformity of melting and the stability of the thermal gradient. Figure 7 A flowchart for optimizing parameters in a laser powder bed additive manufacturing process, as provided in an embodiment of the present invention, is shown below. Figure 7 As shown, after obtaining the part, it includes: S310, Extract the microscopic parameters from the part.

[0051] Specifically, systematic metallographic analysis and microstructure observation can be performed on the cross-section of the part, and quantitative and qualitative analysis can be conducted on the internal pores, unfused areas, microcracks, grain behavior and molten pool size of the molten pool. The characteristics of the molten pool and the behavior of defects can be observed to evaluate the control effect of metallurgical defects during the forming process and verify the role of combining oscillating scanning and large molten pool in reducing defects.

[0052] In this embodiment of the invention, extracting microscopic parameters from the part includes: Microscopic parameters of the part are obtained using a microscope. These parameters include at least one of the following: internal pores of the molten pool, unfused areas, microcracks, grain structure, and molten pool size. The preset thickness refers to the thickness of the powder material deposited on the substrate. Specifically, microscopic parameters include at least one of the following: internal pores in the molten pool, unfused areas, microcracks, grain structure, and molten pool size. These are determined through systematic metallographic analysis and microstructural observation of the part's cross-section. Specifically, methods such as optical microscopy and scanning electron microscopy (SEM) are used to quantitatively and qualitatively analyze internal pores in the molten pool, unfused areas, microcracks, grain behavior, and molten pool size. Taking high-temperature alloys and titanium alloys as examples of powder materials, solutions prepared with 5 ml HNO3, 120 ml HCl, 50 ml H2O, and 25 g FeCl3 can be used to etch high-temperature alloy samples, while solutions prepared with 1% HF, 2.5% HNO3, and 96.5% H2O can be used to etch titanium alloy samples. The characteristics of the molten pool and defect behavior are observed to obtain the microscopic parameters. By analyzing samples with different powder materials, different molten pool sizes, and different oscillation parameters, the control effect of metallurgical defects during the forming process can be evaluated, and the role of combining oscillation scanning with a large molten pool in reducing defects can be verified.

[0053] S320: Optimize the preset thickness, laser power, oscillation amplitude, frequency and scanning speed of the powder material based on microscopic parameters.

[0054] By repeatedly optimizing the corresponding preset thickness, laser power, oscillation amplitude, frequency, and scanning speed, and using microscopic parameters as reference indicators, the stability of the molten pool is evaluated. The parameters corresponding to the highest molten pool stability are selected from the repeatedly optimized preset thickness, laser power, oscillation amplitude, frequency, and scanning speed as the optimal parameters, thereby further improving the stability of the molten pool under large molten pool conditions. This embodiment of the invention, through optimized parameter control, can further ensure the stability of the molten pool, melting uniformity, and controllable thermal gradient under large molten pool conditions, thereby maintaining the compactness, uniformity of mechanical properties, and surface quality of the parts under high-efficiency forming conditions.

[0055] In some embodiments of the present invention, the preset thickness, laser power, oscillation amplitude, frequency, and scanning speed of the powder material are optimized based on microscopic parameters, specifically including: S410. Evaluate the molten pool stability value based on microscopic parameters; where the fewer the number of defects in the molten pool among the microscopic parameters, the greater the molten pool stability value.

[0056] Specifically, the stability of the molten pool can be evaluated based on microscopic parameters. For example, higher levels of internal porosity, unfused areas, and microcracks within the molten pool indicate more defects and lower molten pool stability. Conversely, larger molten pool sizes result in higher stability. This allows for the quantification of molten pool stability. It should be noted that the actual evaluation of molten pool stability is not limited to the above process; evaluation indicators can be adaptively set to determine the molten pool stability value. By qualitatively and quantitatively analyzing internal porosity, unfused areas, microcracks, and molten pool size to evaluate molten pool stability, the defect control effect of a large molten pool formed by oscillating scanning under high-efficiency conditions can be verified.

[0057] S420. The preset thickness, laser power, oscillation amplitude, frequency and scanning speed of the powder material are adjusted multiple times to obtain the corresponding molten pool stability value.

[0058] Specifically, the preset thickness, laser power, oscillation amplitude, frequency, and scanning speed of the powder material are adjusted multiple times. Then, the adjusted preset thickness, laser power, oscillation amplitude, frequency, and scanning speed are used to form the formal part using experimentally verified or simulated optimized printing parameters. Finally, the melt pool stability values ​​of the obtained parts are evaluated to obtain multiple adjusted melt pool stability values ​​for the parts.

[0059] S430: The preset thickness, laser power, oscillation amplitude, frequency, and scanning speed of the powder material corresponding to the maximum molten pool stability value are taken as the optimal values.

[0060] Specifically, the maximum value of the molten pool stability values ​​corresponding to multiple adjusted parts is selected as the maximum molten pool stability value. The preset thickness, laser power, oscillation amplitude, frequency and scanning speed of the powder material corresponding to the maximum molten pool stability value are taken as the optimal values ​​to further ensure the stability of the large molten pool and achieve high-efficiency forming.

[0061] Figure 8 A flowchart of another laser powder bed additive manufacturing method provided in this embodiment of the invention is shown below. Figure 8 As shown, it includes: S1, Substrate mounting and powder coating.

[0062] In the powder bed additive manufacturing equipment, the printing substrate is installed in the forming chamber, requiring a substrate flatness of ≤0.03mm. After installation, the installation gap is checked using a 0.04mm feeler gauge to ensure accurate substrate positioning. Subsequently, metal powder, including titanium alloys, aluminum alloys, high-temperature alloys, stainless steel, and their derivatives, is uniformly deposited on the substrate. By optimizing the powder deposition thickness and uniformity, the large molten pool is ensured to fully melt the material during printing, improving the material deposition efficiency per unit time.

[0063] S2, Scanning path planning and swing design.

[0064] Based on the original linear scanning path, by pre-designing the laser scanning path and printing parameters, the scanning path is moved along the first direction while a regular oscillation is applied in the second direction, causing thorough stirring of the micro-area molten pool. The oscillation patterns include sinusoidal, cosine, elliptical, and figure-eight shapes, but are not limited to these. By adjusting the oscillation amplitude, frequency, and scanning speed, a stable formation and continuous movement of a large molten pool are achieved, significantly increasing the material deposition per unit time and realizing high-efficiency printing. The molten pool disturbance also helps reduce porosity and incomplete fusion defects, further improving printing efficiency.

[0065] S3, Forming chamber washing and atmosphere control.

[0066] Before printing, the forming chamber is thoroughly purged to ensure the oxygen content meets the material printing requirements. After purge, the equipment starts laser output and executes the printing program. During printing, the atmosphere parameters can be adjusted according to the material type and molten pool size to ensure stable formation of a large molten pool, improve printing efficiency, and simultaneously contribute to the densification of the part.

[0067] S4. Part printing and post-processing.

[0068] By scanning and printing on powder material according to a preset laser scanning path, such as a horizontal figure-eight pattern, and combining this with an oscillating strategy to form a large molten pool, the amount of material deposited per unit time is significantly increased. After printing, stress-relief annealing can be performed at 800℃ for 2 hours, followed by wire cutting along the substrate surface to obtain the part. Local overheating is avoided during the cutting process to maintain the integrity of the part.

[0069] S5. Sample analysis and defect observation.

[0070] Metallographic analysis and microstructural observation of the printed sample cross-section were performed. The size of the pores, unfused areas, microcracks and molten pool were qualitatively and quantitatively analyzed using optical microscopes and scanning electron microscopes (SEM) to extract the microscopic parameters of the parts.

[0071] S6. Forming parts based on optimized parameters.

[0072] Specifically, by repeatedly optimizing the corresponding preset thickness, laser power, oscillation amplitude, frequency, and scanning speed, and using microscopic parameters as reference indicators, the stability of the molten pool is evaluated. Thus, the parameter with the highest molten pool stability is selected from the preset thickness, laser power, oscillation amplitude, frequency, and scanning speed that have been optimized and adjusted multiple times as the optimal parameter, so as to further improve the stability of the molten pool under large molten pool conditions and achieve high-efficiency forming.

[0073] Figure 9 A comparison diagram of a large molten pool and a small molten pool provided for an embodiment of the present invention, as shown below. Figure 9 As shown, the large molten pool A is formed during the oscillating scanning of powder material using the laser powder bed additive manufacturing method in this embodiment of the invention, while the small molten pool B is formed during laser scanning using conventional processes. The width of the large molten pool A is 510 μm and the height is 240 μm, while the width of the small molten pool B is 136 μm, with similar height and width. The large molten pool A is larger in size and has a higher melting efficiency than the small molten pool B. Therefore, the laser powder bed additive manufacturing method in this embodiment of the invention can greatly improve the melting efficiency of powder material per unit time and reduce defects such as voids, lack of fusion, segregation, and hot cracks in the large molten pool, thereby improving the forming quality of the parts. Furthermore, existing technologies attempt to form wide or large molten pools by increasing laser power or increasing the spot size. However, the laser powder bed additive manufacturing method of this invention can form wide or large molten pools without increasing laser power or increasing the spot size. It can form large molten pools simply by presetting the laser scanning path without changing the laser devices in the existing laser powder bed additive manufacturing equipment. This reduces equipment replacement costs and can balance the high efficiency and high quality of the laser powder bed melting process.

[0074] This invention provides a laser powder bed additive manufacturing method that effectively overcomes the limitations of limited molten pool size and low deposition rate per unit time under traditional linear scanning paths. By applying regular oscillations within the scanning path, the molten pool is thoroughly stirred, allowing for the complete removal of pores and inclusions. Simultaneously, by combining a large molten pool strategy with optimized printing parameters, the molten pool temperature and thermal gradient are effectively controlled, extending the solidification time per unit length and enhancing the remelting effect during path return. This effectively reduces incomplete fusion and microcrack defects, achieving the goals of high density, high mechanical properties, and high surface quality in additive parts, while significantly improving overall forming efficiency.

[0075] This invention also provides a laser powder bed additive manufacturing apparatus, which performs laser powder bed additive manufacturing according to the laser powder bed additive manufacturing method in any embodiment of this invention.

[0076] Specifically, the laser powder bed additive manufacturing equipment provided in this embodiment of the invention includes a forming chamber, and can perform laser powder bed additive manufacturing using the laser powder bed additive manufacturing method proposed in any of the above embodiments. It has the beneficial effects of the laser powder bed additive manufacturing method proposed in the above embodiments, which will not be repeated here.

[0077] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A laser powder bed additive manufacturing method, characterized by, The laser powder bed additive manufacturing method comprises: laying a powder material on a substrate in a forming cabin; gas washing is performed on the forming cabin; scanning and printing on the powder material according to a preset laser scanning path, and melting the powder material on the preset laser scanning path; wherein the preset laser scanning path comprises swinging in a second direction while moving in a first direction, and the first direction intersects the second direction; after printing is completed, annealing and cutting treatment are performed on the melted powder material to obtain a part.

2. The laser powder bed additive manufacturing method of claim 1, wherein, The swinging mode comprises sinusoidal scanning, cosine scanning, circular scanning, elliptical scanning, horizontal eight-shaped scanning and vertical eight-shaped scanning, and the first direction is perpendicular to the second direction.

3. The laser powder bed additive manufacturing method of claim 2, wherein, The sinusoidal scanning and the cosine scanning satisfy: ； ； The circular scanning and the elliptical scanning satisfy: ； ； The vertical eight-shaped scanning satisfies: ； ； The horizontal eight-shaped scanning satisfies: ； ； wherein, is a scanning speed of the laser along the first direction, is a scanning speed of the laser along the second direction, is a preset laser scanning speed, is an oscillation amplitude, is a frequency, is a time.

4. The laser powder bed additive manufacturing method of claim 1, wherein, The scanning and printing on the powder material according to the preset laser scanning path, and melting the powder material on the preset laser scanning path, comprises: during printing, a molten pool parameter of the powder material is acquired; according to the material type of the powder material and the molten pool parameter, a gas parameter in the forming cabin is adjusted, so that the molten pool temperature of the powder material is in a preset temperature range, and the oxygen content in the forming cabin is in a preset oxygen content range.

5. The laser powder bed additive manufacturing method of claim 1, wherein, The gas washing performed on the forming cabin comprises: the forming cabin is subjected to the operations of vacuumizing and filling with inert gas in a cycle until the oxygen content in the forming cabin is less than a preset oxygen content.

6. The laser powder bed additive manufacturing method of claim 1, wherein, The annealing and cutting treatment performed on the melted powder material to obtain a part comprises: annealing is performed on the melted powder material; cutting is performed along the contact surface of the powder material and the substrate to obtain the part.

7. The laser powder bed additive manufacturing method of claim 1, wherein, The powder material of each material has a corresponding preset thickness, laser power, swinging amplitude, frequency and scanning speed, wherein the preset thickness is the laying thickness of the powder material on the substrate; after the part is obtained, the method further comprises: extracting a micro parameter in the part; optimizing the preset thickness, laser power, swinging amplitude, frequency and scanning speed corresponding to the powder material according to the micro parameter.

8. The laser powder bed additive manufacturing method of claim 7, wherein, The extraction of the micro parameter in the part comprises: the micro parameter in the part is acquired through a microscope, and the micro parameter comprises at least one of a molten pool internal hole, an unmelted area, a micro crack, a grain structure and a molten pool size.

9. The laser powder bed additive manufacturing method of claim 7, wherein, The optimization of the preset thickness, laser power, swinging amplitude, frequency and scanning speed corresponding to the powder material based on the micro parameter comprises: evaluating a molten pool stability value based on the micro parameter; wherein the fewer the number of defects of the molten pool in the micro parameter, the greater the molten pool stability value; the preset thickness, laser power, swinging amplitude, frequency and scanning speed corresponding to the powder material are adjusted multiple times, and the corresponding molten pool stability value is obtained; The preset thickness, laser power, the swing amplitude, the frequency and the scanning speed corresponding to the powder material corresponding to the maximum molten pool stability value are taken as optimal values.

10. A laser powder bed additive manufacturing apparatus, characterized by, The laser powder bed additive manufacturing equipment performs laser powder bed additive manufacturing according to the laser powder bed additive manufacturing method in any one of claims 1-9.

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