Method of stabilizing a powder bed laser fusion process

Abstract

The application provides a method for stabilizing a powder bed laser melting process, belonging to the technical field of additive manufacturing, comprising determining input energy of a single laser scanning; determining a particle size distribution of a powder bed; determining median particle sizes of powders of each particle size layer of the powder bed according to the particle size distribution of the powder bed; preparing required powders of each level according to the particle size distribution of the powder bed and the median particle sizes of the powders of each particle size layer; and layer by layer laying the powders of each layer on a forming substrate of a laser powder bed melting device according to the particle size distribution and the median particle sizes of the powders of each layer to build the powder bed. The application solves the problems of laser energy transmission attenuation and uneven heat accumulation under the condition of large layer thickness. The high-efficiency forming and high-quality forming are realized under the condition of large layer thickness, the high precision and excellent performance possessed by traditional thin layer printing are obtained while the high printing efficiency is maintained, and a feasible path is provided for the large-scale application of the laser powder bed melting technology in the manufacturing of large and complex metal components.

Description

Technical Field

[0001] This invention belongs to the technical field of additive manufacturing, and more specifically, relates to a method for stabilizing the laser melting process of powder bed. Background Technology

[0002] With the increasing demand for large and complex metal components in fields such as aerospace, medical devices, and mold making, additive manufacturing technology has demonstrated significant advantages due to its ability to create molds quickly and freely. Among these technologies, laser powder bed melting technology, with its extremely high forming accuracy and excellent part performance, has become an ideal solution for manufacturing such critical components.

[0003] Traditional laser powder bed melting technology typically employs thin powder layer thicknesses (e.g., 30-50 μm) to ensure forming accuracy. This results in low single-layer cladding, extremely low forming efficiency, long production cycles, and high costs, severely restricting its large-scale application in the manufacturing of large components. To overcome this bottleneck, increasing the powder bed thickness has become a direct way to improve forming efficiency—increasing the layer thickness can significantly increase the amount of powder deposited per layer, thereby effectively shortening the processing cycle and reducing manufacturing costs. However, increasing the layer thickness exacerbates the transmission attenuation of laser energy and uneven heat accumulation in the powder bed, making the dynamic behavior of the molten pool more complex and easily inducing serious defects such as incomplete fusion, spheroidization, and spattering. Ultimately, this leads to a decrease in the density of the formed parts, deterioration of surface quality, and degradation of mechanical properties. Therefore, how to achieve efficient and high-quality synergistic forming under large layer thickness conditions has become a key challenge that laser powder bed melting technology urgently needs to overcome. Summary of the Invention

[0004] The purpose of this invention is to provide a method for stabilizing the powder bed laser melting process, aiming to solve the problem of how to achieve efficient and high-quality synergistic forming under large layer thickness conditions.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: to provide a method for stabilizing the powder bed laser melting process, comprising: Determine the input energy for single-channel laser scanning; Determine the particle size distribution of the powder bed; The median particle size of the powder in each particle size layer of the powder bed is determined based on the particle size distribution of the powder bed. The required powders at each level are prepared based on the particle size distribution of the powder bed and the median particle size of the powders in each particle size layer. On the molding substrate of the laser powder bed melting equipment, each layer of powder is laid layer by layer according to the particle size distribution and the median particle size of each layer of powder to construct a powder bed. Under a protective atmosphere, a laser beam is used to scan and melt the powder bed; In-situ monitoring is performed during the melting process of the powder bed to analyze the melting process and obtain monitoring results; The quality of the melt channel obtained by melting the powder bed is analyzed to obtain the melt channel characterization results; Based on the monitoring results and the melt channel characterization results, the thickness of each layer of the powder bed is adjusted.

[0006] Preferably, determining the input energy for a single laser scan includes: Calculate the minimum heat required to melt a single-layer powder bed; The input energy for a single-channel laser scan is determined based on the minimum heat required to melt the single-layer powder bed.

[0007] Preferably, determining the particle size distribution of the powder bed includes: Determine the total number of layers in the powder bed; The particle size distribution is determined based on the total number of layers in the powder bed.

[0008] Preferably, determining the median particle size of the powder in each particle size layer of the powder bed based on the particle size distribution of the powder bed includes: The equivalent thermal conductivity of each particle size layer is calculated based on the particle size distribution of the powder bed. The median particle size of each particle size layer is calculated based on the equivalent thermal conductivity of each particle size layer.

[0009] Preferably, the thickness of the powder bed is 100-400 μm.

[0010] Preferably, the powder bed includes a bottom layer and an upper layer; the bottom layer has a thickness of 65%-70%, and the upper layer has a thickness of 30%-35%.

[0011] Preferably, the upper layer includes a middle layer and a top layer, the middle layer has a thickness of 19.5%-24.5%, the top layer has a thickness of 5.5%-15.5%, and the powder particle size of the bottom layer, the middle layer and the top layer gradually becomes coarser.

[0012] Preferably, the step of scanning and melting the powder bed using a laser beam under a protective atmosphere includes: The power of the laser beam is 200-500W, and the scanning speed of the laser beam is 300-800mm / s.

[0013] The beneficial effects of the method for stabilizing the laser melting process of a powder bed provided by this invention are as follows: Compared with the prior art, the method of this invention precisely sets the input energy of a single laser scan, allowing the laser energy supply to be precisely matched with the melting requirements of the powder bed. This avoids the problem of insufficient powder melting due to insufficient energy, and also prevents the instability of the molten pool caused by excessive energy, providing suitable energy support for the laser melting process. Scientifically defining the particle size distribution of the powder bed and clarifying the median particle size of each particle size layer provides precise parameters for the construction of the powder bed from the structural design level, allowing the combination of powders of different particle sizes to better meet the heat transfer requirements of laser melting, thus avoiding process defects caused by single-size powders from the source. Preparing powders at each level based on the particle size distribution and median particle size ensures that the particle size parameters of the powder are highly compatible with the structural design of the powder bed, allowing the physical properties of the powder to fully adapt to the energy transfer and heat conduction requirements of the melting process, laying a high-quality material foundation for the subsequent powder bed laying.

[0014] By layering powder onto a molding substrate to construct a powder bed, a tiered structure suitable for large-layer laser melting can be created, forming an ideal heat flow pattern with the heat transfer rate increasing from top to bottom, effectively controlling the transmission path of laser energy in the powder bed. This layer-by-layer laying method ensures uniform thickness and clear boundaries of each powder layer, allowing powders of different particle sizes to fully utilize their heat transfer and melting characteristics. It solves the problems of laser energy transmission attenuation and uneven heat accumulation under large-layer conditions, keeping the dynamic behavior of the molten pool under control. This achieves a synergy between efficient and high-quality forming under large-layer conditions, maintaining high printing efficiency while obtaining the high precision and excellent performance previously only available in thin-layer printing. The formed parts have higher density, smoother surface quality, and better microstructure properties. By actively controlling the heat transfer path of the powder bed and the dynamic behavior of the molten pool, the contradiction between powder spreading quality and melting quality in large-layer forming is resolved, providing a feasible path for the large-scale application of laser powder bed melting technology in the manufacturing of large and complex metal components. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A schematic diagram of the main steps of a method for stabilizing a powder bed laser melting process provided in an embodiment of the present invention; Figure 2 A schematic diagram of the powder bed constructed according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a conventional powder bed structure; Figure 4 This is a schematic diagram of the structure of a powder bed (coarse powder / fine powder: 1 / 3) constructed using an embodiment of the present invention; Figure 5 This is a schematic diagram of the melt channel morphology of a powder bed (coarse powder / fine powder: 1 / 3) constructed using an embodiment of the present invention; Figure 6 This is a schematic diagram of the melt channel morphology of a conventional powder bed. Figure 7 The image shows the powder bed (coarse powder / fine powder: 1 / 3) constructed using an embodiment of the present invention at t=26ms during the melting process; Figure 8 The image shows the powder bed (coarse powder / fine powder: 1 / 3) constructed using an embodiment of the present invention at t=48ms during the melting process; Figure 9 This is an image taken at t=25ms during the conventional powder bed melting process; Figure 10 This is an image taken at t=48ms during the conventional powder bed melting process; Figure 11 The EBSD (electron backscattering diffraction) grain orientation pattern of the powder bed (coarse powder / fine powder: 1 / 3) constructed using the embodiments of the present invention; Figure 12 This is a conventional powder bed EBSD (electron backscattering diffraction) grain orientation diagram; Figure 13 This is a comparison chart of stress-strain curves between a conventional powder bed and a powder bed constructed using an embodiment of the present invention. Detailed Implementation

[0017] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0019] It should be further noted that the accompanying drawings and embodiments of the present invention mainly describe the concept of the present invention. Based on this concept, some specific forms and arrangements of connection relationships, positional relationships, power mechanisms, power supply systems, hydraulic systems and control systems may not be fully described. However, under the premise that those skilled in the art understand the concept of the present invention, they can implement the above-mentioned specific forms and arrangements in a well-known manner.

[0020] When a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0021] In the description of this invention, "a plurality of" means two or more, and "several" means one or more, unless otherwise explicitly specified.

[0022] The directional terms "inner" and "outer" refer to the inner and outer contours of each component itself. The terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0023] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," and "above" are used here to describe the spatial positional relationship between a device or feature and other devices or features, as shown in the figure. It should be understood that spatial relative terms are intended to... The invention includes different orientations of the device in use or operation, in addition to those described in the figures. For example, if a device in the figures is inverted, a device described as "above" or "on top of" other devices or structures will be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below". The device may also be positioned in other different ways, and the spatial relative descriptions used herein are interpreted accordingly. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the invention, "a plurality of" means two or more, and "a number" means one or more, unless otherwise explicitly specified.

[0024] With the increasing demand for large and complex metal components in aerospace, medical devices, and mold-making industries, additive manufacturing technology has demonstrated significant advantages due to its mold-free and rapid free-form capabilities. Among these, laser powder bed melting (LBD) technology is considered an ideal solution for manufacturing such critical components due to its extremely high forming accuracy and excellent part performance. However, traditional LBD technology typically uses a relatively thin powder bed layer (20-60 μm) to ensure forming accuracy, resulting in low single-layer cladding, extremely low forming efficiency, long production cycles, and high costs, severely restricting its large-scale application in the manufacturing of large components. Increasing the powder bed layer thickness can effectively improve the forming speed of LBD, and it is a simple and easy-to-implement technique.

[0025] However, if traditional single fine-particle powder is used directly, increasing the layer thickness will cause a series of process problems: First, due to the strong adhesion and poor flowability between powders, thicker fine powder layers are difficult to form a flat and dense powder bed through the powder spreading device, and are prone to "ploughing" or band breakage; Second, thicker powder layers require higher laser energy input to achieve complete melting, which can easily induce violent metal vapor splashing, unstable molten pool and "spheroidization" effect, ultimately producing defects such as incomplete fusion and pores inside the formed part, causing its density and mechanical properties to fail to meet the requirements of use.

[0026] Existing research clearly demonstrates that powder particle size distribution is a key factor affecting laser powder bed melting processes. Under conditions of large layer thickness, powder size directly regulates laser energy absorption and molten pool behavior, leading to significant differences between powders of different particle sizes: fine powder is beneficial for improving density and suppressing cracks, but has poor flowability and is prone to agglomeration; coarse powder has good flowability, but the molten pool is unstable and prone to incomplete fusion and spheroidization defects. Therefore, the current technical bottleneck lies in the fact that a single powder particle size cannot simultaneously meet the synergistic requirements of powder bed flowability, laser absorption rate, and melting stability for large layer thickness processes, severely restricting the realization of efficient and high-quality forming pathways.

[0027] In summary, traditional laser powder bed melting technology, which uses a single fine-particle powder system, faces a fundamental contradiction when increasing the powder bed thickness: it is difficult to simultaneously achieve both powder bed quality and melting quality. This severely restricts the development of this technology in the field of high-efficiency forming. However, systematically controlling the powder bed's packing structure and laser absorption behavior through scientific particle size matching is considered the most promising technical approach to optimize the complex heat transfer process under large layer thicknesses, overcome existing technological bottlenecks, and achieve high-efficiency and high-quality synergistic forming.

[0028] Reference Figures 1 to 13 The method for stabilizing the laser melting process of powder bed provided by the present invention will now be described.

[0029] Reference Figure 1 and 2The method for stabilizing the powder bed laser melting process includes: S100. Determine the input energy for single-channel laser scanning.

[0030] Preferably, step S100, determining the input energy for a single laser scan, includes: S110. Calculate the minimum heat required to melt a single-layer powder bed.

[0031] The minimum heat required to melt a single-layer powder bed is calculated based on the physical properties of the metal powder and the total thickness of the powder bed using the following formula:

[0032] in, The minimum heat required to melt a single-layer powder bed J ; This refers to the loose bulk density of the metal powder. kg / m 3 ; The volume of powder covered by a single laser scan. m 3 ; This refers to the specific heat capacity of the powder. ; The powder melting temperature, K ; The initial temperature. K ; The latent heat of fusion of the powder, in units of .

[0033] S120. Determine the input energy for a single-channel laser scan based on the minimum heat required to melt a single-layer powder bed.

[0034] The input energy for a single laser scan is calculated using the following formula:

[0035] in, The input energy for single-channel laser scanning. J ; The minimum heat required to melt a single-layer powder bed J ; This refers to the laser absorption efficiency.

[0036] S200. Determine the particle size distribution of the powder bed.

[0037] Preferably, step S200, determining the particle size distribution of the powder bed, includes: S210. Determine the total number of powder bed layers.

[0038]

[0039] in, This represents the total number of powder bed layers. The total thickness of the powder bed. m ; For single-layer powder thickness, m .

[0040] S220. Determine the particle size distribution based on the total number of powder bed layers.

[0041] The particle size distribution of the powder bed is calculated using the following formula:

[0042] in, For the first The number of layers allocated to each granularity level; This represents the total number of powder bed layers. This represents the total number of granularity layers.

[0043] S300. Determine the median particle size of the powder in each particle size layer of the powder bed based on the particle size distribution of the powder bed.

[0044] Preferably, step S300, determining the median particle size of the powder in each particle size layer of the powder bed based on the particle size distribution of the powder bed, includes: S310. Calculate the equivalent thermal conductivity of each particle size layer based on the particle size distribution of the powder bed.

[0045] Calculate the number from top to bottom using the following formula. Equivalent thermal conductivity of the grain size layer:

[0046] in, For the first The equivalent thermal conductivity of the grain size layer, W / (m·K) ; The equivalent thermal conductivity of the topmost grain layer. W / (m·K) ; To increase the constant value, the value is taken as 0.1~0.3.

[0047] S320. Calculate the median particle size of each particle size layer based on the equivalent thermal conductivity of each particle size layer.

[0048] The median grain size of each grain size layer is calculated using the following formula:

[0049] in, For the first Median grain size of the layer m ; For the first The equivalent thermal conductivity of the grain size layer, W / (m·K) ; To protect the inherent thermal conductivity of the gas, W / (m·K) ; This is a material characteristic constant, with a value of 10. -5 ~10 -4 ; The shape and stacking correction index has a value of 1.1-1.5.

[0050] S400. Prepare the required powders at each level according to the particle size distribution of the powder bed and the median particle size of the powders in each particle size layer.

[0051] Preferably, step S400 involves preparing the required powders at each level based on the particle size distribution of the powder bed and the median particle size of each particle size layer, including: S410. Prepare the required powders at each level using gas atomization or plasma rotating electrode atomization, and store them separately.

[0052] In a preferred embodiment, the powder bed has two particle size distribution layers: an upper layer and a lower layer. The upper layer has coarser powder particles, while the lower layer has finer particles. The lower layer powder is prepared using a gas atomization method, and the upper layer powder is prepared using a plasma rotating electrode atomization method.

[0053] In a preferred embodiment, the powder bed has three particle size distribution layers: a bottom layer, a middle layer, and a top layer. The median particle size of the three layers is set in a manner that gradually coarsens from bottom to top. The powder in the middle and bottom layers is prepared by gas atomization, while the powder in the top layer is prepared by plasma rotating electrode atomization.

[0054] S420. Pre-treat powders of all grades.

[0055] Preferably, step S420 involves pretreating the powders at each level, including: S421. Dry the powders at each grade.

[0056] S422. The dried powders at each grade are sieved to remove irregular particles and agglomerates.

[0057] S500. A powder bed is constructed by laying powder layers one by one on the molding substrate of a laser powder bed melting equipment according to the particle size distribution and the median particle size of each powder layer.

[0058] Preferably, the thickness of the powder bed is 100-400 μm.

[0059] Preferably, the powder bed includes a bottom layer and an upper layer; the bottom layer has a thickness of 65%-70%, and the upper layer has a thickness of 30%-35%.

[0060] Preferably, the upper layer includes a middle layer and a top layer, with the middle layer having a thickness of 19.5%-24.5% and the top layer having a thickness of 5.5%-15.5%, and the powder particle size gradually increasing from the bottom layer to the middle layer and the top layer.

[0061] During powder spreading, the powder in the powder hopper containing the finest powder is first dropped onto the substrate by a feeder. Then, a scraper is used to level the powder, thus laying the bottom layer of powder. The scraper is then reset, and powder is spread layer by layer in order from fine to coarse, constructing a powder bed with coarse top and fine bottom.

[0062] S600. Under a protective atmosphere, a laser beam is used to scan and melt the powder bed.

[0063] Preferably, under a protective atmosphere, a laser beam is used to scan and melt the powder bed, including: The laser beam power is 200-500W, and the laser beam scanning speed is 300-800mm / s.

[0064] S700. In-situ monitoring is performed during the powder bed melting process to analyze the melting process of the powder bed and obtain monitoring results.

[0065] In the powder bed structure provided in this embodiment, the variance of liquid level fluctuation during melting is between 69 and 2821, indicating more stable liquid level fluctuation. The liquid level height is between 140 μm and 200 μm, resulting in good molten pool stability. Since the melting of the upper coarse powder particles requires more heat, the heat transfer rate on the powder bed is slowed down, reducing the melting and vaporization rate of the metal powder and weakening the thermal convection intensity and backlash pressure.

[0066] S800. Perform quality analysis on the melt channel obtained from powder bed melting to obtain melt channel characterization results.

[0067] In a preferred embodiment, step S800 involves performing quality analysis on the melt channel obtained from powder bed melting to obtain melt channel characterization results, including: S810. Analyze the surface morphology and roughness of the melt channel.

[0068] S820. Take a sample from the cross-section of the melt channel and perform microstructure analysis.

[0069] Samples were cut from the melt channel section using wire electrical discharge machining. The samples were then subjected to grinding, mechanical polishing, and electropolishing, followed by ultrasonic cleaning of the electropolished samples. Microstructure analysis was performed on the ultrasonically cleaned samples.

[0070] When polishing the sample, use 400-grit, 800-grit, 1200-grit, and 2000-grit silicon carbide sandpaper sequentially for dry or wet polishing. Rotate the sample 90° each time to remove the cutting damage layer until the surface is free of obvious scratches. For mechanical polishing, use 3μm and 1μm diamond stones sequentially. During polishing, use polishing paste and a polishing cloth. After each polishing, ultrasonically clean with anhydrous ethanol for 3 minutes. For electrolytic polishing, immerse the mechanically polished sample in an electrolyte solution and electrolyze for 1-2 minutes at an electrolytic current of 0.3-0.4A. The electrolyte solution consists of 10% perchloric acid and 90% anhydrous ethanol.

[0071] When ultrasonically cleaning samples that have undergone electropolishing, rinse the electropolished samples with alcohol, place the rinsed samples in a beaker containing alcohol, and clean them with an ultrasonic cleaner for 2-5 minutes.

[0072] S900. Adjust the thickness of each layer of the powder bed based on the monitoring results and the melt channel characterization results.

[0073] Based on the laser powder bed melting forming method proposed above, multiple sets of experiments were designed. (1) 100μm layer thickness: laser power of 200W, 250W, and 300W, corresponding to scanning speeds of 800mm / s, 700mm / s, and 600mm / s; (2) 200μm layer thickness: laser power of 250W, 300W, and 350W, corresponding to scanning speeds of 600mm / s, 500mm / s, and 450mm / s; (3) 300μm layer thickness: laser power of 300W, 400W, and 450W, corresponding to scanning speeds of 500mm / s, 400mm / s, and 350mm / s; (4) 400μm layer thickness: laser power of 400W and 500W, corresponding to scanning speeds of 350mm / s and 300mm / s.

[0074] Reference Figure 3 and 4 Among the above parameter combinations, a layer thickness of 400μm, a laser power of 500W, and a scanning speed of 350mm / s were selected as a typical example for detailed analysis. The selected material was 316L stainless steel, and the powder spreading method was coarse on top and fine on the bottom, with a coarse powder / fine powder ratio of 1 / 3.

[0075] Reference Figures 5 to 10 Conventional powder beds generate more splashing during the melting process, resulting in more violent fluctuations in the molten pool surface. For example... Figure 4 As shown, the powder bed constructed using the embodiments of the present invention exhibits a more stable coarse-to-fine (coarse powder / fine powder: 1 / 3) melting process, fewer splashes, and a more uniformly shaped melt channel with a smooth and flat surface. The melt channels formed by a conventional powder bed are as follows: Figure 5As shown, there are obvious necking and protrusion defects. Smaller grain size and more uniform distribution are generally more conducive to improving the strength and plasticity of the formed parts.

[0076] Reference Figure 11 and Figure 12 The powder bed structure constructed using the embodiments of the present invention achieves a finer average grain size (6.51 μm vs. 7.59 μm) and a smaller maximum grain size (42.17 μm vs. 73.67 μm) compared to conventional powder beds, resulting in a more uniform grain structure and thus providing microstructural assurance for obtaining excellent mechanical properties. Figure 13 As shown, the stress-strain curve of the powder bed molded part constructed using the embodiments of the present invention is generally better than that of the conventional powder bed sample, exhibiting higher tensile strength and better plasticity.

[0077] The beneficial effects of the method for stabilizing the laser melting process of powder beds provided by this invention are as follows: Compared with the prior art, the method of this invention achieves precise control over the entire process, including laser energy supply, powder bed structure design, powder preparation and processing, powder spreading and forming, laser melting, process monitoring, and parameter optimization. This significantly improves the stability and forming quality of the laser powder bed melting process under large layer thickness conditions. By accurately calculating the minimum heat required to melt the powder bed, the input energy of a single laser scan is defined, ensuring a precise match between the laser energy input and the actual heat requirement for powder melting. This effectively avoids the problem of insufficient powder fusion caused by insufficient energy input, and completely eliminates process defects such as molten pool instability and metal vapor splashing caused by excessive energy. This provides a suitable and stable energy foundation for the laser melting process, ensuring the controllability of the melting process from the energy regulation level.

[0078] By defining the total number of layers and calculating the equivalent thermal conductivity, the particle size distribution of the powder bed and the median particle size of each layer are planned. This ensures that the structural design of the powder bed is highly compatible with the heat transfer requirements of laser melting, breaking the technical limitation that single-size powders cannot simultaneously achieve both powder spreadability and melting stability. It provides a scientific and precise parameter basis for constructing large-layer-thickness powder beds from the structural design stage. Following the predetermined particle size distribution and median particle size, professional atomization technology is used to prepare powders at each level, combined with pretreatment processes such as drying and sieving. This effectively removes irregular particles and agglomerates from the powder, significantly improving the purity, regularity, and spreadability of the powder. This ensures that the physical properties of the powder are fully adapted to the energy transfer and heat conduction requirements of the melting process. Simultaneously, it allows for the separate storage of powders of different particle sizes, avoiding performance deviations caused by mixing powders of different sizes, thus laying a high-quality material foundation for the subsequent precise laying of the powder bed.

[0079] A tiered powder bed structure is constructed by layering powder onto a molding substrate according to set parameters. Precise control of the overall thickness of the powder bed and the thickness ratio of each layer results in an ideal heat flow pattern where the heat transfer rate increases from top to bottom. This effectively regulates the transmission path of laser energy within the powder bed, allowing powders of different particle sizes to fully utilize their heat transfer and melting characteristics. This powder-laying method ensures uniform thickness and clear boundaries across powder bed layers, structurally solving the industry problem of uneven laser energy transmission attenuation and heat accumulation under large layer thickness conditions. It keeps the dynamic behavior of the molten pool under control. Simultaneously, the coarser top and finer bottom particle size distribution slows down the heat transfer rate on the powder bed, reducing the melting and vaporization speed of the metal powder, further weakening the thermal convection intensity and back pressure, and significantly improving the stability of the molten pool.

[0080] Under a protective atmosphere, a laser beam with set power and scanning speed is used to scan and melt the powder bed. This ensures a good match between the laser energy output and the melting requirements of the tiered powder bed structure, guaranteeing full penetration of the thick powder bed while effectively suppressing process defects such as spheroidization, resulting in a more stable laser melting process. In-situ monitoring during the powder bed melting process allows for real-time capture of key status information such as liquid level fluctuations and molten pool height. Precise analysis of the dynamic changes in the melting process provides accurate and comprehensive process data support for subsequent process parameter adjustments, achieving dynamic and visualized control of the melting process.

[0081] Multi-dimensional quality analysis, including surface morphology, roughness analysis, and microstructure characterization, is performed on the melt channel obtained after melting. This allows for precise control of the melt channel's forming quality and clear identification of potential minute defects during the melting process, resulting in a more comprehensive and accurate evaluation of the melt channel quality. By combining in-situ monitoring process data and melt channel quality characterization results, targeted adjustments are made to the thickness of each layer of the powder bed, achieving closed-loop optimization of process parameters. This enables the powder bed's structural design to adapt in real-time to actual melting effects and forming quality, continuously optimizing laser energy transmission and heat conduction, ensuring the entire melting process remains in optimal condition.

[0082] This complete technical solution achieves a synergistic unity of high-efficiency and high-quality forming under large-layer thickness conditions. While increasing powder bed thickness to tens of times that of conventional thin layers, it maintains high printing efficiency while achieving the high precision and excellent performance typically found only in thin-layer printing. This results in parts with higher density, smoother surface quality, and superior microstructure. By actively controlling the heat transfer path of the powder bed and the molten pool dynamics, this solution fundamentally solves the core contradiction of balancing powder spreading quality and melting quality in large-layer forming. It overcomes the process bottleneck of traditional laser powder bed melting technology in large-layer forming, significantly improving the forming efficiency and application range of laser powder bed melting technology. This provides a feasible technical path for the large-scale, industrial application of this technology in the manufacturing of large and complex metal components.

[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0084] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0085] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

Claims

1. A method for stabilizing a powder bed laser melting process, characterized in that, include: Determine the input energy for single-channel laser scanning; Determine the particle size distribution of the powder bed; The median particle size of the powder in each particle size layer of the powder bed is determined based on the particle size distribution of the powder bed. The required powders at each level are prepared based on the particle size distribution of the powder bed and the median particle size of the powders in each particle size layer. On the molding substrate of the laser powder bed melting equipment, each layer of powder is laid layer by layer according to the particle size distribution and the median particle size of each layer of powder to construct a powder bed. Under a protective atmosphere, a laser beam is used to scan and melt the powder bed; In-situ monitoring is performed during the melting process of the powder bed to analyze the melting process and obtain monitoring results; The quality of the melt channel obtained by melting the powder bed is analyzed to obtain the melt channel characterization results; Based on the monitoring results and the melt channel characterization results, the thickness of each layer of the powder bed is adjusted.

2. The method for stabilizing the powder bed laser melting process as described in claim 1, characterized in that, Determine the input energy for a single laser scan, including: Calculate the minimum heat required to melt a single-layer powder bed; The input energy for a single-channel laser scan is determined based on the minimum heat required to melt the single-layer powder bed.

3. The method for stabilizing the powder bed laser melting process as described in claim 1, characterized in that, Determining the particle size distribution of the powder bed includes: Determine the total number of layers in the powder bed; The particle size distribution is determined based on the total number of layers in the powder bed.

4. The method for stabilizing the powder bed laser melting process as described in claim 1, characterized in that, The median particle size of the powder in each particle size layer of the powder bed is determined based on the particle size distribution of the powder bed, including: The equivalent thermal conductivity of each particle size layer is calculated based on the particle size distribution of the powder bed. The median particle size of each particle size layer is calculated based on the equivalent thermal conductivity of each particle size layer.

5. The method for stabilizing the powder bed laser melting process as described in claim 1, characterized in that, The thickness of the powder bed is 100-400 μm.

6. The method for stabilizing the powder bed laser melting process as described in claim 5, characterized in that, The powder bed comprises a bottom layer and an upper layer; the bottom layer has a thickness of 65%-70%, and the upper layer has a thickness of 30%-35%.

7. The method for stabilizing the powder bed laser melting process as described in claim 6, characterized in that, The upper layer includes a middle layer and a top layer. The thickness of the middle layer is 19.5%-24.5%, and the thickness of the top layer is 5.5%-15.5%. The particle size of the powder in the bottom layer, the middle layer, and the top layer gradually increases.

8. The method for stabilizing a powder bed laser melting process as described in claim 1, characterized in that, The step of scanning and melting the powder bed using a laser beam under a protective atmosphere includes: The power of the laser beam is 200-500W, and the scanning speed of the laser beam is 300-800mm / s.

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