An additive manufacturing method based on non-full melting metal powder

Abstract

The application discloses an additive manufacturing method based on non-complete melting metal powder and belongs to the technical field of metal additive manufacturing. The additive manufacturing method based on non-complete melting metal powder comprises the following steps: obtaining a three-dimensional model of a target component, slicing and layering the three-dimensional model and planning a scanning path, and importing slice data and scanning path planning data into an additive manufacturing device; laying metal powder on a substrate to form a powder layer; controlling an energy beam to scan the powder layer according to slice data of the target component; repeating the powder layer laying and scanning steps to process layer by layer to obtain the component. The application precisely controls the energy density of the energy beam within a process window in which the surface of the metal powder is melted and bonded while the core is not melted, and the component is formed by layer-by-layer scanning, thereby solving the technical problems of high residual stress, cracks and poor organization performance caused by complete melting in the powder bed melting technology in the prior art.

Description

Technical Field

[0001] This application belongs to the field of metal additive manufacturing technology, and specifically relates to an additive manufacturing method based on incompletely melted metal powder. Background Technology

[0002] Powder bed melting technology, including selective laser melting (SLM) and electron beam melting (EBM), is a key technology for manufacturing high-performance complex metal components. Its principle is to completely melt metal powder layer by layer using a high-energy beam (laser / electron beam) to achieve three-dimensional solidification. However, for materials such as nickel-based superalloys and titanium alloys, the complete melting process is accompanied by a large temperature gradient and rapid solidification, leading to significant residual stress, hot cracking tendency, elemental segregation, and coarse columnar grain structure within the component, severely affecting the component's dimensional accuracy, mechanical properties, and service reliability.

[0003] To alleviate these problems, existing technologies mainly focus on optimizing scanning strategies, preheating substrates, and post-heat treatment. For example, Germany has conducted extensive research on combining sintering and additive manufacturing technologies. Projects such as the "Bavarian Manufacturing Alliance" aim to improve part accuracy and cost-effectiveness through process chain integration and simulation optimization. However, these improvements are essentially optimizations within the framework of "complete melting," failing to fundamentally address the inherent problems caused by high energy input. On the other hand, while traditional powder sintering technology can manufacture complex shapes with low stress, it relies on solid-state diffusion, resulting in low densification efficiency and difficulty in obtaining near-fully dense, high-strength metal parts, thus failing to meet the performance requirements of main load-bearing structural components.

[0004] Therefore, the industry urgently needs a new additive manufacturing method that can maintain near-net-shape forming capability and high material properties while physically suppressing the generation of high stress and defects. Summary of the Invention

[0005] The purpose of this invention is to provide an additive manufacturing method based on incompletely melted metal powder, which solves the technical problems of high residual stress, cracks and poor microstructure and properties caused by complete melting in the powder bed melting technology of the prior art.

[0006] To achieve the above objectives, one embodiment of the present invention provides an additive manufacturing method based on incompletely molten metal powder, comprising the following steps: The three-dimensional model of the target component is obtained, the three-dimensional model is sliced ​​and layered and the scanning path is planned, and the slice data and scanning path planning data are imported into the additive manufacturing device. Metal powder is deposited on a substrate to form a powder layer; Based on the layer data of the target component, control the energy beam to scan the powder layer; Repeat the powder layering and scanning steps, processing layer by layer to obtain the component; In particular, during or after the layer-by-layer processing, the formed area is subjected to in-situ periodic heat treatment.

[0007] One preferred embodiment of the present invention is to lay metal powder on a substrate to form a powder layer, including: preheating the powder layer at a temperature of 40%-70% of the solidus temperature of the metal powder.

[0008] In one preferred embodiment of the present invention, the thickness of the powder layer is 20μm-100μm.

[0009] In one preferred embodiment of the present invention, the metal powder is any one of nickel-based alloy powder, titanium alloy powder, and cobalt-chromium alloy powder.

[0010] One preferred embodiment of the present invention involves controlling an energy beam to scan a powder layer based on the layer data of the target component, including: the energy density applied by the energy beam being between the initial energy density at which the metal powder undergoes sintering and the critical energy density at which the metal powder completely melts.

[0011] One preferred embodiment of the present invention involves controlling an energy beam to scan a powder layer based on the layer data of the target component, including: applying an energy density to the energy beam such that the volume fraction of incompletely melted metal powder particles is greater than 50%.

[0012] In one preferred embodiment of the present invention, the incomplete melting volume fraction of metal powder particles is greater than 50% by controlling the electron beam processing parameters or laser processing parameters; wherein the electron beam processing parameters include: layer thickness of 20μm-100μm, line spacing of 0.08mm-0.20mm, scanning speed of 3000mm / s-10000mm / s, beam current of 3mA-12mA, and volume energy density of 20J / mm². 3 -60J / mm 3 The laser processing parameters include: layer thickness of 20μm-60μm, line spacing of 0.05mm-0.15mm, scanning speed of 500mm / s-2000mm / s, laser power of 100W-300W, and volume energy density of 50J / mm². 3 -150J / mm 3 .

[0013] One preferred embodiment of the present invention involves controlling an energy beam to scan a powder layer based on the layer data of the target component, including: performing partitioned processing on regions with different geometric features using different scanning energy densities or scanning strategies based on the three-dimensional model of the target component.

[0014] In one preferred embodiment of the present invention, the linear energy density of the energy beam is 0.04 J / mm-0.12 J / mm.

[0015] One preferred embodiment of the present invention is in-situ periodic heat treatment, comprising: re-scanning the scanned area with an energy beam at a power lower than that of the powder layer scanning energy.

[0016] One preferred embodiment of the present invention, an additive manufacturing method based on incompletely molten metal powder, further includes: post-processing the obtained component, the post-processing including hot isostatic pressing and / or machining.

[0017] Compared with the prior art, this application has the following advantages: 1. The present invention is based on an additive manufacturing method for incompletely molten metal powder. By creating a unique metallurgical state in which powder particles are firmly bonded by an instantaneous liquid phase while the particle core is not completely melted, the present invention significantly reduces thermal stress, eliminates cracks, and obtains a superior microstructure with uniform composition and fine grains while ensuring high density and high strength of the component.

[0018] 2. The additive manufacturing method based on incompletely melted metal powder of this invention fundamentally eliminates large molten pools and extremely high temperature gradients through the "incomplete melting" mechanism, reducing the thermal stress of the forming process to an extremely low level. Furthermore, examples show that its residual stress can be reduced by more than 60% compared to the traditional SLM process, fundamentally eliminating the generation of hot cracks. It is particularly suitable for the manufacture of complex components of easily cracked nickel-based high-temperature alloys (such as hollow turbine blades).

[0019] 3. This invention avoids element segregation and directional epitaxial growth caused by complete melting, which is conducive to the formation of uniform and fine equiaxed or directional fine-grained structures. Such structures give the components more isotropic mechanical properties and higher fatigue-creep performance.

[0020] 4. The additive manufacturing method based on incompletely melted metal powder of this invention is particularly suitable for implementation in vacuum electron beam equipment, providing an excellent protective environment for active materials such as titanium and aluminum. By integrating online monitoring (such as thermal imaging) and process simulation, real-time feedback and precise control of the "incompletely melted" state can be achieved, and the process window is stable and reliable.

[0021] 5. Based on obtaining a high-integrity blank, this invention lays an ideal foundation for subsequent integrated hybrid manufacturing (such as laser shock strengthening or precision milling of specific areas), and can realize the integrated forming and finishing of high-performance components with complex internal flow channels, lattice cores and other structures.

[0022] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures pointed out in the description and the accompanying drawings. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic flowchart of an additive manufacturing method based on incompletely molten metal powder in one embodiment of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0027] This invention discloses an additive manufacturing method based on incompletely molten metal powder, such as... Figure 1 As shown, it includes the following steps: Step (1): Obtain the 3D model of the target component, perform slicing and layering and scan path planning on the 3D model, and import the slicing data and scan path planning data into the additive manufacturing device; Specifically, obtain the 3D CAD model of the target component, perform slicing and layering processing, generate the contour and filling scan path of each layer, and import the above data into the additive manufacturing device; Based on the process simulation model, predict the heat accumulation of different geometric feature areas of the component (such as thin walls, overhanging surfaces, and large solids) during the processing, and provide a basis for zoned energy input control; Step (2): Laying metal powder on the substrate to form a powder layer; specifically, in the forming chamber of the additive manufacturing apparatus, a layer of metal powder of a predetermined thickness is laid on the substrate to form a powder layer; preferably, the metal powder is any one of nickel-based alloy powder, titanium alloy powder and cobalt-chromium alloy powder, wherein the nickel-based alloy powder is nickel-based high-temperature alloy powder; the thickness of the powder layer is 20μm-100μm; further, laying metal powder on the substrate to form a powder layer includes: preheating the powder layer at a temperature of 40%-70% of the solidus temperature of the metal powder, in order to reduce thermal shock and assist the subsequent incomplete melting process; Step (3): Based on the layer data of the target component, control the energy beam to scan the powder layer; specifically, based on the scanning path data of the current layer of the target component, control the energy beam (preferably an electron beam, but also a laser beam) to selectively irradiate and scan the powder layer. During the scanning process, the energy density applied by the energy beam is between the initial energy density at which the metal powder sinters and the critical energy density at which the metal powder completely melts. This energy input is sufficient to melt the surface and contact area of ​​the powder particles, form liquid bridges, and quickly solidify to achieve metallurgical bonding. At the same time, it ensures that at least 50% of the volume fraction of powder particles retains its core area as an incompletely melted solid. That is, the energy density applied by the energy beam makes the volume fraction of the metal powder particles that are not completely melted greater than 50%. This process can be achieved by controlling the parameters such as beam current, scanning speed, and line spacing in the electron beam processing process parameters or laser processing process parameters. The specific process parameter control is shown in Table 1. Table 1: Summary Table of Process Parameters

[0028] In electron beam processing, the narrower line spacing helps to fully bond within the layers, and the extremely fast electron beam scanning speed is key to achieving rapid local heating and cooling. Laser processing requires a protective atmosphere, and because the laser spot is usually smaller, denser scanning lines are needed. A "low power-medium speed" combination is used in laser processing to avoid excessive power causing complete melting.

[0029] Preferably, based on the three-dimensional model of the target component, different scanning energy densities or scanning strategies are used to process regions with different geometric features in separate areas; further, the linear energy density of the energy beam is 0.04 J / mm-0.12 J / mm. Step (4): Repeat the powder layer laying and scanning steps, and process layer by layer to obtain the component; specifically, in step (3), after the current layer is scanned in the powder layer scanning, the forming platform drops by one layer thickness height, and repeats the powder layer laying in step (2) and the scanning steps in step (3) to build up layer by layer until the entire component is completed; wherein, when processing a new layer, part of the thermal effect of the energy beam will act on the previous layer that has been formed, promoting the interlayer to achieve incomplete melting and bonding with the layer; In the process of layer-by-layer processing or after layer-by-layer processing, the formed area is subjected to in-situ periodic heat treatment. The in-situ periodic heat treatment includes: scanning the scanned area again with an energy beam at a power lower than that of the powder layer scanning. Specifically, after scanning N layers (N is an integer from 2 to 10) or after the entire component is manufactured, a large-area, slow secondary scan is performed on the formed area using a defocused or low-power energy beam. This step is not intended to add new material, but to provide a mild and uniform thermal field, which plays a role similar to "in-situ hot isostatic pressing", further promoting the closure of micropores and the homogenization of the structure, and reducing internal stress. The additive manufacturing method based on incompletely molten metal powder also includes: post-processing of the obtained component, including hot isostatic pressing and / or machining; specifically, after the component is cooled in the forming chamber according to a set program, it is taken out and after operations such as removing loose powder and wire cutting to separate the substrate, hot isostatic pressing, solution aging heat treatment or necessary machining (reflecting the concept of hybrid manufacturing) can be applied as needed to obtain the final part.

[0030] This invention is an innovative method for forming complex components by precisely controlling the energy input to keep the metal powder in a partially molten state through additive manufacturing of incompletely molten metal powder. This method is particularly suitable for manufacturing high-temperature alloy parts such as nickel-based and titanium-based alloys that have stringent requirements for residual stress, cracks and microstructure properties.

[0031] Example 1 The manufacturing process of Inconel 718 nickel-based superalloy aero-engine turbine blades includes the following steps: Materials and Equipment: Inconel 718 alloy spherical powder with a particle size range of 15-53 μm was prepared by gas atomization. An Arcam A2X electron beam powder bed melting system, equipped with a programmable scanning system and an infrared thermal imaging monitoring module, was used.

[0032] Process parameters and procedures: Preheating temperature of substrate and powder bed: 900℃.

[0033] Layer thickness: 50μm.

[0034] Core incomplete melting scanning parameters: accelerating voltage 60kV, beam current 8mA, scanning speed 8000mm / s, line spacing 100μm. The calculated linear energy density is approximately 0.06J / mm. These parameters, calibrated through preliminary experiments, represent the optimal window center values ​​for achieving stable incomplete melting of IN718 powder.

[0035] In-situ heat treatment parameters: After every 5 layers are completed, a full scan of the entire component cross section is performed using a defocused electron beam (beam current reduced to 3 mA, scanning speed reduced to 2000 mm / s).

[0036] Process monitoring: The thermal imaging system showed that the peak temperature of the molten pool during the scanning process remained stable at about 1250°C, which is lower than the complete melting temperature of IN718 (about 1330°C), and the size of the molten pool was small and stable without drastic fluctuations.

[0037] Post-treatment: The components are cooled to 300°C at a rate of 10°C / min in the equipment and then removed. They are then subjected to standard hot isostatic pressing (1180°C, 100MPa, 3 hours) and two-stage aging heat treatment.

[0038] Test results: Density: Determined by Archimedes' water displacement method, the density is greater than 99.6%.

[0039] Residual stress: The surface residual stress was determined by X-ray diffraction, with an average value of approximately +85 MPa (tensile stress). As a comparative example, the average value of the SLM formed part at the same measurement location was +320 MPa.

[0040] Microstructure: The microstructure consists of uniform and fine γ matrix grains and diffusely distributed δ phase and γ´ / γ" strengthening phase. No obvious melt pool boundaries and columnar crystal structure were observed, and no microcracks were found.

[0041] Mechanical properties: Room temperature tensile properties: tensile strength ≥1350MPa, yield strength ≥1150MPa, elongation ≥18%, with isotropic properties significantly superior to fully melt-formed parts.

[0042] Example 2 The manufacturing process of complex Ti-6Al-4V titanium alloy frame components includes the following steps: Materials and Equipment: Ti-6Al-4V ELI grade titanium alloy powder was used, and the equipment was the same as in Example 1.

[0043] Process parameters and procedures: Preheating temperature: 680℃.

[0044] Layer thickness: 60μm.

[0045] Core incomplete melting scanning parameters: accelerating voltage 60kV, beam current 6mA, scanning speed 7200mm / s. Linear energy density is approximately 0.05J / mm.

[0046] Zoned energy control: For solid regions with a thickness greater than 5 mm in the component, the scanning speed is increased to 8500 mm / s (energy density slightly reduced) to prevent overheating; for thin-walled regions with a thickness less than 1.5 mm, the scanning speed is reduced to 6000 mm / s (energy density slightly increased) to ensure bonding strength. This zoned strategy is based on previous finite element thermodynamic simulation results.

[0047] Post-treatment: Stress-relief annealing only (700℃, 2h, furnace cooling).

[0048] Test results: The component exhibits high dimensional accuracy and exhibits no warping deformation despite its thin walls. Internal non-destructive testing (CT) revealed no voids or lack of fusion defects. The microstructure is a fine α+β dual-phase structure, and its performance meets aerospace standards.

[0049] Comparative example: Traditional high-energy-density electron beam complete melting manufacturing includes the following steps: The same Inconel 718 powder and equipment as in Example 1 were used.

[0050] Process parameters: Adopting industry-standard full melting parameters to achieve high density. Accelerating voltage 60kV, beam current 18mA, scanning speed 4000mm / s, and linear energy density up to 0.27J / mm.

[0051] result: During the molding process, a distinct micro-explosion sound (splashing) can be heard.

[0052] After the component cools, macroscopic cracks are visible to the naked eye at the edges and thin walls.

[0053] Metallographic analysis revealed that coarse epitaxial columnar crystals penetrated multiple molten pools, and multiple microscopic hot cracks were found at the boundaries of the molten pools.

[0054] The residual stress test value was extremely high, and one blade broke when it was wire-cut and separated from the substrate.

[0055] Although the density reached 99.4%, the component was scrapped due to the presence of cracks.

[0056] The performance data of Example 1 and the comparative example are shown in Table 2.

[0057] Table 2: Performance data of Example 1 and Comparative Example

[0058] As can be seen from Table 2, the performance of the component prepared by the method of Example 1 is better than that of the component prepared by the comparative method, which shows that the component prepared by the additive manufacturing method based on incompletely molten metal powder of the present invention has excellent performance.

[0059] In summary, this invention achieves a unique metallurgical bonding state of "incomplete melting" by precisely controlling the energy density of the energy beam within a process window that melts and bonds the surface of the metal powder while keeping the core unmelted, and then scanning and forming layer by layer. This is further enhanced by in-situ periodic heat treatment, which fundamentally reduces residual stress and crack sensitivity in the additive manufacturing process. This results in a uniform and fine microstructure, making it particularly suitable for manufacturing complex components of high-performance nickel-based and titanium-based high-temperature alloys, such as aerospace engine blades and complex frames.

[0060] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. An additive manufacturing method based on incompletely molten metal powder, characterized in that, Includes the following steps: The three-dimensional model of the target component is obtained, the three-dimensional model is sliced ​​and layered and the scanning path is planned, and the slice data and scanning path planning data are imported into the additive manufacturing device. Metal powder is deposited on a substrate to form a powder layer; Based on the layer data of the target component, control the energy beam to scan the powder layer; Repeat the powder layering and scanning steps, processing layer by layer to obtain the component; In particular, during or after the layer-by-layer processing, the formed area is subjected to in-situ periodic heat treatment.

2. The additive manufacturing method based on incompletely molten metal powder as described in claim 1, characterized in that: The step of depositing metal powder on a substrate to form a powder layer includes: preheating the powder layer at a temperature of 40%-70% of the solidus temperature of the metal powder.

3. An additive manufacturing method based on incompletely molten metal powder as described in claim 1 or 2, characterized in that: The thickness of the powder layer is 20μm-100μm.

4. The additive manufacturing method based on incompletely molten metal powder as described in claim 1, characterized in that: The metal powder is any one of nickel-based alloy powder, titanium alloy powder, and cobalt-chromium alloy powder.

5. The additive manufacturing method based on incompletely molten metal powder as described in claim 1, characterized in that: The step of controlling the energy beam to scan the powder layer based on the layer data of the target component includes: the energy density applied by the energy beam is between the initial energy density at which the metal powder sinters and the critical energy density at which the metal powder completely melts.

6. An additive manufacturing method based on incompletely molten metal powder as described in claim 1 or 5, characterized in that: The step of controlling the energy beam to scan the powder layer based on the layer data of the target component includes: the energy density applied by the energy beam is such that the volume fraction of the metal powder particles that are not completely melted is greater than 50%.

7. The additive manufacturing method based on incompletely molten metal powder as described in claim 6, characterized in that: By controlling the electron beam processing parameters or laser processing parameters, the volume fraction of incompletely melted metal powder particles is made greater than 50%. The electron beam processing parameters include: layer thickness of 20μm-100μm, line spacing of 0.08mm-0.20mm, scanning speed of 3000mm / s-10000mm / s, beam current of 3mA-12mA, and volume energy density of 20J / mm². 3 -60J / mm 3 The laser processing parameters include: layer thickness of 20μm-60μm, line spacing of 0.05mm-0.15mm, scanning speed of 500mm / s-2000mm / s, laser power of 100W-300W, and volume energy density of 50J / mm². 3 -150J / mm 3 .

8. The additive manufacturing method based on incompletely molten metal powder as described in claim 1, characterized in that: The step of controlling the energy beam to scan the powder layer based on the layer data of the target component includes: performing partitioned processing on regions with different geometric features using different scanning energy densities or scanning strategies based on the three-dimensional model of the target component.

9. The additive manufacturing method based on incompletely molten metal powder as described in claim 1, characterized in that: The linear energy density of the energy beam is 0.04 J / mm - 0.12 J / mm.

10. The additive manufacturing method based on incompletely molten metal powder as described in claim 1, characterized in that: The in-situ periodic heat treatment includes: re-scanning the already scanned area using an energy beam at a power lower than that used for scanning the powder layer.

11. The additive manufacturing method based on incompletely molten metal powder as described in claim 1, characterized in that: The additive manufacturing method based on incompletely molten metal powder further includes: post-processing the obtained component, wherein the post-processing includes hot isostatic pressing and / or machining.

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