Additive manufacturing method of load-sweating integrated structure

Abstract

The application discloses an additive manufacturing method of a bearing-sweating integrated structure, and has the characteristics of including: constructing a space of a bearing-sweating integrated structure envelope; filling the space of the envelope with a designed double-diagonal lattice structure unit to form a numerical model of a lattice bearing structure; performing a Boolean subtraction operation to obtain a numerical model of a capillary sweating structure; importing a software to perform a subdivision processing and divide different scanning strategies; importing an additive manufacturing equipment to perform additive manufacturing; performing wire cutting and surface cleaning to obtain a structure sample. Only the information of the outer dimension is needed to model and process, the porosity of different parts can be flexibly regulated, the sweating cooling capacity can be stably and controllably regulated, direct printing can be realized through model placement, no support is needed, the bearing capacity of the structure can be further improved through a topological optimization design method or the like, and the method has strong universality and can realize rapid forming of a complex bearing-sweating integrated structure.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and in particular to an additive manufacturing method for a lattice-capillary composite load-bearing-sweating integrated structure. Background Technology

[0002] Enhancing the ultra-long-range flight capability and ultra-high-speed penetration capability of hypersonic vehicles is an urgent need for a generational upgrade in this field and has significant strategic importance. Developing higher Mach numbers, longer ranges, and reliable service is the development direction for hypersonic vehicles. With the significant increase in the Mach number of hypersonic vehicles, their key components (such as the nose cone, wing leading edge, air intake, and scramjet engine fuel injection support) will experience higher heat flux densities during service. Simultaneously, they must maintain the integrity of the aerodynamic structure under complex and variable force-thermal loads, posing significant challenges to the thermal protection and load-bearing capacity of these components.

[0003] Sweating cooling technology is one of the most advanced thermal protection technologies with the strongest heat exchange capacity currently available. It can effectively cool critical parts of hypersonic vehicles under service conditions, ensuring that the vehicle is not subjected to high-temperature ablation. This technology mainly includes laminated sweating and microporous sweating. There has been considerable research on sweating cooling technology both domestically and internationally, and it has been applied to critical components such as the nose cone, sharp leading edge, and air intake. Currently, laminated sweating cooling and microporous sweating cooling technologies are the primary methods used.

[0004] Laminated plate sweating cooling technology refers to the process of stacking a large number of porous metal sheets together according to a pre-defined flow channel, and then using techniques such as diffusion welding to create a laminated plate structure. For example, patent publication number CN112765913A describes a layered gradient porous material sweating cooling structure and aircraft, which achieves flow control of the laminated plate sweating structure by stacking N layers (N>2) of porous material, with the porosity decreasing layer by layer along the direction closer to the cooling chamber. Another example is patent publication number CN103192978A, which describes a laminated plate sweating and reverse-jet combined cooling nose cone, which is constructed by coaxially stacking spherical-conical laminates and achieving directional delivery of the cooling medium through a pre-defined control flow channel. While these disclosed technologies can solve the problem of short-term thermal protection of components to some extent, the manufacturing process of complex structural components is extremely complex and prone to "local hot spot effects," leading to localized ablation failure of the laminated plate sweating components.

[0005] Microporous sweating cooling technology, especially sweating cooling structures with capillary structures, enables controllable adjustment of the cooling medium flow rate, making it suitable for sweating cooling components operating in more complex environments with higher heat flux densities. For example, patent publication number CN109334974B studies a flow-controlled impact sweating cooling head cone. This head cone utilizes powder metallurgy to prepare a porous head cone end face, allowing for porosity adjustment through control of the powder metallurgy sintering process, thereby controlling the cooling medium flow rate and improving sweating cooling efficiency. Another example is patent publication number CN112935277A, which describes a laser selective melting forming method for multi-level interconnected microporous metal sweating structures. This method utilizes additive manufacturing to achieve three-level micropores from millimeters to micrometers, efficiently realizing the overall forming of various complex metal sweating structures and ensuring uniform and stable sweating cooling capacity. However, existing research on capillary sweating cooling mainly focuses on thermal protection capabilities, resulting in weak structural load-bearing capacity and susceptibility to deformation and failure under external forces. Summary of the Invention

[0006] The purpose of this invention is to solve the problem of weak load-bearing capacity in existing capillary sweating structures, and to provide an additive manufacturing method for an integrated load-bearing and sweating structure. This method organically combines a lattice load-bearing structure with a capillary sweating structure, which can balance load-bearing and sweating performance, and can achieve efficient integrated preparation through additive manufacturing.

[0007] The above-mentioned technical problem of the present invention is mainly solved by the following technical solution: an additive manufacturing method for a load-bearing-sweating integrated structure, characterized by comprising the following steps:

[0008] Step (1) Construct the space of the integrated load-bearing and sweating structure envelope;

[0009] Step (2) Fill the space enveloped by step (1) with the designed double diagonal lattice structure units to form the digital model of the lattice bearing structure;

[0010] Step (3) Perform a Boolean subtraction operation between the space of the integrated load-sweating structure envelope in step (1) and the lattice load-bearing structure digital model in step (2) to obtain the digital model of the capillary sweating structure;

[0011] Step (4) The lattice bearing structure model in step (2) and the capillary sweating structure model in step (3) are respectively imported into the special software for subdivision processing, and different scanning strategies are set. The model in step (2) is set to the printing strategy of dense structure, and the model in step (3) is set to the printing strategy of capillary structure.

[0012] Step (5) Import the model after step (4) into the additive manufacturing equipment to carry out additive manufacturing of the load-sweating integrated structure. First, print the outline of the lattice load-bearing structure digital model in step (2), and then print the internal structure of the digital model and the capillary sweating structure digital model in step (3).

[0013] After printing in step (6), the sample of the load-bearing and sweating integrated structure is obtained by wire cutting and surface cleaning.

[0014] In step (2) of the aforementioned additive manufacturing method for the integrated load-sweating structure, preferably, the lattice structure includes, but is not limited to, a double diagonal lattice structure, the size range of the lattice structure unit is 2 to 10 mm, the basic unit of the lattice structure is composed of rods, tubes or plates, the rod size is 0.1 to 1 mm, the outer diameter and inner diameter of the tube are 0.1 to 1 mm and 0.05 to 0.5 mm respectively, and the width and thickness of the plate are 0.1 to 1 mm and 0.1 to 0.2 mm respectively.

[0015] In step (3) of the additive manufacturing method for the aforementioned integrated load-sweating structure, the capillary sweating structure model constructed using three-dimensional software does not require setting the hole distribution and size in the structure, and the entire capillary sweating structure model is designed as a solid structure.

[0016] In step (4) of the additive manufacturing method for the aforementioned load-bearing-sweating integrated structure, the designed three-dimensional structural model is saved as an STL or 3MF file, and then the model file is split using splitting software.

[0017] In step (5) of the additive manufacturing method for the aforementioned integrated load-sweating structure, the substrate is preheated to 20-1200°C before forming, and the forming chamber is kept in an argon, nitrogen or vacuum atmosphere with an oxygen content of ≤0.1%.

[0018] In step (5) of the aforementioned additive manufacturing method for the integrated load-sweating structure, the additive manufacturing energy source is a laser or an electron gun.

[0019] In step (5) of the additive manufacturing method for the aforementioned integrated load-bearing and sweating structure, the additive manufacturing powder raw materials are titanium alloy, high-temperature alloy, refractory alloy, aluminum alloy, etc., and the powder particle size is controlled between 15 and 200 μm. The powder layer thickness is 20 to 150 μm.

[0020] In step (5) of the additive manufacturing method for the aforementioned integrated load-bearing and sweating structure, the additive manufacturing process parameters of the lattice load-bearing structure model are: laser power 120-450W, scanning speed 300-1600mm / s, spot diameter 0.08-0.2mm, and scanning spacing 0.08-0.2mm.

[0021] The contour process parameters are as follows: laser power 140-400W, scanning speed 300-1000mm / s, spot diameter 0.08-0.2mm, and scanning spacing 0.08-0.2mm; the internal solid structure process parameters are as follows: laser power 120-450W, scanning speed 600-1600mm / s, spot diameter 0.08-0.12mm, and scanning spacing 0.08-0.18mm.

[0022] The additive manufacturing process parameters for the capillary sweating structure model are: laser power 60-260W, scanning speed 800-2400mm / s, spot diameter 0.08-0.16mm, and scanning spacing 0.08-0.3mm.

[0023] In step (6) of the additive manufacturing method for the aforementioned load-bearing-sweating integrated structure, surface cleaning refers to using alcohol, acetone and other organic solvents to clean the oil stains and dirt off the surface of the part.

[0024] The aforementioned additive manufacturing method for the integrated load-bearing and sweating structure results in a final lattice load-bearing structure with a density ≥99.5% and a capillary sweating structure with a porosity between 10% and 50%.

[0025] Compared with existing technologies, this technical solution has the following advantages:

[0026] 1. Only the external dimensions of the integrated load-bearing and sweating component are needed for modeling. In the actual modeling process, the original model enveloping the component is filled with double-diagonal lattice structural elements as the load-bearing structure model, and a simple Boolean subtraction operation is performed to obtain the capillary sweating structure model. There is no need to directly design complex capillary structures. Therefore, the overall model processing computation is very small, the slicing requirements are low, and it is conducive to the rapid establishment and subdivision of the model.

[0027] 2. Based on extensive research into processes, microstructures, and properties, optimal ranges for many important parameters are further provided, such as: unit lattice structure type and dimensional parameters, energy density, scanning spacing, and layer thickness in additive manufacturing of capillary sweating structures. While meeting the load-bearing requirements of the unit lattice structure, the porosity of different parts can be flexibly adjusted by controlling the additive manufacturing process according to the differences in heat flux density between different parts of the load-bearing and sweating components, thus achieving stable and controllable adjustment of the sweating cooling capacity.

[0028] 3. The designed model rods, tubes, and plates have angles of 0°, 45°, 90°, 135°, etc., and can be directly printed by arranging the models without adding supports.

[0029] 4. There are no restrictions on the specific type and size of the unit lattice structure. The load-bearing capacity of the integrated load-bearing and sweating structure can be further improved through topology optimization design, process parameter optimization and other methods.

[0030] 5. It is applicable to, but not limited to, various commonly used metal sweating material systems, including nickel-based superalloys, titanium alloys, and cobalt-based superalloys. It is also suitable for various additive manufacturing processes such as laser additive manufacturing and electron beam additive manufacturing, and has strong versatility.

[0031] 6. The corresponding target product achieves the load-bearing requirements through a dot matrix load-bearing structure, and the capillary structure ensures the sweating and cooling capacity. It does not require metal powder pretreatment and complex post-printing processing, and can achieve rapid prototyping of complex load-bearing-sweat-integrated structures. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a double diagonal lattice structure unit of the present invention.

[0033] Figure 2 This is a model diagram of a double diagonal lattice load-bearing structural unit according to the present invention.

[0034] Figure 3 This is a model diagram of a capillary sweating structure according to the present invention.

[0035] Figure 4 This is a structural model diagram of a load-bearing and sweating integrated structure with a 2×2×2 unit arrangement. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 merely illustrative and not intended to limit the invention.

[0037] This embodiment discloses an additive manufacturing method for a load-bearing-sweating integrated structure, characterized by the following steps:

[0038] Step (1) Construct the space of the integrated structure envelope for bearing and sweating.

[0039] Step (2) fills the space enveloped in step (1) with the designed double diagonal lattice structural units to form the digital model of the lattice-supported structure, such as Figure 1 , Figure 2As shown. Note: The lattice structure includes, but is not limited to, a double-diagonal lattice structure. The size range of its lattice structure unit is 2-10 mm. The basic unit of the lattice structure consists of rods, tubes, or plates. The rod size is 0.1-1 mm, the outer diameter and inner diameter of the tube are 0.1-1 mm and 0.05-0.5 mm, respectively, and the width and thickness of the plate are 0.1-1 mm and 0.1-0.2 mm, respectively.

[0040] Step (3) performs a Boolean subtraction operation between the spatial envelope of the integrated load-bearing and sweating structure in step (1) and the lattice load-bearing structure model in step (2) to obtain the digital model of the capillary sweating structure. The capillary sweating structure digital model constructed using 3D software does not require setting the pore distribution and size in the structure; the entire capillary sweating structure digital model is designed as a solid structure. See [link to relevant documentation]. Figure 3 , Figure 4 .

[0041] Step (4) imports the lattice bearing structure model from step (2) and the capillary sweating structure model from step (3) into dedicated software for meshing, and sets different scanning strategies. The model in step (2) is set to a dense structure printing strategy, and the model in step (3) is set to a capillary structure printing strategy. The designed three-dimensional structure model is saved as an STL or 3MF file, and then the meshing software is used to mesh the model file. The energy source for additive manufacturing is a laser or an electron gun.

[0042] Step (5) The model after step (4) is introduced into the additive manufacturing equipment for additive manufacturing of the load-bearing-sweating integrated structure. Before forming, the substrate is preheated to 20-1200℃, and the forming chamber is kept in an argon, nitrogen or vacuum atmosphere with an oxygen content of ≤0.1%. The additive manufacturing powder raw materials are titanium alloy, high temperature alloy, refractory alloy, aluminum alloy and other powders, and the powder particle size is controlled at 15-200μm. The powder layer thickness is 20-150μm.

[0043] The additive manufacturing process parameters for the lattice load-bearing structure model are: laser power 120-450W, scanning speed 300-1600mm / s, spot diameter 0.08-0.2mm, and scanning spacing 0.08-0.2mm.

[0044] The contour process parameters are as follows: laser power 140-400W, scanning speed 300-1000mm / s, spot diameter 0.08-0.2mm, and scanning spacing 0.08-0.2mm; the internal solid structure process parameters are as follows: laser power 120-450W, scanning speed 600-1600mm / s, spot diameter 0.08-0.12mm, and scanning spacing 0.08-0.18mm.

[0045] The additive manufacturing process parameters for the capillary sweating structure model are: laser power 60-260W, scanning speed 800-2400mm / s, spot diameter 0.08-0.16mm, and scanning spacing 0.08-0.3mm.

[0046] After printing in step (6), wire cutting and surface cleaning are performed to obtain a sample of a dot matrix-capillary composite load-sweating integrated structure. Surface cleaning refers to using alcohol, acetone, and other organic solvents to clean oil stains and dirt from the surface of the parts.

[0047] The density of the final lattice load-bearing structure is ≥99.5%, and the porosity of the capillary sweating structure is between 10% and 50%.

[0048] The following section provides further details on this plan using specific materials, data, and experimental results:

[0049] Example 1:

[0050] An additive manufacturing method for a load-bearing and sweating integrated structure of 718 nickel-based superalloy specifically includes the following steps:

[0051] 1) Construct an envelope space model (20mm×20mm×20mm) with the same external dimensions as the integrated load-bearing and sweating component using CAD software.

[0052] 2) Fill the envelope space with double diagonal lattice structural units with unit dimensions of 10mm×10mm×10mm and rod diameter of 0.5mm to obtain the lattice load-bearing structure model.

[0053] 3) Perform Boolean subtraction between the envelope space model and the lattice bearing structure model to obtain the digital model of the capillary sweating structure.

[0054] 4) Save the lattice bearing structure model and the capillary sweating structure model as STL format respectively.

[0055] 5) Import the two STL format models into Magics Materialise model segmentation software for segmentation processing, with each slice having a thickness of 40μm.

[0056] 6) Import the split model into the Platinum A300 selective laser melting and forming equipment. The particle size range of the raw material 718 nickel-based high-temperature alloy powder is 15-53μm. The substrate preheating temperature is set to 20℃. Argon gas is filled into the forming chamber as a protective gas. Forming begins when the oxygen content drops below 300ppm.

[0057] 7) During the forming process, the lattice bearing structure model adopts high energy density to achieve densification. The scanning strategy for the dense solid contour is: laser power 150W, scanning speed 400mm / s, spot diameter 0.10mm, and scanning spacing 0.08mm; the scanning strategy for the internal solid structure is: laser power 300W, scanning speed 1300mm / s, spot diameter 0.10mm, and scanning spacing 0.08mm; the capillary sweating structure model adopts low energy density to achieve high porosity. The scanning strategy is: laser power 100W, scanning speed 1200mm / s, spot diameter 0.10mm, and scanning spacing 0.23mm.

[0058] 8) After the molding is completed, the substrate is removed by wire cutting, and the oil and dirt on the surface are cleaned with alcohol to obtain the lattice-capillary composite load-sweating integrated structure.

[0059] The compressive yield strength of the integrated load-bearing and sweating structure of this 718 nickel-based superalloy is 356 MPa, while the compressive yield strength of the capillary structure of the same size is 420 MPa, representing an increase of 64 MPa.

[0060] Example 2:

[0061] An additive manufacturing method for a load-bearing and sweating integrated structure of TC4 alloy specifically includes the following steps:

[0062] 1) Construct an envelope space model (10mm×10mm×10mm) with the same external dimensions as the integrated load-bearing and sweating component using CAD software;

[0063] 2) Fill the envelope space with double diagonal lattice structural units with unit dimensions of 5mm×5mm×5mm and rod diameter of 0.2mm to obtain the lattice load-bearing structure model;

[0064] 3) Perform Boolean subtraction between the envelope space model and the lattice bearing structure model to obtain the digital model of the capillary sweating structure;

[0065] 4) Save the lattice bearing structure model and the capillary sweating structure model as STL formats respectively;

[0066] 5) Import the two STL format models into Magics Materialise model segmentation software for segmentation processing, with each slice having a thickness of 50μm.

[0067] 6) Import the split model into the Platinum A300 selective laser melting and forming equipment. The particle size range of the raw material TC4 powder is 15-53μm. The substrate preheating temperature is set to 200℃. Argon gas is filled into the forming chamber as a protective gas. Forming begins when the oxygen content drops below 300ppm.

[0068] 7) During the forming process, the lattice bearing structure model adopts high energy density to achieve densification. The scanning strategy for the dense solid contour is: laser power 180W, scanning speed 1000mm / s, spot diameter 0.08mm, and scanning spacing 0.08mm; the scanning strategy for the internal solid structure is: laser power 200W, scanning speed 1500mm / s, spot diameter 0.08mm, and scanning spacing 0.08mm; the capillary sweating structure model adopts low energy density to achieve high porosity. The scanning strategy is: laser power 70W, scanning speed 1200mm / s, spot diameter 0.08mm, and scanning spacing 0.20mm.

[0069] 8) After the molding is completed, the substrate is removed by wire cutting, and the oil and dirt on the surface are cleaned with alcohol to obtain the lattice-capillary composite load-sweating integrated structure.

[0070] The TC4 alloy has a compressive yield strength of 305 MPa for its load-bearing-sweating integrated structure and 356 MPa for its capillary structure of the same size, representing an increase of 51 MPa.

[0071] The above embodiments are illustrative of the present invention and are not intended to limit the present invention. Any simple modifications to the methods, processes, structures, etc. of the present invention are within the protection scope of the present invention.

Claims

1. A method of additive manufacturing of a load-sweating integrated structure, characterized in that The method comprises the following steps: Step (1) constructing a space of a bearing-sweating integrated structure envelope; Step (2) filling the space of the envelope in step (1) with designed double-diagonal lattice structure units to form a numerical model of a lattice bearing structure; Step (3) performing a Boolean subtraction operation on the space of the bearing-sweating integrated structure envelope in step (1) and the numerical model of the lattice bearing structure in step (2) to obtain a numerical model of a capillary sweating structure; wherein the numerical model of the capillary sweating structure constructed by using a three-dimensional software is designed as a solid structure without setting the distribution and size of holes in the structure; Step (4) importing the numerical model of the lattice bearing structure in step (2) and the numerical model of the capillary sweating structure in step (3) into a software for slicing processing and setting different scanning strategies, wherein the model in step (2) is set as a printing strategy of a dense structure and the model in step (3) is set as a printing strategy of a capillary structure; Step (5) importing the sliced models in step (4) into an additive manufacturing device to perform additive manufacturing of the bearing-sweating integrated structure, printing the outline of the numerical model of the lattice bearing structure in step (2) first, and then printing the internal structure of the numerical model and the numerical model of the capillary sweating structure in step (3); Step (6) after printing, performing wire cutting and surface cleaning to obtain a lattice-capillary composite bearing-sweating integrated structure sample.

2. The additive manufacturing method of load-sweating integrated structure according to claim 1, characterized in that, In step (2), the lattice structure comprises a double-diagonal lattice structure, the size of the lattice structure unit ranges from 2 mm to 10 mm, and the basic unit of the lattice structure is composed of a rod, a tube or a plate, the size of the rod ranges from 0.1 mm to 1 mm, the outer diameter and the inner diameter of the tube range from 0.1 mm to 1 mm and from 0.05 mm to 0.5 mm respectively, and the width and the thickness of the plate range from 0.1 mm to 1 mm and from 0.1 mm to 0.2 mm respectively.

3. The additive manufacturing method of load-sweating integrated structure according to claim 1, wherein, In step (4), the designed three-dimensional structure model is saved as an STL or 3MF format file, and then the model file is sliced by using a slicing software.

4. The additive manufacturing method of load-sweating integrated structure according to claim 1, wherein, In step (5), before forming, the substrate is preheated to a temperature ranging from 20 ℃ to 1200 ℃, and the atmosphere in the forming cabin is argon, nitrogen or vacuum, and the oxygen content is controlled to be ≤0.1%.

5. The additive manufacturing method of load-sweating integrated structure according to claim 1, wherein, In step (5), the energy source of the additive manufacturing is a laser or an electron gun.

6. The additive manufacturing method of load-sweating integrated structure according to claim 1, characterized in that, In step (5), the powder raw material of the additive manufacturing is a titanium alloy or an aluminum alloy powder, and the particle size of the powder is controlled to range from 15 μm to 200 μm.

7. The additive manufacturing method of load-sweating integrated structure according to claim 1, characterized in that, In step (5), the additive manufacturing process parameters of the lattice bearing structure model are as follows: a laser power of 120 W to 450 W, a scanning speed of 300 mm / s to 1600 mm / s, a spot diameter of 0.08 mm to 0.2 mm, and a scanning interval of 0.08 mm to 0.2 mm; The additive manufacturing process parameters of the capillary sweating structure model are as follows: a laser power of 60 W to 260 W, a scanning speed of 800 mm / s to 2400 mm / s, a spot diameter of 0.08 mm to 0.16 mm, and a scanning interval of 0.08 mm to 0.3 mm.

8. The additive manufacturing method of load-sweating integrated structure according to claim 1, characterized in that, In step (6), the surface cleaning refers to cleaning the stains on the surface of the part by using an organic solvent.

9. The additive manufacturing method of load-sweating integrated structure according to claim 1, characterized in that, The density of the final shaped dot matrix bearing structure is ≥ 99.5%, and the porosity of the capillary sweating structure is between 10-50%.

Images