A method for forming spatial heterogeneous structures by laser powder bed fusion

Abstract

The present invention discloses a method for forming spatial heterogeneous structures by laser powder bed melting, which relates to the field of laser additive manufacturing, and includes the following steps: Step 1: the powder cylinder is divided into several areas by an elastic plate, and the types of powders in the several areas are different, wherein the setting direction of the elastic plate is parallel to the movement direction of the scraper; Step 2: the powder in step 1 is scraped onto the substrate in the forming cylinder by the scraper; Step 3: the powder in step 2 is melted / solidified by laser to complete a layer of printing; Step 4: the powder cylinder rises by a powder supply amount, and the forming cylinder drops by a layer thickness, and steps 2 and 3 are repeated to complete N layers of printing. An elastic plate parallel to the movement direction of the scraper is added to the powder cylinder, and the forming cylinder rotates around the axis to obtain a spatial heterogeneous complex forming structure. The method of the present invention does not require an additional powder cylinder, and can overcome the problem of powder falling and powder blocking in the funnel in the existing heterogeneous material powder spreading equipment. The forming process is simple, and the forming process is stable and reliable.

Description

Technical Field

[0001] The invention relates to the field of laser additive manufacturing, and in particular to a method for forming a spatial heterogeneous structure by laser powder bed melting. Background Art

[0002] Traditional metal structures are composed of homogeneous materials with single performance. However, as the service environment of components becomes increasingly harsh, the same component not only requires two or more properties, but also different parts need to have different functions. Therefore, traditional single materials can no longer meet the actual needs of industrial production for comprehensive material performance. Heterogeneous materials can combine the performance characteristics of different materials to achieve locally customized performance and functions, so that components can adapt to extreme service environments (ultra-high temperature, high pressure, etc.), and meet the development direction of lightweight, performance / functional integration, and intelligence of complex aerospace components.

[0003] Laser Additive Manufacturing (LAM) has the process characteristics of integrating "material preparation" and "component forming", providing a technical approach for heterogeneous material forming. Based on the LAM process, suitable materials can be distributed in suitable positions, and different material layouts can be realized on the same component, achieving the goal of "using good steel on the blade", realizing active regulation of the performance / function of metal components, and significantly improving structural efficiency.

[0004] The powder-feeding laser directed energy deposition technology can easily realize heterogeneous material forming through the coordinated action of multiple powder barrels, but its forming accuracy is not high and it is impossible to prepare complex and precise structural components. The powder-spreading laser powder bed melting technology has significant advantages in the forming of precise and complex components. However, it is not easy to freely distribute the required heterogeneous materials as needed during the forming process due to the principle of spreading powder, and it is ultimately difficult to freely manufacture heterogeneous material components. When preparing heterogeneous materials based on the existing laser powder bed melting technology, multiple powder barrels are set in the forming cavity, or multiple funnels are used for gravity powder dropping, or multiple scrapers are used for powder spreading. The above method not only occupies the forming cavity space, but also increases the equipment cost and reduces the forming efficiency; in addition, the multi-funnel powder dropping method is also prone to problems such as powder blockage. The existing Chinese patent CN114799229A proposes a spiral powder feeding method and device for selective laser melting forming of heterogeneous materials. The method is achieved by having a branch powder feeding function and multiple powder feeders with double helix structure characteristics. Although the above method can accurately control different powders, it can only prepare interlayer heterogeneous materials and still cannot achieve the required distribution within the heterogeneous material layer. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for forming spatial heterogeneous structures by laser powder bed melting. An elastic plate parallel to the movement direction of the scraper is added to the powder cylinder, and the forming cylinder is rotated around the Z-axis of the centroid of the structure to obtain a spatial heterogeneous complex forming structure. The method of the present invention does not require an additional powder cylinder, and can overcome the problem of powder falling and powder blockage in the existing heterogeneous material powder spreading equipment. The forming process is simple, and the forming process is stable and reliable.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] A method for forming a spatial heterogeneous structure by laser powder bed melting, comprising the following steps:

[0008] Step 1: The powder cylinder is divided into several areas by an elastic plate, and the types of powder in the several areas are different, wherein the setting direction of the elastic plate is parallel to the movement direction of the scraper;

[0009] Step 2: Scrape the powder in step 1 onto the substrate in the forming cylinder using a scraper;

[0010] Step 3: Use laser to melt / solidify the powder in step 2 to complete a layer of printing;

[0011] Step 4: The powder cylinder rises by one powder supply amount, and the forming cylinder drops by one layer thickness. Repeat steps 2 and 3 to complete N-layer printing.

[0012] In the above scheme, after step 4 is completed, metal components with different spatial heterogeneous structures can be obtained by rotating the forming cylinder.

[0013] In the above scheme, the rotation angle α of the forming cylinder ranges from 0 to 360°.

[0014] In the above solution, the thickness of the elastic plate is 0.2-0.5 mm, and the spacing between adjacent elastic plates is 0.5-10 mm.

[0015] In the above scheme, the powder sphericity is >90%, the purity is >99.9%, and the particle size is 5 to 50 μm.

[0016] In the above scheme, the laser spot diameter is 70 μm, the laser power is 50-500 W, the scanning speed is 200-3000 mm / s, and a zigzag, orthogonal, chessboard or scanning strategy is adopted, with a scanning spacing of 30-100 μm.

[0017] In the above scheme, when the oxygen content in the forming cylinder cavity does not exceed 20ppm, the laser is turned on, and the substrate preheating function is turned on to raise the substrate temperature to 150°C. The laser melts the powders in different forming cylinders according to path planning.

[0018] In the above scheme, the scraper is arranged above the powder cylinder, and the scraper moves downward according to the set vertical feed amount and then scrapes the powder along a predetermined track.

[0019] In the above scheme, the powder layer on the forming cylinder is 30 to 50 μm thick.

[0020] In the above scheme, the powder supply amount in the powder cylinder is 1 to 3 times the thickness of the powder layer in the forming cylinder.

[0021] Beneficial effects:

[0022] 1. The present invention only needs to add an elastic plate to the powder cylinder and rotate the forming cylinder around the centroid Z axis of the structure, so that different materials can be freely distributed in different layers and in different areas between layers as needed, thereby realizing the forming of spatial heterogeneous complex structures. The method is simple and the processing efficiency is high.

[0023] 2. The present invention does not require an additional powder tank, thus reducing the use cost. At the same time, it can overcome the problems of powder sticking and unstable process caused by the multi-funnel gravity powder dropping method during the powder spreading and forming process of heterogeneous materials.

[0024] 3. The spatial heterogeneous structure prepared by the method of the present invention has high forming accuracy and density, has good forming quality, and can be applied to the printing of various complex structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of a method for forming a spatial heterogeneous structure by laser powder bed melting according to an embodiment of the present invention;

[0026] Figure 2 It is a schematic diagram of the cooperation among the scraper, the powder cylinder and the elastic plate;

[0027] Figure 3 It is a schematic diagram of the forming cylinder rotating around the Z axis of the component centroid;

[0028] Figure 4 Schematic diagram of heterogeneous material obtained according to the method of the present invention Figure 1 ;

[0029] Figure 5 Schematic diagram of heterogeneous material obtained according to the method of the present invention Figure 2 .

[0030] Reference numerals:

[0031] 1- elastic plate; 2- material A; 3- material B; 4- material C; 5- material D; 6- material E. DETAILED DESCRIPTION

[0032] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0033] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the present invention, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", "fix" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0034] A method for forming a spatial heterogeneous regular structure by laser powder bed melting, comprising the following steps:

[0035] Step 1: multiple elastic plates are arranged in the powder tank according to the shape and size of the component. The placement direction of the elastic plates is parallel to the movement direction of the scraper. Different powders can be poured into the space between adjacent elastic plates, so that a variety of heterogeneous materials are distributed in a two-dimensional plane;

[0036] Step 2: Scrape the powder in step 1 to the forming cylinder through a powder scraping device to spread the powder evenly on the substrate;

[0037] Step 3: Melt / solidify the powder in step 2 based on laser powder bed fusion technology to complete a layer of printing;

[0038] Step 4: The powder cylinder rises by one powder supply amount, and the forming cylinder drops by one layer thickness. Repeat the above steps 2 and 3 to complete N-layer printing;

[0039] Step 5: According to the structural characteristics of the metal component, after the end of step 4, the forming cylinder rotates around the Z axis of the centroid of the metal component by an angle α;

[0040] Step 6: Repeat the above steps 5-6 until the spatial heterogeneous structure processing is completed.

[0041] Among them, in step one, the number of types of filled heterogeneous materials shall not exceed the number of elastic plates + 1; the elastic plates have deformation ability, the thickness of the elastic plates is 0.2-0.5mm, the spacing between the elastic plates is 0.5-10mm, and they can be arranged at unequal spacings; the sphericity of the heterogeneous powder is >90%, the purity is >99.9%, and the particle size is 5-50μm, so that the powder has better fluidity.

[0042] Among them, in step 2, the elastic plate will descend in an orderly manner when the powder scraping device scrapes the powder; the type of substrate is selected according to the principle of similarity of heterogeneous material components, that is, the components of the printed components are composed of the above-mentioned heterogeneous materials, and the contents of different components are similar.

[0043] Among them, in step three, in different elastic plate spaces, due to different materials' different laser absorption rates and forming characteristics, different materials need to select the laser processing parameters with the best formability for printing (spot diameter is 70μm, laser power is 50-500W, scanning speed is 200-3000mm / s, multiple scanning strategies such as zigzag, orthogonal, chessboard, and remelting are adopted, the powder layer thickness is 30-50μm, and the scanning spacing is 30-100μm). In order to isolate the oxygen in the cavity and prevent the components from having pores, and to blow away the heat of the current forming layer, the protective gas needs to be continuously introduced during the forming process.

[0044] Among them, in step four, when the oxygen content in the forming cavity is lower than 20ppm, turn on the laser; set the powder supply to 3 times the powder layer thickness to ensure smooth powder spreading; at the same time, in order to reduce the temperature gradient between the substrate and the previous layers, turn on the substrate preheating function to preheat it. When the substrate temperature rises to 150°C, the laser melts different powders according to path planning.

[0045] Among them, in step 5, the rotation angle of the forming cylinder around the Z axis of the component centroid is between 0 and 360°. After adding the elastic plate, heterogeneous distribution has been achieved in the layer, so when the component is a regular spatial structure, the forming cylinder does not need to rotate; when the component is a spatial spiral or other irregular structure, the forming cylinder needs to rotate around the Z axis, and the rotation angle is greater than 0°; rotate once after each N layers are printed until the spatial heterogeneous structure is formed.

[0046] Example 1

[0047] As shown in the accompanying drawings, a method for forming a spatial heterogeneous regular structure by laser powder bed melting includes the following steps:

[0048] Step 1: Add two elastic plates 1 in the powder tank parallel to the movement direction of the scraper according to the shape and size of the component, and pour titanium alloy, aluminum alloy and nickel-based alloy powders into the spaces divided by different elastic plates 1, so that a variety of heterogeneous materials are distributed in the same plane;

[0049] Step 2: A customized substrate is installed in the forming cylinder, wherein the components of the substrate are Al, Ti, and Fe, and the contents of the three elements are similar. The three kinds of powders (sphericity>90%, purity>99.9%, and particle size of 5-50μm) in the powder cylinder are scraped into the forming cylinder by a powder scraping device, so that the powder is evenly spread on the substrate; when scraping the powder, the elastic thin plate 1 can descend in an orderly manner;

[0050] Step 3: When the oxygen content in the forming chamber is lower than 20ppm, the substrate preheating function is turned on. When the substrate preheating temperature is 150°C, the three powders are melted / solidified based on the laser powder bed fusion technology to complete a layer of printing;

[0051] Based on the optimized process parameters, the three powders all adopted the partitioned island scanning strategy, with the layer thickness set to 30μm and the scanning spacing set to 50μm; the laser power for aluminum alloy was 400W and the scanning speed was 3000mm / s; the laser power for titanium alloy was 350W and the scanning speed was 2000mm / s; the nickel-based alloy was 300W and 1000mm / s;

[0052] Step 4: After one layer of printing is completed, the powder cylinder rises 90μm and the forming cylinder drops 30μm. Repeat step 4 for 100 layers until the component printing is completed.

[0053] Attached Figure 4 This is the spatial heterogeneous structure obtained after printing in Example 1, wherein the left side is a nickel-based alloy, the middle is an aluminum alloy, and the right side is a titanium alloy.

[0054] Example 2

[0055] The difference between Example 2 and Specific Example 1 is that after forming every 30 layers, the forming cylinder is rotated 30° around the Z axis of the forming cylinder; the rotation is repeated 3 times until the component printing is completed, and the other steps are the same as Example 1.

[0056] Attached Figure 5 This is the spatial heterogeneous structure obtained in Example 2.

[0057] Table 1 Parameters of the spatial heterogeneous structures obtained in Examples 1 and 2

[0058] structure Density(%) Dimensional accuracy 1 99.8 ±0.08mm 2 99.6 ±0.1mm

[0059] Table 1 shows the density and dimensional accuracy of the two structures formed by laser powder bed fusion. The density of the spatial heterogeneous structure in Example 1 is 99.8%, and the dimensional accuracy is ±0.08 mm; the density of the spatial heterogeneous structure in Example 2 is 99.6%, and the dimensional accuracy is ±0.1 mm. Therefore, the spatial heterogeneous structure prepared according to the method of the present invention has high forming accuracy and density, has good forming quality, and can be applied to the printing of various complex structures.

[0060] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0061] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for forming spatial heterogeneous structures by laser powder bed melting, characterized in that: The method comprises the following steps: step 1: the powder cylinder is divided into several areas by an elastic plate, and the types of powders in the several areas are different, wherein the setting direction of the elastic plate is parallel to the movement direction of the scraper; step 2: the powder in step 1 is scraped onto the substrate in the forming cylinder by the scraper; step 3: the powder in step 2 is melted / solidified by a laser to complete a layer of printing; step 4: the powder cylinder rises by a powder supply amount, and the forming cylinder drops by a layer thickness, and steps 2 and 3 are repeated to complete N layers of printing; after step 4, metal components with different spatial heterogeneous structures can be obtained by rotating the forming cylinder; the thickness of the elastic plate is 0.2-0.5 mm, and the spacing between adjacent elastic plates is 0.5-10 mm; the powder supply amount in the powder cylinder is 1-3 times the powder layer thickness in the forming cylinder.

2. The method for forming spatial heterogeneous structures by laser powder bed melting according to claim 1, characterized in that: The rotation angle α of the forming cylinder ranges from 0 to 360°.

3. The method for forming spatial heterogeneous structures by laser powder bed melting according to claim 1, characterized in that: The powder sphericity is >90%, the purity is >99.9%, and the particle size is 5-50μm.

4. The method for forming spatial heterogeneous structures by laser powder bed melting according to claim 1, characterized in that: The laser spot diameter is 70 μm, the laser power is 50-500 W, the scanning speed is 200-3000 mm / s, and a zigzag, orthogonal, chessboard or scanning strategy is adopted, with a scanning spacing of 30-100 μm.

5. The method for forming spatial heterogeneous structures by laser powder bed melting according to claim 1, characterized in that: When the oxygen content in the forming cylinder cavity does not exceed 20ppm, the laser is turned on, and the substrate preheating function is turned on to raise the substrate temperature to 150°C. The laser melts the powder in different forming cylinders according to path planning.

6. The method for forming spatial heterogeneous structures by laser powder bed melting according to claim 1, characterized in that: The scraper is arranged above the powder cylinder, and the scraper scrapes the powder along a predetermined track after descending according to the set vertical feed amount.

7. The method for forming spatial heterogeneous structures by laser powder bed melting according to claim 1, characterized in that: The powder layer on the forming cylinder is 30 to 50 μm thick.

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