A laser additive manufacturing method for controllable adjustment of microstructure and performance

Abstract

This invention provides a laser additive manufacturing method with controllable microstructure and properties. The method includes: S1, melting a metal ingot to prepare a first powder; S2, preparing a second powder and performing a fluidized bed coating treatment, so that nano-ceramic particles are coated on the surface of the second powder in the form of nano-sized particles; S3, loading the first powder and the second powder into different powder feeding and dropping cylinders of a laser powder bed melting device; S4, selecting either the first powder or the second powder and spreading it onto the substrate of the laser powder bed melting device to form a monolayer powder bed; S5, performing laser scanning on the monolayer powder bed to melt and solidify it; repeating steps S4 and S5 until the component is formed. When processing components, the laser additive manufacturing method of this invention enables zoned controllable adjustment of microstructure and mechanical properties and reduces anisotropy.

Description

Technical Field

[0001] This invention relates to the field of laser additive manufacturing technology, and in particular to a laser additive manufacturing method with controllable adjustment of microstructure and properties. Background Technology

[0002] Laser powder bed fusion (LPBF) is a metal additive manufacturing technology based on the "discrete-stacking" principle, capable of forming high-precision, complex components. However, its molten pool temperature gradient is as high as 10°C. 6 The K / s ratio leads to the formation of a large number of columnar crystals inside the component, which not only produces significant anisotropy but also makes it difficult to control the microstructure and mechanical properties.

[0003] To address this issue, a multi-material LPBF process has been proposed in related technologies. This process achieves local performance adjustment by forming dissimilar materials. However, the interface between dissimilar materials is prone to forming brittle phases or stress concentration zones, which in turn leads to a decrease in the mechanical properties of the interface.

[0004] Therefore, in related technologies, columnar crystals dominate under single-material conditions, resulting in uncontrollable performance and strong anisotropy; although multi-material schemes can control performance in different areas, they sacrifice overall reliability due to interface problems, and cannot yet balance the controllable adjustment of microstructure and mechanical properties without interface defects. Summary of the Invention

[0005] This invention provides a laser additive manufacturing method with controllable microstructure and properties, which solves the defects of existing technologies such as columnar crystal dominance, high anisotropy and difficulty in controlling mechanical properties when forming single-material laser powder bed fusion, and the decline in mechanical properties due to heterogeneous interfaces in multi-material schemes. It achieves regional controllable adjustment of microstructure and mechanical properties and reduces anisotropy.

[0006] This invention provides a laser additive manufacturing method with controllable and adjustable microstructure and properties, comprising: S1. Melting metal ingots to prepare the first powder; S2. Prepare a second powder and perform fluidized coating treatment on it so that the nano-ceramic particles are coated on the surface of the second powder in the form of nano-sized particles. S3. The first powder and the second powder are respectively loaded into different powder feeding cylinders and powder dropping cylinders of the laser powder bed melting equipment; S4. According to preset requirements, select the first powder or the second powder and spread it onto the substrate of the laser powder bed melting equipment to form a single-layer powder bed; S5. Perform laser scanning on the single-layer powder bed to melt and solidify the single-layer powder bed into shape; Repeat steps S4 and S5 until the component is formed. The first powder forming region forms a columnar crystal structure, and the second powder forming region forms an equiaxed crystal structure.

[0007] In some embodiments, the method for preparing the second powder in S2 is as follows: melting the metal ingot and atomizing it to produce the second powder, and adding the nano-ceramic particles to perform fluidization coating treatment on the second powder.

[0008] In some embodiments, the method for preparing the second powder in S2 is as follows: removing the nano-ceramic particles from the metal ingot, melting the remaining metal ingot and atomizing it with gas to produce the second powder, and then using the removed nano-ceramic particles to perform fluidization coating treatment on the second powder.

[0009] In some embodiments, the particle size of the first powder and the second powder is 10 μm to 60 μm.

[0010] In some embodiments, S1 includes: The metal ingot is smelted to obtain liquid metal, which is then atomized into metal droplets using a gas atomization device. After the metal droplets solidify, they form spherical or planetary metal powder, which is used as the first powder.

[0011] In some embodiments, S5 includes keeping the process parameters used when performing laser scanning on the first powder and the second powder consistent.

[0012] In some embodiments, the laser powder bed melting apparatus includes: A laser is used to emit and focus a laser beam. A galvanometer is used to control the scanning path of the laser beam.

[0013] In some embodiments, the laser powder bed melting apparatus includes: A powder spreading roller is used to spread the first powder or the second powder onto the substrate.

[0014] In some embodiments, the laser powder bed melting apparatus includes: The first powder feeding cylinder is used to hold the first powder; The first powder-dropping cylinder, in conjunction with the first powder-feeding cylinder, supplies the first powder to the powder-spreading roller.

[0015] In some embodiments, the laser powder bed melting apparatus includes: The second powder feeding cylinder is used to hold the second powder; The second powder discharge cylinder, in conjunction with the second powder feeding cylinder, supplies the second powder to the powder spreading roller.

[0016] The laser additive manufacturing method for controllable microstructure and properties of this invention employs two powders with the same nominal composition but different surface states: the first powder retains the conventional composition, forming columnar crystals; the second powder has nano-ceramic particles coated on its surface, promoting the formation of equiaxed crystals. The identical chemical composition of both powders avoids brittle interfacial phases or stress concentration. By selectively layering the powder, a partitioned distribution of columnar and equiaxed crystals is achieved, thereby enabling controllable adjustment of microstructure and mechanical properties without introducing interfacial defects, and reducing anisotropy. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention 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 invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the laser additive manufacturing method with controllable microstructure and properties provided by the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of the laser powder bed melting equipment used in this invention.

[0020] Figure 3 This is a schematic diagram of the structure of a component processed using the laser additive manufacturing method of the present invention, which allows for controllable adjustment of microstructure and properties.

[0021] Figure 4 This is a schematic diagram of the microstructure of a component processed using the laser additive manufacturing method of the present invention, which allows for controllable adjustment of microstructure and properties.

[0022] Figure label: 1. Substrate; 2. Laser; 3. Galvanometer; 4. Powder spreading roller; 5. First powder feeding cylinder; 6. First powder dropping cylinder; 7. Second powder feeding cylinder; 8. Second powder dropping cylinder; 9. First powder forming area; 10. Second powder forming area; 11. Columnar crystal formed by first powder molding; 12. Equiaxed crystal formed by second powder molding. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0024] The following is combined with Figures 1 to 4 This invention describes a laser additive manufacturing method with controllable microstructure and properties.

[0025] like Figure 1 As shown, the laser additive manufacturing method with controllable microstructure and properties according to an embodiment of the present invention includes: S1. Melt metal ingots to prepare the first powder.

[0026] S2. Prepare a second powder and perform fluidized coating treatment on it so that the nano-ceramic particles are coated on the surface of the second powder in the form of nano-sized particles.

[0027] S3. The first powder and the second powder are respectively loaded into different powder feeding cylinders and powder dropping cylinders of the laser powder bed melting equipment.

[0028] S4. According to preset requirements, select the first powder or the second powder and spread it onto the substrate 1 of the laser powder bed melting equipment to form a single-layer powder bed.

[0029] S5. Laser scanning is performed on the single-layer powder bed to melt and solidify it.

[0030] Repeat steps S4 and S5 until the component is formed.

[0031] The first powder forming region 9 forms a columnar crystal structure, and the second powder forming region 10 forms an equiaxed crystal structure, so as to achieve regional controllable adjustment of the microstructure and mechanical properties of the component and reduce anisotropy.

[0032] The laser additive manufacturing method with controllable microstructure and performance in this embodiment of the invention uses two metal powders with the same nominal composition: the first powder is a conventional gas atomized powder that retains the ceramic-forming elements in the alloy; the second powder has nanoscale ceramic particles uniformly attached to its surface through a fluidized coating process.

[0033] The two powders have identical chemical compositions, avoiding compatibility issues arising from the interface of dissimilar materials. During the forming process, the first or second powder is selected layer by layer for powder spreading and laser melting according to design requirements. Because the nano-ceramic particles on the surface of the second powder can serve as effective heterogeneous nucleation sites, they promote the formation of equiaxed crystals under the same laser process parameters; while the first powder, lacking sufficient nucleation sites, tends to form columnar crystals. Thus, without changing the overall material composition, the spatial distribution control of columnar and equiaxed crystal regions is achieved by switching between powder types layer by layer.

[0034] The temperature gradient of the molten pool in laser powder bed melting is as high as 10. 6The K / s ratio leads to the formation of numerous columnar crystals within the component, resulting in significant anisotropy and making it difficult to control the microstructure and mechanical properties. To address this issue, related technologies have proposed multi-material LPBF processes, which achieve localized performance adjustment by forming dissimilar materials. However, the interfaces between dissimilar materials are prone to forming brittle phases or stress concentration zones, which in turn degrades the interfacial mechanical properties. Therefore, related technologies suffer from columnar crystal dominance, uncontrollable performance, and strong anisotropy under single-material conditions; while multi-material solutions can control performance in specific areas, they sacrifice overall reliability due to interface issues and cannot simultaneously achieve controllable adjustment of microstructure and mechanical properties without interface defects.

[0035] The laser additive manufacturing method for controllable microstructure and properties of this invention employs two powders with the same nominal composition but different surface states: the first powder retains the conventional composition, forming columnar crystals; the second powder has nano-ceramic particles coated on its surface, promoting the formation of equiaxed crystals. The identical chemical composition of both powders avoids brittle interfacial phases or stress concentration. By selectively layering the powder, a partitioned distribution of columnar and equiaxed crystals is achieved, thereby enabling controllable adjustment of microstructure and mechanical properties without introducing interfacial defects, and reducing anisotropy.

[0036] In some embodiments, the second powder is prepared in S2 by: melting a metal ingot and atomizing it to form a second powder, and then adding nano-ceramic particles to fluidize and coat the second powder.

[0037] In this embodiment, the matrix of the second powder is obtained by melting the same metal ingot as the first powder, and is prepared into spherical metal powder by gas atomization process; then the powder is placed in a fluidized bed device, and exogenous nano-ceramic particles (such as TiC, Y2O3, etc.) are introduced at the same time. Through fluidized coating treatment, the nano-ceramic particles are uniformly attached to the powder surface to form a composite powder with surface functionalization treatment.

[0038] The laser additive manufacturing method with controllable microstructure and properties of this invention introduces additional nano-ceramic particles on the surface of an alloy powder with complete composition. This not only preserves the chemical consistency of the original alloy system but also provides high-density heterogeneous nucleation sites during solidification, promoting the preferential formation of equiaxed crystals in the laser molten pool. Thus, the microstructure difference between the laser additive manufacturing method and the columnar crystal region can be controlled without changing the overall material composition.

[0039] In some embodiments, the second powder is prepared in S2 by: removing nano-ceramic particles from the metal ingot, melting the remaining metal ingot and atomizing it to form the second powder, and then using the removed nano-ceramic particles to perform fluidization coating treatment on the second powder.

[0040] In this embodiment, ceramic forming elements (such as Ti, B, C, etc.) are first removed from the original formula before melting, and only the remaining metal components are used to melt into an alloy ingot without ceramic phase. Then, pure metal powder is obtained by gas atomization. Subsequently, the ceramic forming elements that should have been present in the alloy are prepared separately in the form of nanoparticles and used as a coating phase to fluidize the pure powder so that the surface of the powder is loaded with the target ceramic components.

[0041] The laser additive manufacturing method with controllable microstructure and performance of the present invention uses the strategy of "removing ceramics from the inside and adding ceramics to the surface" to enable surface nanoparticles to play a role as controllable nucleation cores, thereby making the formation of equiaxed crystals more stable and maintaining the same composition as the first powder, thus eliminating the risk of interfacial compatibility.

[0042] In some embodiments, the particle size of the first powder and the second powder is 10 μm to 60 μm.

[0043] For example, the particle size of the first powder and the second powder is 10 μm, 30 μm or 60 μm.

[0044] In this embodiment, both powders are sieved or process-controlled to concentrate their particle size distribution within the range of 10μm to 60μm, which meets the requirements of laser powder bed melting for powder flowability and packing density. This is beneficial for forming a uniform and continuous single-layer powder bed and reducing powder gaps or agglomeration.

[0045] The laser additive manufacturing method with controllable microstructure and properties of the present invention adopts a uniform particle size range, making the first powder and the second powder comparable in terms of spreading behavior, laser absorption rate and molten pool dynamic response, thus providing a basis for driving different solidification structures based solely on differences in powder surface properties under the same process parameters.

[0046] In some embodiments, S1 includes: melting metal ingots to obtain liquid metal, using a gas atomizing device to atomize the liquid metal into metal droplets, and after the metal droplets solidify, forming spherical or planetary metal powder as a first powder.

[0047] In this embodiment, metal raw materials according to the target composition ratio are melted into a uniform liquid metal in a vacuum or inert atmosphere. Then, the liquid flow is impacted by a high-pressure inert gas (such as argon) to break it into micron-sized droplets. The droplets cool and solidify rapidly during the falling process to form spherical or planetary metal powder, which is collected and used as the first powder.

[0048] The laser additive manufacturing method with controllable microstructure and properties of this invention uses a standard gas atomization process to prepare a first powder that retains the ceramic forming elements in the alloy design. During the laser melting process, due to the lack of effective external nucleation sites, it tends to grow into columnar crystals along the heat flow direction, providing a reliable base material for constructing the microstructure contrast region.

[0049] In some embodiments, S5 includes keeping the process parameters used when laser scanning the first powder and the second powder consistent.

[0050] In this embodiment, during the entire process of layer-by-layer forming of the component, regardless of whether the first powder or the second powder is being laid, the key process parameters such as laser power, scanning speed, scanning spacing, and layer thickness remain unchanged, and the difference in the morphology is entirely determined by the physicochemical properties of the powder itself.

[0051] The laser additive manufacturing method with controllable microstructure and properties of this invention eliminates the interference of external energy input variables on the solidified structure by fixing the laser process parameters. This makes the difference between columnar crystals and equiaxed crystals clearly attributed to whether there are nano-ceramic particles on the powder surface, thereby enhancing the repeatability of the process and the reliability of the microstructure control.

[0052] In some embodiments, the laser powder bed melting apparatus includes a laser 2 and a galvanometer 3. The laser 2 is used to emit and focus a laser beam. The galvanometer 3 is used to control the scanning path of the laser beam.

[0053] In this embodiment, laser 2 generates high-energy continuous or pulsed laser light, which is focused onto the surface of the powder bed by an optical system to form a tiny spot; galvanometer 3 adjusts the incident angle of the laser beam, thereby precisely controlling its scanning trajectory on the substrate 1 to achieve melting of a single-layer powder bed.

[0054] In some embodiments, the laser powder bed melting equipment includes a powder spreading roller 4, which is used to spread a first powder or a second powder onto a substrate 1.

[0055] In this embodiment, the powder spreading roller 4 is installed above the substrate 1 and can move horizontally at the front edge of each layer forming. It evenly scrapes and lightly presses the powder falling from the powder drop cylinder onto the substrate 1 or the surface of the formed layer to form a single-layer powder bed with consistent thickness and uniform density. The material is usually tungsten carbide or ceramic to reduce wear.

[0056] In some embodiments, such as Figure 2 As shown, the laser powder bed melting equipment includes a first powder feeding cylinder 5 and a first powder dropping cylinder 6. The first powder feeding cylinder 5 is used to hold the first powder. The first powder dropping cylinder 6 cooperates with the first powder feeding cylinder 5 to supply the first powder to the powder spreading roller 4.

[0057] In this embodiment, the first powder feeding cylinder 5 is located on one side of the substrate 1 and stores the first powder inside. During the forming process, the first powder feeding cylinder 5 pushes a quantitative amount of powder upward to the first powder dropping cylinder 6 connected to it. The latter opens the valve to release the powder to the front of the powder spreading area for the powder spreading roller 4 to spread. After completing the single-layer powder supply, it resets.

[0058] The laser additive manufacturing method with controllable microstructure and performance of this invention realizes on-demand supply of columnar crystal forming materials through the first powder feeding cylinder 5 and the first powder dropping cylinder 6, supports the selective activation of the first powder at specific layers, and provides an actuator basis for spatial programming of microstructure.

[0059] In some embodiments, the laser powder bed melting apparatus includes a second powder feeding cylinder 7 and a second powder dropping cylinder 8. The second powder feeding cylinder 7 is used to hold a second powder. The second powder dropping cylinder 8 cooperates with the second powder feeding cylinder 7 to supply the second powder to the powder spreading roller 4.

[0060] In this embodiment, the second powder feeding cylinder 7 is disposed on the other side of the substrate 1 and is used to store the second powder that has undergone fluidized coating treatment; it is linked with the second powder dropping cylinder 8, and when it is necessary to form an equiaxed crystal region, it pushes the second powder to the powder dropping position and releases it in front of the powder spreading path, where it is spread by the powder spreading roller 4.

[0061] The laser additive manufacturing method with controllable microstructure and properties of this invention is configured with a second powder feeding cylinder 7 and a second powder dropping cylinder 8, so that the second powder can be called up in any designed layer, achieving precise positioning of the equiaxed crystal region and supporting the partitioned customized forming of the internal mechanical properties of the component.

[0062] The arrangement and thickness of the first and second powders can be set according to actual needs, for example, such as... Figure 3 As shown, the first powder forming area 9 and the second powder forming area 10 are arranged alternately.

[0063] The columnar crystals 11 formed by the first powder forming and the equiaxed crystals 12 formed by the second powder forming are as follows: Figure 4 As shown.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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 the present invention.

Claims

1. A laser additive manufacturing method with controllable and adjustable microstructure and properties, characterized in that, include: S1. Melting metal ingots to prepare the first powder; S2. Prepare a second powder and perform fluidized coating treatment on it so that the nano-ceramic particles are coated on the surface of the second powder in the form of nano-sized particles. S3. The first powder and the second powder are respectively loaded into different powder feeding cylinders and powder dropping cylinders of the laser powder bed melting equipment; S4. According to preset requirements, select the first powder or the second powder and spread it onto the substrate (1) of the laser powder bed melting equipment to form a single-layer powder bed; S5. Perform laser scanning on the single-layer powder bed to melt and solidify the single-layer powder bed into shape; Repeat steps S4 and S5 until the component is formed. The first powder forming region (9) forms a columnar crystal structure, and the second powder forming region (10) forms an equiaxed crystal structure.

2. The laser additive manufacturing method with controllable microstructure and properties according to claim 1, characterized in that, The method for preparing the second powder in S2 is as follows: melting the metal ingot and atomizing it to produce the second powder, and adding the nano-ceramic particles to perform fluidization coating treatment on the second powder.

3. The laser additive manufacturing method with controllable microstructure and properties according to claim 1, characterized in that, The method for preparing the second powder in S2 is as follows: removing the nano-ceramic particles from the metal ingot, melting the remaining metal ingot and atomizing it with gas to produce the second powder, and then using the removed nano-ceramic particles to perform fluidization coating treatment on the second powder.

4. The laser additive manufacturing method with controllable microstructure and properties according to claim 1, characterized in that, The particle size of the first powder and the second powder is 10μm~60μm.

5. The laser additive manufacturing method with controllable microstructure and properties according to claim 1, characterized in that, S1 includes: The metal ingot is smelted to obtain liquid metal, which is then atomized into metal droplets using a gas atomization device. After the metal droplets solidify, they form spherical or planetary metal powder, which is used as the first powder.

6. The laser additive manufacturing method with controllable microstructure and properties according to claim 1, characterized in that, S5 includes: keeping the process parameters used when performing laser scanning on the first powder and the second powder consistent.

7. The laser additive manufacturing method with controllable microstructure and properties according to claim 1, characterized in that, The laser powder bed melting equipment includes: Laser (2), used to emit and focus a laser beam; A galvanometer (3) is used to control the scanning path of the laser beam.

8. The laser additive manufacturing method with controllable microstructure and properties according to claim 1, characterized in that, The laser powder bed melting equipment includes: A powder spreading roller (4) is used to spread the first powder or the second powder on the substrate (1).

9. The laser additive manufacturing method with controllable microstructure and properties according to claim 8, characterized in that, The laser powder bed melting equipment includes: The first powder feeding cylinder (5) is used to hold the first powder; The first powder drop cylinder (6) cooperates with the first powder feeding cylinder (5) to supply the first powder to the powder spreading roller (4).

10. The laser additive manufacturing method with controllable microstructure and properties according to claim 8, characterized in that, The laser powder bed melting equipment includes: The second powder feeding cylinder (7) is used to hold the second powder; The second powder drop cylinder (8) cooperates with the second powder feeding cylinder (7) to supply the second powder to the powder spreading roller (4).

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