A laser additive manufacturing-based imitation nacreous pearl layer structure heterogeneous steel and a preparation method thereof

Abstract

The application belongs to the technical field of heterogeneous steel additive manufacturing, and particularly relates to a kind of heterogeneous steel based on laser additive manufacturing and a preparation method of shell-like nacreous layer structure, the shell-like nacreous layer structure heterogeneous steel includes multiple layers of bionic heterogeneous structure layer, each layer of bionic heterogeneous structure layer includes multiple shell-like nacreous layer structure unit bodies, each shell-like nacreous layer structure unit body includes four square modules, each square module includes two long rectangular martensite steel regions and two long rectangular austenite steel regions which are parallel to each other, long rectangular martensite steel regions and long rectangular austenite steel regions are arranged at intervals, the direction of long rectangular martensite steel regions and long rectangular austenite steel regions in any two adjacent square modules in each layer of bionic heterogeneous structure layer is perpendicular, and the direction of long rectangular martensite steel regions and long rectangular austenite steel regions in any two adjacent square modules in any two adjacent layers of bionic heterogeneous structure layer is perpendicular, and the application realizes the synergy of strength and toughness of material.

Description

Technical Field

[0001] This invention belongs to the field of heterogeneous steel additive manufacturing technology, specifically relating to a heterogeneous steel with a nacreous structure based on laser additive manufacturing and its preparation method. Background Technology

[0002] In recent years, the fabrication of heterostructured metallic materials using laser additive manufacturing has become a research hotspot. The unique spatial design and manufacturing flexibility of additive manufacturing allow for the combination of processing and custom-designed structures for heterostructured materials, thereby combining the superior properties of each constitutive material to improve overall performance. Furthermore, interfaces in multilayer metals play a crucial role in material properties such as strength, fracture, and work hardening. For example, interfaces can act as barriers to slip dislocations, improving yield strength, while flow strength increases primarily with decreasing individual layer thickness. Therefore, thinner layers or more interfaces are essential for improving performance.

[0003] Microscopically, the nacreous layer of seashells possesses a layered structure resembling a brick-and-mortar matrix. This structure consists of alternating layers of ductile organic matter (10–50 nm thick) and brittle aragonite flakes (200–900 nm thick). This layered structure is similar to the structure of pearlite in steel; the ductile organic matter layer corresponds to the soft ferrite within pearlite, while the brittle aragonite flake layer corresponds to the hard and brittle cementite. The alternating arrangement of these two layers contributes to improved overall mechanical properties. Through this nanoscale layered structure, the nacreous layer combines calcium carbonate (hard and brittle) and polymers (soft) into a heterogeneous material with excellent mechanical properties (high strength, high hardness, and high toughness). Its flexural strength can reach 190 MPa, and its fracture energy can reach 1240 J / m. 2 Compared to calcium carbonate aragonite, its strength is approximately twice as high, its hardness is approximately twice as high, and its fracture energy is approximately 3000 times higher.

[0004] Inspired by the unique structural features and excellent mechanical properties of nacre, many scholars have conducted research on heterogeneous materials with nacre-like structures. Most common nacre-like heterogeneous materials are prepared using methods such as ice template method, extrusion method, gel casting and hot pressing, and tape casting. However, their raw materials are mostly ceramic materials or metal-based ceramic composites, limiting their application range. For example, the journal *Acta Materialia*, Volume 59, page 10, 2009, reported the preparation of layered nacre-like Al2O3-PMMA composites using ice template technology, exhibiting both high strength and good toughness. However, the raw materials were limited by the method, preventing the preparation of heterogeneous metal materials, and the process was relatively complex. In recent years, scholars have studied the preparation of heterogeneous metal materials using additive manufacturing technology, but there are few reports on nacre-like heterogeneous metal materials, and their structures are relatively simple. For example, Chinese invention patent application CN112276294A, with publication date January 29, 2021, discloses a heterogeneous mesh structure layered composite material and its dual-wire electric arc additive manufacturing method. It discloses the preparation of heterogeneous mesh structure layered composite material using dissimilar metals as raw materials and electric arc additive manufacturing technology. This mesh structure is quite different from the nacreous structure of seashells.

[0005] Therefore, designing a layered structure that mimics the nacreous layer of seashells and using laser additive manufacturing technology to prepare a heterogeneous metal material with the mimicking nacreous layer structure has important practical value in both scientific research and industrial production. Summary of the Invention

[0006] The technical problem to be solved by this invention is to address the shortcomings of existing technologies by providing a heterogeneous steel with a shell-like nacre structure based on laser additive manufacturing and its preparation method. The preparation process of the shell-like nacre structure in this invention is simple and can give full play to the advantages of the shell nacre structure. The shell-like nacre structure heterogeneous steel provided by this invention has high strength and good toughness, achieving a synergistic effect of strength and toughness in the material.

[0007] This solution is achieved through the following technical measures: a biomimetic nacre structure heterogeneous steel based on laser additive manufacturing, comprising multiple biomimetic heterogeneous structure layers. Each biomimetic heterogeneous structure layer includes multiple biomimetic nacre structure units spread longitudinally and laterally. Each biomimetic nacre structure unit includes four square modules. Each square module includes two parallel rectangular martensitic steel regions and two rectangular austenitic steel regions. The two rectangular martensitic steel regions and the two rectangular austenitic steel regions are arranged alternately. The directions of the rectangular martensitic steel regions and the rectangular austenitic steel regions in any two adjacent square modules in each biomimetic heterogeneous structure layer are perpendicular. The directions of the rectangular martensitic steel regions and the rectangular austenitic steel regions in any two adjacent square modules in any two adjacent biomimetic heterogeneous structure layers are also perpendicular.

[0008] This invention also provides a method for preparing the above-mentioned heterostructured steel with a nacreous shell structure based on laser additive manufacturing, which includes the following steps:

[0009] (1) Based on the “brick-mud” layered structure of the nacreous layer of the shell, a biomimetic heterostructure design is carried out, a CAD model of the imitation nacreous layer structure is established, the layered contour data and deposition working path are obtained by using path planning software, the additive manufacturing position is determined, the position parameters are obtained, and then the data is imported into the laser deposition additive manufacturing equipment.

[0010] (2) Based on the compatibility of the physical and chemical properties of the materials, martensitic steel was selected as the "brick" of the imitation shell nacre structure, austenitic steel was selected as the "mud" of the imitation shell nacre structure, and 304 stainless steel plate was selected as the substrate.

[0011] (3) Based on the designed biomimetic heterostructure, directional energy deposition is performed using the set process parameters to deposit the shell-like nacreous layer structure heterostructure steel layer by layer:

[0012] (a) Deposit imitation shell nacre layer structure units in different regions to form a single-layer biomimetic heterostructure layer;

[0013] (b) Repeat step (a) on the basis of the previous biomimetic heterostructure layer to deposit the next biomimetic heterostructure layer. After the material of each biomimetic heterostructure layer is deposited, laser remelting is performed on each layer until the biomimetic heterostructure layer is deposited to obtain a shell nacre structure heterosteel.

[0014] (4) The imitation seashell nacre structure heterostructure steel is removed from the substrate by wire cutting or mechanical processing.

[0015] Preferably, the method for preparing the imitation seashell nacre structure unit in step (3) is as follows:

[0016] (i) Martensitic steel is deposited in regions a, b, c, and d in sequence according to the design order;

[0017] (ii) Austenitic steel is deposited sequentially in regions e, f, g, and h according to the design order;

[0018] (iii) Martensitic steel is deposited in regions i, j, k, and l in sequence according to the design order;

[0019] (iv) Austenitic steel is deposited in regions m, n, o, and p in sequence according to the design order.

[0020] Preferably, the raw materials for the rectangular martensitic steel region and the rectangular austenitic steel region are martensitic steel powder and austenitic steel powder.

[0021] Preferably, the particle size of the martensitic steel powder and the austenitic steel powder is 50-150 μm.

[0022] Preferably, the martensitic steel powder and austenitic steel powder need to be vacuum dried before use, with a drying temperature of 180°C and a holding time of 4 hours.

[0023] Preferably, the process parameters set in step (3) for directional energy deposition forming are: laser power of 350-550W, scanning speed of 300-420mm / min, powder feeding rate of 2-4g / min, and overlap rate of 35-45%.

[0024] Preferably, the process parameters used in the laser remelting in step (3) are: laser power of 100-150W and scanning speed of 480-540mm / min.

[0025] Preferably, during the directional energy deposition forming and laser remelting process, argon gas is required for powder feeding and protection, wherein the concentration of argon gas is 99.99% and the flow rate of argon gas is 8-12 L / min.

[0026] Preferably, the directional energy deposition forming process employs laser deposition additive manufacturing equipment, which has a dual-material bin to achieve alternating deposition forming of martensitic steel powder and austenitic steel powder.

[0027] The beneficial effects of the present invention are as follows: By constructing a layered structure that mimics the nacreous layer of a seashell and using laser additive manufacturing technology, the present invention can prepare heterogeneous metal materials with excellent comprehensive mechanical properties. The biomimetic nacre structure heterogeneous steel of this invention comprises multiple biomimetic heterogeneous structural layers. Each biomimetic heterogeneous structural layer includes multiple biomimetic nacre structure units spread longitudinally and laterally. Each biomimetic nacre structure unit includes four square modules. Each square module includes two parallel rectangular martensitic steel regions and two rectangular austenitic steel regions, which are arranged alternately. The directions of the rectangular martensitic steel regions and rectangular austenitic steel regions in any two adjacent square modules in each biomimetic heterogeneous structural layer are perpendicular. The directions of the rectangular martensitic steel regions and rectangular austenitic steel regions in any two adjacent square modules in any two adjacent biomimetic heterogeneous structural layers are also perpendicular. Moreover, the bonding surfaces of the soft and hard modules are regularly staggered. Under the action of tension, pressure, bending, impact, etc., this structure helps to prevent crack initiation and propagation. This composite structure has excellent comprehensive mechanical properties. This invention employs a laser remelting process to remelt the surface of each layer of dissimilar metal material, effectively reducing surface roughness and residual stress, minimizing defects such as porosity and cracks, increasing density, and improving the fatigue performance of the dissimilar metal material. Therefore, compared with existing technologies, this invention possesses outstanding substantive features and significant progress, and its beneficial effects are readily apparent. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the laser additive manufacturing process of the imitation seashell nacre structure heterogeneous steel in this invention.

[0029] Figure 2 This is a schematic diagram of the formation of a shell nacre structure unit.

[0030] Figure 3 This is a top view schematic diagram of a heterostructured steel with a nacreous structure resembling that of a seashell.

[0031] In the figure, 1-substrate, 2-martensitic steel region, 3-austenitic steel region, 4-laser deposition additive manufacturing equipment, 5-mimetic nacre structure unit. Detailed Implementation

[0032] To clearly illustrate the technical features of this solution, the following detailed implementation method, in conjunction with its accompanying drawings, will be used to describe the solution.

[0033] A type of biomimetic nacre structure heterogeneous steel based on laser additive manufacturing comprises multiple biomimetic heterogeneous structure layers. Each biomimetic heterogeneous structure layer includes multiple biomimetic nacre structure units 5 that are spread longitudinally and laterally. Each biomimetic nacre structure unit 5 includes four square modules. Each square module includes two parallel rectangular martensitic steel regions 2 and two rectangular austenitic steel regions 3. The two rectangular martensitic steel regions 2 and two rectangular austenitic steel regions 3 are arranged alternately. In any two adjacent square modules in each biomimetic heterogeneous structure layer, the directions of the rectangular martensitic steel regions 2 and rectangular austenitic steel regions 3 are perpendicular. In any two adjacent biomimetic heterogeneous structure layers, the directions of the rectangular martensitic steel regions 2 and rectangular austenitic steel regions 3 in the vertically adjacent square modules are also perpendicular.

[0034] This invention also provides a method for preparing the above-mentioned heterostructured steel with a nacreous shell structure based on laser additive manufacturing, which includes the following steps:

[0035] (1) Based on the “brick-mud” layered structure of the nacreous layer of the shell, a biomimetic heterostructure design is carried out, a CAD model of the imitation nacreous layer structure is established, the layered contour data and deposition working path are obtained by using path planning software, the additive manufacturing position is determined, the position parameters are obtained, and then the data is imported into the laser deposition additive manufacturing equipment 4.

[0036] (2) Based on the compatibility of the physical and chemical properties of the materials, martensitic steel was selected as the "brick" of the imitation shell nacre structure, austenitic steel was selected as the "mud" of the imitation shell nacre structure, and 304 stainless steel plate was selected as the substrate 1.

[0037] (3) Based on the designed biomimetic heterostructure, directional energy deposition was performed using the set process parameters to deposit the shell-like nacreous layer structure of heterostructured steel layer by layer. The set process parameters for directional energy deposition were: laser power of 350-550W, scanning speed of 300-420mm / min, powder feeding rate of 2-4g / min, and overlap rate of 35-45%.

[0038] (a) Deposit imitation shell nacre layer structure unit 5 in different regions to form a single-layer biomimetic heterostructure layer;

[0039] The preparation method of the simulated seashell nacre structure unit 5 is as follows:

[0040] (i) Martensitic steel is deposited in regions a, b, c, and d in sequence according to the design order;

[0041] (ii) Austenitic steel is deposited sequentially in regions e, f, g, and h according to the design order;

[0042] (iii) Martensitic steel is deposited in regions i, j, k, and l in sequence according to the design order;

[0043] (iv) Austenitic steel is deposited in regions m, n, o, and p in sequence according to the design order.

[0044] (b) Repeat step (a) on the basis of the previous biomimetic heterostructure layer to deposit the next biomimetic heterostructure layer. After the material of each biomimetic heterostructure layer is deposited, laser remelting is performed on each layer until the biomimetic heterostructure layer is deposited to obtain a shell-like nacreous layer structure heterostructure steel. The process parameters used for laser remelting are: laser power of 100-150W and scanning speed of 480-540mm / min.

[0045] During the directional energy deposition forming and laser remelting process, argon gas is required for powder feeding and protection. The concentration of the argon gas is 99.99%, and the flow rate of the argon gas is 8-12 L / min.

[0046] The directional energy deposition forming process employs laser deposition additive manufacturing equipment, which has a dual-feed chamber, enabling the alternating deposition forming of martensitic steel powder and austenitic steel powder.

[0047] (4) The imitation seashell nacre structure heterostructure steel is removed from the substrate by wire cutting or mechanical processing.

[0048] The raw materials for the rectangular martensitic steel region 2 and the rectangular austenitic steel region 3 are martensitic steel powder and austenitic steel powder. The particle size of the martensitic steel powder and austenitic steel powder is 50-150 μm. The martensitic steel powder and austenitic steel powder need to be vacuum dried before use at a temperature of 180°C for 4 hours.

[0049] In summary, the above-mentioned preparation method of the present invention involves establishing a CAD model of the simulated seashell nacre structure, obtaining layer contour data and deposition working path using path planning software, determining the additive manufacturing position, acquiring position parameters, and then importing the data into the laser deposition additive manufacturing equipment 4. Under a protective atmosphere, the simulated seashell nacre structure heterogeneous steel is deposited in different regions according to the sequence in step (3). Laser remelting is performed after each layer of material is deposited. Finally, the simulated seashell nacre structure heterogeneous steel is removed from the substrate by wire cutting or machining.

[0050] Technical features not described in this invention can be implemented using existing technologies and will not be elaborated upon here. This invention is not limited to the specific embodiments described above; any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of this invention should also fall within the protection scope of this invention.

Claims

1. A method for preparing a shell-like nacre-structured heterostructured steel based on laser additive manufacturing, characterized in that, The biomimetic nacre structure heterogeneous steel based on laser additive manufacturing includes multiple biomimetic heterogeneous structure layers. Each biomimetic heterogeneous structure layer includes multiple biomimetic nacre structure units (5) that are spread longitudinally and laterally. Each biomimetic nacre structure unit (5) includes four square modules. Each square module includes two parallel rectangular martensitic steel regions (2) and two rectangular austenitic steel regions (3). The two rectangular martensitic steel regions (2) and two rectangular austenitic steel regions (3) are arranged alternately. The directions of the rectangular martensitic steel regions (2) and rectangular austenitic steel regions (3) in any two adjacent square modules in each biomimetic heterogeneous structure layer are perpendicular. The directions of the rectangular martensitic steel regions (2) and rectangular austenitic steel regions (3) in any two adjacent square modules in any two adjacent biomimetic heterogeneous structure layers are perpendicular. The preparation method of the imitation seashell nacre structure heterostructure of heterostructure steel based on laser additive manufacturing includes the following steps: (1) Based on the "brick-mud" layered structure of the nacreous shell, a biomimetic heterostructure design is carried out, a CAD model of the nacreous shell structure is established, the layered contour data and deposition working path are obtained by using path planning software, the additive manufacturing position is determined, the position parameters are obtained, and then the data is imported into the laser deposition additive manufacturing equipment (4). (2) Based on the compatibility of the physical and chemical properties of the materials, martensitic steel was selected as the "brick" of the imitation shell nacre structure, austenitic steel was selected as the "mud" of the imitation shell nacre structure, and 304 stainless steel plate was selected as the substrate (1). (3) Based on the designed biomimetic heterostructure, directional energy deposition is performed using the set process parameters to deposit the shell-like nacreous layer structure heterostructure steel layer by layer: (a) Deposit shell-like nacreous layer structural units in different regions (5) to form a single-layer biomimetic heterostructure layer; (b) Repeat step (a) on the basis of the previous biomimetic heterostructure layer to deposit the next biomimetic heterostructure layer. After the material of each biomimetic heterostructure layer is deposited, laser remelting is performed on each layer until the biomimetic heterostructure layer is deposited to obtain a shell nacre structure heterosteel. (4) The imitation seashell nacre structure heterostructure steel is removed from the substrate by wire cutting or mechanical processing.

2. The preparation method according to claim 1, characterized in that, The preparation method of the imitation seashell nacre structure unit (5) in step (3) is as follows: (i) Martensitic steel is deposited in regions a, b, c and d as shown in Figure 2 in the order of design. (ii) Following the design sequence, austenitic steel is deposited sequentially in regions e, f, g, and h as shown in Figure 2; (iii) Martensitic steel is deposited sequentially in regions i, j, k, and l as shown in Figure 2, according to the design sequence; (iv) Austenitic steel is deposited in regions m, n, o and p as shown in Figure 2 in sequence according to the design order.

3. The preparation method according to claim 2, characterized in that, The raw materials for the rectangular martensitic steel region (2) and the rectangular austenitic steel region (3) are martensitic steel powder and austenitic steel powder.

4. The preparation method according to claim 2, characterized in that, The particle size of the martensitic steel powder and the austenitic steel powder is 50~150 μm.

5. The preparation method according to claim 2, characterized in that, The martensitic steel powder and austenitic steel powder need to be vacuum dried before use. The drying temperature is 180℃ and the holding time is 4 hours.

6. The preparation method according to claim 2, characterized in that, The process parameters set in step (3) for directional energy deposition are: laser power of 350~550 W, scanning speed of 300~420 mm / min, powder feeding rate of 2~4 g / min, and overlap rate of 35~45%.

7. The preparation method according to claim 2, characterized in that, The process parameters used in step (3) for laser remelting are: laser power of 100~150 W and scanning speed of 480~540 mm / min.

8. The preparation method according to claim 2, characterized in that, during the directional energy deposition forming and laser remelting process, argon gas is required for powder feeding and protection, wherein the concentration of argon gas is 99.99% and the flow rate of argon gas is 8~12 L / min.

9. The preparation method according to claim 2, characterized in that, The directional energy deposition forming process employs laser deposition additive manufacturing equipment, which has a dual-material bin to achieve alternating deposition forming of martensitic steel powder and austenitic steel powder.

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