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CN-122007441-A - Method for preparing layered structure by laser powder bed layer-by-layer remelting technology

CN122007441ACN 122007441 ACN122007441 ACN 122007441ACN-122007441-A

Abstract

The invention provides a method for preparing a layered structure by a laser powder bed layer-by-layer remelting technology, which comprises the following steps of S1, paving a layer of metal powder on a substrate of laser selective melting equipment, carrying out laser melting on the layer of metal powder to form a substrate layer, S2, carrying out laser line remelting on a specific area on the substrate layer, wherein the area of the specific area is smaller than the area of the layer of metal powder subjected to laser melting, S3, paving a layer of metal powder on the substrate layer again after remelting, and repeatedly executing the step S1 and the step S2 until printing is completed to obtain the layered structure. The invention induces differentiated solid phase transformation and grain growth behaviors in situ in the same powder layer, thereby constructing the ferrite-austenite layered composite stainless steel material with complex three-dimensional configuration.

Inventors

  • ZHENG LIUWEI
  • WANG XUDONG
  • ZHONG BOWEN
  • WANG LIFEI
  • WANG HONGXIA
  • NIU XIAOFENG

Assignees

  • 太原理工大学

Dates

Publication Date
20260512
Application Date
20260303

Claims (8)

  1. 1. A method for preparing a layered structure by a laser powder bed layer-by-layer remelting technology is characterized by comprising the following steps: S1, laying a layer of metal powder on a substrate of laser selective melting equipment, and carrying out laser melting on the layer of metal powder to form a substrate layer; s2, carrying out laser wire remelting on a specific area on the substrate layer, wherein the area of the specific area is smaller than the area of the metal powder laser melting of the layer; s3, after remelting, paving a layer of metal powder on the substrate layer, and repeatedly executing the step S1 and the step S2 until printing is completed, so as to obtain the layered structure; The microstructure of the layered structure is characterized in that the microstructure of the region which is not remelted by the laser line is composed of ferrite with a BCC crystal structure and austenite with an FCC crystal structure, and crystal grains are equiaxed crystals, and the microstructure of the region which is remelted by the laser line is composed of ferrite with a single BCC crystal structure, and the crystal grains are columnar crystals.
  2. 2. The method for preparing the layered structure by using the laser powder bed layer-by-layer remelting technology as claimed in claim 1, wherein the laser melting process is characterized in that a scanning strategy is a checkerboard, the scanning power is 150-270W, the scanning speed is 800-1500 mm/s, the scanning interval is 0.1mm, the layer thickness is 30 μm, the rotation angle between layers is 67 degrees, and the diameter of a laser beam is 100 μm.
  3. 3. The method for preparing the layered structure by using the laser powder bed layer-by-layer remelting technology according to claim 1, wherein the laser line remelting technology is characterized in that the scanning strategy is parallel lines, the scanning power is 100-350W, the scanning speed is 800-2000 mm/S, the scanning interval is 0.2-0.3 mm, the rotation angle between layers is 0-360 degrees, the laser beam diameter is 100 mu m, and in the step S2, the number of times of laser line remelting on the specific area is 1-3 times.
  4. 4. The method for preparing the layered structure by the laser powder bed layer-by-layer remelting technology according to claim 1, wherein the 430 stainless steel powder is in a regular spherical shape, the grain size distribution is in a range of 15-53 μm, the chemical components of the 430 stainless steel powder comprise 16.85% of Cr, 0.97% of Mn, 0.66% of Si, the balance of Fe and unavoidable impurities in percentage by mass, the 316L stainless steel powder is in a regular spherical shape, the grain size distribution is in a range of 15-53 μm, the chemical components of the 316L stainless steel powder comprise 17.94% of Cr, 12.01% of Ni, 2.15% of Mo, 0.39% of Si, 0.006% of Mn, the balance of Fe and unavoidable impurities in percentage by mass, and the chemical components of the mixed powder comprise 16.9-17.5% of Cr, 6.9-7.21% of Ni, 0.98-1.29% of Mo, 0.25-0.39% of Mn, 0.3-0.498% of Si and the balance of Fe and unavoidable impurities in percentage by mass.
  5. 5. The method for preparing the layered structure by using the laser powder bed layer-by-layer remelting technology as claimed in claim 1, wherein the environment parameters of the laser selective melting equipment are that the preheating temperature of the substrate is 80+/-5 ℃, the protective atmosphere is argon, and the oxygen content is not higher than 0.8vol%.
  6. 6. The method for preparing a layered structure by using the laser powder bed layer-by-layer remelting technique as set forth in claim 1, wherein the specific region changes in shape layer by layer, and the scanning power, scanning speed, scanning pitch and rotation angle between layers are the same or different for each laser line remelting when step S2 is performed a plurality of times.
  7. 7. The method for preparing a layered structure by using the laser powder bed layer-by-layer remelting technology as set forth in claim 1, wherein the specific areas in the plurality of layers of the metal powder are periodically and alternately arranged in a three-dimensional space, so that the prepared layered structure is macroscopically represented by a composite configuration in which ferrite columnar crystal areas and biphasic equiaxed crystal areas are alternately laminated.
  8. 8. The method of claim 1, wherein the grain size, grain orientation and element distribution of the specific region in the different powder layers are graded by changing at least one of a scanning power, a scanning speed and a scanning pitch of laser line remelting of the specific region layer by layer during layer printing.

Description

Method for preparing layered structure by laser powder bed layer-by-layer remelting technology Technical Field The invention relates to the technical field of additive manufacturing of metal materials, in particular to a method for preparing a layered structure by a laser powder bed layer-by-layer remelting technology. Background The layered structure metal material has wide application prospect in the high-end manufacturing fields of aerospace, nuclear energy equipment, ocean engineering, biomedical treatment and the like because the layered structure metal material can integrate the excellent performances of materials with different phases or different components. For example, ferritic stainless steel (such as 430 stainless steel) has excellent stress corrosion resistance and heat conduction performance, while austenitic stainless steel (such as 316L stainless steel) has excellent plastic toughness and welding performance, and the layered structure material formed by compounding the two is expected to realize the cooperative improvement of strength, toughness and corrosion resistance. However, the conventional lamellar structure preparation technology, such as physical/chemical methods of rolling compounding, explosion compounding, casting compounding and the like, has at least the technical defects of high process cost, large-scale special equipment and complex pretreatment procedures, difficulty in preparing three-dimensional components with complex geometric shapes, usually limited to simple plate compounding, low production efficiency, multi-pass rolling or long-time diffusion annealing, easiness in occurrence of defects of oxide inclusion, segregation or non-welding and the like at a prepared lamellar interface, and serious influence on the overall performance and reliability of the material. In recent years, the laser powder bed melting additive manufacturing technology provides a new technical path for preparing the layered structure material due to the characteristics of strong near net forming capability, high design freedom, high cooling rate and the like. However, existing laser powder bed melt additive manufacturing techniques are typically used to produce single phase or dual phase materials of uniform composition, and it is difficult to achieve periodic layered distribution of microstructures within the same component. Although there have been studies attempting to regulate tissues by changing powder or adjusting scanning strategies, there are general problems of poor process stability, poor interlayer bonding, or insufficient tissue controllability. Disclosure of Invention Based on the background, the invention aims to provide a method for preparing a layered structure by a laser powder bed layer-by-layer remelting technology, which is capable of constructing a ferrite-austenite layered composite stainless steel material with a complex three-dimensional structure by combining global laser melting and local laser line remelting strategies and inducing differentiated solid phase transformation and grain growth behaviors in situ in the same powder layer. In order to achieve the above object, the present invention provides the following technical solutions: a method for preparing a layered structure by a laser powder bed layer-by-layer remelting technology, comprising the following steps: S1, laying a layer of metal powder on a substrate of laser selective melting equipment, and carrying out laser melting on the layer of metal powder to form a substrate layer; s2, carrying out laser wire remelting on a specific area on the substrate layer, wherein the area of the specific area is smaller than the area of the metal powder laser melting of the layer; s3, after remelting, paving a layer of metal powder on the substrate layer, and repeatedly executing the step S1 and the step S2 until printing is completed, so as to obtain the layered structure; The microstructure of the layered structure is characterized in that the microstructure of the region which is not remelted by the laser line is composed of ferrite with a BCC crystal structure and austenite with an FCC crystal structure, and crystal grains are equiaxed crystals, and the microstructure of the region which is remelted by the laser line is composed of ferrite with a single BCC crystal structure, and the crystal grains are columnar crystals. Preferably, the laser melting process conditions are that the scanning strategy is a checkerboard, the scanning power is 150-270W, the scanning speed is 800-1500 mm/s, the scanning interval is 0.1mm, the layer thickness is 30 μm, the rotation angle between layers is 67 degrees, and the diameter of the laser beam is 100 μm. By optimizing the process parameters of global melting, high density and uniform dual-phase structure of the matrix layer can be ensured. Preferably, the laser line remelting process comprises the steps of scanning parallel lines, scanning power of 100-350W, scanning speed of 800-2000 mm