Selective laser melting forming transverse multi-material scanning method based on laser bias

Abstract

The invention discloses a laser bias-based scanning method for selective laser melting forming of transverse multi-materials, which is used for optimizing a transverse interface of a selective laser melting forming multi-material structural member, and the multi-material structural member is provided with two different printing materials on two sides of the transverse interface. When the multi-material structural member is sliced and layered, the thicknesses of slices of the two different printing materials on the same printing layer are consistent; in the process of forming the same printing layer through selective laser melting, the printing material with the high laser energy density in the two different printing materials is firstly printed, then the printing material with the low laser energy density is printed, and when the printing material with the low laser energy density is printed, the laser scanning direction is from an interface formed by the two different printing materials to a boundary, and the laser scanning direction is from the boundary to the boundary. And an offset distance X is formed towards an interface formed by the two different printing materials. Therefore, the interface bonding effect of the laser forming part is improved by optimizing the laser offset distance, so that the mechanical property of the laser forming part is further improved.

Description

Technical Field

[0001] The invention relates to a lateral multi-material scanning method for selective laser melting forming based on laser bias, and belongs to the field of metal material additive manufacturing. Background Art

[0002] With the rapid development of the aerospace and military industries, aircraft and other weapon systems are facing increasingly harsh high-temperature working environments to achieve higher flight speeds. In order to maintain the performance, reliability and safety of the engine under such conditions, key components such as combustion chambers, turbine blades and nozzles must be made of materials that can withstand extreme high temperatures. Therefore, engineers often use a clever combination of multiple materials to manufacture these components in order to achieve the best service performance. Taking the engine combustion chamber as an example, its outer shell is usually made of nickel-based high-temperature alloy IN718, which is known for its excellent strength in high-temperature environments. For the interior of the combustion chamber, the high-thermal conductivity copper alloy CuSn10 can be used. This material has excellent thermal conductivity and helps to improve cooling efficiency. Through the combination of this material inside and outside, not only can the durability of the components in high-temperature environments be enhanced, but also its cooling efficiency under extreme conditions can be improved, so that the engine can operate at higher temperatures, thereby improving the thrust-to-weight ratio of the aircraft. This multi-material structure design not only demonstrates the innovative application of material science in modern industry, but also indicates its great potential in future high-temperature applications. Through careful material selection and design, we are able to provide more powerful and reliable power systems for aerospace vehicles, pushing flight technology higher, faster and farther.

[0003] Laser Powder Bed Fusion (LPBF) technology, also known as zone laser melting forming technology, is increasingly used in the aerospace field, especially in the manufacture of parts with complex structures. Compared with traditional arc additive manufacturing, laser directed energy deposition and laser welding technologies, LPBF technology can produce parts with higher forming accuracy and usually does not require a large number of post-processing steps. When designing multi-material structures, such as engine combustion chambers, it is bound to include the combination of heterogeneous materials in all directions, but they can be decomposed into up and down combination (longitudinal interface) + left and right combination (lateral interface).

[0004] A multi-material structure (taking material A + material B as an example) model is assembled from two CAD models of material A and material B. For the vertical interface, the two CAD models are connected up and down. Since the depth of the molten pool is usually greater than the thickness of the powder layer, the upper layer will naturally remelt the lower layer. When processing the top material B, the first few layers will remelt the bottom material A, thereby achieving metallurgical bonding between material A and material B. For the horizontal interface, the two CAD models are adjacent to each other on the left and right, and the periphery of the laser spot will scan the contour of each CAD model to ensure the accuracy of each part. Therefore, ideally, materials A and B will be closely adjacent.

[0005] However, due to some objective circumstances, such as:

[0006] 1. Under conventional Gaussian laser, the molten pool presents a size characteristic of being wide at the top and narrow at the bottom, so the molten pools of the two materials at the lateral interface will be closely connected at the top but difficult to connect at the bottom.

[0007] 2. Due to the phenomenon of thermal expansion and contraction, there may be no metallurgical bonding between the two materials at the lateral interface, and it is often almost impossible to achieve close proximity.

[0008] Therefore, a measure to improve the lateral interface bonding is urgently needed. In order to improve the lateral interface bonding, researchers have proposed a variety of measures. For example, by improving the powder feeding device of the equipment to achieve mutual overlap between powders, or by post-processing to eliminate the defects of the lateral interface. However, these methods often require a long cycle. At present, there is no report on the technology for preparing dense and defect-free CuSn10 / IN718 multi-material structures using different scanning strategies. Summary of the invention

[0009] The purpose of the present invention is to provide a lateral multi-material scanning method for selective laser melting based on laser bias, which preliminarily realizes the horizontal connection of multi-material structural parts (such as CuSn10 / IN718 multi-material structural parts) formed by selective laser melting by laser bias, and improves the interface bonding effect of laser-formed parts by optimizing the laser bias distance, so as to further improve the mechanical properties of laser-formed parts.

[0010] In order to achieve the above technical objectives, the present invention will adopt the following technical solutions:

[0011] A lateral multi-material scanning method for selective laser melting based on laser bias is used to optimize the lateral interface of a multi-material structural part formed by selective laser melting, wherein the multi-material structural part has two different printing materials on both sides of the lateral interface; for a multi-material structural part with a lateral interface, when slicing and layering, the slice layer thickness of the two different printing materials on the same printing layer is consistent;

[0012] In the process of selective laser melting to form the same printing layer, the printing material with higher laser energy density among the two different printing materials is printed first, and then the printing material with lower laser energy density is printed. When printing the printing material with lower laser energy density, the laser scanning direction is from the interface formed by the two different printing materials to the boundary, and has an offset distance X toward the interface formed by the two different printing materials.

[0013] Preferably, the two different printing materials are CuSn10 powder and IN718 powder respectively.

[0014] Preferably, in the process of selective laser melting to form the same print layer, CuSn10 powder is printed first, and then IN718 powder is printed, and when printing IN718 powder, the laser scanning direction has an offset distance X=25-125μm toward the CuSn10 / IN718 interface.

[0015] Preferably, the laser power for printing CuSn10 powder is 170 W, the scanning speed is 600 mm / s, and the scanning spacing is 0.07 mm; while the laser power for printing IN718 powder is 120 W, the scanning speed is 800 mm / s, and the scanning spacing is 0.075 mm.

[0016] Preferably, the slice layer thickness is 0.03 mm.

[0017] Preferably, during the selective laser melting process, the rotation angle between layers is 0 degree.

[0018] Another technical object of the present invention is to provide a lateral multi-material scanning method for selective laser melting based on laser bias, comprising the following steps:

[0019] Step 1: Establish three-dimensional solid models of the base and the workpiece respectively;

[0020] The workpiece is a multi-material structure having a transverse interface, wherein the multi-material structure has two different printing materials on both sides of the transverse interface;

[0021] Step 2: Plan the laser scanning strategy and printing process parameters for the base and workpiece respectively:

[0022] The three-dimensional solid models of the base and the workpiece are sliced ​​and layered respectively, and the obtained slice files are imported into the control system of the selective laser melting equipment; and when the three-dimensional solid model of the workpiece is sliced ​​and layered, the slice layer thickness of two different printing materials on the same printing layer is consistent;

[0023] Laser scanning strategy of the abutment: The abutment was formed using a chessboard scanning strategy, with 67 degrees of rotation between different layers;

[0024] Laser scanning strategy of workpiece: the workpiece is formed by adopting the overall scanning strategy, and the rotation angle between layers is 0 degrees; in addition, on the same printing layer, the printing material with higher laser energy density among the two different printing materials is printed first, and then the printing material with lower laser energy density is printed. In the process of printing the two different printing materials, the laser scanning direction is from the interface formed by the two different printing materials to the boundary. At the same time, when printing the printing material with lower laser energy density, the laser scanning direction has an offset distance X toward the interface formed by the two different printing materials.

[0025] Step 3: Printing the base:

[0026] The slicing file of the base obtained in step 2 is selected in the control system, and the base is printed layer by layer on the printing substrate according to the laser scanning strategy and printing process parameters of the base planned in step 2;

[0027] Step 4: Print the workpiece:

[0028] The slicing file of the workpiece obtained in step 2 is selected in the control system, and the workpiece is printed layer by layer on the base according to the laser scanning strategy and printing process parameters of the workpiece planned in step 2.

[0029] Preferably, in step 1, the two different printing materials of the multi-material structural component on both sides of the lateral interface are CuSn10 powder and IN718 powder;

[0030] The laser scanning strategy of the workpiece is as follows: in the process of selective laser melting to form the same print layer, the CuSn10 powder is printed first, and then the IN718 powder is printed. When printing the IN718 powder, the laser scanning direction is toward the CuSn10 / IN718 interface with an offset distance X=25–125μm.

[0031] Preferably, in step 2, the process parameters of the workpiece are: the laser power for printing CuSn10 powder is 170W, the scanning speed is 600mm / s, and the scanning spacing is 0.07mm; and the laser power for printing IN718 powder is 120W, the scanning speed is 800mm / s, and the scanning spacing is 0.075mm.

[0032] Another technical purpose of the present invention is to provide a multi-material structural part, which is printed and formed by the above-mentioned selective laser melting forming lateral multi-material scanning method based on laser bias.

[0033] Based on the above technical objectives, the present invention has the following advantages over the prior art:

[0034] The laser bias-based selective laser melting forming transverse multi-material scanning method described in the present invention takes into account the defects of existing multi-material structural parts (multi-material structural parts) at the transverse interface. On the one hand, when slicing and layering the multi-material structural parts, it ensures that the slice layer thickness of the two different printing materials on both sides of the transverse interface on the same printing layer is consistent; on the other hand, when printing and forming the same printing layer, it is required to first print the printing material with high laser energy density among the two different printing materials, and then print the printing material with low laser energy density. When printing the printing material with low laser energy density, the laser scanning direction is from the interface formed by the two different printing materials to the boundary, and has an offset distance X toward the interface formed by the two different printing materials. It can be seen that in this way, when printing and forming the same printing layer, the existence of the offset distance can ensure that when printing the printing material with low laser energy density, not only the printing material with low laser energy density is scanned, but also the printing material with high laser energy density is locally remelted, and the remelting width is the offset distance, thereby improving the bonding effect of the transverse interface, and then optimizing the microstructure and mechanical properties of the interface junction. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a comparative schematic diagram of the selective laser melting forming of transverse multi-materials with and without laser bias according to the present invention;

[0036] Figure 2 It is a CuSn10 / IN718 multi-material specimen prepared based on different laser bias distances;

[0037] Figure 3 It is based on the interface bonding of CuSn10 / IN718 multi-material samples prepared at different laser bias distances;

[0038] Figure 4 The metallurgical bonding at the interface of CuSn10 / IN718 multi-material sample prepared by laser bias 75μm

[0039] Figure 5 It is the hardness distribution at the interface of CuSn10 / IN718 multi-material sample prepared by laser bias 75μm. In the figure: (a) is the hardness distribution cloud diagram at the interface of CuSn10 / IN718 multi-material sample; (b) is the X-direction distance-average hardness line diagram of the hardness at the interface of CuSn10 / IN718 multi-material sample. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means any limitation to the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise specified, the relative arrangement, expressions and numerical values ​​of the components and steps described in these embodiments do not limit the scope of the present invention. The techniques, methods and equipment known to ordinary technicians in the relevant fields may not be discussed in detail, but in appropriate cases, the techniques, methods and equipment should be regarded as part of the specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiments may have different values.

[0041] like Figure 1 As shown, the laser bias-based selective laser melting lateral multi-material scanning method of the present invention is used to optimize the lateral interface of the selective laser melting multi-material structural member, and the multi-material structural member has two different printing materials on both sides of the lateral interface; for the multi-material structural member with a lateral interface, when slicing and layering, the slice layer thickness of the two different printing materials on the same printing layer is consistent; in the process of selective laser melting forming the same printing layer, the printing material with a higher laser energy density among the two different printing materials is printed first, and then the printing material with a lower laser energy density is printed, and in the process of printing the two different printing materials, the laser scanning direction is from the interface formed by the two different printing materials to the boundary, and at the same time, when printing the printing material with a low laser energy density, the laser scanning direction has an offset distance X toward the interface formed by the two different printing materials.

[0042] Specifically, the lateral multi-material scanning method for selective laser melting forming based on laser bias of the present invention comprises the following steps:

[0043] Step 1: Establish three-dimensional solid models of the base and the workpiece respectively;

[0044] The workpiece targeted by the present invention is a multi-material structural member with a transverse interface, and the multi-material structural member has two different printing materials on both sides of the transverse interface. In other words, the workpiece selected by the present invention has a structural member made of material A on one side in the horizontal direction, which is recorded as the material A structural member, and a structural member made of material B on the other side, which is recorded as the material B structural member.

[0045] The base is made of a printing material with a low laser energy density among two different printing materials.

[0046] Step 2: Plan the laser scanning strategy and printing process parameters for the base and workpiece respectively:

[0047] The slicing software is used to slice and layer the three-dimensional solid models of the base and the workpiece, and the obtained slice files are imported into the control system of the selective laser melting equipment; and when the three-dimensional solid model of the workpiece is sliced ​​and layered, the slice layer thickness of two different printing materials on the same printing layer is consistent; in addition, it should be specially pointed out that when the three-dimensional solid model of the workpiece is sliced ​​and layered, the slice files of the A material structure part and the B material structure part can be obtained respectively;

[0048] Laser scanning strategy of the abutment: The abutment was formed using a chessboard scanning strategy, with 67 degrees of rotation between different layers;

[0049] Printing process parameters of the workpiece: among two different printing materials, the laser energy density of one printing material is higher than that of the other printing material; for the sake of convenience, it is assumed that the laser energy density of the above-mentioned material A is higher than that of the material B; the A material structure is located on the left side of the multi-material structure, and the B material structure is located on the right side of the multi-material structure.

[0050] Laser scanning strategy of the workpiece: The workpiece is formed by an overall scanning strategy, and the rotation angle between layers is 0 degrees. The reason for the 0-degree rotation between layers is that during the melting process of the powder, due to the uneven heat transfer, the melting depth and width of the tip area of ​​the part are significantly different from those of the internal area. By choosing the interface and the melt path to be always parallel, the appearance of the melt path tip at the interface can be avoided as much as possible, further ensuring the optimization of the interface bonding by the laser bias; in addition, on the same printing layer, the printing material with a higher laser energy density among the two different printing materials is printed first, and then the printing material with a lower laser energy density is printed. When printing the printing material with a lower laser energy density, the laser scanning direction is from the interface formed by the two different printing materials to the boundary, and there is an offset distance X towards the interface formed by the two different printing materials; the laser scanning direction is from the interface formed by the two different printing materials to the boundary, which can ensure that a relatively accurate offset distance can be obtained at the lateral interface.

[0051] Step 3: Printing the base:

[0052] The slicing file of the base obtained in step 2 is selected in the control system, and the base is printed layer by layer on the printing substrate according to the laser scanning strategy and printing process parameters of the base planned in step 2;

[0053] Specifically, the printing of the base includes the following steps:

[0054] Step 3.1. Select the slice file of the base obtained in step 2 in the control system, prepare for printing, and fill with nitrogen to reduce the oxygen content to below 0.1% to protect the printing environment.

[0055] Step 3.2, clean the molding chamber of the equipment, fix and level the substrate, adjust the distance between the substrate and the scraper to the preset value, start the laser additive manufacturing equipment, and print the forming base layer by layer on the printing substrate according to the laser scanning strategy and printing process parameters of the base planned in step 2.

[0056] Step 4: Print the workpiece:

[0057] The slicing file of the workpiece obtained in step 2 is selected in the control system, and the workpiece is printed layer by layer on the base according to the laser scanning strategy and printing process parameters of the workpiece planned in step 2.

[0058] Specifically, the printing of the workpiece includes the following steps:

[0059] Step 4.1, selecting the workpiece slicing file, the workpiece laser scanning strategy and the printing process parameters obtained in step 2 in the control system;

[0060] Step 4.2, adjust the forming cylinder to drop a certain distance (this distance is the slice thickness), fill the left half of the multi-material structure with material A and use a scraper to flatten it. Perform laser scanning of material A in the current printing layer according to the model size of the material A structure to ensure that the size of the formed part is consistent with the model of the material A structure;

[0061] Step 4.3: After the printing of material A in the current printing layer is completed, the unmelted material A powder is cleaned up, and the right half of the multi-material structure is filled with material B, and the laser scanning path of material B in the printing layer is followed. It should be noted in this step that the laser scanning path of material B is not strictly in accordance with the CAD model size of the material B structure, but is offset by a distance of Xμm to the material A structure at the interface, that is, ideally, the size of the material B molded part will be expanded by Xμm toward the interface side.

[0062] Step 4.4: Repeat steps 4.2-4.3, with the rotation angle between layers being 0 degrees, until the workpiece is printed.

[0063] The technical solution of the present invention will be described in detail below in conjunction with various embodiments.

[0064] Example 1

[0065] This embodiment is a specific application example of the lateral multi-material scanning method for selective laser melting forming based on laser bias according to the present invention, and specifically includes the following steps:

[0066] Step 1: Create three-dimensional solid models of the base and workpiece respectively:

[0067] In this embodiment, the workpiece is a multi-material structural part formed by assembling the right half IN718 part and the left half CuSn10 part; the interface formed by the IN718 part and the CuSn10 part is recorded as the CuSn10 / IN718 interface;

[0068] The abutment is a structural component made of IN718 material, denoted as IN718 abutment;

[0069] Step 2: Plan the laser scanning strategy and printing process parameters for the base and workpiece respectively:

[0070] Plan the laser scanning strategies and printing process parameters for IN718 and CuSn10 respectively, slice and layer the 3D solid model. Both need to have the same slice layer thickness, and import the slice file into the equipment control system.

[0071] The specific contents of the laser scanning strategy include: for the IN718 base, a chessboard scanning strategy is used to form the base, with a 67-degree rotation between different layers; for multi-material structural parts, on the same printing layer, the CuSn10 structural parts with high laser energy density are printed first, and then the IN718 structural parts with low laser energy density are printed. The laser scanning direction of the two materials is from the CuSn10 / IN718 interface to the boundary, ensuring that a relatively accurate offset distance can be obtained at the interface. The optional value of the offset distance is 75μm.

[0072] The process parameters of the workpiece are: the laser power for printing CuSn10 powder is 170W, the scanning speed is 600mm / s, and the scanning spacing is 0.07mm; while the laser power for printing IN718 powder is 120W, the scanning speed is 800mm / s, and the scanning spacing is 0.075mm.

[0073] like Figure 1 As shown, the yellow part represents the CAD model size corresponding to the CuSn10 part, and the red arrow represents the laser scanning path and scanning direction of the laser melting formed CuSn10 part (high laser energy density); the blue part represents the CAD model size of the IN718 part (low laser energy density), and the black arrow represents the laser scanning path and scanning direction of the laser melting formed IN718 part. The 1st, 2nd, ... (N+n)th lanes represent the scanning order of each laser of the two materials.

[0074] The red circle indicates the laser spot, indicating the size of the laser action area. In the comparative example (laser offset distance 0 μm), the positions of the laser spots are adjacent and have no overlap. In the embodiment (laser offset distance X), the laser spot close to the interface in the blue area has an offset distance X toward the yellow area, so that the first laser spot of the IN718 part formed by laser melting will overlap with the first laser spot of the CuSn10 part formed by laser melting, and the lateral width of the overlap is the offset distance X.

[0075] Step 3: Printing the base:

[0076] Select the imported IN718 base slice file in the control system, prepare for printing, and fill with nitrogen to reduce the oxygen content to below 0.1% to protect the printing environment.

[0077] Clean the molding chamber of the equipment, fix and level the substrate, adjust the distance between the substrate and the scraper to 0.03mm, start the laser additive manufacturing equipment, and form the IN718 base.

[0078] Step 4: Print the workpiece:

[0079] The printing process of the workpiece includes the following steps:

[0080] Step 4.1, select the imported workpiece slice file, the workpiece laser scanning strategy and the printing process parameters in the control system;

[0081] Step 4.2, adjust the forming cylinder to drop 0.03mm, fill the left half of the multi-material component with CuSn10 powder and use a scraper to smooth it. Perform a laser scan of CuSn10 according to the CAD model size to ensure that the size of the formed part is consistent with the model.

[0082] Step 4.3: After completing the printing of CuSn10 in the current printing layer, clean up the unmelted CuSn10 powder, refill the right half of the multi-material component with IN718 powder, and scan it according to the laser scanning path of the IN718 printing layer.

[0083] Among them, the laser scanning path of IN718 is not strictly in accordance with the CAD model size, but is offset by 75 μm toward CuSn10 at the CuSn10 / IN718 interface, that is, in ideal conditions, the size of the formed part will be expanded by 25 μm on the interface side.

[0084] Step 4.4: Repeat steps 4.2-4.3 until the entire model is printed.

[0085] In addition, it should be noted that the reason for the 0-degree interlayer rotation is that the melting depth and width of the tip area of ​​the part are significantly different from those of the internal area due to the uneven heat transfer during the melting process of the powder. In order to better study the influence of laser bias on interface bonding at the CuSn10 / IN718 interface, the appearance of the melt path tip at the interface is avoided, and the interface and the melt path are always parallel.

[0086] Wait for the substrate temperature to drop to room temperature, open the door, clean the powder, take out the substrate from the forming chamber, and use wire cutting to remove the sample. The obtained sample is shown in the attached Figure 2 The bonding condition of the sample at the interface is shown in the attached Figure 3 .

[0087] Example 2

[0088] The difference between this embodiment and embodiment 1 is that the optional value of the offset distance is 75 μm. The obtained sample is shown in the attached Figure 2 Sample No. 3 or No. 5, Figure 2 The enlarged image of sample 5 is also shown. In the enlarged image, three sets of repeated samples 5-1, 5-2, and 5-3 of laser bias 75μm workpieces on the same IN718 base are also shown. The bonding conditions of the samples at the interface are shown in the attached Figure 3 The metallurgical bonding of the sample at the interface is detailed in the attached Figure 4 The hardness distribution of the sample at the interface is shown in the attached Figure 5 .

[0089] Depend on Figure 4 It can be seen that the CuSn10 peninsula and the IN718 peninsula form a mutually interlocking microstructure in the interface area. This interlocking structure increases the interface contact area, helps the two materials (CuSn10 powder + IN718 powder) to achieve mechanical locking on a micro scale, and enhances the strength of the interface bonding. In addition, it can be seen that there is element diffusion at the interface before the peninsula. This diffusion forms a metallurgical bond on the interface, improves the stability of the bond, and enables the interface to withstand higher mechanical loads and thermal stresses. This is the reason why the interface structure of the sample obtained under the laser bias of 75μm is good.

[0090] Figure 5 The hardness distribution of CuSn10 powder and IN718 powder near the interface when the laser bias is 75μm (160 points) is shown; the X-direction distance-average hardness line graph shows the average value of 8 different Y-value points corresponding to the same X value in the distribution cloud graph. The hardness value in the laser bias area fluctuates widely, which is due to the presence of Figure 4The peninsula is shown. The overall smooth transition from the CuSn10 region to the IN718 region verifies that the metallurgical bonding effect brought by the laser bias makes the interface well bonded. The increase in hardness near the interface may be due to the interface strengthening effect caused by the combination of the two materials. This strengthening may be caused by lattice distortion, grain refinement, precipitation of the second phase, or enhanced interatomic bonding force at the interface.

[0091] Example 3

[0092] The difference between this embodiment and embodiment 1 is that the optional value of the offset distance is 125 μm. The obtained sample is shown in the attached Figure 2 The bonding condition of the sample at the interface is shown in the attached Figure 3 .

[0093] Comparative Example

[0094] The difference between this comparative example and Example 1 is that the offset distance is 0 when the workpiece is printed. Figure 2 For the bonding condition of the samples at the interface, see the attached Figure 3 .

[0095] from Figure 3 It can be seen that CuSn10 and IN718 are located on both sides, and both materials show high density, indicating that their printing parameters are within the optimal processing window.

[0096] When the laser bias is 0 μm, CuSn10 and IN718 do not form metallurgical bonding, there are continuous grooves in the adjacent areas, and unmelted powder is adhered inside the grooves. Under the action of their respective surface tensions, the edges of the upper surfaces are in an arc shape and shrink to their respective sides.

[0097] When the laser bias is 25μm, there is a partial metallurgical bond between CuSn10 and IN718, the two materials are partially adhered, the gullies become discontinuous, and there is still unmelted powder at the discontinuity. Microcrack propagation is also observed on the IN718 side. Due to the weak wetting effect between the two materials, the arc of the upper surface edge is smoother than that of the laser bias of 0μm.

[0098] When the laser offset is 75μm, CuSn10 and IN718 achieve metallurgical bonding. In the offset area, the two materials are stirred and interlocked due to Marangoni convection, which increases the interface bonding strength. This offset distance promotes good wetting of the materials and a smooth transition on the upper surface. However, due to the rapid solidification characteristics of the selective laser melting process and the large difference in thermal expansion coefficients between the two, some microcracks are generated on the IN718 side.

[0099] When the laser bias is 125μm, although there is still metallurgical bonding between CuSn10 and IN718, the number of cracks increases significantly, the interface area lacks obvious bite, the surface is rugged, and the wettability is poor. The large bias distance causes a significant temperature gradient, resulting in large thermal stress, and the accumulation of residual stress exacerbates the formation of cracks.

[0100] In summary, an appropriate laser offset distance is beneficial to interface bonding. If the offset distance is too small, the two will have insufficient wetting and difficult metallurgical bonding. If the offset distance is too large, the temperature gradient and residual stress will increase, thereby aggravating the generation of cracks.

[0101] It should be pointed out that the printing process parameters of the workpiece need to be determined according to the performance of the two different printing materials themselves. The printing process parameters of the two different printing materials can be the corresponding optimal printing parameters. Of course, the specific acquisition of these parameters may be affected by objective test conditions and there may be some changes. The main invention of the present invention is that for the same printing layer, the configuration of the offset distance affects the metallurgical bonding of the lateral interface.

[0102] It should also be pointed out that the above-mentioned embodiments 1-3 are only specific implementations of the effect of the offset distance on the metallurgical bonding of the CuSn10 / IN718 interface. In fact, due to the configuration of the offset distance in the process of 3D printing formed parts of the present invention, not only the printing material with low laser energy density printed later is melted, but also the printing material with high laser energy density printed earlier is locally remelted at the interface position. Therefore, it can be determined that the offset distance must have a beneficial effect on the metallurgical bonding of the lateral interface. However, for lateral interfaces formed by different materials, the specific value of the offset distance needs to be obtained through corresponding experiments. Therefore, the above-mentioned embodiments should not limit the technical solutions described in the present invention.

Claims

1. A lateral multi-material scanning method for selective laser melting based on laser bias, used to optimize the lateral interface of a multi-material structural part formed by selective laser melting, wherein the multi-material structural part has two different printed materials on both sides of the lateral interface; characterized in that: For multi-material structures with lateral interfaces, when slicing and layering, the slice thickness of two different printed materials on the same print layer is consistent; In the process of selective laser melting to form the same printing layer, the printing material with higher laser energy density among the two different printing materials is printed first, and then the printing material with lower laser energy density is printed. In the process of printing the two different printing materials, the laser scanning direction is from the interface formed by the two different printing materials to the boundary. At the same time, when printing the printing material with lower laser energy density, the laser scanning direction has an offset distance X toward the interface formed by the two different printing materials.

2. The method for lateral multi-material scanning by selective laser melting based on laser bias according to claim 1, characterized in that: The two different printing materials are CuSn10 powder and IN718 powder.

3. The method for lateral multi-material scanning by selective laser melting based on laser bias according to claim 2, characterized in that: In the process of selective laser melting to form the same printing layer, CuSn10 powder is printed first, and then IN718 powder is printed. When printing IN718 powder, the laser scanning direction has an offset distance X=25-125μm toward the CuSn10 / IN718 interface.

4. The method for lateral multi-material scanning by selective laser melting based on laser bias according to claim 3 is characterized in that: The laser power for printing CuSn10 powder is 170W, the scanning speed is 600mm / s, and the scanning spacing is 0.07mm; while the laser power for printing IN718 powder is 120W, the scanning speed is 800mm / s, and the scanning spacing is 0.075mm.

5. The method for lateral multi-material scanning by selective laser melting based on laser bias according to claim 4, characterized in that: The slice layer thickness is 0.03 mm.

6. The method for lateral multi-material scanning by selective laser melting based on laser bias according to claim 4, characterized in that: During the selective laser melting process, the rotation angle between layers is 0 degrees.

7. A method for scanning multiple materials in a lateral direction by selective laser melting based on laser bias, characterized in that: The steps include: Step 1: Establish three-dimensional solid models of the base and the workpiece respectively; The workpiece is a multi-material structure having a transverse interface, wherein the multi-material structure has two different printing materials on both sides of the transverse interface; Step 2: Plan the laser scanning strategy and printing process parameters for the base and workpiece respectively: The three-dimensional solid models of the base and the workpiece are sliced ​​and layered respectively, and the obtained slice files are imported into the control system of the selective laser melting equipment; and when the three-dimensional solid model of the workpiece is sliced ​​and layered, the slice layer thickness of two different printing materials on the same printing layer is consistent; Laser scanning strategy of the abutment: The abutment was formed using a chessboard scanning strategy, with 67 degrees of rotation between different layers; Laser scanning strategy of workpiece: the workpiece is formed by adopting the overall scanning strategy, and the rotation angle between layers is 0 degrees; in addition, on the same printing layer, the printing material with higher laser energy density among the two different printing materials is printed first, and then the printing material with lower laser energy density is printed. In the process of printing the two different printing materials, the laser scanning direction is from the interface formed by the two different printing materials to the boundary. At the same time, when printing the printing material with lower laser energy density, the laser scanning direction has an offset distance X toward the interface formed by the two different printing materials. Step 3: Printing the base: The slicing file of the base obtained in step 2 is selected in the control system, and the base is printed layer by layer on the printing substrate according to the laser scanning strategy and printing process parameters of the base planned in step 2; Step 4: Print the workpiece: The slicing file of the workpiece obtained in step 2 is selected in the control system, and the workpiece is printed layer by layer on the base according to the laser scanning strategy and printing process parameters of the workpiece planned in step 2.

8. The method for lateral multi-material scanning by selective laser melting based on laser bias according to claim 7, characterized in that: In step 1, the two different printing materials of the multi-material structural component on both sides of the lateral interface are CuSn10 powder and IN718 powder; The laser scanning strategy of the workpiece is as follows: in the process of selective laser melting to form the same print layer, the CuSn10 powder is printed first, and then the IN718 powder is printed. When printing the IN718 powder, the laser scanning direction is toward the CuSn10 / IN718 interface with an offset distance X=25–125μm.

9. The method for lateral multi-material scanning by selective laser melting based on laser bias according to claim 8, characterized in that: In step 2, the process parameters of the workpiece are: the laser power for printing CuSn10 powder is 170 W, the scanning speed is 600 mm / s, and the scanning spacing is 0.07 mm; while the laser power for printing IN718 powder is 120 W, the scanning speed is 800 mm / s, and the scanning spacing is 0.075 mm.

10. A multi-material structural component, characterized in that: Printing and forming is carried out by the lateral multi-material scanning method of selective laser melting forming based on laser bias as described in any one of claims 1 to 9.

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